Transcript Diapositive 1

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
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”
mass and measurement time.
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
• New planar Ge detector : our needs regarding low-energy gamma detection
require 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.
• Cryogenerators : We plan to equip one Ge detector with a system
of cryogenerators. Evaluation of possibilities of installation on one
of our detectors is under way.
• Construction of a Radon precision
measuring facility, with a sensitivity of
~ mBq/m3 (Vol. 70 l)
Radon trapping facility
Installation September 2004
Radon trapping facility
Radon purification by adsorption in charcoal
Time during which radon is trapped
in the « filter » : Tr = K(T) M / Q
K(T) : dynamic adsorption coeff.
M : charcoal mass
Q : Air rate
2 charcoal towers :
T1 = -53 C, T2 = -45 C
M = 2 x 450 kg
Vol. clean air : 150 m3/h
Activity 222Rn = 15 mBq/m3