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Diana C. Herrera on behalf of Zaragoza group .

Micromegas -TPC Operation at high pressure in Xe+Trimethylamine mixtures. Diana C. Herrera on behalf of Zaragoza group . University of Zaragoza SIXTH SYMPOSIUM ON LARGE TPCs FOR LOW ENERGY RARE EVENT DETECTION Paris 18 December 2012. Outline. Introduction Experimental setup

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Diana C. Herrera on behalf of Zaragoza group .

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  1. Micromegas-TPC Operation at high pressure in Xe+Trimethylamine mixtures Diana C. Herrera onbehalf of Zaragoza group. University of Zaragoza SIXTH SYMPOSIUM ON LARGE TPCs FOR LOW ENERGY RARE EVENT DETECTION Paris 18 December 2012

  2. Outline Introduction Experimental setup Experimental procedure Results Si-MM setup: drift velocity & attachment NEXT-Micromegas prototype Conclusions and outlook Small TPC S. Cebrián et al, arXiv:1210.3287 JINST accepted: January Medium TPC Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 2/15

  3. Introduction Neutrinoless double beta decay in 136Xe using HPTC Main challenges • Improve as much as possible the energy resolution • at Qβ β-value of 136Xe (2458 keV) ~1% • Better Pattern recognition →discriminate from all different background signals 136Xe Explore: Xe – basedPenning Mixture Penning Mixture: It is formed with an additive gas with ionization potential below and closer to the first metastable level of the main gas (Xe). Previous experimental studies with various Xe- based Penning mixtures have shown that Trimetilamine presents a strong Penning effect. Brian Ramsey and P. C. Agrawal: NIM A 278 (1989) Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 3/16

  4. Introduction Xe+TMA Penning Mixture Energy Resolution Xe+TMA Pattern Recognition Intrinsic energy resolution • Drift velocity could increase • Diffusion coefficient could reduce • F and G may be reduced We show in this work : Good prospects to search Remarkable improvements in energy resolution and gas gain in Xe+TMA mixtures Preliminary measurements of drift velocities in Xe+TMA mixtures. D. Nygren, et al, Conf. Ser 309 (2011) Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 4/16 signal

  5. Experimental setup Characterization of Xe+TMA Penning Mixtures Systematic studies of energy resolution and gas gain in a MigromegasHP TPC. Vessel of stainless steel, V=2 L h=10 cm, ϕ=16cm Driftdistance 1 cm Microbulk detector ϕ=3,5 cm TPC 1cm 3.5cm 10 cm Experimental Procedure Varying the Fraction of TMA at four reference pressures: 1, 5 , 8 and 10 bar. Determine the optimum fraction Varying the pressure between 1 and 10 bar Maximum gain and Energy resolution Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 5/16

  6. Experimental Procedure Before Filling the TPC • Pumped →vacuum down ~10-6 mbar • Baked out → outgassing down ~10-5 mbar Xe+TMA mixtures preparation • At the beginning high concentrated mixture • ( 7 %) of TMA was prepared. • Lower fractions of TMA were obtained adding fresh Xe from the external bottle Optimal conditions • Circulation through a SAES filter • Pressure was kept constant • active behaviour of filter →absorbing or expelling TMA We wait around 20 minutes →Stable TMA concentration Micromegas Characterization 1. Determination of operating point 2. Gain and energy res. Measurements At the end Mass Spectrum Xe+3.5%TMA • the gas composition was measured with a Pfeiffer OmniStar mass spectrometer. • the TPC and the gas system was pumped out by cooling the sample cylinder to the LN2 temperature Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 6/16 TMA Peaks Xe Peaks H2O O2

  7. Experimental details Acquisition Offline analysis Using a 3-step Rootroutine The Ag Kα, Kβlines and the corresponding Xe escape peaks (L-shell) Peak at 22.1 keV 109Cd collimated radioactive source used for all measurements 14-30 keV • peak at 22.1 keV • Gas gain • Energyresolution • Energy Resolution →(%FWHM) • Gas gain → • electronic chain calibration • W value of Xe Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 7/16

  8. Experimental details Energy spectrum from 109Cd source acquired at 8 bar in a Xe+1.4% TMA mixture with E/p=245 V/cm/bar. peak 88keV 5.1% Ag X-rays @ 22.1 keV 9.8 % Xe escape peak @58keV (%FWHM) 5.8% Scaling 1/ Fit The scaling expected Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 8/16

  9. Experimental details Operating point The amplification field was kept constant (gas gain around 100) →Ensuring maximum electron mesh transmission Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 9/16

  10. Results → Varying the TMA fraction Max. ~% 2 Max. ~% 2 Max. ~% 2 Max. ~% 2 Max. ~% 2 TMA Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 10/16

  11. Results → Varying the TMA fraction Max. ~% 2 Max. ~% 2 Max. ~% 2 Max. ~% 2 Max. ~% 2 TMA Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 10/16

  12. Results → Varying the TMA fraction • For a given amplification field the addition of TMA produces a rapid increase in gas gain. In general, the gas gain improves one order of magnitude for a given amplification field Common region 1-10 bar Strong Penning effect 1.5 -2.5 % TMA • The energy resolution also improves. At 1 bar, the energy resolution goes from 7.3 % to 8.4 % (%FWHM) 0.4% TMA At 10 bar, the energy resolution improves by a factor 2. 19.7 (%FWHM) 0.8% TMA 1.0 -2.5 % TMA Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 11/16

  13. Varying the pressure 1-10 bar With concentrations below % 2 variation 1-10 bar Maximum gas gain decreases exponentially with pressure. Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 11/16

  14. Varying the pressure 1-10 bar With concentrations below % 2 variation 1-10 bar Maximum gain improves with respect to pure Xe C. Balanet al, 2011 JINST 6 P02006 Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 11/16

  15. Varying the pressure 1-10 bar With concentrations below % 2 C. Balanet al, 2011 JINST 6 P02006 Similar trend has been observed in previous works, where the level of impurities estimated are less 1 ppm H. Sakurai et al, NIM A 307 • Degradation: • to intrinsic phenomena • X the attachment. Diana Herrera (UNIZAR), TPC Conference, Paris, 18/12/2012 11/16

  16. Varying the pressure 1-10 bar With concentrations below % 2 C. Balanet al, 2011 JINST 6 P02006 Pure Xe Pure Xe Xe+@2%TMA Diana Herrera (UNIZAR), TPC Conference, Paris, 18/12/2012 11/16

  17. Varying the pressure 1-10 bar With concentrations below % 2 C. Balanet al, 2011 JINST 6 P02006 Pure Xe Pure Xe Energy resolution at 10 bar 9.6 (% FWHM) Xe+@2%TMA Diana Herrera (UNIZAR), TPC Conference, Paris, 18/12/2012 11/16

  18. By Francisco Iguaz Si-MM setup: drift velocity & attachment Coincidences with an 241Am source: Emits: α and γ particle simultaneously (30%) • αat the Si (t0) & γ at the Micromegas • We acquire the coincidences using an oscilloscope Δt 4 cm Diana Herrera (UNIZAR), TPC Conference, Paris, 18/12/2012 12/16

  19. By Francisco Iguaz Si-MM setup: drift velocity & attachment • New information on: • Drift velocity in Xe+TMAmixtures • Mean electron lifetime (gas purity, Xe+TMAattachment coefficients) Comparison with Magboltz 29.8 keV Xe escape 59.5 keV γ-Ray P=3 bar 88 kV/cm 100 V/cm/bar Diana Herrera (UNIZAR), TPC Conference, Paris, 18/12/2012 13/16

  20. NEXT-Micromegas Prototype Preliminary results with a medium size TPC using Xe+TMAmixtures Volume 80 L 30cm 0.8cmx0.8cm pixelizedmicrobulk Micromegas Talk by C. Oliveira Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 14/16

  21. NEXT-Micromegas Prototype • Signal for energy and tracking from the same detector • Energy: Amplification chain for the mesh pulse, MCA digitizer • Pixel signal readout using T2K DAQbased on the AFTER chip 241Am (α-shielded, to detect the 60 keVγ) First tracks observed 60 keVγ-Ray Co57 35cm 8 cm MMs Registered pulses foreach active pixel XY distrib.fortheactivatedpixels Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 15/16

  22. NEXT-Micromegas Prototype • Signal for energy and tracking from the same detector • Energy: Amplification chain for the mesh pulse, MCA digitizer • Pixel signal readout using T2K DAQbased on the AFTER chip 241Am (α-shielded, to detect the 60 keVγ) First tracks observed >140 keV Co57 35cm 8 cm MMs XY distrib.fortheactivatedpixels Registered pulses foreach active pixel Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 15/16

  23. Conclusions • We have operated microbulkMicromegas detector in high pressure TPC with Xe+TMA Penning mixture, obtaining very good performance in terms of stability, gas gain and energy resolution. • We have found an optimum range for TMA concentrations between 1.5% and 2.5% where the Penning effect is maximum. • We have observed the first tracks in Xe+TMA mixtures with the medium prototype. With respect to pure Xenon • Improvements in gas gain by a factor 5 considering a fix amplification field. • At 10 bar the energy resolution improves by a factor 3, being the best value down 9.6 (%FWHM) →extrapolates at Qβ β-value of 136Xe to 0.9 (%FWHM). Outlook: Xe+TMAmixtures • Systematically measurements of drift velocities will be done in both prototypes. • Measurements with Micromegas of 25 gap in the small prototype. • Simulations in Garfield in order to understand the microphysics of the avalanche. • Specific geometry and fields will be taken into account • the Penning transfer r will be calculated for Xe+TMAmixtures Diana Herrera (UNIZAR), TPC SYMPOSIUM, Paris, 18/12/2012 16/16

  24. Thank you

  25. The first Townsend Coefficient, Semi-empirical parametrization A and B are gas parameters that depend on gas Parameters obtained from linear fits of each curve . From 5 bar the coefficients are compatible Monte Carlo simulation of the avalanche microphysics will be realized in order to understand the deviations below 5 bar.

  26. The first Townsend Coefficient, Semi-empirical parametrization A and B are gas parameters that depend on the gas Parameters obtained from linear fits of each curve . Linear fitfor data above 5 bar Probably the Penning effect produces this deviations for pressures below 5 bar. P.K. Lighfoot et al., NIM 554 From 5 bar the coefficients are compatible

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