Radiation sources and diagnostics with ultrashort electron bunches

Abstract

The basic principles and design of radiation sources (transition radiation, Cerenkov radiation, radiation from periodic structures, etc) and radiationbased diagnostics will be discussed, with emphasis on radiation from ultrashort electron bunches. Ultrashort electron bunches have the potential to produce high peak flux radiation sources that cover wavelength regimes where sources are currently not widely available (coherent THz/IR) as well as ultrashort X-ray pulses (3-100 fs). While radiation from the electron bunch contains the full signature of the electron beam and/or medium it has travelled through, the deconvolution of a single property of interest can be difficult due to a large number of contributing properties. The experimental implementation of novel solutions to this problem will be described for beams from 30 MeV to 30 GeV, including fluctuational interferometry, source imaging, phase matched cone angles and laser-based techniques, which utilize optical transition radiation, wiggler and Cerenkov radiation, and Thomson scattering. These novel diagnostic methods have the potential to resolve fs bunch durations, slice emittance on fs scales, etc. The advantages and novel features of these techniques will be discussed.

Experiment on the electromagnetic radiation excited in an electron beam‐ion channel system

“…[1,2] To avoid this difficulty radically, one of the possible schemes is to use the electron beam-plasma system to generate high-frequency EM radiation. [3][4][5] Although this research field can be traced back to three decades ago, the simple and feasible experimental method still needs to be studied. Specially, it attracts interests again in these years for the purpose of designing high-power THz sources.…”

“…However, as the radiation frequency increases to the terahertz (THz) band, the dimension of the cavity should be greatly reduced due to the physical restriction, which not only poses a severe challenge to the processing technology but also directly limits the capacity of power . To avoid this difficulty radically, one of the possible schemes is to use the electron beam‐plasma system to generate high‐frequency EM radiation . Although this research field can be traced back to three decades ago, the simple and feasible experimental method still needs to be studied.…”

Advances in Laser Driven Accelerator R&D

“…Some of the novel diagnostics discussed in Ref. [50] have the potential to resolve fs-bunches. Recently, the generation of coherent radiation from the electron bunches as they exit the plasma was studied experimentally [8,51] and theoretically [9], both as a radiation source and as a diagnostic for measuring the electron bunch properties [36].…”

“…A detailed overview was written of the various diagnostic techniques that we have developed, and the physics behind them [50]. Some of the novel diagnostics discussed in Ref.…”

Ultrafast Diagnostics for Electron Beams from Laser Plasma Accelerators

“…Laser Plasma Accelerators (LPAs) aie becoming increasingly important as compact sources of high-eneigy electrons As this technology begins to matme, a wide vanety of applications, from high-energy colliders to free-electron lasers [1], are emerging that would benefit greatly from it, spurring interest The primary limitations of these accelerators impeding their application in general include their lack of shot-to-shot stability and the lack of fine-tuning of the beam parameters A crucial step that precedes the ability to fine-tune and stabilize the electron beam parameters, however, is the ability to measure them As a result, a significant focus of LPA research has been dedicated to the development of diagnostic techniques [2] While the field of electron beam diagnosis in conventional accelerators is veiy mature, LPAs have several unique features that require evaluation of the suitability of the conventional techniques to this new accelerator format, as well as development of new ones One of the most notable and promising features of LPAs is their ability to produce electron bunches of extremely short durations, which are expected to be in the few femtosecond regime While such short duiations are very desirable for many applications, they can be exceptionally difficult to measure, requiring development of new methods with ultrahigh temporal resolution The susceptibility of LPAs to shot to-shot fluctuations in the beam parameters is their other salient featuie Because of this high vanability, it is generally not practical to measure the various beam parameters in series on separate shots It is thus critical to the advancement of LPA sources to develop a full suite of diagnostics which can be run simultaneously in a single-shot This requirement implies the necessity of non destructiveness in these diagnostics Here we present an overview of several diagnostics which can be used in parallel to measure charge, energy, energy spread, emittance, and longitudinal and transverse structure of the electron beams from LPAs Much advantage is taken of electromagnetic emission from the acceleiated electrons produced through various mechanisms, some of which are byproducts of the acceleration process CHARGE DIAGNOSTICS Integrating Current Transformers (ICTs) have become standard instruments for the measurement of charge in conventional accelerator because of their ease of use, precision and non invasiveness More recently, ICTs have been critical tools for the LPA community as well Because of the importance of accurate absolute charge measurement for a large number of labs (including medical institutions), many tests have been done to verify the accuracy of ICTs for electron bunches with durations typical for conventional acceletators No bunch-length dependence has yet FIGURE 1. Comparison of ICT-based and Lanex-based charge measurements.…”