WG2 session summary

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WG2 session summary

M. ChefdevilleRD51 collaboration meeting

7-10 October 2010, Bari, Italy

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Session agenda

• Emphasis on operation in argon at low temperature (3 talks)– GEM/Micromegas/GridPix

• MAMMA collaboration presentations (2 talks)– Status report and spark study

• Application with neutrons– GEM for neutron beam diagnostic

• High rate application– Micromegas for COMPASS– Proposal of an experiment at a pp collider

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The double phase argon LEM-TPC, D. Lussi

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• Large Electron Multiplier– 1000/500/800 um thickness/diameter/pitch

• Two dimensional projective anode– 10x10 cm2 with 3 mm readout pitch– Spark protection and preamplifier

• Gas purification system– Cool down phase – filling – recirculation– 1 volume / 48 h– best purity achieved [O2]eq < 0.6 ppb


Made @ CERN workshop

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• Test setup @ CERN


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• Cosmic tracks– X/Y correlation -> Q sharing close to 1– Extraction field scan: attachment and time smearing < 1

kV/cm– Landau MPV @ ≠ voltages -> max gas gain ~ 30– dQ/dx VS time -> e- life-time & [O2]eq


• Alternative charge readout: Micromegas (A. Delbart)

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• Robustness test of Bulk Micromegas @ low T– Max. voltage of at decreasing temperature

(1300 V@-196° C)– After drying out detector at 80° C for 1 night

gas gain curve was lower than before bath• High pressure gas gain measurement @ Room T

– Former Hellaz exp. Chamber– No particular gas purification system– 241 Am alpha source + ORTEC readout of mesh– Gain max of 500 @ 3.5 bar with 50 um micro-Bulk

First test of Micromegas in double phase liquid Ar, A. Delbart

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• Goal: operation & gas gain measurement with a Bulk-Micromegas• 1D readout with 32 strips (3.1 mm pitch) -> modified PCB (CERN workshop)• 2 bulk done with 128 and 100 um gap


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• Measure gain @ various voltages (10 fC/strip expected for MIP) • Fields of 42, 46, 47 kV/cm, gain of 1,3, 4• Steep transition from stable to unstable conditions• Signal loss while increasing drift field

(250-750 V/cm) not observed


42 kV/cm 46 kV/cm 47 kV/cm

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• The maximum gain is low and may be due to the very high purity of Argon (which is demanded for charge drift in liquid)

• Such a low gain could be suitable for neutrino applications but higher gains (>100) are needed for dark matter search

• But these are the first tests and further improvements and studies are planned (thinner bulk gaps, micro-bulk, …)


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• DARWIN: European R&D project for bi-phase missing mass/energy detectors• With InGrid TPC:

– detection of single, individual electronsessential: granularity and the very small source capacitance at pixel input

– high (95 %) single electron efficiency– accurate X, Y and Z (timing) precision– potentially: (UV) photon detector

First operation of GridPix low temperature, H. van der Graaf

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• TimePix proved to work at -100 °C, confirmed at -73 °C, -160 still to be tested

• Maximum gas gain of 200– Might not be a problem with a new TimePix with preamplifier optimized for low

temperature application (noise of 20 e- ?)

• New collaboration with Rubbia group at CERN– Construct support structure to place GridPix inside

the Cryostat (-186 °C)– First test to check the suitability of detector’s

electronical components

• Detect scintillation light signal with GridPix– CsI layer on grid


55Fe in pure argon,HVgrid = 350 VP = 1 barT = -70 Cat NLR cryostatgain: ~ 200 !

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• MAMMA: Muon Atlas MicroMegas Activity– High rate application -> avoid sparks or make detector spark-proof– High resistive coating may solve the sparking issue

• Test in high intensity beam of detector with different resistive coatings (2009)– Preliminary results

• Preparation of next test beam & resistive Bulk characterization– Gain stability and spark topology studies

Characterization of resistive Micromegas for MAMMA, D. Attie

Requirements:High rate capability (≤ 10 kHz.cm-2)Spatial resolution ~100 µm (θ ≤ 45 °)Radiation hardness and good ageing propertiesTime resolution ~few nsLevel1 triggering capabilityLarge surface

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• Strong attenuation of spark current and voltage drop• Spatial resolution of 80 um (1 mm pitch strip)• Low cluster size value


2009 TB preliminary results

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• Setup for the next TB– Increase cluster size with higher diffusion gas (Ar/CF4/iso

95/3/2 -> Ar/iso 98/2)– More detector with smaller strip pitch (0.5 mm)

• First characterisation with 55Fe source– Gas gain measurements & energy resolution– Charging up effects & model comparison


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• Sparking study in resistive detectors with an alpha source– Measure voltage drop through a 1 MOhms resistance on 4 adjacent strips and apply

threshold


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• In some configuration the resistive coating is able to contain or even suppress the spark signal

• Ready for the next beam test at Cern to determine in high rate condition operation the efficiency of the various resistive Micromegas.


R14, Resistive strips 300 kΩ/

R17, Joerg likeStandard Bulk

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• New results with “Joerg” chambers: R11,R12,R13– Small 100 x 100 mm2 chamber with 100 mm long strips and

250 µm strip pitch, 360 strips in total• Characteristics:

– Resistive strips connected to the ground– Thin insulating layer between of the resistive and readout strips– AC coupling of signals– Sparks are neutralized through the resistive strips to the ground

Micromegas progress report, V. Polychronakos

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• Laboratory tests with X-tube and 55Fe quanta


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• Test in a neutron beam– First plots showed at previous collaboration meeting– New results on spark rate

• R11 worked fine in a neutron flux of up to 1.5 x 106 n/cm2 s • Despite sparks, no HV breakdown, no dead time • Measured three Ar:CO2 gas mixtures, 93:7 looks very interesting,

with a spark rate almost a factor 5 lower than for 80:20


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• Test in a high intensity hadron beam• R11, R12, R13, and P3 chambers were tested in +120 GeV pion beam

intensities 40 kHz & 5 kHz in two Ar:CO2 mixtures, 85:15 and 93:7• Main goals:

– Study HV and current behavior of resistive and non-resistive chambers in a hadron beam– Measure performance (spatial resolution and efficiency) of resistive chambers– Study performance of long strips (0.4 m & 1m, non-resistive)

• A few million of events are being analyzed


Event display:Timing at angle 40°


MM readout chip designBNL chip features

• Data Driven System with Peak Amplitude and Time Detection: on-detector zero suppression

• Neighbour-channel enabling circuitry: high thresholds without losing small amplitudes

• Able to provide Trigger Primitives for on-detector track finding logic

• Based on existing chip developed a few years ago for a TPC application

• Appropriate for a variety of detectors (mMegas, TGC, TPC, GEM, etc.) requiring amplitude and time measurement

Example of test of BNL chip with Micromegas• On-chip zero suppression:

only channels that exceed a predefined trigger threshold, plus the two neighbouring ones are analyzed and read out

Simulation


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• Next steps– Proceed with full-size prototype (CSC size)

• First version is under design• Readout with APV25 chip and RD51 readout system• Test in H6 foreseen in October

– Multi-plane full-size prototype design will start this fall• BNL electronics should be available• Could install a test chamber in ATLAS during 2012 shut down


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nGEM Detectors for the SPIDERneutron facility, G. Croci

Fast neutron beam diagnostic• Interaction of deuterium ions of 100 keV

with the beam dump:– D + D -> 3He + n(2.45 MeV)

• detect any variation of the deuterium beam intensity with1 ns & 20 mm reso.

• SPIDER beam divided into 16 groups of 5*16 beamlets of20x22 cm2

Beam dump• 2 layers of CuCrZn alloy interleaved

with water• Place detector behind to measure

neutrons flux

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nGEM detectors• Triple GEM detector

– dimensions : 35.2 cm x 20 cm – 3 mm/ 1 mm / 2 mm/ 1 mm gaps

• Pads readout with 16*10 = 160 pads of 20 x 22 mm2

• Al or Cu Cathode equipped with a polyethene (CH2) layer used to convert neutrons into protons

• Gas mixture Ar/CO2 70%/30% • FE Electronics: CARIOCA

(open to other counting chip solution)


The Al layer thickness is optimized in order to stop all the protons that are not normally emitted

60 keV deposited in the gas

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Previous measurements in beam• At Frascati Neutron Generator• Detector divided into 2 halves

– One sensitive to 2.5 MeV neutrons (DD reaction)

– One sensitive to 14 MeV neutrons(DT reaction)

• Readout Anode : 128 readout pads 6x12 cm2 organized in a matrix 16x8

On-going and future tests• Gamma test @ Frascati now• Neutron TB in November• 16 nGEM detectors should be produced in

order to equip all the beam dump, total area of about 1.5 m2 2012

• The final detector will be HV powered using the new HV GEM module

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Proposal for a high rate experiment with MPGD readout, D. Kaplan

• Fixed target experiment to study CP-violation of hyperons particles• Use Fermilab anti-proton beam and existing apparatus after

Tevatron shut down (2011?)

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Status report of the Micromegas R&D for COMPASS at Saclay, M. Vandenbroucke

Pixelized center for COMPASS• 40x40 cm2 Bulk Micromegas• 2560 channels read out by APV chips• In COMPASS since end August 2010

with comparable performance with “old” Micromegas

APV tunning• Parameters

– Preamplifier feedback current– Shaper powering current– Shaper feedback current

• Optimization between noise, amplitude and time occupancy of the APV signals

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Status report of the Micromegas R&D for COMPASS at Saclay, M. Vandenbroucke

Gain measurements• Mesh and strip readout• Measure that resistive detectors have lower gain

– Not yet understood• Further studies will continue with the October

RD51 test beam on SPS

PS/T11 test beam, Aug. 2010• COMPASS/CLAS12

– 6x10 cm2 Bulk detectors– 144 strips with 400 um pitch– Read out by AFTER (T2K)

• Investigation of different protection schemes• GEM pre-amplification• Resistive layers

• Low energy beam• Study influence of hadron energy

• Analysis on-going

Last slide

• Thanks to the speakers for their contributions

• Thanks you all for your attention

Documents

WG2 session summary