Thomson scattering infrared photons off energetic electrons provides a mechanism to produce hard X-rays desirable for applied sciences research Using a small, modest energy (25MeV) electron storage ring together with a resonantly-driven optical storage cavity, a narrow spectrum of hard X-rays could be produced with the quality and monochromatic intensity approaching that of beamline sources at large synchrotron radiation laboratories The general design of this X-ray source as well as its technical feasibility are presented In particular, the requirements of optical pulse gain enhancement in an external cavity are described and experimentally demonstrated using a CW mode-locked laser

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A compact light source: Design and technical feasibility study of a laser-electron storage ring X-ray source

Based on single particle tracking in the framework of classical Thomson scattering with incoherent superposition, we developed a relativistic, three-dimensional numerical model that calculates and quantifies the characteristics of emitted radiation when a relativistic electron beam interacts with an intense laser pulse. This model has been benchmarked against analytical expressions, based on the plane wave approximation to the laser field, derived by Esarey et al. [Phys. Rev. E 48, 3003 (1993)]. For laser pulses of sufficient duration, we find that the scattered radiation spectrum is broadened due to interferences arising from the pulsed nature of the laser. We find that by appropriately chirping the scattering laser pulse, spectral broadening can be minimized, and the peak on-axis brightness of the emitted radiation is increased by a factor of approximately 5.

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Spectral bandwidth reduction of Thomson scattered light by pulse chirping

The process of Thomson scattering of an ultra-intense laser pulse by a relativistic electron bunch has been proposed as a way to obtain a bright source of short, tunable and quasi-monochromatic X-ray pulses. The real applicability of such a method depends crucially on the electron-beam quality, the angular and energetic distributions playing a relevant role. In this paper we present the computation of the Thomson-scattered radiation generated by a plane-wave, linearly polarized and flat-top laser pulse, incident on a counterpropagating electron bunch having a sizable angular divergence and a generic energy distribution. Both linear and nonlinear Thomson-scattering regimes are considered and the impact of the rising front of the pulse on the scattered-radiation distribution has been taken into account. Simplified relations valid for long laser pulses and small values of both scattering angle and bunch divergence are also reported. Finally, we apply the results to the cases of backscattering with electron bunches typically produced with both standard radio-frequency-based accelerators and laser–plasma accelerators.

Thomson backscattering X-rays from ultra-relativistic electron bunches and temporally shaped laser pulses

The beam energy measurement system (BEMS) for the upgraded Beijing electron–positron collider BEPC-II is described. The system is based on measuring the energies of Compton back-scattered photons. The relative systematic uncertainty of the electron and positron beam energy determination is estimated as 2×10−5. The relative uncertainty of the beam's energy spread is about 6%.

The Beam energy measurement system for the Beijing electron-positron collider

We examine a Lagrangian formulation of gravity based on an approach analogous to electromagnetism, called Gravitoelectromagnetism (GEM). The gravitational analogue of the electromagnetic field tensor is a three-index tensor, $${\mathcal {F}_{\mu\nu\lambda}}$$
 , defined in terms of a two-index gravitoelectromagnetic potential, $${\mathcal {A}_{\mu\nu}}$$
 . The energy-momentum tensor is derived and is symmetric. We construct a Lagrangian which allows us to describe interactions between fermions, photons and gravitons. We calculate transition amplitudes of various processes involving gravitons: gravitational Moller scattering, gravitational Compton scattering, and the graviton photoproduction.

On a Lagrangian formulation of gravitoelectromagnetism

Laser Compton scattering by relativistic electrons provides the energy information associated with electron beams in an accelerator. Determining the electron beam energy by this method depends primarily on the signal to noise (S/N) ratio associated with laser Compton scattering. In this study, we propose a method to enhance the S/N ratio by synchronous measurement with a high peak power pulsed ${\mathrm{CO}}_{2}$ laser. In this method, the pulsed ${\mathrm{CO}}_{2}$ laser provides the gate trigger signals, and the delay times of the triggers are optimized to obtain a maximum S/N ratio. In the storage ring of Taiwan Light Source, a \ensuremath{\gamma} ray with the highest energy of 3.021 MeV was backscattered after the 0.1172 eV ${\mathrm{CO}}_{2}$ laser photons colliding with the relativistic electrons. The S/N ratio is about 42.5 with the electron beam current being 19 mA. Also, the measured electron beam energy is 1.3058 GeV with relative uncertainty 0.13%. \textcopyright{} 1996 The American Physical Society.

https://epaper.kek.jp/e96/papers/tupl/tup071l.pdf

Energy measurement of relativistic electron beams by laser compton scattering

In the experimental study of accelerator physics, a turn by turn monitoring of the beam profile CAN provide very unique information. In this paper, we proposed a method which may measure a turn by turn electron beam profile through its synchrotron radiation by using a fast photo-diode. Here, we utilized the non-linearity of the response of the photo-diode detector. At high photon intensity, non-linearity occurred due to the saturation of the device. In this paper, we will present the theory and the test experimental results. We had examined this idea by using a modulated He-Ne laser to simulate the synchrotron radiation light. The results agree with our computer simulation results. But the photon power intensity of synchrotron radiation in the storage ring of TLS (Taiwan Light Source) is not sufficient to saturate the photo-diode as what we expected. In order to utilize the idea on the synchrotron radiation, we used an external light source to saturate the photo-diode and the synchrotron radiation be the probe beam. In this paper, the theory and the experiment of the above idea will be discussed.

http://ieeexplore.ieee.org/iel3/3749/10951/00505602.pdf

Ian C. Hsu

Papers

Energy measurement of relativistic electron beams by laser compton scattering

Study of fast energy electron beam profile monitor system