Angular momentum of synchrotron radiation

Bordovitsyn, V. A.; Konstantinova, O. A.; Nemchenko, E. A.

doi:10.1007/s11182-012-9774-9

Cited by 22 publications

(18 citation statements)

References 9 publications

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“…However, at a large distance from the radiation point, it seems impossible to record the twisted photons created in this way by the detector with a short base. In accordance with (22), (55), the corresponding wave packets spread in the direction normal to the photon propagation direction with the velocity n ⊥ ∼ γ −1 .…”

Section: Helical Wigglermentioning

confidence: 53%

Probability of radiation of twisted photons by classical currents

2018

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The general formula for the probability of radiation of a twisted photon by a classical current is derived. The general theory of generation of twisted photons by undulators is developed. It is proved that the probability to record a twisted photon produced by a classical current is equal to the average number of twisted photons in a given state. The general formula for the projection of the total angular momentum of twisted photons with given the energy, the longitudinal projection of momentum, and the helicity is obtained. The symmetry property of the average number of twisted photons produced by a charged particle moving along a planar trajectory is found. The explicit formulas for the average number of twisted photons generated by undulators both in the dipole and wiggler regimes are obtained. It is established that, for the forward radiation of an ideal right-handed helical undulator, the harmonic number n of the twisted photon coincides with its projection of the total angular momentum m. As for the ideal left-handed helical undulator, we obtain that m = −n. It is found that the forward radiation of twisted photons by a planar undulator obeys the selection rule that n + m is an even number. It turns out that the average number of twisted photons produced by the undulator and detected off the undulator axis is a periodic function of m in a certain spectral band of the quantum numbers m. *

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Section: Helical Wigglermentioning

confidence: 53%

Probability of radiation of twisted photons by classical currents

2018

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“…One of the bright and sufficiently pure sources of twisted photons are undulators and undulator-like devices, for example, FELs and laser waves. The generation of narrow wave packets of twisted photons by such devices was predicted theoretically [4,5,[16][17][18][19][20][21][22][23][24][25][26] and confirmed experimentally [25,[27][28][29]. Recently, we have found a general formula for the probability of radiation of twisted photons by classical currents [30].…”

Section: Introductionmentioning

confidence: 78%

Probability of radiation of twisted photons by axially symmetric bunches of particles

Bogdanov

Kazinski

2019

Eur. Phys. J. Plus

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The effect of a finite width of a particle bunch on radiation of twisted photons is studied. The general formulas connecting the radiation probability distribution of twisted photons produced by bunches of identical particles with the radiation probability distribution of twisted photons generated by one particle are obtained for axially symmetric bunches. The bunch is called axially symmetric if it is axially symmetric with respect to the detector axis at some instant of time and all the particles in the bunch move along parallel trajectories. The general sum rules for the probability of radiation of twisted photons by axially symmetric bunches are established. In particular, we prove that the projection of the average total angular momentum of radiated twisted photons per particle in the bunch does not depend on the radial profile of the bunch. The uniform, Gaussian, and exponential radial bunch profiles are considered in detail. The radiation of axially symmetric bunches in ordinary and crystalline undulators is investigated. The selection rules for radiation of twisted photons by one particle in undulators are violated when the finite width of the particle bunch is taken into account. We find the condition when this violation is marginal. The form of the radiation probability distribution of twisted photons becomes universal for wide incoherent axially symmetric particle bunches. We completely describe these universal distributions. *

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“…For the incoherent interference factor, it is only necessary the fulfillment of (23) and the conditions on the third line of (24). The first condition on the third line of (24) follows from the first condition in (24). In the ultrarelativistic regime, the cases ζ = ±1 have to be considered separately.…”

Section: Particular Casesmentioning

confidence: 99%

Probability of radiation of twisted photons by cold relativistic particle bunches

2020

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The probability to record a twisted photon produced by a cold relativistic particle bunch of charged particles is derived. The radiation of twisted photons by such particle bunches in stationary electromagnetic fields and in propagating electromagnetic waves is investigated. Several general properties of both incoherent and coherent contributions to the radiation probability of twisted photons are established. It is shown that the incoherent radiation by bunches of particles traversing normally an isotropic dispersive medium (the edge, transition, and Vavilov-Cherenkov radiations) and by bunches moving in a helical undulator does not depend on the azimuthal distribution of particles in the bunch and is the same as for round bunches. As for planar undulators, the incoherent radiation by particle bunches is the same as for the bunches symmetric under reflection with respect to the axis of a twisted photon detector. At high energies of recorded twisted photons, this property is universal and holds for the forward incoherent radiation by any cold relativistic particle bunch. The coherent radiation of twisted photons by such particle bunches obeys the property that we call the addition rule. This rule provides a simple means to describe the properties of coherent radiation of twisted photons. Furthermore, the strong addition rule is established for the coherent radiation by sufficiently long helical bunches. The use of this rule allows one to elaborate superradiant pure sources of twisted photons. The coherent radiation by helical bunches is considered for the edge, transition, and Vavilov-Cherenkov processes and for particles moving in undulators and plane laser waves with circular polarization. In these cases, the sum rules are deduced for the total probability to record a twisted photon and for the projection of the total angular momentum per photon. The explicit expressions for both incoherent and coherent interference factors are derived for several simple bunch profiles. *

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Angular momentum of synchrotron radiation

Cited by 22 publications

References 9 publications

Probability of radiation of twisted photons by classical currents

Probability of radiation of twisted photons by classical currents

Probability of radiation of twisted photons by axially symmetric bunches of particles

Probability of radiation of twisted photons by cold relativistic particle bunches

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