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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
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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)
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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)
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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
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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:
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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.
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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
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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
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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:
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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
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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
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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
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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
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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