Favorite pastime but leading nowhere

Thermoluminescence (TL) investigations enjoy a unique combination of materials scientists, TL researchers, and application dosimetrists, each supporting the other but leading to nowhere in particular. A favorite pastime in the TL community is the discovery and analysis of new TL materials. Almost invariably, the new materials are claimed to have dosimetric potential in order to establish a motivation for future research and efforts. However, since the discovery of LiF: Mg, Cu, P (GR-200) in mainland China [1], some thirty years ago, none of these materials have been demonstrated to be useful, or superior in any manner to the well-established materials: LiF: Mg, Ti, CaF₂:T_M, CaF₂:Dy. CaSO₄;Dy, Li₂B₄O₇:Mn, Al₂O₃. Even LiF: Mg, Cu, P “missed the boat” due to the requirement to carefully limit the annealing temperature to 240^oC: even a 1°C higher in temperature led to a loss in sensitivity. Dosimetry practitioners and most everybody else do not have the time or patience or know how to manage that kind of temperature control. Nowadays, the research seems to be based on “What materials do we have on the shelf today” and “trial and error”: let’s try X.Y.Z”. A recent review [2] relates the discovery of BaSO₄, CuB₄O₇, various calcium sulfate compounds, ZrO₂, MgO₂, TiO₂, and various perovskites. Other papers deal with K₂SrP₂O₇:Pr [3], an investigation of Lanthanide level location in YPO₄ doped with Ce (3+) and co-doped with Nd(3+, Sm(3+), Dy(3+), Ho(3+). Er (3+), and Tm (3+) [4]. One must mention a study of ZnO/Ag/ZnO [5]. Many other materials have been investigated, the list goes on and on. Recently, a long overdue investigation of defect clustering in BeO, undoped, doped in Cr, Mn, Ni, Ca, W, and Pb reaches the conclusion ‘that TL materials engineering is near impossible’ [6]. Unfortunately, a conclusion which is likely to be largely ignored. My advice to those currently involved is, if you must continue, look for a re-useable, tissue-equivalent material with linear dose response to at least 30 Gy. But please do not expect to publish negative results in a reputable journal.

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