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24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 1
The STAR Photon Multiplicity DetectorSupriya Das, VECC Kolkata
ForThe STAR PMD Collaboration
Junior’s DaySTAR Collaboration Meeting, BNL - 2003
Outline of the talk: Physics goals Working principle of the detector Design and fabrication aspects Test results Installation DAQ, Trigger and Slow control Simulation and offline reconstruction software Summary
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 2
What does it do?
We measure the multiplicity and spatial distribution of photons (dN/detc) to study:
• The azimuthal anisotropy to determine the reaction plane and flow as the probes of thermalization.
• The event by event fluctuations in global observables like multiplicity and pseudorapidity distributions following critical phenomena near phase boundary.
• The distribution of Nand N/Nch with full azimuthal coverage ( the charged particles info will be taken from FTPC), looking for signals of chiral symmetry restoration (e.g. DCC).
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 3
Recollection from past…
Observation of collective flow Phys. Lett. B403 (1997) 390.•Scaling of particle production: Phys. Lett. B458 (1999) 422.•DCC Search:• Phys. Lett. B420 (1998) 169 • Phys.Rev.C64:011901,2001 Fluctuations: Phys. Rev. C, May 2002
Scintillator + CCD readout detector sitting 21.5 meters from the vertex covering to
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 4
• Two planes CPV+Preshower• Gas detector of hexagonal cells• Cell cross section : 1.0 cm2
• Cell depth : 0.8 cm• Gas used: Ar+CO2 in 70:30• Total number of channels : 82,944• Distance from vertex : 550 cm• coverage: 2.3 – 3.8• Area of the detector : 4.2 m2
CP
V
Pre
Sh
ower
Preshower detector : • 3X0 Pb convertor sandwiched between two planes of segmented gas detectors.
• Charged particle gives single cell signal in both the planes, photon gives restricted shower signal on the second plane
How does it work?
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 5
• One Unit Module has 576 cells.
• Different Supermodules has different number of unit modules (4,6,9 etc.) depending on the position on the detector
• Each plain has 12 Supermodules 144 unit modules
• Supermodules are Gas tight and HV isolated
• Whole detector can be separated in two halves
Different features of PMD
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 6
• Cathode Material: 0.2mm thick copper sheet• Anode wire: 20 m gold plated Tungsten• Anode wire Tension : 25 grams• End caps: standard 1.6 mm thick FR4 PCB
The single cells (shown above) have solder coating on the outer surface. They are assembled on a special jig (shown on the right) and fused together under controlled heat.
Single Cell Design
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 7
Unit ModuleComponents
Gas - 4 board pluggedonto the connector
• Each unit module contains 24x24 array of cells (576)• Size of unit module: Rhombus of side 255 mm• Weight of unit module: 700 gm
Unit Module construction
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 8
STAR PMD Supermodule assembled in Laboratory
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 9
Front-end Electronics
The front-end electronics for processing PMD signals uses 16-channel GASSIPLEX chips.
Gassiplex Chip Testing
10,000 chips have been tested for the full functionality of each channel.
Test board for GASSIPLEX
The chip
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 10
Translator Board:
Needed to shift the logic level of the control signals (CLK, CLR and T/H) from fast NIM to that of the GASSIPLEX chips.
Gas – 4 Boards:• Contains 4 GASSIPLEX boards and necessary discrete components.• Two protection boards with twin series diodes for each channel is also plugged in.
Buffer board:
Needed for the impedance matching of the analog signal and the input impedance of the ADC in C-RAMS.
Different Front end boards
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 11
Tests performed on the Supermodule:
• Gas leak test• HV test • Pedestal with FEE boards• Signal with cosmic muons
Supermodule under test in laboratory
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 12
Test Setup at CERN-PS
June 2002
STAR PMD Supermodule
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Supermodule Test Results IPion beam at 5 GeV/c
# of cells hit = 1.091
Pulse height spectrum
Variation of Efficiency &Pulse height with Voltage
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 14
Test with electron beams
Preshower spectra Calibration curve
Supermodule Test Results II
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 15
PMD in Wide Angle Hall
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The suspension mechanism for PMD
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PMD Installation
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One Unit Module (UM) consists of 24x24 = 576 cells
•One UM has 9 Gas - 4 Boards each with 4 chips (= 64 Multiplexed channels per board)•3 of UM are daisy chained in ONE FEE Chain
• In ONE Chain: 27 Nos. Gas-4 boards i.e. 27x64 = 1728 channels
• In total there are 72 UM per plane.•Two planes: 72 x 2 = 144 Unit Modules.
•Total Number of FEE chains 144/3 = 48
• One C-RAM has 2 Blocks• One Block = 2K Channels and Total 4K Channels/C-RAM• 1728 channels/Block i.e. ONE chain/Block will be used
• Total Nos. of C-RAMS required are 24.
DAQ:Number of Chains and C-RAMS
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PMD trigger timing diagram
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Typical pedestal plot for one FEE chain
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CA
N
BU
S
VME Crate for DAQ(pmd02)
VME Crate for DAQ(pmd01)
NIM Crate for CLK,CLR,T/H
NIM Crate for Trigger Elec.
Motor Movement Control(PMD)
PL-500 LV unit
PL-500 LV unit
VME Crate for HV Control
Network Power SwitchEthernet Hub for DAQ Network
Ethernet Hub for Slow Control Network
PC-Ethernet
PC-CAN-USB
HV Console
CA
N
BU
SC
AN
B
US
CAN BUSCAN BUS
Host PC
To Main DAQ Network
To Main Slow Control Network
Fibre Optic
RACK-1 RACK-2 RACK-3
HV Serial
Slow Control for PMD at STAR
LeCroy 1454 HV Unit
MVME 167B
24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 22
• 10 Supermodules have been installed in the last shut down period.
• 7 FEE chains have been installed and tested.
• Pedestal taken for all seven FEE chains.
• Slow control for Cathode High Voltage, FEE Low Voltage and VME crates have been set up and working.
• Suspension and moving mechanism for PMD has been installed on the east wall of the WAH.
• The stainless steel support plate and lead converter plates have been installed.
Journey so far …
• All LV, HV and signal cables including various optical cables have been laid.
• Gas supply and distribution system has been installed.
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Implementation in GSTAR
Front view of PMD in GSTAR
PMD with other detectors
PMD
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Offline reconstruction framework
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Summary
• Photon Multiplicity Detector is a preshower detector which measuresthe multiplicity and spatial distribution of photons in the forward regionof STAR.
• In combination with the charged particle data from the FTPC, it studies different important physics aspects.
• A major portion of the detector has already been installed.
Looking forward for data from d+Au and p+p runs for detector Calibration and understanding of the different aspects of the detector.
Getting ready for real physics data from Au+Au run.
• The DAQ, Trigger and Slow control systems has been set up.