Superradiant temporal transition radiation of a relativistic electron beam
Abstract
A charge in uniform motion carries a bound field that does not radiate. Transition radiation releases part of it at a boundary in space. We propose and analyze the case of radiation emission due to a boundary in time: a relativistic electron bunch passes through an aperture in a semiconductor (silicon) wafer, and while its bound field occupies the wafer, a femtosecond laser switches the semiconductor into an electron-hole plasma. The field is a valid solution of the old medium and not of the new one, so it is handed to the plasma as an initial condition for radiation emission at the plasma frequency. Because in temporal transition radiation (t-TR) the wavevector is conserved, and the frequency is not, the emission can appear in a spectral band that the bunch's own field does not populate. Every electron contributes in phase to the initial condition at the switching moment, so the emitted energy scales as N2. We derive the field energy conversion at the temporal boundary and the resultant measurable amplitude and frequency line-shape of the radiation taking into consideration plasma carriers collisional loss. The simplified analytical model of the process and its scaling laws are confirmed by use of FDTD numerical computations for a reference case based on the parameters of an existing 6.5 MeV photoinjector accelerator. For this case we predict wideband t-TR radiation emission at THz frequencies, where the emission center frequency, near the plasma frequency, is selectable across an octave, set by the laser fluence, and the intensity is governed by the beam charge. The predicted radiative energy is detectable in a single shot. The experimental considerations for observing it are given in a Supplement.
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BibTeX
@misc{nause2026superradiant,
title = {{Superradiant temporal transition radiation of a relativistic electron beam}},
author = {Ariel Nause and Avraham Gover},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25165},
eprint = {2610.25165},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25165},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Superradiant temporal transition radiation of a relativistic electron beam
AU - Ariel Nause
AU - Avraham Gover
PY - 2026
DA - 2026/10/18
PB - arXiv
DO - 10.48550/arxiv.2610.25165
UR - https://arxiv.org/abs/2610.25165
AB - A charge in uniform motion carries a bound field that does not radiate. Transition radiation releases part of it at a boundary in space. We propose and analyze the case of radiation emission due to a boundary in time: a relativistic electron bunch passes through an aperture in a semiconductor (silicon) wafer, and while its bound field occupies the wafer, a femtosecond laser switches the semiconductor into an electron-hole plasma. The field is a valid solution of the old medium and not of the new one, so it is handed to the plasma as an initial condition for radiation emission at the plasma frequency. Because in temporal transition radiation (t-TR) the wavevector is conserved, and the frequency is not, the emission can appear in a spectral band that the bunch's own field does not populate. Every electron contributes in phase to the initial condition at the switching moment, so the emitted energy scales as N^2. We derive the field energy conversion at the temporal boundary and the resultant measurable amplitude and frequency line-shape of the radiation taking into consideration plasma carriers collisional loss. The simplified analytical model of the process and its scaling laws are confirmed by use of FDTD numerical computations for a reference case based on the parameters of an existing 6.5 MeV photoinjector accelerator. For this case we predict wideband t-TR radiation emission at THz frequencies, where the emission center frequency, near the plasma frequency, is selectable across an octave, set by the laser fluence, and the intensity is governed by the beam charge. The predicted radiative energy is detectable in a single shot. The experimental considerations for observing it are given in a Supplement.
ER -