Presentation is loading. Please wait.

Presentation is loading. Please wait.

Micromegas-TPC development for rare event detection

Similar presentations

Presentation on theme: "Micromegas-TPC development for rare event detection"— Presentation transcript:

1 Micromegas-TPC development for rare event detection
3rd symposium on Large TPCs for low energy rare event detection, Paris, December 2006. Leila Ounalli Neuchâtel University

2 Restrictive conditions for rare event detection
Big detector mass (high pressure), Radioactive background as low as possible (underground laboratory + radio-pure components), Good energy resolution (FWHM), High gas gain (collected charge / initial charge).

3 The eye and the retina Cones Sticks Light Optic nerve Brain
(analyze, classify, memorize)

4 The TPC and Micromegas spacers Dave Nygren (1970) Woven wires
1mm spacers Cathode Grid Amplification (> 50 m) Micromesh Ed ~ 200V/cm Ea ~ kV/cm Anode Conversion + Drift (gamma, RX, UV …) e- Dave Nygren (1970) Woven wires Micromegas « Compact » analyze, classify, memorize.

5 The Neuchâtel mini-TPC
miniTPC(10X20cm) The source position. max of dC-g=18cm Edrift The drift electric field choice: Ed= 200 The gap dimension (dgrille-anode ): ( µm) High pressure + low voltages The quencher choice and %: - Xe + (CF4, isobutene): double beta decay - CF4 + (Xe, Ar): solar low E

6 Why we replace the MWPC by the Micromegas micro-pattern?

7 Charge deviation from their trajectories. (RE + ξ ) bad (50% @ 6 keV)
Contours of V near the amplification gap x10-3 Y-Axis[cm] X-Axis[cm] Comparison with MWPC’s Y-Axis[cm] X-Axis[cm] Circular form: Charge deviation from their trajectories. (RE + ξ ) bad 6 keV) rectilinear: E uniform: // of electrons. (RE + ξ ) good 6keV with 1 bar of CF4)

8 How to operate the Micromegas-TPC at higher pressures?
The increase of the gap amplification permits a good charge collection at high pressure C G Amplification (75, 250) m Micromesh A Conversion + Drift

9 Why we choose a gap of 250 µm? 250 µm 4 bar 75 µm

10 How to improve the charge collection in Xe?
A small CF4 addition is sufficient

11 CF4 is the best additive for Xe
← improves the charge collection. P: 1.00 atm, Ed=200, Gap: 100 µm ■ Xe-CF4 (2, 5, 10, 50%) ▲ Xe-isobutene (2%) CF4 addition: increases the electron drift velocity in Xe. reduces longitudinal and transversal diffusions.

12 Optimal parameters Ed= 200 Gap: 250 µm.
Gas: Xe(98)CF4(2) Make preliminary tests in the mini-TPC of Neuchâtel (241Am).

13 The Xe(98)CF4(2) gain and the energy resolution @ 60 keV at different pressures
1.05 atm 2.01 atm 3.00 atm 4.00 atm Gas: Xe(98)CF4(2) Ed= Source: 241Am (37kBq) ▲ 8.05 keV Cu-Kα keV Xe-Kα 103

14 Pulse height spectra of 241Am source in Xe(98)CF4(2) with a Micromegas-TPC
8 keV G ≈ 1340 30 keV G ≈ 1670 30 keV 8 keV Cu-Kα Xe-Kα Pulser 1 bar 3 bar

15 Radio-pure and radio-active components

16 The Germanium detector : gamma spectrometry
Ge (400 cm3) “Vue-des-Alpes”

17 Copper (TPC+rings+cathode). Glue (araldite). Grid (Stainless steel).
Kevlar Resin-epoxy Lead. Copper (TPC+rings+cathode). Glue (araldite). Grid (Stainless steel). insulators (delrin, teflon) Radio-pure 2614 x104 Printed-circuit (resin-epoxy). Resistances (ceramic). Solder (210Pb) Radio-active

18 Gotthard results

19 The Gotthard TPC diameter: 50 cm TPC (60X70cm) Micromegas Gap: 250 µm
Gotthard-TPC low energies (241Am, 133Ba). Estimate the radioactive background of the TPC. - Find the sources of noise: Measure the radioactivity of components using a Ge detector “Vue-des-Alpes”.

20 The compact Micromegas is tested before being installed

21 Micromegas (50 cm of diameter): (Am and Ba) sources effect
81 keV (133Ba) 60 keV (241Am) 60 keV (241Am) The Compton plateau (133Ba)

22 The behavior of the background registered in the Gotthard TPC
1 bar of P10 gas 46 keV 3 bar of P10 gas

23 Conclusions We improve the energy resolution when we replace the MWPC with a Micromegas. Xe(98)CF4(2): ideal for double beta search: high gains, good efficiency, good (energy, spatial and time) resolutions. Increase the gap (amplification): permits a good charge collection in Xe and go up at higher pressures. Micromegas in compact: (50 cm) showed high efficiency and good energy resolution.

Download ppt "Micromegas-TPC development for rare event detection"

Similar presentations

Ads by Google