PIXE-PURC-Particle-Induced X-Ray Emission Pile-Up Rejection Circuit. A Dynamic Beam-Pulsing Technique for Pile-Up Rejection in Charged-Particle-Induced X-Ray Emission Analytical Studies

摘要

The use of Particle-Induced X-ray Emission (PIXE) as a research and analytical technique has been widely exploited of late. Energy-dispersive X-ray detectors, either Si(Li) or Intrinsic Germanium, having extremely good energy-resolution characteristics, are in general used in such systems. These detectors suffer a major disadvantage with respect to their count-rate limitations regarding pile-up difficulties. This arises from the long electronic time constants required for pulse processing in order to achieve the ultimate in energy resolution. A pulsed-beam system, based on the Van de Graaff accelerator of the Atomic Energy Board, has been developed for the PIXE analytical beam line. This system, when triggered by an event recorded by the X-ray detector, deflects the beam from the target for a time commensurate with the pulse processing time of the detector electronics. In this way no further pulses as a result of beam bombardment of the target are generated in the detector during the pulse processing period, which otherwise would lead to pulse pile-up being generated. The basic PIXE analysis system is described and the Pile-Up Rejection Circuitry (PURC) and beam geometry are detailed. The performance of the system for count rates up to 12 kHz is specified, and typical PIXE spectra resulting from routine analytical studies are presented to demonstrate the efficacy of the technique. The net result of the application of the system has been to increase the operational count rate by a factor of 10 while retaining both the ultimate in energy resolution of the detector, as well as achieving a superior signal to noise ratio. The PURC system is in routine use for the analysis of air-particulate and other samples and is applied to all beam-generated X-ray studies involving the use of Si(Li) or Intrinsic Germanium detectors on the Van de Graaff accelerator. (Atomindex citation 10:433877)