1. Energy resolution results for Microbulk MICROMEGAS at high energy and pressure. Alfredo Tomás Alquézar Universidad de Zaragoza on behalf of the collaboration College de France: P. Gordetzsky and P. Salin IRFU-Saclay: E. Ferrer-Ribas and I. Giommataris Zaragoza: T. Dafni, F.J. Iguaz, I. G. Irastorza and A. Tomás

2. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 2 Outline The subject: Microbulk µicroMegas The motivation : A NEutrino Xenon gas TPC for  decay searches The tests : high energy & pressure resolution  Ar + isoC 4 H 10 (already presented, Amsterdam I.G. Irastorza)  pure Xe (preliminary) Results (preliminary)

3. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 3 Microbulks (not to mistake for bulks) Micromesh 5µm copper Kapton 50 µm Readout pads Readout plane + pillars + mesh manufactured simultaneously. Uniformity of amplification gap up to few microns. Next generation of MM for CAST (3 microbulks + CCD)

4. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 4 Mibrobulk simplest prototype 100 µm  40 µm cooper mesh kapton pillards epoxy support mesh contactanode contact cooper anode 25 mm 55 Fe 12,3% FWHM

5. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 5 0  & NEXT Neutrinoless Double Beta (  ) Neutrino: Majorana or Dirac? Absolute scale of netrino’s mass NEXT Monolithic Xe detector Topological signature:

6. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 6 NEXT: energy resolution requirement Energy is the main observable for a  decay experiment. Good resolution is essential to distinguish the ultimum and unavoidable background: the  spectrum.

7. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 7 P exhaust oxisorb The tests: set up  Simple anode microbulk  HP 2 liter TPC (from HELLAZ)  Single run: full TPC (through oxisorb) and isolate gas Lower part Upper part

8. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 8 The tests: Ar + 2% isobutane  Already presented (I.G. Irastorza, Amsterdam RD51 meeting).  1,5-2% FWHM along the 2-5 bar pressure range.  Landau deconvolution points out 0,7% FWHM intrinsic  icroMegas resolution.  Very similar results obtained in a wide range of parameters like: electric drift field, gain, electric fields ratio, electric drift field homogeneity, etc. 4,75 bar

9. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 9 The tests: pure Xe (PRELIMINARY)  Enough gain was achieved only with Xe.  Resolution and gain were not so robust as in Ar, moreover some peak’s defects indicated the presence of attachment.  Pulse shape offline analysis can help to clarify this situation:

10. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 10 Pure Xe at 2 bar  Risetime-Amplitude correlation hadn’t been observed in Ar measurements.  Different slopes at variable conditions on gas purity convinced us the effect is really due to attachment. 4,2% FWHM 2,8% FWHM

11. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 11 Pure Xe at 3 bar 4,9% FWHM 7,8% FWHM 4,9% FWHM 7,8% FWHM

12. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 12 Pure Xe at 4 bar 4,5% FWHM 14,4% FWHM

13. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 13 Pure Xe: Gain ? ? Product Q primary · G seems to be the limitation, independent on pressure when working at high Qp and (not so) low gain. At least 180

14. RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza 14 Microbulks represent the state of the art in  icroMegas in relation to energy resolution (less than 15% @5,9 keV guaranteed in Ar + isoC 4 H 8 at atm pressure). Results in pure Xe at high energy (5,6 MeV 241 Am  ) & pressure: Expected improvements (PROSPECTS) in  Better gas system quality  Quencher  Addition of Light readout   icroMegas geometry Summary Gain higher than 180