Single Electron Detection with the Large Volume Spherical Proportional Counter Ilias Savvidis Collaboration S. Andriamonje, S. Aune, E. Bougamont, M. Chapelier, P. Colas, J. Derré, E. Ferrer, G. Gerbier, I. Giomataris, M. Gros, P. Mangier, X.F. Navick, CEA-Saclay, I. Savvidis, University of Thessaloniki P. Piquemal, M. Zampalo, LSM S. Gaffet, P. Salin, LSBB I. Irastorza, University of Saragoza J. D. Vergados, University of Ioannina The outline 1. The spherical proportional counter (SPC) 2. Cosmic Rays and Resolution 3. Sub-keV detection: UV lamp 4. Data analysis 5. Reactor neutrino detection 6. Conclusions
The Large Volume (1m3) Spherical Proportional Counter First prototype The sphere 1 in Modane Volume = 1 m3, Cu 6 mm Gas leak < 5x10-9mbar/s. Gas mixture Argon + 2%CH4.Pressure up to 5 bar Internal electrode at high voltage. Read-out of the internal electrode 15 mm the sensor
The situation today There are three spherical detectors in action: 1. In CEA- Saclay for low energy (sub-kev) detection 2. In the underground laboratory (LSM), in Modane -France, with He-3, for low flux neutron measurements and 3. In Thessaloniki for fast and atmospheric neutron detection.
Radial TPC with spherical proportional counter read-out Saclay-Thessaloniki-Saragoza A Novel large-volume Spherical Detector with Proportional Amplification read-out, I. Giomataris et al., JINST 3:P09007,2008 5.9 kev 55 Fe signal E=A/R 2 Very low electronic noise: low threshold Good fit to theoretical curve including avalanche induction and electronics 20 μs 15 mm Simple and cheap C= R in = 7.5 mm <.1pF single read-out Robustness Good energy resolution Low energy threshold Efficient fiducial cut
Electrostatic field (simulation results) LEFT: 15 mm sphere, 1mm Cu cable covered with 3mm PE RIGHT: 15 mm sphere, 1mm Cu cable covered with 3mm PE + graphite (ground). Distance sphere to graphite 4mm No field correction With field correction
Alpha particle spectroscopy and thermal neutrons Rn-222: 5.49 MeV alpha Po-218: 6.00 MeV alpha Po-214: 7.68 MeV alpha Resolution: σ=1.5% Gas: 98% Ar + 2% CH4,P=200 mbar Underground thermal neutron peak in LSM, after rise time cut. 3gr He-3 in the sphere R=417 evts/d, Φth.neutron = 1.9 10-6 n/cm2/s n + He-3 p + H-3 + 765 kev 765 kev
Cosmic rays Gas: Ne + 5% CH4, P= 500 mbar
Sub-keV detection: UV lamp We are using a pulsed hydrogen lamp Electrons are extracted by the copper internal spherical vessel UV attenuators: 38% transparent mesh MgF2 entrance window UV lamp 38% transparent mesh 1-5 pieces
Electronic noise The calibration with the 8 kev Cu X Ne + 5% CH4, P=500 mbar Electronic noise UV Lamp Cosmic rays UV Lamp Cosmic rays 8 kev Cu-X 8 kev Cu-X after cosmic rays cut-off
Sub-keV detection UV Lamp with the mesh attenuator Ne (85 mbar) + CH4 (15 mbar) UV Lamp+1mesh 600 ev UV Lamp+3mesh 100 ev UV Lamp+4mesh 50 ev UV Lamp flash energy for this position (calibration with the 8keV X-Cu) No mesh ~1 kev 1 mesh ~600 ev 2 mesh ~250 ev 3 mesh ~100 ev 4 mesh ~50 ev 5 mesh ~14 ev
The electronic noise and the background 1 mvolt electronic noise No Lamp?? Cosmic rays and low energy background
UV Lamp data analysis (J. Derre analysis)
I. Giomataris Most likely Secondaries (Compton etc) From Co inside Cu vessel And outside gamma backgrounds
Neutrino-nucleus coherent elastic scattering (I. Giomataris) ν + Ν > ν +Ν σ N 2 E 2, D. Z. Freedman, Phys. Rev.D,9(1389)1974 T N =2 m N (E ν cosθ) 2 /{(m N + E ν ) 2 (E ν cosθ) 2 } A. Druikier, L. Stodolsky, Phys.Rev.D30:2295,1984 JI Collar, Y Giomataris - NIMA471:254-259,2000 H. T. Wong, arxiv:0803.0033-2008 PS Barbeau, JI Collar, O Tench - Arxiv preprint nucl-ex/0701012, 2007 Nuclear reactor measurement with present prototype At 10 m from the reactor, after 1 year run (2x10 7 s), assuming full detector efficiency: - Xe (σ 2.16x10-40 cm 2 ), 2.2x10 6 neutrinos detected, T max =146 ev - Ar (σ 1.7x10-41 cm 2 ), 9x10 4 neutrinos detected, T max =480 ev - Ne (σ 7.8x10-42 cm 2 ), 1.87x10 4 neutrinos detected, T max =960 ev Challenge : Very low energy threshold We need to calculate and measure the quenching factor Application : Remote control of nuclear reactors
Sensitivity for reactor neutrino detection The number of events in one day for the present spherical TPC dete P=5 Atm, R=.65 m, T=300 0 K, anti-neutrino flux= 10 13 /cm 2 /s target anti ν e (QF, no Thr) anti ν e (QF ) Thr = 1 electron Xe 2325 825 275 anti ν e (QF ) Thr = 2 electron Ar 430 292 210 This a considerable signal Argon is a good candidate But we need to build a new detector with appropriate shiel Background at 1 electron level?
Improvements Better calibration, lower than the 8keV Cu-X New sensor with lower capacitance Decrease of the electronic noise Decrease of the low energy background The next step Next experiment in the underground laboratory in Modane (LSM), were the cosmic ray background is very low. Reactor measurements for neutrino detection (CEA-Saclay experiment) Since the detector is sensitive to low energy recoils, it is possible to measure the fast neutron recoils (Thessaloniki experiment)
CONCLUSIONS The spherical proportional counter is a suitable for alpha particle spectroscopy (with σ= 1,5%) and low flux neutron detection The detector is sensitive to sub-kev UV irradiation up to several tenths ev (few electrons and single electron detection) We need to improve the system to be possible to measure the reactor neutrino recoils.
Sub-keV calibration: UV lamp We are using a pulsed hydrogen lamp MgF 2 entrance window Electrons are extracted by the copper internal spherical vesse UV attenuators: 38% transparent mesh Total drift time (μs) P= 10 mbar? P= 50 mbar P= 100 mbar P= 200 mbar P= 500 mbar Ar 25 50 75 Ne 80 100 145 I. Giomataris