Radiation emission and its influence on the motion of multi-GeV electrons and positrons incident on a single diamond crystal

Kirsebom, K.; Mikkelsen, U.; Uggerhøj, E.; Elsener, K.; Ballestrero, S.; Sona, P.; Connell, S. H.; Sellschop, J.P.F.; Vilakazi, Z.

doi:10.1016/s0168-583x(00)00517-6

Cited by 28 publications

(17 citation statements)

References 33 publications

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“…Investigations of the onset of QED effects in energy loss have been performed before by others [19,20] for a Ge crystal aligned on the axis and by us for a diamond crystal [21]. However, the influence of the spin was marginal for the values of x achieved; the large energy losses dominated by channeling and thus the spin were not discussed.…”

Section: -1mentioning

confidence: 99%

First Measurements of the Unique Influence of Spin on the Energy Loss of Ultrarelativistic Electrons in Strong Electromagnetic Fields

et al. 2001

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Although some authors have claimed that the effect is not detectable, we show experimentally for the first time that as the quantum parameter x grows beyond 1, an increasingly large part of the hard radiation emitted arises from the spin of the electron. Results for the energy loss of electrons in the energy range 35-243 GeV incident on a W single crystal are presented. Close to the axial direction the strong electromagnetic fields induce a radiative energy loss which is significantly enhanced compared to incidence on an amorphous target. In such continuously strong fields, the radiation process is highly nonperturbative for ultrarelativistic particles and a full quantum description is needed. The remarkable effect of spin flips and the energy loss is connected to the presence of a field comparable in magnitude to the Schwinger critical field, E 0 m 2 c 3 ͞eh, in the rest frame of the emitting electron. DOI: 10.1103/PhysRevLett.87.054801 PACS numbers: 41.60. -m, 12.20. -m, 41.75.Ht, 78.70. -g Under small angles of incidence to a crystal, the strong electric fields of the nuclear constituents add coherently such as to obtain a macroscopic, continuous field of the order E Ӎ 10 11 V͞cm. This is evidenced by, e.g., the channeling phenomenon [1] or the so-called "doughnut scattering" [2]. Therefore, in the rest frame of an ultrarelativistic electron with a Lorentz factor of g Ӎ 10 5 , the field encountered becomes comparable to the critical (or Schwinger-) field, E 0 m 2 c 3 ͞eh 1.32 3 10 16 V͞cm, corresponding to a magnetic field B 0 4.41 3 10 9 T. Here, m is the rest mass of the electron, c is the speed of light, e is the elementary charge, andh is Planck's constant divided by 2p. The incident particle moves in these immensely strong fields over distances up to that of the crystal thickness, i.e., up to several mm. Thereby the behavior of charged particles in strong fields as E 0 can be investigated.Strong field effects can be investigated by other means. One example is in heavy ion collisions where the field becomes comparable to the Schwinger field, but the collision is of extremely short duration. Another -technically demanding -example is in multi-GeV electron collisions with terawatt laser pulses where nonlinear Compton scattering and so-called "Breit-Wheeler" pair production are observed [3]. In nature, near-critical fields are believed to be present in the vicinity of pulsars.However, as we point out below, in order to investigate the effect of the spin on the radiation spectrum, the electron must interact with the strong field over large distances. So crystals present unique tools for the investigation of the influence of spin on the radiation spectrum.Already in the late 1960s, Baier and Katkov [4] calculated the photon spectrum emitted by "particles of arbitrary spin moving in an arbitrary electromagnetic field." However, the realization that the spin influences the spectrum significantly in this context lay dormant for many years and was not discussed as an observable phenomenon although radiation in...

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Section: -1mentioning

confidence: 99%

First Measurements of the Unique Influence of Spin on the Energy Loss of Ultrarelativistic Electrons in Strong Electromagnetic Fields

et al. 2001

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“…In the production of photon beams, single crystals can play an important role by exploiting coherent and strong field effects that arise for oriented incidence in the interaction of radiation and matter in crystalline materials [16]. The CB method is a well established technique for obtaining linearly polarized photons starting from unpolarized electrons [17][18][19][20].…”

Section: A Linearly Polarized Cb Photonsmentioning

confidence: 99%

Coherent bremsstrahlung, coherent pair production, birefringence, and polarimetry in the 20–170 GeV energy range using aligned crystals

Apyan¹,

Avakian²,

Badełek³

et al. 2008

Phys. Rev. ST Accel. Beams

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The processes of coherent bremsstrahlung (CB) and coherent pair production (CPP) based on aligned crystal targets have been studied in the energy range 20 -170 GeV. The experimental arrangement allowed for measurements of single photon properties of these phenomena including their polarization dependences. This is significant as the theoretical description of CB and CPP is an area of active debate and development. With the approach used in this paper, both the measured cross sections and polarization observables are predicted very well. This indicates a proper understanding of CB and CPP up to energies of 170 GeV. Birefringence in CPP on aligned crystals is applied to determine the polarization parameters in our measurements. New technologies for high-energy photon beam optics including phase plates and polarimeters for linear and circular polarization are demonstrated in this experiment. Coherent bremsstrahlung for the strings-on-strings (SOS) orientation yields a larger enhancement for hard photons than CB for the channeling orientations of the crystal. Our measurements and our calculations indicate low photon polarizations for the high-energy SOS photons.

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“…Recently these experiments were resumed in CERN 23 for electron energies up to 243 GeV. All these experimental and theoretical investigations were devoted to the analysis of the multiple scattering effect on radiation spectrum.…”

Section: Introductionmentioning

confidence: 99%

<title>Multiple scattering effect on angular distribution and polarization of radiation by relativistic electrons in a thin crystal</title>

Fomin¹,

Fomin

Шульга

2005

SPIE Proceedings

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The multiple scattering of ultra relativistic electrons in an amorphous matter leads to the suppression of the soft part of radiation spectrum (the Landau-Pomeranchuk-Migdal effect), and also can change essentially the angular distribution of the emitted photons. A similar effect must take place in a crystal for the coherent radiation of relativistic electron. The results of the theoretical investigation of angular distributions and polarization of radiation by a relativistic electron passing through a thin (in comparison with a coherence length) crystal at a small angle to the crystal axis are presented. The electron trajectories in crystal were simulated using the binary collision model which takes into account both coherent and incoherent effects at scattering. The angular distribution of radiation and polarization were calculated as a sum of radiation from each electron. It is shown that there are nontrivial angular distributions of the emitted photons and their polarization that are connected to the superposition of the coherent scattering of electrons by atomic rows ("doughnut scattering" effect) and the suppression of radiation (similar to the Landau-Pomeranchuk-Migdal effect in an amorphous matter). It is also shown that circular polarization of radiation in the considered case is identically zero.

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Radiation emission and its influence on the motion of multi-GeV electrons and positrons incident on a single diamond crystal

Cited by 28 publications

References 33 publications

First Measurements of the Unique Influence of Spin on the Energy Loss of Ultrarelativistic Electrons in Strong Electromagnetic Fields

First Measurements of the Unique Influence of Spin on the Energy Loss of Ultrarelativistic Electrons in Strong Electromagnetic Fields

Coherent bremsstrahlung, coherent pair production, birefringence, and polarimetry in the 20–170 GeV energy range using aligned crystals

<title>Multiple scattering effect on angular distribution and polarization of radiation by relativistic electrons in a thin crystal</title>

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