R&D WITH MICROMEGAS FOR LOW BACKGROUND APPLICATIONS: THE T-REX PROJECT Laura Seguí and Juan Antonio García Universidad de Zaragoza CEA, Saclay December of 2011

- U. Zaragoza: J. Castel, S. Cebrian, T. Dafni, J. A. García, H. Gómez, J. G. Garza, D. C. Herrera, I. G. Irastorza, G. Luzón, A. Rodríguez, L. Seguí, A. Tomás, J. A. Villar - CEA/Saclay: E. Ferrer-Ribas, I. Giomataris, F.J. Iguaz, J. P. Mols, T. Papaevangelou,, J. Galán - CERN: R. de Oliveira, A. Teixeira - CAST collaboration - NEXT collaboration

OUTLINE T-REX project  MMs for rare event searches · Radiopurity Measurements 1.MMs for axion searches:  CAST experiment: · Canfranc test · Simulations · 2012 prospects · IAXO project 2.MMs for ββ Decay:  NEXT Experiment · Pattern Recognition · Energy Resolution Results · Tracking with MicroMegas R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 1

T-REX PROJECT Novel MPGD developments Low background techniques Application of TPCs to Rare Event searches? New generation of experiments with access to high topological information Application of TPCs to Rare Event searches? New generation of experiments with access to high topological information - Gas TPCs offer high potential for rare event through signal topology. · Example: directionality of WIMPs! - But, complex detector to reach high masses - Novel readout techniques based on MPGD - T-REX to merge MPGDs (=Micromegas) + low background expertise. - Focus on exploratory R&D and small scale prototyping R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 2

T-REX PROJECT NEXT-1-MM NEXT-0-MM Test bench CAST setup Clean handling From 2009 to 2011 First generation lab: operative + Further 90 m 2 being furnished… + R&D space Canfranc Infrastructure: - New laboratory at Zaragoza. R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 3

RADIOPURITY MEASUREMENTS 232 Th 235 U 238 U 40 K 60 Co Microbulk mM <9.3< ± ±24.8<3.1 * Kapton-Cu foil <4.6 * <3.1 * <10.8<7.7 * <1.6 * Cu-Kapton-Cu foil<4.6 * <3.1 * <10.8<7.7 * <1.6 * * Level obtained from the Minimum Detectable Activity of the detector Results (in  Bq/cm 2 ) Very low levels of radioactivity, compatible with the sensitivity of the measurement Contamination probably comes from the treatment of the materials used Next steps: identification of the contaminating steps and find alternatives  Rare events Searches dictate the use of radiopure materials  Microbulks are mainly Cu and Kp  potentially very radiopure  Several samples measured with HPGe at Canfranc 2 samples of raw material (double clad kapton foil) 2 samples detached from old CAST detectors R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 4

CAST EXPERIMENT Axions are particles proposed to solve the strong CP problem in QCD and are dark matter candidates. Axions could be produced in the sun via Primakoff effect. Solar axions could be detected via inverse Primakoff effect in a strong magnetic field. One of the most important factors in the sensitive of CAST is the background level of the detectors between 1-10 keV. X-ray detectors require low background techniques  working focused on reduction of the background level of the detectors. R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 5

CAST EXPERIMENT LHC prototype dipole magnet. Magnetic field: B=9 T Length: L=9.26 m Rotating platform and rails ( Vertical: ±8 o, Horizontal: ±40 o ) 2x90 min solar tracking/day CERN Axion Solar Telescope: CAST phase I (vacuum) Completed ( ) ma<0.02 eV CAST phase II (buffer gas) 4 He completed ( ) 0.02<ma<0.39 eV 3 He completed ( ) 0.39<ma<1.18 eV R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 6

CAST EXPERIMENT CAST microbulk MICROMEGAS exploit 3 different low background strategies: Low intrinsic radioactivity Light mass. Clean materials (copper, plexiglass, kapton,..) Signal topology  offline analysis 2D readout pattern via strips. Time information from mesh pulse. Shielding 2.5 cm of archeological lead 5 mm of inner Cu Clean inner atmospere by N2 flushing Typical rate (2011): <2 c/h x20 improving background from the beginning of the experiment. R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 7

CANFRANC TEST Canfranc Underground Laboratory (LSC) measurements: LSC situated at Canfranc (Huesca) in the spanish Pyrenees under the mountain Tobazo, with a depth of 2500 m.w.e.  muon flux reduced by a factor All enviromental variables are very stable at Canfranc and continuously measured (temperature, radon level, …) R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 8

CANFRANC TEST Experimental set-up: 10 – 20 cm of lead shielding, inner copper and nitrogen flux. Microbulk MICROMEGAS, faraday cage and automatic calibrator. Stainless steel cathode replaced by Cu cathode. Ultra-low trigger rate reached < 0.01 Hz Slow-control implemented measuring the temperature, pressure of the chamber and sparks. Canfranc rate: <0.1 c/h 2·10 -7 c·keV -1 ·cm -2 ·s -1 !!!! x20 improving background level of CAST. R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 9

SIMULATIONS R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop Fe calibration in Ar + 2% iso Geant4  55 Fe γ and environmental γ Magboltz  Diffusion in the chamber TRest (Zaragoza)  Electronic response Simulated external γ at CAST. Work in progress  simulate internal radioactivity of the detector. See Alfredo IRFU talk September of 2011 at Saclay

CAST 2012 PROSPECTS Hypothesis  The background level of MICROMEGAS is limited by external gammas. CAST 2012 prospects: Improve background level in Sunset side with a new shielding design. Motivated by the low background level obtained at Canfranc and simulation results. R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 11

IAXO PROJECT International AXion Observatory towards a new axion helioscope. CAST PRL2004 most cited experimental paper in axion physics No other technique can realistically improve CAST in a wide mass range Ingredients of CAST: MAGNET X-RAY OPTICS LOW BACKGROUND X-RAY DETECTOR Sensitivity: b = normalized background;  = detector efficiency, a = focusing spot of the optics,  o = optics efficiency, B= magnetic field, L = magnet length, A = cross area and t = time exposure R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 12

IAXO PROJECT Sensitivity scenarios : The new helioscope will require to build a new magnet and dedicated optics. Ultralow-background detectors are required for IAXO. R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 13

IAXO PROJECT Goal: at least c/keV/cm 2 /s, down to c/keV/cm 2 /s if possible. Work on-going: - Experimental tests with current detectors at CERN, Saclay & Zaragoza - Specially: underground setup at Canfranc Laboratory - Simulation works to build up a background model - Design a new detector with improvements implemented - New T2K electronics for Micromegas detectors. - Installation of a new telescope in Sunset Micromegas line in 2013  To adquire experience for the new telescope. An ultralow-background Micromegas for IAXO: R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 14 J. P. Saclay CAST

IAXO PROJECT Sensitivity scenarios prospects: Factor 8 to 30 better in g a  (4000 to 10 6 in signal strength!!) Pessimistic Realistic Optimistic A big part of the QCD axion model region could be explored next decade R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 15 New Generation Axion Helioscope(NGAH) JCAP06(2011)013

ββ0ν would provide crucial information on  Neutrino nature (Dirac or Majorana)  Neutrino mass hierarchy (inverse or direct) Good energy resolution is mandatory to distinguish ββ0ν from ββ2ν ββ2ν standard process, already observed ββ0ν process BSM, only possible if ν is Majorana 3.5% for 0.5 ton 1,0% for 0.5 ton MicroMegas for ββ searches Also required: -Ultra low Background -High masses of isotope -Pattern recognition Also required: -Ultra low Background -High masses of isotope -Pattern recognition R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 16

MicroMegas for ββ searches- Pattern Recognition An extra advantage of a gas TPC + pixelized detectors  Pattern Recognition  GEANT4 simulations + discrimination algorithms are been developing  Basic idea: to select events with a single track ended in two high energy deposits (absorption of the electrons emited in a ββ0ν)  Diffusion affects spatial resolution (Magboltz) High Diffusion, pure Xe Low Diffusion, Xe + TMA ENERGY SPECTRUM FOR THE BACKGROUND IN Xe-TMA R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 17 RoI 2% Q ββ

R&D studies focus on test MMs in HP pure Xe, Energy Resolution improvements and test microbulk readouts in realistic conditions (e- tracks fully contained) with two prototypes as a parallel line in NEXT Experiment. NEXT EXPERIMENT A high-pressure, 100kg gaseous Xe TPC to look for the 0  decay of 136 Xe Q ββ at 2.46 MeV Baseline: an EL TPC, energy measured by PMTs and tracking with SiPM Parallel Study: Microbulk Micromegas with pixelized anode to measure both  Energy through the mesh  Tracks in the pixels MicroMegas for ββ searches R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 18

R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 19 Goal: test small microbulk readouts in diverse conditions of high pressure Xe SETUP UNIZAR Stainless steel 2.4 l volume Low outgassing materials (~10 -6 mbar x l/s) P up to 12 bar UHV specials bakeable Drift 6 cm MICROBULK MICROMEGAS Ø 35 mm 50  m gap microbulk 6 Cu Rings 3 peek columns 6 Resistors 10 MΩ Two different geometries tested. Bigger distance btw holes  Better E Res. NEXT0-MM Prototype- Setup Field Cage Ø hole s 45  m Pitch 75  m Ø hole s 50  m Pitch 115  m 10x10 cm 2 Pixelized anode 12x12 pixels

8 bar 4 bar 1.96 % FWHM MAIN RESULTS - PURE Xe  Microbulk are able to work at pure high pressure Xe !!  Gains ~ 100  Alphas 5.5 MeV from Am-241 source in pure Xe  E = 1.96 % 4bar  E = 4.81 % 8 bar : attachment observed Energy resolution studies R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 20

R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 21 MAIN RESULTS - PURE Xe  Microbulk are able to work at pure high pressure Xe !!  Gains ~ 100  Alphas 5.5 MeV from Am-241 source  E = 1.96 % 4bar  E = 4.81 % 8 bar (attachment observed)  Low energy gammas keV  E = 9.53 % 3.5 bar 3.5 bar keV   E ~ 1.20 % 2.5 MeV for 2 bar   E ~ 2.00 % FWHM for 5 bar Energy resolution studies

1.Determination of the best mixture for Gain and Resolution 1bar) using a Cd-109 source (22.1 keV γ) 92 % Xe + 8 % TMA chosen for HP measurements MAIN RESULTS – Xe Mixtures  Xe - TMA Energy resolution studies Motivation: Xe+TMA forms a Penning mixture.  The excitation energy of the main gas is transferred to additive by collisions, increasing the initial ionization  Improvement in gas gain from 10  10 3 R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 22

2. Energy resolution study for different pressures with the choice mixture Extrapolating  E = % 7bar  E = 1.20 % 2.46 keV (Q ββ ) Extrapolating  E = % 7bar  E = 1.20 % 2.46 keV (Q ββ ) Energy resolution studies MAIN RESULTS – Xe Mixtures  Xe - TMA Ref: Balan,C., Freitas, E. et al, Jinst, 6 P02006 Zaragoza Measurements Ref: Balan,C., Freitas, E. et al, Jinst, 6 P02006 Zaragoza Measurements R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 23

MAIN RESULTS Microbulk are able to work at pure high pressure Xe !! Gains ~ 100 Pure Xenon  Alphas 5.5 MeV from Am-241 source  E = 1.96 % 4bar  E = 4.81 % 8 bar (attachment observed)  Low energy gammas keV  E = 9.53 % 3.5 bar   E ~ 1.20 % 2.46 MeV for 2 bar   E ~ 2.00 % 2.46 MeV for 5 bar Xe- Mixtures  Xe-TMA Higher gains ~10 3  E = % 22.1 keV for 7bar    E = 1.20 % 2.46 keV (Q ββ )  Xe-Neon Higher gains than pure Xe (factor 10) Energy resolution studies R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 24

R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 25 Pure bar reduced T2K electronics version Tracking with Microbulks

Goal: test microbulk readouts in realistic conditions (e- tracks fully contained) Prototype of medium size (1 kg 10 bar) Height 600 mm, φ 396 mm, 74 l inner volume Sensitive volume: height 350 mm, φ 280 mm Tested up to 15 bar Heating and insulation systems Low outgassing materials Field Cage 35 cm drift length 34 rings Inner Ø 28cm Outer Ø 30cm 4 PEEK columns 35 resistors 70 PEEK screws Cirlex foil between field cage and vessel HV FT 330 MΩ total resistivity For drift fields of ~ kV/cm  need to supply 35kV Readout FTs NEXT-MM- Setup J.P. Saclay R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 26

Bulk Micromegas Active region Ø ~30cm 1252 pixels independently read Active region Ø ~30cm 1252 pixels independently read First Tests: Reading the Mesh Rn222 diffused in Ar+2%Isob Mesh-only read All volume active 5.5 MeV 6 MeV 7.7 MeV First pulses (muons and alpha events) First pulses (muons and alpha events) NEXT-MM with Bulk R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 27

First α tracks in Ar NEXT-MM with Bulk with AFTER-based DAQ with a Bulk readout Ar-Iso R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 28 E. Delagnes D. Calvet F. Druillole S. L’Henoret E. Delagnes D. Calvet F. Druillole S. Saclay

NEXT-MM with Microbulk Microbulk readout Actual manufacturing process limit the size of detectors to 30x30 cm 2 To cover NEXT1-MM sensitive surface sectorial detectors were designed and manufactured (r =14 cm) 4 sector full coverage now installed  the larger surface up to now 2 sector installation 4 sector installation R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 29

CONCLUSIONS -Microbulk Micromegas are of large interest for Rare Events -Low radiopurity. Lower values can be obtain taking care of the manufactuing process -Working on background reduction in axion searches: · CAST  Sunset shielding upgrade · Iaxo project  Reduce the background level as much as possible · Special conditions at Canfranc  Promising results, trying to understand what is limiting the actual background level R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 30 - Microbulk Micromegas for double beta decay Simulations to understand background and develop selection cuts Operation at high pressure Xe Energy Resolutions of : 1.96 % (FWHM) at 4 bar of pure Xe for 5.5 MeV  9.50 % (FWHM) at 3.5 bar of pure Xe for 60 keV  % (FWHM) at 7 bar of Xe-8 %TMA for 22kev   1.20 % for Q ββ Bigger prototype ready to characterize larger surface microbulk - Microbulk MMs gather all the characteristics necessary for rare events searches

3 cm Ø 10 x 10cm 2 12 x 12 pixels 15 cm radius 300 pixels Largest microbulk up to now Underway: 30 cm Ø microbulk Microbulk Scaling Up THANK YOU R&D with MICROMEGAS for low background applications: the T-REX project, L. Seguí & J.A. García, UNIZAR, Saclay workshop 31

BackUp

Absolute Gain at differents TMA percentages Energy resolution studies MAIN RESULTS – Xe Mixtures  Xe - TMA

Energy resolution studies MAIN RESULTS – Xe Mixtures  Xe - TMA High O2 dependence 1.Determination of the best mixture for Gain and Resolution 1bar) using a Cd-109 source (22.1 keV γ). 92 % Xe + 8 % TMA chosen for HP measurements

Energy resolution studies MAIN RESULTS – Xe Mixtures  Xe - TMA Energy resolution for each pressure at 92% Xe + 8 % TMA