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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