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Thomson scattering sources are known for generating quasi-monochromatic, high-brightness, and polarization-tunable X-rays, which are widely applied in fields such as fluorescence imaging, magnetic circular dichroism, and nuclear physics. In this paper, we present an experimental demonstration of polarization control at the Tsinghua Thomson scattering X-ray source (TTX) by adjusting the laser polarization. A specially designed Compton polarimeter is employed to effectively analyze the Degree of Linear Polarization (DoLP) of the X-rays produced at the TTX. Our results indicate that the DoLP of X-rays within a collecting angle of 1 / (3 γ) , where γ is the Lorentz factor of the relativistic electron, closely matches the DoLP of the laser. Furthermore, we demonstrate that the X-ray polarization can be continuously modulated from linear polarization to circular polarization by adjusting the laser polarization, which can significantly enhance the functionality and applicability of Thomson Scattering sources for scientific research. [ABSTRACT FROM AUTHOR]

Positron emission particle tracking (PEPT) is used to study a wide range of scientific, industrial, and biomedical systems, typically those inaccessible through conventional optical particle tracking techniques. However, in dense or thick-walled systems a fraction of the coincident gamma-rays emitted from a PEPT tracer, called Lines-of-Response (LoRs), are attenuated via Compton scattering. Additionally, at high source activity, random LoRs may be formed by two unrelated events. The incorporation of scattered or random LoRs decreases PEPT spatial accuracy and can distort the trajectory. In this work, we use validation experiments and simulations to investigate the spatial accuracy of the Birmingham Method (BM) PEPT algorithm when two key free parameters are changed: the total number of LoRs in the sample and the fraction of LoRs in the sample used to locate the tracer. Our results show that the default algorithm parameters are not suitable for all cases, however, Monte Carlo simulations of PEPT experiments can be used to estimate the optimal parameter values. Ultimately a variant of the BM, called Dynamic-BM, is demonstrated in a virtual PEPT experiment. Dynamic-BM uses the optimal parameters on a sample-by-sample basis improving PEPT accuracy in this case by 4.03% over the best constant parameters and 76.5% over the default parameters. These improvements make PEPT a more accurate and thus more useful tool. • Two key free parameters a PEPT algorithm are optimised for spatial accuracy. • Optimal parameter values are discovered through experiments and simulations of PEPT. • The Birmingham Method is extended to dynamically change parameter values. • Using optimal values, spatial errors decrease by 76.5% compared to default values. [ABSTRACT FROM AUTHOR]

The PREX-2 and CREX experiments in Hall A at Jefferson Lab are precision measurements of parity violating elastic electron scattering from complex nuclei. One requirement was that the incident electron beam polarization, typically ≈ 90 % , be known with 1% precision. We commissioned and operated a Møller polarimeter on the beam line that exceeds this requirement, achieving a precision of 0.89% for PREX-2, and 0.85% for CREX. The uncertainty is purely systematic, accumulated from several different sources, but dominated by our knowledge of the target polarization. Our analysis also demonstrates the need for accurate atomic wave functions in order to correct for the Levchuk Effect. We describe the details of the polarimeter operation and analysis, as well as (for CREX) a comparison to results from a different polarimeter based on Compton scattering. [ABSTRACT FROM AUTHOR]

We report here a theoretical proof of the limiting value of the velocity of target/particle responsible for various photon–electron interactions in the Compton scattering experiment which may be carried out in various applications such as gamma-ray spectroscopy. Compton scattering deals with the collision of photons with a target particle where both energy and momentum are transferred to the particle while the photon moves with reduced energy and a change of momentum. Here, the changed energy of a photon depends on the angle between the incident axis and scattered photon (θ), the rest mass of the electron, and the frequency of the photon before the collision. However, when some initial velocity is provided to an electron that is at rest initially, then in such cases, the particle obeys limiting value on velocity for a particular energetic photon to follow Compton scattering. In such cases, the changed frequency of photons also depends on the initial and final velocity of nonstationary electrons during a collision, including the angle (φ ′) between the recoil electron and incident axis. Here, we have presented the derivations to calculate the recoil velocity of the nonstationary electron. These terms are the accurate solution of the Compton shift. We have tried to calculate the upper limit or limiting values of the initial velocity of the target particle in Compton scattering. Further, we have computationally demonstrated that there is a dependence of scattered photon frequency on initial velocity of target particle (u) and mass of the target particle (m) at a higher scattering angle. Finally, numerical simulations were carried out with particles such as an electron, pion (+/-, 0) to verify the greater degree of accuracy of the particles in spectroscopic detectors such as gamma-ray spectroscopy and other high energy spectroscopic techniques. [ABSTRACT FROM AUTHOR]

MicroBeam Radiosurgery (MBRS, also referred to as Microbeam Radiation Therapy, MRT) is a potential clinical technique for the treatment of solid tumors. MBRS utilizes a series of narrow 30 to 50 μ m beams of ultra-high, lethal dose synchrotron x-ray radiation (peaks) separated by relatively wide spaces of no radiation (valleys) with spacings of 200 to 400 μ m center-to-center. It has been observed that healthy small animal tissue, including neurologic tissue (brain and spinal cord), can recover quickly, but solid tumors take a prolonged time of many months to regrow. This vast difference in recovery period is the basis for the therapeutic effect of MBRS on tumors. The interactions of X rays and tissue cells in alignment with the microbeams cause some deposited dose to be delivered to the tissue between the peak region of the microbeams and spill into the valley regions. It is generally believed that the dose delivered between the microbeam peak regions must be maintained at a low level to maximize the efficacy of MBRS. To date the most widely used criterion for the efficacy of MBRS is known as the Peak-to-Valley Dose Ratio (PVDR). This ratio depends on the geometry of the system along with the X-ray spectra. As most of the experimental work to date has used polychromatic microbeams of X rays, the PVDR will change with the energy range and spectrum. We are reporting novel investigations and present data suggesting considerations additional to the PVDR are needed for the design of a human clinical facility. In this paper we studied X-ray interactions in simulated human biologic material (Water - H 2 O) using the MCNP6 radiation transport computer code. The new slit geometry dependent information includes: (1) rounding of peak shape; (2) decrease of the maximum peak height with decreasing peak slit width; (3) qualitative and quantitative changes to the "skirt" radiation dose delivered in the valley regions adjacent to the peak regions. All these effects were highly dependent on incident X-ray energy because of the transition of the dominant X-ray interaction from the photo-electric effect to atomic Compton scattering with increasing energy in the 50 to 300 keV range. Changes in the radiation dose distributions, as a function of X-ray energy, delivered to both the peak and valley regions after the X-ray interactions were investigated in detail. Insights from understanding how the dose is delivered in the valley regions have implications for the calculations of the clinical radiation dose planning. Accurate dose distribution calculations are necessary in human clinical treatment since it is anticipated that most patients will have received prior radiation therapy treatments that need to be considered in microbeam dose planning so that radiation side-effects and toxicity are accounted for and minimized. This work suggests an X-ray energy range of 130–250 keV is the most appropriate range for a human clinical facility. Using the results of this work, the authors suggest that the PVDR may not be the only criteria one should consider for determining the energy range needed for a human clinical facility; analysis of the data presented demonstrates the benefit of also using the full width at 10% maximum of the distribution. [ABSTRACT FROM AUTHOR]

We present a novel method to perform gamma-ray spectroscopy suitable for extreme pileup situations, wherein traditional pulse-height spectroscopy is infeasible or impractical. One example of such application is spectral characterization of intense laser-based radiation sources that employ laser wakefield acceleration, in which a large number of photons can be produced in a well-collimated beam on a picosecond or shorter timescale. The method relies on the angularly-resolved calorimetric measurement of Compton scattering. The probability for a photon to undergo Compton scattering into a given solid angle is a function of its energy and is described by the Klein–Nishina formula. By first Compton scattering the incident beam and then measuring the total energies deposited in multiple detectors placed at various scattering angles, the incident beam energy spectrum can be reconstructed without resolving the individual events in detectors. We compare the performance of an maximum likelihood expectation maximization algorithm with that of an artificial neural network to measure the energy spectrum of a beam of monoenergetic gamma rays from 137Cs decay. We demonstrate that the method can be used to reconstruct the characteristic inverse Compton scattering spectra. [ABSTRACT FROM AUTHOR]

The uncertainty of the energy measurement of the electron beam on circular electron positron collider (CEPC) must be smaller than 10 MeV to make sure the accurate measurement of the mass of the Higgs boson. In order to simplify the energy measurement system, a new method is proposed by fitting the Compton edge of the energy distribution of the gamma ray from a microwave–electron Compton scattering. With our method, the uncertainty of the energy measurement is 6 MeV for the electron energy of 120 GeV in the Higgs mode. In this system, the energy resolution of the gamma detection needs to reach 1 0 − 4 . Therefore, only the high-purity germanium (HPGe) detector can meet the critical requirement. In a head-on collision mode, the initial photons should be microwave photons with the wavelength of 3.04 centimeters. A cylindrical resonant cavity with selected T M 010 mode is used to transmit microwaves. After the microwave–electron Compton backscattering, the scattered photons and the synchrotron-radiation background transmit a shielding structure and then are detected by a HPGe detector at the end of the beam line of the synchrotron-radiation applications. The hole radius in the side wall of the cavity is about 1. 5 mm to allow the electron beam passing through. The results of the computer simulation technology (CST) software shows that the influence of the hole radius on the cavity field is negligible. The change of the resonance frequency can be easily corrected by fine-tuning the cavity size. [ABSTRACT FROM AUTHOR]

We propose PET scanners using low atomic number media that undergo a persistent local change of state along the paths of the Compton recoil electrons. Measurement of the individual scattering locations and angles, deposited energies, and recoil electron directions allows using the kinematical constraints of the 2-body Compton scattering process to perform a statistical time-ordering of the scatterings, with a high probability of precisely identifying where the gamma first interacted in the detector. In these cases the Line-of-Response is measured with high resolution, determined by the underlying physics processes and not the detector segmentation. There are multiple such media that act through different mechanisms. As an example in which the change of state is quantum-mechanical through a change in molecular configuration, rather than thermodynamic, as in a bubble chamber, we present simulations of a two-state photoswitchable organic dye, a 'Switchillator', that is activated to a fluorescent-capable state by the ionization of the recoil electrons. The activated state is persistent, and can be optically excited multiple times to image individual activated molecules. Energy resolution is provided by counting the activated molecules. Location along the LOR is implemented by large-area time-of-flight MCP-PMT photodetectors with single photon time resolution in the tens of ps and sub-mm spatial resolution. Simulations indicate a large reduction of dose. [ABSTRACT FROM AUTHOR]

The spectrum of laser–plasma generated X-rays is very important, it characterizes electron dynamics in plasma and is basic for applications. However, the accuracies and efficiencies of existing methods to diagnose the spectrum of laser–plasma based X-ray pulse are not very high, especially in the range of several hundred keV. In this study, a new method based on electron tracks detection to measure the spectrum of laser–plasma produced X-ray pulses is proposed and demonstrated. Laser–plasma generated X-rays are scattered in a multi-pixel silicon tracker. Energies and scattering directions of Compton electrons can be extracted from the response of the detector, and then the spectrum of X-rays can be reconstructed. Simulations indicate that the energy resolution of this method is approximately 20% for X-rays from 200 to 550 keV for a silicon-on-insulator pixel detector with 12 μ m pixel pitch and 500 μ m depletion region thickness. The results of a proof-of-principle experiment based on a Timepix3 detector are also shown. [ABSTRACT FROM AUTHOR]

A new electromagnetic calorimeter consisting of 140 lead tungstate (PbWO 4) scintillating crystals was constructed for the PrimEx- η experiment at Jefferson lab. The calorimeter was integrated into the data acquisition and trigger systems of the GlueX detector and used in the experiment to reconstruct Compton scattering events. The experiment started collecting data in the spring of 2019 and acquired about 30% of the required statistics. The calorimeter is a prototype for two PbWO 4 -based detectors: the Neutral Particle Spectrometer (NPS) and the lead tungstate insert of the Forward CALorimeter (FCAL) of the GlueX detector. The article presents the design and performance of the Compton calorimeter and gives a brief overview of the FCAL and NPS projects. [ABSTRACT FROM AUTHOR]

Shanghai laser electron gamma source (SLEGS) is an energy-variable gamma-ray source developed based on the inverse Compton scattering of 10640 nm photons from a 100 W CO 2 laser on 3.5 GeV electrons from the Shanghai Light Source. It produces gamma-rays in the energy range of 0.4–21.7 MeV with a flux of 10 5 –10 7 photons/s. A collimator system was designed to produce quasimonochromatic gamma-ray beams with a best possible bandwidth of 1.1%–4.4% and filter out the substandard gamma-rays. The collimator system composed of coarse and fine collimators, constitutes a critical component of the SLEGS. By Geant4 simulations, we show that the collimator system is effective in tuning beam bandwidths and regular dodecagonal beam spots at the target position. [ABSTRACT FROM AUTHOR]