Abstract: A single crystal scintillator and apparatus for prospecting underground strata using the scintillator is described. The single crystal scintillator is a cerium doped gadolinium silicate compound of the formula:Gd.sub.2-(x+y) Ln.sub.x Ce.sub.y SiO.sub.5wherein Ln is Sc, Tb, Lu, Dy, Ho, Er, Tm, or Yb; 0.03.ltoreq.x.ltoreq.1.9; and 0.001.ltoreq.y.ltoreq.0.2.

Abstract: A scintillator for radiation detection obtained by coating a light reflective material in a thickness of 50 to 150 .mu.m by a screen printing method on the surface of a solid scintillator material substrate is excellent in uniformity, dimensional accuracy with high light output. When the light reflective material layer is covered with a synthetic resin film, adhesive strength of the light reflective material layer to the substrate is increased remarkably.

Abstract: A scintillator for radiation detection obtained by coating a light reflective material in a thickness of 50 to 150 .mu.m by a screen printing method on the surface of a solid scintillator material substrate is excellent in uniformity, dimensional accuracy with high light output. When the light reflective material layer is covered with a synthetic resin film, adhesive strength of the light reflective material layer to the substrate is increased remarkably.

Abstract: A method of producing the single crystals of the gadolinium molybdate family having a high transmission and low threshold field, comprising the step of growing a single crystal from a melt of the gadolinium molybdate family by a crystal pulling technique, the step of cooling slowly the single crystal in a temperature range of from immediately below a melting point to a segregation temperature of .alpha. phase of the single crystal and the further step of cooling under such cooling conditions that the .alpha. phase is not segregated and the value of the threshold field of the single crystal is not made large in a temperature range of below the segregation temperature of the .alpha. phase.