The PSD upgrade performance Front-End-Electronics MAPD HV system Temperature stabilization MAPD gain monitoring system Slow control Readout –present and future. - First estimation of the PSD capability for reaction plane measurements at NA61. A.Ivashkin on behalf of INR group 1 NA61/SHINE collaboration meeting, CERN September, 2014

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 PSD modules in 2011 Be-run

1.The PSD cooling system was not working properly (air flow from basement). 1.The temperature control system is not working properly 2. No feed back to MAPD voltage. 3. Long term stability of MAPD gains was not monitored. 4.Raise time of PSD trigger signal was slow – problem with the time-amplitude walk and signal delay in trigger box. 5. Electronics noise was rather small but comparable with MIPs signal. Muon calibration was rather challenging. Necessity of PSD upgrade. E beam =30AGeV Energy in PSD Temperature MAPD gain ~4 %/ 0 C PSD was constructed with the minimum functionality that lead to some problems with PSD have been found during Be-runs: 3

The PSD trigger signal in ns 300 ns MAPD signal M~5x10 4 integrated signal M~10 7 ADC signal Be runs: 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. In :…. trigger signal after MAPD – fast signal, no problem with time walk and delay. 4

Strategy of the PSD upgrade 1. New cooling system with temperature control system. 2. New HV control (readout of real voltages). 3. Monitoring system for the MAPD gains (LED stabilized source). 4. New fast amplifiers for the PSD signals and trigger. 5. Compatibility with new DRS4 readout system. 5. Compatibility with existing readout (old mother boards). 5 Summer 2013 All PSD electronics has been dismounted June 2014 The PSD after upgrade

New FEE for PSD 10 Analog signals +trigger (adder) MAPDs Al-plate+Armaflex LED source HV channels SC connector All 10 MAPDs at Al-plate for cooling. 10 fast amplifiers and HV power sources individually for each photodiode. Two (high/low gain) outputs in each amplifier. Fast analog adder in each module for PSD trigger. Stabilized LED source for MAPD gain monitoring. 6

PELTIER COOLER New scheme of MAPDs cooling and temperature stabilization with Peltier element. Heat sink Temperature sensor Copper heat sink Al plate External TEC controller PSD module electronics Compressed air T s -sink temperature sensor T o -object temperature seensor ToTo TsTs 7

Fully assembled cooling system, FEE, HV and control system for one module. TEC-controller Air-inlet Sink Peltier FEE+MAPD Copper rod In total we have (spares) sets of electronics. 8

Controller for slow control system Originally developed for COMPASS ECAL Can control up to 127 devices (modules). Control the MAPD HV settings. Control the gain monitoring system (stabilized LED sources). Connection with external computer: USB-2.0 or RS-232. Controller for SC New HV distribution system Extremely low power consumption. HV stability – 0.01%. One external power supply ~12 V. Permanent check of HV values. There is feedback to HV! Already tested for a few years! Developer - HVSys Co., Dubna. 9

PSD readout PC HVSys... HVSys flat cable TEC RS485 network (twisted pair) HV & LED control box USB to RS485 Converter LAN USB PSD slow control for temperature, gain, and MAPD HV. HVSys, Dubna USB to RS485 Converter 2 RS485 networks X 22 channels each 10

Cooling system long term (a few days) tests. New MAPDs cooling system based on the Peltier elements provides stable (within C) temperature in each module. Ambient temperature Module temperature (MAPD Al-plate)

FEE - noise source: TEC-controller for Peltier elements. TEC OFF TEC ON one event TEC OFFTEC ON one event effect on pedestal effect on MIP-like signal 12 noise with constant period Time bins

Noise effect at pedestal and MIP-like signal. 13 pedestal TEC OFF Time bins pedestal TEC ON Time bins 100 “ticks” pedestal calculation signal calculation Time bins Due to the periodic structure of noise the effect is minimal, because the noise is the same in pedestal and signal regions. MIP-like

MAPDs gain monitoring system. Light amplitude is controlled by PIN- diode inside with very low temperature dependence. Control of MAPD gain at ~1% level. Based on stabilized LED source. LED amplitude vs time LED amplitude distribution (~30 hours). ~1% Small module 14

Now fast trigger signal is avaialble. 15 Signal shape after adder. Rise time ~10 ns No time walk! No extra delay of trigger signals! Present scheme: MAPD Fast Amp. G=30 Adder

Calibration with cosmic muons. Trigger – sum of adder signals from all modules. At least one section in PSD module must be fired. The spectrum contains the pedestals mainly. Small moduleLarge module ADC [ch] Dedicated event selection is needed! 16

Matching with readout electronics (present and future variants). 17 Shape and amplitude of MAPD signal after amplifier are PMT like ones. Easy to adapt to any readout scheme. Two amplifiers increase the dynamical range of detected energies. (especially important for heavy ion program) Present variant : MAPD Fast Amp. G=30 Signal adapter Slow amp.- integrator CB Future (DRS4) variant : MAPD Fast Amp. G=30 DRS Fast Amp. G=120 DRS (for high energy deposition) (for low energy deposition + muon calibration) 17

Future DRS readout 18 Number of DRS channels: 440 MAPDs in PSD. 440x2 (high/low gain) amplified signals are available. 440x2=880 DRS readout channels for individual MAPD readout. For the pile-up identification the adder signal must be in the time window 8  s. A 6 groups of 8 modules might be digitized in this window. ~ 6 DRS channels with extended time window are required. Cables, connectors, patch-panel?

PSD and flow measurements. Can it be used for the reaction plane reconstruction? 19

First estimation on reaction plane resolution measured with the PSD at NA61 Simulations have been done for - Ar+Sc at 7 energies 12, 18, 29, 39, 75 and 149 AGeV AGeV - and 35 AGeV for NA61 and compared with CBM geometries Reaction plane angle calculations were done in 5 centrality bins: b: 0-2, 2-4, 4-6, 6-8, >8 Corrections of reaction plane angles due to magnetic field and flattering procedure were applied events for were generated with Shield code and transported (all particles) from the target to PSD via Geant4. 20

Au35Au, NA61, 8cm, 17m Au35Au, CBM, cbmroot, hole6cm, 6.5cm, 15m AGeV 18, 29, 39, 75 and 149 AGeV - reaction plane resolution vs b - 80 – 100 degrees. Reaction plane resolution for different systems. 21

Reaction plane resolution at CBM (FAIR) 22 PSD Au-beam energy 2-30 GeV. Magnet field. Reaction plane resolution is consistent with NA61 MC numbers.

Conclusions: 1)New FEE for PSD is installed and tested. 2) The PSD slow control and temperature control systems have been tested. PSD is ready for muon calibration at beam in October ) First simulation of reaction plane determination by the PSD was done. 23 To do PSD slow control is to be implemented in NA61 DCS. Readout by SC of the temperature in PSD modules creates picked-up noise in MAPD amplifiers during readout (a few seconds). Would be nice to synchronize this readout with the spill structure. MAPD gain monitoring system is working in stand-alone mode when PSD is triggered by LED signals. Is it possible to incorporate this trigger to common DAQ?

Thank You 24