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Coherent radiation produced by microtron electron bunches

S. V. Anishchenko, P. V. Molchanov

TL;DR

This paper addresses the challenge of generating and measuring coherent radiation from electron-beam accelerators, focusing on coherent transition radiation (CTR) produced when a microtron beam exits into free space. It develops a formalism where the CTR spectrum is given by the product of the single-electron spectrum and the beam form factor $|F(\omega,\theta)|^2$, providing explicit expressions for the angular and spectral-angular distributions. A key result is that the spectrum forms a comb of harmonics with frequencies $\omega_n(\theta)$ and widths $\Delta\omega_n(\theta)$ that scale with angle, bunch length $\sigma$, and bunch number $N_b$. The paper also quantifies the microwave noise produced by CTR for a 10 MeV microtron beam, highlighting forward-dominated power and the importance of noise budgeting in measurements of coherent radiation.

Abstract

The theory of coherent transition radiation produced by a relativistic electron beam during its extraction from a microtron is established. Expressions for the beam form factor, spectral-angular and angular distribution of coherent transition radiation are obtained in explicit form. Estimates of microwave noise caused by coherent transition radiation are given.

Coherent radiation produced by microtron electron bunches

TL;DR

This paper addresses the challenge of generating and measuring coherent radiation from electron-beam accelerators, focusing on coherent transition radiation (CTR) produced when a microtron beam exits into free space. It develops a formalism where the CTR spectrum is given by the product of the single-electron spectrum and the beam form factor , providing explicit expressions for the angular and spectral-angular distributions. A key result is that the spectrum forms a comb of harmonics with frequencies and widths that scale with angle, bunch length , and bunch number . The paper also quantifies the microwave noise produced by CTR for a 10 MeV microtron beam, highlighting forward-dominated power and the importance of noise budgeting in measurements of coherent radiation.

Abstract

The theory of coherent transition radiation produced by a relativistic electron beam during its extraction from a microtron is established. Expressions for the beam form factor, spectral-angular and angular distribution of coherent transition radiation are obtained in explicit form. Estimates of microwave noise caused by coherent transition radiation are given.
Paper Structure (4 sections, 12 equations, 3 figures)

This paper contains 4 sections, 12 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Microtron electron bunches
  3. Transition radiation of electron bunches
  4. Conclusion

Figures (3)

  • Figure 1: Transition radiation generated by microtron electron bunches.
  • Figure 2: The angular distributions of coherent transition radiation corresponding to harmonics with indices $n=1$ (solid curves) and $n=8$ (dashed curves), respectively. Black and gray curves correspond to the condition $\omega_n(\theta)R_f\sin\theta/c\gtrsim\pi/2$ and $\omega_n(\theta) R_f\sin\theta/c\lesssim\pi/2$, respectively.
  • Figure 3: Radiation power for different harmonics. Black (gray) dots correspond to radiation emitted into the forward (backward) hemisphere in respect to the direction of particle motion.