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Projectile Spectator Detector: Status and Plans A.Ivashkin (INR, Moscow) • PSD performance in Be run. • Problems and drawbacks. • Future steps. 1 PSD – Projectile Spectator Detector Compensating calorimeter PSD in 2011 •Pb/scintillator (4/1) 60 sandwiches in one module •Modules 10 x 10 x 120 cm3 – central part • Modules 20 x 20 x 120 cm3outer part • 10 longitudinal sections with 10 MAPDs readout Precise measurement of the energy of projectile spectators. •Centrality selection (on trigger level) • Measurement of event-by-event fluctuations (to reduce Npart fluctuations) • Reconstruction of the reaction plane PSD modules in 2011 Be-run 16 central modules in trigger 2 Photo of PSD after full construction (Feb.2012) Rear side Front before FEE installation 44 modules 440 MAPDs and readout channels 17 tons 3 7Be spectra in PSD at low energies 13 GeV 20 GeV 30 GeV Good identification of beam ions. But the resolution is still ~20% worse of expected numbers. Needs the improvement of calibration. Contribution of electronic noise is maximum at low energies. 4 Temperature dependent 7Be peak position Energy in PSD 25.01 – 26.01 27.01 – 28.01 29.01 - 04.02 MAPD gain ~3%/0C Temperature Time dependent calibration is needed! A few variants are considered. What actions are needed for the improvement of PSD performance? 1. Improvement of temperature stabilization 2. Modification of trigger signal 3. Control on MAPD’s voltages 4. Full upgrade of readout 5. New approach in calibration with cosmic muons 6 Temperature stabilization At present: The flow of underground air trough the distributor box and pipes in each PSD module. Problems: • the temperature of underground air is not constant. • ~6 0C difference between summer/winter. • ~2 0C spread during the run. • Temperature gradient ~2.5-3 0C between top/down modules due to different length of pipes and air pressure in modules. What can be done: 1. Improvement of present cooling system: Chiller before the distributor box (accuracy ~1 0C ), optimization of the pressure and pipe length for air. (The simplest and cheapest solution) 2. Full modification – installation of Peltier elements in each module (accuracy ~0.1 0C ). 7 Modification of PSD trigger signal MAPD signal M~5x104 integrated signal M~107 ADC signal 300 ns 60 ns Plans: trigger signal after MAPD – fast signal, no problem with time walk and delay. At present: the PSD trigger signal comes after integrators with rise time ~60 ns: rather slow and large time-amplitude walk. Needs careful adjustment for each beam energy and each beam ion. This action requires the replacement of present FEE! New amplifiers, new adders! 8 Control of MAPD voltages • • MAPD voltages must be stable within 0.05V accuracy. At present two power sources in one chain (reference and variable) are used for all PSD modules. • What can be done: 1. Slow control of output voltages after power sources. – Only 2 numbers, Rather simple solution. But the real voltage at MAPD would be not measured. Or 2. Control of voltages in each individual MAPD. Installation of ADC in each of 440 MAPDs. Full upgrade of slow control, replacement of FEE. 9 Approach in calibration with cosmic muons Test of one PSD section reveals peak in energy spectrum from cosmic muons Can we apply this approach for NA61? 10 Full replacement of FEE? • Modification of trigger or control of individual MAPD voltages requires full replacement of PSD FEE. • In this case one needs to develop new amplifiers, adders, slow control (hardware and software). • The readout would be done in another way (DRS, TRB3…) • The resources and manpower are needed. • In present FEE one needs to repair two sections in one outer modules (short circuit during intervention), to repair one adder in central module (result of power cut at CERN). Description of present FEE in: https://twiki.cern.ch/twiki/bin/viewauth/NA61/PsdHardware 11 Some inputs for new FEE • • • • • • • • • • Number of modules - 44 Number of channels – 440 ( 10 in each module) Geometrical size of one PCB 95x95 mm2 with holes in the corners. Could be a few PCBs or mezzanine boards. Vop of MAPD: 62-68 V Accuracy of Vset ~0.05V Signal – rise time 8-10 ns, full length 60 ns. Slow control must write and readout the MAPD voltages. Amplifier: gain~100-120, bandwidth~20 MHz, dynamical range 5mV1.5V. Two outputs – 9/10 parts for DRS and 1/10 for adder. Would be nice to have the gain switch from 100-120 to 20-30. 10 amplifiers in one module. Analog adder – 10 channels with weight ~1. Output – LEMO connector. The electronic must ensure the gain/amplitude stability of about 1% in the temperature range 15-30 0C. 12 The last item to be fixed – remote control of PSD moving table Thank you! 13