1. 1 Projectile Spectator Detector: Status and Plans A.Ivashkin (INR, Moscow) PSD performance in Be run. Problems and drawbacks. Future steps.

2. 2 PSD – Projectile Spectator Detector Precise measurement of the energy of projectile spectators. Centrality selection (on trigger level) Measurement of event-by-event fluctuations (to reduce N part fluctuations) Reconstruction of the reaction plane Compensating calorimeter Pb/scintillator (4/1) 60 sandwiches in one module Modules 10 x 10 x 120 cm 3 – central part Modules 20 x 20 x 120 cm 3 - outer part 10 longitudinal sections with 10 MAPDs readout PSD in 2011 16 central modules in trigger PSD modules in 2011 Be-run

3. 3 Photo of PSD after full construction (Feb.2012) Front Rear side before FEE installation 44 modules 440 MAPDs and readout channels 17 tons

4. 4 7 Be spectra in PSD at low energies 13 GeV 30 GeV 20 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.

5. Energy in PSD 25.01 – 26.01 27.01 – 28.01 29.01 - 04.02 Temperature Temperature dependent 7 Be peak position Time dependent calibration is needed! A few variants are considered. MAPD gain ~3%/ 0 C

6. 6 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

7. 7 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 0 C difference between summer/winter. ~2 0 C spread during the run. Temperature gradient ~2.5-3 0 C 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 0 C ), 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 0 C ).

8. 8 Modification of PSD trigger signal 60 ns 300 ns MAPD signal M~5x10 4 integrated signal M~10 7 ADC signal 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. Plans: trigger signal after MAPD – fast signal, no problem with time walk and delay. This action requires the replacement of present FEE! New amplifiers, new adders!

9. 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 Control of MAPD voltages

10. Test of one PSD section reveals peak in energy spectrum from cosmic muons 10 Approach in calibration with cosmic muons Can we apply this approach for NA61?

11. 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 Full replacement of FEE?

12. Some inputs for new FEE Number of modules - 44 Number of channels – 440 ( 10 in each module) Geometrical size of one PCB 95x95 mm 2 with holes in the corners. Could be a few PCBs or mezzanine boards. V op of MAPD: 62-68 V Accuracy of V set ~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 5mV- 1.5V. 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 0 C. 12

13. 13 Thank you! The last item to be fixed – remote control of PSD moving table