K. Ranjan

Silicon sensors in next generation hadron colliders will face a tremendously harsh radiation environment. Requirement to study rarest reaction channels with statistical constraints has resulted in a huge increment in radiation flux, resulting in both surface damage and bulk damage. For sensors which are used in a charged hadron environment, both of these degrading processes take place simultaneously. Recently it has been observed in proton irradiated n+-p Si strip sensors that n+ strips had a good inter-strip insulation with low values of p-spray and p-stop doping densities which is contrary to the expected behaviour from the current understanding of radiation damage. In this work a simulation model has been devised incorporating radiation damage to understand and provide a possible explanation to the observed behaviour of irradiated sensors.

Summary The paper outlines a comprehensive workflow for calibrating well models and optimizing well production. An automated well-model management system ensures data accuracy and timeliness by fetching information from the production database. Simultaneously, the well-production optimization process identifies opportunities for improving field development and production operations by analyzing real-time data and applying optimization techniques. The system empowers engineers with data-driven decision-making tools and provides recommendations for optimizing well parameters. The integration of multiple data sources, automated processes, and data quality control ensures the reliability of results. This automated approach enhances the identification of valid optimization opportunities and facilitates well performance management, leading to significant oil production gains and informed decision-making within the field.

In the present work, detailed simulation using Technology Computer Aided Design (TCAD) tool, Silvaco for non-irradiated and irradiated LGAD (Low Gain Avalanche Detector) devices has been carried out. The effects of different design parameters and proton irradiation on LGAD operation are discussed in detail. An already published effective two trap bulk damage model is used to simulate the radiation damage without implementing any acceptor removal term. The TCAD simulation for irradiated LGAD devices produce decreasing gain with increasing fluence, similar to the measurement results. The space charge density and electric field distribution are used to illustrate the possible reasons for the degradation of gain of the irradiated LGAD devices.

In this paper, a computer-based analysis is performed to study layout solutions aimed at increasing the breakdown voltage in Si-microstrip detectors. For optimum performance it is crucial to achieve maximum breakdown voltage for Si detectors operating at very high bias due to the extremely hostile radiation environment of next generation experiments such as LHC. The performance of Si-microstrip detectors can be improved by implementing floating field-limiting rings around the active detector area. A simulation study has been carried out to evaluate the distribution of breakdown voltage as a function of guard-ring spacing (GS). The purpose of this work is to find a criterion to optimize GS for multiple ring structures incorporating various physical and geometrical parameters as an aid to design optimization. Using this criterion the optimum spacing of guard rings for multiple ring structures was obtained. The proposed criterion is very robust and is insensitive to the number of guard rings, junction depth and radiation damage. The simulation results for the seven-ring design agree well with experimental measurements.

The harsh radiation environment in future high energy physics experiments like large hadron collider provides a challenging task to the performance of Si microstrip detectors. The performance of Si microstrip detectors is scaled in terms of the breakdown performance of the device while having no adverse effect on signal/noise ratio (S/N). The adoption of overhanging metal electrode is known to limit the breakdown risks in high voltage biased microstrip detectors. The present study aims at investigating the effect of width of overhanging metal electrode on the interstrip capacitance, and hence on noise performance of silicon microstrip detectors to be used in the Preshower detector of the electromagnetic calorimeter at compact muon solenoid. The influence of various geometrical and physical parameters like strip-width/pitch ratio of the strips, surface state fixed oxide charge and relative permittivity of the passivant on the interstrip capacitance of Si detectors is also discussed. The adoption of limited overhanging metal electrode is shown to have positive impact on interstrip capacitance while improving the breakdown performance of the device also.

Background: Neuroimaging is an important tool in early detection of Alzheimer’s disease (AD), which is a serious neurodegenerative brain disease among the elderly subjects. Independent component analysis (ICA) is arguably one of the most widely used algorithm for the analysis of brain imaging data, which can be used to extract intrinsic networks of brain from functional magnetic resonance imaging (fMRI). Method: Witnessed by recent studies, a more flexible model known as restricted Boltzmann machine (RBM) can also be used to extract spatial maps and time courses of intrinsic networks from resting state fMRI, moreover, RBM shows superior temporal features than ICA. Here, we seek to employ RBM to improve the performance of classifying individuals. Experiments are performed on healthy controls and subjects at the early stage of AD, i.e., cognitive normal (CN) and early mild cognitive impairment participants (EMCI), and two types of data, i.e., structural magnetic resonance imaging (sMRI) and fMRI data. Results: (1) By separately employing ICA for sMRI and fMRI, the features extracted from fMRI improve classification accuracy by 7.5% for CN and EMCI; (2) instead of applying ICA to fMRI, using RBM further improves classification accuracy by 7.75% for CN and EMCI; (3) the lesions at the early stage of AD are more likely to occur in the regions around slices 4, 6, 10, 14, 19, 51 and 59 of the whole brain in the longitudinal direction. Conclusion: By using fMRI instead of sMRI and RBM instead of ICA, we can classify CN and EMCI more efficiently.

During the scheduled high luminosity upgrade of LHC, the world's largest particle physics accelerator at CERN, the position sensitive silicon detectors installed in the vertex and tracking part of the CMS experiment will face more intense radiation environment than the present system was designed for. To upgrade the tracker to required performance level, extensive measurements and simulations studies have already been carried out. A defect model of Synopsys Sentaurus TCAD simulation package for the bulk properties of proton irradiated devices has been producing simulations closely matching with measurements of silicon strip detectors. However, the model does not provide expected behavior due to the fluence increased surface damage. The solution requires an approach that does not affect the accurate bulk properties produced by the proton model, but only adds to it the required radiation induced properties close to the surface. These include the observed position dependency of the strip detector's charge collection efficiency (CCE). In this paper a procedure to find a defect model that reproduces the correct CCE loss, along with other surface properties of a strip detector up to a fluence $1.5\times10^{15}$ 1 MeV n$_{\textrm{eq}}$ cm$^{-2}$, will be presented. When applied with CCE loss measurements at different fluences, this method may provide means for the parametrization of the accumulation of oxide charge at the SiO2/Si interface as a function of dose.

Previous detailed studies of direct photon production from both fixed-target and collider experiments have witnessed a pattern of deviation between the measured inclusive cross sections and the corresponding theoretical expectations in the low transverse momentum ${(p}_{T})$ regime. Most data sets display steeper ${p}_{T}$ dependence than the next-to-leading-order (NLO) perturbative QCD (PQCD) calculations with standard choices of scales and parton distribution functions in this region. A simple implementation of higher-order soft-gluon corrections to the NLO PQCD predictions significantly improves the agreement between data and theory. This interesting feature motivated us to investigate the D\O{} and CDF measurements of inclusive photon cross section at $\sqrt{s}=1.8\mathrm{TeV}$ from the run $1b$ and also at $\sqrt{s}=630\mathrm{GeV}.$ We use the latest updated parton distribution function CTEQ6M in the NLO QCD calculations for direct photon cross section to describe the data. The conventional theoretical uncertainties originating from scale dependence and gluon distributions have been illustrated. We estimate the impact of additional soft-gluon radiation on the direct photon production using PYTHIA (LO PQCD), which adds transverse momentum ${k}_{T}$ to initial-state partons through a Gaussian smearing. The impact of ${k}_{T}$ effects on the discrepancy in the low-${p}_{T}$ region is explored using a phenomenological model, wherein we merge the NLO calculations with ${k}_{T}$ correction factors. We show that this approach provides a much more acceptable description of the Fermilab Tevatron data.

In an effort to compare beam dynamics and create a "benchmark" for Dispersion Free Steering (DFS) a comparison was made between different International Linear Collider (ILC) simulation programs while performing DFS. This study consisted of three parts. Firstly, a simple betatron oscillation was tracked through each code. Secondly, a set of component misalignments and corrector settings generated from one program was read into the others to confirm similar emittance dilution. Thirdly, given the same set of component misalignments, DFS was performed independently in each program and the resulting emittance dilution was compared. Performance was found to agree exceptionally well in all three studies.

Si sensors in future high-energy physics experiments will encounter an extremely harsh radiation environment. In lepton colliders, the dominant background from electron–positron pairs can be managed with modern Si technology, but there is also a potentially dangerous neutron background. Specifically, the estimated neutron background is around 1–1.6 × 1010 1-MeV equivalent neutrons cm−2 year−1 for the Si microstrip sensors to be used in the innermost vertex detectors of the International Linear Collider (ILC). This causes bulk damage in the Si sensors due to the non-ionization energy loss and is of much greater importance in determining the viability of their long-term operation. For reliable operation, such sensors will need to operate at high reverse biases, far beyond the full depletion voltages, which can lead to the sensor breakdown. Multi-guard ring structures have evolved as a powerful technique to improve the breakdown performance of these sensors. In this work, a comprehensive approach towards the understanding of multi-guard ring structures is followed by simulating several structures with different layouts. The potential and field distributions help in optimizing design parameters.

Silicon Detector (SiD) is one of the proposed detectors for the future International Linear Collider (ILC). In the innermost vertex of the ILC, Si micro-strip sensors will be exposed to the neutron background of around 1–1.6×1010 1 MeV equivalent neutrons cm−2 year−1. The p+n−n+ double-sided Si strip sensors are supposed to be used as position sensitive sensors for SiD. The shortening due to electron accumulation on the n+n− side of these sensors leads to uniform spreading of signal over all the n+ strips and thus ensuring good isolation between the n+ strips becomes one of the major issues in these sensors. One of the possible solutions is the use of floating p-type implants introduced between the n+ strips (p-stops) and another alternative is the use of uniform layer of p-type implant on the entire n-side (p-spray). However, pre-breakdown micro-discharge is reported because of the high electric field at the edge of the p-stop/p-spray. An optimization of the implant dose profile of the p-stop and p-spray is required to achieve good electrical isolation while ensuring satisfactory breakdown performance of the Si sensors. Preliminary results of the simulation study performed on the n+n− Si sensors having p-stop and p-spray using device simulation program, ATLAS, are presented.

Abstract A simple model has been proposed to calculate the cohesive energy and other related bulk properties of alkali-doped C60 solids. In our earlier work we have successfully explained the bulk properties of K-, Rb- and Cs-doped C60 solids. The system is treated as an ionic solid, where van der Waals interactions have also been taken into account. The nature of interactions does not change when doped with sodium or other alkali atoms. The present work specifically deals with bulk properties of sodium and mixed alkali-doped M3C60 solids and in general alkali-doped C60 solids. Highly doped sodium systems are of extreme importance due to clustering of sodium atoms at octahedral sites. Our results for lattice constant are in good agreement with other experiments and calculations. Our method also allows us to estimate the distribution of excess charge among the clusters. We find that the Na atoms at tetrahedral sites are fully ionized, i.e. exist as Na+ while those at octahedral sites, which exist as clusters whenever n > 3 in NanC60, are partially ionized such that the total charge on C60 molecule is six-electron units.

We report cohesive energy calculations for alkali metal doped C60 solids. Model calculations are presented for K1C60, K2C60, K3C60, K4C60 and K6C60. In this work, the C60 molecule is modelled as a uniform spherical shell with appropriate surface density of carbon atoms, while the ionised alkali atoms, forming the cations are taken to be point charges. Part of the electrons freed by those ionised K atoms are distributed on the C60 molecule making it an anion, while the rest (say x) are assumed to form a delocalised electron gas. This electron gas screens the Coulomb interaction between the various anion and cations. We also account for on-shell Coulomb repulsion between the electrons on the C60 shell. With these assumptions the total cohesive energy is calculated taking into consideration van der Waals and screened Coulomb interaction between different ions. On minimising the energy thus calculated with respect to x, the fraction of electrons forming electron gas, we find that x is zero i.e. total charge transfer from cation to anion is favoured. Thus ionic character of K doped C60 solids is established on the basis of the model. Comparison of the total energy thus obtained has been made with other calculations. We also show the phase instability of K2C60 system.

The performance of metal-overhang (MO) equipped silicon micro-strip sensors, after irradiation for the preshower detector to be used in compact muon solenoid (CMS)experiment at the large hadron collider (LHC), CERN, has been studied through simulations. Detailed calculations using Hamburg model have allowed the parameterization of these effects and helped to simulate the operation scenario of MO equipped sensors over ten years of LHC operation. The utility of overhanging metal extension as junction termination technique after space charge sign inversion (SCSI) has been explored in detail for the first time in this work. Several interesting results like a shift in the optimal oxide thickness in MO equipped structures after irradiation have been reported. The comparison of dielectric and semi-insulator passivated MO equipped structures after irradiation has been studied. Also, the impact of various crucial geometrical parameters like device depth (W/sub N/), width of back N/sup +/ layer used for ohmic contact (W/sub N//sup +/), strip width (W), strip pitch (P) and width of overhang extension (W/sub MO/) on the MO equipped structure after SCSI has been presented in detail.

In an effort to compare beam dynamics and create a ''benchmark'' for Dispersion Free Steering (DFS) a comparison was made between different ILC simulation programs while performing DFS. This study consisted of three parts. First, a simple betatron oscillation was tracked through each code. Secondly, a set of component misalignments and corrector settings generated from one program was read into the others to confirm similar emittance dilution. Thirdly, given the same set of component misalignments DFS was performed independently in each program and the resulting emittance dilution was compared. Performance was found to agree exceptionally well in all three studies.

Study of direct photon production in high-energy hadronic collisions provides a clean tool for testing the essential validity of perturbative quantum chromodynamics (PQCD) predictions as well as for constraining the gluon distribution of nucleons. These attractive considerations prompted us to study the characteristics of direct photons at CERN LHC energy $(\sqrt{s}=14\mathrm{TeV}).$ In order to validate our simulation results, we first describe the direct photon data at $\sqrt{s}=1.8\mathrm{TeV}$ in the central pseudorapidity $(\ensuremath{\eta})$ region. We used next-to-leading-order (NLO) QCD calculations and leading-order (LO) PYTHIA estimates with the latest parton distribution function, CTEQ5M1. At $\sqrt{s}=14\mathrm{TeV},$ the LO and NLO QCD predictions for direct photon cross section are presented as a function of transverse momentum of photon ${(p}_{T})$ in the kinematical region $20\mathrm{GeV}<{p}_{T}<400\mathrm{GeV}$ and $|\ensuremath{\eta}|<3.$ The sensitivity of the theoretical predictions to the choice of renormalization scales and gluon distributions is also demonstrated. The pseudorapidity $(\ensuremath{\eta})$ and cone size dependence of the direct photon cross section is also discussed.

Giant Cell Tumour of Tendon Sheath (GCTTS) is a slow growing benign soft tissue tumour arising from synovium of tendon sheath or joint. These tumours occur more frequently in upper limbs, especially hands. In the present study, we aimed to evaluate the cytomorphological spectrum of GCTTS.This retrospective study includes a total of 56 cases of GCTTS diagnosed over a period of 8 years. The clinical and radiological details of these cases were retrieved from the cytopathology records and detailed cytomorphological features were studied and analysed. Histopathological correlation was done in 16/56 cases, where follow-up was available.The mean age of patients at the time of presentation was 32 years and were predominantly females (68%). The most common site of GCTTS was fingers (76%), followed by foot, wrist and toes. The most consistent finding on cytology was stromal cells (100%) of polygonal, spindle and plasmacytoid morphology with interspersed multinucleated osteoclastic giant cells (100%), followed by binucleated stromal cells (75%), xanthoma cells (61%) and hemosiderin laden macrophages (52%). Presence of proteinaceous fluid background was also observed in 50% of the cases.GCTTS can be diagnosed with certainty on FNAC based on characteristic cytomorphological features in an appropriate clinical and radiological setting. FNAC plays a pivotal role in diagnosing GCTTS and differentiating it from other giant cell rich lesions, thus obviating the need of tissue biopsy for diagnosis, which in turn helps the clinician in timely and adequate management of the patient.

Half-Heusler compounds are a broad class of materials that have attracted attention as possible high-temperature thermoelectric materials due to their favourable electrical transport behaviour and other features useful for device manufacturing. Although half-Heusler compounds exhibit an incredibly wide range of thermal conductivities, these are nonetheless often higher than other cutting-edge thermoelectric materials, which present a unique difficulty. It was observed that the chosen half-Heuslers were direct bandgap semiconductor with high power factors equivalent to the art of thermoelectric materials. Since the computed phonon is positive, the substance is dynamically stable. The high power factor and high Seebeck coefficient of the half-Heusler alloy are also revealed by the density of states. The stability of the material is also revealed by the formation energy. The optimized structure of LiYSi has band gap of 0.70 eV. The calculated power factor of n-type LiYSi is 7.31 × 1011Wm−1 K−2 s−1 per relaxation time. The calculated power factor per relaxation time of p-type LiYSi is 1.44 × 1012Wm−1 K−2 s−1.The power factor increases with increase in temperature. High n-type thermoelectric performance is produced by the interaction of low lattice thermal conductivity and excellent electrical transport characteristics. This suggests that at high temperatures, LiYSi is a potential n-type half-Heusler thermoelectric material. It is clear that the electronic structure has high valence band degeneracy, which contributes for good transport properties and results good thermoelectric material.

Abstract The application of Si detectors in the high-energy physics experiments requires a reliable performance in adverse radiation conditions, which is the main test for these detectors. Devices requiring high voltages face the problem of high peak electric field in the vicinity of junction termination. Various contours and design principles have evolved in the effort to reduce these peak fields. Out of many proposed solutions, metal-overhang and guard ring techniques are of general interest for improving the breakdown performance of the Si detectors (in the vertical devices). In the present work, the breakdown performance of metal-overhang and field-limiting ring techniques is compared for various values of junction depth, substrate resistivity, relative permittivity of the dielectric passivant and fixed oxide charge under similar conditions. The results demonstrate the superiority of metal-overhang technique over field-limiting ring technique for planar shallow-junction high-voltage Si detectors used in high-energy physics experiments.

In future linear colliders, such as the International Linear Collider (ILC), axial asymmetries in the accelerating cavities might generate asymmetries in the fields that kick the beam and tend to degrade the beam emittance, and thus the collider performances[1]. In this paper we present the results of calculations of transverse wakefields and RF kicks (from the powerand high order modescouplers of the acceleration structure) and their impact on the beam dynamics in the main linac as well as the bunch compressors of ILC. Coupler kicks have been implemented in the tracking code PLACET[2] to study and counteract the emittance growth induced by this effect. The results of the simulations are presented in this paper.

P-on-n silicon strip sensors having multiple guard-ring structures have been developed for High Energy Physics applications. The study constitutes the optimization of the sensor design, and fabrication of AC-coupled, poly-silicon biased sensors of strip width of 30μm and strip pitch of 55μm. The silicon wafers used for the fabrication are of 4 inch n-type, having an average resistivity of 2–5 kΩ cm, with a thickness of 300μm. The electrical characterization of these detectors comprises of: (a) global measurements of total leakage current, and backplane capacitance; (b) strip and voltage scans of strip leakage current, poly-silicon resistance, interstrip capacitance, interstrip resistance, coupling capacitance, and dielectric current; and (c) charge collection measurements using ALiBaVa setup. The results of the same are reported here.

Silicon detectors are being widely used in high energy physics (HEP) experiments as tracking and vertexing elements since the last three decades. The technology development is critical to maintain the performance of Si detectors in high radiation environment of the future HEP experiments. Owing to their better ability for higher charge collection efficiency and internal charge multiplication, there has been an increased interest for the relatively higher bulk doping density (1013–1014 cm−3) Si sensors. However, detailed investigations are required for studying the radiation damage effects on these low resistivity devices. In the present work, we report a systematic TCAD simulation study for the effect of proton fluence (up to 3 × 1015 neq.cm−2) on charge collection efficiency, leakage current and electric field distribution etc. of p-type Si diodes of varied thicknesses. A two trap proton damage model (Delhi model) is used to implement the radiation damage within TCAD framework. The results show promising future for these devices.

Radiation damage of the silicon detectors in future hadron colliders poses a major challenge for its reliable operation. It is crucial to investigate the neutron-induced radiation damage owing to its large flux in the calorimeters and the trackers. Measurement results on irradiated detectors are complemented by modeling for getting a deep insight into the device behavior. This work presents the development of neutron-induced radiation damage model in silicon detectors using TCAD simulation. A wide spectrum of measurement results available on neutron-irradiated silicon detectors, viz. full depletion voltage, leakage current, charge collection, and effective trapping times, helps in constraining the model parameters, resulting in a robust model for neutron damage. Modeling has been performed within the phase-space of the measurements, i.e. for different initial bulk resistivities, active thicknesses and for both polarities up to the fluence values of 9 × 1014 1 MeV neq cm−2 (where, 1 MeV neq refers to the equivalent fluence for monoenergetic neutrons of energy 1 MeV) and for two measurement temperatures, 253 and 263 K. The results obtained from the devised neutron damage model show a good agreement with the measurement results.

In order to address the problems caused by the harsh radiation environment during the high luminosity phase of the LHC (HL-LHC), all silicon tracking detectors (pixels and strips) in the CMS experiment will undergo an upgrade. And so to develop radiation hard pixel sensors, simulations have been performed using the 2D TCAD device simulator, SILVACO, to obtain design parameters. The effect of various design parameters like pixel size, pixel depth, implant width, metal overhang, p-stop concentration, p-stop depth and bulk doping density on the leakage current and critical electric field are studied for both non-irradiated as well as irradiated pixel sensors. These 2D simulation results of planar pixels are useful for providing insight into the behaviour of non-irradiated and irradiated silicon pixel sensors and further work on 3D simulation is underway.

Si detectors, in various configurations (strips and pixels), have been playing a key role in High Energy Physics (HEP) experiments due to their excellent vertexing and high precision tracking information. In future HEP experiments like upgrade of the Compact Muon Solenoid experiment (CMS) at the Large Hadron Collider (LHC), CERN and the proposed International Linear Collider (ILC), the Si tracking detectors will be operated in a very harsh radiation environment, which leads to both surface and bulk damage in Si detectors which in turn changes their electrical properties, i.e. change in the full depletion voltage, increase in the leakage current and decrease in the charge collection efficiency. In order to achieve the long term durability of Si-detectors in future HEP experiments, it is required to operate these detectors at very high reverse biases, beyond the full depletion voltage, thus requiring higher detector breakdown voltage. Delhi University (DU) is involved in the design, fabrication and characterization of multi-guard-ring furnished ac-coupled, single sided, p+n−n+ Si strip detectors for future HEP experiments. The design has been optimized using a two-dimensional numerical device simulation program (TCAD-Silvaco). The Si strip detectors are fabricated with eight-layers mask process using the planar fabrication technology by Bharat Electronic Lab (BEL), India. Further an electrical characterization set-up is established at DU to ensure the quality performance of fabricated Si strip detectors and test structures. In this work measurement results on non irradiated Si Strip detectors and test structures with multi-guard-rings using Current Voltage (IV) and Capacitance Voltage (CV) characterization set-ups are discussed. The effect of various design parameters, for example guard-ring spacing, number of guard-rings and metal overhang on breakdown voltage of test structures have been studied.

During the high luminosity upgrade of the LHC (HL-LHC) the CMS tracking system will face a more intense radiation environment than the present system was designed for. In order to design radiation tolerant silicon sensors for the future CMS tracker upgrade it is fundamental to complement the measurement with device simulation. This will help in both the understanding of the device performance and in the optimization of the design parameters. One of the important ingredients of the device simulation is to develop a radiation damage model incorporating both bulk and surface damage. In this paper we will discuss the development of a radiation damage model by using commercial TCAD packages (Silvaco and Synopsys), which successfully reproduce the recent measurements like leakage current, depletion voltage, interstrip capacitance and interstrip resistance, and provides an insight into the performance of irradiated silicon strip sensors.

The harsh radiation environment to be encountered at LHC (large hadron collider) and RHIC (relativistic heavy ion collider) poses a challenging task for the fabrication of Si microstrip detectors. Due to high luminosities, detectors are required to sustain very high voltage operation well exceeding the bias voltage needed to fully deplete them. The `overhanging' metal contact is now a well established technique for improving the breakdown performance of the Si microstrip detector. Based on computer simulation, the influence of various physical and geometrical parameters on the electrical breakdown of the Si detectors equipped with metal overhangs is extensively analysed. Furthermore, optimization of design parameters is performed to achieve breakdown voltages close to maximum realizable values. The simulation results are found to be in good agreement with experimental data.

We present here the simulation results on the emittance dilution in the curved International Linear Collider (ILC) main linac using Dispersion Free Steering (DFS) under the nominal misalignments of the beamline components. In order to understand the implication of the earth’s curvature on beam dynamics, we present the comparison of the curved linac with the laser straight geometry. We have studied the sensitivity of DFS to various misalignments and have also considered the effect of incorporating incoming beam jitter and quadrupole vibration jitter. In addition, the robustness of DFS to the failure of a corrector magnet or Beam Position Monitor (BPM) is investigated. The beneficial effect of dispersion bumps on the emittance dilution performance is also discussed.

A superconducting 1.3 GHz RF cavity is designed for acceleration of H− ions traveling at 81% of the speed of light. This 1.3 GHz cavity is considered for use in the squeezed International Linear Collider (ILC) section of the proposed high intensity H− ion linac at Fermilab, in order to accelerate a H− ion beam for the energy range of 420 MeV–1.2 GeV. The design of the earlier proposed 11-cell elliptical cavity is studied for higher order modes and the shape of the end cells is optimized to avoid trapped modes while keeping the field flatness and operating frequency undisturbed. A new alternative design based on nine cells is also proposed. Both inner and end cells are designed to achieve the optimal performance of the proposed cavity and higher order modes are studied.

The harsh radiation environment in future high-energy physics (HEP) experiments like LHC provides a challenging task to the performance of Si microstrip detectors. Normal operating condition for silicon detectors in HEP experiments are in most cases not as favourable as for experiments in nuclear physics. In HEP experiments the detector may be exposed to moisture and other adverse atmospheric environment. It is therefore utmost important to protect the sensitive surfaces against such poisonous effects. These instabilities can be nearly eliminated and the performance of Si detectors can be improved by implementing suitably passivated metal-overhang structures. This paper presents the influence of the relative permittivity of the passivant on the breakdown performance of the Si detectors using computer simulations. The semi-insulator and the dielectric passivated metal-overhang structures are compared under optimal conditions. The influence of various parameters such as passivation layer thickness, junction depth, metal-overhang width, device depth, substrate resistivity and fixed oxide charge on the junction breakdown voltage of these structures is extensively studied. The results presented in this work clearly demonstrate the superiority of the metal-overhang structure design employing semi-insulator passivated structures over dielectric passivated ones in realising a given breakdown voltage. The effect of bulk damage caused by hadron environment in the passivated Si detectors is simulated, to a first order approximation, by varying effective carrier concentration (calculated using Hamburg Model) and minority carrier lifetime. This approach allows getting an insight of the device behaviour after radiation damage by evaluating the electric field distribution, and thus proves helpful in predicting some interesting results.

In this paper, we present a two-dimensional computer-based analysis. We study extensively the influence of various parameters, such as the permittivity of the passivant dielectric, the passivation layer thickness, the junction depth, the n-layer thickness and the fixed oxide charge, on the breakdown voltage of the dielectric passivated silicon microstrip detector. The relative permittivity of the passivant dielectric layer deposited over the oxide influences the breakdown voltage once some minimum value of passivation layer thickness has been reached. The breakdown voltage of shallow junction devices remains nearly constant over a wide variation in passivation layer thickness. It is shown that, for deeper junction devices, the breakdown voltage remains almost constant up to a particular passivant layer thickness and then increases sharply. The effects of device depth and fixed oxide charge on the passivated device are also analysed. Based on this T-CAD simulation, we propose a layout for a detector protection structure with optimized performance. The design presently envisaged offers decisive advantages over a number of possible alternatives in silicon detector technology. We have found good agreement between previous experimental data and the simulation results.

Electrical properties of a device depend primarily on the active dopant concentration; understanding of the activation (annealing) process is crucial for the prediction of device behaviour. The present paper reports results from a computer based simulation approach to improve the breakdown performance of the device by studying the annealing behaviour of boron implanted in silicon. In order to have deep insight of the effect of defect complexes on the device performance, extended defect model has been incorporated in the simulation program. Optimization of annealing time, annealing temperature and dose has been performed, for the first time, incorporating a complete set of process induced defects like {113} defects, interface traps, dislocation loops and the optimization has been validated in terms of the breakdown performance of the device.

We present a first look at simulation results of emittance bumps implemented to preserve the emittance growth in the main linac of the proposed International Linear Collider (ILC). It is found that global orbit bumps used as a static tuning option after dispersion free steering can be extremely beneficial in further limiting the emittance growth in the main linac. Two kinds of emittance bumps, dispersion and wakefield, are studied in the present study. The effect of varying the location of these bumps along the main linac and the number of these bumps are studied. The influence of combining these bumps on the emittance growth is also discussed.

Silicon detectors are widely employed in the modern HEP experiments at particle colliders like LHC because of their excellent tracking and vertexing capabilities. However, the high irradiation levels of unprecedented luminosity of the HL-LHC physics programme of the CMS experiment, requires development of new generation of radiation hard silicon detectors. The radiation environment due to p-p collisions in HL-LHC would consist of both charged and uncharged particles (particularly protons and neutrons), which would reach fluence levels of about 1e16 n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eq</sub> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> in tracker and endcap calorimeter regions. These high levels of incident fluence interact with the silicon detectors and cause radiation damage and hence affect the macroscopic properties of the detectors, viz. full depletion voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FD</sub> ), leakage current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LEAK</sub> ) and charge collection efficiency (CCE). In the present work, Technology Computer Aided Design (TCAD) simulation software - Silvaco, has been used to develop a radiation damage model for neutron irradiation. The effects of neutron and proton irradiation on macroscopic properties of the silicon detectors are also compared and presented in this work. For proton irradiation the already developed proton radiation damage model has been used. The simulation results related to those macroscopic properties are found to be in good agreement with the measurement results.

The extension of Si detectors to the next generation high-energy physics experiments such as large hadron collider implies a reliable operation in high radiation environment which is by far the main technological challenge for these detectors. Multiple field limiting ring systems are well established as a means of protecting diffused junction from high voltage premature breakdown. Also, a spread of the Al metallization over the inter-cathodic field oxide sensibly lowers the electric field at the junction edges, thus, allowing for higher breakdown voltages. The purpose of this work is to combine the positive aspects of these two termination techniques with the aim of defining layouts and technological solutions suitable for the use of Si detectors in adverse radiation environment. An important feature is the potential distribution in the multi-guard ring structure, which depends on the bulk doping concentration, the oxide charge, the size of the gap between guard rings and the metal-overhang design. A systematic investigation on the breakdown performance is done by varying the physical and geometrical parameters such as width of overhang, guard ring spacing, junction depth and oxide charge. CAD tools are used for evaluating potential and electric field distributions within the device.

: Breast cancer is essential to be detected in primitive localized stage for enhancing the possibility of survival since it is considered as the major malediction to the women society around the globe. Most of the intelligent approaches devised for breast cancer necessitate expertise that results in reliable identification of patterns that conclude the presence of oncology cells and determine the possible treatment to breast cancer patients in order to enhance their survival feasibility. Moreover, the majority of the existing schemes of the literature incur intensive labor and time, inducing a predominant impact over the diagnosis time utilized for detecting breast cancer cells. An Intelligent Artificial Bee Colony and Adaptive Bacterial Foraging Optimization (IABC-ABFO) scheme is proposed for facilitating a better rate of local and global searching ability in selecting the optimal features subsets and optimal parameters of ANN considered for breast cancer diagnosis. In the proposed IABC-ABFO approach, the traditional ABC algorithm used for cancer detection is improved by integrating an adaptive bacterial foraging process in the onlooker bee and the employee bee phase that results in optimal exploitation and exploration. The investigation of results of the proposed IABC-ABFO approach facilitating the use of the Wisconsin breast cancer dataset showed a mean classification accuracy of 99.52% which is higher than the existing breast cancer detection schemes.

The study of the radiation tolerance and subsequent annealing effects on p+-n-n+ silicon micro strip detectors has been performed as a part of R&D program for the preshower detector in the CMS experiment. CMS silicon strip sensors were irradiated with 24 GeV protons at CERN proton synchrotron (PS) to a total fluence of 3/spl times/10/sup 14/ p/cm/sup 2/. Sensors were stored in freezer after irradiation and I-V and C-V measurements were carried out. Variation in full depletion voltage and leakage current have been studied as a function of annealing time. The breakdown performance of the device actually improves after irradiation due to the beneficial effect of type-inversion. The breakdown voltage increases further with annealing time. However, the leakage current increases tremendously just after irradiation. As the sensors are annealed, there is a drop in leakage current. The rate of annealing is observed to be temperature dependent. Hence in terms of leakage current, it seems that room temperature annealing is beneficial. However, if the sensors are annealed at room temperature, the depletion voltage will start rising after a short period of beneficial annealing. Hence for the silicon detectors to be used for preshower of CMS experiment, the temperature is set to freezer temperature to avoid reverse annealing. The beneficial and reverse annealing time constants are calculated and found to match well with predictions from Ziock parameterization.

Abstract The influence of crystal damage on the electrical properties and the doping profile of the implanted p+–n junction has been studied at different annealing temperatures using process simulator TMA-SUPREM4. This was done by carrying out two different implantations; one with implantation dose of 1015 BF2+ ions/cm2 at an energy of 80 keV and other with 1015 B+ ions/cm2 at 17.93 keV. Substrate orientation 〈1 1 1〉 of phosphorus-doped n-type Si wafers of resistivity 4 kΩ cm and tilt 7° was used, and isochronally annealing was performed in N2 ambient for 180 min in temperature range between 400°C and 1350°C. The diode properties were analysed in terms of junction depth, sheet resistance. It has been found that for low thermal budget annealing, boron diffusion depth is insensitive to the variation in annealing temperature for BF2+-implanted devices, whereas, boron diffusion depth increases continuously for B+-implanted devices. In BF2+-implanted devices, fluorine diffusion improves the breakdown voltage of the silicon microstrip detector for annealing temperature upto 900°C. For high thermal budget annealing, it has been shown that the electrical characteristics of BF2+-implanted devices is similar to that obtained in B+-implanted devices.

The Large Hadron Collider (LHC) has been extremely successful in its initial few years of its operation. The two general purpose experiments, the CMS and the ATLAS, announced the observation of a Higgs-like boson with mass of approximately 125 GeV using 5.1fb−1 and 5.3fb−1 of the integrated luminosity collected in proton–proton collisions at the s=7TeV and 8 TeV respectively. Since then additional data has been collected by the LHC. This work presents an update on the results of Higgs-like boson using additional ∼7fb−1 of integrated luminosity collected by the CMS experiment at s=8TeV In particular, results from the two most sensitive final states, i.e. H→ZZ→4l and H→γγ are described in detail.

Transient Current Technique (TCT) is one of the important methods to characterize silicon detectors and is based on the time evolution of the charge carriers generated when a laser light is shone on it. For red laser, charge is injected only to a small distance from the surface of the detector. For such a system, one of the charge carriers is collected faster than the readout time of the electronics and therefore, the effective signal at the electrodes is decided by the charge carriers that traverse throughout the active volume of the detector, giving insight to the electric field profile, drift velocity, effective doping density, etc. of the detector. Delhi University is actively involved in the silicon detector R&D and has recently installed a TCT setup consisting of a red laser system, a Faraday cage, a SMU (Source Measuring Unit), a bias tee, and an amplifier. Measurements on a few silicon pad detectors have been performed using the developed system, and the results have been found in good agreement with the CERN setup.

The Compact Muon Solenoid (CMS) is one of the general purpose experiments at the Large Hadron Collider (LHC), CeRN and has its tracker built of all silicon strip and pixel sensors. Si sensors are expected to play extremely important role in the upgrades of the existing tracker for future high luminosity environment and will also be used in future lepton colliders. however, properties of the silicon sensors have to be carefully understood before they can be put in the extremely high luminosity condition. At Delhi university (DU), we have been working on the development of Si sensor characterization system, as part of the collaboration with the CMS experiment and RD50 collaboration. this works reports the installation of current-voltage (I-V) and capacitance-voltage (C-V) systems at DU.

Silicon (Si) detectors are playing a key role in High Energy Physics (HEP) experiments due to their superior tracking capabilities. In future HEP experiments, like upgrade of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC), CERN, the silicon tracking detectors will be operated in a very intense radiation environment. This leads to both surface and bulk damage in Si detectors, which in turn will affect the operating performance of Si detectors. It is important to complement the measurements of the irradiated Si strip detectors with device simulation, which helps in understanding of both the device behavior and optimizing the design parameters needed for the future Si tracking system. An important ingredient of the device simulation is to develop a radiation damage model incorporating both bulk and surface damage. In this work, a simplified two-trap model is incorporated in device simulation to describe the type-inversion. Further, an extensive simulation of effective doping density as well as electric field profile is carried out at different temperatures for various fluences.

Abstract The CMS all-silicon tracker consists of 16,588 modules. Aligning these with the desired precision of a few micrometers is only feasible using track based alignment procedures. Ultimate local precision is now achieved by the determination of sensor curvatures. This faces the algorithms with about 200,000 parameters to be calculated simultaneously. The Millipede II program interfaced with CMS software is optimized to provide solution in one step. The main remaining challenges are systematic distortions in the achieved geometry that are systematically biasing the track parameters like the track momenta. These distortions are controlled by adding further information into the alignment workflow, e.g. the mass of decaying resonances. In addition, the orientation of the tracker with respect to the magnetic field of CMS is determined with a stand-alone chi-square minimization procedure. The geometries are finally carefully validated. The monitored quantities include the basic track quantities for tracks from both collisions and cosmic muons and physics observables like resonance masses.

A search for the Standard Model (SM) Higgs boson in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 1.6 fb−1 recorded by the CMS experiment. The search is conducted in the decay channel H → ZZ → 2l2ν. No excess is observed in the transverse mass distributions. Limits are set on the production of the Higgs boson in the context of the Standard Model and in the presence of a sequential fourth family of fermions with high masses.

Project-X is the proposed high intensity proton facility to be built at Fermilab, US. Its Superconducting Linac, to be used at first stage of acceleration, will be operated in continuous wave (CW) mode. The Linac is divided into three sections on the basis of operating frequencies &amp; six sections on the basis of family of RF cavities to be used for the acceleration of beam from 2.5 MeV to 3 GeV. The transition from one section to another can limit the acceptance of the Linac if these are not matched properly. We performed a study to calculate the acceptance of the Linac in both longitudinal and transverse plane. Investigation of most sensitive area which limits longitudinal acceptance and study of influence of failure of beam line elements at critical position, on acceptance are also performed.

Project-X is the proposed high intensity proton facility to be built at Fermilab, US. First stage of the Project-X consists of superconducting linac which will be operated in continuous wave (CW) mode to accelerate the beam from 2.5 MeV to 3 GeV. The operation at CW mode puts high tolerances on the beam line components, particularly on radiofrequency (RF) cavity. The failure of beam line elements at low energy is very critical as it results in mis-match of the beam with the following sections due to different beam parameters than designed parameter. It makes the beam unstable which causes emittance dilution, and ultimately results in beam losses. In worst case, it could affect the reliability of the machine and may lead to the shutdown of the Linac to replace the failed elements. Thus, it is important to study these effects and their compensation to get smooth beam propagation in linac. This paper describes the results of study performed for the failure of RF cavity & solenoid in SSR0 section.

Project-X is the proposed high intensity proton facility to be built at Fermilab, US. First stage of the Project-X consists of superconducting linac which will be operated in continuous wave (CW) mode to accelerate the beam from 2.5 MeV to 3 GeV. The operation at CW mode puts high tolerances on the beam line components, particularly on radiofrequency (RF) cavity. The failure of beam line elements at low energy is very critical as it results in mis-match of the beam with the following sections due to different beam parameters than designed parameter. It makes the beam unstable which causes emittance dilution, and ultimately results in beam losses. In worst case, it could affect the reliability of the machine and may lead to the shutdown of the Linac to replace the failed elements. Thus, it is important to study these effects and their compensation to get smooth beam propagation in linac. This paper describes the results of study performed for the failure of RF cavity &amp; solenoid in SSR0 section.

Project-X is the proposed high intensity proton facility to be built at Fermilab, US. Its Superconducting Linac, to be used at first stage of acceleration, will be operated in continuous wave (CW) mode. The Linac is divided into three sections on the basis of operating frequencies & six sections on the basis of family of RF cavities to be used for the acceleration of beam from 2.5 MeV to 3 GeV. The transition from one section to another can limit the acceptance of the Linac if these are not matched properly. We performed a study to calculate the acceptance of the Linac in both longitudinal and transverse plane. Investigation of most sensitive area which limits longitudinal acceptance and study of influence of failure of beam line elements at critical position, on acceptance are also performed.

Polychlorinateddibenzo-p-dioxins(PCDDs) and Polychlorinated dibenzofurans (PCDFs) represent a large group of industrial and byproduct compound is resistance to chemical and biological degradation and highly toxic.A series of 18 PCDD and PCDF compounds is subjected to QSTR studies by using differnt molecular descripters.The dependent variable used in this study represents log (EC 50 ) values (EC 50 -median effective concentration during a bioassay).The regression analysis of the data has shown that the toxicity of the compound can be modeled excellently in multi-parametric model.Its resulting model exhibited good R 2 value up to 0.8938.The present work contribute in the identification of those compounds which are very toxic and polluting our environment.

In the present work in mathematical modeling, quantitative structure activity relationship (QSAR) studies were performed on some 5, 6-dihydro-2-pyrones derivatives using statistical work.Using only 4 topological and physico-chemical molecular descriptors, we have achieved 84.81% correct classification of the compounds with and without its activity.A heurisimatedtic algorithm selects the best multiple linear regression(MLR) equation showed the correlation between the observed values and the estimated values of activity is very good(R=0.9209,R 2 =O.8481,PRESS=0.7312,=0.8210, S PRESS =0.2074).The results are discussed in the light of the main factors that influence the inhibitory activity of the HIV-1 protease. INTRODUCTION:The construction and investigation of Physico-Chemical Descriptor which could be used to describe molecular structures is one of the important directions of mathematical chemistry.Nowadays, scientists routinely work with collection of hundreds of thousands of molecular structures which cannot be efficiently processed without use of diverse sets of QSAR parameters.Modern QSAR science uses a broad range of atomic and molecular properties varying from merely empirical to quantumchemical.QSAR studies have often been carried out by using regression analysis the biological activities are being modeled using a set of molecular descriptor.

A search for the Standard Model Higgs boson in the H-&gt;ZZ-&gt;2l2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of both 7 and 8 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 5.0 fb-1 at 7 TeV and 5.0 fb-1 at 8 TeV. The search is optimized separately for the vector boson fusion and the gluon fusion production processes.No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 278-600 GeV/c2 range is excluded at 95% confidence level.

A search for the Standard Model Higgs boson in the H->ZZ->2l2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of both 7 and 8 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 5.0 fb-1 at 7 TeV and 5.0 fb-1 at 8 TeV. The search is optimized separately for the vector boson fusion and the gluon fusion production this http URL significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 278-600 GeV/c2 range is excluded at 95% confidence level.

We present an evaluation of the CMS expected 95% C.L. exclusion limits in early Standard Model (SM) Higgs boson searches.The results are based on a statistical combinations of multiple recent Monte-Carlo analyses: H → WW * → 2l2ν and H → ZZ * → 4l decay channels, where l stands for e or µ.We show that these two channels alone should allow for excluding the Standard Model Higgs boson in the mass range of 140-230 GeV by the time when CMS collects 1 fb -1 of data at a center-of-mass energy of 14 TeV.We also give an estimate of how the change of the LHC center-of-mass collision energy from 14 to 10 TeV would impact the Higgs boson exclusion limits.

The Low Gain Avalanche Detectors (LGADs) have the unique characteristic to provide amplification to the particle signal by using a controlled local avalanche mechanism. These devices are being explored by the HEP community because, while it is known that in standard silicon detectors the signal-to-noise ratio falls drastically with fluence, in LGAD devices this can be made sufficiently high to potentially overcome this problem. However, the existing irradiation studies show that at high fluences, the LGAD internal gain disappears and is no more significant. In this work, we have studied the effect of various design parameters of the LGAD device on its gain characteristic, at different irradiation levels. With the acquired understanding, we have also tried to tune the LGAD gain so to be suited for operation in a high radiation environment.

The present paper deals with the comprehensive studies of phonon dynamics in alkali metal (M) doped C 60 ( MC 60 ) solids in fcc phase using a rigid ion model with pairwise interionic interaction potential. The investigations include the computation of the phonon density of states, the specific heat, the Gruneisen parameters, thermal expansion and thermal expansion coefficient and the phonon-dispersion curves of RbC 60 . The analysis incorporates the van der Waal's and Coulomb interactions for alkali metal– C 60 as well C 60 – C 60 molecule and show fairly good agreement with reported inelastic neutron scattering results for RbC 60 . We have found that thermal expansion coefficient at room temperature is in the range 4.3–6.2 × 10 -5 K -1 , which is of the order of pure C 60 solid (6.1 × 10 -5 K -1 ). Comparing the thermal expansion coefficient of different alkali-doped solids, we conclude that doping decreases anharmonicity in general, and further it decreases with increase in size of the alkali metal. The results have been found to present an overall consistent interpretation of the available experimental data.

Detailed results of estimations and simulations for the RF kick caused by input and HOM couplers of the ILC acceleration structure are presented. Results of possible beam emittance dilution caused by RF kick are discussed for the main LINAC acceleration structure, and the RF structures of the ILC bunch compressors BC1 and BC2. Methods of the RF kick reduction are discussed.

The International Linear Collider (ILC) is a proposed electron-positron accelerator requiring very small spot-size at the interaction point, and thus necessitates very tight tolerances on beamline elements. For static tuning of the machine a few methods like dispersion-free steering (DFS) or kick minimization (KM) techniques was proposed. The further suppression of emittance growth can be achieved by using close orbit emittance bumps. Stability of ILC is determined by the stability of the site, additional noises of beamline component, energy and kicker jitter and performance of the train-to-train and intra-train feedback. We discuss the performances of the Adaptive Alignment technique, which keeps the accelerator dynamically aligned in the presence of ground motion and technical noises. This presentation is an overview of two posters THPMN107 and THPMN108, presented at PAC07.

In this work we present simulation results on the effect of ground motion on the main linac performance of the proposed International Linear Collider (ILC), and then use adaptive alignment (AA) technique to correct it. The adaptive alignment technique is investigated for the ILC main linac and its limitations are studied. Then ground motion studies are performed using the simulation program LIAR and the beneficial effects of implementing AA algorithm are further discussed.

Si detectorsBhardwaj, Ashutosh are now being widely used in experimental high energy physics (HEP). This detector technology is more popularly used as particle tracking detectors. Its application is diverse, viz. from the track reconstruction, various parameters of the incident particle like the flight of path, the momentum in the presence of a magnetic field, secondary or a decay vertex, interaction vertex, etc., can be deduced. Si detectors are also used as active layers in sampling calorimeters in some of the experiments.

As the rate of the incoming fluence increases, the density of the traps also increases in the silicon bulk. This leads to a decrease in the charge collected limiting the long term operation of the silicon detectors. In the work presented here, we have calculated the effective trapping probability in a proton irradiated silicon pad detector using transient currentTransient current simulationsSimulations and ROOT software.

The silicon sensors to be deployed in the next generation high energy physics experiments for operation in high luminosity scenarios, will require a high level of radiation tolerance. AC-coupled silicon strip sensors integrated with biasing poly-silicon resistors have been fabricated in collaboration with the Bharat Electronics Limited foundry using 4 inch n-type wafers in p-on-n configuration. Several sensors were irradiated with protons at different fluences at the Karlsruhe Cyclotron facility under the Advanced European Infrastructures for Detectors at Accelerators (AIDA) program. This paper reports on these radiation hardness study performed on the AC-coupled silicon sensors fabricated in India. The characterization comprises of electrical tests, including total current, voltage and strip scans and charge collection studies.

The CMS tracking system will demand a large quantity of multi-strip silicon sensors, which must fulfill stringent tolerance criteria to maintain the physics performance in the High Luminosity (HL) phase of the LHC. Thus, a subset of the fabricated sensors must be extensively tested prior to the installation in the main detector system. This will be achieved through measurement of various global and strip parameters of silicon strip sensors as envisaged in a detailed quality assurance program for phase II upgrade of CMS tracker. Also, to handle the large quantity of the pixel and strip sensors and other constraints, the characterization setup should have multi-functionality features, including automation. A fully automated and programmable characterization system for testing silicon multi-strip sensors has been under development at University of Delhi. The entire system is controlled though an Automated Characterization Suite (ACS). Various features of the characterization system along with some measurement results are presented in this work.

An overview of recent results of single-top quark production at the LHC using data collected with the CMS detector is presented. The CMS experiment has measured the electroweak production of the top quark in three production modes, namely t-channel, tW-channel, and s-channel. Measurements of the rare processes involving a single-top quark with a Z boson and a single-top quark with a γ are also discussed. All measurements are in agreement with the standard model prediction, and no sign of physics beyond the standard model is observed.

The inclusive cross-section for tW production in proton-proton collisions at $\sqrt{s} = 13$ TeV is measured for an integrated luminosity of 35.9 fb$^{-1}$ collected by the CMS experiment. The measurement is performed using events with one electron and one muon in the final state and at least one b-quark jet, and utilises kinematic differences between the signal and the dominating $t\bar{t}$ background using multivariant discriminants which is designed to disentangle the two processes. The measured cross-section of $\sigma = 63.1 \pm 1.8~({\rm stat}) \pm 6.4~({\rm syst}) \pm 2.1~({\rm lumi})$ pb is observed to be in agreement with the Standard Model.

A major concern with the use of silicon sensor in nuclear and particle physics experiments is its survival in the intense radiation environment.The unprecedented increase in fluence in these experiments affects its long-term sustainability due to both bulk and surface damage, resulting in the deterioration of its static and dynamic properties.Hence, stringent tolerance criteria are imposed on these sensors to maintain the physics performance of an experiment.This necessitates the testing of the silicon sensors' performance under temperature and humidity controlled, dark and dust free, environment.Our Group at the University of Delhi is in the process of establishing such a characterization system, for the first time in India, for testing a large array of silicon micro-strip sensors.A set of electrical characterization units, capable of providing 3000 V and measuring pico-Ampere currents and pico-Farad capacitances, are installed in the facility.Among other features, the probe station has a capability to translate in three directions, with a step size of 2 micro-meter over the range of 20 cm in XY directions.The entire system is interfaced through the Automated Characterization Suite (ACS) software and can be programmed in such a way that one does not need to intervene manually as it switches from one silicon strip to another.Several measurements involving currents, capacitances and resistances can be performed for the total, strip and inter-strip parameters.It is primarily envisioned to utilize the setup for the qualification of micro-strip silicon sensors for the CMS outer tracker in the high-luminosity LHC upgrade.In this work, we present the details of this state-of-the-art characterization system and measurements performed on silicon strip sensors.

In this work we present simulation results on the effect of ground motion on the main linac performance of the proposed International Linear Collider (ILC), and then use adaptive alignment (AA) technique to correct it. The adaptive alignment technique is investigated for the ILC main linac and its limitations are studied. Then ground motion studies are performed using the simulation program LIAR and the beneficial effects of implementing AA algorithm are further discussed.

Silicon Detector (SiD) is one of the proposed detector for future $e^+e^-$ Linear colliders, like International Linear Collider (ILC). The estimated neutron background for ILC is around 1 - 1.6 x 1010 1-MeV equivalent neutrons cm-2 year-1 for the Si micro strip sensors to be used in the innermost vertex detector. The p+n-n+ double-sided Si strip sensors are supposed to be used as position sensitive sensors for SiD. On the $n^+n^-$ side of these sensors, shorting due to electron accumulation leads to uniform spreading of signal over all the n+ strips. Hence inter-strip isolation becomes one of the major technological challenges. One of the attractive methods to achieve the inter-strip isolation is the use of uniform p-type implant on the silicon surface (p-spray). Another alternative is the use of floating p-type implants that surround the n-strips (p-stop). However, the high electric fields at the edge of the p-spray/p-stop have been shown to induce pre-breakdown micro-discharge. An optimization of the implant dose profile of the p-spray and p-stop is required to achieve good electrical isolation while ensuring satisfactory breakdown performance of the Si sensors. In the present work, we report the preliminary results of simulation study performed on the $n^+n^-$ Si sensors, equipped with p-spray and p-stops, using SILVACO tools.

The Silicon strip sensors in high energy physics collider experiments have excellent capabilities of vertexing and tracking of incoming particles produced as a result of collision. These sensors are placed in intense radiation environment and hence undergo severe bulk and surface radiation damage. In order to operate these detectors with good physics performance, they must be subjected to stringent tolerance limits for their design parameters. These design parameters include global, strip and inter-strip parameters. The sensors are characterized for these parameters in temperature and humidity controlled environment, which are then accepted or rejected based on the constraints imposed on these parameters offered by a specific experiment.Our group at the University of Delhi is engaged in the process of developing a silicon sensor quality control centre for testing a large number of silicon micro-strip sensors. The primary objective of this facility is the qualification of these sensors for the outer tracker of the CMS experiment in High-Luminosity LHC upgrade. The system consists of a probe station and a set of electrical characterization units. The entire system is interfaced through the Automated Characterization Suite (ACS) software which allows the automatic characterization of the whole multistrip sensor without any manual intervention. The set-up has been under testing for measurements involving global, strip and inter-strip parameters. In this work, we present the details of this characterization system and measurements performed on some silicon strip sensors. To calibrate our setup the same set of measurements are performed with the setup available at the University of Pisa, Italy. The measurements performed using these two setups are found to be consistent with each other.

Silicon detectors are expected to experience an unprecedented radiation flux in the future upgrades of the detectors at the Large Hadron Collider (LHC). The challenging radiation environment of these experiments will severely affect the performance of such detectors, degrading their detection capabilities and imposing severe operational conditions. The modeling of the detectors through Monte Carlo simulation represents a necessary step for the detailed understanding of the silicon detector performance before and after radiation damage; also for setting up optimized design rules aiming to mitigate the detrimental effect of the radiation damage. In the present work, a comparison of simulation results, obtained from- Technology Computer-Aided Design (TCAD) simulation software: Silvaco and Synopsys- used to predict silicon detectors performance, is presented. The effects of radiation damage are incorporated in the TCADs, using an effective multiple traps model. A systematic study of the sensitivity of the silicon detector's macroscopic parameters to the modeling of traps is performed. The simulation results for static electrical parameters, such as the leakage current and the full depletion voltage, obtained by the TCADs are presented and compared.

Phonon dynamics of alkali metal atom, M doped in C60, forming MC60 solids in fcc phase has been studied. The calculations take into account Van-der-Waals and Coulomb interactions for M-C60 and C60-C60 and show fairly good agreement with reported neutron scattering results for RbC60. The calculations have also been done following Rigid Shell Model (RSM). We also perform calculations for specific heat, Gruneisen parameter, thermal expansion and thermal expansion coefficient.

The very intense radiation environment of high luminosity future colliding beam experiments (like LHC) makes radiation hardness the most important issue for Si detectors. One of the central issues concerning all LHC experiments is the breakdown performance of these detectors. The major macroscopic effect of radiation damage in determining the viability of long-term operation of Si sensors is the change in effective charge carrier concentration (Neff), leading to type- inversion. Floating field limiting guard rings have been established as means of improving the breakdown performance of Si detectors. In this work the usefulness of the guard rings in improving the breakdown performance of detectors after type- inversion has been studied. Simulations are carried out to study the effect of change in Neff on the breakdown performance of optimized guard ring structure using two dimensional device simulation program, TMA-MEDICI. Detailed calculations using Hamburg Model have allowed the parameterization of these effects to simulate the operation scenario of Si detectors over 10 years of LHC operation.

We present the preliminary results of the tt̄ pair production cross‐section measurements and the single top quark exclusion limits carried out by the DØ and the CDF collaborations in Run II of the Tevatron. The dataset for the various measurements ranges from 140 pb−1 to 350 pb−1.

The study of the radiation tolerance and subsequent annealing effects on p+-n-n+ silicon micro strip detectors has been performed as a part of R&D program for the preshower detector in the CMS experiment. CMS silicon strip sensors were irradiated with 24 GeV protons at CERN proton synchrotron (PS) to a total fluence of 3/spl times/10/sup 14/ p/cm/sup 2/. Sensors were stored in freezer after irradiation and I-V and C-V measurements were carried out. Variation in full depletion voltage and leakage current have been studied as a function of annealing time. The breakdown performance of the device actually improves after irradiation due to the beneficial effect of type-inversion. The breakdown voltage increases further with annealing time. However, the leakage current increases tremendously just after irradiation. As the sensors are annealed, there is a drop in leakage current. The rate of annealing is observed to be temperature dependent. Hence in terms of leakage current, it seems that room temperature annealing is beneficial. However, if the sensors are annealed at room temperature, the depletion voltage will start rising after a short period of beneficial annealing. Hence for the silicon detectors to be used for preshower of CMS experiment, the temperature is set to freezer temperature to avoid reverse annealing. The beneficial and reverse annealing time constants are calculated and found to match well with predictions from Ziock parameterization.

In this paper, the influence of various physical and geometrical parameters such as permittivity of passivant dielectric, passivation layer thickness, junction depth, n-layer thickness and fixed oxide charge on the breakdown voltage of semi-insulator passivated silicon microstrip detector is investigated using a 2-dimensional T-CAD simulator. Comparisons of this structure with most commonly used dielectric are also studied. The breakdown voltage of semi-insulator passivated devices remains nearly constant over a wide variation in passivation layer thickness for all values of junction depth, indicating that passivation layer thickness is not an important design parameter in high voltage planar devices passivated with semi-insulator. The influence of the fixed oxide charge on the breakdown voltage of semi-insulator passivated device is found to be negligible. Thus, the present study shows that the semi-insulator passivated structures allow for a design of Si strip detectors reducing dead layer and making the detectors more suitable for next generation high energy physics experiments and improve the breakdown voltage. In contrast, dielectric passivated films are preferred if compactness of detectors are desired. A good agreement between the experiment and simulation is also observed.

The very intense radiation environment of high luminosity future colliding beam experiments (like LHC) makes radiation hardness the most important issue for Si detectors. One of the central issues concerning all LHC experiments is the breakdown performance of these detectors. The major macroscopic effect of radiation damage in determining the viability of long-term operation of Si sensors is the change in effective charge carrier concentration (N/sub eff/), leading to type-inversion. Floating field limiting guard rings have been established as means of improving the breakdown performance of Si detectors. In this work the usefulness of the guard rings in improving the breakdown performance of detectors after type-inversion has been studied. Simulations are carried out to study the effect of change in N/sub eff/ on the breakdown performance of optimized guard ring structure using two dimensional device simulation program, TMA-MEDICI. Detailed calculations using Hamburg Model have allowed the parameterization of these effects to simulate the operation scenario of Si detectors over 10 years of LHC operation.

The importance of Si sensors in high-energy physics (HEP) experiments can hardly be overemphasized. However, the high luminosity and the high radiation level in the future HEP experiments, like Large Hadron Collider (LHC), has posed a serious challenge to the fabrication of Si detectors. For the safe operation over the full LHC lifetime, detectors are required to sustain very high voltage operation, well exceeding the bias voltage needed to full deplete the heavily irradiated Si sensors. Thus, the main effort in the development of Si sensors is concentrated on a design that avoids p-n junction breakdown at operational biases. Among various proposed techniques, Field-limiting Ring (FLR) (or guard ring) and Metal-Overhang (MO) are technologically simple and are suitable for vertical devices. Since high-voltage planar Si junctions are of great importance in the HEP experiments, it is very interesting to compare these two aforementioned techniques for achieving the maximum breakdown voltage under optimal conditions. In the present work, the breakdown performance of metal-overhang and field-limiting ring techniques is compared for various values of junction depth and fixed oxide charge under similar conditions using two dimensional device simulation program TMA-MEDICI.

The utility of silicon microstrip detectors in future high luminosity colliders, like LHC requires some serious issues concerning radiation hardness to be carefully considered. The performance of metal-overhang (MO) equipped Si micro-strip sensors has been studied after irradiation for the preshower detector to be used in CMS experiment at LHC, CERN. The parameterization of these effects has been performed using Hamburg model to simulate the operation scenario of MO equipped sensors over 10 years of LHC operation. The utility of overhanging metal extension as junction termination technique after type-inversion has been explored for the first time in this work Several interesting results like a shift in the optimal oxide thickness in MO equipped structures after irradiation have been reported. It has been found that the breakdown performance of the device actually improves after irradiation due to the beneficial effect of type-inversion. Dielectric and semi-insulator passivated MO equipped structures have been compared after irradiation in this study. Also, the impact of various crucial geometrical parameters like device depth (W/sub N/), width of back N+ layer used for ohmic contact (W/sub N//sup +/) and width of overhang extension (W/sub MO/) on the metal-overhang equipped structure after type-inversion has been presented in detail.

The very intense radiation environment of high luminosity future colliding beam experiments (LHC, etc.) makes radiation hardness the most important issue for Si detectors. The crucial question is whether the Si strip detectors can withstand the harsh radiation environment for sufficiently long time (full LHC lifetime) and hence the central issue concerning all LHC experiments is the breakdown performance of these detectors. In this paper the simulations have been performed to analyze electrical parameters for the most deleterious long-term effect of radiation: the change in effective charge carrier concentration and resulting increase in full depletion bias. Detailed calculations using Hamburg Model have allowed the parameterization of these effects, and helped to simulate the operation scenario of Si detectors over 10 years of LHC operation. The systematic studies of the electric field to get an insight into the device behavior provide, for the first time, a possible explanation for the improvement in breakdown performance with radiation. Simulation study is also carried on optimized guard ring structures to study the change in guard voltage distribution after 10 years of neutron radiation damage.

The foreseen high fluence environment in future nuclear and particle physics experiments requires corresponding radiation hard silicon sensors. However, these sensors must be tested for their charge collection performance and long-term radiation sustainability prior to their usage. The Transient Current Technique (TCT) is a useful characterization technique for investigating the radiation damage effects. This work reports measurements on silicon pad detectors carried out using the TCT setup installed at the University of Delhi. Measurement results are complemented with TCAD simulation, which is useful to get an insight of the silicon detector.

Abstract The low gain avalanche detector (LGAD), having a unique feature of built-in charge multiplication, is more efficient in terms of charge collection (CC) than the traditional silicon detector even after irradiation. However, a dramatic decrease in the charge multiplication beyond a fluence of 3 × 10 14 <?CDATA $n_{\textrm{eq}}\cdot$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>n</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>eq</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>⋅</mml:mo> </mml:math> cm −2 is observed in the measurements. In the reported work, TCAD CC simulations are carried out on various physical and geometrical LGAD design parameters with the aim to understand and extend the radiation hardness capabilities. It is observed that a thin LGAD with low bulk resistivity may survive up to a fluence of 3 × 10 15 <?CDATA $n_{\textrm{eq}}\cdot$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>n</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>eq</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>⋅</mml:mo> </mml:math> cm −2 for an optimal choice of p-well design. A detailed investigation including CC and leakage current validation with experimental data and 1D electric field profile, in support of optimizations performed, is also provided.