news: measurements at sub kev energies with spherical detectors g gerbier + i giomataris, j derre, p...
Post on 10-Dec-2015
212 Views
Preview:
TRANSCRIPT
1
NEWS: measurements at sub keV energies with spherical detectors
G Gerbier + I Giomataris, J Derre, P Magnier, A Dastgheibi, D. Jourde, M Gros, E
Bougamont, XF Navick, T Papaevangelou, J Galan, G Tsiledakis IRFU–Saclayon behalf of NEWS collaboration
Introduction to the detectorLow energy investigations -preliminary-
Calibrations, characterisationMeasurements at LSM
NEWS : neutrino coherent scattering measurement 6th TPC Symposium- Paris-2012
2
Drift region
Ampl region
Spherical Proportional Counters• Sphere cavity + spherical sensor + HT• Low threshold (low C)• Fiducial selection by risetime • Flexible (P, gaz)• Large mass / large volume• Robust, simple, cheap, sealed mode• Digitisation @ 1 MHz, soft trigger• 2 LEP cavity 130 cm Ø tested• 1 low activity 60 cm Ø in operation @ LSM
3
Run with Ar/CH4 + 3g 3He @ 200 mb SPC 130cm Ø @ LSM
Rise
tim
e (
s)
Amplitude
210Po5.3 MeV
n capt on 3He 764 keV
222Rn 218Po 214Po
If localised energy deposition, rise time depends of radius(diffusion)
If track, rise time depends on orientation of track(different drift times)
NB: no start=> risetime records place and/or history of energy deposition
derivative
alpha
de/dx
4
Rise
tim
e (
s)
Amplitude
210Po5.3 MeV
n capt on 3He 764 keV
210Po5.3 MeV
from 210Pb @ Cu surface
R = 15 cm
n capt on 3He => p + T
222Rn 218Po 214Po Unwanted Radon daughter deposit on surface
1 23
2 : fast neutron expected here
Taux 400 capt/j
Run with Ar/CH4 + 3g 3He @ 200 mb SPC 130cm Ø @ LSM
5
Calibrations with (external) sources• Saclay SPC, Ar/CH4, 500 mb, 16 mm ball • Calibration with 22 keV from 109Cd => Illustration of volume/surface
identification
8.1 keV from fluorescence of Cu
22 keV8 keV
Volume interactionsLatt 22 keV= 190 cm
Latt 8 keV= 10 cm
Periph interactions
6
Calibration with UV flash lampfor single electron response
Digitised region around where UV induced pulse expected => Look for pulse in 200-260 ms windowAbout 1 in 10 => single electron response
Trigger @ 10 ADU
=> Trigger efficiency for single electron = 54 %
1 electron16 ADU
ms
Single electrondistribution
250 mb, Ar/2%CH4
7
• 37Ar, 35 days lifetime, K a 2.6 keV and Lb 260 ev
• Can be made with Calcium irradiated with fast neutrons
• => first experiments successful !
Volume calibration with 37Ar source
Behaviour at E<300 eV
2.6 keV
8
Spectrum at low energy in surface lab
adu20 eVthresh
600 eV
Exponential rise at low energy
Saclay Ar/2%CH4250 mb
106evts/keV.d
9
Spectrum at low energy in surface lab
adu
Simulated spectrum shape with flat + 1.3 electron mean exponential
=> Source of single electrons ? Many…
600 eV20 eVthresh
10
Detecting coherent neutrino scattering ?• Simulation of expected spectrum from nuclear reactor, on
Ar, with quenching factor and instrumental response• Normalisation to experimental reactor 70 MW• Sphere of 2 m diam, 5 bars
20 ev/keV.kg.d
80 ev/keV.kg.d
>30 eV
30 eV
Equivalent to 120 days exposure
If background is 500 evts/kg.d.keVNbackev= 500*37*120*0.22= 500 000 evtsS/N = 1/20 , N s = 30
eV
11
Data with « SEDINE » the 60 cm low activity detector @ LSM
Argon 39 (1 Bq/kg)
Alpha’s (Po 210 + Rn induced)SEDINE@LSMIn shield
Tot rate surface
Tot rate @LSM
Ar CH4(2%)
SPC130 cm
Pressure mb
Rate Hz
Residual e rate
13
Data with « SEDINE » the 60 cm low activity detector @ LSM – « High energy »
h
222Rn
210Po
In volume
?
in vol
on surf
in vol
Corrected for gain loss (1 % in 4 days)
Inventory of alpha ratesPo210 peak 0.090 Hz 1300/m2.d (« EDW » 400)Rn222 peak 0.011 HzPo214 peak 0.006 HzPo218 peak 0.012 HzTail 0.054 Hz
« Bi-Po » event
NB : 2009 measurement with 130 cm SPC => 0.045 Hz Po210
Degasing of valves ?
218Po
214Po
14
• Example of two 50 mb & 300 mb runs (<24h, non stable conditions)
Data with « SEDINE » the 60 cm low activity detector @ LSM – « Low energy »
Monte carlo simulations on going : see G Tsiledakis talk
eV
keV
« Electron track » spectrum (high RT) evts/kev.d
23 keV
3 keV
300 mb
50 mb
Localised energy deposition in volume Need volume calibration to estimate
cuts and background level Need better estimator for rejectionevts/kev.d
15
Detecting ALPs ?• Axion Like Particles KK postulated to explain high
temperature corona of sun (Zioutas/di Lella, 0207073v1)
• => should decay in 2 gammas with spectra < 3 keV @ rate = 200 /d/m3
• Analysis of pulse shape provide signature• Tests runs in Saclay with 130 cm SPC on-going
derivative
Pulse of 6 keV 55Fe source
Working on background rejection and simulation : J Galan and T Papaevangelou GG IG
a1/a2a1
a2
16
CEA-IRFU/Saclay (GG,IG) ,LSM (F Piquemal), Aristotle University of Tessaloniki (I Savvidis), University of Ioannina (I Vergados), NCSR DemoKritos (G Fanourakis), Hellenic Open University (S Tzamaria) University of Tsinghua Beijing (C Tao), Shanghai Jiao Tong University (K Ni), IHEP-Beijing ( C Yang)University of Saragoza (I Irastorza), Livermore (JR Armendariz)
New Experiments With SpheresNeutrino Experiments With SpheresNew Experiments for Wimps with Spheres
• F : R&D at Saclay and LSM, sensors, high P• F : Coherent neutrino scattering experiment
feasibility (ERC submitted by IG/GG)• G : Neutron monitor (I Savvidis next talk) • C : R&D with SPC 130 cm shipped to Beijing,
investigating large sphere building / tests• F G C : SN monitor, DM …
Tessaloniki 2012
top related