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Status of P rojectile S pectator D etector A.Ivashkin INR , Moscow

I. Introduction to PSD. II. Design and readout. III. Estimation of radiation dose. IV. Results of beam test of PSD prototype. V. Comparision with simulation. VI. Summary. Status of P rojectile S pectator D etector A.Ivashkin INR , Moscow. PSD in CBM setup.

rafael-vance
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Status of P rojectile S pectator D etector A.Ivashkin INR , Moscow

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  1. I.Introduction to PSD. II. Design and readout. III. Estimation of radiation dose. IV. Results of beam test of PSD prototype. V. Comparision with simulation. VI. Summary. Status of Projectile Spectator DetectorA.IvashkinINR , Moscow

  2. PSD in CBM setup. Very Forward Hadron Calorimeter for detection of projectile spectators PSD Experimental intention: 1. Measurement of centrality: b~ A - Nspect , selection of centrality at trigger level; 2. Measurement of event-by-event fluctuations to exclude the fluctuation of participants;3. Reconstruction of the reaction plane; 4. Monitor of beam intensity by detecting the neutrons from electromagnetic dissociation .

  3. spectator spots at Z=15m Eau=15 AGeV Optional Beam hole Full beam intensity.Minimum 107 modules. X Z Schematic view of PSD configuration. Low beam intensity. Detection of fragments. (25 modules)

  4. Design and readout Modular Lead/Scintillator sandwich compensating calorimeter. Sampling ratio Pb:Scint=4:1. Expectation:For thickness δPb=16 mm and δScint=4 mm σE/E ~ 50%/√E . Conception Light readout– WLS-fibers for uniform light collection. Signal readout – Micropixel APD (MAPD) to avoid nuclear counter effect, detection of a few photons signal, compactness, low cost. Longitudinal segmentation – for permanent calibration of scintillators in radiation hard conditions, rejection of secondary particles. Modular design – transverse uniformity of resolution, flexible geometry, simplicity.

  5. Structure of PSD module. MAPDs and amplifiers. • 60 lead/scintillator sandwiches. • 10 longitudinal sections. • 6 WLS-fiber/MAPD. • 10 MAPDs/module. • 10 Amplifiers with gain~40.

  6. Properties of selected MAPDs working in Geiger mode (deep micro-well type). Production: Dubna-Mikron Co. (Z.Sadygov). Active area: 3x3 mm2. Number of pixels: 104/mm2. Photon detection efficiency:~20%. Gain: 5-6 x104. Working voltage: 130-140V. Pixel density is crucial for the calorimetry!

  7. pixels Linearity of MAPD response. Depends on number of pixels analytical formula 3x3 mm2 MAPD with pixel density 104/mm2 has a linear response up to (1-2)x104 ph.el. (σ2 ~ Nph.el. in linear case ) New generation of micropixel APD is produced by Zecotec.com (Singapore). Number of pixel up to 40000/mm2. Gain ~ few x 105 . Single electron noise ~ 1 MHz/mm2 . Voltage < 100 V. Active area up to 5x5 mm2. High stability. Dependence of signal width (σ2) on signal amplitude Nph.el. (both in photoelectrons).

  8. Radiation dose map for PSD. Neutron flux at MAPD position(rear side of calorimeter). UrQMD generator +GEANT3of 104 Au-Au events at 25 GeV ~5 MRad/(12 months of CBM run) Beam hole Magnet ON. Proton and neutron spots are separated. Assuming 3x1014 events/year the flux ~ 1011 neutrons/cm2/year is expected. (~200 times less of CMS ECAL Hamamatsu 5x5 mm2 APDs ) ~2 times light yield drop. No changes in uniformity and resolution. Fluka simulation with fragmentation is highly desired!

  9. Radiation hardness test of MAPDs with 28 MeV positrons and flux 8x1010 /cm2 (PSI test-2006) No significant changes in gain and PDE were found.Dark counts (noise) increased strongly. New MAPDs from Zecotek.com with dark current ~1 MHz/mm2 survived after one order more dose (PSI-2007 beam test, private communication). Results will be published soon. 28 MeV positron flux is equivalent to 20 times less flux of 1 MeV neutrons. MAPDs survive after dose ~3x1010 neutrons/cm2 (a few months of CBM run). Much better performance is expected. Dubna MAPDsPSI-2006 test.

  10. Module assembling at INR.

  11. PSD supermodule beam test at NA61 beam line (Sept. 27 – October 1, 2007) Program of measurements: -modules calibration with muon beam; -study of the response and energy resolution of the PSD on hadron beams 20, 30, 40, 80, 158 GeV/c; -study of the PSD compesation; -study of APDs long term stability

  12. Calibration of modules by 75 GeV muon beam (response of each section in module) l.y~2ph.e/MeV Run 5362 mod 1

  13. Deposited energy in 9 modules:simulationand experiment

  14. muons hadrons positrons Performance of calorimeter. Energy spectrum in first section of module for mixed 30 GeV beam of pions, positrons and muons. PID and rejection of secondary particles are possible. Energy resolution of 3x3 prototype: stochastic term ~ 55% constant term ~ 3.7% Lateral shower leakage 16% is introduced in parameterization*: stochastic term ~ 54% constant term ~ 1.9% *NIM A308(1991)481-508

  15. Energy resolution for 9 (3 x 3 area) modules (MC simulation GEANT3+Geisha) σ(E)/(E) = 51.6%/√E(GeV)+3.2% Rather good agreement with experiment σ(E)/(E) = 48.7%/√E(GeV)+1.4% +16%/ 4√E(GeV) Shower leak

  16. How is important the constant term in energy resolution of PSD? • The PSD has very specific task of measurement of many particles with the same energy. • The constant term in energy resolution is essential only for energy measurement of single particle. • It is not important in case of measurement of total energy from many particles with the same energy. • The reason is dependence of energy resolution for N spectators as (1/sqrt(N)x(resolution for single particle):

  17. Summary. • The prototype of modular longitudinally segmented PSD calorimeter was developed and assembled. The readout is done by micropixel APDs working in Geiger mode. • The prototype of 9 modules was tested in hadron beam at CERN. • The possibility of PSD calibration with modules was demonstrated. • Energy resolution was measured for 5 beam energies and equals to 54% (stochastic term) with constant term ~ 1.9%. • The test of larger size prototype of 5x5 modules is planed. • The measurement of transverse uniformity of energy resolution is requested. • Radiation hardness of PSD modules and MAPDs need to be determined. • Long-term stability and reliability of MAPDs are to be studied.

  18. Thank you!

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