Common analysis of background spectra of proportional counter filled with krypton enriched with 78Kr and natural krypton Vladimir Kazalov Baksan Neutrino Observatory INR RAS "PARTICLES and COSMOLOGY“, April 16 - 21 , 2007, Baksan Valley

Ju. Gavriljuk, V. Gavrin, A. Gangapshev, V. Kazalov, V. Kuzminov, N. Osetrova Institute for Nuclear Research of the Russian Academy of Sciences, Moscow Russia S. Panasenko, S. Ratkevich Karazin Kharkiv National University, Kharkiv, Ukraine The work is performing in the frames of a Presidium RAS Fundamental Research Program “Neutrino Physics” and Supported by RFBR grant №04-02-16037

2ek + 2 (2.88 MeV) Theory: Experiment:

} = 0.481 еа к assumption Se**-----------------> Se*+Se* Kab=12.652 keV, 2Kab=25.3 keV Ka1=11.221 keV 1.00 Ka2=11.181 keV 0.52 Kb1=12.491 keV 0.21 Kb2=12.651 keV 0.01 wk=0.596 x-ray we=0.404 e-Auger Se* 0.4042 =0.163 } = 0.481 0.5962 = 0.355 еа к

Schematic diagram of 2k-capture event 78Se**  78Se 78Se**  78Se

Parameters of the counter 1. Body’s material Cu 2. Total length, mm 1160 3. Fiducial length, mm 595 4. Outer diameter, mm 150 5. Inner diameter, mm 140 6. Central anode material, mm g.p.tan., 0.010 7. Total volume, l 11.0 8. Fid. Volume, l 9.16 9. Pressure, at 4.51 10. Capacity, pF 31 11. Anode wire resistance , Ohm 613 Æ140 Æ150 Cross-section of the counter + - anode

Low background shield  1760 mm    15 cm lead 8 cm borated polyethylene 18 cm copper

View of installation

Electric scheme of the setup PA1 & PA2 – preamplifiers A1 & A2 – amplifiers CS – coincidence scheme DO – digital oscilloscope

Real pulse sample

Spectrum of 109Cd (88 keV) Events / keV Energy, keV

Background of 78Kr(T=8400 h) Events / keV Energy, keV

Background of Krnat (T=3039 h) Events / keV Energy, keV

Comparison of 78Kr with Krnat Events / keV Energy, keV

Comparison of 78Kr with Krnat Events / keV Energy, keV

Three point pulse 17

Results: Events / keV Energy, keV

Number of Kr-78 atoms - 1,08·1024 Registration efficiency for 3(·)-events - 0,809 Probability for 3(·)- events - 0,355·0,985 Effectiveness of selection for 3(·)- events - 0,43