Light and charge collection with a Light and charge collection with a new Micromegas-TPCnew Micromegas-TPC  

Light and charge collection with a Light and charge collection with a new Micromegas-TPCnew Micromegas-TPC  

Leila OunalliLeila OunalliNeuchâtel UniversityNeuchâtel University

CHIPP workshop on Detector R&DCHIPP workshop on Detector R&D11-12 June- University of Genova11-12 June- University of Genova Ionisation

Scintillation

L0

L 22 0 2) : ( , ) ( , ) A Z A Z e e

T G E Z MGT1 22 1 2

02 2

/ ,

2

A

2

2/1 10

T 02

20

00 ,

mMg

gMZEG FV

GT

Double beta decay and the Standard Model (SM)

1 2 2) : ( , ) ( , ) A Z A Z e e e e

-ed(n) u(p)

-

d(n) u(p)

ee

WW e

d(n) u(p)e-eW

d(n) u(p)W e-

e m

If ββ0 exists: Neutrinos are Majorana type

http://www.lhep.unibe.ch/pages/logos.php?lang=en

The EXO detectorThe EXO detector

Why we need a good energy resolution?

Arb

itra

ry u

nit

s

RéalisteOptimiste

2.48 Qββ [Mev]

RealisticOptimistic

= 3.3% @ 2.48 MeV

EXO: a strong anti-correlation observed between scintillation and ionization signals

Combing bothScint & ioniz )S+I= 1.7 %

Ionization only )I= 4.8 %

Scintillation only )S= 10.3 %

Micromegas « Compact »

The Micromegas-TPCThe Micromegas-TPC  

1mm

spacers

Woven wires http://www.bopp.ch/(gamma, RX, UV …)

e-

Cathode

GridAmplification (> 50 m)

Micromesh

Ed ~ 200V/cm

Ea ~ 40-100kV/cmAnode

Conversion + Drift

The Neuchâtel mini-TPC prototypeThe Neuchâtel mini-TPC prototype

miniTPC(10X20cm)• The source position. max of count @ dC-g=18cm

Edrift

• The drift electric field: Ed= 200 V.cm-1.bar-1

• The gap dimension (dgrid-anode ): (75-100-250 µm) High pressure + low voltagesHigh pressure + low voltages

• The quencher choice and %: - Xe + (CF4, isobutene):

double beta decaydouble beta decay - CF4 + (Xe, Ar):

solar solar @ low E @ low E

A higher pressure requires a larger gap

104 @ 4 bar75 µm

Gas:P10, Ed=200 V.cm-1.atm-1

P={1(black), 2(red), 3(green), 4(blue)} atm

250 µm

How to improve the charge collection in Xe?

A small CF4 addition is sufficient

• increases the electron drift velocity in Xe.

CF4 is the best additive for Xe

CF4 addition:

• reduces longitudinal and transversal diffusions.

← improves the charge collection.

P: 1.00 atm, Ed=200 V.cm-1.atm-1,Gap: 100 µm

■ Xe-CF4 (2, 5, 10, 50%)▲ Xe-isobutene (2%)

CF4 is cheap, easy to use, and does not absorb light (t0 possible)

The new Micromegas-TPC for charge & The new Micromegas-TPC for charge &

light collectionlight collection  

Woven wires http://www.bopp.ch/

Gap250 μm

Cathode

Charge read outLight read out

Light read out

Primary ionization (t0)

Advantages of the new device Advantages of the new device

measure the light emitted by ionization. measure the light emitted by ionization. the anti-correlation Charge-Light.the anti-correlation Charge-Light.

Better identification of particles and Better identification of particles and good determination of the energy good determination of the energy deposition localizationdeposition localization..

A well sealed feedthrough

I0

I1

Research & development

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