title: Fast-neutron OSL sensitivity of thallium-doped ammonium salts.
abstract: The main problem in selecting suitable thermoluminescent (TL) materials for fast-neutron dosimetry is finding a material that is both tissue-equivalent and not damaged upon heating. Optically stimulated luminescence (OSL) avoids the need to heat the materials and allows the use of materials with a high content of hydrogen (responsible for 90% of the absorbed dose of fast-neutrons). The choice of studying the ammonium salts for their OSL properties was based on the calculation of their neutron kerma factor. A constant ratio of an ammonium salt's kerma coefficients to the tissue's kerma coefficients (in the fast-neutron range) is a prerequisite for a similar energy response to neutrons, i.e. tissue equivalency. The salts studied are NH4Br and (NH4)2SiF6 both doped with Tl+. This paper describes the OSL properties of Tl(+)-doped NH4Br and (NH4)2SiF6 after exposure to 14.5 MeV neutrons to explore their potential for developing new, tissue-equivalent OSL materials suitable for fast-neutron dosimetry. The relative neutron sensitivity, k, defined as the ratio of the sensitivity of the material to neutrons to its sensitivity to gamma rays, has been determined for 14.5 MeV neutrons and varies between k = 0.15 and k = 0.5. The latter value is a factor 2.5 higher than that found for known TL materials (k < or = 0.2). A drawback of these materials is the fast fading of the OSL signal.
authors.affiliation: Delft University of Technology, IRI, Mekelweg 15, 2629 JB Delft, The Netherlands.
authors.forename: N J M
authors.initials: NJ
authors.lastname: Le Masson
authors.forename: A J J
authors.initials: AJ
authors.lastname: Bos
authors.forename: Z
authors.initials: Z
authors.lastname: Czapla
authors.forename: J C
authors.initials: JC
authors.lastname: Brouwer
authors.forename: C W E
authors.initials: CW
authors.lastname: van Eijk
mesh_terms: D001822:Body Burden; D004781:Environmental Exposure / Q000032:analysis; D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000379:methods; D005214:Fast Neutrons; D018499:Linear Energy Transfer; D016273:Occupational Exposure / Q000032:analysis; D000644:Quaternary Ammonium Compounds / Q000528:radiation effects*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000295:instrumentation* / Q000379:methods; D011868:Radioisotopes / Q000032:analysis*; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012492:Salts / Q000528:radiation effects; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013793:Thallium / Q000528:radiation effects*; D013819:Thermoluminescent Dosimetry / Q000295:instrumentation* / Q000379:methods; D014159:Transducers
chemical_list: D000644:Quaternary Ammonium Compounds; D011868:Radioisotopes; D012492:Salts; D013793:Thallium