PROBLEM TO BE SOLVED: To provide a method for preparing a CsX:Eu stimulable phosphor and a screen or a panel provided with the phosphor as powder phosphor or vapor deposited needle-shaped phosphor suitable for use in an image forming method for recording and reproducing images of an object made by high energy radiation. SOLUTION: The CsX:Eu stimulable phosphor is essentially free from oxygen in its crystal structure, and wherein X represents a halide selected from the group consisting of Br, Cl and combinations thereof. The method comprises the steps of mixing CsX with a compound or combinations of precursor compounds having as a composition Cs x Eu y X' x+αy , heating the mixture at a temperature ≥450°C, cooling the mixture, and optionally annealing and recovering the CsX:Eu stimulable phosphor, wherein the ratio of x/y exceeds a value of 0.25, wherein α≥2 and X' is a halide selected from the group consisting of Cl, Br and I and combinations thereof. COPYRIGHT: (C)2005,JPO&NCIPI