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

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 13

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

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 16

The suspension mechanism for PMD

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 17

PMD Installation

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 18

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

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 19

PMD trigger timing diagram

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 20

Typical pedestal plot for one FEE chain

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 21

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.

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 23

Implementation in GSTAR

Front view of PMD in GSTAR

PMD with other detectors

PMD

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 24

Offline reconstruction framework

24th. February, 2003 Supriya Das : Junior’s Day, STAR Collaboration Meeting, BNL 25

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.