Development of a TL detector for neutron measurement by CaSO4:Dy phosphors

Abstract

Personal neutron dosimetry is quite a difficult area because a neutron is always accompanied with gamma radiation, which is required of a capability for mixed field dosimetry. CaSO4:Dy phosphor is known to have a very high sensitivity to gamma radiation, but the neutron capture cross section of the constituents of CaSO4:Dy are so small that the interactions between the thermal neutron and the phosphor are rare. One method to improve the neutron interaction is by introducing an impurity ion with a large thermal neutron captures cross section into the phosphor to act as a neutron target centre such as 6Li. In neutron-gamma mixed radiation fields, if two detectors for the 6Li-7Li compounds embedded CaSO4:Dy thermoluminescent (TL) pellets are used, a 6Li-compound embedded pellet can detect the neutron and gamma radiations together, and the other pellet can only detect the gamma radiation. Recently, the Korea Atomic Energy Research Institute (KAERI) has developed a new type of CaSO4:Dy TL materials embedded with phosphorous (KCT-300) to detect beta and gamma radiation with a very high sensitivity. This paper presents the development of CaSO4:Dy TL pellets embedded with 6Li compound for a thermal neutron measurement, and the detection method of the neutron and gamma dose in mixed fields with CaSO4:Dy TL pellets embedded with a 6Li compound (KCT-306) and CaSO4:Dy TL pellets embedded with a 7Li compound (KCT-307) is introduced. The net neutron sensitivity of CaSO4:Dy TL pellets embedded with 6Li compound developed in this study is about two times higher than that of the TLD-600 (Harshaw Chemical) dosemeter which is available commercially.

Investigation of neutron converters for production of optically stimulated luminescence (OSL) neutron dosimeters using Al2O3:C

“…The range of the a particle and the recoil 7 Li nucleus are of the order of a few microns in Al 2 O 3 :C. On the other hand, the range of the 3 H recoil nucleus from the 6 Li(n,a) 3 H neutron capture reaction is 23 lm in Al 2 O 3 :C and 32.1 lm in LiF. Therefore, the likelihood of secondary heavy-charged particles reaching and penetrating the Al 2 O 3 :C grain, producing OSL signal, is higher for the 6 Li(n,a) 3 H than for the 10 B(n,a) 7 Li neutron capture reaction. This is probably the explanation for the successful sensitization produced by 6 Li converters, as opposed to 10 B converters.…”

“…Neutron converters are used to enhance the neutron sensitivity of active and passive detectors including TLDs and image plates [6][7][8]. They interact with the neutron field through neutron capture reaction or elastic scattering, creating secondary heavy charged particles that deposit energy in the sensitive volume, the luminescence detector in this case.…”

Thermoluminescence of silica-based materials irradiated by thermal neutrons

“…For example Yang et al [14] have suggested the use of CaSO 4 : Dy TL pellets embedded with a 6 Li compound for a thermal neutron measurement. Torkzadeh and Manouchehri [15] have measured the thermal neutron fluence in a research reactor using TLD-600.…”