Some Theoretical Estimations of Spatial Distribution of Compton Backscattered Laser Photons Beam

Non-planar four-mirror optical cavity for high intensity gamma ray flux production by pulsed laser beam Compton scattering off GeV-electrons

As part of the R&D toward the production of high flux of polarised Gamma-rays we have designed and built a non-planar four-mirror optical cavity with a high finesse and operated it at a particle accelerator. We report on the main challenges of such cavity, such as the design of a suitable laser based on fiber technology, the mechanical difficulties of having a high tunability and a high mechanical stability in an accelerator environment and the active stabilization of such cavity by implementing a double feedback loop in a FPGA.

An Intense $γ$-ray Beam Line of 10 MeV Order Based on Compton Backscattering

Shanghai Laser Electron Gamma Source, a $γ$-ray beam line of 10MeV order was proposed recently. The beam line is expected to generate $γ$-ray with maximum energy of 22MeV by backward Compton scattering between CO$_2$ laser and electron in the 3.5GeV storage ring of future Shanghai Synchrotron Radiation Facility. The flux of non-collimated $γ$-ray can be 10$^9$ $\sim$ 10$^{10}$s$^{-1}$ if a commercial CO$_2$ laser of 100W order output power is employed and injected with optimized settings.

Photon generation by laser-Compton scattering at the KEK-ATF

We performed a photon generation experiment by laser-Compton scattering at the KEK-ATF, aiming to develop a Compton based polarized positron source for linear colliders. In the experiment, laser pulses with a 357 MHz repetition rate were accumulated and their power was enhanced by up to 250 times in the Fabry-Perot optical resonant cavity. We succeeded in synchronizing the laser pulses and colliding them with the 1.3 GeV electron beam in the ATF ring while maintaining the laser pulse accumulation in the cavity. As a result, we observed 26.0 +/- 0.1 photons per electron-laser pulse crossing, wh…

SPring-8 LEPS2 beamline: A facility to produce a multi-GeV photon beam via laser Compton scattering

We have constructed a new laser-Compton-scattering facility, called the LEPS2 beamline, at the 8-GeV electron storage ring, SPring-8. This facility provides a linearly polarized photon beam in a tagged energy range of 1.3--2.4 GeV. Thanks to a small divergence of the low-emittance storage-ring electrons, the tagged photon beam has a size (sigma) suppressed to about 4 mm even after it travels about 130 m to the experimental building that is independent of the storage ring building and contains large detector systems. This beamline is designed to achieve a photon beam intensity higher than that …

Spectral distribution and flux of $γ$-ray beams produced through Compton scattering of unsynchronized laser and electron beams

Intense, quasi-monochromatic, polarized $γ$-ray beams 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 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…

Efficient propagation of the polarization from laser photons to positrons through Compton scattering and electron-positron pair creation

We demonstrated for the first time the production of highly polarized short-pulse positrons with a finite energy spread in accordance with a new scheme that consists of two-quantum processes, such as inverse Compton scatterings and electron-positron pair creations. Using a circularly polarized laser beam of 532 nm scattered off a high-quality electron beam with the energy of 1.28 GeV, we obtained polarized positrons with an intensity of 10^4 e+/bunch. Magnitude of positron polarizations was determined as 73+-15(sta) +-19(sys)% by means of a newly designed positron polarimeter.

Monte Carlo simulation method of polarization effects in Laser Compton Scattering on relativistic electrons

Quasi-monochromatic, high energy and highly polarized $γ$-ray beam sources based on Compton scattering of laser photons (LCS) on relativistic electrons have developed for the last few decades as established instruments for nuclear physics studies. Following an extensive photoneutron experimental campaign at the LCS $γ$-ray beam line of the NewSUBARU synchrotron radiation facility at SPring8, Japan, a dedicated simulation code was developed for characterizing the incident $γ$-ray beams. The eliLaBr code is implemented using Geant4 and is available on the GitHub repository, at https://github.com…

A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

A high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532~nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064~nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO$_{3}$ crystal. The maximum achieved green power at 5 W IR pump power is 1.74 W with a total conversion efficiency of 34.8\%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7~kW with a corre…

用于研究非微扰QED中康普顿散射的高计数率电子探测器

High-rate electron detectors to study Compton scattering in non-perturbative QED

本文针对LUXE实验中激光-电子束碰撞产生的高通量康普顿散射粒子，提出由充气切伦科夫探测器和闪烁体屏组成的组合探测系统，并讨论从高计数率数据中重建非线性康普顿电子能谱以提取非微扰QED特征的方法。

Development of High Intensity Laser-Electron Photon Beams up to 2.9 GeV at the SPring-8 LEPS Beamline

A laser-Compton backscattering beam, which we call a `Laser-Electron Photon' beam, was upgraded at the LEPS beamline of SPring-8. We accomplished the gains in backscattered photon beam intensities by factors of 1.5--1.8 with the injection of two adjacent laser beams or a higher power laser beam into the storage ring. The maximum energy of the photon beam was also extended from 2.4 GeV to 2.9 GeV with deep-ultraviolet lasers. The upgraded beams have been utilized for hadron photoproduction experiments at the LEPS beamline. Based on the developed methods, we plan the simultaneous injection of fo…

Proposal for VEPP-4M beam energy measurement using magnetic spectrometer with Compton calibration and photon detector

A method for circular e$^-$/e$^+$ accelerator beam energy measurement is proposed. Coordinate of an electron (or a positron) in a focusing magnetic spectrometer built in a circular accelerator depends on its energy, two spectrometer parameters, and the circulating beam energy. The spectrometer parameters can be defined using minimum electron energies from Compton backscattering with two laser wavelengths, and an additional photon coordinate detector. The photon detector is calibrated at once at well-known beam energy. The VEPP-4M collider has appropriate equipment for the method implementation…

一种用于在LUXE实验中测量非线性康普顿散射的高通量电子探测器系统

A High-Flux Electron Detector System to Measure Non-linear Compton Scattering at LUXE

本研究针对强场非微扰QED研究需求，提出一种带分段充气Cherenkov探测器、闪烁体屏和摄像装置的新型高通量电子探测系统，用于LUXE等实验测量非线性康普顿散射，初步实验验证了电子能谱重建方法。