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Mingay, D.W.; Jonker, W.D.; Smith, B.J.
Atomic Energy Board, Pelindaba, Pretoria (South Africa)1978
Atomic Energy Board, Pelindaba, Pretoria (South Africa)1978
AbstractAbstract
[en] 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
[af]
Die gebruik van deeltjiegeinduseerde X-straalproduksie (PIXE) as 'n navorsings- en ontledingstegniek is in die jongste tyd op groot skaal uitgebou. Energiedispersiewe X-straaldetektore, hetsy Si(Li)- of intrinsieke germanium, met hul besonder goeie oplosvermoe, word oor die algemeen in sodanige stelsels gebruik. 'n Belangrike tekortkoming van hierdie detektore is teltempobeperkings wat ontstaan as gevolg van die ophoping van pulse weens die lang elektroniese tydkonstantes wat vir pulsverwerking vereis word vir die verkryging van die allerbeste energie-oplosvermoe. 'n Stelsel wat op die pulsering van die Raad op Atoomkrag se Van de Graaffversneller se bundel berus, is vir PIXE se analitiese bundelpyp ontwikkel. Wanneer hierdie stelsel deur 'n gebeurtenis gesneller word wat deur die X-straaldetektor geregistreer word, deflekteer dit die versnellerbundel van die skyf af vir 'n tydsduur wat eweredig aan die pulsverwerkingstyd van die detektorelektronika is. Op hierdie wyse word geen verdere pulse ontwikkel nie wat andersins tot ophoping sou lei as gevolg van beskieting van die skyf gedurende die pulsverwerkingstyd in die detektor. Die basiese PIXE-ontledingstelsel en gegewens oor die ophoopsperbaan (PURC) en bundelgeometrie word beskryf. Die doeltreffendheid van die stelsel vir teltempo's tot 12 kHz word bespreek en tipiese PIXE-spektra, die gevolg van roetine-ontledingstudies, word vertoon om die praktiese uitvoerbaarheid van die tegniek te demonstreer. Die eindresultaat van die toepassing van die stelsel was dat die bedryfsteltempo met 'n faktor tien verhoog is, terwyl dit die uiterste in energie-oplossing handhaaf asook 'n voortreflike seinruisverhouding behaal. Die PURC-stelsel word op 'n roetinegronslag vir die ontleding van lugdeeltjie en ander monsters gebruik en deurgaans op alle studie van bundelgeproduseerde X-strale toegepas, waarby die gebruik van Si(Li)- of intrinsiekegermanium-detektore by die Van de Graaffversneller gemoeid isSource
Mar 1978; 15 p; ISBN 086960 674 3; 

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