V. Avdeichikov

Thin detectors for the CHICSi /spl Delta/E-E telescope

A pilot series of 10 /spl mu/m to 15 /spl mu/m thin silicon detectors has been made for the /spl Delta/E-E telescopes in the CHICSi detector system. This system will operate at the CELSIUS heavy ion storage ring in Uppsala, Sweden. /spl Delta/E-E telescopes provide isotope identification and energy determination of fragments from nuclear collisions. The thin detectors are made as p-i-n diodes in thin etched membranes in 280 /spl mu/m thick silicon wafers. The membranes are made with anisotropic etching using 25 wt.% tetramethylammonium hydroxide (TMAH) solution. The etch speed of this solution is very uniform across a wafer. As a result detectors with uniform thickness can be produced. The etch depth varies with less than /spl plusmn/0.3 /spl mu/m over a wafer and the surface microroughness is in the range from 2 to 4 nm. Each detector has a 10.0 mm/spl times/10.0 mm active area on a 10.2 mm/spl times/10.2 mm membrane surrounded by a 1.1 mm wide supporting frame. The detectors have leakage currents in the active area of approximately 0.5 nA at 20 V. The breakdown voltage of the detectors is above 100 V. Evaluation experiments with telescopes consisting of a thin detector in combination with a thick detector have shown excellent isotope separation capabilities. Mass separation of /sup 6/Li and /sup 7/Li is clearly observable.

Systematics in the light response of BGO, CsI(T1) and GSO(Ce) scintillators to charged particles

The light response of a BGO crystal has been measured for particles Z = 1-8, A = 1-16 in the energy range similar to2-60 A MeV. The reaction products are identified by a DeltaE(Si) - E(Sci/PD) telescope, The position of the jump in the value of the signal from the PD at the punch-through points is used to calibrate both the DeltaE(Si) and E(Sci/PD) scales in MeV. The dependence of the light output on the energy E, ion atomic number Z and mass A is parameterized by the power law relation, L(Z, A, E) = a(1)((Z, A))E(a2(Z, A)). The parameters a(1) and a(2) have a smooth dependence on Z for all three crystals. The mass dependence of a(1), a(2) is deduced as a simple analytical expression, The systematics of these parameters is presented for BGO, CsI(Tl) and GSO(Ce) scintillators as a function of Z, A. Calculations of the response function, based on the Murray-Mayer model provide an excellent description of the shape of L(Z, A, E) versus E dependence, but show some deviations in the individual ion normalization constant for the BGO and GSO(Ce) scintillators

Range–energy relation, range straggling and response function of CsI(Tl), BGO and GSO(Ce) scintillators for light ions

Abstract Range–energy relations and range straggling of 1,2,3 H and 4,6 He isotopes with the energy ≈50 A MeV are measured for the CsI(Tl), BGO and GSO(Ce) scintillators with an accuracy better than 0.2% and 5%, respectively. The Si-Sci/PD telescope was exposed to secondary beams from the mass separator ACCULINNA. The experimental technique is based on the registration of the “jump” in the amplitude of the photodiode signal for ions passing through the scintillation crystal. Light response of the scintillators for ions 1⩽ Z ⩽4 is measured in energy range (5–50) A MeV, the results are in good agreement with calculations based on Birks model. The energy loss straggling for particles with Δ E / E =0.01–0.50 and mass up to A =10 in 286 μm Δ E silicon detector is studied and compared with theoretical prescriptions. The results allow a precise absolute calibration of the scintillation crystal and to optimize the particle identification by the Δ E – E (Sci/PD) method.

Energy calibration of CsI(T1) scintillator in pulse-shape identification technique

A batch of 16 CsI(TI) scintillator crystals, supplied by the Bicron Company, has been studied with respect to precise energy calibration in pulse-shape identification technique. The light corresponding to pulse integration within the time interval 1.6-4.5 mus (long gate) and 0.0-4.5 mus (extra-long gate) exhibits a power law relation, L(E, Z, A) a1 (Z, A)Ea2(Z-4), for (1.2.3) H isotopes in the measured energy range 5-150 MeV. For the time interval 0.0-0.60 mus (short gate), a significant deviation from the power law relation is observed, for energy greater than similar to30 MeV. The character of the a2(p)-a2(d) and a2(p)-a2(t) correlations for protons, deuterons and tritons, reveals 3 types of crystals in the batch. These subbatches differ in the value of the extracted parameter a2 for protons, and in the value of the spread of a2 for deuterons and tritons. This may be explained by the difference in the energy dependence of the fast decay time component and/or by the difference in the light output ratio of the fast/slow components. An accuracy well inside 1.0% is achieved in the energy calibration of the CsI(TI) crystals by using the DeltaE(Si) E(CsI(Tl))/PMT method. The batch of 16 CsI(TI) crystals is utilized to measure the correlations of light charged particles produced in E/A = 61 MeV, (36)Arinduced reactions. The preliminary correlation functions for two protons with small relative momenta are presented

Design and commissioning of the GSI pion beam

We describe the design of the secondary pion beam-line installed at the SIS 18Tm synchrotron at GSI, Darmstadt, and discuss the commissioning results. The experiments were performed with proton and C-12 primary beams at several energies using beryllium production targets. Pion yields in a momentum range between 0.4 and 2.8 GeV/c were identified, At the highest primary beam energies of 3.5 GeV for proton and 2.0 A GeV for carbon ions, the latter beam produces the highest low-momentum pion yield while at momenta of 1.5 GeV/c the yields are comparable and at 2.8 GeV/c the proton beam is superior. A momentum resolution of around 0.5% is achieved and the time resolution (a) ranges from 100 to 150 ps, for bombarding rates up to 1.5 MHz

On-beam calibration of the ΔE(Si)–Sci/PD charged particle telescope

Abstract The reaction products emitted in the 14 N (45 A MeV )+( CH 2 / CD 2 ) interactions are identified by a Δ E (Si)– E (Scintillator/Photodiode) telescope by the conventional Δ E – E method. The position of “jumps” in the amplitude of the photodiode signal for ions passing through the scintillator (Sci) is used to calibrate on-beam both the Δ E and the Sci/PD scales in MeV. The accuracy of an absolute energy calibration is better than 2.3% and 1.8% for CsI(Tl) and GSO(Ce) detectors, respectively. It is defined mostly by the correctness of the range-energy relations of ions in the Si and Sci crystals. The light response function, L ( E , Z , A ), of isotopes up to Z ( A )=8(16) in the range of energy ∼(2.5–60) A MeV is extracted. The effects of doping concentration and pulse shaping on the light response are analyzed. The validity of the existing empirical light-energy relations is checked in a wide interval of ion energies and a new power law relation is proposed. Calculations of the response function based on the Murray–Mayer model are found to be in excellent agreement with experimental data for the CsI(Tl) crystal.

CHICSi – a Compact Ultra-High Vacuum Compatible Detector System for Nuclear Reaction Experiments at Storage Rings. I. General Structure, Mechanics and UHV Compatibility

CELSIUS Heavy-Ion Collision Silicon detector system (CHICSi) is a large solid angle, barrel-shaped detector system, housing up to 600 detector telescopes arranged in rotational symmetry around the beam axis. CHICSi measures charged particles and fragments from nuclear reactions. It operates at internal targets of storage rings. In order to optimize space and momentum-space coverage and minimize the low-energy detection limits, CHICSi is designed for use in ultra-high vacuum (UHV, similar to 10(-8) Pa) inside a cluster-jet target chamber. This calls for materials in mechanical support, detectors, Very Large Scale Integrated (VLSI) electronics, connectors, cables and other signal transport devices with very low outgassing. Two auxiliary detector systems, which will operate in coincidence with CHICSi, a heavy-recoil, time-of-flight system (HR-TOF) also placed inside the target chamber and a projectile fragmentation wall (PF-WALL) located outside the chamber, have also been constructed. In total, this combined system registers more than 80% of all charged particles and fragments from typical heavy-ion reactions at energies of a few hundreds of MeV per nucleon

Pion emission in H-2, C-12, Al-27(gamma, pi(+)) reactions at threshold

The first data from MAX-lab in Lund, Sweden on pion production in photonuclear reactions at threshold energies, is presented. The decrease of the total yield of pi+ in gamma + 12C, 27Al reactions below 200 MeV as well as differential, dsigma/dOmega, cross sections follow essentially predictions from an intranuclear cascade model with an attractive potential for pion-nucleus interaction in its simplest form. Double differential, d2sigma/dOmegadT, cross sections at 176 MeV show, however, deviations from the model, which call for refinements of nuclear and Coulomb potentials and possibly also for coherent pion production mechanisms.

The limiting nuclear target fragmentation and the thermodynamical model

Abstract The fragmentation of nuclear targets is considered in the frame of the thermodynamical model. The scaling properties of experimental data concerning backward particles are described.

The CALIFA endcap

D. Cortina-Gil ∗1, H. Alvarez-Pol 1, T. Aumann13, V. Avdeichikov 4, M. Bendel†7, J. Benlliure1, D. Bertini5, A. Bezbakh 11, T. Bloch13, M. Böhmer7, M.J.G. Borge2, J.A. Briz2, P. Cabanelas 1, E. Casarejos 8, M. Carmona Gallardo2, J. Cederk̈all4, L. Chulkov12, M. Dierigl7, D. Di Julio4, G. Ferńandez Maŕ ınez13, E. Fiori10, A. Fomichev 11, D. Galaviz9, R. Gernḧauser7, J. Gerl5, P. Golubev4, M. Golovkov11, D. Gonźalez1, A. Gorshkov 11, A.L. Hartig13, A. Heinz3, M. Heil5, B. Heiss7, A. Ignatov13, B. Jakobsson 4, H.T. Johansson 3, P. Klenze7, D. Köeper5, Th. Kröll13, R. Krücken‡7, S. Krupko11, F. Kurz7, T. Le Bleis7, B. Löher10, E. Nacher 2, T. Nilsson3, A. Perea2, C. Pfeffer7, B. Pietras1, R. Reifarth6, P. Remmels 7, H.B. Rhee13, J. Sanchez del Rio 2, D. Savran10, H. Scheit 13, S. Sidorchuk 11, H. Simon5, O. Tengblad2, P. Teubig9, R. Thies3, J.A. Viĺan8, M. von Schmid13, M. Winkel§7, S. Winkler 7, F. Wamers13, P. Yãnez8, and the RB collaboration. 1Universidad de Santiago de Compostela; 2Instituto Estructura de la Materia, CSIC Madrid; 3Chalmers University of Technology, Göteborg; 4Lund University; 5Helmholtzzentrum für Schwerionenforschung, Darmstadt; 6Goethe University Frankfurt am Main;7Technische Universität München; 8Universidad de Vigo;9Centro de Fı́sica Nuclear da Universidade de Lisboa; 10Extreme Matter Institute and Research Division, GSI; 11Joint Institute for Nuclear Research, Dubna; 12Nuclear Reseach Center, Kurchatov Institute Moscow; 13Technische Universität Darmstadt