Laser-Compton Scattering X-ray Research Articles

Computational method for the optimization of quasimonoenergetic laser Compton x-ray sources for imaging applications.

The development of compact quasimonoenergetic x-ray radiation sources based on laser Compton scattering (LCS) offers opportunities for novel approaches to medical imaging. However, careful experimental design is required to fully utilize the angle-correlated x-ray spectra produced by LCS sources. Direct simulations of LCS x-ray spectra are computationally expensive and difficult to employ in experimental optimization. In this manuscript, we present a computational method that fully characterizes angle-correlated LCS x-ray spectra at any end point energy within a range defined by three direct simulations. With this approach, subsequent LCS x-ray spectra can be generated with up to 200 times less computational overhead.

Study on X-ray enhancement in Laser-Compton scattering for auger therapy

Purpose Monochromatic hard X-rays with high brightness are desired for medical applications including Auger therapy. One can generate such X-rays through laser-Compton scattering (LCS) by allowing photons from a compact laser system to interact with electrons accelerated by a compact electron accelerator. In this paper, after a brief description of laser-Compton X-ray sources, a scheme called crab crossing to enhance the X-ray intensity is proposed. The effect of crab crossing is evaluated, and we report our dedicated laser system for the crab crossing LCS research. Materials and methods The luminosity enhancement factor by crab crossing is evaluated. For the electron beam, a rf deflector will be used to generate a tilted electron beam. For the laser system, chirped pulsed amplification is adopted. Yb-doped optical fibers and a Yb:YAG thin-disk is used for the laser gain media. Results The luminosity enhancement factor by crab crossing is expected to be 3.8 when the crossing angle is 45 degrees. 10mJ pulse energy was achieved by thin-disk regenerative amplifier. The pulse duration after the pulse compressor was about 1.5 ps. Conclusion We are going to demonstrate the LCS X-ray enhancement by crab crossing of electron beam and laser pulse. The expected enhancement factor is 3.8. We have successfully finished the laser development and the proof-of-principle experiment will be conducted soon.

K-edge imaging with quasi-monochromatic LCS X-ray source on the basis of S-band compact electron linac

A quasi-monochromatic hard X-ray source via laser Compton scattering (LCS) was developed on the basis of an S-band compact electron linac at AIST. The total number of photons generated and the maximum X-ray energy were ∼107photons/s and 41keV, respectively, when a 42-MeV electron beam was collided with an 800-nm Ti:sapphire laser at a 15° collision angle. We successfully demonstrated K-edge imaging using these LCS X-rays for the high-contrast observation of a human phantom with barium sulfate-concentrated blood vessels. In this paper, we describe the results of the K-edge imaging and analytical estimates of the contrast enhancement effect for the energy range ∼37keV, which corresponds to the K-edge energy of barium.

Preliminary experimental study and simulation of an energy-tunable quasi-monochromatic laser-Compton X/γ-ray source

We propose a slanting collision scheme for Compton scattering of a laser light against a relativistic electron beam. This scheme is suitable to generate an energy-tunable X/γ-ray source. In this paper, we present theoretical study and simulation of the spectral, spatial and temporal characteristics of such a source. We also describe two terms laser-Compton scattering (LCS) experiments at the 100 MeV Linac of Shanghai Institute of Applied Physics, where quasi-monochromatic LCS X-ray energy spectra with peak energies of ∼30 keV are observed successfully. These preliminary investigations are carried out to understand the feasibility of developing an energy-tunable quasi-monochromatic X/γ-ray source, the future Shanghai Laser Electron Gamma Source.

An X-ray spectroscopy system and its application to the laser-Compton scattering experiments

One of the main challenges for the laser-Compton scattering (LCS) experiments with the oblique configuration at the Linac of SINAP is the low signal to noise ( S/N) ratio due to the low intensity of LCS signals. X-ray spectroscopy system mainly consisting of an X-ray Si(Li) detector, electronics, and LabVIEW-based data acquisition has been developed for the low S/N ratio experiments. Spectral characteristics of such a system (i.e., energy and time resolutions, data acquisition efficiency, and system instability) have been determined by the 55Fe, 241Am, and 238Pu radioactive sources. In order to extract the LCS X-ray spectrum, several methods for the enhancement of the S/N ratio have been achieved and data have been taken alternatively with laser pulse on and off. Thanks to these methods the S/ N ratios have been optimized. Finally, the generated LCS X-ray spectrum has been achieved through the subtraction of the on/off laser accumulated spectra.

X-ray generation from slanting laser–Compton scattering for future energy-tunable Shanghai Laser Electron Gamma Source

There is great interest in the generation of energy-tunable, bright, short-pulse X/γ-ray sources, which are required in various research fields. Laser–Compton scattering (LCS) is considered to be one of the most promising methods to implement this kind of X/γ-ray source. At the 100-MeV LINAC of the Shanghai Institute of Applied Physics, a 2-J, 8-ns, 1064-nm, Q-switched Nd:YAG laser is brought to a slanting collision at 40° (44°) with an 112-MeV, 0.9-ns (rms) relativistic electron beam. We measured the LCS X-ray energy spectrum with a peak energy of 31.73±0.22stat±1.64syst keV and a peak width (rms) of 0.74±0.26stat±0.03syst keV. This preliminary investigation was carried out to understand the feasibility of developing an energy-tunable X/γ-ray source. Based on this study, the future Shanghai Laser Electron Gamma Source (SLEGS) at the Shanghai Synchrotron Radiation Facility (SSRF) can be constructed to be not only an energy-tunable γ-ray source by guiding the laser incident angle from laser–Compton scattering, but also a high flux (∼1010 photons/s or even higher) γ-ray source by adding a laser super-cavity.

Quasi-monochromatic hard X-ray source via laser Compton scattering and its application

We have developed a quasi-monochromatic hard X-ray source via laser Compton scattering (LCS) based on an S-band compact electron linac at AIST. The number of total photons and the maximum X-ray energy was 10 7 photons/sec and about 40 keV, respectively, in 15-degree crossing angle between a 42 MeV electron beam and a 800 nm Ti:Sa laser. The biological observation of the human bone with fractures has been successfully demonstrated using the LCS X-ray of 26.4 keV with the in-line phase contrast scheme. Good contrast enhancement is clearly observed between the absorption and the phase contrast images.

A laser-Compton scattering prototype experiment at 100 MeV linac of Shanghai Institute of Applied Physics

As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42 degrees between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1+/-4.4|(stat)+/-2.1|(syst) keV and the peak width (rms) of 7.8+/-2.8|(stat)+/-0.4|(syst) keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2+/-2.0) x 10(2) Hz can be achieved.

Laser-Compton scattering as a tool for electron beam diagnostics

Laser-Compton scattering (LCS) experiments were carried out at the Idaho Accelerator Center (ICA) using the 5 ns (FWHM) and 22 MeV electron beam. The electron beam was brought to an approximate head-on collision with a 7 ns (FWHM), 10 Hz, 29 MW peak power Nd:YAG laser. We observed clear and narrow X-ray peaks resulting from the interaction of relativistic electrons with the 532 nm Nd:YAG laser second harmonic line on top of a very low bremsstrahlung background. We have developed a method of using LCS as a non-intercepting electron beam monitor. Unlike the method used by Leemans et al. (1996), our method focused on the variation of the shape of the LCS spectrum rather than the LCS intensity as a function of the observation angle in order to extract the electron beam parameters at the interaction region. The electron beam parameters were determined by making simultaneous fits to spectra taken across the LCS X-ray cone. We also used the variation of LCS X-ray peak energy and spectral width as a function of the detector angles to determine the electron beam angular spread, and direction and compared the results to the previous method. Experimental data show that in addition to being viewed as potential bright, tunable and monochromatic X-ray source, LCS can provide important information on electron beam pulse length, direction, energy, angular, and energy spread. Since the quality of LCS X-ray peaks, such as degree of monochromaticity, peak energy and flux, depends strongly on the electron beam parameters, LCS can therefore be viewed as an important non-destructive means for electron beam diagnostics.

Determination of electron beam parameters by means of laser-Compton scattering

Laser-Compton scattering (LCS) experiments were carried out at the Idaho Accelerator Center using the 5 ns (FWHM) and 22 MeV electron beam. The electron beam was brought to an approximate head-on collision with a 29 MW, 7 ns (FWHM), 10 Hz Nd:YAG laser. Clear and narrow x-ray peaks resulting from the interaction of relativistic electrons with the Nd:YAG laser second harmonic line at 532 nm were observed. We have developed a relatively new method of using LCS as a nonintercepting electron beam monitor. Our method focused on the variation of the shape of the LCS spectrum rather than the LCS intensity as a function of the observation angle in order to extract the electron beam parameters at the interaction region. The electron beam parameters were determined by making simultaneous fits to spectra taken across the LCS x-ray cone. This scan method allowed us also to determine the variation of LCS x-ray peak energies and spectral widths as a function of the detector angles. Experimental data show that in addition to being viewed as a potential bright, tunable, and quasimonochromatic x-ray source, LCS can provide important information on the electron beam pulse length, direction, energy, angular and energy spread. Since the quality of LCS x-ray peaks, such as degree of monochromaticity, peak energy and flux, depends strongly on the electron beam parameters, LCS can therefore be viewed as an important nondestructive tool for electron beam diagnostics.

Laser-Compton scattering from a 20MeV electron beam

Abstract Laser-Compton scattering (LCS) experiments were carried out at the Idaho Accelerator Center. A 20 MeV electron beam was brought to a head-on collision with a 100 MW 7 ns Nd:YAG laser. We observed clear narrow LCS X-ray spectral peaks resulting from the interaction of the electron beam with the two Nd:YAG laser photon lines of 1064 and 532 nm. The LCS X-ray energy lines and widths were measured as a function of the electron beam energy and energy spread, respectively. The results recorded showed good agreement with the predicted values.