Patent ID: 7344595

Claim:
A method for making a crystal with less absorption, less diffuse scattering and less radiation damage, in which crystal raw material is purified in a purification apparatus, said purification apparatus comprising a closable melt vessel for melting the crystal raw material and said closable melt vessel having at least one through-going opening, said method comprising the steps of: a) drying the crystal raw material by removal of absorptive, adsorptive and/or chemically bound water at a drying temperature of 100° C. to 600° C. over a drying time interval of at least 20 hours, said at least one through-going opening having a geometric conductance value of from 2.00 mm 2 to 30.00 mm 2 during the drying; b) reacting impurities contained in the crystal raw material with at least one scavenger at a reaction temperature of from 600° C. to 1200° C. for a reaction time interval of at least nine hours, said at least one through-going opening having a geometric conductance value of from 0.0020 mm 2 to 0.300 mm 2 during the reacting; and c) melting the crystal raw material to form a melted portion and homogenizing the melted portion at a homogenizing temperature above 1400° C. for a homogenizing time of at least six hours, said at least one through-going opening having a geometric conductance value of from 0.25 mm 2 to 1.1 mm 2 during the homogenizing.