Preparation of highly pure, preferably radiation-stable large volume single crystals, useful in e.g. lenses, comprises producing a melt obtained from crystal raw material and controlled cooling under solidification

摘要

Preparation of highly pure, preferably radiation-stable large volume single crystals with small intrinsic birefringence comprises producing a melt obtained from crystal raw material and controlled cooling under solidification, where: fragments and/or blends of the obtained crystals is useful as crystal raw material; the crystal exhibits no color under visual observation, and on irradiating in dark room with a white light lamp exhibits e.g. (a) minimum or maximum of perceptible reddish and/or bluish fluorescence. Preparation of highly pure, preferably radiation-stable large volume single crystals with small intrinsic birefringence comprises producing a melt obtained from crystal raw material and controlled cooling under solidification, where: fragments and/or blends of the obtained crystals are useful as crystal raw material; the crystal exhibits no color under visual observation, and on irradiating in dark room with a white light lamp exhibits (a) minimum or maximum of perceptible reddish and/or bluish fluorescence, (b) minimum or maximum of perceptible diffuse dispersion, and minimum or weak discrete dispersion of maximum two visually perceptible dispersions per dm 3>. An independent claim is included for a crystal for optical applications comprising a BSDF value of less than 7x10 -7>, RMS homogenizes after removing of 36 Zernike-coefficients of less than 15x10 -8>and a SDB RMS value in 111 direction of less than 0.2 nm/cm.