1. CEA DSM Dapnia Sédi Streamer theory Streamer theory Protection schemes Protection schemes Some ideas Some ideas Input Protection for Gas Detector Electronic Readout Frédéric Druillole Thanks to :Alain Le Coguie, Xavier De La Broïse, Estelle Monmarthe

2. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 2 GEMs and µMegas Discharge probability : ~3.10 -12 (10 4 ) Performance degradation due to discharge High Gain Energy resolution ~18%FWHM Spatial resolution <~60µm High rate Large scale Discharge probability : ~10 -3 to 10 -9 (10 4 ) No Performance degradation due to discharge High Gain Detection efficiency ~100% Energy resolution ~20%FWHM Spatial resolution <~100µm High rate, weak radiation length Large scale

3. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 3 Electric Field in GEM S1/S2 ~ E amp /E drift S1 2 σ mesh pitch l derive multiplication Total transparency of the grid S2

4. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 4 Streamer Theory Streamer : If the number of electron produced during the avalanche reach 10 7 ~10 8  Divergence of the avalanche goes to a streamer phenomenum. Impurities in the amplication zone could also amplify the Electric field and increase the number of electrons.

5. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 5 Streamer consequences Avalanche with a critical size Creation of secondary electrons in the head of the streamer Creation of a conducting channel Could weld the grid on the pad (Permanent short circuit) Could weld the grid on the pad (Permanent short circuit)

6. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 6 Protection schemes 1.Sparks protection 2.Permanent short circuit protection 3.High Voltage Components 4.supplied diodes (additional noise) 5.current injection risk (diode symetry) 1.Sparks protection 2.No additional noise 3.Unsupplied diode 4.No current injection risk

7. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 7 AC Coupling C ac-coupling changes the charge sharing between detector and preamp : Q preamp = Q det * C ac-coupling /(C ac-coupling + C det ) C ac-coupling increases crosstalk channel to channel (Cc/C ac-coupling ) Variation of C ac-coupling changes gain uniformity C ac-coupling controls the dead time due to sparks  Test must be perform if we need High Voltage components in the case of the second scheme.  Purpose: Try to reduce the size of the protection circuit

8. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 8 How to connect (preliminary ideas) « Fakir » Board : Needles in a hole to pack and to connect pads to the electronic in horizontal plane High density pad new technology to test Insertion force Mechanic tool

9. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 9 How to connect (preliminary ideas) To choose to put different protection depending of the detector type Reduce electronic place in z Good for large pad size z x y

10. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 10 How to connect (preliminary ideas) Add components into the plane. Maintenance and repairs Unsupplied diodes

11. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 11 Connectors To look for high density connectors : (connectics, samtec,HRS,ERNI) Depend on the mechanical structure of the TPC, the available space for the electronic. Need more detector specification Higher Density  Very expensive (2 euros / pads)

12. CEA DSM IRFU Sédi - Frédéric Druillole - [ Worshop ACTAR CENBG] 16-06-2008 12 Conclusion Protection is mandatory for GEMs and µMegas, necessary for wired chamber. Need to test more compact solution to reduce the taken place by protection components Mandatory to produce very clean detector components in term of impurities and also in term of radioactive matter. Protection schemes depends on how we want to handle the Electric field uniformity and the current production for short circuit. Need to study the influence of AC coupling with high density pads and the foreseen performances. Large choice of connectors depending the mechanical architecture, the budget and the maintenance of the system.