Investigation on radiation generated by sub-GeV electrons in ultrashort silicon and germanium bent crystals

We report on the measurements of the spectra of gamma radiation generated by 855 MeV electrons in bent silicon and germanium crystals at MAMI (MAinzer MIkrotron). The crystals were 15 $$\upmu \text {m}$$ μ m thick along the beam direction to ensure high deflection efficiency. Their (111) crystalline planes were bent by means of a piezo-actuated mechanical holder, which allowed to remotely change the crystal curvature. In such a way it was possible to investigate the radiation emitted under planar channeling and volume reflection as a function of the curvature of the crystalline planes. We showed that, using volume reflection, intense gamma radiation can be produced – with intensity comparable to that obtained in channeling but with higher angular acceptance. We studied the trade-off between radiation intensity and angular acceptance at different values of the crystal curvature. The measurements of radiation spectra have been carried out for the first time in bent germanium crystals. In particular, the intensity of radiation in the germanium crystal is higher than in the silicon one due to the higher atomic number, which is important for the development of the X-ray and gamma radiation sources based on higher-Z deformed crystals, such as crystalline undulators.

Энергетический обмен при встречном двухволновом взаимодействии в кристалле Bi-=SUB=-12-=/SUB=-GeO-=SUB=-20-=/SUB=- среза (001)

The regularities of energy transfer between two linearly polarized light waves as their contra-directional mixing on a volume reflection holographic grating formed in a photorefractive Bi12GeO20 crystal of the (001)-cut are analyzed. The values of the crystal thickness and the azimuths of the linear polarization of the light waves, at which the amplification of the object wave is achieved, are determined. The change in the direction of energy transfer to the opposite, depending on the thickness of the crystal, has been experimentally demonstrated.

Angular asymmetry of the nuclear interaction probability of high energy particles in short bent crystals

The rate of inelastic nuclear interactions in a short bent silicon crystal was precisely measured for the first time using a 180 GeV/c positive hadron beam produced in the North Experimental Area of the CERN SPS. An angular asymmetry dependence on the crystal orientation in the vicinity of the planar channeling minimum has been observed. For the inspected crystal, this probability is about $$\sim 20\%$$∼20% larger than in the amorphous case because of the atomic density increase along the particle trajectories in the angular range of volume reflection, whose dimension is determined by the crystal bending angle. Instead, for the opposite angular orientation with respect to the planar channeling, there is a smaller probability excess of $$\sim 4\%$$∼4%.

Channeling and radiation experiments at SLAC

Since 2014, a SLAC-Aarhus-Ferrara-CalPoly collaboration augmented by members of ANL and MIT has performed electron and positron channeling experiments using bent silicon crystals at the SLAC End Station A Test Beam as well as the FACET accelerator test facility. These experiments have revealed a remarkable channeling efficiency of about 24% under our conditions. Volume reflection is even more efficient with almost the whole beam taking part in the reflection process. A positron experiment demonstrated quasi-channeling oscillations for the first time at high beam energy. In our most recent experiment we measured the spectrum of gamma radiation for crystal orientations covering channeling and volume reflection. This series of experiments supports the development of more advanced crystalline devices capable e.g. of producing narrow-band gamma rays with electron beams or studying the interaction of the electrons with the wakefields generated in the crystal at high beam intensity.

OGAY IS A KIND OF RUSSIAN KOREANS: PAST AND PRESENT

In recent years, the issue of childbirth in the life of communities belonging to the same ethnic community has been given increased attention in any country. And this is not by chance. The situation in the world itself is of interest to learn more about each other, about their neighbors. This is necessary primarily to consolidate the communities themselves, to develop a unity of goals, interests in everyday life, such concepts as “he is a representative of this kind”, “he is from a kind of talented people”, “belonging to one or another kind is laudable” and so on. In other words, in practice, belonging to a clan acts as a brand, a business card in a certain situation, recognition in the society itself, in fact, representation from a particular clan. In this regard, the formation and history of the genus, the assessment of its role and place of two or one person in this society, in the gens. In Russia during the Civil War, the Great Patriotic War, in Korea during the war years 1950-1953 representatives of many Korean clans (Kim, Lee, Ogay, Choi, and others) participated. All of them glorified themselves with heroic feats, realizing the main goal – the establishment of the power of the Soviets, the achievement of victory over fascism, the liberation of the outcome of the Japanese yoke. They made a notable contribution to the consolidation of the Soviet state, actively participating in the restoration of the national economy and the revival of the culture of the peoples in the USSR. More than 500 representatives of different clans from Soviet Koreans were active participants in the process of strengthening Korean statehood in North Korea, North Korea, preserving the integrity of this state, increasing its power and spiritual potential, similar actions took place in the history of Western European countries, when representatives of different clans acted in the vanguard of the struggle to preserve the integrity of a particular statehood, its consolidation. Their efforts were focused on the development of priority sectors of the economy. Many of their undertakings were reflected in the life of the Korean family – Ogay. All the representatives of this kind mentioned in the essay, working in Kamchatka, in Primorye, in the republics of Central Asia and Kazakhstan, in certain regions of the Western European part of the RSFSR, received a volume reflection. Of course, the Korean clans underwent a transformation due to the presence of Soviet education, based on the principles of patriotism and Confucian thinking, including in conditions of rapidly developing migration processes and the functioning of civil society institutions.