Energy resolution results for Microbulk MICROMEGAS at high energy and pressure.

Alfredo Tomás AlquézarUniversidad de Zaragoza

on behalf of the collaborationCollege de France: P. Gordetzsky and P. Salin

IRFU-Saclay: E. Ferrer-Ribas and I. GiommatarisZaragoza: T. Dafni, F.J. Iguaz, I. G. Irastorza and A.

Tomás

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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Outline

The subject: Microbulk µicroMegas

The motivation: A NEutrino Xenon gas TPC for decay searches

The tests: high energy & pressure resolution Ar + isoC4H10 (already presented, Amsterdam I.G. Irastorza) pure Xe (preliminary)

Results (preliminary)

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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Microbulks (not to mistake for bulks)

Micromesh5µm 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)

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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Mibrobulk simplest prototype

100 µm

40 µm

cooper mesh

kapton pillards

epoxy support

mesh contactanode contact

cooper anode

25 m

m

55Fe

12,3% FWHM

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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0 & NEXT Neutrinoless Double Beta ()

•Neutrino: Majorana or Dirac?

•Absolute scale of netrino’s mass

NEXT

•Monolithic Xe detector

•Topological signature:

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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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.

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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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

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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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

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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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:

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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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

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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Pure Xe at 3 bar

4,9% FWHM

7,8% FWHM

4,9% FWHM

7,8% FWHM

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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Pure Xe at 4 bar

4,5% FWHM

14,4% FWHM

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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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

RD51, Paris 14th October Alfredo Tomás Alquézar, Universidad de Zaragoza

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Microbulks represent the state of the art in icroMegas in relation to energy resolution (less than 15% @5,9 keV guaranteed in Ar + isoC4H8 at atm pressure).

Results in pure Xe at high energy (5,6 MeV 241Am ) & pressure:

Expected improvements (PROSPECTS) in Better gas system quality Quencher Addition of Light readout icroMegas geometry

Summary

Gain higher than 180