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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

Micromegas for the Central Tracker

Sébastien Procureur

CEA-Saclay


Micromegas and clas12
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


The mm challenges cerchi dell inferno

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Cylindrical micromegas

Mini: 4 mm ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Cylindrical micromegas1
Cylindrical Micromegas ones

Performance compared to thick flat MM usingcosmics

Thick detector

Thin detector

→ similar performance as thick detectors

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Spatial resolution in 5 t
Spatial resolution in 5 T ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Spatial resolution in 5 t1
Spatial resolution in 5 T ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Large area detectors
Large area detectors ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Electronics
Electronics ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Electronics recent developments
Electronics - recent developments ones

  • 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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Dream and test bench schedule
DREAM and test bench schedule ones

  • 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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies
Spark rate studies ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies1
Spark rate studies ones

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)

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies2
Spark rate studies ones

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)

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate studies3
Spark rate studies ones

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)

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Spark rate last mysteries
Spark rate – last mysteries ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Integration
Integration ones

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Forward tagger with micromegas
Forward Tagger with Micromegas? ones

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur


Schedule
Schedule ones


Conclusion

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

Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur




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