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 Readout PCB GEMS 1 2 3 CERN made GEM foils obtained from Area: 10cm x 10cm Drift gap: ~7mm Induction gap: 1.5mm Transfer gap: 1mm Drift plane (inner side copper plated) 12 x cm 12 cm x 10 mm

Detector fabrication at VECC for Sep08 beam test Readout plane 256 Pads 8 mm x 3.5 mm Outer side of the readout PCB 10 ohm Resistors for protection

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 GSI det01 Tests done using standard NIM electronics at VECC

Test with Fe55 + nXYTER using 3GEM Pulse height from Pad#20 nXYTER ADC ADC Subtracted ADC ADC DeltaV (GEM) ADC

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 3150V HV 3050V HV 2950V

Beam Region fired (2008) BEAM SPOT 3-GEM BEAM SPOT Only alternate channels hit, efficiency estimate couldn’t be possible

Test beam Aug-Sep: 2009 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

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 Protons of 2.3 Gev/c the beam profile on Respective planes

MIP distribution of hit cell Correlation between GEM1 and GEM2 Position of spots (cell units) from 2 detectors Shown (well-correlated) MIP distribution of hit cell

ADC distribution of main cell and variation with HV 4 fold increase in ADC for a deltaV(GEM) increase by 50V

PAD multiplicity -- no effect of induction gap on the cluster size (Same granularity but different induction gap) 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 -- no effect of induction gap on the cluster size

Time difference between trigger(aux) and GEM ROC Procedure: Select fired GEM cells in 900-1200 nsec after last Aux. All Aux channels: eff:10% Aux-Channel=2 (4 fold) eff = 71% Offset + Drift time(~150 ns) -- why this large spread ?? ---- copied from Sauli’s slides

Efficiency of detector 1 (large pad size) Using AUX trigger Time window: 900-1200 nsec

Efficiency of detector 1 (large pad size) Using STS hits as reference -- slides from Bipasha Bhowmick (Calcultta University, India)

Efficiency Eff_66 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+CFD Detector+Ortec_142IH+TFA+CFD 3. Using MANAS coupled to PCI CFD card 4. Cosmic + Aux and nXYTER

Cosmic Setup and test with MANAS TOP PMT(1) LOWER PMT(2) IN 2FOLD OUT IN Ch1 OUT Ch1 GEM(4) IN 3FOLD OUT Middle PMT(3) IN Ch2 OUT Ch2 IN 4FOLD OUT Ch3 IN Ch3 Ch4 Ch4 Quad CFD Quad COINC P.AMP MANAS 3FOLD IN TFA 1.2 micro sec Delay Dual Timer Quad Counter NIM – TTL Converter Translator Board DAQ (PCI CFD Card) Patch Bus cable Trigger to DAQ HV is from CAEN N470

Results with MANAS GEM signal connected to Channel 56 of FEE (MANAS) Pedestal 64 channels for 4 MANAS No of triggers( from 3 FOLD) = 187 Entries =158 => 85% After pedestal subtraction -ADC of Channel 56

Thick GEM (THGEM) fabrication and testing first attempt in India 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 0.5mm thick double-sided copper clad FR4 material. hole size is 0.3mm and the pitch is 1.2mm. made locally.

THGEM

A closer view of THGEM holes “eccentricity” problems 0.1 mm 0.5 mm 1.2 mm “eccentricity” problems 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

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.

Chamber PCBS for Test beam 2010 Bottom copper Connector with resistors Top copper GND Plane Connectors for FEBs Inner 1 Inner 2 Top copper Pad 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

Connectivity Between FEB and ROC TID: Total Ionizing Dose at the outer edged of the detector is around 10krad 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 Ref : http://cbm-wiki.gsi.de/cgi-bin/viewauth/Radiationstudies/WebHome?CGISESSID=2bce338388a71f099de8d3ca43e0f2b7 10 March 2010 Physics With FAIR: Indian Perspective, Susanta K Pal

Placement of ROC Boards ROC stack ROC stack Tracking station plane 3mt (approx) 2m 10 March 2010 Physics With FAIR: Indian Perspective, Susanta K Pal

Physics With FAIR: Indian Perspective, Susanta K Pal MUCH PCB design Inner 1 Inner-2 Bottom Copper Top copper Blind vias from inner layers( blue) Blind vias (red ) to inner layer 2.6 mm square pads Modular Approach 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 10 March 2010 Physics With FAIR: Indian Perspective, Susanta K Pal

Physics With FAIR: Indian Perspective, Susanta K Pal Conceptual sketch of Triple GEM chamber module 1 mt Gas out HV 10cm Gas in To be decided LV connector 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 40 FEBs in one module in 1mt slat with about 10240 channels 10 March 2010 Physics With FAIR: Indian Perspective, Susanta K Pal

Chamber PCB Top side Inner 1 layer Bottom side GND Plane Inner 2 layer 4 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. Top side Inner 1 layer Bottom side GND Plane Inner 2 layer Sa SAMTEC-300 Pin connectors 2chipFEBs

Chamber PCB with 4 FEBs FEB 1 FEB 4 FEB 2 FEB 3 Bottom view of FEB Top view with 4 sq mm pads Bottom view –Connectors for FEBs

SUMMARY We are also trying to develop THGEM boards locally. 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.

Thanks For Your Attention

BACKUPS

The readout PCB beam only alternate channels connected to nXYTER. This was because the first prototype of nxyter had this bonding problem. beam

A 2-GEM ASSEMBLY at VECC – A FIRST ATTEMPT 10 cm x 10 cm GEM foil Frame for GEM gluing (0.5 mm in thickness) stretching and gluing Jig In the direction towards making a GEM based prototype, we started with assembling a double GEM

Slide from (Kondo GNANVO) GEM & Micromegas : Gain Gain stability GEM MWPC, MSGC & Micromegas Slide from (Kondo GNANVO)

Readout plane-bottom Copper ERNI Part no 114805 4 No –68Pins 68 Pin connectors for FEB 1nXGen Resistors for input Protection 68 Pin connectors for FEB 1nXGen

Triple GEM: Test with Fe-55 3GEM: Gain vs. Vgem

Pad multiplicity/cluster size Position resolution 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 size Position resolution Required dynamic range before saturation Induction gap (does it increase cluster size?)