UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 1

LC-TPC R&D LC-TPC R&D LC-TPC R&D LC-TPC R&D

• GEM, MicroMEGAS and MWPC techniquesGEM, MicroMEGAS and MWPC techniques

• Preliminary studiesPreliminary studies– drift velocities, positive ion feedback , aging, ...drift velocities, positive ion feedback , aging, ...

– FeFe5555, Sr, Sr9090 and cosmic ray measurements and cosmic ray measurements

• Mini-TPC construction and magnetic field test programMini-TPC construction and magnetic field test program

M. RonanLBNL Berkeley

and many others not mentionned fromLBNL Berkeley, LAL Orsay, DAPNIA Saclay, IPN Orsay

andLBNL Berkeley, CERN, Karlsruhe, MPI Munich

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 2

Gas Electron Multiplier (GEM)

• High (100 High (100 m) pitch m) pitch small pad response functionsmall pad response function• No ExB effects No ExB effects better resolutionbetter resolution• Direct electron signal Direct electron signal no lossesno losses

• Efficient ion collectionEfficient ion collection no gating grid ?? no gating grid ??

• Easy to build Easy to build dead zones potentially smalldead zones potentially small

• Robust to aging Robust to aging insensitive to LC backgroundsinsensitive to LC backgrounds

• Multi-stage structuresMulti-stage structures large gains (10 large gains (1033-10-1044)) • Low mass construction Low mass construction no wire framesno wire frames

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 3

MicroMEGAS readout structuresMicroMEGAS readout structuresMicroMEGAS readout structuresMicroMEGAS readout structures

• High (50 High (50 m) pitch m) pitch small pad response functionsmall pad response function

• No ExB effects No ExB effects better resolutionbetter resolution

• Direct electron signal Direct electron signal no lossesno losses

• Funnel effect Funnel effect very efficient ion collectionvery efficient ion collection

• Electron amplification independent of the gap to first Electron amplification independent of the gap to first

order order promising dE/dxpromising dE/dx

• Easy to build Easy to build dead zones potentially smalldead zones potentially small

• Robust to aging Robust to aging insensitive to LC backgroundsinsensitive to LC backgrounds

• Good electro-mechanical stability Good electro-mechanical stability large gains (10large gains (1033-10-1044))

• Low mass construction Low mass construction no wire framesno wire frames

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 4

Principle of operationPrinciple of operationPrinciple of operationPrinciple of operation

• VeryVery

Drift space

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 5

Gain StabilityGain StabilityGain StabilityGain Stability

The gain variation is flat (maximal) as a function of the gap around a few 10m

Thus a MicroMEGAS TPC has a good potential for dE/dx measurements.

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 6

Positive ion feed-back Positive ion feed-back - funnel - funnel effecteffect

Positive ion feed-back Positive ion feed-back - funnel - funnel effecteffect

• VeryVeryDue 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 =

Eamplification / Edrift

= S2 / S1

Ions return to the grid: related space charge

effects are suppressed

S1

S2

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 7

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 CF4 as a quencher improves T

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 8

55Fe

0 +2KV 0 - 300 V

Cathodegridwires

90Sr

0 -340 V - 640 V

Cathodemeshanode

2mm 2mm 1cm 50 m 1cm

Small-gap Wire TPC MicroMEGAS TPC

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

•The positive ion feedback doesn ’t depend on magnetic field for the Wire chamber or for MicroMEGAS

Magnetic field testsMagnetic field testsMagnetic field testsMagnetic field tests

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 10

Large Mini-TPC Test ChamberLarge Mini-TPC Test ChamberLarge Mini-TPC Test ChamberLarge Mini-TPC Test Chamber

• Saclay 2 Tesla superconducting (MRI) magnetSaclay 2 Tesla superconducting (MRI) magnet

• STAR Front-End (FEE) electronics STAR Front-End (FEE) electronics Analog waveform Analog waveform

sampling at 10-40 MHz, 1024 channels with amplifier-sampling at 10-40 MHz, 1024 channels with amplifier-

shape, SCA, 10 bit ADC, 512 time slices deep, low shape, SCA, 10 bit ADC, 512 time slices deep, low

noisenoise

• Modular VME data acquisition running VxWorks Modular VME data acquisition running VxWorks Stand-Stand-

alone and MIDAS online systems, VB Pad Monitor, Java alone and MIDAS online systems, VB Pad Monitor, Java

histogramming packagehistogramming package

• Removable detector endplate Removable detector endplate plan to test MicroMEGAS, plan to test MicroMEGAS,

asymmetric Wire chamber, options for spreading signalasymmetric Wire chamber, options for spreading signal

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

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 12

STAR READOUT ELECTRONICS

TEST BENCH

Front end cards

Pulse generator

Mother board

Optical link

VME processor

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

UTA, Jan. 9-11, 2003 M. Ronan LC-TPC R&D 14

CONCLUSIONCONCLUSIONCONCLUSIONCONCLUSION

• 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.