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Radiation generated by single and multiple volume reflection of ultrarelativistic electrons and positrons in bent crystals

Vincenzo Guidi, Laura Bandiera, and Victor Tikhomirov
Phys. Rev. A 86, 042903 – Published 22 October 2012
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  • INTRODUCTION
  • BAIER-KATKOV QUASICLASSICAL FORMULA IN…
  • SIMULATION OF THE RADIATION GENERATED BY…
  • PARTICLE MOTION AND RADIATION UNDER…
  • CONCLUSIONS
  • ACKNOWLEDGEMENTS
    • References

    Abstract

    Recently discovered processes of volume reflection and multiple volume reflection of charged particles in bent crystals are accompanied by specific electromagnetic (e.m.) radiation. The mechanism of radiation emission is quite complex due to the coexistence of different regimes for particle dynamics, resulting in e.m. generation with features characteristic of each regime. We present a simulation taking into consideration both the nondipole nature and arbitrary multiplicity of radiation accompanying volume reflection. This approach is worked out for electrons or positrons of any energy and is based on the local straight-crystal approximation and Baier-Katkov formula for radiation, the integration of which is considerably facilitated by the fast Fourier transform method. The radiation generated by multiple volume reflection with vertical and skew planes has been studied, too. A large axial contribution to the hard part of the radiative energy loss spectrum as well as the strengthening of planar radiation, with respect to the single volume reflection case, in the soft part of the spectrum are demonstrated. Both the wide spectrum and high intensity make this type of radiation quite suitable for the conversion of electron and positron beams to hard γ radiation.

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    • Received 14 June 2012
    • Corrected 26 October 2012

    DOI:https://doi.org/10.1103/PhysRevA.86.042903

    ©2012 American Physical Society

    Corrections

    26 October 2012

    Erratum

    Publisher's Note: Radiation generated by single and multiple volume reflection of ultrarelativistic electrons and positrons in bent crystals [Phys. Rev. A 86, 042903 (2012)]

    Vincenzo Guidi, Laura Bandiera, and Victor Tikhomirov
    Phys. Rev. A 86, 049906 (2012)

    Authors & Affiliations

    Vincenzo Guidi* and Laura Bandiera†

    • Department of Physics and INFN, University of Ferrara

    Victor Tikhomirov‡

    • Research Institute for Nuclear Problems, Belarus State University, Bobruiskaya 11, 220030 Minsk, Belarus

    • *guidi@fe.infn.it
    • †bandiera@fe.infn.it
    • ‡vvtikh@mail.ru

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    Issue

    Vol. 86, Iss. 4 — October 2012

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    Images

    • Figure 1
      Figure 1
      General view of particle volume reflection (left). The particle moves in the horizontal xz plane and is reflected from the vertical plane parallel to the y axis. Trajectories of 120 GeV positrons (right) reflecting from the (110) plane of the 2-mm Si crystal bent with radius of 11 m, evaluated with consideration (bottom) and in neglection (top) of the incoherent scattering. Positrons initially move at 100 μrad with respect to the reflecting bent planes.Reuse & Permissions
    • Figure 2
      Figure 2
      Effective potential (positron potential energy) of bent crystal planes. The nearest maxima reached by the effective potential in coordinates xnmx or xnmx′ are used both to determine is the particle channeled or not and to evaluate the minimal transverse velocity vmin for the unchanneled one. vmin is used both to tabulate and interpolate the intensity of radiation of the latter, while the turning point coordinate xturn is used for the same if the particle is channeled.Reuse & Permissions
    • Figure 3
      Figure 3
      Spectra of radiation of 120 GeV positrons channeled in the field of Si(110) planes with turning point coordinates 0.1, 0.3, and 0.5 Å.Reuse & Permissions
    • Figure 4
      Figure 4
      Spectra of radiation of 120 GeV positrons moving in nonchanneling regime in the field of (110) Si planes with minimal transverse velocities 10, 30 and 50 μrad.Reuse & Permissions
    • Figure 5
      Figure 5
      Energy distribution of 180 GeV positron energy losses in the 0.84 mm Si (111) crystal bent with 12 m radius. Experimental data (circles with bars) and simulation results for the FTPR (solid line) and DIBK (crosses) methods.Reuse & Permissions
    • Figure 6
      Figure 6
      Same distributions as in Fig. 5 for 180 GeV electrons and 8 m bending radius.Reuse & Permissions
    • Figure 7
      Figure 7
      Same distributions as in Fig. 5 for 120 GeV positron radiation in 2mm Si(110) crystal bent with the radius of 11 m.Reuse & Permissions
    • Figure 8
      Figure 8
      Same distributions as in Fig. 7 for 4.7 m bending radius.Reuse & Permissions
    • Figure 9
      Figure 9
      Particles hitting the crystal at small angles with respect to 〈111〉 axis, experience VR from both the vertical, (11¯0)V, and numerous skew planes. (a) The comoving reference system ryz rotates with the bent axis direction z when a particle is moving through the crystal. (b) Evolution of particle transverse velocity in the ry plane. Figure also contains the projections of the crystal planes intersecting along the 〈111〉 axis (solid) and the borders of the regions of influence by each plane (dashed). Small multiple arrows indicate the directions of particle reflection from different planes. The vertical projections of the angles of reflection from symmetric skew planes compensate each other while the horizontal ones sum up leading to the MVROC effect.Reuse & Permissions
    • Figure 10
      Figure 10
      Energy loss spectrum of 120 GeV positrons in 2 mm Si (110) crystal, bent by ϕ= 700 μrad. Plot (1) is for planar MVROC, (2) for VR by only (110)V plane and (3) for the radiation in the field of 〈111〉 axes. Positrons initially move with 50 μrad divergence and average incidence angles of 350 and 150 μrad with respect to the axis in horizontal and vertical planes.Reuse & Permissions
    • Figure 11
      Figure 11
      Same distributions as in plot 3 of Fig. 10 for both 120 GeV positron (crosses) and electron (circles) radiation in the field of 〈111〉 axes.Reuse & Permissions
    • Figure 12
      Figure 12
      Same distributions as in plot 3 of Fig. 10 for both 120 GeV electron beams with 50 μrad (line) and 150 μrad (circles) divergence.Reuse & Permissions
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