Fission fragment tracks

A large number of radiometric techniques have been developed for Pu analysis on tracer, biochemical, and environmental samples (119,120). In general the a-particles of most Pu isotopes are detected by gas-proportional, surface-barrier, or scintillation detectors. When the level of Pu is lower than 10 g/g sample, radiometric techniques must be enhanced by preliminary extraction of the Pu to concentrate the Pu and separate it from other radioisotopes (121,122). Alternatively, fission—fragment track detection can detect Pu at a level of 10 g/g sample or better (123). Chemical concentration of Pu from urine, neutron irradiation in a research reactor, followed by fission track detection, can achieve a sensitivity for Pu of better than 1 mBq/L (4 X 10 g/g sample) (124). 

FIGURE 3.10 A typical fission fragment track in water, showing dense overlap of secondary electrons in the penumbra region (shaded). Core is shown dotted. Reproduced from Mozumder (1969), by permission of John Wiley Sons, Inc. ... 

Fleischer, R. L., and P. B. Price Techniques for geological dating of minerals by chemical etching of fission fragment tracks. Geochim. cosmochim. Acta 28, 1705 (1964). 

Glass dating by fission fragment tracks. J. geophys. Res. 69, 331... 

Fission-fragment tracks in neutron-irradiated zircon and in natural metamict zircon have been observed by Vance and Boland (1975) and by Yada, Tanji, and Sunagawa (1981), respectively, and will be considered in the following section. 

Figure 6(d). Typical fission fragment track in water. Secondary electrons densely overlap to form the sheath Their LET is about two orders of magnitude smaller than that of the core... 

Further developments using track models presented here will be reported later. We propose to include (1) diffusion kinetic studies based on present track models, (2) discussion of thermalization lengths of electrons generated in these tracks, and (3) detailed description of fission fragment tracks. 

In addition to fission-fragment track measurements, thermal neutrons can also be detected by alpha tracks from n, a) reactions with Li or B. Finally,... 

Bhandari N, Bhat SC, Lai D, Rajagoplan G, Tamhane AS, Venkatavaradan VS (1971) Fission fragment tracks in apatite Recordable track lengths. Earth Planet Sci Lett 13 191-199. 

Sidall R, Hiuford AJ (1998) Semi-qttantitative determination of apatite anion composition for fission-track analysis using infra-red nticrospectroscopy. Chem Geol 150 181-190 Silk ECH, Barnes RS. (1959) Examination of fission fragment tracks with an electron microscope. Phil Mag 4 970-972... 

Sources of specifically designed for 252cf-PD applications are commercially available. A carrier-free sample of Cf is electroplated onto a thin nickel foil in the form of a small circular spot with a diameter of 3 mm and is then sealed with a thin nickel foil to contain the Cf. (Fission fragment tracks formed in the source eject Cf atoms from the source a process called self-transfer.) A source used in PD contains about 0.5 tg of Cf and, when located to within a few millimetres of a sample, will deliver 2000-3000 fission fragments into the sample per second. The useful life of the source in a 252Cf-PD mass spectrometer is of the order of 4 years. 

Track-etched membranes are made by exposing thin films (mica, polycarbonate, etc) to fission fragments from a radiation source. The high energy particles chemically alter material in their path. The material is then dissolved by suitable reagents, leaving nearly cylindrical holes (19). 

The second feature of the track structure of multicharged ions—the high concentration of fission fragments in the track s core—manifests itself in the preferential production of low-molecular products in the core of the track. The yields of products with more complicated structure, on the contrary, become smaller, which explains the high yields of H2, CO, and CH4 observed in radiolysis of liquid hydrocarbons induced by multicharged ions.362,364,365... 

Fig. 2. Tracks of fission fragments in mica showing the characteristic forward-backward orientation of the two fragments emerging from the same fission event. By courtesy of R. Brandt (1974) reproduced from G. Herrmann, Phys. Scr. 10A, (1974) 71.

Chadderton, L. T. (1964). Fission fragment damage to crystal lattices track contrast. Proc. Roy. Soc. (London). A280, 110-22. 

---