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Chicago, January 8, 2002P. Colas - micromegas TPC1 A micromegas TPC prototype in a magnetic field Principle and advantages of a micromegas TPCPrinciple.

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Presentation on theme: "Chicago, January 8, 2002P. Colas - micromegas TPC1 A micromegas TPC prototype in a magnetic field Principle and advantages of a micromegas TPCPrinciple."— Presentation transcript:

1 Chicago, January 8, 2002P. Colas - micromegas TPC1 A micromegas TPC prototype in a magnetic field Principle and advantages of a micromegas TPCPrinciple and advantages of a micromegas TPC Goals and projectsGoals and projects F. Bieser 1, R. Cizeron 2, P. Colas 3, Y. Giomataris 3, J. Jeanjean 2, V. Lepeltier 2, Ph. Rebourgeard 3, M. Ronan 1 (+ many others not mentionned) 1) LBL, 2) LAL Orsay, 3) DAPNIA Saclay

2 Chicago, January 8, 2002P. Colas - micromegas TPC2 Principle of operation VeryVery Drift space

3 Chicago, January 8, 2002P. Colas - micromegas TPC3 Field lines VeryVery « funnel effect » : S1/S2 ~ E amplif / E drift Due to diffusion, when S1/S2 is large, ions are unlikely to follow back the field lines to the drift space. Ions return to the grid: ion feed-back and related space charge effects are suppressed

4 Chicago, January 8, 2002P. Colas - micromegas TPC4 Stationnarity of the gain VeryVery The gain is stationnary (maximal) as a function of the gap around 100  m This gives a micromegas TPC a good potential for dE/dx

5 Chicago, January 8, 2002P. Colas - micromegas TPC5 ADVANTAGES OF MICROMEGAS Very thin amplification gap (50 to 100  m) => fast signalVery thin amplification gap (50 to 100  m) => fast signal Funnel effect => efficient ion collection ( see V. Lepeltier’s talk )Funnel effect => efficient ion collection ( see V. Lepeltier’s talk ) large gains ( )large gains ( ) gain independent of the gap to first order => promising dE/dxgain independent of the gap to first order => promising dE/dx easy to build, dead zones potentially very smalleasy to build, dead zones potentially very small potential robustness to agingpotential robustness to aging

6 Chicago, January 8, 2002P. Colas - micromegas TPC6 ACHIEVEMENTS Construction of a small TPC (30 channels, 16cm drift length), HV tests and observation of mesh signals with 55 Fe and 90 Sr sources Measurements of drift velocities with a laser (see case of Ar-CF 4 ) (P.C., A. Delbart, J. Derré, I. Giomataris, F. Jeanneau, V. Lepeltier, I. Papadopoulos, Ph. Rebourgeard, Vienne conf., Jan 2001) Measurement of ion current Measurement of aging with Ar-CF4 in progress Several ideas to improve the point resolution

7 Chicago, January 8, 2002P. Colas - micromegas TPC7 STAR ELECTRONICS STAR is a channel TPC at RHIC. Started data taking at RHIC in june Records currently 5000-track eventsSTAR is a channel TPC at RHIC. Started data taking at RHIC in june Records currently 5000-track events A front-end board bears 32 channels with a low- noise amplifier, a shaper, a 5 to 20 MHz Switched Capacitor Array with a depth of 512 buckets and a 10-bit ADCA front-end board bears 32 channels with a low- noise amplifier, a shaper, a 5 to 20 MHz Switched Capacitor Array with a depth of 512 buckets and a 10-bit ADC This is perfectly adapted to the test we have in mind (except polarity)This is perfectly adapted to the test we have in mind (except polarity)

8 Chicago, January 8, 2002P. Colas - micromegas TPC8 STAR ELECTRONICS Mike Ronan helped us to install in Saclay a complete data- taking chain including 20 cards of 32 channels (640 channels) extendable to 1152 channels, in September 2000 and March and September FEE MOTHER BOARD DET FIB. OPT VME Pulse generator

9 Chicago, January 8, 2002P. Colas - micromegas TPC9 STAR ELECTRONICS With advice from F. Bieser, we have modified a card to adapt it to both positive and negative polarities, so that we can use it for both a micromegas and a wire TPC.

10 Chicago, January 8, 2002P. Colas - micromegas TPC10 IN PROGRESS Construction of a large TPC (L=0.5m,  =0.45m, 1000 channels) in a 2T magnetic field to work with cosmics. Will be modular (removable endplate, reconnectible electronics) in order to test several schemes. Maybe a smaller chamber to be installed in a test beam to study high rate aspects We have a few 100 channels of FEE available, the DELPHI TPC HV supply, low voltage supplies from DELPHI. Gas and detector HV supplies have been ordered.

11 Chicago, January 8, 2002P. Colas - micromegas TPC11 Layout

12 Chicago, January 8, 2002P. Colas - micromegas TPC12 endplate ssss

13 Chicago, January 8, 2002P. Colas - micromegas TPC13 FEE card support

14 Chicago, January 8, 2002P. Colas - micromegas TPC14 CONCLUSION We plan to take cosmics in a high magnetic field (2T) in a few months from now. This is necessary to confirm the high potentiality of micromegas as an endplate for a new TPC generation.


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