ALICE PMD : STATUS REPORT

1
ALICE PMD STATUS REPORT
Comprehensive Review-II (a) Concerns on the
relocation and the extent of changes to the PMD
Request of a document detailing the
modifications. (b) Planning for construction
OUTLINE
? Effect of relocation on PMD ? New position ?
Prototype tests ? Simulation results ? Status
of document ? Experience from STAR PMD ?
Mechanical design, Readout and integration ?
Planning for production ? Summary
2
Upstream material budget
Why relocation?
Material as in Sept. 02
TDR coverage ? 1.8-2.6
New coverage ? 2.3-3.5
3
Forward Detector Zone on the Left Side within
ALICE
PMD finds a position at z-361.5 cm
V0
PMD
Beryllium vacuum chamber
FMD (Si3)
T0
4
Particle density at new location
Pseudorapidity density 8000
About 3-4 times higher than the TDR values
Consequences granularity, gas thickness
Z-361.5cm
? 2.3
5
Effect of Relocation
Comparison of TDR and new design parameters
Parameter TDR Present ? - Coverage 1.8-2.6 2.3
-3.5 Distance from IP -550 cm -361.5 cm Cell
X-section 1 sq.cm 0.23 sq.cm Cell depth 8
mm 5 mm Cell geometry EC-honeycomb EC-honeycomb
No. of photons 4000 4400
6
Prototype fabrication and tests
Extended cathode honeycomb detector
dia. a dia. b Reference Testing
period (insul. Circle) (wire support)
4mm 0.5mm Prototype-4 May 2001
3mm 0.5mm Prototype-3 Sept. 2001
2mm 0.2mm Prototype-2 June 2002
Tests at PS T-10 Beam pion, electron Prototype
256 cells Readout Gassiplex0.7-3 CRAMS
7
Prototype-2 Response to charged particles
Charged particles confined to almost one cell
Design criterion satisfied
8
Prototype-2 Operating voltage
Average efficiency in plateau region
97 Proportional region 1400-1500V
9
Relative gains of cells (Prototype-2)
Proto-2 8 with 5mm deep chamber,
gassiplex0.7 TDR 6, with 8mm deep chamber,
gassiplex1.5 WA98 10 Scint.fibreCCD readout
10
Count Rate Study
Prototype-3
Efficiency and peak pulse height for 100GeV/c
electrons as a function of the incident flux.
Efficiency and peak ADC are stable with count
rate up to 3KHz.
(103 particles/cm2/sec)
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Simulation Results
Physics with PMD mainly governed by Photon
reconstruction efficiency, purity of photon
sample Number of photons on the detector
Detectors/services as in AliRoot in front of PMD
TPC, ITS, FMD, V0, beam pipe Cylindrical
geometry for ITS services Pseudorapidity density
8000 New clustering routine for largely
overlapping clusters Photon-hadron discrimination
only using signal threshold (WA98) (NN method
under development)
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Simulation results Occupancy
Effect of ITS services, under optimization/investi
gation
Without TPC/ITS support/services
Comfortable region for reconstruction ?
2.33.1 with particle density 8000 N? 3100 on
PMD in this region.
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Deviation of tracks from original direction
eta 2.3 3.5
eta 1.8 2.6
AlSS Beam pipe pump
ITS Services (under optimization)
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Efficiency and Purity (preliminary)
Eff/pur close to 60/60 at least in a limited
region of the detector Problem at low ?
efficiency with material overestimated, under
investigation.
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Status of Document
Summary of simulation and prototype tests
Prototype with modified cell geometry works well,
in final shape Photon reconstruction efficiency,
purity of photon sample at least 60/60 in
limited zone of the detector, physics not
affected Further improvement expected after
optimization of geometry of ITS services
(cylindrical conical) Extended coverage of
detector may be useful at lower particle
multiplicity
Effect of Relocation on the Design and
Performance of ALICE PMD
Draft version ready, to be finalized after
optimization of ITS services
16
PMD Fabrication and assembly for STAR Experiment
at RHIC
STAR-PMD design is identical to
ALICE-PMD TDR version
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PMD _at_ STAR

• Basic parameters
• Two planes Veto Pre-shower
• Total no. of cells 82,944
• Distance from vertex 550cm
• PMD is outside STAR magnet
• Gas detector with hexagonal cells
• h Coverage 2.3 3.9
• Cell cross section 1.0 cm2, depth 0.8 cm
• Area of the detector 4.2m2
• Readout Gassiplex 0.7-3 chip C-RAMS
• Unit module 24 X 24 cell rhombus
• Supermodule 4-9 unit modules

PMD front view
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Unit Module Assembly and Quality Control
Steps
1. Assembly of 2 PCBs and honeycomb 2. Wire
insertion with tensioning jig 3. Soldering
4. Visual inspection 5. Resistance
measurement 6.
Repair/rectification, Gluing of holes 7. Wire
cutting 8. Final inspection
continuity check
Technicians from Bhubaneswar, Jammu trained at
Kolkata, jigs/fixtures, raw material
transferred Six assembly stations, with
horizontal laminar flow tables, employed Kolkata
-- 3, Bhubaneswar --1, Jammu 2 Detailed
log-sheet procedure for quality control Each unit
module packed along with its log-sheet for
further use
Average time of assembly reduced from 3 days
to 1.5 days 200 unit modules assembled in less
than six months
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Unit module (Contd)
Visual inspection PCBs before mounting after
soldering after gluing Wire insertion,
tensioning jig and soldering (delicate needle
work)
Resistance meas. for one UM
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Unit Module Testing
Unit module statistics of broken
wires None 109 One 38 Two 23 Three
8 Four 3 Five 2 More 5 Total 188

• Test Parameters
• Pedestal with/without HV (noise pickup study)
• Pedestal RMS for HV from 1200 to 1700V
• Signal from Cosmic
• Sparking point (in HV) if any

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Supermodule assembly and tests

• Tests on a supermodule
• Gas tightness
• Shorting points, if any
• HV conditioning (sparks if any) upto 1600V,
  measuring leakage current
• Pedestal with and without HV

STAR supermodule (SM-8)
If leakage current high, search cell-by-cell for
the fault, disconnect the cell after diagnosis
Difficulty in procuring precision corners
SM-4 test in the lab
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GASSIPLEX Chip Testing
Ped. spread vs Ped. minimum
Gassiplex Chip Testing setup 10K chips tested
within 4 months, manually and with DAQ 3 testing
stations ready
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STAR PMD in Wide Angle Hall
Veto plane
Preshower plane
Engineering run of STAR PMD during 2002-2003 RHIC
running period
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Mechanical Design Layout of ALICE PMD
Two types of unit modules, type A 48 X 96, type
B 96X48 Two types of supermodules, six unit
modules each Four supermodules in each plane,
eight in total Rectangular geometry, HV isolation
at unit module
Design modification for efficient cooling
Unit module A
Modules fabricated in sub-units of 48X12, then
joined to form a Unit Module
? 2.3
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Comparison of TDR and New Layouts
Characteristics TDR Present No. of SMs per
plane 26 4 No. of UMs in a SM 9 6 Shape of
UM Rhombus Rectangular No. of HV
channels 52 48 No. of contagious
cells 5184 4608 Max. no. of cells 269568 2211
84 Detector area 10 sq.m. 2 sq.m. Detector
weight 6000 kg 1000 kg
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Components of Unit Module
4 X 16 cells for one MCM Board
TOP PCB (details)
32-pin connector
Edge frame
Copper honeycomb
Bottom PCB
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Front-End Electronics on the Supermodule

• Al-boundary frame for supermodule
• Backplane fixtures
• PCB Backplane (PC-Bus LV power)
• 32-pin FPC connector
• Kapton Printed Circuit cable
• MCM Board
• Interface connector

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MCM Board
18-pin connector for power, PC-bus
TOP PCB of FEE BOARD
Circuit identical to MANU12 of Muon Tracking
Chambers
To kapton cable on detector
70 mm X 35 mm
BOTTOM PCB of FEE BOARD
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READ OUT
PMD readout identical to that of Tracking
chambers of Dimuon Spectrometer
- The Cluster Read Out Concentrator Unit System
(CROCUS) - The VME Trigger Dispatching Crate
PMD requires 4 CROCUS crates, with optimum data
rate for lt100µs dead time, as in TDR
Trigger
Detector
CROCUS
MCM Board
RORC/Daq
On-board connector
PC-bus/flat cable
DDL link
Mont Dore March 2002
IPN-ORSAY / SEP
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Cooling (conceptual)
using chilled air, input at 15C, output at 20C
Chilled air
Each half separately kept in a plastic
enclosure Chilled air blown from top, passing
thru baffles Flow to be adjusted to maintain
output air temp at 20C
FEE cooling study setup (1/4 scale) Thermal load
of 1 MCM board 1W Prototype 1700mm X 400mm, 441
boards eq.
Temp sensor
Resistor load
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Integration PMD in Mini-Frame
Closed position
Open position
V0
Sufficient space within mini-frame to open the
PMD for servicing by clearing V0
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Pre-production Prototype
Two 48 X 48 cell unit modules to be
fabricated Assembly in a supermodule PCBs for
unit modules Proper layout with 32-pin
connectors (as in real design) PCBs half-size,
fitted with edge frames for gas seal and HV
isolation Readout using 4-chip Gassiplex boards
(from STAR PMD) Connection from Detector to
Gassiplex board kapton cable (similar to actual
, only printed circuit layout changed) Boundary
using Al-channel for gas flow Tests at PS T-10
during July-2003
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Planning for Production
Detector Pre-production prototype July
2003 Production Readiness Review Oct. 2003 Unit
module production Jan-Dec. 2004 Supermodule
assembly Jan-April 2005 Electronics/Readout
(coupled with developments at Orsay/Cagliari/Kolka
ta) Test setup for MCM boards Sept. 2003 Chip
tests Sept. 2004 MCM boards test
complete June 2005 CROCUS modules
complete July 2005 Mechanics, slow control,
gas etc. July 2005
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Summary
Simulation results suggest that relocation does
not affect physics capability of the PMD.
Investigation in progress for improving ITS
services for reduction in upstream
material. Detector prototype in almost final
shape. PPP to be tested in July 2003. Mechanical
design, readout electronics and integration
issues conceptually finalized. Considerable
experience has been gained by the STAR PMD
project. Infrastructure, manpower, testing setup
all available. This should help in meeting the
ALICE PMD milestones.