1. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D1 LC-TPC R&D GEM, MicroMEGAS and MWPC techniquesGEM, MicroMEGAS and MWPC techniques Preliminary studiesPreliminary studies –drift velocities, positive ion feedback, aging,... –Fe 55, Sr 90 and cosmic ray measurements Mini-TPC construction and magnetic field test programMini-TPC construction and magnetic field test program M. Ronan LBNL Berkeley and many others not mentionned from LBNL Berkeley, LAL Orsay, DAPNIA Saclay, IPN Orsay and LBNL Berkeley, CERN, Karlsruhe, MPI Munich

2. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D2 Gas Electron Multiplier (GEM) High (100  m) pitch small pad response functionHigh (100  m) pitch small pad response function No ExB effects better resolutionNo ExB effects better resolution Direct electron signal no lossesDirect electron signal no losses Efficient ion collection no gating grid ??Efficient ion collection no gating grid ?? Easy to build dead zones potentially smallEasy to build dead zones potentially small Robust to aging insensitive to LC backgroundsRobust to aging insensitive to LC backgrounds Multi-stage structures large gains (10 3 -10 4 )Multi-stage structures large gains (10 3 -10 4 ) Low mass construction no wire framesLow mass construction no wire frames

3. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D3 MicroMEGAS readout structures High (50  m) pitch small pad response functionHigh (50  m) pitch small pad response function No ExB effects better resolutionNo ExB effects better resolution Direct electron signal no lossesDirect electron signal no losses Funnel effect very efficient ion collectionFunnel effect very efficient ion collection Electron amplification independent of the gap to first order promising dE/dxElectron amplification independent of the gap to first order promising dE/dx Easy to build dead zones potentially smallEasy to build dead zones potentially small Robust to aging insensitive to LC backgroundsRobust to aging insensitive to LC backgrounds Good electro-mechanical stability large gains (10 3 -10 4 )Good electro-mechanical stability large gains (10 3 -10 4 ) Low mass construction no wire framesLow mass construction no wire frames

4. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D4 Principle of operation VeryVery Drift space

5. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D5 Gain Stability The gain variation is flat (maximal) as a function of the gap around a few 10  m Thus a MicroMEGAS TPC has a good potential for dE/dx measurements.

6. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D6 Positive ion feed-back - funnel effect VeryVery Due to diffusion, when S2 small wrt avalanche cloud size, the positive ions are unlikely to follow the field lines back into the drift space. Ideal feedback = E amplification / E drift = S2 / S1 Ions return to the grid: related space charge effects are suppressed S1 S2

7. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D7 Gas studies Drift properties: to obtain a high drift velocity plateau at low E-field, an Ar- dominated carrier is required Hydrogen should be avoided because of neutron background Use of CF 4 as a quencher improves  T

8. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D8 55 Fe 0 +2KV 0 - 300 V Cathodegrid wires 90 Sr 0 -340 V - 640 V Cathodemesh anode 2mm 2mm 1cm 50  m 1cm Small-gap Wire TPC MicroMEGAS TPC

9. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D9 The positive ion feedback doesn ’t depend on magnetic field for the Wire chamber or for MicroMEGAS Magnetic field tests

10. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D10 Large Mini-TPC Test Chamber Saclay 2 Tesla superconducting (MRI) magnetSaclay 2 Tesla superconducting (MRI) magnet STAR Front-End (FEE) electronics Analog waveform sampling at 10-40 MHz, 1024 channels with amplifier- shape, SCA, 10 bit ADC, 512 time slices deep, low noiseSTAR Front-End (FEE) electronics Analog waveform sampling at 10-40 MHz, 1024 channels with amplifier- shape, SCA, 10 bit ADC, 512 time slices deep, low noise Modular VME data acquisition running VxWorks Stand- alone and MIDAS online systems, VB Pad Monitor, Java histogramming packageModular VME data acquisition running VxWorks Stand- alone and MIDAS online systems, VB Pad Monitor, Java histogramming package Removable detector endplate plan to test MicroMEGAS, asymmetric Wire chamber, options for spreading signalRemovable detector endplate plan to test MicroMEGAS, asymmetric Wire chamber, options for spreading signal

11. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D11

12. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D12 STAR READOUT ELECTRONICS TEST BENCH Front end cards Pulse generator Mother board Optical link VME processor

13. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D13

14. UTA, Jan. 9-11, 2003M. Ronan LC-TPC R&D14 CONCLUSION Amplification, drift velocities, diffusion, aging, positive ion feedback,... are being studied for GEM, MicroMEGAS and MWPC TPC ’s operating with different gases and readout technologies. New results for a GEM TPC running on cosmic rays without a magnetic field. First operation of a MicroMEGAS TPC in a magnetic field. Strong multi-institution collaborations building GEM, MicroMEGAS and asymmetric Wire chamber Mini-TPCs for cosmic ray tests in high magnetic fields.