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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
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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