Yu. M. Ivanov

First results of experiments on high-efficiency single- crystal extraction of protons from the U-70 accelerator

A radical increase in the efficiency of beam extraction from an accelerator is achieved with a short (7 mm long) crystal bent by a small angle (1.7 mrad) by increasing the number of times particles pass through the crystal. A particle extraction efficiency of ~20%, in agreement with the prediction of the theory, was achieved experimentally. A record high intensity of the extracted beam 1.9×1011 protons per cycle, which is four orders of magnitude higher than previous results, is obtained.

The growth of single crystals by the self-seeding technique

Abstract A self-seeding technique suitable for growing large single crystals of low-heat-conductivity materials from the melt is developed using industrially important CdTe and Cd 1− x Zn x Te crystals as an example. A method of controlling crystal composition by maintaining an “undersaturation” excessive partial pressure of a higher-volatility component over the melt, which was developed for preparing semiconductor materials, is applied to Cd-containing compounds for the first time. With these modifications, rather perfect large CdTe and Cd 1− x Zn x Te single crystals are grown by the Obreimov–Shubnikov (gradient freeze) method.

Refinement of the atomic structure of CdTe single crystals

A comparative refinement of the anharmonic and disordered models of the atomic structure was performed based on precision X-ray diffraction data sets collected from a CdTe single crystal at 295, 376, 491, and 583 K. Although both models provide the asymmetric contributions of Cd and Te to the structure factors, the anharmonic model seems to be more advantageous.

New results on efficient crystal extraction of protons from the 70 GeV accelerator at the Institute of High-Energy Physics

A record-high particle extraction efficiency, exceeding 40%, in agreement with theoretical predictions, is achieved using a short (5 mm long) crystal bent by 1.5 mrad. An extracted beam intensity of ∼6×1011 protons per cycle is obtained. This is five to six orders of magnitude higher than previous results.

Performance of Cd0.9Zn0.1Te X-ray detectors versus the purity of initial components

X-ray detectors made of Cd0.9Zn0.1Te single crystals are studied. Starting components (Cd, Zn, Te) are obtained by multistage volume distillation. Synthesized CdZnTe is finally purified by continuous vacuum sublimation. Detectors highly sensitive to X rays are produced.

Investigation of the emission of photons induced in the volume reflection of 10-GeV positrons in a bent silicon single crystal

The emission of photons in the motion of a 10-GeV positron beam in bent silicon crystals has been experimentally investigated. The experimental data are compared with the theoretical calculations.

Preparation of CdTe and CdZnTe single-crystalline ingots 100 mm in diameter by a modified Obreimov–Shubnikov method

This survey is concerned with the development of a modified Obrerimov–Shubnikov method, namely directional solidification growth of CdTe and CdZnTe crystals.

Production of high-purity Cd, Zn, and Te by multistage vacuum distillation

The quality of detector single crystals is determined by the lifetime and mobility of nonequilibrium charge carriers, which depend on the purity of the components used for synthesis. An original setup for multistage vacuum distillation of Cd, Zn, and Te is designed, which is characterized by the simplicity of equipment and the minimal loss of the initial material. The purified materials have low contents of oxygen and metal impurities, which allow one to significantly increase the purity of the synthesized crystals.

Polymorphic transitions in CdS and CdSe as probed by dilatometry

Polymorphic transitions in CdS and CdSe were studied on a dilatometric setup that comprised an evacuated quartz ampoule containing a sample, in which a cadmium vapor pressure was created to keep the sample from subliming at high temperatures. Measurements were carried out at temperatures in the range 100–1050°C. The test samples were found to experience jumpwise changes in their lengths during heating (at 270 and 760°C in CdS and at 690 and 980°C in CdSe). Cooling induced similar changes (a jumpwise shortening of the length of a sample). Thus, a clear-cut and well reproducible hysteresis was observed in heating-cooling measurement sets. Topics of CdS and CdSe technology are discussed in terms of polymorphic transitions.

Photovoltaic X-ray detectors made of CdTe crystals with a p-n junction

X-ray detectors made of CdTe crystals with a p-n junction obtained by diffusion of In into p-CdTe are investigated. The basic characteristics of such a detector are studied for the first time. It is found that the device is highly sensitive to X rays at a low bias voltage (to −50 V) and the X-ray effective energy in the range 28–72 keV. It is shown that photovoltaic detectors based on CdTe with p-n junctions are superior to Cd0.9Zn0.1Te ones.