Micromegas for the Central Tracker

Sébastien Procureur CEA-Saclay

Micromegas and CLAS12

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

- 3 double layers of cylindrical MM (Barrel)- 3 double layers of cylindrical MM (Barrel)- 3 double layers of flat MM (Forward)- 3 double layers of flat MM (Forward) ~ 4 m²~ 4 m²

The MM challenges (Cerchi dell'Inferno)

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

“Abandon all hope, you who enter here”

Cylindrical MicromegasMake use of the « bulk » technology (2006)Make use of the « bulk » technology (2006)

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

2 to 4 mm 128 mMini: 4 mm

Mesh

Photoresist border

Photoresist amplification spacer (~300 µm)

PCB with strips

→ → more robustmore robust

→ → PCB can be thinPCB can be thin

Cylindrical MicromegasPerformance compared to thick flat MM using cosmicsPerformance compared to thick flat MM using cosmics

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

→ → similar performance as thick detectorssimilar performance as thick detectors

Thick detector Thin detector

Spatial resolution in 5 TX tiles of Barrel Micromegas are sensitive to the Lorentz angle of drifting electronsX tiles of Barrel Micromegas are sensitive to the Lorentz angle of drifting electrons

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

x = h tanθ = h v B / E

x

h → → minimize h (but less signal)minimize h (but less signal)

→ → use heavier gas (but more sparks)use heavier gas (but more sparks)

→ → increase E field (but lower transparency)increase E field (but lower transparency)

Garfield simulation

→ → ~ 220 µm if ~ 220 µm if can be lowered down to 20° can be lowered down to 20°

Spatial resolution in 5 TTest to validate Garfield simulation with a Micromegas in dvcs magnet (Hall B)Test to validate Garfield simulation with a Micromegas in dvcs magnet (Hall B)

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

Garfield validated, Garfield validated, can be as low as 20° can be as low as 20°

→ → use of a focused UV laser to extract electrons use of a focused UV laser to extract electrons from the drift electrodefrom the drift electrode

P. Konczykowski P. Konczykowski et al.et al., NIM A612 (2010), 274, NIM A612 (2010), 274

Large area detectorsFull size Y prototypes have been built at CERNFull size Y prototypes have been built at CERN

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

→ → doubled area compared to COMPASSdoubled area compared to COMPASS

50x60 cm²

1400 channels→ → CCdetdet ~ 25 nF, C ~ 25 nF, Cstripstrip from 90 to 120 pF (can be reduced) from 90 to 120 pF (can be reduced)

Scan with Fe55 source → → 90% of strips OK (1st proto!)90% of strips OK (1st proto!)

→ → ready to build them at Saclayready to build them at Saclay

ElectronicsThe limited space requires an off-detector electronics → long cablesThe limited space requires an off-detector electronics → long cables

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

→ → Irakli found 70 pF/m (Hitachi)Irakli found 70 pF/m (Hitachi)

→ → initial cables were 160 pF/m (FLEX)initial cables were 160 pF/m (FLEX)

→ → CCcabcab = 105 pF ~ C = 105 pF ~ Cstrip strip

→ → Significant effect on S/B (~50%)Significant effect on S/B (~50%)

→ → Needs 10 V more to be compensatedNeeds 10 V more to be compensated

Electronics - recent developments

0,7

0,8

0,9

1

1,1

1,2

1,3

1,4

1,5

1,6

1,7

1,8

1,9

0 20 40 60 80 100 120 140 160 180 200

Mag

nitu

de A

DC

inpu

t (V)

Input capacitance (pF)

Asic DREAM0: Magnitude versus input capacitance

AGET

modif

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

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

→ check ability to withstand sparks→ Goal: 40 pF/m cables

Micromegas CLAS 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

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

Spark rate studiesActivity started in 2009Activity started in 2009

→ → simulation: try to relate sparks with largesimulation: try to relate sparks with large energy deposits with Geant4 (Gemc)energy deposits with Geant4 (Gemc)

→ → spark condition: Nspark condition: Nelel ~ 10 ~ 1077 (Raether) (Raether)

→ → Quantitatively reproduces (few) existing dataQuantitatively reproduces (few) existing data

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

→ → Explains gas effect & give predictions (bulk)Explains gas effect & give predictions (bulk)

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

Spark rate studies

→ → 6 different detectors in 150 GeV pion beams6 different detectors in 150 GeV pion beams

→ → bulk ~ non-bulkbulk ~ non-bulk

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

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

Tests at CERN/SPS, October 2009Tests at CERN/SPS, October 2009

→ → Effect of a 1.5 T Effect of a 1.5 T magnetic field magnetic field

→ → 11stst test of a MM+GEM detector (D. Neyret) test of a MM+GEM detector (D. Neyret)

→ → No strong effect of B fieldNo strong effect of B field

→ → 1 week of data1 week of data

Spark rate studies

→ → 1 MM & 1 MM+GEM in FROST setup1 MM & 1 MM+GEM in FROST setup

→ → simulation ~ OKsimulation ~ OK

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

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

Tests at JLab/Hall B, July 2010Tests at JLab/Hall B, July 2010

→ → Effect of a 5 T // magnetic fieldEffect of a 5 T // magnetic field

→ → 100 with GEM foil100 with GEM foil→ → x10 with 5 T fieldx10 with 5 T field

→ → 2.5 days of data2.5 days of data

Spark rate studies

→ → 12 detectors in 12 detectors in ππ++ or or ππ-- beam beam

→ → peaks in spark rates with peaks in spark rates with ππ++

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

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

Tests at CERN/PS, August 2010Tests at CERN/PS, August 2010

→ → beam momentum tunable between 0.2 and 3 GeV/cbeam momentum tunable between 0.2 and 3 GeV/c

→ → confirms GEM effectsconfirms GEM effects

→ → 2 MM+GEM to understand spark rate suppression2 MM+GEM to understand spark rate suppression

→ → 2 weeks of data2 weeks of data

Spark rate – last mysteries

→ → effect of the longitudinal 5 T fieldeffect of the longitudinal 5 T field

→ → strong hint for significant effect of transverse diffusionstrong hint for significant effect of transverse diffusion

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

2 observations cannot be reproduced by the naive simulation2 observations cannot be reproduced by the naive simulation

→ → spark suppression with the MM-GEM detectorsspark suppression with the MM-GEM detectors

→ → explains all effects seen with MM-GEM:explains all effects seen with MM-GEM:

→ → large suppression with moderate GEM gainslarge suppression with moderate GEM gains

→ → effect of trans. diff. only at high GEM gainseffect of trans. diff. only at high GEM gains

→ → change of slope at high GEM gainchange of slope at high GEM gain

new spark condition: critical surface charge densitynew spark condition: critical surface charge density

Integration

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

Forward Tagger with Micromegas?Project to equip the FMT with central pixels for small angle e- detectionProject to equip the FMT with central pixels for small angle e- detection

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

- add 2-4 MM layers in front of calo- add 2-4 MM layers in front of calo

Track finding eff > 95% in pFMT

Track finding eff > 95% in pFMT

Very large background due to MoellerVery large background due to Moeller

zz

φφpp

All hitsAll hits Selected hitsSelected hits

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

Schedule

Conclusion

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

Additional slides

Working pointParameter Barrel (Z&Y) Forward Remarks

Drift space 2-3 mm 5 mm

Gas Ar+10%iC4H10 Ne+iC4H10

Fields ratio 5.5-6 50

Mesh Transparency 40% 40%

Electron Transparency

40-45% ~100% Measured @ B=0

Gain (effective) 5000 3000

Detection Efficiency >90% >95% Measured @ B=0(X)

Tracking Efficiency >93% >90% Simulation (tracking)

Detectors / layer 3 1-2

Background noise/ Detector

2 MHz 12 MHz Geant4 estimate

Sparking rate 1/s 0.4/s Geant4 estimate

Space resolution 220&100 µm 80 µm Garfield estimate

Lorentz angle 20° 0° Garfield estimate, validated