Effect of electric field on cellulose nitrate track detector

Abstract

The influence of d.c. electric fields (0−3.5 × 10 7 V· m −1) applied for different durations (0−2 h) on the track recording characteristics of CA80-15 Kodak Pathe's cellulose nitrate, is reported. It is observed that at a lower etch time of 30 min (2.5. N NaOH, 55°C, without stirring), etched track diameters of normally incident 4 MeV α-particles remain unchanged almost up to the applied electric fields 0−3 X 10 V·m −1 irrespective of the time duration of application of field. Track diameter increases on increasing the field further. At higher etching times (interrupted etching with 30 min step) track diameter and bulk etch velocity V g go on decreasing in general at first, attain a minimum and then show an upward trend at fields ≈3 X 10 V· m −1. However, for field values >3 X 10 7 V· m −1 and longer field times (1.5−2 h), downward trend is indicated. Average bulk etch velocity calculated for a total etch time of 180 min for the samples treated with different electric fields for a maximum time of 2 h, increases first, acquires a maximum and then exhibits a failing trend with increasing fields. Average track etch velocity, V t , however, decreases initially and then increases with the field followed by an abrupt rise at higher field values. The etch velocity ratio, V ( = V t / V g ) shows peaking at 3.5 X 10 7 V· m −1 in the upward direction. The etching efficiency, η, changes from 82% to 97% for the field values changing from 1 X 10 7V·m −1 to 3.5 X 10 7 V·m −1 for a field duration of 2 h and total etch time of 180 min. An attempt has been made to correlate the observed results with the possible increased crystallinity with the application of electric field leading to the electret phenomenon involving molecular orientations and the ozone effects.