Micromegas for the central tracker
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Micromegas for the Central Tracker. Sébastien Procureur CEA-Saclay. Micromegas and CLAS12. - 3 double layers of cylindrical MM (Barrel). ~ 4 m². - 3 double layers of flat MM ( Forward ). Micromegas CLAS collaboration meeting, 09 /03/2011 S.Procureur.

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Micromegas for the Central Tracker

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Micromegas for the Central Tracker

Sébastien Procureur

CEA-Saclay


Micromegas and CLAS12

- 3 double layers of cylindrical MM (Barrel)

~ 4 m²

- 3 double layers of flat MM (Forward)

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Build cylindrical detectors with similar performance as flat ones

The MM challenges (Cerchi dell'Inferno)

“Abandon all hope, you who enter here”

Achieve good spatial resolution in a 5 T transverse B field

Build large area detectors (~0.3m²) operating at high

efficiency

Develop off-detector electronics (~1.5 m)

Estimate the spark rate

(and make it ALARA)

Find some space for

detectors &

electronics

Get money

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Mini: 4 mm

128 mm

2 to 4 mm

Cylindrical Micromegas

Make use of the « bulk » technology (2006)

Photoresist border

→ more robust

→ PCB canbethin

Photoresist amplification spacer (~300 µm)

Mesh

PCB with strips

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Cylindrical Micromegas

Performance compared to thick flat MM usingcosmics

Thick detector

Thin detector

→ similar performance as thick detectors

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Spatial resolution in 5 T

X tiles of Barrel Micromegas are sensitive to the Lorentz angle of driftingelectrons

x = h tanθ = h v B / E

h

→ minimize h (but less signal)

→ use heaviergas (but more sparks)

x

→ increase E field (but lowertransparency)

→  ~ 220 µm if  canbelowered down to 20°

Garfield simulation

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Spatial resolution in 5 T

Test to validate Garfield simulation with a Micromegas in dvcsmagnet (Hall B)

→ use of a focused UV laser to extractelectrons

from the drift electrode

Garfield validated,  canbe as low as 20°

P. Konczykowskiet al., NIM A612 (2010), 274

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Large area detectors

Full size Y prototypes have been builtat CERN

→ doubled area compared to COMPASS

→ Cdet ~ 25 nF, Cstripfrom 90 to 120 pF (canbereduced)

50x60 cm²

1400 channels

→ 90% of strips OK (1st proto!)

Scan with Fe55 source

→ ready to buildthemat Saclay

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Electronics

The limitedspacerequires an off-detector electronics → long cables

→ initial cableswere 160 pF/m (FLEX)

→ Iraklifound 70 pF/m (Hitachi)

→ Ccab = 105 pF ~ Cstrip

→ Significanteffect on S/B (~50%)

→ Needs 10 V more to becompensated

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Electronics - recent developments

  • Detector cables: Hitachi 50 pF/m cables expected on March 15th

    • check ability to withstand sparks

    • Goal: 40 pF/m cables

  • Dream: reworked input stage adapted to high detector capacitances up to 200 pF

    • ENC of 2200e for 150 ns peaking time

    • Expected S/N : 30 – 40 depending on gain

  • Test bench: Dream carrier board in place & route

    • Up to 7 Dreams

    • One Dream on a remote board

  • Firmware: in progress

    • Test bench and front-end unit firmware

    • Goal: estimate FPGA resources needed

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


DREAM and test bench schedule

  • February: Dream carrier board place & route started

  • End of March

    • Submission of Dream

      • Backup date: end of April

    • Production of the Dream carrier board

  • April: Dream carrier board in test

  • May: Dream test bench ready

    • Final adjustments for firmware and software

  • June: packaged Dream ready for tests

    • T2-T3 – Dream tests

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies

Activitystarted in 2009

→ simulation: try to relate sparkswith large

energydepositswith Geant4 (Gemc)

→ spark condition: Nel ~ 107 (Raether)

→ Quantitativelyreproduces (few) existing data

→ Explainsgaseffect & givepredictions (bulk)

S. Procureur et al., NIM A621 (2010), 177

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies

Tests at CERN/SPS, October 2009

→ 6 different detectors in 150 GeV pion beams

→ Effect of a 1.5 T  magneticfield

→ 1st test of a MM+GEM detector (D. Neyret)

→ 1 week of data

→ bulk ~ non-bulk

→ No strongeffect of B field

S. Procureur et al., submitted to NIM (Feb. 1st 2011)

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies

Tests atJLab/Hall B, July 2010

→ 1 MM & 1 MM+GEM in FROST setup

→ Effect of a 5 T // magneticfield

→ 2.5 days of data

→ simulation ~ OK

→ 100 with GEM foil

→ x10 with 5 T field

B. Moreno et al., submitted to NIM (Mar. 8th 2011)

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies

Tests at CERN/PS, August 2010

→ 12 detectors in π+ or π-beam

→ beammomentumtunablebetween 0.2 and 3 GeV/c

→ 2 MM+GEM to understandspark rate suppression

→ 2 weeks of data

→ peaks in spark rates withπ+

→ confirms GEM effects

G. Charles et al., submitted to NIM (Feb. 25th 2011)

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate – last mysteries

2 observations cannotbereproduced by the naive simulation

→ effect of the longitudinal 5 T field

→ spark suppression with the MM-GEM detectors

→ stronghint for significanteffect of transverse diffusion

 new spark condition: critical surface charge density

→ explains all effectsseenwith MM-GEM:

→ large suppression withmoderate GEM gains

→ effect of trans. diff. onlyathigh GEM gains

→ change of slopeathigh GEM gain

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Integration

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Forward Tagger with Micromegas?

Project to equip the FMT with central pixels for small angle e- detection

- add ~ 6k channels to the FMT (electronics?)

- add 2-4 MM layers in front of calo

Trackfindingeff > 95% in pFMT

φ

p

Very large background due to Moeller

All hits

Selected hits

z

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Schedule


Build cylindrical detectors with similar performance as flat ones

Conclusion

Achieve good spatial resolution in a 5 T transverse B field

Build large area detectors (~0.3m²) operating at high

efficiency

Develop off-detector electronics (~1.5 m)

Estimate the spark rate

(and make it ALARA)

Find some space for

detectors &

electronics

Get money

MicromegasCLAS collaboration meeting, 09/03/2011 S.Procureur


Additional slides


Working point


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