1. Hans Rudolf Schmidt GSI Darmstadt
The CBM-GEM project for FAIR mainly: Muon Chamber R&D in India (talk of Anand Kumar Dubey, VECC group Kolkata)
Hans Rudolf Schmidt
GSI Darmstadt
RD51 Collaboration Meeting 25. May 2010

2. FAIR
CBM at SIS 100 (start version/30 GeV/c (protons) and SIS 300 (future/90 GeV/c)
systematic exploration of high baryon density matter in A+A collisions from 4-90×A/Z AGeV/c beam energy
explore the QCD phase diagram, chiral symmetry restauration (AGS, SPS, RHIC)
very high rate (fixed target) HI-experiments (> 107 interactions/s), access to rare probes (dileptons, (open) charm....)
CBM Muon Chambers

3. The CBM experiment – electron-hadron setup
Transition
Radiation
Detectors
Electro-
magnetic
Calorimeter
Ring Imaging
Cherenkov
Detector
Silicon
Tracking
System
Projectile
Spectator
Detector
(Calorimeter)
Micro Vertex
Detector
Resistive
Plate
Chambers
(TOF)
Dipole
magnet
CBM Muon Chambers

4. The CBM experiment – muon setup
Tracking
Detector
Muon
detection
System
Silicon
Tracking
System
Projectile
Spectator
Detector
(Calorimeter)
Micro Vertex
Detector
Dipole
magnet
Resistive
Plate
Chambers
(TOF)
CBM Muon Chambers

5. Much Layout Studies in Progess
baseline:
6 GEM stations
3 layers per station
30 x 30 cm2 GEM foils
other layouts under study
In our study we used the compact version of MUCH system consisting of 5 station, each station containing 3 layers. The thickness of the active gas volume was selected at 1cm which is close to realistic case. Three MUCH layer designs were considered in the analysis: the monolithic one, when a layer represents a big monolithic shape segmented by rectangular sectors; and two variants of module design, when each layer consists of modules arranged in rows on both sides of the layer with some overlap region in one dimension. Two values for module size were chosen, namely 25.6x25.6 cm^2 and 51.2x51.2 cm^2. Larger module sizes are restricted for now by construction technology of GEM foils.
35 m2 of GEM stations (300 m2 of foils)
#pads: > 500 k
pad size: 2.8 mm2 and larger (optimization under scrutiny)
CBM Muon Chambers 5 5

6. Particle Rates/Dose LHC/DESY/FAIR
Max. Rates in CBM
MUCH
beam
Neutron fluence in CBM cave
(FLUKA –simulation)
Typical operation scenario: 6 years  neq/cm2
 radiation hardness regime of LHC experiments
CBM MUCH-GEM
10 MHz/cm2
CBM TRD1
100 kHz/cm2
CBM Muon Chambers

7. 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, THGEMs or Straw Tubes
institutions:
VECC, India: R&D in GEM, THGEM – Design & Construction
PNPI, Russia: R&D THGEM, Hybrid Micromegas-GEM – Layout studies
VBLHEP, JINR, Russia: Straw Tubes
GSI/University of Tübingen: GEM-ageing in high rate hadronic environment
CBM Muon Chambers

8. MUCH R&D @ VECC, KalKota we have assembled and tested
double and triple GEM prototypes
based on 10 cm x 10 cm GEM foils.
Idea is to optimize the operating conditions
with 10 cm x 10 cm.
In future we would like to go to 30 x 30 cm2 and later to larger dimensions.
CBM Muon Chambers

9. Schematic of prototype GEM chamber assembly
Readout PCB
GEMS
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
CBM Muon Chambers

10. First Test with Fe55 + nXYTER using 3GEM
Pulse height from Pad#20
nXYTER Peak ADC
baseline (2150) subtraction + “inversion”:
Subtracted ( ADC)
ADC
DeltaV (GEM)
CBM Muon Chambers

11. 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
-- 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.
CBM Muon Chambers

12. Readout Board for Test beam Aug-Sep 09
Two triple GEM chambers were fabricated :
det 01 – with two different pad sizes(shown below)
det same size pads but with larger induction gap
Inside view
Outside view
Inside view
CBM Muon Chambers

13. GEM chambers – Beamtest 2009
CBM Muon Chambers

14. Aug-Sep09 test (with 2.3 GeV/c protons)
pulse height spectra
Correlation between GEM1 and GEM2
CBM Muon Chambers

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

16. Efficiency Measurments (with beam)
effciency too small (<70%) and time dependant...
possible reasons under investigation (extraction method, electronics, readout, etc)
CBM Muon Chambers

17. Cosmic Ray test setup at VECC
Setup for detector efficiency:
1. Detector+Ortec preamp+amp
Using MANAS coupled to
PCI CFD card
3. Using Aux + nXYTER
CBM Muon Chambers

18. 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
0.1 mm
0.5 mm
1.2 mm
“eccentricity” problems
Obstacles: Accuracy in drilling holes
and etching of the annular region
10 cm x 10 cm
0.5mm thick double-sided copper clad FR4 material.
hole size is 0.3mm and the pitch is 1.2mm made locally.
CBM Muon Chambers

19. MuCh Layout Studies: We have to decide upon : Present constraints :
Total number of stations (layers)
Total absorber thickness, total no. of absorbers & the absorber material
Number of stations (2/3) in between two absorbers
Distance between stations & absorber to station distance
TOF station?
arrangement of readout electronics
Present constraints :
Absorber material (Fe, Pb, W )
Layer to layer distance >= 10 cm.
Layer to absorber distance >= 5cm.
CBM Muon Chambers

20. MuCh Layout Options
2 m
CBM Muon Chambers

21. CBM Muon Chambers

22. CBM Muon Chambers

23. Ageing Measurement, High Rate Behaviour
Do we need the investigation of GEM ageing?
Should be ok for ArCO2 mixture (as shown in many x-ray measurments), but we need to test all construction materials for outgassing....
Moreover, we have in CBM a high rate hadronic environment (also many slow protons), i.e., situation might be different.
Do we need to check high rate behavior?
GEMs tested to be ok up to 106 Hz/mm2 (factor 10 above CBM), but again: situation behind first absorber might be more challenging (slow fragments)….
At GSI: We are building a FAIR ageing facility to test construction materials used for gas detector in FAIR experiments. Plan to test GEM ageing in hadron beams.
CBM Muon Chambers

24. SUMMARY Double and Triple GEMs have been assembled at VECC.
Tests performed with radioactive sources as well with
proton beams at GSI.
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.
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
under discussion. Actual size of large GEMs for the final chamber
is still under consideration.
CBM Muon Chambers