Mikhail N. Strikhanov

Diffraction radiation from relativistic particles

Foreword Preface 1. Radiation from Relativistic Particles 2. General Properties of Diffraction Radiation 3. Diffraction Radiation at Optical and Lower Frequencies 4. Diffraction Radiation in the Ultraviolet and Soft X-Ray Regions 5. Diffraction Radiation at the Resonant Frequency 6. Diffraction Radiation from Media with Periodic Surfaces 7. Coherent Radiation Generated by Bunches of Charged Particles 8. Diffraction Radiation in the Pre-Wave (FRESNEL) Zone 9. Experimental Investigations of Diffraction Radiation Generated by Relativistic Electrons References

First experimental observation of the conical effect in Smith–Purcell radiation

The conical effect in Smith–Purcell radiation arising from electrons moving at non-zero angle to the direction of grating periodicity has been observed for the first time. It was found that the maximum of radiation intensity for ψ ≠ 0 shifts in both polar and azimuth angles. The experimental and theoretical results were compared, and the good agreement was shown. The experiment has been performed for 6 MeV electrons and at millimeter wavelengths.

Theoretical analysis of the strain mapping in a single core-shell nanowire by x-ray Bragg ptychography

X-ray Bragg ptychography (XBP) is an experimental technique for high-resolution strain mapping in a single nano- and mesoscopic crystalline structures. In this work we discuss the conditions that allow direct interpretation of the ptychographic reconstructions in terms of the strain distribution obtained from the two dimensional (2D) XBP. Simulations of the 2D XBP experiments under realistic experimental conditions are performed with a model of InGaN/GaN core-shell nanowire with low (1%) and high (30%) Indium concentrations in the shell.

Coherent effects in backward EUV and x-ray transition radiation of a bunch of electrons from thin wires

In this paper we consider X-Ray and EUV Transition radiation propagating in backward direction which is generated by the ultrarelativistic electron bunch crossing the target. The target consists of periodical set of thin wires with the rectangular cross-section. We obtain the analytical expressions for distribution of the energy of the transition radiation per solid angle and frequency. In high frequency region (X-Ray, EUV), where the wavelength of radiation is less than length of a beam, the main part of radiation is incoherent. In this case the radiation from electron bunches is described by the so called incoherent form-factor. We obtain and analyse the expression for incoherent form-factor. In this work we show that incoherent form-factor arises always when the size of a target is finite and that it depends on the ratio between the transversal size of the bunch and the production of wavelength and Lorentz-factor of the charged particles. The coherent effects of target and the electron bunch play an important role in increasing the intensity of radiation and also change the spatial distribution of radiation.

XUV Cherenkov and diffraction radiation from femtosecond electron bunch

Absorption in the medium, i.e. an imaginary part of the dielectric permittivity, can lead to arising of Cherenkov radiation at high frequencies – X-Ray and XUV. In this paper X-Ray Diffraction radiation from a bunch of ultra-relativistic electrons moving near an absorbing target is investigated theoretically. In these conditions the Cherenkov radiation arises even when trajectories of the particles does not cross the target. The spatial distribution of the radiation usually represents the cone with the axis in forward direction with thickness proportional to the imaginary part of dielectric permittivity. In this paper it is shown that taking into account the refraction and reflection of the waves at the surface of the target leads to essential changes in spatial distribution of radiation. We give analytical description of the XUV Cherenkov and diffraction radiation from the bunch of charged particles. We show that the spatial distribution of radiation is not symmetrical in relation to the top face of the target.

THz radiation under non-central propagation of electrons through periodical channel

Radiation from non-central electrons moving through channel with variable radius in the THz region is investigated using Particle In Cell (PIC) solver of the Computer Simulation Technology (CST) software package. Characteristics of radiation arising for non-central and central electrons propagation in the channel are compared, both for Smith-Purcell and Cherenkov kinds of radiation. It is demonstrated that the radiation is more intensive for the non-central propagation of electrons.

Inclusive Hadron Production

The initial stage of the investigation of single-spin asymmetry in inclusive hadron production was performed in the 1960s with the appearance of polarized proton beams with a kinetic energy of 400 MeV (March in Phys. Rev. 120:1874, 1960; Mcllwan et al. in Phys. Rev. 127:239, 1962) and 650 MeV (Borisov et al. in Sov. J. Nucl. Phys. 5:348, 1967). The first and second experiments were carried out with emulsions and bubble chambers, respectively; the third experiment was a purely electronic experiment (scintillation counters) with high statistics. In all these experiments, nonzero asymmetry of pions was observed. To interpret asymmetry in inclusive pion production at 650 MeV, the known Mandelstam isobar model (Mandelstam in Proc. R. Soc. A 244:491, 1958) was successfully used, whereas the one-pion exchange (OPE) model (Ferrari and Selleri in Nuovo Cimento 27:1450, 1963) appeared to be unsatisfactory (Nurushev and Solovyanov in Preprint No. R-2382, JINR, Dubna, Russia, 1965). These data were also useful for the phase shift analysis. Physicists made huge efforts to advance polarization investigations from energies about 100 MeV to energies ∼105 GeV (in the laboratory frame) for 50 years. At the same time, the prevailing opinion is still that the spin phenomena insignificant and can disappear with increasing energy. However, already the first results from the RHIC collider showed that polarization effects survive even at energies of 105 GeV. Now, it is possible to hope that polarization physics will bring many further surprising results. Single-spin asymmetries at high energies (>10 GeV) have been considered in several works where one can find particular results and details of discussions (Soffer in Proceedings of the workshop on the prospects of spin physics at HERA, Zeuthen, p. 370, 1995; Nurushev in Proceedings of the 2nd meeting held at Zeuthen, p. 3, 1995; Nurushev in Proceedings of the 2nd meeting held at Zeuthen, p. 75, 1995).

Results of the Experiments with Fixed Targets

The comparative investigation of polarization phenomena in the interaction of particles and antiparticles is an important but insufficiently developed research direction. The known Pomeranchuk hypothesis states that total interaction cross sections of particles and antiparticles should be equal in the asymptotic limit in the case of unpolarized hadrons (Pomeranchuk in Zh. Eksp. Teor. Fiz. 34:725, 1958). This hypothesis is experimentally tested up to a center-of-mass energy of 63 GeV at ISR. The asymptotic limit in the sense of this hypothesis has not yet been reached. There is no any experimental test of this hypothesis for the case of the interaction of polarized particles and antiparticles. In Sect. 3.2, we mentioned the hypothesis proposed in Logunov et al. (Dokl. Akad. Nauk SSSR 142:317, 1962), and Nambu and Iona-Lasinio (Phys. Rev. 122:345, 1961) of the γ 5 invariance of strong interaction in the asymptotic limit. Certain asymptotic relations between the polarization parameters in cross reaction channels are predicted in a number of theoretical works (see Sect. 3.3). Unfortunately, they have not yet been experimentally tested. There is only one experimental work on studying the polarization of particles and antiparticles in elastic scattering. It will be described below (Nurushev In: Proceedings of the 9th international symposium on high energy spin physics, Bonn, Germany, p. 34, 1990).

Latest Results from the Largest Polarization Setups

The above presentation was based on review of Nurushev (Int. J. Mod. Phys. A 12:3433, 1997) appearing ten years ago. Since that, large polarization setups COMPASS (CERN) and HERMES (DESY), as well as the STAR, PHENIX, BRAHMS, and pp2pp setups at RHIC (BNL), have been commissioned. The first results from them have appeared partially in the final form, partially in the form of preliminary reports inaccessible to a wide audience. We present some interesting results to readers.

Methods for Obtaining Polarized Beams

Methods for obtaining high-energy polarized beams are strongly different for different particles. The problem of obtaining polarized proton beams is most complicated. In this case, it is necessary to create high-current sources of hydrogen ions with a high polarization degree and to guide such a beam through a long chain of accelerating units for reaching the final energy. It is particularly difficult to guide beams through strong-focusing accelerators, where a high-accuracy device, so-called “Siberian snake,” should be used to preserve polarization during the acceleration of the protons. This device will be described later. The polarimetry of high-energy proton beams is also difficult. The problem of obtaining polarized electron beams in circular accelerator is somewhat easier. This problem is simplified with the use of ring accelerators/colliders due to the effect of the synchrotron-radiation-induced self-polarization of electrons (so-called Sokolov–Ternov (ST) effect), which will be discussed in the section devoted to polarized electron/positron beams. The problem of obtaining polarized electron beams in linear accelerators is somewhat more complicated. In this case, it is necessary to create high-current sources of polarized electrons. It is particularly easy to obtain polarized muon beams. Muons appear being already polarized in the weak decay of pions. For this reason, many difficulties inherent in the production of polarized proton and even electron (linac) beams are absent in this case. These aspects will be discussed in more details later.