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Can dosimetric quantities describe charged particle tracks in matter?
340
Abstracts--1 lth ICSSNTD
SESSION l: FUNDAr~ENTAL r"ECHANISMS Chairman: E. Schopper
CAR DOSIMETRIC QUANTITIES DESCRIBE CHARGED PARTICLE TRACKS IN MATTER? Herwig G. Paretzke GSF - Institut fiir Strahlenschutz D-8042 Neuherberg, W.-Germany
ABSTRACT Appropriate classification of relevant microscopic or macroscopic changes in a target material after interaction with ionizing radiation represents one of the most important objects in radiation research. Most classification concepts proposed for analytical work on radiation effects and most methods actually used in practical radiation measurements are of dosimetric nature, i.e, they are based on the assumlption that ener~Dr deposited in a mass element or derived quantities are adequate physical measures for interaction patterns of charged particles as regards physical, chemical or biological effects. The validity of the assumptions underlying implicitely dosimetric concepts is discussed in this paper as well as their usefulness and shortcomings. Arguments are put forward that analysis based on dosimetric quantities only can not he expected to lead to further improvements in our understanding of radiation effects, This is mainly due to their inadequate concepts of information reduction. To overcome these fundamental problems, further work is urgently needed on the development of better classification concepts for charged particle track structures. A possible approach to this problem is outlined, which is based on the locations of primary activations themselves.
I.R., U.V. AND E.S.R. STUDIES ON PLASTIC TRACK DETECTORS IRRADIATED BY HEAVY IONS A. Chambaudet
(LA ]76) and J. Roncin (LA 75)
Laborateire de Chimie Physique B~timent 350, Avenue Jean Perrin 91405 ORSAY (France)
ABSTRACT Generally the track formation in plastics is associated with chemical damage. In order to investigate the latter, three analytical techniques have been utilised : I.R. and U.V. optical absorption spectroscopy and for all the plastics (including CR 39) E.S.R. spectroscopy. As an electron bombardment does not give rise to such etchable tracks, we have compared the effects of two types of radiation : Ar or Kr ions and 1,6 MeV electrons. On the other hand, as a thermal treatment anneals the latent tracks, the E.S.R. signal is followed versus annealing temperature up to total annealing. The dose effect is also widely investigated. We conclude that, a track effect can be a mere dose effect in most cases (e.g. polyethylene, polypropylene,...) ; in other cases, the formation of etchable tracks requires a time correlation in addition to the spatial correlation. We suggest that the existence of heavy ion latent tracks might be correlated with the formation of carbon-like radicals such as are produced in polymer pyrolysis. In the special case of teflon, the carbon like radicals are converted so quickly to RO~ radicals that subsequent etching of the tracks is not possible.
Abstracts--1 lth ICSSNTD
SESSION l: FUNDAr~ENTAL r"ECHANISMS Chairman: E. Schopper
CAR DOSIMETRIC QUANTITIES DESCRIBE CHARGED PARTICLE TRACKS IN MATTER? Herwig G. Paretzke GSF - Institut fiir Strahlenschutz D-8042 Neuherberg, W.-Germany
ABSTRACT Appropriate classification of relevant microscopic or macroscopic changes in a target material after interaction with ionizing radiation represents one of the most important objects in radiation research. Most classification concepts proposed for analytical work on radiation effects and most methods actually used in practical radiation measurements are of dosimetric nature, i.e, they are based on the assumlption that ener~Dr deposited in a mass element or derived quantities are adequate physical measures for interaction patterns of charged particles as regards physical, chemical or biological effects. The validity of the assumptions underlying implicitely dosimetric concepts is discussed in this paper as well as their usefulness and shortcomings. Arguments are put forward that analysis based on dosimetric quantities only can not he expected to lead to further improvements in our understanding of radiation effects, This is mainly due to their inadequate concepts of information reduction. To overcome these fundamental problems, further work is urgently needed on the development of better classification concepts for charged particle track structures. A possible approach to this problem is outlined, which is based on the locations of primary activations themselves.
I.R., U.V. AND E.S.R. STUDIES ON PLASTIC TRACK DETECTORS IRRADIATED BY HEAVY IONS A. Chambaudet
(LA ]76) and J. Roncin (LA 75)
Laborateire de Chimie Physique B~timent 350, Avenue Jean Perrin 91405 ORSAY (France)
ABSTRACT Generally the track formation in plastics is associated with chemical damage. In order to investigate the latter, three analytical techniques have been utilised : I.R. and U.V. optical absorption spectroscopy and for all the plastics (including CR 39) E.S.R. spectroscopy. As an electron bombardment does not give rise to such etchable tracks, we have compared the effects of two types of radiation : Ar or Kr ions and 1,6 MeV electrons. On the other hand, as a thermal treatment anneals the latent tracks, the E.S.R. signal is followed versus annealing temperature up to total annealing. The dose effect is also widely investigated. We conclude that, a track effect can be a mere dose effect in most cases (e.g. polyethylene, polypropylene,...) ; in other cases, the formation of etchable tracks requires a time correlation in addition to the spatial correlation. We suggest that the existence of heavy ion latent tracks might be correlated with the formation of carbon-like radicals such as are produced in polymer pyrolysis. In the special case of teflon, the carbon like radicals are converted so quickly to RO~ radicals that subsequent etching of the tracks is not possible.