Stopping powers of mylar for protons from 0.40 to 3.25 MeV

Abstract

Stopping powers of mylar have been measured for protons of 0.40 to 3.25 MeV from the accelerator at Nara Women's University. The experimental setup and procedure are quite similar to those of the previous experiments [e.g., Nucl. Instr. and Meth. B 103 (1995) 225; Nucl. Instr. and Meth. B 47 (1990) 111]. The results agree well with the calculated values of the ICRU Report 49 for protons above 1.50 MeV. For protons under 1.50 MeV, however, our results are higher as the energies decrease. The mean excitation energy, viz., the I-value, for mylar has been extracted from the measured stopping power data. The I-values extracted with Bonderup's [K. Dan. Vidensk. Selsk. Mat. Fys. Medd. 35 (1967) no. 17] and Bichsel's [UCRL Report No. 17538 (1967); ICRU Report 37 (1984)] shell corrections are 81.7 and 80.8 eV, respectively, and agree well within their uncertainties. They are also in good agreement with the previous I-values of 80.8 and 80.2 eV [Nucl. Instr. and Meth. B 103 (1995) 255] obtained from measurements at 4.0–11.5 MeV with the respective shell corrections and also with the value recommended in ICRU Reports 37 and 49, 78.7 eV, the uncertainty of which is stated to be 5–10%. The I-values obtained by combining the previous data and present stopping power data are 81.8 and 80.9 eV with the respective Bonderup's and Bichsel's shell corrections.