GEM Development in India, test beam analysis and plan for next

test beam

Anand Kumar Dubey for VECC group, Kolkata

CBM Muon detector requirements:

Main issues: The first plane(s) has a high density of

tracks -- detector should be able to cope up with high rate. ~ 10 MHz/cm2

good position resolution Should be radiation resistant Large area detector – modular

arrangement suitable options: micropattern gas detectors such as GEMs, Micromegas, and more recenlty THGEMs.

Multi GEM configurations

For MUCH R&D : we have assembled and tested double and triple GEMs prototypes

Schematic of prototype GEM chamber assembly

GEMS1 2 3

Drift plane (inner side copper plated)

12 x cm 12 cm x 10 mm

Readout PCB

CERN made GEM foils obtained fromArea: 10cm x 10cm

Drift gap: ~7mmInduction gap: 1.5mmTransfer gap: 1mm

Detector fabrication at VECC for Sep08 beam test

Readout plane 256 Pads 8 mm x 3.5 mm

10 ohm Resistors for protection

Outer side of the readout PCB

Detector Biasing Scheme---- symmetric mode of biasing scheme, (i.e. same voltage across each GEM)

3 GEM Signal from a fast preamp

Rms 40 ns~ 40 ns

Test with Fe-55 before shipping to GSIdet01

Tests done using standard NIM electronics at VECC

DeltaV (GEM)ADC

Test with Fe55 + nXYTER using 3GEM

ADC

AD

C

Pulse height from Pad#20

nXYT

ER

ADC

Subt

ract

ed A

DC

Testing of GEM chambers @GSI At the SIS 18 beam line using proton beams of 2.5 GeV/c Aim being : -- to test the response of the detector to charged particles. -- efficiency, cluster size, gain uniformity, rate capability, position resolution and dynamic range study.

-- testing with actual electronics for CBM : nXYTER -- testing with the actual DAQ -- Aug08-- first successful test with n-XYTER(with 64 channels bonded ) + GEM was performed. MIP spectra for 2GEMs and 3 GEMs were obtained. -- Aug-Sep 09, In 2009 a fuller version of nXYTER with all the 128 channels bonded was available. this offered a better configuration for efficiency estimation and also for cluster size estimation.

Sr-90 tests with nXYTER+3GEM

HV 3050V HV 2950V

HV 3150V

Beam Region fired (2008)

Only alternate channels hit, efficiency estimate couldn’t be possible

BEAM SPOT

3-GEM

Main Features: --- more number of days as compared to last test beam --- A new fully connected nXYTER board--- An X--Y movement facility was provided exclusively for the GEM ch. --- A better trigger arrangement for efficiency studies.

--- STS, RICH + Panda (parasitic run with Panda) Summary of data taken: 2 ROCs connected to one half of each detector• small cell size in det1 and large cell size in det 2• one day data: Both large pad sizes --- First Day – Problem with SY1527 calibration --- Movement in both X and Y (Beam spot moved and went away)

Aux signals: 2 days data where Aux from different detectors can be correlated (can be used for position resolution) One day data for good AUX (crucial for eff) Trigger data: One run for 10 minutes

Test beam Aug-Sep: 2009

Readout Board for Test beam Aug-Sep 09

Inside view

Outside view

Two triple GEM chambers were built :

det 01 – with two different pad sizes(shown above)

det02 -- same size pads but with larger induction gap

TEST SETUP – Beamtest 2009

Aug-Sep09 test

the beam profile on

Respective planes

Protons of 2.3 Gev/c

MIP distribution of hit cell

Correlation between GEM1 and GEM2

Position of spots (cell units) from 2 detectors Shown (well-correlated)

ADC distribution of main cell and variation with HV

4 fold increase in ADC for a deltaV(GEM) increase by 50V

PAD multiplicity

• Two back to back detectors similar pad multiplicity..

• No effect of increased induction gap?

(Last day’s data, det2 had low eff, went bad after 3500V)

Depends on beam profile, needs correlating with beam tracker

(Same granularity but different induction gap)

-- no effect of induction gap on the cluster size

Time difference between trigger(aux) and GEM ROC

Offset + Drift time(~150 ns) -- why this large spread ??

Procedure: Select fired GEM cells in 900-1200 nsec after last Aux.

All Aux channels: eff:10% Aux-Channel=2 (4 fold) eff = 71%

---- copied from Sauli’s slides

Efficiency of detector 1 (large pad size)

Using AUX triggerTime window: 900-1200 nsec

Efficiency of detector 1 (large pad size)

Using STS hits as reference

-- slides from Bipasha Bhowmick (Calcultta University, India)

Eff_66

Efficiency

HV= 3650 HV= 3750

Looks like the detector takes some time to become stable,-- for HV scan, maybe 2 hours is perhaps short.

-- slides from Bipasha Bhowmick (Calcultta University, India)

Position resolution (Run #63)

-- slides from Bipasha Bhowmick (Calcultta University, India)

Cosmic Ray test setup at VECC

1. Detector+Ortec_142IH +572A+SCA+CFD2. Detector+Ortec_142IH+TFA+CFD3. Using MANAS coupled to PCI CFD card4. Cosmic + Aux and nXYTER

MiddlePMT(3)

TOP PMT(1) LOWER PMT(2)

GEM(4)

P.AMP TFAMANAS

Translator Board Patch Bus cable DAQ

(PCI CFD Card)

Quad COINCQuad CFD

Ch1

Ch2

Ch3

Ch4

2FOLD OUT

Ch1

Ch2

Ch3

Ch4

IN

IN

IN

INOUT

OUT

IN

IN

3FOLD OUT

4FOLD OUT

NIM – TTL Converter

Trigger to DAQ

1.2 micro sec

Delay

Dual Timer

3FOLD IN

Quad Counter

HV is from CAEN N470

Cosmic Setup and test with MANAS

Pedestal

GEM signal connected to Channel 56 of FEE (MANAS)

After pedestal subtraction -

ADC of Channel 56

No of triggers( from 3 FOLD) = 187 Entries =158 => 85%

Results with MANAS

64 channels for 4 MANAS

Thick GEM (THGEM) fabrication and testing first attempt in India

0.5mm thick double-sided copper clad FR4 material. hole size is 0.3mm and the pitch is 1.2mm. made locally.

THGEM – a thicker variant of GEMs(>0.4mm) with 0.3 mm holes and annular etching region of 0.1 mm Main advantages:-- Can be made from normal PCB’s using simple mechanical drilling technique. It “can” be damn cheap relative to GEMs !

-- is free from the complex operation of framing and stretching unlike thin GEMs -- easy to handle and hence more robust Constraints: position resolution ~ 500 microns

10 cm x 10 cm Obstacles: Accuracy in drilling holes and etching of the annular region

THGEM

0.1 mm 0.5 mm

A closer view of THGEM holes

1.2 mm

The position of the rim is not concentric with the G10 holes and the gap is too little at some places. Lost few boards during tests Fresh Boards ordered – tests going on

“eccentricity” problems

Fe55 Signal from Double THGEM

Not all THGEM boards could give a reasonable energy resolution. --- this could be because of the eccentricity problems. --- we are trying to think of different ways to improve on this.

Preparation for the next beam test

-- Two 3 GEM chambers with following granularity: -- 3 mm x 3 mm 512 pads -- 4 mm x 4 mm 512 pads

-- Get the efficiency problem fully understood using cosmic trigger in lab

-- detector design: The top cover would be sealed via an O-ring instead of the present two component RTV.

Top copperPad area-67*73 Sq mm For 3mm. For 4mm - 88*97 sq mm

Main Features : Both 3 and 4mm square pad sizes Not Staggered (‘09 test beam module) Symmetric Square Pads Multi Layers ( 4) with GND Planes Signal Tracks are distributed in 3 planes

• Reduce the capacitance• Track to Track spacing increases• Reduce Cross talk

Blind Vias for gas integrity Gnd Tracks between Signal Tracks

Bottom copper

Connector with resistors

Top copper

GND Plane

Bottom copper

GND Plane

GND Plane

Connectors for FEBs

Inner 1

Inner 2

33

Chamber PCBS for Test beam 2010

Connectivity Between FEB and ROC

Radiation dose• ROC boards may be affected by this radiation environment• Plan to put the ROC boards 3mt apart from the 0-axis• Detail dose calculation is needed at that point (seems to be falling fast)• The breakdown value of TID is also to be investigated for ROC components

Cable Type• Length of the cable to be known for error free communication• Shielded twisted pair flat type may be a good choice

TID: Total Ionizing Dose at the outer edged of thedetector is around 10krad

Ref : http://cbm-wiki.gsi.de/cgi-bin/viewauth/Radiationstudies/WebHome?CGISESSID=2bce338388a71f099de8d3ca43e0f2b7

10 March 2010 37Physics With FAIR: Indian Perspective,

Susanta K Pal

Tracking station plane

2m

ROC stack

3mt (approx)

Placement of ROC BoardsROC stack

10 March 2010 38Physics With FAIR: Indian Perspective,

Susanta K Pal

Inner 1 Inner-2 Bottom CopperTop copper

Blind vias from inner layers( blue)

Blind vias (red ) to inner layer

2.6 mm square pads

Pads arranged in one block of 32*8=256.

Connected to 300 pin connector.

Tracks - shorter and not closer . can be easily duplicated for

bigger sizes. 40 such FEE Boards for One Slat

of 1mt. Length..

Each block read by 1 FEB with 2/4 n-XYTERs ( 128/64 Channels)

FEBs can be mounted horizontal or vertical

Modular Approach

MUCH PCB design

10 March 2010 39Physics With FAIR: Indian Perspective,

Susanta K Pal

Gas out

Conceptual sketch of Triple GEM chamber module

Gas in

Segmented LV power line/power plane on Detector PCB each power line is feeding 5-FEBs ground plane of LV line is in other layer of PCB

HV

1 mt

10cm

To be decided

LV connector

40 FEBs in one module in 1mt slat with about 10240 channels

10 March 2010 40Physics With FAIR: Indian Perspective,

Susanta K Pal

Chamber PCB4 sq mm pads. 32*32 Array(1024 pads).PCB active area is 135mm *135 mm.Read by 2 chip FEB(256 channels)Basic block=32*8 array. Track lengths are short.

Bottom side

Inner 2 layer

Inner 1 layer

Top side

GND Plane

Sa SAMTEC-300 Pin connectors

2chipFEBs

Chamber PCB with 4 FEBs

Top view with 4 sq mm pads Bottom view –Connectors for FEBs

FEB 1 FEB 4

FEB 2 FEB 3

Bottom view of FEB

Double and Triple GEMs have been assembled at VECC.

Tests performed with radioactive sources as well with proton beams. We are also trying to develop THGEM boards

locally.

Test with proton beams: Double GEM and triple GEMs

coupled to the first prototype of n-XYTER readout chip. – preliminary response looked encouraging. -- charged particle detection efficiency needs to be still higher. investigations underway, using tests with cosmic rays. cross talks issues to be resolved.

Next test beam: two chambers of 3x3 sq. mm 4x4 sq. mm chamber

would require 8 FEBs. May also skip resistor protection

Several layout s of the actual design of the Muon Chamber

are under discussion.

SUMMARY

Thanks For Your Attention

BACKUPS

The readout PCB

only alternate channels connected to nXYTER.

beam

A 2-GEM ASSEMBLY at VECC – A FIRST ATTEMPT

Frame for GEM gluing(0.5 mm in thickness)

10 cm x 10 cm GEM foil

stretching and gluing Jig

GEM & Micromegas : Gain

Slide from (Kondo GNANVO)

Gain stability

MWPC, MSGC & Micromegas

GEM

Readout plane-bottom Copper

68 Pin connectorsfor FEB 1nXGen

68 Pin connectors

for FEB 1nXGen

Resistors for input Protection

ERNI Part no 1148054 No –68Pins

Triple GEM: Test with Fe-55

3GEM: Gain vs. Vgem

Questions remaining from last test beam• Absolute efficiency and HV dependence• Beam intensity dependence • Absolute gain estimate• Uniformity over small zone

New questions:Pad multiplicity/cluster sizePosition resolutionRequired dynamic range before saturation

Induction gap (does it increase cluster size?)