Method of spatial size measurement of relativistic electrons beams with small bunch length

Abstract

We investigate the practical implementation of a previously proposed method for determining the transverse dimensions of an electron beam on a target by measuring the two-dimensional angular distributions of diffracted transition radiation of relativistic electrons for two distances between the crystal where the radiation is generated and the coordinate detector for femtosecond bunches. We show that determining electron microbunches with small longitudinal sizes requires an increased photon energy, achieved by decreasing the observation angle. The sensitivity limits of the method and the influence of the emission of secondary electrons and photons from the detector pixels are discussed. K: Beam-line instrumentation (beam position and profile monitors; beam-intensity monitors; bunch length monitors); Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc); Instrumentation for FEL 1Corresponding author.

Diffracted transition radiation as a new diagnostic tool for relativistic electron beam emittance

“…When the condition 𝜔 ≪ 𝛾𝜔 p is satisfied, the angular distribution of the intensity of the transition radiation, and hence the DTR, does not depend on the photon energy; therefore, all of the following statements apply to other crystals, observation angles, and reflecting planes. Choosing a different crystal or observation angle will only change the photon energy and reflected radiation yield [29]. The presence of the polarization factor 𝐶 pol in expression (2) leads to a change in the ratio of the intensities of the vertical and horizontal distributions with a change in the observation angle.…”

“…In all cases, the differences between the estimate and the true value start to exceed the fitting error under the condition 𝜎 ′ 𝑥,𝑦 = 𝜎 𝑥,𝑦 ∕𝑅 2 ≤ 0.1𝛾 −1 . The reason for this behavior of the fitting results is that the differences between the ''noisy'' distributions 𝑌 𝑅 1 (𝜃 𝑥 , 𝜃 𝑦 ) and 𝑌 𝑅 2 (𝜃 𝑥 , 𝜃 𝑦 ) decrease with increasing distance between the crystal and the coordinate detector [29], so the method loses its sensitivity. It is also found that with increasing ''noise'' level, the deviation of σ𝑥,𝑦 from 𝜎 𝑥,𝑦 begins to manifest itself for smaller distances, and vice versa: with decreasing ''noise'' level, the fitting error decreases, and the deviation of σ𝑥,𝑦 from 𝜎 𝑥,𝑦 starts at larger distances.…”

A proof-of-principle experiment on a new diagnostic tool for determining beam sizes from angular distributions of parametric X-ray radiation

“…In this case, DTR can be used instead of PXR, and the measurable beam size is limited by the pixel size of the detector and comparable to 10-15 μm [19]. Following the work [18,19], we discussed the scheme for determining beam sizes for XFEL linear accelerators [21], and the scheme for determining emittances of 5-10 GeV electron beams [22].…”