Low background gamma rays spectrometry

SILENA Sp.A, Canberra Ltd., CAEN, Baltic Scientific Instruments, Scionix, IFJ Kraków; 1992-2017


Technical data:

Five low background gamma rays spectrometers with germanium detectors:

  1. 1. HPGe (Broad Energy type), ca. 50 % efficiency, produced by Canberra (USA, 2017), equipped with passive and active shield. Active anticoincidence shield consist of five large plastic scintillation detectors sensitive for cosmic muons produced by Scionix (The Netherlands, 2017), all 5 cm thick and the largest one is 70 cm x 70 cm. Spectra acquisition is done by digitizer CAEN DT 5725 (Italy) what allows for both on-line and off-line spectra obtaining. Passive shield is made of (from inside): 1.5 cm of electrolytical copper, 5 cm of low background lead (2500 years old, having Pb-210 activity from 6 to 8 Bq/kg Pb), 0.2 cm of cadmium, 10 cm of standard lead, 8-12 cm paraffin; electronics: HV supply Canberra 3106 D.
  2. 2. HPGe coaxial, 20% efficiency (home made, 2013, crystal by Umicore) in ultra-low level cryostat by Baltic Scientific Instruments (U or Th at level of one ppb), lead (60 years old) passive shield, HV supply Canberra 3102, amplifier Canberra 2022, MCA Tukan 8k USB.
  3. 3. HPGe coaxial, well type, 15% efficiency (home made, 1999, crystal by Umicore), passive shield (from inside): 1.8 cm of electrolytical copper, 0.2 cm of cadmium, from 5 cm to 12 cm of standard lead; electronics: Amplifier Silena 7611/L, HV Supply Silena 7716 and ADC Silena 7411.
  4. 4. HPGe coaxial, 10% efficiency produced by Silena (1991), passive shield (from inside): 2 cm of electrolytical copper, 0.2 cm of cadmium, 10 cm of standard lead; electronics: Amplifier Silena 7611/L, HV Supply Silena 7716 and ADC Silena 7411.
  5. 5. HPGe planar, (home made, 2004, crystal by Umicore, efficiency about 5%), passive shield (from inside): 5 mm acryl, from 0.3 cm to 1 cm of elecctrolytical copper, 5 cm of standard lead, electronics: HV Supply Canberra 3102, Amplifier Canberra 2022, ADC Silena 7411.
Tracks 3,4,5 are connected to multichannel analyser Silena MB7329 16K using interface Silena 4IADC 8919. The whole spectrometric system is controlled from dedicated PC.


Fig. 1. Ultra-low-level gamma rays spectrometer with active anticoincidence shield (listed as No 1 above)


Fig. 2. Spectrometers listed above as Nos 3,4 & 5.


Fig. 3. Spectrometer in low-background cryostat by BSI (listed above as No 2).


Application:

Measurements of natural and artificial gamma emitters (for example: Cs-137, Be-7, K-40, Ra-226, Pb-210 etc. ) in any kind of solid or liquid sample. Chosing suitable spectrometer we are able to determine activity concentration for nuclides emitting gamma rays in range from 5 keV to 3 MeV at level from several mBq/kg up to hundreds of kBq/kg.

Laboratory in which the equipment is in use:

Environmental Radioactivity Laboratory, Building 6, Department of Nuclear Physical Chemistry (NZ64)