In this report, the continuation of studies (Afonin et al., 2003, 2012; Scandale et al., 2014) of focusing properties of bent single crystals is presented. Recently, the possibility of transforming a ...parallel beam into the point-like one has been demonstrated theoretically and experimentally (Scandale et al., 2014). Here we study an inverse problem of conversion of a point-like beam into the parallel one. It is shown that, by exploiting such a capability, the significantly more intensive secondary particle beams could be generated compared to usage of other conventional method.
The results of observation and studies of focusing of 400 GeV/c proton beam with the help of bent single crystals are presented. Two silicon crystals have been used in the measurements. The focal ...length of the first and second crystals is found to be 1.48 m and 0.68 m, respectively. The mean square size of the horizontal profile in the focus was 3.1 and 4.3 times as small as at the exit of the crystals.
Works on the formation of particle and radiation beams using particle channeling and reflection in oriented crystals have been carried out at IHEP over a number of years. Comprehensive theoretical ...and experimental studies have led to the creation of actually operating systems on the U-70 accelerator. In particular, a slow proton beam extraction with unprecedentedly high parameters, an extraction efficiency of about 85% at a beam intensity of 10
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particles per cycle, has been realized on U-70 using particle channeling in short bent crystals. Experiments to implement the method of particle reflection in crystals for beam extraction and collimation have been carried out on U-70. At present, crystal elements are used in regular U-70 runs and provide half of the particle beams for physical experiments. We summarize the results of this unique experience in the world practice of accelerators and outline its prospects.
The deflection of a 1-GeV charged particle beam by a system formed by fan-oriented thin silicon wafers has been studied theoretically and experimentally. Software has been developed for numerical ...simulation of a particle beam transmission through a fan crystal system. In the U-70 experiment on a proton beam, the particles were deflected by such a system through an angle exceeding 1 mrad. Thus, a new method has been demonstrated for rotating a particle beam, which can be used for creating accelerator beams for medical purposes.
In view of the successful experience in the generation of pion and kaon secondary beams using a focusing crystal, it has been proposed to build at the U-70 accelerator a new-type channel of secondary ...particles that does not consume electric power. It has been shown experimentally that an extraction septum magnet can be protected from radiation by applying a multistrip crystal device through current septum shadowing by the crystal that involves the bulk reflection regime for the deflection of particles. The listed applications of crystals are novel in the world practice with accelerators.
Recently studies are started on the application of volume reflection of particles in crystals for the steering beams (for extraction and collimation of a circulating beam in accelerators). Volume ...reflection is more efficient than channeling, but requires amplification of the deflection angle by applying multicrystals. The report discusses two new applications of multicrystals made like multistrip structures: (i) the property of effective deflection of particle beam was used to protect the septum magnets of the U-70 in the process of extraction of the proton beam with energy of 50 GeV; (ii) the possibility of generation of gamma radiation was studied in the secondary electron beam with energy of 7 GeV. In both cases, promising preliminary data were obtained.
At large accelerators, bent crystals are employed to deflect weakly divergent proton beams at the stages of extraction and collimation. We demonstrate that a divergent particle beam may be ...efficiently deflected using a crystal with a focusing edge. A proton beam with divergence near 1 mrad, which exceeds the Lindhard angle by a factor of 30, has been experimentally deflected by 1.8 mrad with efficiency near 15%. The proposed focusing crystal may serve as an element of a novel optical system for secondary-particle beams in the TeV energy region.
A radiation source based on the emission of electrons and positrons moving in a short bent crystal has been recently discovered. The emission of particles is due to oscillations of their trajectories ...near the point of reflections, where trajectories approach a tangent to bent atomic planes. In the experiment performed with the secondary electron beam of the U70 accelerator, it has been shown that the emission intensity can be increased by using a sequence of oriented bent crystals. Passing through six 2.5-mm-long silicon crystals, 7-GeV electrons lose on average 2.0 GeV on emission. This value is several times larger than that in an amorphous medium. Thus, an intense source of radiation has been demonstrated with prospects of application at accelerators.
It has recently been realized that the focusing of high-energy particle beams at a distance of about 1 cm is promising. A new idea is proposed in this work to focus the beam at a short distance by ...using a bent plane–parallel silicon plate whose side edges are rotated at a small angle with respect to crystallographic planes. At the U-70 accelerator (IHEP, Protvino), a 50-GeV proton beam has been focused to a narrow line with a width of no more than 30 μm at a distance of 17 cm.
In the experiment the efficiency of the 50 GeV proton beam extraction from accelerator by means of a bent crystal as a function of crystal orientation was measured. This allowed one to make a ...comparative analysis of efficiencies of high-energy protons deflection by different crystal atomic planes with different values of the electrostatic field. The results of simulation of high-energy protons deflection by means of crystal atomic planes and crystal atomic strings are also presented in the article. In the case of planar channeling the simulation shows a good agreement with experimental data. In the case of proton motion in the regime of stochastic scattering by bent atomic strings the simulation shows that angles of particle deflection are much greater than the critical channeling angle.
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