Investigation of the energy spectrum and dose response of optical absorption bands in 4N single crystal LiF and LiF:Mg,Ti (TLD-100)

The optical absorption dose response of the 4.3 eV, 4.77 eV, 5.08 eV and 5.45 eV bands following gamma irradiation has been measured from 10²-10⁵ Gy in 4N single crystal LiF and compared to the dose response of the same bands in LiF:Mg,Ti (TLD-100). The relative intensity of the 4.3 eV band in the 4N material is an order of magnitude lower than in TLD-100. In addition, its dose response enters into saturation above 10⁴ Gy as opposed to the behavior of the dose response in TLD-100 which increases by over an order of magnitude between 10⁴ and 10⁶ Gy. The dose filling constant of the 4.3 eV band in 4N material can be fitted with a linear/exponentially saturating function with a value of β_4N = 2.9 × 10⁻⁴ Gy⁻¹. In TLD-100, on the other hand, the dose response requires two linear/exponentially saturating functions. The first is dominant at low dose with β₁ = 1 × 10⁻⁴ Gy⁻¹ and the second is dominant at high dose with β₂ = 1.1 × 10⁻⁵ Gy⁻¹. The value of β₂, approximately 26 times smaller than that of β_4N, suggests that the high dose behavior in TLD-100 does not result from the same “4.3 eV entity” in 4N material.