Pergamon Nud Tracks R a d ~ Meas., Vol. 22, Nos I-4, pp. 7'?9-782, 1993 Ebevmr Scuce Lai Pnmmd ia Omm Britain. 0969-907S~ $6.00+.00 ELECTRON MICROSCOPY ANALYSIS OF KRYP'IDN ION TRACKS INDUCED IN DURANGO APATITE M. GRIVET, M RE2ETEZ, A CHAIVflIAUDET and N. BEN GHOUMA Lalmratomre de Ml~roanalysesNucl~ures, Facult6 des Sciences et des Techmques, Umvermt~ de F, ranche-Comt~, 16 mute de Gray, 25030 Besanqon Cedex, France ABSTRACT The Irack annealing phenomenon, which occtn in a healed mineral containing uranium like apatite, is analysed using the Immmmitted electron microscopy (TEM) associated to the platinium shadowed carbon replica method. Tbe diamelers of 86Kr (1,66 MeV/nucleon) ion Iracks induced normally to the observation plane are meammd dm-ing m etching stage with a very low concma~_m4_ etchamt (HNO3 1%). Tbe distribution of Irack diametm, s in a sample, and its variau'm following the annealing mount the almite knew, lead us to agree with the track mgisltmion model which let appeg more than one micsmmpic defect struclme ~ et aL, 1981). This model cammt be observed with only unannealed etched Irucks, but is clearly highlighted by the thermal annealing of nuclear trucks In this mineral. Tbe opening uack profile is analysed as a determination of d~e etching _sp__'~___ variation versus the distsnce m the ion Irajeclory. The variation is shown to be dependent on the "cs~t~ga~y of the apatite. The diffenmt etching speeds, ~.la~ve to the orientation with the c-axis of the apetite, influence the track shape fcf long etching times. The etched pit figure is not symetrical, and lm~at in the c-axis direction a much mole width opening than the etched track diamet~. Finaly, the !A!,~altrack shape and the etched pit are supposed to be sensitive to the e~tumt strength. KEYWORDS Ion track; carbon replica; electron microscopy; fission track; apatite; Durango. INTRODUCTION Nuclear tracks can be observed in uranium-contsining min~ like atmtites, sphenes and zircons. In such a case, it is the isotope 238 of this element which spontaneously produce~ two fission fragments ejected in opposite diructicms. Consequently, a population of spontaneous latent tracks is recorded in the mineral throughout its histmy. These wacks can be observed with an optical microscope aftex an aplm3pdate chemical etching (Fleischer eta/., 1964). The detmminafion of the etched track density enables the mineral to be dated. Secondly, latent fmsion tracks ate sensitive mainly to time and temperature, that is, the etchable length of an individual track is shortened by an amount detemmine¢! by the time/temperature it has experienced. The study of their characteristics can thus provide impemnt information on the mineral's thermal history. In ~ tO study this annealing phenomenon, Irucks we~ generated in Dumngo apafite, normally to the surface, by heavy ions ~ m GANIL (Caen, Fnmce), ~ a totM mmesling of the sponmucons eoes. 86Kr ion was chosen as iris similar to speemmeousfission fragments with m energy of 1.66 lVleV per nucleon. IMklmuemems of the etched Iruck dismetms were taksn for severalmmeMing mira, by ~ o n of ~ ~ with elucuron microscope. This work is aimed at showing the link betwe~ the default distribution, observed through the etching speeddism'bution, and the degreeof armealmg,and at ___deJ~_ "bing the fission track annealing in apme. 779