Method and apparatus for assaying the lithium isotope of mass no.6

摘要

The lithium-6 content of a sample is measured by directing on to the sample a beam of deuterons and detecting the [alpha] particles produced by the reaction Li6 + d # 2[alpha] which are simultaneously emitted by the sample in directions corresponding to opposite directions in the centre of mass system and with energy within a given range. Collimated 700 keV deuterons from an accelerator impinge on a carbon or plastics holder carrying a film of material to be analyzed for Li6. Silicon junction detectors 10, 10' located at 85 degrees to beam direction detect [alpha] particles emitted at right angles to the beam in the centre of mass system. The outputs of detectors 10, 10' are fed via amplifiers 14, 14' 16, 16' and single channel pulse height analyzers 18, 18' to a coincidence circuit 20, which gives an output pulse only when detectors 10 and 10' simultaneously receive [alpha] particles of the same energy. A pulse height analyzer 26 may be provided to determine the height difference between spectrum peak and the background level and apply a signal to scaler 22 to compensate for background. In order to compensate for variations in the deuteron beam intensity the same may be measured by a Faraday cage 23 which receives the beam after it has passed through the sample and feeds a current integrator 24. In a modification Fig. 2 (not shown), the deuteron beam intensity is monitored by scattering some of the deuterons which have passed through the sample on to a silicon junction detector by means of a gold foil.