X-Ray image conversion and intensifying screens - using lanthanum-oxybromide or oxychloride activated by thulium

摘要

An image converter consisting of well-formed crystals of a substance of formula LnOX:Tm+3 where Ln is La and/or Gd; Z is Cl and/or Br; Tm is 0.05-1 mole% thulium used as an activator. Lanthanum or gadolinium oxychloride or oxybromide, plus Tm, are very efficient fluorescent substances for converting X-rays into visible blue light or for increasing the exposure X-ray photographic film. The optimum amt. of Tm is 0.002-0.003 mole/mole of the oxyhalide. The crystals ar pref. =2 mu in size and a suitable screen can be made using e.g. LaOBr:0.002 Tm. Tests show that such a screen has an absorption twice that exhibited by a similar screen made from CaWO4.