CEA DSM Dapnia Sédi

• Streamer theoryStreamer theory• Protection schemesProtection schemes• Some ideasSome ideas

Input Protection for Gas Detector Electronic Readout

Frédéric DruilloleFrédéric DruilloleThanks to :Alain Le Coguie, Xavier De La Broïse, Estelle MonmartheThanks to :Alain Le Coguie, Xavier De La Broïse, Estelle Monmarthe

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 2

GEMs and µMegas

• Discharge probability : ~3.10-12 (104)• 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 (104)• 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

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 3

Electric Field in GEM

S1/S2 ~ Eamp/Edrift

S1

2 σ

mesh pitch l

derive

multiplication

Total

transparency of

the grid

S2S2

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 4

Streamer Theory

Im p u rity : d ie lec tr icE in c rea se s ,e lec tro n s in c rea se

Streamer : If the number of electron produced during the avalanche reach 107 ~108 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.

P rim ary av a lan ch e

P h o to n

S eco n d a ry av a lan ch e

Q U E N C H E R

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 5

Streamer consequences

- -- -- -

+ + + ++ + + ++ + + ++ + + ++ + + ++ + + ++ + + +

+ + + ++ + + +

+ + + ++ + + ++ + + ++ + + ++ + + +

+ + + ++ + + ++ + + ++ + + ++ + + ++ + + ++ + + +

+ + + ++ + + +

+ + + ++ + + ++ + + ++ + + ++ + + +

+ + + +

+ + + ++ + + ++ + + ++ + + ++ + + ++ + + +

+ + + ++ + + +

+ + + ++ + + ++ + + ++ + + ++ + + +

+ + + +

N ég a tiv e S tream er

• Avalanche with a critical size• Creation of secondary electrons in the head of the streamer• Creation of a conducting channelCreation of a conducting channel• Could weld the grid on the pad (Permanent short Could weld the grid on the pad (Permanent short circuit)circuit)

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 6

Protection schemes

1. Sparks protection2. Permanent short circuit protection3. High Voltage Components4. supplied diodes (additional noise)5. current injection risk (diode symetry)

1. Sparks protection2. No additional noise3. Unsupplied diode4. No current injection risk

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 7

AC Coupling

• Cac-coupling changes the charge sharing between detector and preamp : Qpreamp = Qdet* Cac-coupling/(Cac-coupling + Cdet)

• Cac-coupling increases crosstalk channel to channel (Cc/Cac-coupling)

•Variation of Cac-coupling changes gain uniformity

• Cac-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

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 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

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 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

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 10

How to connect (preliminary ideas)

• Add components into the plane.• Maintenance and repairs• Unsupplied diodes

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 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)

- Frédéric Druillole - [ Worshop ACTAR CENBG] CEA DSM IRFU Sédi16-06-2008 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.