Piggyback seal MicromegasD. Atti, A. Chaus, D. Durand, D. Deforges, E. Ferrer Ribas, J. Galn, I.Giomataris, A. Gongadze, F.J. Iguaz, F. Jeanneau, R. De Oliveira, T. Papaevangelou, A. Peyaud, A. Teixeira

CERN and IRFU (CEA-Saclay)

ConceptSeparation of the amplification structure and the readout planeResistive layer (RuO2)~10 mResistive thin layer (1 M / to 100 G /) Signal is transmitted by capacitive coupling to the readout planeOptimisation of the induced signal : tinsulator

I. Giomataris First set-up 3 detectors with active area: 33 cm21 cm drift, 128 m amplification gap, 20 m of RuO2 with 100 M/, ceramic layer 300 m

Argon + 5%Iso and Ne + 5% Ethane and a standard buk in Argon + 5%Iso

-HVdrift-HVresistGround-HVamp

I. Giomataris

First experimental resultsChecking possibles looses by the ceramic layer: signal entirely transmitted Test with a 252Cf (fission fragments signals) reading simultaneously mesh and anodeAmplitude within 5%

Same rise time for both polarities

I. Giomataris

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I. Giomataris Rate capabilityWith X-rays from a gun (8keV)

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I. Giomataris Comparison with Monte Carlo

I. Giomataris

I. Giomataris 1 G/sq10 G/sq100 M/sq10 M/sq

I. Giomataris

CMOS chip readoutMedipix2/TimepixCMOS chip256256 square pixels of 55 m side each

To be used with MPGD the MPGD needs to be covered by a layerof high resistivity material (amorphous silicon or silicon-rich nitride)Set-up with Piggyback3020 mm2 bulkAmplification gap 128 mDrift gap 10 mmSignal observed on Medipix chip with Ar + 5% IsoNo damage of the chip during operation at high gain 105

I. Giomataris

*David.Attie@cea.frSpot diameter about 500 mmWith a ceramic plate of 100 mmWe expect to get it down to 150 mm

55Fe events (G ~ 50 000)

I. Giomataris

Second set-up: towards a sealed detector Ar+5% Iso

I. Giomataris

Detector chamber gluedOne night oven at 60C + pumping

Flushed with gas for only 4 hoursStability over 14 daysSecond set-up: towards a sealed detector

I. Giomataris

Latest result for a sealed detector Stability over 30 daysSmall fluctuations due to day night effectsBig amplitude fluctuation due to the removal of the sourcePiggyback resistive Micromegas , D. Atti et al e-Print: arXiv:1310.1242 [physics.ins-det]

I. Giomataris

Conclusions and outlookFloating mesh, Bulk Micromegas, Microbulk, Ingrid and now PiggybackPiggyback resistive Micromegas provides spark protectionDetector dissociated from readout planeCan optimise dead spaceHigh rate vs resistivity has been studiedTest higher values of resistivity, different thickness of ceramicSeal detector is under development