R. Potenza

The RD48 (ROSE) collaboration has succeeded to develop radiation hard silicon detectors, capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach this objective, a defect engineering technique was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ), ensuring the necessary O-enrichment of about 2×1017 O/cm3 in the normal detector processing. Systematic investigations have been carried out on various standard and oxygenated silicon diodes with neutron, proton and pion irradiation up to a fluence of 5×1014 cm−2 (1 MeV neutron equivalent). Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too and the appreciable benefits obtained with DOFZ silicon in radiation tolerance for charged hadrons are outlined. The results are reliably described by the “Hamburg model”: its application to LHC experimental conditions is shown, demonstrating the superiority of the defect engineered silicon. Microscopic aspects of damage effects are also discussed, including differences due to charged and neutral hadron irradiation.

Using reverse kinematics, we have studied the breakup of 1.0A GeV gold nuclei incident on a carbon target. The detector system permitted exclusive event reconstruction of nearly all charged reaction products. The moments of the resulting charged fragment distribution provide strong evidence that nuclear matter possesses a critical point observable in finite nuclei. We have determined values for the critical exponents γ, β, and τ. These values are close to those for liquid-gas systems and clearly different than those for 3D percolation and the liquid-gas mean field limit.Received 20 May 1994DOI:https://doi.org/10.1103/PhysRevLett.73.1590©1994 American Physical Society

An exclusive study of the interaction of 1A GeV Au with C shows a separability into two stages: a prompt stage involving emission of most Z=1 and some Z=2 particles and a second stage involving the decay of an equilibrated remnant, which typically undergoes multifragmentation. The mean mass, charge, excitation energy, and the initial temperature Ti of the remnant have been determined as a function of the total charge multiplicity, m, as has the freeze-out temperature Tf. Both Ti and Tf increase linearly with m and their values at the critical point have been determined. Tf rises monotonically with excitation energy as expected for a continuous phase transition.Received 15 March 1996DOI:https://doi.org/10.1103/PhysRevLett.77.235©1996 American Physical Society

Exclusive measurements have been made of Au +Au reactions with beam energies ranging from 0.25 A to 1.15 A GeV. We present measurements of directed collective flow averaged over all light fragments with masses up to alphas, as well as separate measurements for protons, deuterons, tritons, 3He, 4He, and Li. The results show a strong increase of the directed flow with fragment mass at all energies measured. Experimental results are compared with a quantum molecular dynamics model. We find that neither the "soft" nor the "hard" equation of state can describe the data over the entire range of beam energies.Received 27 October 1994DOI:https://doi.org/10.1103/PhysRevLett.75.2100©1995 American Physical Society

This report summarises the final results obtained by the RD48 collaboration. The emphasis is on the more practical aspects directly relevant for LHC applications. The report is based on the comprehensive survey given in the 1999 status report (RD48 3rd Status Report, CERN/LHCC 2000-009, December 1999), a recent conference report (Lindström et al. (RD48), and some latest experimental results. Additional data have been reported in the last ROSE workshop (5th ROSE workshop, CERN, CERN/LEB 2000-005). A compilation of all RD48 internal reports and a full publication list can be found on the RD48 homepage (http://cern.ch/RD48/). The success of the oxygen enrichment of FZ-silicon as a highly powerful defect engineering technique and its optimisation with various commercial manufacturers are reported. The focus is on the changes of the effective doping concentration (depletion voltage). The RD48 model for the dependence of radiation effects on fluence, temperature and operational time is verified; projections to operational scenarios for main LHC experiments demonstrate vital benefits. Progress in the microscopic understanding of damage effects as well as the application of defect kinetics models and device modelling for the prediction of the macroscopic behaviour has also been achieved but will not be covered in detail.

A systematic study of energy spectra for light particles emitted at midrapidity from Au+Au collisions at E=0.25-1.15A GeV reveals a significant non-thermal component consistent with a collective radial flow.This component is evaluated as a function of bombarding energy and event centrality.Comparisons to Quantum Molecular Dynamics (QMD) and Boltzmann-Uehling-Uhlenbeck (BUU) models are made for different equations of state.

Progress in experimental particle physics in the coming decade depends crucially upon the ability to carry out experiments in high-radiation areas. In order to perform these complex and expensive experiments, new radiation hard technologies must be developed. This paper discusses the use of diamond detectors in future tracking applications and their survivability in the highest radiation environments. We present results of devices constructed with the newest polycrystalline and single crystal Chemical Vapor Deposition diamond and their tolerance to radiation.

Beam test results of the radiation tolerance study of chemical vapour deposition (CVD) diamond against different particle species and energies is presented. We also present beam test results on the independence of signal size on incident particle rate in charged particle detectors based on un-irradiated and irradiated poly-crystalline CVD diamond over a range of particle fluxes from 2 kHz/cm2 to 10 MHz/cm2. The pulse height of the sensors was measured with readout electronics with a peaking time of 6 ns. In addition functionality of poly-crystalline CVD diamond 3D devices was demonstrated in beam tests and 3D diamond detectors are shown to be a promising technology for applications in future high luminosity experiments.

Multifragmentation MF results from 1AGeV Au on C have been compared with the Copenhagen statistical multifragmentation model (SMM). The complete charge, mass, and momentum reconstruction of the Au projectile was used to identify high momentum ejectiles leaving an excited remnant of mass A, charge Z, and excitation energy E* which subsequently multifragments. Measurement of the magnitude and multiplicity (energy) dependence of the initial free volume and the breakup volume determines the variable volume parametrization of SMM. Very good agreement is obtained using SMM with the standard values of the SMM parameters. A large number of observables, including the fragment charge yield distributions, fragment multiplicity distributions, caloric curve, critical exponents, and the critical scaling function are explored in this comparison. The two stage structure of SMM is used to determine the effect of cooling of the primary hot fragments. Average fragment yields with Z>~3 are essentially unaffected when the excitation energy is ⩽7 MeV/nucleon. SMM studies suggest that the experimental critical exponents are largely unaffected by cooling and event mixing. The nature of the phase transition in SMM is studied as a function of the remnant mass and charge using the microcanonical equation of state. For light remnants A<~100, backbending is observed indicating negative specific heat, while for A>~170 the effective latent heat approaches zero. Thus for heavier systems this transition can be identified as a continuous thermal phase transition where a large nucleus breaks up into a number of smaller nuclei with only a minimal release of constituent nucleons. Z<~2 particles are primarily emitted in the initial collision and after MF in the fragment deexcitation process.Received 7 June 2000DOI:https://doi.org/10.1103/PhysRevC.64.054602©2001 American Physical Society

A high-statistics exclusive study of the multifragmentation of 1A GeV gold on carbon has been performed. Particles with Z<~2 show evidence of emission in a first prompt stage as well as in a second equilibrium stage whereas fragments with Z>~3 appear to be emitted essentially only in the second stage. Two methods for the separation of the Z<~2 particles into the two stages are given and they are in agreement. The yields for each stage are determined as a function of the event charged particle multiplicity m. The mass, nuclear charge, excitation energy per nucleon, and temperature of the remnant left after the first stage and their fluctuations have been determined as a function of m. The expansion of the remnant to fragment freeze-out is examined. The freeze-out temperature is determined from double isotope ratios as a function of m and isentropic trajectories are obtained in the temperature-density plane. The caloric curve shows a monotonic increase with excitation energy. Some of the energy is in the form of radial flow. Overall, the results are consistent with a previous statistical analysis of the data which suggests that, over a certain range of excitation energies, multifragmentation involves a continuous phase transition.Received 14 July 1997DOI:https://doi.org/10.1103/PhysRevC.57.764©1998 American Physical Society

E896 has measured Lambda production in 11.6A GeV/c Au-Au collisions over virtually the whole rapidity phase space. The midrapidity p(t) distributions have been measured for the first time at this energy and appear to indicate that the Lambda hyperons have different freeze-out conditions than protons. A comparison with the relativistic quantum molecular dynamics model shows that while there is good shape agreement at high rapidity the model predicts significantly different slopes of the m(t) spectra at midrapidity. The data, where overlap occurs, are consistent with previously reported measurements.

The interaction of neutrons in the energy range 2.5 to 5 MeV in aluminium is studied by measuring the total cross section and the reaction cross sections for the (n,p) process and for the fast neutron radiative capture. Measurements are made in steps of about 25 keV for the total cross section and of about 50 keV for the (n, p) and (n,γ) cross sections with a neutron energy spread of about 50 keV in both cases. The structures of the cross sections are interpreted as due to statistical fluctuations of the level density of the Al28 intermediate nucleus. An estimate of an effective Al28 level density at an excitation energy E = 12.5 MeV is obtained from the fluctuations of the cross sections; the fit with the theoretical predictions is discussed.

This paper reports the elemental production cross sections for 17 projectile-energy combinations with energies between 338 and 894 MeV/nucleon interacting in a liquid hydrogen target. These results were obtained from two runs at the LBL Bevalac using projectiles ranging from $^{22}\mathrm{Ne}$ to $^{58}\mathrm{Ni}$. Cross sections were measured for all fragment elements with charges greater than or equal to half the charge of the projectile. The results show that, over the energy and ion range investigated, the general decrease in cross section with decreasing fragment charge is strongly modified by the isospin of the projectile ion. Significant additional modifications of the cross sections due to the internal structure of the nucleus have also been seen. These include both pairing and shell effects. Differences in the cross sections due to the differing energies of the projectile are also considerable. \textcopyright{} 1996 The American Physical Society.

The fragment yields from the multifragmentation of gold, lanthanum, and krypton nuclei obtained by the EOS Collaboration are examined in terms of Fisher’s droplet formalism modified to account for Coulomb energy. The critical exponents σ and τ and the surface energy coefficient c0 are obtained. Estimates are made of the pressure-temperature and temperature-density coexistence curve of finite neutral nuclear matter as well as the location of the critical point.Received 7 May 2002DOI:https://doi.org/10.1103/PhysRevC.67.024609©2003 American Physical Society

A liquid hydrogen target was used to study the nuclear fragmentation of beams of relativistic heavy ions, 22Ne to 58Ni, over an energy range 400 to 900 MeV/nucleon. The experiments were carried out at the Lawrence Berkeley Laboratory Bevalac HISS facility, using the charge-velocity-rigidity method to identify the charged fragments. Here we describe the general concept of the experiment and present total charge-changing cross sections obtained from 17 separate runs. These new measured cross sections display an energy dependence which follows semiempirical model predictions. The mass dependence of the cross sections behaves as predicted by optical models, but within the experimental energy range, the optical model parameters display a clear energy dependence. The isospin of the projectile nuclei also appears to be an important factor in the interaction process.Received 19 November 1993DOI:https://doi.org/10.1103/PhysRevC.49.3200©1994 American Physical Society

With the commissioning of the LHC in 2010 and upgrades expected in 2015, ATLAS and CMS are planning to upgrade their innermost tracking layers with radiation hard technologies. Chemical Vapor Deposition diamond has been used extensively in beam conditions monitors as the innermost detectors in the highest radiation areas of BaBar, Belle, CDF and all LHC experiments. This material is now being considered as a sensor material for use very close to the interaction region where the most extreme radiation conditions exist. Recently the RD42 collaboration constructed, irradiated and tested polycrystalline and single-crystal chemical vapor deposition diamond sensors to the highest fluences expected at the super-LHC. We present beam test results of chemical vapor deposition diamond up to fluences of 1.8×1016 protons/cm2 illustrating that both polycrystalline and single-crystal chemical vapor deposition diamonds follow a single damage curve. We also present beam test results of irradiated complete diamond pixel modules.

The cluster distributions of different systems are examined to search for signatures of a continuous phase transition. In a system known to possess such a phase transition, both sensitive and insensitive signatures are present; while in systems known not to possess such a phase transition, only insensitive signatures are present. It is shown that nuclear multifragmentation results in cluster distributions belonging to the former category, suggesting that the fragments are the result of a continuous phase transition.

Multifragmentation in fully reconstructed events from 1A GeV Kr and La collisions with C has been studied. Results are compared with similar data for 1A GeV Au+C. The emitted charged particles and fragments are identified with emission from either a prompt first stage or a second stage in which the remnant resulting from the first stage breaks up. The nuclear charge, mass, and excitation energy distributions of the remnant are determined. The total charged multiplicity, as well as those of the first and second stages are obtained. Freeze-out temperatures and thermal excitation energy permit the determination of the caloric curve. The fragment charge distribution as well as the IMF multiplicity distribution and those of individual fragments are obtained. The various results are examined as to the extent of universal behavior when scaled for varying system size. Comparisons are made with intranuclear cascade and statistical multifragmentation model calculations.Received 23 February 2000DOI:https://doi.org/10.1103/PhysRevC.62.024616©2000 American Physical Society

Using charged-particle-exclusive measurements of Au+Au collisions in the LBL Bevalac's EOS time projection chamber, we investigate momentum-space densities of fragments up to 4He as a function of fragment transverse momentum, azimuth relative to the reaction plane, rapidity, multiplicity, and beam energy. Most features of these densities above a transverse momentum threshold are consistent with momentum-space coalescence, and, in particular, the increase in sideward flow with fragment mass is generally well described by a momentum-space power law.Received 29 August 1994DOI:https://doi.org/10.1103/PhysRevLett.74.2646©1995 American Physical Society

Chemical vapor deposition diamond has been discussed extensively as an alternate sensor material for use very close to the interaction region of the LHC where extreme radiation conditions exist. During the last few years diamond devices have been manufactured and tested with LHC electronics with the goal of creating a detector usable by all LHC experiment. Extensive progress on diamond quality, on the development of diamond trackers and on radiation hardness studies has been made. Transforming the technology to the LHC specific requirements is now underway. In this paper we present the recent progress achieved.

Invariant mass analyses of (p,{pi}{sup {plus_minus}}) pairs in {sup 58}Ni+Cu collisions at 1.97A GeV have been performed and show correlations resulting from the decays of the {Delta} resonance, the {Lambda} baryon, and possibly the N{sup {asterisk}}(1440) resonance. A reduction in the {Delta} mass is observed and the mass reduction increases with collision centrality. Events generated by the relativistic cascade model (ARC) also reveal a mass reduction. The mass reduction is related to the size of the reaction volume and the details of {Delta} production mechanisms in heavy ion collisions. {copyright} {ital 1997} {ital The American Physical Society}

We have studied the yield of individual fragments formed in the projectile fragmentation of gold nuclei at 1 AGeV incident on a carbon target as a function of the total charge multiplicity. The yields of fragments of different nuclear charge peak at different multiplicities. We show that this behavior can be used to determine the critical exponent σ. We obtain σ = 0.68±0.05, consistent with the liquid-gas value.

A systematic analysis of multifragmentation (MF) in fully reconstructed events from $1A\mathrm{GeV}$ Au, La, and Kr collisions with C has been performed. These data are used to provide a definitive test of the variable volume version of the statistical multifragmentation model (SMM). A single set of SMM parameters directly determined by the data and the semi-empirical mass formula are used after the adjustable inverse level density parameter ${\ensuremath{\epsilon}}_{0}$ is determined by the fragment distributions. The results from SMM for second stage multiplicity, size of the biggest fragment, and the intermediate mass fragments are in excellent agreement with the data. Multifragmentation thresholds have been obtained for all three systems using SMM prior to secondary decay. The data indicate that both thermal excitation energy ${E}_{\mathrm{th}}^{*}$ and the isotope ratio temperature ${T}_{\mathrm{H}\mathrm{e}\ensuremath{-}\mathrm{D}\mathrm{T}}$ decrease with increase in system size at the critical point. The breakup temperature obtained from SMM also shows the same trend as seen in the data. The SMM model is used to study the nature of the MF phase transition. The caloric curve for Kr exhibits back-bending (finite latent heat) while the caloric curves for Au and La are consistent with a continuous phase transition (nearly zero latent heat) and the values of the critical exponents \ensuremath{\tau}, \ensuremath{\beta}, and \ensuremath{\gamma}, both from data and SMM, are close to those for a ``liquid-gas'' system for Au and La. We conclude that the larger Coulomb expansion energy in Au and La reduces the latent heat required for MF and changes the nature of the phase transition. Thus the Coulomb energy plays a major role in nuclear MF.

Transverse flow has been studied as a function of impact parameter for pions and protons from the reaction 1.15AGeV 197Au+197Au. We observe an “antiflow” behavior for both π+ and π− in peripheral collisions.Received 29 July 1996DOI:https://doi.org/10.1103/PhysRevLett.78.4165©1997 American Physical Society

It is shown that the Fisher droplet model, percolation, and nuclear multifragmentation share the common features of reducibility (stochasticity in multiplicity distributions) and thermal scaling (one-fragment production probabilities are Boltzmann factors). Barriers obtained, for cluster production on percolation lattices, from the Boltzmann factors show a power-law dependence on cluster size with an exponent of 0.42+/-0.02. The EOS Collaboration Au multifragmentation data yield barriers with a power-law exponent of 0.68+/-0.03. Values of the surface energy coefficient of a low density nuclear system are also extracted.

The Li7+p interaction has been extensively studied and its various products analysed. The results confirm the presence of the well known levels of Be8 at 2.9, 17.63 and 18.15 MeV and give clear evidence for the existence of the discussed 7.56 MeV level. Three new levels of Be8 have been discovered at the energies 13.91, 17.9 and 18.0 MeV. Widths, angular momenta, parities and isobaric spins of several levels have been determined Some anomalies of the Li7+p interaction, previously observed by others, are explained.

It is shown that thermodynamic scaling when applied to systems with few (∼150) constituents, in accordance with the theory of critical phenomena, is observed in nuclear multifragmentation. Yields of different nuclear fragments, obtained over a wide range of excitation energies, collapse with some scatter onto a universal curve. This curve is the nuclear scaling function, which is intimately related to the free energy of the system. The determination of the scaling function forms the basis for quantitatively predicting the critical behavior in nuclei.

The interactions of ${}^{36}\mathrm{Ar}$ projectile nuclei with energies of 361, 546, and 765 MeV/nucleon and ${}^{40}\mathrm{Ar}$ nuclei with 352 MeV/nucleon, have been studied in a liquid-hydrogen target as part of a program to study interactions of relevance to the problem of cosmic-ray propagation in the interstellar medium. We have measured the cross sections for the production of isotopic fragments of the projectile nuclei in these interactions. The variations of these cross sections with mass, charge, and energy, are examined for insights into any systematic features of this type of fragmentation reaction that might aid predictions of other, unmeasured cross sections. These cross sections are also compared with the values derived from the most commonly used prediction techniques. It is suggested that these techniques could be improved by taking account of the systematic features identified here.

Using charged-particle-exclusive measurements of $\mathrm{Au}+\mathrm{Au}$ collisions in the Bevalac's EOS time projection chamber, we demonstrate the advantages of an alternative representation of the squeeze-out phenomenon where the speed of collective expansion is slowest in the plane of the reaction, and is modulated sinusoidally according to fragment azimuth relative to this plane. This simpler representation facilitates a highly comprehensive description of light fragment spectra and the three main categories of collective motion: sideward flow, squeeze-out, and radial expansion.

A fast neutron spectrometer consisting of a wide suitably shaped converter sheet and a silicon junction detector is described. Efficiency and resolving power are calculated and experimentally checked using mylar and polyethylene radiators. Screening of the detector against direct neutrons yields a good signal to noise ratio. The energy spectrum of neutrons from a PoBe source is measured and the comparison with the known data discussed.

Abstract We have measured the radiation tolerance of poly-crystalline and single-crystalline diamonds grown by the chemical vapor deposition (CVD) process by measuring the charge collected before and after irradiation in a 50 m pitch strip detector fabricated on each diamond sample. We irradiated one group of sensors with 800 MeV protons, and a second group of sensors with 24 GeV protons, in steps, to protons cm −2 and protons cm −2 respectively. We observe the sum of mean drift paths for electrons and holes for both poly-crystalline CVD diamond and single-crystalline CVD diamond decreases with irradiation fluence from its initial value according to a simple damage curve characterized by a damage constant for each irradiation energy and the irradiation fluence. We find for each irradiation energy the damage constant, for poly-crystalline CVD diamond to be the same within statistical errors as the damage constant for single-crystalline CVD diamond. We find the damage constant for diamond irradiated with 24 GeV protons to be and the damage constant for diamond irradiated with 800 MeV protons to be . Moreover, we observe the pulse height decreases with fluence for poly-crystalline CVD material and within statistical errors does not change with fluence for single-crystalline CVD material for both 24 GeV proton irradiation and 800 MeV proton irradiation. Finally, we have measured the uniformity of each sample as a function of fluence and observed that for poly-crystalline CVD diamond the samples become more uniform with fluence while for single-crystalline CVD diamond the uniformity does not change with fluence.

Chemical Vapor Deposited (CVD) polycrystalline diamond has been proposed as a radiation-hard alternative to silicon in the extreme radiation levels occurring close to the interaction region of the Large Hadron Collider. Due to an intense research effort, reliable high-quality polycrystalline CVD diamond detectors, with up to 270μm charge collection distance and good spatial uniformity, are now available. The most recent progress on the diamond quality, on the development of diamond trackers and on radiation hardness studies are presented and discussed.

The energy spectra of the charged particles produced in the (n, p) and (n, α) reactions in silicon are analysed using silicon detectors as targets. The excitation functions for the Si28(n, p) and Si29(n, α) transitions are given from 3.7 to 5.5 MeV. The observed fluctuations can hardly be attributed to single resonant states; it is suggested to interpret them as due mainly to fluctuations in the level density of the intermediate nuclei.

We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 μm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) × 1015 protons/cm2, (1.43±0.14) × 1016 neutrons/cm2, and (6.5±1.4) × 1014 pions/cm2, respectively. By observing the charge induced due to the separation of electron-hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62±0.07(stat)±0.16(syst)× 10-18 cm2/(p μm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65±0.13(stat)±0.18(syst)× 10-18 cm2/(n μm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0±0.2(stat)±0.5(syst)× 10-18 cm2/(π μm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.

The isotopic production cross sections for ${}^{40}\mathrm{Ca}$ projectiles at 357, 565, and 763 MeV/nucleon interacting in a liquid hydrogen target have been measured by the Transport Collaboration at the LBL HISS facility. The systematics of these cross sections are studied, and the results indicate that nuclear structure effects are present in the isotope production process during the relativistic collisions. The newly measured cross sections are also compared with those predicted by semiempirical and parametric formulas, but the predictions do not fully describe the systematics such as the energy dependence. The consequences of the cross section systematics in galactic cosmic ray studies are also discussed.

We study the energy dependence of collective (hydrodynamic-like) nuclear matter flow in (400--1970)A MeV $\mathrm{Ni}+\mathrm{Au}$ and (1000--1970)A MeV $\mathrm{Ni}+\mathrm{Cu}$ reactions. The flow increases with energy, appears to reach a maximum, and then to decrease at higher energies. A way of comparing the energy dependence of flow values for different projectile-target mass combinations is introduced, which demonstrates a more-or-less common scaling behavior among flow values from different systems.

Interstrip and backplane capacitances on silicon microstrip detectors with p+ strip on n substrate of 320μm thickness were measured for pitches between 60 and 240μm and width over pitch ratios between 0.13 and 0.5. Parametrisations of capacitance w.r.t. pitch and width were compared with data. The detectors were measured before and after being irradiated to a fluence of 4×1014protons/cm2 of 24GeV/c momentum. The effect of the crystal orientation of the silicon has been found to have a relevant influence on the surface radiation damage, favouring the choice of a 〈100〉 substrate. Working at high bias (up to 500 V in CMS) might be critical for the stability of detector, for a small width over pitch ratio. The influence of having a metal strip larger than the p+ implant has been studied and found to enhance the stability.

The one-proton and one-neutron transfer reactions in the interaction of 34S with incident 32S were studied in the 0–3.5 MeV excitation energy range of the exit nuclei. The experimental set-up (kinematic identification technique, implanted targets, etc.) has allowed an angular resolution of 0.2°, a mass resolution of 1.5% and a Q-value resolution of 0.35 MeV. Comparison with DWBA computations using an analytical approximation for the radial integral, with insertion of suitable recoil corrections, demonstrates the absorptive direct mechanisms of the reactions, even when double excitation of residual nuclei is present. The extracted values for the products of spectroscopic factors are in very good agreement with the known values and they are confirmed by EFR-DWBA computations. The selectivities of the reaction receive about the same contributions from the nuclear structure as from the specific reaction mechanism.

Diamond devices have now become ubiquitous in the LHC experiments, finding applications in beam background monitoring and luminosity measuring systems. This sensor material is now maturing to the point that the large pads in existing diamond detectors are being replaced by highly granular tracking devices, in both pixel and strip configurations, for detector systems that will be used in Run II at the LHC and beyond. The RD42 collaboration has continued to seek out additional diamond manufacturers and quantify the limits of the radiation tolerance of this material. The ATLAS experiment has recently installed, and is now commissioning a fully-fledged pixel tracking detector system based on diamond sensors. Finally, RD42 has recently demonstrated the viability of 3D biased diamond sensors that can be operated at very low voltages with full charge collection. These proceedings describe all of these advances.

We have measured the production of light nuclei (A<~3) in 11.6GeV/c Au-Au collisions at the Brookhaven Alternating Gradient Synchrotron (AGS). The transverse mass spectra are analyzed using a thermal fireball model, and the yields for different particle species are discussed assuming coalescence and fragmentation as possible production mechanisms. The wide acceptance range of the 3He measurements permits a broad study of the coalescence parameter B3 as functions of transverse momentum and rapidity. Comparisons with data obtained previously at AGS energies suggest that the simple models are insufficient to describe fully the production mechanisms of light nuclei.Received 24 August 2001DOI:https://doi.org/10.1103/PhysRevC.65.034907©2002 American Physical Society

A position sensitive detector made up of thin discs of NE102 scintillating material is proposed for the detection of neutrons emitted in intermediate and high energy heavy ion reactions (0.1≤En≤3 GeV). Positions and time of “hits” are determined by measuring the different times at which light reaches N photomultiplier tubes placed around each disc at the vertices of a regular polygon. A new method, based on Multiple Elliptical Coordinate Systems (MECS), is developed to linearize equations correlating signal times to coordinates and time of hit.

The interactions of deuterons with 7Li, producing two α-particles and a neutron in the final state are studied at Ed=0.8 and 1 MeV. The spectra and the angular distribution of the α-particles and neutrons, and the angular correlation of the α-particles are measured. The two-dimensional display of α-particle pulses is studied. The contribution of the 7Li(d, α)5He reaction to the α-spectra and the angular distribution of the α-particles from the decay of 5He are obtained.

Detectors based on Chemical Vapor Deposition (CVD) diamond have been used extensively and successfully in beam conditions/beam loss monitors as the innermost detectors in the highest radiation areas of Large Hadron Collider (LHC) experiments. The startup of the LHC in 2015 brought a new milestone where the first polycrystalline CVD (pCVD) diamond pixel modules were installed in an LHC experiment and successfully began operation. The RD42 collaboration at CERN is leading the effort to develop polycrystalline CVD diamond as a material for tracking detectors operating in extreme radiation environments. The status of the RD42 project with emphasis on recent beam test results is presented.

Transverse kinetic energies of individual fragments have been measured over a broad range of emitter excitation energies for the reaction $1A\mathrm{GeV}$ $\mathrm{A}\mathrm{u}+\mathrm{C}.$ For excitation energies leading to large intermediate mass fragment multiplicities, these transverse energies require large collective radial expansion of the emitting systems. However, the traditional decomposition of the transverse energy into a thermal component and a Coulomb and collective component proportional to the fragment mass cannot account for this expansion. Expansion velocities show an increase with decreasing fragment $Z$ and thus indicate fractionation of the collective energy for the expanding system. This collective energy increases with emitter excitation up to about 50% of the energy deposited for a nuclear system with total energy $\ensuremath{\sim}12A\mathrm{MeV}.$ The bulk of the collective energy is carried away by ejectiles of $Z&lt;~3.$

The isotopic production cross sections for 22Ne projectiles at 377,581, and 894 MeV nucleon-1 and 26Mg projectiles at 371 and 576 MeV nucleon-1 interacting in a liquid hydrogen target have been measured by the Transport Collaboration at the Lawrence Berkeley Laboratory Heavy-Ion Spectrometer System (LBL HISS) facility. These cross sections are compared with those predicted by semi-empirical formulae. The systematics are studied to develop suitable inputs for calculations of galactic cosmic-ray interstellar transport. These calculations are used to unfold the transport effects from available observations of cosmic-ray CNO isotopes to extract the underlying source composition. With these new cross section measurements, the previously reported enhancement of 18O at the cosmic-ray source, which is sensitive to the cross sections for production from 22Ne and 26Mg and the uncertainties in cross section prediction formulae, may be explained. There is no evidence for an enhancement of 18O when these new cross sections are used in a weighted slab propagation calculation.

The deposition conditions and the detection properties of a homoepitaxial diamond film, grown by microwave Chemical Vapor Deposition (CVD) on a HPHT single crystal substrate are reported. The charge collection spectrum, measured under irradiation with a triple 239 Pu 241 Am 244 Cm source emitting 5.16, 5.48 and 5.80 MeV a-particles respectively, shows three clearly resolved peaks with an energy resolution of about 1.1%. Both the charge collection efficiency and the energy resolution reach saturation values when the applied voltage exceeds 60 V, suggesting 100% collection efficiency. The detector was also tested with 14.8 and 14.1 MeV neutrons. The obtained collection spectra show a well separated 12 C(n,a0) 9 Be reaction peak with an energy spread of 0.5 MeV for 14.8 MeV neutrons and 0.3 MeV for 14.1 MeV neutrons, which are fully compatible with the energy spread of the incident neutrons. D 2005 Elsevier B.V. All rights reserved.

The detection properties of heteropitaxial (polycrystalline, pCVD) and homoepitaxial (single crystal, scCVD) diamond films grown by microwave chemical vapor deposition (CVD) in the Laboratories of Roma “Tor Vergata” University are reported. The pCVD diamond detectors were tested with α-particles from different sources and 12C ions produced by 15 MV Tandem accelerator at Southern National Laboratories (LNS) in Catania (Italy). pCVDs were also used to monitor 14 MeV neutrons produced by the D-T plasma at Joint European Torus (JET), Culham, U.K. The limit of pCVDs is the poor energy resolution. To overcome this problem, we developed scCVD diamonds using the same reactor parameters that optimized pCVD diamonds. scCVD were grown on a low cost (1 0 0) HPHT single crystal substrate. A detector 110μm thick was tested under α-particles and under 14 MeV neutron irradiation. The charge collection efficiency spectrum measured under irradiation with a triple α-particle source shows three clearly resolved peaks, with an energy resolution of about 1.1%. The measured spectra under neutron irradiation show a well separated C(n,α0)9Be12 reaction peak with an energy spread of 0.5 MeV for 14.8 MeV neutrons and 0.3 MeV for 14.1 MeV neutrons, which are fully compatible with the energy spread of the incident neutron beams.

In sight of the luminosity increase of the High Luminosity-LHC (HL-LHC), most experiments at the CERN Large Hadron Collider (LHC) are planning upgrades for their innermost layers in the next 5–10 years. These upgrades will require more radiation tolerant technologies than exist today. Usage of Chemical Vapor Deposition (CVD) diamond as detector material is one of the potentially interesting technologies for the upgrade. CVD diamond has been used extensively in the beam condition monitors of BaBar, Belle, CDF and all LHC experiments. Measurements of the radiation tolerance of the highest quality polycrystalline CVD material for a range of proton energies, pions and neutrons obtained with this material are presented. In addition, new results on the evolution of various semiconductor parameters as a function of the dose rate are described.

In the present study, results towards the development of a 3D diamond sensor are presented. Conductive channels are produced inside the sensor bulk using a femtosecond laser. This electrode geometry allows full charge collection even for low quality diamond sensors. Results from testbeam show that charge is collected by these electrodes. In order to understand the channel growth parameters, with the goal of producing low resistivity channels, the conductive channels produced with a different laser setup are evaluated by Raman spectroscopy.

In this work, we report on the structural characterization of homoepitaxial Microwave Plasma Enhanced CVD diamond grown onto Ib diamond substrates by varying systematically the methane to hydrogen ratio in the gas mixture (1–7% CH4). X-ray diffraction, Raman spectroscopy and photoluminescence (PL) have been used to characterize the diamond samples. Raman measurements pointed out the excellent crystalline quality and phase purity of the specimens. PL measurements in the 1.7–2.7 eV energy range have shown completely flat spectra, excluding the presence of nitrogen-related optical centers. Such results show that the homoepitaxial CVD diamond can be grown, at moderate microwave power (720 W), and at growth rates not too low (∼ 1 μm/h) preserving a good quality. Moreover, the homoepitaxial crystals exhibited a strong free-exciton recombination radiation at room temperature even at the highest methane concentration used (7%). Preliminary measurements of the lifetime of the free exciton at room temperature have been also performed. The excitation was produced by a 5 ns pulsed laser irradiation at energies above the diamond band gap. The results have been compared with the structural properties of the samples and correlated with the growth conditions.

Marx-topology modulator, capable of providing the required waveform shaping to stabilize the accelerating gradient and compensate for beam loading, will be presented, along with development data from the prototype unit.

A sample of Λ's produced in 2 A GeV 58Ni + natCu collisions has been obtained with the EOS Time Projection Chamber at the Bevalac. Low background in the invariant mass distribution allows for the unambiguous demonstration of Λ directed flow. The Λ mT spectrum at mid-rapidity has the characteristic shoulder-arm shape of particles undergoing radial transverse expansion. A linear dependence of Λ multiplicity on impact parameter is observed, from which a total Λ+Σ0 production cross section of 112±24 mb is deduced. Detailed comparisons with the ARC and RVUU models are made.

Measurements of angular distributions for elastic scattering in the $^{11}\mathrm{B}$ + $^{12}\mathrm{C}$ system were performed in the energy range from 15 to 40 MeV c.m. in \ensuremath{\simeq}2.5 MeV steps in broad angular regions up to about ${170}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$ c.m. The optical-model parameters were determined from the analysis of the cross section at forward angles. The rise of cross section in the backward angles was explained as direct elastic transfer. From the distorted-wave Born approximation analysis, the values of proton spectroscopic factor in $^{12}\mathrm{C}$ were found. They exhibit a strong energy dependence in the energy region between 5 and 40 MeV c.m.

A systematic analysis of the moments of the fragment size distribution has been carried out for the multifragmentation of 1AGeV Au, La, and Kr on carbon. The breakup of Au and La is consistent with a continuous thermal phase transition. The data indicate that the excitation energy per nucleon and isotopic temperature at the critical point decrease with increasing system size. This trend is attributed primarily to the increasing Coulomb energy with finite size effects playing a smaller role.Received 5 September 2000DOI:https://doi.org/10.1103/PhysRevC.64.041605©2001 American Physical Society

We have measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 µm pitch strip detector fabricated on each diamond sample before and after irradiation.We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV) and a third group of samples with 200 MeV pions, in steps, to (8.8 ± 0.9) × 10 15 protons/cm 2 , (1.43 ± 0.14) × 10 16 neutrons/cm 2 and (6.5 ± 0.5) × 10 14 pions/cm 2 respectively.By observing the charge induced due to the separation of electron-hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all data sets can be described by a first order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons and 200 MeV pions.We find the damage constant for diamond irradiated with 70 MeV protons to be 1.61 ± 0.07 (stat) ± 0.15 (syst) × 10 -18 cm 2 /(p µm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65 ± 0.13 (stat) ± 0.16 (syst) × 10 -18 cm 2 /(n µm) and the damage constant for diamond irradiated with 200 MeV pions to be 2.0 ± 0.2 (stat) ± 0.5 (syst) × 10 -18 cm 2 /(π µm).The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond.We find 70 MeV protons are 2.60 ± 0.27 times more damaging than 24 GeV protons, fast reactor neutrons are 4.27 ± 0.34 times more damaging than 24 GeV protons and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons.We also observe the measured data can be described by a universal damage curve for all proton, neutron and pion irradiations we have performed of Chemical Vapor Deposition diamond.Finally, we confirm the FWHM/MP ratio of the signal spectrum, a measure of the spatial uniformity of the collected charge, decreases with fluence for polycrystalline Chemical Vapor Deposition diamond and this effect can also be described by a universal curve.

E896 was designed to search for the predicted short-lived six-quark H0 di-baryon. The goal is to enhance the existing knowledge by extending the search into regions of shorter lifetimes (approximately half that of the lambda) and via exploring a new creation channel, that of the coalescence of two lambdas. Two main tracking chambers are used, a distributed drift chamber positioned to measure low-pt and high-rapidity neutral particle decay products and a silicon drift detector array which measures particle production at mid-rapidity. Both detectors are also investigating lambda polarization, over their respective coverages, for Au-Au collisions at 11.3 GeV/nucleon. The current status of the H0 di-baryon search and preliminary results of the strange particle production and polarization measurements will be presented.

Energy spectra of hydrogen and helium isotopes emitted in Au+Au collisions at 0.25, 0.40, 0.60, 0.80, 1.0, and 1.15A GeV have been measured. A systematic study of the shapes of the spectra reveals a significant non-thermal component consistent with collective radial flow. The strength of this component is evaluated as a function of bombarding energy. Comparisons of the flow signal to predictions of QMD and BUU models are made. Using reverse kinematics, the breakup of gold nuclei has been studied in Au+C reactions at 1.0A GeV. The moments of the resulting charged fragment distribution provide evidence that nuclear matter possesses a critical point observable in finite nuclei. Values for the critical exponents γ, β, and τ have been determined. These values are close to those for liquid-gas systems and different from those for 3D percolation.

The neutron energy spectrum and the two-neutron correlation function have been measured for the E/A=45 MeV Ni + Al reaction in order to assess the space-time characteristics of the neutron emitting source. When comparing the data to a statistical model, the kinetic energy spectra, the integrated correlation function as well as the longitudinal correlation function are reproduced by one single source. However, only the inclusion of a short-lived pre-equilibrium component can account for the stronger correlation exhibited by neutron pairs emitted with high total momentum. The correlation function from events defined as peripheral by constraints on the highest charge of the projectile-like fragment does show a significantly weaker correlation than the minimum bias sample.

This report is intended to describe first, the principal physics reasons for an ambitious experimental program in neutrino physics and proton decay based on construction of a series of massive water Cherenkov detectors located deep underground (4850 ft) in the Homestake Mine of the South Dakota Science and Technology Authority (SDSTA); and second, the engineering design of the underground chambers to house the Cherenkov detector modules; and third, the conceptual design of the water Cherenkov detectors themselves for this purpose. In this proposal we show the event rates and physics sensitivity for beams from both FNAL (1300 km distant from Homestake) and BNL (2540 km distant from Homestake). The program we propose will benefit with a beam from FNAL because of the high intensities currently available from the Main Injector with modest upgrades. The possibility of tuning the primary proton energy over a large range from 30 to 120 GeV also adds considerable flexibility to the program from FNAL. On the other hand the beam from BNL over the larger distance will produce very large matter effects, and consequently a hint of new physics (beyond CP violation) can be better tested with that configuration. In this proposal we focus on the CP violation physics. Included in this document are preliminary costs and time-to-completion estimates which have been exposed to acknowledged experts in their respective areas. This presentation is not, however, to be taken as a technical design report with the extensive documentation and contingency costs that a TDR usually entails. Nevertheless, some contingency factors have been included in the estimates given here. The essential ideas expressed here were first laid out in a letter of intent to the interim director of the Homestake Laboratory on July 26, 2001. Since that time, the prospect of a laboratory in the Homestake Mine has been realized, and the design of a long baseline neutrino experiment has been refined. The extrapolation contained in this proposal is within the common domain of thinking in the area of physics discussed here. It needs now only the encouragement of the funding agencies, NSF and DOE.

Diamond films grown by microwave plasma enhanced chemical vapor deposition have been investigated as particle detectors for nuclear physics. A CH4CO2 gas mixture was used as gas feed during the growth process. The film morphology, preferential orientation and crystal quality were systematically changed by varying the deposition parameters. In particular, the substrate temperature, Ts, and the CH4 concentration in the gas mixture were chosen in the 750–850 °C and 47–50% ranges, respectively. The resulting films were characterized by X-ray diffraction and scanning electron microscopy. The correlation of the above structural properties with the response of the diamond-based detectors was then extensively studied. To this purpose, they were irradiated with a 5.5 MeV 241Am alpha particle source under different applied electric fields and their collection lengths and efficiencies were compared. In particular, it was found that the limiting factor in the detector performances is related to intra-grain trapping centers, whose effectiveness is increasingly higher when the sample preferential orientation tends to (100) texturing or moving away from the Si-diamond interface.

Over the past year the RD42 collaboration continued to improve CVD diamond detectors for high luminosity experiments at the LHC. We have made extensive progress on diamond quality and radiation hardness studies using the highest quality diamond were performed up to fluences of 20 ◊ 10 15 p/cm 2 . Transforming this technology to specific requirements of the LHC has begun. The first ATLAS diamond pixel module was constructed using the same bump-bonding and electronics that the present ATLAS pixel modules use. Both ATLAS and CMS have tested and are planning to use diamond for their beam conditions monitoring systems. In this report we present the progress made and the requirements specific to the programme.

Polycrystalline (pCVD) and single crystal (scCVD) diamond films grown from Chemical Vapour Deposition (CVD), if sufficiently pure at Raman analysis, are very good materials for beam or flux monitors inside accelerators or nuclear reactors. This is because they are very hard to damage in high radiation fields and very resistant to high temperatures. Films of pCVD diamond are, however, not so good as spectroscopy detectors due to inhomogeneities induced by their growth in grains with the consequent presence of grain boundaries which worsen their energy resolution. The latter can be significantly improved by growing scCVD diamond films onto HPHT synthetic diamond substrates. We have shown that it is possible to measure the density of defects inside diamond specimens using as probes suitable penetrating nuclear radiations. With the preliminary results reported here we'll show that, bombarding CVD diamond films grown at Roma “Tor Vergata” with energetic protons and 4He, 6Li and 12C ions produced in the accelerators of Catania laboratories, the pulse height defects are higher than those in silicon detectors and likewise well described by a power law in the deposited energy. Furthermore, we'll show that pulse heights for the same particles seem to depend on the duration of the measurement, thus exhibiting a sort of depolarization of the insulator when exposed to the electric voltage which makes it a particle detector.

Two fast neutron spectrometers are described and experimentally checked for absolute measurements of energy spectra of neutrons emitted in nuclear reactions and of neutrons from collimated beams. The recoil protons ejected from large radiator sheets are detected by junction detectors. A good signal to noise ratio is obtained by screening the junction detector against direct neutrons. A satisfactory compromise between efficiency and resolving power is realized.

CVD mono-crystalline diamond thin films deposited on a doped diamond and aluminum backing were employed as detectors of the radiation emitted from the laser-generated plasma. Laser-matter interactions were obtained by the use of an Nd:Yag repetitive laser at INFN-LNS in Catania operating at 1010 W/cm2 pulse intensity, and a high-power iodine PALS laser in Prague operating at 1015 W/cm2 pulse intensity. Plasmas were obtained by ablating Al, Ta, Au, and CF2 bulk targets. Plasma characterization was carried out using diamond detectors and ion collectors placed at different distances and angles in relation to the position of the ablated target. Photons, electrons, and ions hitting the sensible volume of the detector generate electronhole pairs (loosing 13 eV for a pair), resulting in an arising of the voltage signal at the device electrodes, which is proportional to the deposited energy. Diamond detectors can measure UV, X-rays, electrons, and ions. The time-of-flight (TOF) technique was exploited to separate photon, electron, and particle contributions. Because of the high gap of the diamond band structure (5.48 eV), the detectors are blind to visible and IR light from the plasma, which results in very low background current. The TOF diamond spectra were compared with traditional ion collector spectra using the experimental data obtained from the experiments conducted at the Catania and Prague laboratories. The results indicate that the ion energy resolution of the employed diamond detectors is high and that the fast electrons can be detected from a deconvolution procedure applied to the fast photo-peak. Information about the mean energy of soft X-rays could be obtained by analyzing the fast contribute of the spectra acquired by using different absorber films.

We present results obtained with full-size wedge silicon microstrip detectors bonded to APV6 (Raymond et al., Proceedings of the 3rd Workshop on Electronics for LHC Experiments, CERN/LHCC/97-60) readout chips. We used two identical modules, each consisting of two crystals bonded together. One module was irradiated with 1.7×1014neutrons/cm2. The detectors have been characterized both in the laboratory and by exposing them to a beam of minimum ionizing particles. The results obtained are a good starting point for the evaluation of the performance of the “ensemble” detector plus readout chip in a version very similar to the final production one. We detected the signal from minimum ionizing particles with a signal-to-noise ratio ranging from 9.3 for the irradiated detector up to 20.5 for the non-irradiated detector, provided the parameters of the readout chips are carefully tuned.

Light pulses seen by photomultiplier tubes (PMTs) after propagation within long scintillator slats or rods, or large disc-shaped scintillators are investigated and compared with those from point-like scintillators. Results of experimental tests for the disc-shaped configuration, performed with the single photon counting technique, are presented and compared with numerical calculations. These calculations were performed describing the light pulse shape by means of a new, quite general analytical method based on the geometrical optics concepts of virtual light paths and images. The associated electric pulses produced by the PMTs coupled to the scintillators are then discussed with particular emphasis on their dependence on the distance between light source and photocathode.

The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z ≥ 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the LBL Bevalac HISS facility with 20 projectiles from 4He to 58Ni in the energy range 393–910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.

This paper describes the main achievements in the development of radiation resistant silicon detectors to be used in the CMS tracker. After a general description of the basic requirements for the operation of large semiconductor systems in the LHC environment, the issue of radiation resistance is discussed in detail. Advantages and disadvantages of the different technological options are presented for comparison. Laboratory measurements and test beam data are used to check the performance of several series of prototypes fabricated by different companies. The expected performance of the final detector modules are presented together with preliminary test beam results on system prototypes.

Neutrons produced in the ${}^{40}$Ca+H reaction at ${E}_{\mathrm{lab}}=357A$ and $565A$ MeV have been detected using a three-module version of the multifunctional neutron spectrometer MUFFINS. The detector covered a narrow angular range around the beam in the forward direction $(0\ifmmode^\circ\else\textdegree\fi{}\ensuremath{-}3.2\ifmmode^\circ\else\textdegree\fi{})$. Semi-inclusive neutron production cross sections, at the two energies, are reported together with neutron energy spectra, angular, rapidity, and transverse momentum distributions. Comparison with a Boltzmann-Nordheim-Vlasov approach + phase space coalescence model is discussed.

Abstract The elastic scattering differential cross section for 32 S incident on 33 S at E inc = 91.3 MeV has been measured. The observed backward oscillations are successfully described by explicit inclusion of a parity-dependent term in the real potential for the optical-model calculations of the elastic scattering. To investigate possible sources of the parity-dependent term, the backward oscillations were also interpreted as being produced by the interference between the elastic amplitude and the one-neutron elastic one-step transfer process.

Because of its high radiation hardness, diamond can be used better than other materials in the intense radiation field characterizing the interior region of a particle beam in an accelerator. In effect, the measurements reported here were carried out by placing diamond detectors under continuous irradiation in the 26-MeV proton beam of the 15-MV TANDEM accelerator of Southern National Laboratory (LNS) of INFN in Catania. The diamond detectors were built in the Rome Tor Vergata Laboratory. Diamond films were deposited by microwave plasma enhanced chemical vapor deposition on silicon substrates. A four-pixel beam monitor prototype was then realized by depositing four titanium gold contacts on the diamond surface. The signal was found to be stable and reproducible. The collected charge in DC mode was more than 20 000 electrons/protons for a diamond thickness of 65 μm, thus exhibiting a gain of approximately 104 with respect to the Faraday cup. For the measured samples, both response and release times of approximately 1 s were observed in the above experimental conditions. An analysis of the relative sensitivity between pixels was also performed. No differences of the detector current and Faraday cup current ratio were observed for different pixels, indicating the homogeneity of the beam monitor response.

Abstract The transport properties in synthetic diamond are studied using high quality diamond films grown by microwave plasma enhanced chemical vapor deposition (CVD). In particular, electron and hole contributions to the diamond carrier dynamics are successfully separated and defect distribution inside specimens is obtained. This is achieved through a systematic investigation of the signals obtained from properly biased diamonds irradiated with differently penetrating nuclear particles. To this purpose 12C ions produced by the 15 MV Tandem accelerator of the Southern National Laboratories of INFN in Catania (Italy) are used as a probe. The ion beam energy is varied in the 22–91 MeV range (penetration depth from 10.5 μm to the thickness of the used samples, deposited energies from 22 to 62 MeV and mean energy densities from 0.8 to 2.1 MeV/μm, respectively). The sample responses are studied as a function of the 12C energy and penetration depth, both in the positive and negative bias polarization. The experimental results clearly show that, when the detector is previously driven in the so-called pumped state by 90Sr β-particle irradiation, a different behavior of signals is observed in the positive and negative polarization states. The data are analysed in the framework of a properly modified Hecht model were the different behavior of carriers and influence of the variation in the ionization density along the path of the incident particles are considered. As a novelty the inhomogeneous distribution of defects is taken into account. By fitting the experimental curves with the model, a quantitative estimate of the defects distribution and of the correlated mean drift distance for electron and holes can be obtained. A good agreement is observed, thus allowing a better understanding of the diamond growth.

The planned upgrade of the LHC to the High-Luminosity-LHC will push the luminosity limits above the original design values. Since the current detectors will not be able to cope with this environment ATLAS and CMS are doing research to find more radiation tolerant technologies for their innermost tracking layers. Chemical Vapour Deposition (CVD) diamond is an excellent candidate for this purpose. Detectors out of this material are already established in the highest irradiation regimes for the beam condition monitors at LHC. The RD42 collaboration is leading an effort to use CVD diamonds also as sensor material for the future tracking detectors. The signal behaviour of highly irradiated diamonds is presented as well as the recent study of the signal dependence on incident particle flux. There is also a recent development towards 3D detectors and especially 3D detectors with a pixel readout based on diamond sensors.

The properties of the remnant resulting from the emission of prompt particles in the interaction of 1AGeV197Au+C interactions have been compared with intranuclear cascade and Boltzmann-Uehling-Uhlenback transport calculations. The number of first-stage particles and the energy spectra of first-stage protons are also compared. Both models can fit the general but not the detailed features of the data.Received 24 March 1999DOI:https://doi.org/10.1103/PhysRevC.60.064606©1999 American Physical Society

In this paper, we report on the characterization of homoepitaxial CVD diamond grown onto HPHT Ib diamond substrates by varying systematically the methane to hydrogen ratio in the deposition gas mixture (1–7%) and the microwave power (520–720 W). Growth rates up to approximately 2.2 μm/h have been achieved. X-ray diffraction, Raman spectroscopy and photoluminescence (PL) have been used to characterize the diamond samples. Raman measurements point out an excellent crystalline quality and phase purity of the homoepitaxial specimens even at the highest CH4 concentration used. Completely flat PL spectra registered in a wide energy range (1.7–2.7 eV) exclude impurity contamination of the diamond samples. Such results show that homoepitaxial CVD diamond can be grown, at moderate microwave power and with moderate growth rate, preserving a good crystalline quality.

Abstract The photoresponse of high quality single crystal diamond films homoepitaxially grown by Chemical Vapor Deposition (CVD) onto low cost diamond substrates has been studied. The time evolution electrical response to the excitation by 5 ns laser pulses at 215 nm closely reproduces the laser pulse shape. The single crystal diamond response is therefore much faster than the laser pulse duration. The output signal is also very stable and reproducible, without significant priming or memory effects. Single crystal diamond films can therefore be grown by CVD having enough high quality to be used as photodetectors. However, a minor slow component shows up in the charge-integrated sample response. A systematic speed up of this slow component when increasing the detector temperature from − 25 °C to + 50 °C demonstrates its thermally activated origin. The slow component is therefore attributed to detrapping effects from shallow trapping centres. A model of the charge transport mechanism in the presence of trapping–detrapping centres can be developed and the results can be compared to the experimental ones. The activation energy of the shallow defects is accordingly determined as E a  = 0.4 eV.

Three-layer structures consisting of intrinsic/B-doped homoepitaxial CVD diamond grown onto commercial HPHT Ib substrates have been studied by means of Raman spectroscopy and photoluminescence (PL). The intrinsic layers have been deposited, at fixed methane to hydrogen ratio (1%), by systematically changing the substrate temperature (620–820 °C). Raman measurements point out the excellent crystalline quality and phase purity of the samples. Moreover, flat PL spectra in a wide energy range (1.7 eV–2.7 eV) indicate also their great purity. As the free-exciton recombination can be used to further probe the quality of synthetic diamond, measurements of free-exciton emission at room temperature have been also performed. The excitation was produced by a 5 ns pulsed tunable laser irradiation. The results have been compared with the detection characteristics of simple alpha-particle detector prototypes based on the analyzed samples. A clear correlation between excitonic emission and detector sensitivity is demonstrated. On the basis of these results, low methane concentrations (approx. 1% CH4/H2) in the deposition gas mixture and intermediate substrate temperatures (approx. 720 °C–770 °C) have been identified as the best working conditions of our growth reactor.

Abstract Compact solid-state detectors based on CVD single-crystal diamonds (SCD), configured in a p-type/intrinsic/Schottky-metal layered structure, are proposed for the detection of high-energy ions at the 15-MV tandem accelerator of the Southern National Laboratory of INFN in Catania. The spectroscopic response of two thin-film SCD detectors has been studied by varying the angle of incidence of a 27–77 MeV 12C-scattered ion beam and a simple theoretical model is reported for the fit of the experimental curves of the collected energy vs. the angle of incidence. A rough estimation of the detector sensitive thickness and of the charge collection efficiency has thus been obtained. Keywords: CVDsingle-crystal diamonddetectorsion beams

Diamond is used as detector material in high energy physics experiments due to its inherent radiation tolerance. The RD42 collaboration has measured the radiation tolerance of chemical vapour deposition (CVD) diamond against proton, pion, and neutron irradiation. Results of this study are summarized in this article. The radiation tolerance of diamond detectors can be further enhanced by using a 3D electrode geometry. We present preliminary results of a poly-crystalline CVD (pCVD) diamond detector with a 3D electrode geometry after irradiation and compare to planar devices of roughly the same thickness.

A position sensitive parallel plate (PSPP) stop detector for heavy ions with an active area of 70 × 76 mm2 has been developed. The cathode is a printed circuit board with parallel strips which form a delay-line. The position resolution is better than 1 mm in the x direction (orthogonal to the strips) and better than 2 cm in the y direction (along the strips). The anode time resolution is about 300 ps fwhm.

The inclusive light fragment (Z<~7) yield data in Au+Au reactions, measured by the EOS Collaboration at the LBNL Bevalac, are presented as a function of multiplicity. Moving from central to peripheral collisions the measured charge distributions develop progressively according to a power law which can be fitted, within errors, by a single τ exponent independently of the bombarding energy except for the data at 250A MeV. In addition, the location of the maximum in the individual yields of different charged fragments, for a given beam energy, shifts towards lower multiplicity as the fragment charge increases from Z=3 to Z=7. This trend is common to all six measured beam energies. Moments of charge distribution are also reported. The universal features observed in the present Au + Au data are consistent with previous experimental findings in the Au + C multifragmentation reaction at 1A GeV. Received 19 April 1999DOI:https://doi.org/10.1103/PhysRevC.61.044902©2000 American Physical Society

The transverse momenta (px,py) of projectile fragments produced by 1.0A GeV 197Au nuclei incident on Au and C targets have been measured. The medium and heavy fragments have px and py distributions, which are wider than predicted by models. For the Au target the widths of the distributions are significantly larger than those for C, particularly for the heavy fragments. The C distributions show a different gross structure, which may be due to the target-projectile size difference.Received 13 February 2001DOI:https://doi.org/10.1103/PhysRevC.64.014610©2001 American Physical Society

The CMS experiment at the LHC will comprise a large silicon strip tracker. This article highlights some of the results obtained in the R&D studies for the optimization of its silicon sensors. Measurements of the capacitances and of the high voltage stability of the devices are presented before and after irradiation to the dose expected after the full lifetime of the tracker.

This paper describes the proton irradiation campaign, performed at the INFN “Laboratori Nazionali del Sud” (LNS), on a silicon microstrip detector. The irradiated module is identical to the ones which are used to assemble the tracker inner barrel of the CMS experiment at the CERN Large Hadron Collider (LHC). The aim of the test was to verify the radiation resistance of the detector module to the LHC environment by checking its behavior with increasing fluence.

This report provides the results of an extensive and important study of the potential for a U.S. scientific program that will extend our knowledge of neutrino oscillations well beyond what can be anticipated from ongoing and planned experiments worldwide. The program examined here has the potential to provide the U.S. particle physics community with world leading experimental capability in this intensely interesting and active field of fundamental research. Furthermore, this capability could be unique compared to anywhere else in the world because of the available beam intensity and baseline distances. The present study was initially commissioned in April 2006 by top research officers of Brookhaven National Laboratory and Fermi National Accelerator Laboratory and, as the study evolved, it also provided responses to questions formulated and addressed to the study group by the Neutrino Scientific Advisory Committee (NuSAG) of the U.S. DOE and NSF. The participants in the study, its Charge and history, plus the study results and conclusions are provided in this report and its appendices. A summary of the conclusions is provided in the Executive Summary.

The Heavy Ion Spectrometer System (HISS) at the LBL Bevalac provided a unique facility for measuring projectile fragmentation cross-sections important in deconvolving the Galactic Cosmic Ray (GCR) source composition. The general characteristics of the apparatus specific to this application are described and the main features of the event reconstruction and analysis used in the TRANSPORT experiment are discussed.

Measurements of angular distributions for inelastic scattering in the $^{11}\mathrm{B}$${+}^{12}$C system with excitation of the ${2}^{+}$ (4.44 MeV) level of $^{12}\mathrm{C}$ and 1/${2}^{\mathrm{\ensuremath{-}}}$ (2.12 MeV) and 5/${2}^{\mathrm{\ensuremath{-}}}$ (4.44 MeV) levels of $^{11}\mathrm{B}$ nuclei were performed in the energy range from 15 to 40 MeV c.m. in \ensuremath{\simeq}2.5 MeV steps in broad angular regions up to about 170\ifmmode^\circ\else\textdegree\fi{} c.m. The cross section at forward angles was well described in the distorted-wave Born approximation by collective model with energy-independent deformation length. The rise of cross section at the backward angles was explained as inelastic proton transfer. The extracted values of the proton spectroscopic factors for the excited nuclei $^{12}\mathrm{C}_{4.44}^{\mathrm{*}}$ and $^{11}\mathrm{B}_{2.12}^{\mathrm{*}}$ are energy independent in contradiction to the previously found energy-dependent spectroscopic factor for $^{12}\mathrm{C}_{\mathrm{g}.\mathrm{s}.}$=p${+}^{11}$${\mathrm{B}}_{\mathrm{g}.\mathrm{s}.}$.

At present most experiments at the CERN Large Hadron Collider (LHC) are planning upgrades in the next 5-10 years for their innermost tracking layers as well as luminosity monitors to be able to take data as the luminosity increases and CERN moves toward the High Luminosity-LHC (HL-LHC). These upgrades will most likely require more radiation tolerant technologies than exist today. As a result this is one area of intense research, and Chemical Vapour Deposition (CVD) diamond is one such technology. CVD diamond has been used extensively in beam condition monitors as the innermost detectors in the highest radiation areas of all LHC experiments. This talk describes the preliminary radiation tolerance measurements of the highest quality polycrystalline CVD material for a range of proton energies and neutrons obtained with this material with the goal of elucidating the issues that should be addressed for future diamond based detectors. The talk presents the evolution of various semiconductor parameters as a function of dose.

A position sensitive parallel plate (PSPP) stop detector for heavy ions with an active area of 70×76 mm2 has been developed. The cathode is a printed circuit board with parallel strips which form a distri buted constant delay-line. The position resolution is better than 1 mm in the x direction (orthogonal to the strips) and 2 cm in the y direction (along the strips). The anode time resolution is about 300 psec fwhm.