Low-level beta GM multicounter


Low level Beta Counter 


Low-level gas flow beta multicounter system for the measurement of 5 samples simultaneously.
The basic part of the Risø low-level beta multicounter system is a gas-flow unit with dimensions of 50x100x250 mm which incorporates five individual GM sample counter elements and a common guard counter.
The guard counter reduces the cosmic-ray background by using anticoincidence technique. Each sample counter element is provided with an aluminized Mylar window of density < 1 mg/cm2 and diameter 25 mm. The counters are gas-flow types designed for 99 % Ar/1 % isobutane or 99 % Ar/1% propane counter gas. A sample slide allows five samples to be inserted into the multicounter. These samples are measured simultaneously. A lift mechanism minimizes the sample-to-window distance to obtain optimal efficiency. The multicounter is normally placed inside a lead shielding of 100 mm thickness to reduce the ambient background radiation.



  • Sample size: 25 mm diameter.
  • Counter gas: 99% Argon N48/1% Isobutane N25 (or 99% Argon/1% propane N25).
  • Sample counter elements: 25 mm diameter with aluminized mylar window (<1 mg/cm2).
  • Guard counter: 100 mm x 250 mm x 12 mm.
  • Background in 100 mm lead shieldine: <0.2 CPM (typically <0.15 CPM.
  • Efficiency: 90Sr/Y (activity prepared on a 25 mm diameter filterpaper attached to a 5 mm thick Thallium disc): 54%. 36Cl (activity deposited on a 25 mm. diameter x 5 mm thick plastic disc): 44%. 14 C (1 mm. thick acrylic source, 25 mm diameter): 24%.
  • 99Tc (Electro plated on steel disc): 42%.
  • Size: Mechanical unit: 50 x 100 x 250 mm. (Other dimensions on request) disc./anticoincidense module: 250x250x65 mm.


External USB interface 


USB upgrade
An external USB interface is now available for the Risoe beta multicounter, replacing the original PC-card. This now allows the use of a laptop computer to control the counter.
The new system can run up to 4 counters simultaneously, on the same pc. A new improved version of the software is available with the new interface.


Software update
An update of the software running the beta counter is available for download here