Response of polymer solid state nuclear track detectors to high energy charged particles

Nuclear Tracks and Radiation Measurements, Vol. 8, Nos. 14, pp. 167-169, 1984. Printed in Great Britain.

0191-278X/84 $3.00 + .00 © 1984 Pergamon Press Ltd.

RESPONSE OF POLYMER SOLID STATE NUCLEAR TRACK DETECTORS TO HIGH ENERGY CHARGED PARTICLES F. Spurn@ Institute of Radiation Dosimetry, Czechoslovak Academy of Sciences, 180 86 Prague, Czechoslovakia

ABSTRACT The response of some polymer solid state nuclear track detectors to high energy protons and helium nuclei was studied. Detectors studied were CR 39; Koda~ materials CN 85, CA 80-15, and LR ll5; and Melinex O, charged particl~s energy v~ried between 0.2 and 0.4 GeV per nuclei. Responses observed are between lO- and 10-4 tracks per particle, following general sensitivity of a detector. Results obtained are analyzed and discussed, some dosimetry applications of detectors are presented. KEYWORDS Track detection, polymer solid state track detectors, high energy charged particles, dosimstry applications of track etching, dosimetry in space INTRODUCTION Solid state nuclear track detectors (SSNTD's) are becoming used also for the detection and dosimetry of high energy charged particles. Polymer SSNTD's without an external radiator can detect such particle also due to secondary charged particles created in a detector material through primary particle s interactions. It is the case for charged particles studied in this work, i.e.protons, and helium nuclei of energies between 0.2 and 4.0 GeV per nucleon. EXPERIMENTAL Irradiation were. carried out at different accelerators installed in USSR. Charged particle s beam monitoring was assured with iQDization chamber~easur~ments and/or using activation detectors (reactions ~ V A l ~ # N a ; 2 7 A l ~ F ; r e s p . X ~ c ~ l l c ) . Its accuracy is appreciated to be about X 6% for proton beams, not better than ± 30% in the case of alphas and carbon nuclei Polymer SSNTD-s studied and the conditions of their etching are given in Table 1. Kodak materials were etched chemically, Melinex 0 electrochemically. CR 39 materials was etched by sequential two-step chemical (at 343 K) and electrochemical (at 298 K) treatment described elsewhere (Somogyi and co-workers, 1982). Layer removed from one-side of a detector by etching was in all cases about 6jum. The tracks revealed by chemical etching were counted using an optical microscope at a magnification of 540x, electrochemically revealed spots were counted using a projection microscope at a magnification of 260x. Background track (or spot) densities were evaluated at the same conditions. 167

168

F. SPURN"~

TABLE i

Polymer SSNTD's studied

Detector CR 39 - Pershore Kodak CN 85 Kodak CA 80-15 Kodak LR ll5 Melinex 0 - ICI

Etching conditions . . . . . . . . . 30~ 2.5 2.5 2.5 30%

KOH; 343 K; N NaOH; 333 N NaOH; 333 N NaOH; 313 KOH; 343 K;

Bulk etchSng rate

/~zm.n-X/

25 kV. cm-l; 9 kHz K K K 40 kV. cm-1; 5 kHz

1.5 4.0 5.0 0.6 4.0

Results of evaluation were statistically treated, they are allways presented with an error expressed as one standard deviation of mean value. RESULTS AND DISCUSSION Responses of chemically etched polymer SSNTD's to perpendicularly incident protons and helium nuclei are given in Table 2. Responses of electrochemically TABLE 2

Responses of chemically etched SSNTD's to protons and helium nuclei Response I) to

SSNTD

protons

O. 2 Ge V CN 85 (1.5 -+ 0.2) CA 80-1~ ll.1 ~ 0.2) LR 115 °) 3 2 03)

0.6 GeV -053) (1.2 ~ 0.2) -05 .... -06 (1.7 ± 0.2)

helium nuclei 2.6 GeV 4.0 GeV -05 (3.9 ~ 0.5) -05 (4.8 ~ 0.5) -05 (2.9 ~ 0.4) -05 (3.7 ~ 0.4) -05 -06 (1.1 - 0.2) -05 ( 8 . 0 1.O) -06

fin tracks per particle. ~
SSNTD

CR-39 Melinex

Responses of electrochemically etched SSNTD's to protons and alphas

protons 0.2 GeV (6.0 ¥+ 0.7) (1.3 - 0.2)

-05 -06

Response I) to helium nuclei 0.5 GeV +

(2.6 ~ 0.3) ( 3 . 7 - 0.5)

-05 -06

4.0 GeV +

(4.0 ¥ 0.5) ( 4 . 0 - 0.5)

-05 -06

RESPONSE FOR POLYMER SOLID STATE NUCLEAR TRACK DETECTORS

169

Re~ponsgs given in Tables 2 and 3 permit to measure particle fluences from lO ~ cm-~, it corresponds to tissue absorbed dosis several tens of~uGy (several mrads). They can be used in such way also to establish the dosimetric characteristics of charged particles field on the board of cosmic vehicles. We have tested them on the board of Saljut 7 during 201 days expedition of Lebedev and Berezovoj. Absorbed doses from cosmic protons established with CA 80-15 detector in different parts of cosmic station were 35; 32; 36; resp.40 mGy; TLD measurements gave in the same places the values of 40; 38; 38; resp.37 mGy. Track detectors permitted i~ the same foil establish also cosmic heavy charged p~rticle fluence ( L E T ~ = ~ 2 0 0 keV.~um-1), it was equal in average to 38 cm -~ per all flight. ~v ACKNOWLEDGMENT Author is much obliged to Drs.V.J.Alejnikov, V.P.Bamblevskij,V.I.Popov, and A.I.Vichrov for their invaluable assistance and help during irradiation. REFERENCES Dajk~ G., and Tu~ek K. (1983);paper presented at this Conference Somogyi G., Dajk6 G., Turek K., and Spurn~ F. (1982). Solid State Nuclear Track Detectors, eds.: Fowler P.H., and Clapham W . H ~ Pergamon Press, Oxford, 445-448