Mark Pesaresi

Two high-accuracy goniometers equipped with two bent silicon crystals were installed in the betatron cleaning insertion of the CERN Large Hadron Collider (LHC) during its long shutdown. First beam tests were recently performed at the LHC with 450 GeV/c and 6500 GeV/c stored proton beams to investigate the feasibility of beam halo collimation assisted by bent crystals. For the first time channeling of 6500 GeV/c protons was observed in a particle accelerator. A strong reduction of beam losses due to nuclear inelastic interactions in the aligned crystal in comparison with its amorphous orientation was detected. The loss reduction value was about 24. Thus, the results show that deflection of particles by a bent crystal due to channeling is effective for this record particle energy.

New experiments on crystal assisted collimation have been carried out at the CERN SPS with stored beams of 120 GeV/c protons and Pb ions. Bent silicon crystals of 2 mm long with about 170 μrad bend angle and a small residual torsion were used as primary collimators. In channeling conditions, the beam loss rate induced by inelastic interactions of particles with the crystal nuclei is minimal. The loss reduction was about 6 for protons and about 3 for Pb ions. Lower reduction value for Pb ions can be explained by their considerably larger ionization losses in the crystal. In one of the crystals, the measured fraction of the Pb ion beam halo deflected in channeling conditions was 74%, a value very close to that for protons. The intensity of the off-momentum halo leaking out from the collimation station was measured in the first high dispersion area downstream. The particle population in the shadow of the secondary collimator–absorber was considerably smaller in channeling conditions than for amorphous orientations of the crystal. The corresponding reduction was in the range of 2–5 for both protons and Pb ions.

A study of crystal assisted collimation has been continued at the CERN SPS for different energies of stored beams using 120 GeV/c and 270 GeV/c protons and Pb ions with 270 GeV/c per charge. A bent silicon crystal used as a primary collimator deflected halo particles using channeling and directing them into the tungsten absorber. A strong correlation of the beam losses in the crystal and off-momentum halo intensity measured in the first high dispersion (HD) area downstream was observed. In channeling conditions, the beam loss rate induced by inelastic interactions of particles with nuclei is significantly reduced in comparison with the non-oriented crystal. A maximal reduction of beam losses in the crystal larger than 20 was observed with 270 GeV/c protons. The off-momentum halo intensity measured in the HD area was also strongly reduced in channeling conditions. The reduction coefficient was larger than 7 for the case of Pb ions. A strong loss reduction was also detected in regions of the SPS ring far from the collimation area. It was shown by simulations that the miscut angle between the crystal surface and its crystallographic planes doubled the beam losses in the aligned crystal.

A charged particle telescope has been constructed for data taking at high rates in a CERN 400 GeV/c proton beam line. It utilises ten planes of silicon microstrip sensors, arranged as five pairs each measuring two orthogonal coordinates, with an active area of 3.8 × 3.8 cm2. The objective was to provide excellent angular and spatial resolution for measuring the trajectories of incident and outgoing particles. The apparatus has a long baseline, of approximately 10 m in each arm, and achieves an angular resolution in the incoming arm of 2.8 μrad and a total angular resolution on the difference of the two arms of 5.2 μrad, with performance limited by multiple scattering in the sensor layers. The sensors are instrumented by a system based on the CMS Tracker electronic readout chain, including analogue signal readout for optimal spatial resolution. The system profits from modified CMS software and hardware to provide a data acquisition capable of peak trigger rates of at least 7 kHz. We describe the sensor readout, electronic hardware and software, together with the measured performance of the telescope during studies of crystal channeling for the UA9 collaboration. Measurements of a previously unobserved periodic movement of the beam are also presented and the significance of such an effect for precise studies such as for channeling is discussed.

The FC7 is a flexible, μTCA compatible Advanced Mezzanine Card (AMC) for generic data acquisition/control applications. Built around the Xilinx Kintex-7 FPGA, the FC7 provides developers with a platform which has access to a large array of configurable I/O, primarily delivered from on-board FPGA Mezzanine Card (FMC) sockets. Targeting users of high-speed optical links in high energy physics experiments, the board is capable of driving and receiving links up to 10 Gbps. This paper presents test results from the first set of pre-production prototypes and reports on FC7 uses and applications towards upgrades in CMS.

The results of observation and studies of focusing of 400 GeV/c proton beam with the help of bent single crystals are presented. Two silicon crystals have been used in the measurements. The focal length of the first and second crystals is found to be 1.48 m and 0.68 m, respectively. The mean square size of the horizontal profile in the focus was 3.1 and 4.3 times as small as at the exit of the crystals.

A new tracking detector is under development for use by the CMS experiment at the High-Luminosity LHC (HL-LHC). A crucial requirement of this upgrade is to provide the ability to reconstruct all charged particle tracks with transverse momentum above 2–3 GeV within 4 μs so they can be used in the Level-1 trigger decision. A concept for an FPGA-based track finder using a fully time-multiplexed architecture is presented, where track candidates are reconstructed using a projective binning algorithm based on the Hough Transform, followed by a combinatorial Kalman Filter. A hardware demonstrator using MP7 processing boards has been assembled to prove the entire system functionality, from the output of the tracker readout boards to the reconstruction of tracks with fitted helix parameters. It successfully operates on one eighth of the tracker solid angle acceptance at a time, processing events taken at 40 MHz, each with up to an average of 200 superimposed proton-proton interactions, whilst satisfying the latency requirement. The demonstrated track-reconstruction system, the chosen architecture, the achievements to date and future options for such a system will be discussed.

Bent silicon crystals mounted on high-accuracy angular actuators were installed in the CERN Super Proton Synchrotron (SPS) and extensively tested to assess the feasibility of crystal-assisted collimation in circular hadron colliders. The adopted layout was exploited and regularly upgraded for about a decade by the UA9 Collaboration. The investigations provided the compelling evidence of a strong reduction of beam losses induced by nuclear inelastic interactions in the aligned crystals in comparison with amorphous orientation. A conceptually similar device, installed in the betatron cleaning insertion of CERN Large Hadron Collider (LHC), was operated through the complete acceleration and storage cycle and demonstrated a large reduction of the background leaking from the collimation region and radiated into the cold sections of the accelerator and the experimental detectors. The implemented layout and the relevant results of the beam tests performed in the SPS and in the LHC with stored proton and ion beams are extensively discussed.

Abstract Measurements of the interaction of positively charged particles with bent crystals were obtained by developing a new and consolidated analysis method, for the use of UA9 collaboration. The method was deployed to characterize crystals with a length of a few mm along the beam direction and a bending angle in the order of 10 μrad to 100 μrad, typically exploited in the CERN accelerators. To assess their properties and quality, the crystals have been investigated in the Super Proton Synchrotron North Area with a beam of mixed hadrons at 180 GeV. The UA9 telescopic tracker has been used to collect the data. Some of them are used in the present study to describe and validate the applied data-analysis methodology.

The possibility for optimization of crystal assisted collimation has been studied at the CERN SPS for stored beams of protons and Pb ions with 270 GeV/c per unit charge. A bent silicon crystal used as a primary collimator deflects halo particles in the channeling regime, directing them into a tungsten absorber. In channeling conditions a strong reduction of off-momentum particle numbers produced in the crystal and absorber, which form collimation leakage, has been observed in the first high dispersion (HD) area downstream. The present study shows that the collimation leakage is minimal for some values of the absorber offset relative to the crystal. The optimal offset value is larger for Pb ions because of their considerably larger ionization losses in the crystal, which cause large increases of particle betatron oscillation amplitudes. The optimal absorber offset allows obtaining maximal efficiency of crystal-assisted collimation.

A 130 nm CMOS chip has been designed for silicon microstrip readout at the SLHC. The CBC has 128 channels, and utilises a binary un-sparsified architecture for chip and system simplicity. It is designed to read out signals of either polarity from short strips (capacitances up to ~ 10 pF) and can sink or source sensor leakage currents up to 1 μA. Details of the design and measured performance are presented.

Channeling is the confinement of the trajectory of a charged particle in a crystalline solid. Positively charged particles channeled between crystal planes oscillate with a certain oscillation length, which depends on particle energy. A crystal whose thickness is half the oscillation length for planar channeling may act as a mirror for charged particles. If the incident angle of the particle trajectory with the crystal plane is less than the critical angle for channeling, under-barrier particles undergo half an oscillation and exit the crystal with the reversal of their transverse momentum, i.e., the particles are “mirrored” by the crystal planes. Unlike the traditional scheme relying on millimeter-long curved crystals, particle mirroring enables beam steering in high-energy accelerators via interactions with micrometer-thin straight crystal. The main advantage of mirroring is the interaction with a minimal amount of material along the beam, thereby decreasing unwanted incoherent nuclear interactions. The effectiveness of the mirror effect for ultrarelativistic positive particles has been experimentally proven at external lines of CERN-SPS. The mirroring effect in a 26.5-μm-thick Si crystal has been studied in the experiment with a narrow beam of 400 GeV/c protons at the CERN-SPS. The reflection efficiency for a quasi-parallel beam is larger than 80%.

In ideal two-stage collimation systems, the secondary collimator–absorber should have its length sufficient to exclude practically the exit of halo particles with large impact parameters. In the UA9 experiments on the crystal assisted collimation of the SPS beam a 60 cm long tungsten bar is used as a secondary collimator–absorber which is insufficient for the full absorption of the halo protons. Multi-turn simulation studies of the collimation allowed to select the position for the beam loss monitor downstream the collimation area where the contribution of particles deflected by the crystal in channeling regime but emerging from the secondary collimator–absorber is considerably reduced. This allowed observation of a strong leakage reduction of halo protons from the SPS beam collimation area, thereby approaching the case with an ideal absorber.

A deflection efficiency of about 61% was observed for 400 GeV/c protons due to channeling, most strongly along the 〈110〉 axis of a bent silicon crystal. It is comparable with the deflection efficiency in planar channeling and considerably larger than in the case of the 〈111〉 axis. The measured probability of inelastic nuclear interactions of protons in channeling along the 〈110〉 axis is only about 10% of its amorphous level whereas in channeling along the (110) planes it is about 25%. High efficiency deflection and small beam losses make this axial orientation of a silicon crystal a useful tool for the beam steering of high energy charged particles.

The UA9 experimental equipment was installed in the CERN-SPS in March '09 with the aim of investigating crystal assisted collimation in coasting mode. Its basic layout comprises silicon bent crystals acting as primary collimators mounted inside two vacuum vessels. A movable 60 cm long block of tungsten located downstream at about 90 degrees phase advance intercepts the deflected beam. Scintillators, Gas Electron Multiplier chambers and other beam loss monitors measure nuclear loss rates induced by the interaction of the beam halo in the crystal. Roman pots are installed in the path of the deflected particles and are equipped with a Medipix detector to reconstruct the transverse distribution of the impinging beam. Finally UA9 takes advantage of an LHC-collimator prototype installed close to the Roman pot to help in setting the beam conditions and to analyze the efficiency to deflect the beam. This paper describes in details the hardware installed to study the crystal collimation during 2010.

We present the design of CBC2, the new version of the CMS Binary Chip ASIC for the readout of CMS Tracker Phase-two upgrade. CBC2, designed in 130nm CMOS, doubles the input channels to 254 and will be bump-bonded to the substrate. The ASIC is designed to instrument double layer modules in the outer tracker, consisting of two overlaid silicon sensors with aligned microstrips, and incorporates the logic to identify L1 trigger primitives in the form of ``stubs'': high transverse-momentum candidates which are isolated from the low momentum background by selecting correlated hits between two closely separated microstrip sensors. The functionality of the coincidence logic, which includes rejection of wide clusters and offset correction to account for the position of the module in the R-ϕ plane, is described in detail.

Spectral maxima of parametric X-ray radiation (PXR) produced by 400 GeV/c protons in bent silicon crystals aligned with the beam have been observed in an experiment at the H8 external beam of the CERN SPS. The total yield of PXR photons was about 10−6 per proton. Agreement between calculations and the experimental data shows that the PXR kinematic theory is valid for bent crystals with sufficiently small curvature as used in the experiment. The intensity of PXR emitted from halo protons in a bent crystal used as a primary collimator in a circular accelerator may be considered as a possible tool to control its crystal structure, which is slowly damaged because of irradiation. The intensity distribution of PXR peaks depends on the crystal thickness intersected by the beam, which changes for different orientations of a crystal collimator. This dependence may be used to control crystal collimator alignment by analyzing PXR spectra produced by halo protons.

This paper is devoted to an experimental study of focusing and defocusing positively charged particle beams with the help of specially bent single crystals.Four crystals have been fabricated for this purpose.The studies have been performed at the CERN SPS in 400 GeV=c proton and 180 GeV=c pion beams.The results of measurements of beam envelopes are presented.The rms size of the horizontal profile at the focus was 5-8 times smaller than at the exit of the crystals.The measured focal lengths were 4-21 m.The results of measurements are in good agreement with calculations.Possible applications of focusing crystals in present and future high energy accelerators are discussed.

Abstract The Serenity-S1 is a production-optimised Advanced Telecommunications Computing Architecture (ATCA) processing blade based on the AMD Xilinx Virtex Ultrascale+ device. It incorporates many developments from the Serenity-A and Serenity-Z prototype cards and, where possible, adopts solutions being used across CERN. Due to the shortage of components during the recent semiconductor crisis, commonly used components in the prototypes had to be replaced by new ones after qualification. In this work, we discuss various improvements to simplify manufacturing, the performance of new components, some of the more difficult aspects of procurement, the performance of production-grade Samtec 25 Gb/s optical firefly parts, and concerns regarding the rack cooling infrastructure.

The CBC2 is the latest version of the CMS Binary Chip ASIC for readout of the upgraded CMS Tracker at the High Luminosity LHC. It is designed in 130 nm CMOS with 254 input channels and will be bump-bonded to a substrate to which sensors will be wire-bonded. The CBC2 is designed to instrument double layer modules, consisting of two overlaid silicon microstrip sensors with aligned microstrips, in the outer tracker. It incorporates logic to identify L1 trigger primitives in the form of “stubs”: high transverse-momentum track candidates which are identified within the low momentum background by selecting correlated hits between two closely separated microstrip sensors. The first prototype modules have been assembled. The performance of the chip in recent laboratory tests is briefly reported and the status of module construction described.

A charged particle telescope has been deployed for data taking at high rates in a CERN beam line using protons and other particles. The apparatus has a baseline of approximately 10 m in each arm, and achieves an angular resolution of 5.4 μrad using 400 GeV/c protons. The electronic readout and data acquisition system is based on that developed for the CMS Tracker, and provides almost deadtime-free operation at trigger rates of up to about 10 kHz. The telescope was developed to characterize crystals used in channeling experiments with a primary objective to validate them for use in a future LHC beam collimation system. The telescope has also been used for other studies of fundamental phenomena associated with the channeling process. The telescope is described, and its measured performance, referring to results from channeling studies, including recent measurements in heavy ion beams.

Multiple scattering effects of 12 and 20 GeV electrons on 8 and 20 mm thickness carbon targets have been studied with high-resolution silicon microstrip detectors of the UA9 apparatus at the H8 line at CERN . Comparison of the scattering angle between data and GEANT4 simulation shows excellent agreement in the core of the distributions leaving some residual disagreement in the tails.

Abstract This work presents the development of an Intelligent Platform Management Controller mezzanine in a Mini DIMM form factor for use in electronic boards compliant to the PICMG Advanced Telecommunication Computing Architecture (ATCA) standard. The module is based on an STMicroelectronics STM32H745 microcontroller running the OpenIPMC open-source software. The mezzanine has been successfully tested on a variety of ATCA boards being proposed for the upgrade of the experiments at the HL-LHC, with its design and firmware being distributed under open-source hardware license.

The Super-LHC (SLHC) is a proposed Large Hadron Collider (LHC) accelerator upgrade to increase the machine luminosity by an order of magnitude to 1035cm-2s-1. The CMS experiment at the LHC is also planning an upgrade of its tracking system in expectation of this development. The increased particle fluxes and radiation environment will necessitate the complete replacement of the current CMS tracker while presenting the design of a new tracker with severe challenges. Power consumption is one of the main challenges for the tracker readout system since a higher granularity detector will be required. Physics performance must not be compromised so the tracker material contribution should be lowered where possible. In addition, it is likely that the Level 1 system will require information from the tracker in order to reduce the trigger rate. A method of reducing the on-detector data rate for input into a L1 trigger using closely separated pixel layers is presented. A detailed simulation of a concept tracker geometry has been developed and the triggering performance has been estimated. The simulations report that the presented tracking trigger layer would be viable for use at SLHC. A layer would be capable of reducing the detector data rate by a factor of ∼ 20 while maintaining a track finding efficiency in excess of 96% for tracks with pT > 2 GeV/c. The information provided by a single stacked layer would not be useful for reducing the L1 trigger rate, but two stacked layers could be used to reconstruct tracks with δpT/pT < 20% for pT < 20 GeV/c and with sufficient resolution so as to match tracks with L1 calorimeter objects.

The CMS Tracker under development for the High Luminosity LHC includes an outer tracker based on ``PT-modules'' which will provide track stubs based on coincident clusters in two closely spaced sensor layers, aiming to reject low transverse momentum track hits before data transmission to the Level-1 trigger. The tracker data will be used to reconstruct track segments in dedicated processors before onward transmission to other trigger processors which will combine tracker information with data originating from the calorimeter and muon detectors, to make the final L1 trigger decision. The architecture for processing the tracker data is still an open question. One attractive option is to explore a Time Multiplexed design similar to one which is currently being implemented in the CMS calorimeter trigger as part of the Phase I trigger upgrade. The Time Multiplexed Trigger concept is explained, the potential benefits of applying it for processing future tracker data are described and a possible design based on currently existing hardware is presented.

The effect of multiple volume reflections in one crystal was observed in each of several bent silicon strips for 400 GeV/c protons. This considerably increased the particle deflections. Some particles were also deflected due to channeling in one of the subsequent strips. As a result, the incident beam was strongly spread because of opposite directions of the deflections. A modified multi-strip deflector produced by periodic grooves on the surface of a thick silicon plate was used for these measurements. This technique provides perfect mutual alignment between crystal strips. Such multi-strip deflector may be effective for collider beam halo collimation and a study is planned at the CERN SPS circulating beam.

Inelastic nuclear interaction probability of 400 GeV/c protons interacting with bent silicon crystals was investigated, in particular for both types of crystals installed at the CERN Large Hadron Collider for beam collimation purposes. In comparison to amorphous scattering interaction, in planar channeling this probability is $$\sim 36\%$$ for the quasi-mosaic type (planes (111)), and $$\sim 27\%$$ for the strip type (planes (110)). Moreover, the absolute inelastic nuclear interaction probability in the axial channeling orientation, along the $$\langle 110\rangle $$ axis, was estimated for the first time, finding a value of $$0.6\%$$ for a crystal 2 mm long along the beam direction, with a bending angle of 55 $$\upmu $$ rad. This value is more than two times lower with respect to the planar channeling orientation of the same crystal, and increases with the vertical angular misalignment. Finally, the correlation between the inelastic nuclear interaction probability in the planar channeling and the silicon crystal curvature is reported.

We present the experimental observation of the reduction of multiple scattering of high-energy positively charged particles during channeling in single crystals. According to our measurements the rms angle of multiple scattering in the plane orthogonal to the plane of the channeling is less than half that for non-channeled particles moving in the same crystal. In the experiment we use focusing bent single crystals. Such crystals have a variable thickness in the direction of beam propagation. This allows us to measure rms angles of scattering as a function of thickness for channeled and non-channeled particles. The behaviour with thickness of non-channeled particles is in agreement with expectations whereas the behaviour of channeled particles has unexpected features. We give a semi-quantitative explanation of the observed effect.

A new tracking system is under development for operation in the CMS experiment at the High Luminosity LHC. It includes an outer tracker which will construct stubs, built by correlating clusters in two closely spaced sensor layers for the rejection of hits from low transverse momentum tracks, and transmit them off-detector at 40 MHz. If tracker data is to contribute to keeping the Level-1 trigger rate at around 750 kHz under increased luminosity, a crucial component of the upgrade will be the ability to identify tracks with transverse momentum above 3 GeV/c by building tracks out of stubs. A concept for an FPGA-based track finder using a fully time-multiplexed architecture is presented, where track candidates are identified using a projective binning algorithm based on the Hough Transform. A hardware system based on the MP7 MicroTCA processing card has been assembled, demonstrating a realistic slice of the track finder in order to help gauge the performance and requirements for a full system. This paper outlines the system architecture and algorithms employed, highlighting some of the first results from the hardware demonstrator and discusses the prospects and performance of the completed track finder.

At large accelerators, bent crystals are employed to deflect weakly divergent proton beams at the stages of extraction and collimation. We demonstrate that a divergent particle beam may be efficiently deflected using a crystal with a focusing entry face. A 180 GeV/c pion beam with divergence near 0.060 mrad, which exceeds the Lindhard angle by a factor of 4, has been experimentally deflected by 0.25 mrad with efficiency near 22%. The proposed focusing crystal may serve as an element of a novel particle optics for secondary-particle beams in the TeV energy region.

Abstract In the context of the CMS Phase-2 tracker back-end processing system, two mezzanines based on the Zynq Ultrascale+ Multi-Processor System-on-Chip (MPSoC) device have been developed to serve as centralized slow control and board management solution for the Serenity-family Advanced Telecommunications Computing Architecture (ATCA) blades. This paper presents the developments of the MPSoC mezzanines to execute the Intelligent Platform Management Controller (IPMC) software in the real-time capable processors of the MPSoC. In coordination with the Shelf Manager, once full-power is enabled, a CentOS-based Linux distribution is executed in the application processors of the MPSoC, on which EMPButler and the Serenity Management Shell (SMASH) are running.

We present the results of an experimental study of multiple scattering of positively charged high energy particles in bent samples of monocrystalline silicon. This work confirms the recently discovered effect of a strong reduction in the rms multiple scattering angle of particles channeled in the silicon (111) plane. The effect is observed in the plane orthogonal to the bending plane. We show in detail the influence of angular constraints on the magnitude of the effect. Comparison of the multiple scattering process at different energies indicates a violation of the law of inverse proportionality of the rms angle of channeled particles with energy. By increasing the statistics, we have improved the results of multiple scattering measurements for particles moving, but not channeled, in silicon crystals.

Abstract A vertical slice of the CMS Outer Tracker has been tested at the tracker integration facility and at the M2 muon beam facility at CERN. It includes the final prototype of the 2S module with an optical link to the back-end ATCA system. The performance of the system will be described, including cooling limits of racks, robustness of 25 Gbit/s trigger optical links, and readiness of firmware.

The CMS Binary Chip (CBC) is designed for readout of silicon microstrips in the CMS Tracker at the High Luminosity LHC (HL-LHC). Binary, unsparsified readout is well suited to the high luminosity environment, where particle fluences and data rates will be much higher than at the LHC. In September 2011, a module comprising a CBC bonded to a silicon microstrip sensor was tested with 400 GeV protons in the H8 beamline at CERN. Performance was in agreement with expectations. The spatial resolution of the sensor and CBC has been shown to be better than pitch/√12 due to spatial distribution of one and two strip clusters. Large cluster events show consistency with the production of delta rays. At operating thresholds, the hit efficiency has been shown to be approximately 98%, limited by the resolution of timing apparatus, while the noise occupancy is measured to be below 10−4. The distribution of charge deposition in the sensor has been reconstructed by measurement of the hit efficiency as a function of comparator threshold; assuming the underlying distribution is a Landau.

The CMS Binary Chip 2 (CBC2) is a full-scale prototype ASIC developed for the front-end readout of the high-luminosity upgrade of the CMS silicon strip tracker.The 254-channel, 130 nm CMOS ASIC is designed for the binary readout of double-layer modules, and features cluster-width discrimination and coincidence logic for detecting high-P T track candidates.The chip was delivered in January 2013 and has since been bump-bonded to a dual-chip hybrid and extensively tested.The CBC2 is fully functional and working to specification: we present the result of electrical characterization of the chip, including gain, noise, threshold scan and power consumption, together with the performance of the stub finding logic.Finally we will outline the plan for future developments towards the production version.

The ordered positions of atoms in crystals give a reason to study multiple Coulomb scattering of high energy charged particles within them. In addition, the accurate representation of multiple scattering of high energy protons in a bent crystal is important for studies of crystal assisted collimation at the SPS and the LHC. Multiple scattering of 400 GeV/c protons in bent silicon crystals was measured for orientations far from the directions of main crystallographic planes and axes in conditions excluding channeling of protons. The observed RMS widths of the angular distributions are a little larger than those obtained from the Moliere theory. Simulation of multiple scattering in a model of binary collisions with the crystal atoms shows about 3.5% decrease of the RMS deflection with respect to the model of a sequence of random collisions. We consider this as a possible indication of a reduction of multiple scattering of protons in a crystal in comparison with its amorphous state.

The CBC3 is the latest version of the CMS Binary Chip ASIC for readout of the outer radial region of the upgraded CMS Tracker at HL-LHC.This 254-channel, 130nm CMOS ASIC is designed to be bump-bonded to a substrate to which sensors will be wire-bonded.It will instrument double-layer 2S-modules, consisting of two overlaid silicon microstrip sensors with aligned microstrips.On-chip logic identifies first level trigger primitives from high transversemomentum tracks by selecting correlated hits in the two sensors.Delivered in late 2016, the CBC3 has been under test for several months, including X-ray irradiations and SEU testing.Results and performance are reported.

Experimental results on deflection of a 180 GeV/c π+-meson beam by a 23 mm long bent silicon crystal are analyzed to study the dechanneling process of particles due to multiple scattering. A new approach for the determination of contributions from atomic nuclei and electrons to the multiple scattering using the experimental data for random crystal orientations is suggested. The results of simulations performed using this approach, in which the contribution from atomic electrons is considered according to the prescription of Bethe, are in a good agreement with the experiment.

Strong reduction of multiple scattering for channeled particles has been observed in an experiment on the deflection of a 180 GeV/c π+-meson beam by bent silicon crystals. The RMS deflections due to multiple scattering for the channeled particles were about six times smaller than for non-channeled ones. It was shown that the approach suggested recently for the description of multiple scattering for channeled particles using the experimental data for random crystal orientations gives fair agreement with the experiment.

Deflection of 400 GeV/c protons by a short bent silicon crystal was studied at the CERN SPS. It was shown that the dechanneling probability increases while the dechanneling length decreases with an increase of incident angles of particles relative to the crystal planes. The observation of the dechanneling length reduction provides evidence of the particle population increase at the top levels of transverse energies in the potential well of the planar channels.

Abstract The rate of inelastic nuclear interactions in a short bent silicon crystal was precisely measured for the first time using a 180 GeV/c positive hadron beam produced in the North Experimental Area of the CERN SPS. An angular asymmetry dependence on the crystal orientation in the vicinity of the planar channeling minimum has been observed. For the inspected crystal, this probability is about $$\sim 20\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>∼</mml:mo><mml:mn>20</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:math> larger than in the amorphous case because of the atomic density increase along the particle trajectories in the angular range of volume reflection, whose dimension is determined by the crystal bending angle. Instead, for the opposite angular orientation with respect to the planar channeling, there is a smaller probability excess of $$\sim 4\%$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>∼</mml:mo><mml:mn>4</mml:mn><mml:mo>%</mml:mo></mml:mrow></mml:math> .

The CBC3 is the latest version of the CMS Binary Chip for readout of the outer radial region of the upgraded CMS Tracker at the High Luminosity LHC. This 254-channel, 130 nm CMOS ASIC is designed to be bump-bonded to a substrate to which sensors will be wire-bonded. It will instrument double-layer 2S-modules, containing two overlaid silicon microstrip sensors, aligned with a parallel orientation. On-chip logic identifies Level-1 trigger primitives from high transverse-momentum tracks by selecting correlated clusters in the two sensors. The CBC3 was delivered in late 2016; wafer probing and performance tests have been carried out. Several prototype modules using the CBC3 have been produced and tested in the lab and in different beams. The results show that the CBC3 satisfies CMS requirements and only small corrections are needed for the final version of the chip for production.

The UA9 setup, installed in the Super Proton Synchrotron (SPS) at CERN, was exploited for a proof of principle of the double-crystal scenario, proposed to measure the electric and the magnetic moments of short-lived baryons in a high-energy hadron collider, such as the Large Hadron Collider (LHC). Linear and angular actuators were used to position the crystals and establish the required beam configuration. Timepix detectors and high-sensitivity Beam Loss Monitors were exploited to observe the deflected beams. Linear and angular scans allowed exploring the particle interactions with the two crystals and recording their efficiency. The measured values of the beam trajectories, profiles and of the channeling efficiency agree with the results of a Monte-Carlo simulation.

Abstract Beam steering performance of bent silicon crystals irradiated with high-intensity and high-energy protons has been studied. In particular, crystals of the type used for collimation and extraction purposes in the Large Hadron Collider and the Super Proton Synchrotron at CERN have been irradiated at the HiRadMat CERN facility with $$2.5 \times 10^{13}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>2.5</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>13</mml:mn></mml:msup></mml:mrow></mml:math> 440 GeV/c protons, with a pulse length of 7.2 $$\upmu $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>μ</mml:mi></mml:math> s. The purpose is to study possible changes in bending angle and channeling efficiency due to thermo-mechanical stresses in case of accidental irradiation during accelerator operations. A comparison between measurements performed before and after the irradiation does not show any appreciable performance reduction in either crystal.

In view of possible future fixed target experiments requiring precisely steered charged particle beams, the UA9 Collaboration has undertaken experimental studies of the use of bent silicon crystals for this purpose. The channeling efficiency of positively charged particles inside the crystalline lattice has been investigated in detail for a setup with a tungsten target installed in front of the crystal. Due to multiple Coulomb scattering inside the target, the channeling efficiency was observed to be reduced by a factor of about 6.1 for a 180 GeV/c quasi-parallel hadron beam. The yield of nuclear interaction secondaries as an estimation of the additional machine background is also discussed.

Experiments to measure the electric and the magnetic moments of short-lived baryons using an internal target and two bent crystals in the vicinity of one of the existing LHC detectors were recently proposed, in the frame of the Physics Beyond Colliders Working Group at CERN. Investigating fixed-target physics in the LHC with in-vacuum solid targets is an unprecedented challenge. As a preparatory step, the layout of the UA9 experiment, installed in the CERN SPS to explore beam manipulations assisted by bent crystals, has been modified to study the feasibility of the double-crystal scenario in a circular accelerator. Ideally, the first crystal should capture halo protons in channeling states directing them onto the internal target to produce rare baryons, whilst the second crystal, located just downstream of the target, should channel the baryons, rotate their polarization vector and deflect them towards the detector area. The upgraded UA9 layout is presented. Preliminary measurements providing an insight of the beam behavior are reported.

The High Luminosity LHC (HL-LHC) will deliver luminosities of up to 5 × 1034 Hz/cm2, with an average of about 140 overlapping proton-proton collisions per bunch crossing. These extreme pileup conditions place stringent requirements on the trigger system to be able to cope with the resulting event rates. A key component of the CMS upgrade for HL-LHC is a track trigger system which would identify tracks with transverse momentum above 2 GeV/c already at the first-level trigger. This paper presents the status of proposals for implementing the L1 tracking in conjunction with the planned upgrade for the silicon tracker of the CMS experiment.

The subsystems of the CMS silicon strip tracker were integrated and commissioned at the Tracker Integration Facility (TIF) in the period from November 2006 to July 2007. As part of the commissioning, large samples of cosmic ray data were recorded under various running conditions in the absence of a magnetic field. Cosmic rays detected by scintillation counters were used to trigger the readout of up to 15\,\% of the final silicon strip detector, and over 4.7~million events were recorded. This document describes the cosmic track reconstruction and presents results on the performance of track and hit reconstruction as from dedicated analyses.

The Compact Muon Solenoid (CMS) experiment at CERN is scheduled for a major upgrade in the next decade in order to meet the demands of the new High Luminosity Large Hadron Collider.Amongst others, a new tracking system is under development including an outer tracker capable of rejecting low transverse momentum particles by looking at the coincidences of hits (stubs) in two closely spaced sensor layers in the same tracker module.Accepted stubs are transmitted off-detector for further processing at 40 MHz.In order to maintain under the increased luminosity the Level-1 trigger rate at 750 kHz, tracker data need to be included in the decision making process.For this purpose, a system architecture has to be developed that will be able to identify particles with transverse momentum above 3 GeV/c by building tracks out of stubs, while achieving an overall processing latency of maximum 4us.Targeting these requirements the current paper presents an FPGA-based track finding architecture that identifies track candidates in real-time and bases its functionality on a fully time-multiplexed approach.As a proof of concept, a hardware system has been assembled targeting the MP7 MicroTCA processing card that features a Xilinx Virtex-7 FPGA, demonstrating a realistic slice of the track finder.The paper discusses the algorithms' implementation and the efficient utilisation of the available FPGA resources, it outlines the system architecture, and presents some of the hardware demonstrator results.

Recent discussions about accelerators in high energy physics identified several challenges for the future, where it is necessary to focus particle beams over a distance of a few cm. In this paper, we investigate the focusing of particles by a new crystal device having such a capability. The trajectories of 180 GeV/c pions passing through a 500 µm thick focusing crystal were reconstructed using silicon microstrip detectors. It is shown that a parallel beam of particles can be focused in one plane at a distance of 15.5 cm from the crystal, in a narrow line with an rms width of 8 µm.

At the HL-LHC, proton bunches will cross each other every 25 ns, producing an average of 140 pp-collisions per bunch crossing. To operate in such an environment, the CMS experiment will need a L1 hardware trigger able to identify interesting events within a latency of 12.5 μs. The future L1 trigger will make use also of data coming from the silicon tracker to control the trigger rate. The architecture that will be used in future to process tracker data is still under discussion. One interesting proposal makes use of the Time Multiplexed Trigger concept, already implemented in the CMS calorimeter trigger for the Phase I trigger upgrade. The proposed track finding algorithm is based on the Hough Transform method. The algorithm has been tested using simulated pp-collision data. Results show a very good tracking efficiency. The algorithm will be demonstrated in hardware in the coming months using the MP7, which is a μTCA board with a powerful FPGA capable of handling data rates approaching 1 Tb/s.

The Super-LHC (SLHC) is a proposed Large Hadron Collider (LHC) accelerator upgrade to increase the machine luminosity by an order of magnitude to 10 35 cm -2 s -1 .The increased particle fluxes and years of radiation damage means that the Compact Muon Solenoid (CMS) experiment at the LHC will have to replace its entire tracking system in expectation of this.Power consumption is a significant challenge in the design of a future tracker readout system due to requirement for a higher granularity detector.Physics performance must not be compromised so the tracker material contribution should be lowered where possible.It will also be necessary for the tracker to provide some information to the Level 1 system in order to maintain the trigger rate below a maximum of 100 kHz.A method of reducing the on-detector data rate for input into a L1 trigger using closely separated ("stacked") pixel layers is presented.Detailed simulations report that a tracking trigger layer would be viable for use at SLHC, reducing the detector data rate by a factor of ∼20 while maintaining a track finding efficiency in excess of 96% for tracks with p T >2 GeV/c.Two or more stacked layers could be used to reconstruct tracks with δ p T /p T < 20% for p T <20 GeV/c and with sufficient resolution so as to match tracks with L1 calorimeter objects.Recent progress on stacked module R&D, trigger simulations and concept designs is presented.

Abstract Bunch merging is a well-established technique to increase the intensity of synchrotrons and the luminosity of circular colliders. We suggest to exploit a combination of channeling, volume reflection and amorphous interactions in a bent crystal for beam merging in a transfer line. Two beams converging into the bent crystal along special directions should emerge in almost parallel directions. A merging scenario is discussed, and data collected by the UA9 Collaboration are reprocessed to prove its feasibility. Comparison with magnetic stacking, which is a similar process, is presented.

The Serenity-S1 is a Xilinx Virtex Ultrascale+ based Advanced Telecommunications Computing Architecture (ATCA) processing blade that has been optimised for production. It incorporates many developments from the Serenity-A and Serenity-Z prototype cards and, where possible, adopts solutions being used across CERN. It also uses many new parts because commonly used parts have disappeared from the market during the semiconductor crisis, with only some returning. Improvements to simplify manufacture, the performance of new components, some of the more difficult aspects of procurement, the performance of production-grade Samtec 25\,Gb/s optical firefly parts, and issues with the rack cooling infrastructure are discussed.

A charged particle telescope based on silicon microstrip sensors has been used for several years for data taking at high rates in the CERN H8 beam line using a range of different incident particles. The electronic readout and data acquisition system is based on that developed for the CMS Tracker, and provides almost deadtime-free operation at trigger rates of up to about 10 kHz. The telescope was designed to characterise crystals in channeling studies by the UA9 experiment with the primary objective to validate them for use in a future LHC beam collimation system, hence is optimised for measurement of a single particle in the outgoing arm. The telescope has also been used for other studies of fundamental phenomena associated with the channeling process and further LHC applications. Some of these require a different layout of the telescope, for example to achieve a larger angular acceptance to study longer channeling crystals, or modifications to sensor operating conditions because of the very large electric charge and consequent ionisation energy loss associated with heavy ions. The telescope and its performance are described. Possible improvements are discussed.

Abstract The possibility to deflect hadron beams precisely through angles of multi-mrad is important for several future applications, and magnets are not suitable for this purpose. Crystal channeling provides a means to do this, but is not well studied for such deflections. Measurements of the interactions of charged particles with several cm long crystals with large bending have been obtained by the UA9 collaboration. These crystals have a bending 100 times larger and a length along the beam direction up to 40 times longer than the ones presently used by UA9 in the CERN accelerators. To assess their properties and quality, the crystals have been investigated in the CERN North Area with a Super Proton Synchrotron beam of mixed hadrons at 180 GeV. The UA9 tracking telescope has been adapted to collect data with these particular crystals. A new track reconstruction method is described which was required to obtain the results reported, and has been used in the present study to validate the methodology, so that detailed assessments of future systems can be made.

Abstract The channeling process in bent silicon crystals are used since '70s to manipulate beams of high energy particles. During the last decade, several studies and experiments carried out by the UA9 Collaboration at CERN demonstrated the possibility to use bent crystals for beam collimation, extraction, focusing and splitting in particle accelerators. These crystals are subject to deterioration due to the interaction of the particles with the crystal lattice, degrading the beam steering performance. For this reason, robustness tests are crucial to estimate their reliability and operational lifetime. A ∼8% of reduction in channeling efficiency on crystals irradiated with 2.5·10 21 /cm 2 thermal neutrons was measured and reported in this manuscript. Extrapolations to possible operational scenarios in high energy accelerators are also discussed.

The CMS collaboration is preparing a major upgrade of its detector, so it can operate during the high luminosity run of the LHC from 2026. The upgraded tracker electronics will reconstruct the trajectories of charged particles within a latency of a few microseconds, so that they can be used by the level-1 trigger. An emulation framework, CIDAF, has been developed to provide a reference for a proposed FPGA-based implementation of this track finder, which employs a Time-Multiplexed (TM) technique for data processing.

W. Scandale a,b,e, F. Andrisani a, G. Arduini a, M. Butcher a, F. Cerutti a, M. Garattini a, S. Gilardoni a, A. Lechner a, R. Losito a, A. Masi a, A. Mereghetti a, E. Metral a, D. Mirarchi a,j, S. Montesano a, S. Redaelli a, R. Rossi a,e, P. Schoofs a, G. Smirnov a, E. Bagli c, L. Bandiera c, S. Baricordi c, P. Dalpiaz c, G. Germogli c, V. Guidi c, A. Mazzolari c, D. Vincenzi c, G. Claps d, S. Dabagov d,k,l, D. Hampai d, F. Murtas d, G. Cavoto e, F. Iacoangeli e, L. Ludovici e, R. Santacesaria e, P. Valente e, F. Galluccio f, A.G. Afonin g, Yu.A. Chesnokov g, A.A. Durumg, V.A. Maisheev g, Yu.E. Sandomirskiy g, A.A. Yanovich g, A.D. Kovalenko h, A.M. Taratin h,∗, Yu.A. Gavrikov i, Yu.M. Ivanov i, L.P. Lapina i, J. Fulcher j, G. Hall j, M. Pesaresi j, M. Raymond j

The feasibility of crystal-assisted collimation is being investigated for improvements of the LHC collimation system, for possible implementation in the future high luminosity upgrade of the CERN LHC (HL-LHC).Two high-accuracy goniometers, each equipped with one bent silicon crystal, were installed in the betatron cleaning insertion of the LHC in 2014.During dedicated tests in 2015, bent crystals were approached to the circulating beams to test their usage as a first stage in a crystal-based collimation system, both with proton and Pb ion beams.Tests were performed with protons at injection energy (450 GeV) and at flat top (6.5 TeV), and with ions at injection energy (450 Z GeV).A reduction of losses immediately downstream of the crystals was observed in optimum channeling orientation, demonstrating for the first time particle channeling at these energies.

A new tracking detector is under development for use by the CMS experiment at the High-Luminosity LHC (HL-LHC).A crucial component of this upgrade will be the ability to reconstruct within a few microseconds all charged particle tracks with transverse momentum above 3 GeV, so they can be used in the Level-1 trigger decision.A concept for an FPGA-based track finder using a fully time-multiplexed architecture is presented, where track candidates are reconstructed using a projective binning algorithm based on the Hough Transform followed by a track fitting based on the linear regression technique.A hardware demonstrator using MP7 processing boards has been assembled to prove the entire system, from the output of the tracker readout boards to the reconstruction of tracks with fitted helix parameters.It successfully operates on one eighth of the tracker solid angle at a time, processing events taken at 40 MHz, each with up to 200 superimposed proton-proton interactions, whilst satisfying latency constraints.The demonstrated track-reconstruction system, the chosen architecture, the achievements to date and future options for such a system will be discussed.

In this paper, we discuss an experimental layout for the two-crystals scenario at the Super Proton Synchrotron (SPS) accelerator. The research focuses on a fixed target setup at the circulating machine in a frame of the Physics Beyond Colliders (PBC) project at CERN. The UA9 experiment at the SPS serves as a testbench for the proof of concept, which is planning to be projected onto the Large Hadron Collider (LHC) scale. The presented in the text configuration was used for the quantitative characterization of the deflected particle beam by a pair of bent silicon crystals. For the first time in the double-crystal configuration, a particle deflection efficiency by the second crystal of $0.188 \pm 3 \cdot 10^{-5}$ and $0.179 \pm 0.013$ was measured on the accelerator by means of the Timepix detector and Beam Loss Monitor (BLM) respectively. In this setup, a wide range angular scan allowed a possibility to \textit{in situ} investigate different crystal working regimes (channeling, volume reflection, etc.), and to measure a bent crystal torsion.

The CMS Silicon Strip Tracker front-end readout system utilises 73,000 APV25 ASICs to provide low noise signal amplification, analogue buffering and proc essing in a harsh radiation environment on-detector and 440 Front End Drivers (FEDs) to digitise, buffer and process the signals offdetector so that the data rate is reduced. The APV buffers cannot be monitored directly on-detector so an APV Emulator (APVE) has been designed and built to calculate the exact buffer occupancies of the APV25s for preventing buffer overflows. The APVE is als o able to provide information to the FEDs in order to check that synchronisation between the APVE and the APV25s has been maintained. The majority of the authors work concerns the commisioning of the APVE within the final Data Acquisition (DAQ) System. The APVE has been fully tested and integration with the tracker readout and DAQ is almost complete. The author has written an application based on the integrated CMS DAQ framework (XDAQ) for the purpose of monitoring the APVE during the testing and operational phases of the CMS detector.

The CMS Silicon Tracker comprises a complicated set of hardware and software components that have been thoroughly tested at CERN before final integration of the Tracker. A vertical slice of the full readout chain has been operated under near-final conditions. In the absence of the tracker front-end modules, simulated events have been created within the FED (Front End Driver) and used to test the readout reliability and efficiency of the final DAQ (Data Acquisition). The data are sent over the S-Link 64 bit links to the FRL (Fast Readout Link) modules at rates in excess of 200 MBytes/s per FED depending on setup and conditions. The current tracker DAQ is fully based on the CMS communication and acquisition tool XDAQ. This paper discusses setup and results of a vertical slice of the full Tracker final readout system comprising 2 full crates of FEDs, 30 in total, read out through 1 full crate of final FRL modules. This test is to complement previous tests done at Imperial College[3] taking them to the next level in order to prove that a complete crate of FRLs using the final DAQ system, including all subcomponents of the final system both software and hardware with the exception of the detector modules themselves, is capable of sustained readout at the desired rates and occupancy of the CMS Tracker. Simulated data are created with varying hit occupancy (1-10%) and Poisson distributed trigger rates (<200KHz) and the resulting behaviour of the system is recorded. Data illustrating the performance of the system and data readout are presented.