low background facilities at lsm
DESCRIPTION
Low background facilities at LSM. Pia Loaiza. ILIAS meeting, Modane January 12 th 2005. Ge detectors at LSM. As S ~ /BDF, Gentiane and IRIS have roughly the same sensitivity at 583 keV and 1461 keV. At present, the sensitivity are, typically, 1 mBq/kg for “reasonables” - PowerPoint PPT PresentationTRANSCRIPT
Low background facilities at LSM
Pia Loaiza
ILIAS meeting, Modane January 12th 2005
Ge detectors at LSM Detector Type Volume Total and peak background rate (counts/day)
40-2700 keV 352 keV 583 keV 1461 keV
MONDEUSE well 220 cc 770 4.2 2.7 5
ROUSSETE well 430 cc 692 4.1 2.9 7.2
ABYMES well 980 cc 828 5.6 5.6 5.6
XXL well 844 cc 821 6.8 <1.8 11.6
HERMINE N 197 cc 313 1.2 1.5 2.3
HELLAZ P 204 cc 515 4.5 0.3 1.4
JASMIN P 380 cc 529 2.0 1.41 1.71
GENTIANE N 215 cc 178 <0.21 0.38 0.65
IRIS P 400 cc 282 1.02 1.46 3.01
At present, the sensitivity are, typically, 1 mBq/kg for “reasonables”mass and measurement time.
As S ~ /BDF, Gentiane and IRIS have roughly the same sensitivity at 583 keV and 1461 keV.
On-going projects at the LSM
• Improvement of a low background Ge detector (IRIS, 400 cc).Prospective construction materials are being measured. Monte Carlo simulations are performed to get the distinct contribution to the background from the assembly materials and to determine the maximum acceptable radioactivities in order to get an improvement of a factor 5 in the detector background.We’ve found a high Th activity (0.13 Bq/kg @ 238 keV) in one of the insulators near the crystal, which need to be replaced by other material.
On-going projects at the LSM
• Cryogenerators : We plan to equip one Ge detector with a system of cryogenerators. Evaluation of possibilities of installation on oneof our detectors is under way.
• Construction of a Radon precision measuring facility, with a sensitivity of ~ mBq/m3 (Vol. 70 l)
• New planar Ge detector : our needs regarding low-energy gamma detectionrequire a new planar Ge (diam = 80 mm, d=35 mm), with a resolution of 0.7 keV at 50-60 keV. Performances of detectors in the market are being evaluated.
Radon trapping facility
Installation September 2004
Radon trapping facility
Time during which radon is trappedin the « filter » : Tr = K(T) M / Q
K(T) : dynamic adsorption coeff.M : charcoal massQ : Air rate
2 charcoal towers : T1 = -53 C, T2 = -45 CM = 2 x 450 kg
Vol. clean air : 150 m3/hActivity 222Rn = 15 mBq/m3
Radon purification by adsorption in charcoal