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Single- and multi-photon spectra of pulsed γ -ray beams produced at 17, 34, and 40 MeV in the laser Compton scattering were measured with an 8” × 12” NaI(Tl) detector. By using the experimental single-photon spectra as the probability function of generating random numbers, response functions of the NaI(Tl) detector to j -fold photons ( j = 2, 3, 4 ...) were constructed. The least-square fits to the experimental multi-photon spectra by the Poisson distribution consisting of the response functions were made. The multi-photon spectra measured at 17 and 34 MeV follow the Poisson distribution. A quenching phenomenon of multi-photon spectra was observed for 40 MeV γ -rays as a result of the saturation at the photomultiplier tube of the NaI(Tl) detector. The original Poisson distributions were restored from the quenched spectra using a saturation curve in the form of y = a ⋅ x η with η =e − b x . We discuss the accuracy of photon-flux determination. [ABSTRACT FROM AUTHOR]

Intense, quasi-monochromatic, polarized γ -ray beams with high and tunable energy produced by Compton scattering of laser photons against relativistic electrons are used for fundamental studies and applications. Following a series of photoneutron cross section measurements in the Giant Dipole Resonance (GDR) energy region performed at the NewSUBARU synchrotron radiation facility, we have developed the eliLaBr Monte Carlo simulation code for characterization of the scattered γ -ray photon beams. The code is implemented using Geant4 and is available on the GitHub repository (https://github.com/dan-mihai-filipescu/eliLaBr). Here we report the validation of the eliLaBr code on NewSUBARU LCS γ -ray beam flux and spectral distribution data and two applications performed with it for asymmetric transverse emittance profiles electron beams, characteristic for synchrotrons. The first application is based on a systematic investigation of transverse collimator offsets relative to the laser and electron beam axis. We show that the maximum energy of the LCS γ -ray beam is altered by vertical collimator offsets, where the edge shifts towards lower energies with the increase in the offset. Secondly, using the eliLaBr code, we investigate the effect of the laser polarization plane orientation on the properties of the LCS γ -ray beams produced with asymmetric emittance electron beams. We show that: 1. The use of vertically polarized lasers contributes to the preservation of the LCS γ -ray beam maximum energy edge by increasing the precision in the vertical collimator alignment. 2. Under identical conditions for the electron and laser beams phase-space distributions, the energy spectrum of the scattered LCS γ -ray beam changes with the laser beam polarization plane orientation. More precisely, the use of vertically polarized laser beams slightly deteriorates the LCS γ -ray beam energy resolution. [ABSTRACT FROM AUTHOR]

The ELI-NP Gamma Beam Source (GBS) is now under construction in Magurele–Bucharest (RO). Here an advanced source of gamma photons with unprecedented specifications of brilliance ( > 10 21 ), monochromaticity (0.5%) and energy tunability (0.2–19.5 MeV) is being built, based on Inverse Compton Scattering in the head-on configuration between an electron beam of maximum energy 750 MeV and a high quality high power ps laser beam. These requirements make the ELI-NP GBS an advanced and challenging gamma ray source. The electron beam dynamics analysis and control regarding the machine sensitivity to the possible jitter and misalignments are presented. The effects on the beam quality are illustrated providing the basis for the alignment procedure and jitter tolerances. [ABSTRACT FROM AUTHOR]

Abstract: The rf photoinjector and linear accelerator in the Mono-Energetic Gamma-ray (MEGa-ray) facility at LLNL is presented. This machine uses 11.4GHz rf technology to accelerate a high-brightness electron beam up to 250MeV to produce MeV through Compton scattering with a Joule-class laser pulse. Compton scattering-based generation of high flux, narrow bandwidth places stringent requirements on the performance of the accelerator. The component parts of the accelerator are presented and their requirements described. Simulations of expected electron beam parameters and the resulting light source properties are presented. [Copyright &y& Elsevier]

Abstract: A gamma-ray beam produced by Compton scattering of a laser beam with a relativistic electron beam has been used for nuclear physics research at the high intensity -ray source () facility at Duke University. The success of many experiments using the gamma-ray beam critically depends on the accurate knowledge of the gamma-ray beam energy distribution which is typically obtained by unfolding a measured energy spectrum. Conventionally, the detector response function used in the spectrum unfolding is simulated by a simple Monte Carlo code in which an isotropic gamma-ray event generator is used. However, for a Compton scattered gamma-ray beam, this simulation method could lead to an inaccurate detector response function, since it neglects the spatial and energy distributions of the gamma-ray beam. In this paper, we will present a novel end-to-end gamma-ray spectrum reconstruction method by completely modeling the process of the Compton gamma-ray beam production, collimation, transportation and detection. Using this method, we have successfully reconstructed the energy distribution of beams for nuclear physics research with a high degree of accuracy. [Copyright &y& Elsevier]

Abstract: A two-dimensional laser-wire scanner capable of measuring the transverse charge profiles of an electron (or positron) bunch has been constructed at the PETRA accelerator in DESY. The development of the system is explained in this paper, along with descriptions of its photon detector and laser system. Results of transverse profile scans are presented for both horizontal and vertical directions. The measurement error is 1.3% from a multi-scan measurement in the vertical direction, where single scans can be performed in less than 50s. [Copyright &y& Elsevier]

Abstract: We present a feasibility study of a particular X-ray source based on Compton scattering. In particular, we focus on the pulse mode of its operation, in which electron beams are injected with the frequency of 50–60Hz. We propose to construct a compact storage ring with a circumference of 12m, as well as a lattice to provide stable operation in the pulse mode for electron–laser interaction. We develop a computer code to simulate beam dynamics in the pulse mode. Intra-beam scattering and Compton scattering are included in the simulation, and their effects on beam emittance and stability are discussed. This source provides X-ray beam in the pulse mode with an intensity of ∼1.7×1012 photons/s and spectral brightness of ∼1010 photons/s/0.1%BW/mm2/mrad2 in the energy range from 20 to 80keV. These parameters meet the requirements for angiography as well as other technological and scientific applications that require high brightness and pulse nature of X-ray. [Copyright &y& Elsevier]

Abstract: The laser undulator compact X-ray source (LUCX) is a test bench used with the compact, high-brightness X-ray generator at KEK (High Energy Accelerator Research Organization). Our group is conducting experiments with LUCX to demonstrate the possibility of K-edge digital subtraction angiography, based on Compton scattering. One of the challenging problems is to generate high-brightness multi-bunch electron beams to compensate for the energy difference arising from the beam loading effect. In this paper we calculate the transient beam loading voltage and energy gain from the RF field in the gun and accelerating tube for a multi-bunch train. To do so we consider the process by which the RF field builds up in the gun and accelerating tube, and the special shape of the RF pulse. We generate and accelerate 100 bunches with a 50nC electron bunch train, effectively compensating for the beam loading effect by adjusting the injection timing. Using a beam position monitor (BPM) and optical transition radiation (OTR) system, we measure the electron beam energy bunch by bunch. The average energy of a 100-bunch train is 40.5MeV and the maximum energy difference from bunch to bunch is 0.26MeV. [Copyright &y& Elsevier]

Abstract: Quasi-monochromatic X-rays can be generated via Compton backscattering at the KAERI superconducting (SC) radio-frequency (RF) Linac system. The KAERI SC RF Linac with one 352MHz cryomodule is now operating at 10MeV. For a few keV Compton X-rays, an electron beamline is designed at the straight section, just after the SC linac, while an optical beamline is designed and fabricated based on the fiber laser delivery. Both will be installed in fall, 2006. In this paper, we estimate the parameters of Compton X-rays at a given system using three different commercial lasers and suggest the scheme to generate higher harmonics using an intense ultra-short laser. [Copyright &y& Elsevier]

Abstract: The new generation of the intense X-ray sources based on low-energy electron storage ring and Compton scattering (CS) of laser beam allows to produce X-rays with intensity up to 1014 phot/s. There are two basic problems in laser–electron storage rings (LESR) design. The first one is associated with strong effect of the intrabeam scattering at low electron beam energy. Because of this effect, the beam size grows quickly and CS intensity decreases. The second problem is associated with large electron beam energy spread because of fluctuation of Compton generation. The value of the energy spread may run up to few percents and one has to keep electron beam during long term in order to achieve the high Compton beam intensity. The paper is devoted to the description of lattice of NSC KIPT compact intense X-ray generator NESTOR and the main principles are background for the LESR lattice design. [Copyright &y& Elsevier]

Abstract: We describe in this report an upgraded version of the laser wire beam profile monitor developed at KEK to measure a low-emittance electron beam in the ATF damping ring. This monitor is based on the Compton scattering of electrons with a laser light target. A thin and intense laser beam is produced by exciting a Fabry–Perot optical cavity with a CW laser. Various improvements were made to the original setup. First, the effective laser power inside the cavity was increased by an order of magnitude, leading to a drastic increase in a signal-to-background ratio and a decrease in measurement time. Second, readout circuits were modified to separately measure beam sizes of each bunch in a multi-bunch beam. Third, two cavities were installed to measure both horizontal and vertical beam sizes. With this upgraded setup, measurements of electron beam emittance operated in a multi-bunch mode were carried out successfully. [Copyright &y& Elsevier]

A tightly focused laser beam (laser wire) is used for measurement of transverse electron beam sizes in storage rings and linear colliders. It is assumed that the laser beam does nothing with the electron beam except Compton scatterings which happen with a rather small probability. In reality, electrons crossing the laser beam get kicks (with 100% probability) proportional to the square of the laser field and inversely proportional to the beam energy. In practical cases of beam diagnostics this effect is negligible. [Copyright &y& Elsevier]

We propose a design of a polarized positron source for linear colliders. The design is based on electron–positron pair creation from polarized γ-rays which are produced by Compton scattering of circularly polarized laser light off a high-energy electron beam. Polarized positrons are created from those γ-rays incident on a thin conversion target. A future linear collider of the TeV-energy region requires an extraordinary large number of positrons (∼1×1010 positrons/bunch) in a multi-bunch time structure. To meet these requirements, our design employs a high-current, low-emittance electron beam of 5.8 GeV, 10 CO2 lasers, and 200 laser–electron collision-points. At each collision point, a pair of specially designed parabolic mirrors is installed to achieve efficient head-on collisions. This system allows us to produce high-intensity polarized γ-rays, which effectively generate high-intensity polarized positrons with the magnitude of polarization greater than 50%. [Copyright &y& Elsevier]

Compton scattered radiation sources have been utilized in a broad range of experiments from fundamental science to industrial applications for their unique features, the generation of energy-tunable, nearly mono-energetic polarized photon beams. In the Compton radiation sources, the radiation bandwidth can be controlled by a collimator to restrict the scattering angle, but the bandwidth is also affected by the emittance and energy spread of the electron beam. In this study, we discuss collimator optimization to obtain narrow-band radiation from a Compton source with an electron beam having asymmetric emittance in the horizontal and vertical planes. A Monte Carlo simulation code based on Geant4 has been developed and used to compare circular and rectangular collimators for shaping the radiation spectrum of Compton sources. [ABSTRACT FROM AUTHOR]

The fineness of a composite open resonator for a compact X-ray source is calculated. The region of the resonator parameters has been found where its fineness is unessentially changed, the excited mode remains Gaussian (with maximum at the axis of the laser beam) and the effective head-on collision of laser and electron beams is realized. [Copyright &y& Elsevier]

Abstract: Spectral and angular information of inverse Compton sources is shown to be obtainable using only an X-ray imaging device and various foils with K-edges in keV energy range. Beam parameters can be chosen such that on-axis photons are above the K-edge for a given material, where absorption is very strong and there is relatively zero transmission. Photons observed off-axis are red-shifted and fall below the K-edge, therefore being transmitted and creating a “ring” pattern in the ideal case. Starting with photon energies below the K-edge and aperturing for small angles on-axis allows one to scan the electron beam to higher energy until all scattered photons are above the K-edge and absorbed, thus presenting a method of bandwidth measurement. Using these methods, we present experimental results of the bandwidth and double differential spectrum (DDS) for angle and energy of Compton photons generated at the Brookhaven National Laboratory Accelerator Test Facility (BNL ATF). [Copyright &y& Elsevier]