FIRST TEST RESULTS FROM A MICROMEGAS LARGE TPC PROTOTYPE P. Colas (CEA Saclay), on behalf of the LC-TPC collaboration Micromegas with resistive anode: previous results The Large Prototype Micromegas panels Data Drift velocity measurement Pad response function Resolution 12/03/2009, Tsukuba 1 P. Colas, Micromegas TPC tests
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FIRST TEST RESULTS FROM A MICROMEGAS LARGE TPC PROTOTYPE P. Colas (CEA Saclay), on behalf of the LC-TPC collaboration Micromegas with resistive anode:
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FIRST TEST RESULTS FROM A MICROMEGAS LARGE TPC
PROTOTYPEP. Colas (CEA Saclay), on behalf of the LC-TPC collaboration
Micromegas with resistive anode: previous resultsThe Large PrototypeMicromegas panelsDataDrift velocity measurementPad response functionResolution
12/03/2009, Tsukuba P. Colas, Micromegas TPC tests 2
D. Arogancia, K. Fujii et al., to appear in NIM A
LC-TPC goal is 200 measurement points on a track, with <130 micron resolution
With Micromegas, signal spread is equal to the avalanche size, 12-14 microns : not enough charge sha-ring at low diffusion even with 1mm pads.Need to share the charge between neighbouring pads to make a barycentre possible and improve resolution.
Also charge sharing saves number of channels ($, W, X°)
Introduction : resistive anode (2)
12/03/2009, Tsukuba P. Colas, Micromegas TPC tests 3
One way to make charge sharing is to make a resistive anode (M.S.Dixit et.al., NIM A518 (2004) 721.) This corresponds to adding a continuous RC circuit on top of the pad plane. Charge density obeys 2D telegraph equation
t
1
RC
2r2
1
r
r
(r, t)RC2t
r2RC4 te
M.S.Dixit and A. Rankin NIM A566 (2006) 281
SIMULATION
MEASUREMENT
Res. foil also provides anti-spark protection
Previous testsMicromegas TPC endplates have been tested in the past1) Berkeley-Orsay-Saclay in cosmics, 2T, 1000 channels (2002-2004)2) MP-TPC at KEK, 1T, 380 channels (June 2005)3) Carleton-Saclay chamber at KEK, 1T, 128 channels with resistive anode
(10/05)
4) Carleton-Saclay chamber at DESY 5T in cosmics, 128 channels with r.a. Now test 1 panel in 1 T at DESY, 1726 channels (T2K electronics)
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Previous results with resistive anodes
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KEK beam test, 2005 DESY 5T cosmic test, 2007
50 micron resolution at short drift distance, with 2mm pads
(was obtained with an AlSi cermet-coated mylar)
eff
dx N
zC
220
The EUDET setupat DESY
See talk by K. Dehmelt
PCMag magnet from KEKCosmic trigger hodoscope from Saclay-KEK-INRBeam trigger from NikhefDummy modules from BonnField cage, gas from DESYEndplate from Cornell
shaper, 100 ns to 2 µs tunable peaking time, full wave sampling by SCA, frequency tunable from 1 to 100 MHz (most data at 25 MHz), 12 bit ADC (rms pedestals 4 to 6 channels)
- Beam data (5 GeV electrons) were taken at several z values by sliding the TPC in the magnet. Beam size was 4mm rms.
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1012/03/2009, Tsukuba P. Colas, Micromegas TPC tests10
• Peaking time: 1 μs• Frequency sampling: 100 MHz
Cosmic ray data sample
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