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Rare Event Searches with Xe /TMA TPCs

Rare Event Searches with Xe /TMA TPCs. Diego González- Díaz (Zaragoza University and Tsinghua University), Stony Brook, 04-Oct-2012 . 1. TPCs for rare event searches. CAST ( axion searches ). NEXT-100 (neutrino- less double beta decay ). XENON ( dark matter ).

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Rare Event Searches with Xe /TMA TPCs

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  1. Rare Event Searches with Xe/TMA TPCs Diego González-Díaz (Zaragoza University and Tsinghua University), Stony Brook, 04-Oct-2012 1

  2. TPCs for rare event searches CAST (axionsearches) NEXT-100 (neutrino-lessdouble beta decay) XENON (darkmatter) T-REX (directionaldarkmatter) ArgonDM (darkmatter) ………. EXO-200 (neutrino-lessdouble beta decay) 2

  3. Hector Mirallas MicrobulkMicromegas technology • Main characteristics: • Simple and robustall-in-onekapton-clad 2-copper sandwichstructure. • Verylowoutgassingand highradiopurity(<30 μBq/cm2for235U, 238U, 232Th chains). • Multiplicationtakes place in ‘cells’. Geometrical UV-photonquenchingseemstoprovideanimprovedstabilityat highpressures. • Granularitydemandsare easilyscalable. 50 μm 115 μm Veryhighquality of pattern! copper 5 μm S. Cebrian et al, Radiopurity of Micromegas readout planes, Astropart. Phys. 34 (2011) 354-359 y [μm] kapton 50 μm copper Comsol simulation for a typical field configuration at high electron transparency: Edrift/Eamp~0.01 x [μm] 3

  4. A sensible application for next-generation TPC experiments: ββ0-decay constrained by ν-oscillations presentββ0-bounds Inverted mass ordering cosmologicalconstraints Klapdor’s claim Normal mass ordering A relevant figure of merit. Sensitivity to mββ: upper mass limit that can be claimed at 90%CL by a negative result in the next generation ββ0 experiments, as a function of theirexposure. end of inverted mass ordering landscape J. J. Cadenas et al., Sense and sensitivity of double beta decay experiments, JCAP(2011) 4

  5. Canfranc UndergroundLab Why NEXT-100? • Itcovers a ‘technological gap’, providingsimultaneously: • Goodtopologicalinformation. • Goodenergyresolutiondownto 0.5-1%FWHM@Qββ. • Goodprospectsforscalabilityto1Ton. 2-blob ββ0 event at Qββ backgroundevent at Qββ V. Alvarez et al., NEXT-100 Technical design report (TDR). Executive summary, 2012JINST 7 T06001 5

  6. Why microbulk Micromegas? • Flexibility for large area coverage. • Possibly the only affordable technological concept that allows simultaneously for energy resolution and virtually unlimited tracking capabilities at high pressure and large areas (1-5m2). • Assets that will be surely useful for 1Ton experiments . • Extremely radio-pure. . work-line 1 (this talk) • Not mature enough, specially for operation at high pressures. • Not sensitive to the to signal . work-line 2 (work in progress) • A priori compatible with electroluminescence . • Can improve resolution down to Fano factor. • Recover sensitivity to to. Why Xe-TMA? work-line 1 (this talk) They are known to form a Penning mixture, that is a desirable for energy resolution and maximum gain of gaseous detectors. It increases drift velocity and reduces diffussion, recombination and attachment, enhancing the topological signatures. work-line 3 (Dave Nygren et al at Berkeley) Penning mixtures are known to reduce the Fano factor by 1/2-1/3. If TMA fluoresces in the visible region one might expect to keep sensitivity to to and still being able to create electroluminescence (!). J. Phys. Conf Ser. 309(2011)012006 6

  7. General purpose chamber for R&D studies • Main characteristics: • Fully stainless-steel vessel, h=10cm, ϕ=16cm. • Designed for standing pressures in the range 0-15bar. • Mini-TPC with microbulkMicromegas as anode. • Bake out system + turbo pump, allowing for vacuum down to 10-6mbar after full TPC assembly. • Outgassing below 5x10-5 mbar l/s before gas filling. • Gas recirculation through SAES FaciliTorr + Messer Oxysorb getters. • Characterization of system composition with a Pfeiffer OmniStarmass spectrometer. • O2 and H2O impurities estimated (indirectly) to be below 30ppms in running conditions. O2and H2O –meters will be incorporated soon. • Acquisition with: • 1) Canberra 2004/2022 amplifying chain + multichannel analyzer Amptek MCA 8000A. • 2) Oscilloscope. radioactive source goes here Field cage: h= 1-6cm 10 cm 3.5cm Micromegas (50μm gap, 50μm holes, 115 μm pitch) 7 10MΩ/resistors

  8. Diana C. Herrera Operation of Micromegas in Xe+TMA mixtures.General properties. Xe/TMA at ~98.5/1.5 Good transparency even at 10bar. Only achievable through continuous gas purification. Used for this study. 5 Good description and good 1/√E scaling. Find these results at: Xe/TMA at ~98.5/1.5 P = 8bar S. Cebrian et al., Micromegas operation at high pressures in Xenon-Trimethylamine, arXiv 8

  9. Diana C. Herrera Penning at work-I too much too much too little too little too much too much too little too little 9

  10. Diana C. Herrera Penning at work-II Drastic increase in gain at constant field with increasing concentration of TMA! -> Presumably due to the activation of Penning-type energy-transfer mechanisms up to x30-50 increase at constant field Field for a gain=300 1.5-2.5% (optimal range is extremely narrow!) • Necessary increase of the field is much weaker than E/p mainly due to: • Scaling of α = αo p/po • To a smaller extent to the dynamics of the Penning effect. < x3 10

  11. Diana C. Herrera Pressure scan for Penning-optimizedXe/TMA mixtures (~97.5/2.5) Strong exponential drop of the maximum achievable gain at high pressures. -> Possibly due to the increased space charge at constant gain for high pressure. Is it possible to further improve?. Where is the limit?. Xe/TMA at ~98.5/1.5 x400 Xe/TMA at ~98.5/1.5 Energy resolution degrading at high pressure: -> Operation at a much reduced E/p (down to 1/3-1/4) cools the electron swarm at high pressures. 22.1 keV 11

  12. Diana C. Herrera Best energy resolutions for Penning-optimizedXe/TMA mixtures (~97.5/2.5) pure Xe, C. Balan et al., 2011 JINST 6, P02P006 pure Xe, T. Dafni et al., J. Phys.: Conf. Ser. 309 (2011) 012009 (similar setup) Xe/TMA, these measurements within a factor x3 of the Fano factor limit for pure Xenon (0.27%FWHM) 12

  13. Francisco Iguaz Preliminary modeling and scopefor large area TPCs Si-diodefortriggering (to) α 241Am driftregion can be imaged γ MM vd [cm/μs] x 4-5 pure Xenon E [V/cm/bar] DT [μm/cm1/2 bar1/2] Region of maximumtransparency in Xe/TMA mixtures x 10! Preliminary comparison with TMA rather reasonable (despite TMA itisrated 3* in Magboltz at themoment) pure Xenon pushing the Magboltz-truth a step further… E [V/cm/bar] 13

  14. Preliminary results with a medium size TPC 14

  15. time-line arrival pumping and bake-out system 30cm 35cm 0.8cmx0.8cm pixelizedmicrobulk Micro-Megas T2K electronics (based on AFTER chip) field-cage 15

  16. Laura Segui Firstresultsfor 1/4th of thereadoutplane (proof of principle) Unfortunatelyconnectivitynotyetperfect: ~10/270pixels are notproperlyconnected. Wehaverecoveredfrom a designproblembymeans of a tediouscapacitiveprocedurethatensures a high (yetnotperfect) connectivity. Work in progress. 241Am 57Co Xe/TMA 96.3/3.7 Edrift= 170 V/cm, Eamp= 54 kV/cm, P = 1 bar 16

  17. Laura Segui Energyresolution • Nextsteps: • Channelequalization • Optimization of pedestal subtraction. • Eventfiltering(forinstance, suddennoiseexplosions). • Improvedfiducialization. • Specially, development of anadequateanalysisforthis new stage. 17

  18. Laura Segui someevents at around60keV 18

  19. Laura Segui someevents at around90keV x-ray candidate 19

  20. Laura Segui someevents at around120keV x-ray candidate x-ray candidate 20

  21. Conclusions • Microbulkmicromegas in Xe-TMA mixtures is an appealing technological option for rare event searches. • The Penning transfer mechanisms seem to be optimally active within a mild 1-3% TMA concentration range, therein virtually un-affecting the experiment exposure (Xenon). • Operation at a gain x400 and at 0.9%FWHM@Qββ,Xe at 10bar is possible. • We would like to study the mixture more systematically with a new batch, specially the maximum gain, reproducibilityand stability. • Preliminary comparisons with Magboltz (TMA rated 3*) suggest that a dramatic factor x10 reduction of the transverse diffusion is within reach. Further studies resorting to event topology are required to validate this estimate. • In order to make this option competitive, we are considering various approaches to determine the to (an obvious one being TMA-fluorescence) • Proof of principle demonstrated for a medium size ϕ=30cm, h=35cm TPC. Tracks can be clearly reconstructed, albeit a crude value for the energy resolution is about a factor x3 worse than for the case of un-segmented readout in small chambers. • However, a large effort is still needed in order to achieve competitive results for the complete medium-size TPC at 10bar. stay tuned! 21

  22. The team • Igor Irastorza • Hector Gomez • Asuncion Rodriguez • Juan Castel • Hector Mirallas • Alicia Diago • Laura Segui • TheopistiDafni • Diego Gonzalez-Diaz • Diana Carolina Herrera • Susana Cebrian • Gloria Luzon • Alfredo Tomas • Esther Ferrer-Ribas (CEA-Saclay) • IannisGiomataris (CEA-Saclay) and Rui Oliveira (CERN) Antonio Teixeira (CERN) and the support of the CERN workshop 22

  23. BACKUP

  24. Status of NEXT-I(MM) on the last collaboration meeting (Nov11) In a nut-shell • Bake-out and pumping systems fully installed: • Gas tightness: <1mbar/day (T-corrected) at 11bar during 10days • Vacuum: ~10-6 mbar after bake-out • Out-gassing: <10-5 mbar l/s • The HV for the 35cm-long drift region proved to be Paschen-tight up to 7kV@1bar and 26kV@8bar in pure Ar. Common wisdom suggests that for Xe it should be usually better. • Mass-spectrometer working steadily. Calibration factors in Xe-TMA mixtures obtained. • Re-circulation system installed. Not commissioned. • Four pixelized μ-bulk MicroMegas (Φ=28cm) installed. • T2K electronics connected. Not thoroughly tested. Analysis software still in early stage.

  25. Status of NEXT-I(MM) today Final system pressure Levels down to Pf=6x10-6 mbar achieved in the present system after ~72h heating time at 130deg.  However, x10-100 worse vacuum levels were used during most of measurements presented here. 

  26. Status of NEXT-I(MM) today Out-gassing Levels below Og=3x10-4 mbar l/s achieved in the present system. From experience it will be much better after bake-out. Unfortunately it was not measured. 

  27. Status of NEXT-I(MM) today Gas tightness Jan-2010 After correcting for temperature variations: Previously: ΔP<1mbar/day at 11bar for 10 days (limited by pressure-meter). Presently: ΔP<3mbar/day at 1bar for 3 days (limited by pressure-meter). No concern regarding gas leakage but more systematic measurements will come.

  28. ~x2 Status of NEXT-I(MM) today Electrical insulation 2%TMA 0%TMA really?? From D. C. Herrera Xe-TMA mixtures much less Paschen-tight than pure Ar (Penning effect at work!), by~ x2. The drift fields are still comfortable and transparency seems to be achievable.  Strong limitation for systematic study of attachment. An extra factor x3 will be handy  If it is Paschen-tight for Xe-TMA, possibly ok for most practical mixtures. 

  29. very seldom, even cosmic-ray triggered events can be directly seen from the mesh external trigger signal mesh signal 180 μs Chamber operation (I) Status of NEXT-I(MM) today electronics situation After grounding optimization and soft RC-filtering, signal is visible at Edrift= 160 V/cm/bar, and EMM = 58kV/cm (Xe-TMA ~ 98/2) with the following parameters: • Mesh signal with single amplifying stage (CANBERRA-2004, tfall~50μs for δ-impulse excitation): • Eth~30keV, rmsEnoise~10keV (fairly stable) • Mesh signal with double amplifying stage (CANBERRA-2004 + spectroscopic amplifier, gaussian response tshaping=8μs): • Eth~10keV, rmsEnoise~3keV (fairly stable) • Pixel signals with T2K electronics (tshaping=2μs): • Eth~1.5keV, rmsEnoise~0.75keV (unstable) Micro-bulk MicroMegas produces nice signals in the scope.  System problems galore: -> cross-talk -> noise -> HV in 2 MMs unproperly applied -> dead pixels -> un-perfect cable-connector contact

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