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Uri Lachish

Publications and source records attributed to Uri Lachish.

3 recordsLinked to original sources

The Sun and the Moon a Riddle in the Sky

The uniform image of the full moon is well known from the beginning of history. In the last decades, there are photos with a similar configuration of the earth observed from the moon and from space, as well as of all the planets and their moons. The photos are all nearly uniform. Such images are considered non-Lambertian since they do not comply with Lambert Cosine Law of light scattering. Theories of the uniformity deal only with the moon. Apart from being not persuasive for the moon case, they are not applicable to most other cases. There are thousands of thousands of similar photos, but there is not a single true photo that does comply with Lambert cosine Law. Photos that do comply with the law are all "rendered", that is, at least partly simulated. A calculation based on fundamental principles is presented to clarify the uniformity in all cases regardless of the observed object and its surface properties. The uniformity is a direct outcome of a single sunlight scattering from the observed object, and there is no need of further assumptions or models to justify it.

physics.pop-ph

CdTe and CdZnTe Crystal Growth and Production of Gamma Radiation Detectors

Bridgman CdTe and CdZnTe crystal growth, with cadmium vapor pressure control, is applied to production of semiconductor gamma radiation detectors. Crystals are highly donor doped and highly electrically conducting. Annealing in tellurium vapors transforms them into a highly compensated state of high electrical resistance and high sensitivity to gamma radiation. N-type detectors, equipped with ohmic contacts, and a grounded guard ring around the positive contact, are not sensitive to hole trapping. Conductivity control, by the doping level, optimizes the detector operation by trade-off between electrons' lifetime and electrical resistance. Gamma spectra of single detectors and detector arrays are presented. Detector optimization and gamma detection mechanisms are discussed.

physics.ins-det