Radiation Measurements 35 (2002) 301–305 www.elsevier.com/locate/radmeas Swelling in CR-39 and its eect on bulk etch-rate F. Malik, E.U. Khan ∗ , I.E. Qureshi, S.N. Husaini, M. Sajid, S. Karim, K. Jamil Radiation Physics Division, PINSTECH, P.O. Nilore, Islamabad, Pakistan Received 24 May 2001; received in revised form 24 September 2001; accepted 2 March 2002 Abstract The eect of swelling in CR-39, during the etching process has been studied using ‘thickness-measurement’ method. The values of the bulk etch-rate (VB) determined by this method have been corrected in the context of irreversible swelling produced in various CR-39 samples. The results have been compared with those obtained using the ‘mass-measurement’ as well as the ‘ssion fragment track diameter’ methods. The values of experimental VB have been obtained by taking the arithmetic average as well as by tting the Gaussians to the results of a number of CR-39 samples. It is shown that the ‘thickness-measurement’ method is as good as the other methods of determining the bulk etch-rate provided suciently large number of CR-39 samples are used for obtaining the mean value from the Gaussian t of the experimental data. c 2002 Elsevier Science Ltd. All rights reserved. Keywords: CR-39 (Pershore); Swelling; Bulk etch-rate 1. Introduction The solid state nuclear track detectors (SSNTDs) have been usefully employed in a number of dierent elds of science and technology (Durrani and Bull, 1987; Khan and Qureshi, 1999). One of the basic parameters required for the use of the SSNTDs is the bulk etch-rate (VB), i.e the rate at which an etchant erodes the target material in a gen- eral direction. The value of VB is required to be known, for example, for the identication of charge of incident ions and also for determining the other important parameters like track etch-rate and the track revelation eciency. These pa- rameters are required for certain practical applications of SSNTDs. Therefore, it is important to critically assess the methods of measuring VB. In particular, the eect of swelling (Cassou and Benton, 1978) on VB, during the process of etching has to be studied in a systematic way. Out of dierent methods of determining bulk etch-rate (VB) for SSNTDs, one is the measurement of thickness eroded, x, during the etching process of a detector surface ∗ Corresponding author. Tel.: +92-51-220-7230; fax: +92-51- 929-0275. E-mail address: ehsan@pinstech.org.pk (E.U. Khan). in a specic interval of time t VB(x)= x 2t : (1) The factor ‘2’ above takes account of the removal of the thickness from both sides of the at surfaces of a detector sheet. Although the above mentioned method of determining VB is the simplest one, it has been widely known to yield erroneous results (Matiullah et al., 1999; Zhaipengji and Kang Tiesheng, 1988; Waheed et al., 1990; Henke et al., 1986) since the surfaces of CR-39 become uneven after etch- ing. The uneven surfaces yield dierent values of thickness at various locations of the same detector. Moreover, for the short etching time intervals, prior to the stabilization of the water absorption from the etchant (Fromm et al., 1991), the net thickness of CR-39 increases in spite of the surface re- moved. It is perhaps due to these reasons that Eq. (1) has been modied by substituting m=ad in place of x. VB(m; d)= m 2t 1 ad ; (2a) where ‘m’ is the mass of the removed surfaces, ‘a’ is the area of one of the at surfaces and ‘d’ is the detector density after etching. 1350-4487/02/$-see front matter c 2002 Elsevier Science Ltd. All rights reserved. PII:S1350-4487(02)00053-7