On the linearity of the high-temperature emission from 7LiF:Mg,Ti (TLD-700)

It is known since the early 1970s [e.g., Jähnert, B., 1972. The response of TLD-700 thermoluminescent dosemeters to protons and alpha particles. Health Phys. 23, 112-114.] that the high-temperature emission (HTE) from LiF:Mg,Ti thermoluminescence (TL) phosphors shows a distinctly different LET dependence than the dominant glow peak 5. This behaviour of the high-temperature structure can be attributed to the earlier onset of supralinearity compared to peak 5. The relative TL-efficiency of the high-temperature peaks after heavy ion irradiation with respect to 60Co was calculated by Waligórski and Katz [1980a. Supralinearity of peak 5 and 6 in TLD-700. Nucl. Instrum. Meth. 175, 48-50; 1980b. Supralinearity of peak 5 and 6 in TLD-700. Nucl. Instrum. Meth. 172, 463-470.], demonstrating that levels far exceeding 1 can be reached. The HTE from LiF:Mg,Ti has been applied in various ways, e.g., to determine an “effective” LET under mixed ion field conditions and, subsequently, to correct the absorbed dose deposited in the crystal for TL-efficiency [Berger, T., 2003. Dose assessment in mixed radiation fields-special emphasis on space dosimetry. Ph.D. Thesis, Vienna University of Technology; Berger, T., Hajek, M., Fugger, M., Vana, N., 2006a. Efficiency corrected dose verification with thermoluminescence dosemeters in heavy ion beams. Radiat. Prot. Dosim. 120, 361-364; Berger, T., Reitz, G., Hajek, M., Vana, N., 2006b. Comparison of various techniques for the exact determination of absorbed dose in heavy ion fields using passive detectors. Adv. Space Res. 37, 1716-1721.]. This approach showed good results in the low dose region (≤100 mGy). A crucial requirement for this procedure is the linearity of the gamma dose-response of the HTE for the applied dose levels. The discussion whether a linear dose-response can be found is still ongoing: while some groups reported a linear dose-response [Pradhan, A.S., Rassow, J., Meissner, P., 1985. Dosimetry of d(14)+ Be neutrons with the two-peak method of LiF TLD-700. Phys. Med. Biol. 30, 1349-1354; Massillon-Jl, G., Gamboa-deBuen, I., Brandan, M.E., 2006. Onset of supralinear response in TLD-100 exposed to 60Co gamma-rays. J. Phys. D: Appl. Phys. 39, 262-268.; Bilski, P., 2006. Response of various LiF thermoluminescent detectors to high energy ions-results of the ICCHIBAN experiment. Nucl. Instrum. Meth. Phys. Res. B 251, 121-126.] others measured a pronounced supralinearity even at very low doses [Horowitz, Y.S., Satinger, D., Puks, E., Oster, L., Podgalov, 2003. On the use of LiF:Mg, Ti TLDs in space-a critical review. Radiat. Prot. Dosim. 106, 7-25.; Horowitz, Y.S., Oster, L., Datz, H., 2007. The thermoluminescence dose-response and other characteristics of the high-temperature TL in LiF:Mg, Ti (TLD-100). Radiat. Prot. Dosim. 124, 191-205.]. This paper focuses on the results from a linearity study of the HTE in the dose region between 1 and 500 mGy.