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Concepts and Statusof the GEM trackers
Evaristo Cisbani / INFN-Rome Sanità Group
SBS - ReviewJLab : 22/Jan/2010
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Outline
• Requirements for tracking
• Conceptual design– GEM technology– Modular approach
• GEM design details– Mechanics– Service components
• Electronics
• Beam tests– Very preliminary results
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Different (e,e’h) experimental configurations
Experiments Luminosity
(s·cm2)-1
Tracking Area
(cm2)
Resolution
Angular
(mrad)
Vertex
(mm)
Momentum
(%)
GMn - GEn up to 7·1037 40x150
and 50x200
< 1 <2 0.5%
GEp(5) up to 8·1038
40x120, 50x200 and
80x300
<0.7
~1.5
~ 1 0.5%
SIDIS up to 2·1037 40x120,
40x150 and 50x200
~ 0.5 ~1 <1%
Maximum reusability: same trackers in different setups
Most demandingMost demanding
HighHighRatesRates
LargeLargeAreaArea
Down to Down to ~ 70 ~ 70 mmspatial resolutionspatial resolution
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Choice of the technology
System RequirementsTracking Technology
Drift MPGD Silicon
High Background Rate (up to):
(low energy and e) 1 MHz/cm2NO MHz/mm2 MHz/mm2
High Resolution (down to):
70 m Achievable 50 m 30 m
Large Area:
from 40×150 to 80×300 cm2YES Doable
Very Expensive
… and modular: reuse in different geometrical configuration
Flexibility in readout geometry and lower spark rate
GEM Ms
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GEM working principle
Ionization
Multiplication
Readout
Multiplication
Multiplication
Readout independent from ionization and multiplication stages
Recent technology: F. Sauli, Nucl. Instrum. Methods A386(1997)531
GEM foil: 50 m Kapton + few m copper on both sides with 70 m holes, 140 m pitch
Strong electrostatic field in the GEM holes
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Rate capability
• Hit rate not an issue
Ar/CO2/CF4 (60/20/20)
Triple GEMPoli Lener, PhD Thesis - Rome 2005
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Aging in COMPASS and LHCb
Altunbas et al.NIMA 515 (2003) 249
Expected max. collected charge in GEp:0.5 mC/mm2/y
Ar/CO2 (70/30)X-ray 8.9 keV
-ray 1.25 MeV Ar/CO2/CF4 (45/15/40)
Alfonsi et al.Nucl. Phys. B 150 (2006) 159
6.3 kHz/mm2 25 kHz/mm2
Use of not-outgassing epoxy
Change in HV
No significant aging expected
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Spatial Resolution in COMPASS: 70 m
COMPASS readout plane (33x33 cm2) and results(analog readout)
C. Altunbas et al.NIMA 490 (2002) 177
70 m resolution achieved by strips centroid
Analog readout required
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Approach: 40x50 cm2 Module
Use the same “basic” module for all trackers types
– Size: 40x50 cm2 active area + 8 mm frame width
• FEM study:
– 3 x GEM foils (double mask technology)
– 2D strip readout (a la COMPASS) - 0.4 mm pitch
– x/y and u/v coordinates
Two exceptions in readout foil:
1. Front Tracker last 2 chambers:• Double segmented readout to reduce
occupancy (Pentchev talk)
2. Coordinate Detector:• 1D strip readout• 1 mm pitch
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Material Budget
Based on the COMPASS GEM• single honeycomb• smaller copper thickness
Minimise material to reduce background (Pentchev talk) and multiple scattering
Quantity Thickness Density X0 Area X0 S-Density m g/cm3 mm Fraction % g/cm2
WindowMylar 1 10 1.39 287 1 0.0035 0.0014
DriftCopper 1 3 8.96 14.3 1 0.0210 0.0027Kapton 1 50 1.42 286 1 0.0175 0.0071
GEM FoilCopper 6 3 8.96 14.3 0.8 0.1007 0.0129Kapton 3 50 1.42 286 0.8 0.0420 0.0170
Grid SpacerG10 3 2000 1.7 194 0.008 0.0247 0.0082
ReadoutCopper-80 1 3 8.96 14.3 0.2 0.0042 0.0005
Copper-350 1 3 8.96 14.3 0.75 0.0157 0.0020Kapton 1 30 1.42 286 0.2 0.0021 0.0009
G10 1 120 1.7 194 1 0.0619 0.0204NoFlu glue 1 60 1.5 200 1 0.0300 0.0090
HoneycombNomex 1 6000 1 13125 1 0.0457 0.6000
G10 2 120 1.7 194 1 0.1237 0.0408Gas
(CO2) 1 9000 1.84E-03 18310 1 0.0492 0.0017Total 0.542 0.725
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Single Module Mechanical Structure
• 3D di Francesco
gas in/out-let detail
cover
drift
3 x transfer+induction
honeycomb
Service frame
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Readout Plane and ZIF extension
Readout along all sides
− not strictly required in x/y
unless additional segmentation
of the readout plane
− weight balance
− unavoidable in diagonal u/v
Extension feeds into ZIF
connectors:
− no soldering on the readout foil
− permit safer bending
Small frame width (8 mm);
minimize dead area
• Require precise cutting around the
ZIF terminalsRui De Oliveira design based on
our preliminary drawing
x/y
In production
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± 45° u/v readout plane and fan-out configuration
uv
1.25% dead area in v plane(in simpler configuration)
Conceptual design
Detailed design in progress
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Detail of the HV distribution
SMD resistor
pads
GEM active area
20 5×20 cm2
HV sectors
Use the HV modules developed by Corradi/Murtas at LNF
• 7 independent HV channels for each
chamber (TBC)
• 3 HV identical doublets + 1 for drift (same on
all GEM foils); each doublet serves one GEM
foil, unused will be cut.
• SMD protection resistors, under the thin
frame
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Assembling tools: GEM foil stretcher
Francesco Noto; inspired by Bencivenni @ al. (LNF)
In production
Uniform and controlled stretching of the foil(30 kg on the load cells)
Load cells
Lo
ad cells
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SBS Tracker Chambers configuration
Modules are composed to form larger
chambers with different sizes Electronics along the borders and
behind the frame (at 90°) – cyan and
blue in drawing
Aluminum support frame around the
chamber (cyan in drawing); dedicated
to each chamber configuration
Front TrackerGeometry
x6
Back Trackers Geometry
X(4+4)
GEp(5) SBS
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GEM Trackers Accounting
Tracker Area
(cm2)
Number of Chambers
Readout Pitch
(mm)
Modules/Chamber
Total Modules
Total Readout Channels
FT 40x150 6 2D
4(x/y) 2(u/v)
0.4 1×3 18 49000
+
13500
ST
+
TT
50x200 4 + 4 2D
2(x/y) 2(u/v)
4×0.4 1×5 20+20 13600
+
13600
CD 80x300 2 1D
y+y
1.0 2×6 24 12000
Last 2 FT modules with strips split in the middle (double segmentation on each site)
ST and TT readout groups 4 strips in GEp(5) with binary readout
Total chs. 101700
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Electronics layout and outer support
Cards and modules are supported by an outer aluminum frame which runs all around the chamber.
Optimization is in progress.
Green = FE card
Cyan = Module frames
Red= Outer Support Frame
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Electronics Components
GEM FEC ADC+VME Controller DAQ
Main features:• Use analog readout APV25 chips (wire-bonded on standard PCB, no
ceramics): proven to work in COMPASS• ZIF connector on the GEM side (no soldering on readout foil) • Minimum electronics components (front-end + VME custom module)• Copper connection between front-end and VME
2D R
eado
ut
Thanks to Michael Böhmer and Igor Konorov from TUMfor very productive discussions on the design of the APV25 based FrontEnd card
Up to 10m
80 mm
49.5
mm
8 mm
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Front End Card
Front End card based on COMPASS original design
The APV25 chip (originally developed for SiD in CMS)
Bus like digital lines (CLOCK, trigger and I2C) & Low Voltages
Single differential line for the ANALOG out
ZIF connectors on the GEM side (no soldering on readout foil); minimize thickness
800 front-end cards needed
ANALOGOUT
Digital IN/OUT+ LV
to the next cardFirst front-end
prototypes under test
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Prototype Design completed
VME64x Custom Controller
VME controller hosts the digitization of the analog signals coming from the front-
end card.
Handle all control signals required by the front end cards (trigger/clock/I2C)
Compliant to the JLab/12 VME64x VITA 41 (VXS) standard
Designed with the possibility to detach the ADC subcomponent to extend FEC-
VME64x distance (expected to be ~7 m)
50 modules required
From the VXS backplane:
1. Trigger L1/L2
2. Synch
3. Clock
4. Busy (OUT)
(duplicated on front panel)
More on DAQ Hansen Talk
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Beam Tests
• Dec/09: preliminary beam test at DESY-II test area (low
intensity electron beam from 1 to 6 GeV) of 2 10x10 cm2
2D prototypes + Gassiplex electronics
– Characterize the small chamber
– Prepare for the full size module test
• March/10: Expected next test/data taking in high lumi at
JLab/PREX experiment (with new electronics)
• Late Spring/10: Planned test of 40x50 cm2 module at
DESY
– Demonstrate the large module works as expected
– Improve design
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DESY beam test in Dec/09: setup
Silicon Tracker+ scintillator fingers
2x 10x10 cm2 GEM prototypes
HV Power Supply
Beam
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DESY beam test in Dec/09 - pedestals
Preliminary!
Gassiplex Readout (not optimized for negative charge), 700 ns shaping time
Baseline subtracted pedestals
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DESY beam test in Dec/09 - event example
Single Event
Cumulated (Beam profile)
Ar/CO2 70%/30%3 GeV Electron Beam
Preliminary!
GEM = 410 VVdrift = 2.5 kV/cmVGEM = 2.5 kV/cmVind = 3.5 kV/cm
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DESY beam test in Dec/09 – x/y correlation
Total Charge in cluster
Maximum charge in strip
GEM = 410 VVdrift = 2.5 kV/cmVGEM = 2.5 kV/cmVind = 3.5 kV/cm
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SBS Front Tracker Project
INFN groups involved in the front tracker development + electronicsBA: Gas systemCA: Mechanics + Test + MC + Slow ControlGE: ElectronicsISS/RM: Prototyping, Test, Digitization + Reconstruction, SiD, Coordination
Collaboration and funding Liyanage Talk
2 0 0 8 2 0 0 9 2 0 1 0 2 0 1 1 2 0 1 2 2 0 1 3Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
Preliminary StudyConceptual Design
Detailed DesignSmall area Tracking Telescope
Fulla Scale PrototypingElectronic Design and Prototyping
Full scale GEM moduleDetailed Design Revised
HV System Design
ProductionTracking Modules
Readout electronicsOther components
IntegrationModules
Modules TestsChambers
Chambers Tests
InstallationCommissioning
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Conclusions
• 3 different trackers required in the SBS experiments;
– support high rate,
– down to ~70 m spatial resolution
– large areas
• GEM technology adopted
– high rate and spatial resolution proven in real experiments
• Modular approach to get large area detectors, and at the same time
to guarantee the already achieved performance
• Detail design almost completed, first 40x50 cm2 module in
production, test in late Spring/10
• Electronics based on APV25; first prototypes under test
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Backup slides
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Choice of the frame width - FEM
Foil stretched with 30 kg weightElectrostatic field of 10x5 kV/cm (1 Pa)Permaglass frame
<40 m distorsion assumed safe
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GEM: Prototype 0 and 1
• First 10x10 prototypes under cosmic test
• Using 70/30 Ar/CO2 gas mixture
• 7 Independent HV levels up to ~ 4000 V
Assembling the GEM chambers parts require a careful quality control at several check points and specific tools for gluing, heating, testing, cleaning
Final 40x50 cm2 module finalized; GEM foils and readout orderedFinal 40x50 cm2 module finalized; GEM foils and readout ordered
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Clean Room Tools and Facilities
HV single foil testing station
Visual inspection back-light board
Assembling the GEM chambers parts require a careful quality control at several check points and specific tools for gluing, heating, testing, cleaning
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Slow Control
HV management is not trivial!
7 HV levels must rump up/down coherently
Low pass filters