Transmutation of nuclear wastes using photonuclear reactions triggered by Compton backscattering photons at the Shanghai laser electrongamma source

Based on the facility of the Shanghai Laser Electron Gamma Source (SLEGS),the transmutation for nuclear wastes such as 137Cs and 129I is investigated.It is found that nuclear waste can be transmuted efficiently via photonuclear reaction triggered by gamma photons generated from Compton backscattering between CO2 laser photons and 3.5 GeV electrons.The nuclear activities of 137Cs and 129I are evaluated and compared with the results of transmutation triggered by bremsstrahlung gamma photons driven by ultra intense laser.Due to the better character of gamma photon spectrum as well as the high brightness of gamma photons,the transmutation rate of Compton backscattering method is much higher than that of the bremsstrahlung method.     

康普顿γ光源SLEGS对长寿命裂变产物126Sn的嬗变潜力

结合激光康普顿散射模拟程序4D-MCLCSS和Geant4软件包, 模拟上海激光电子γ源(SLEGS)的γ光产生及其对长寿命裂变产物¹²⁶Sn的光核嬗变过程, 研究嬗变率与嬗变靶几何参数的依赖关系, 并初步诊断基于SLEGS的光核嬗变产物分布, 获得¹²⁶Sn嬗变靶的最佳靶厚和半径分别为16cm和0.4cm, 对应的嬗变率为1.89×10⁶/s。研究结果表明:基于SLEGS的光核嬗变率比强激光驱动的轫致辐射法要高2倍, 而且升级潜力巨大。     

Gamma Ray Generation Through a 1.064 μM Laser Beam

We are exploring to process nuclear waste through nuclear transmutation method with ray irradiation. The ray employed for transmutation is generated in the way of Compton backscattering. Preliminary experiment is being developed on the NewSUBARU storage ring providing an electron beam with energy of 1 GeV, and 17.6 MeV ray will be generated through a head-on collision of the electron beam and a 1.064 m laser light. ray flux about the present experiment is predicted theoretically. A planned scheme for promoting the flux is also introduced, As well as the maximum laser power available for the storage ring is discussed.     

Experiment on Gamma Ray Generation by Laser Compton Scattering

A gamma ray generation facility was developed through laser Compton scattering on an electron beam storage ring, for the purpose of researching nuclear transmutation. Theoretical analysis on gamma ray yield and energy spectrum was performed, as well as EGS4 simulation code was employed to simulate the interaction of gamma ray and Ge detector. The acquired experimental results are in agreement with theory.     

Nuclear reactions triggered by laser-accelerated relativistic electron jets

A relativistic electron beam, generated by relativistic self-focusing of an ultra-high-intensity laser pulse in a He gas jet, was targeted onto high-Z materials for conversion to high-energy bremsstrahlung. Nuclear reactions in the primary converter materials as well as in secondary and tertiary targets placed directly behind the converter were analyzed with time-resolved -spectroscopy. The electron-jet temperature of more than 35 MeV, matching the giant dipole resonances of heavy nuclei, enabled us to efficiently generate photo-induced nuclear reactions. The measured temperatures are significantly higher than suggested by ponderomotive scaling. We supplemented our earlier measurement of the (, n) reaction cross section of ¹²⁹I with a method solely based on nuclear reactions. The photo-induced transmutation yields were increased by two orders of magnitude compared to earlier experiments. Simulations with the Monte Carlo code MCNPX confirm the experimental results . PACS 52.38.Ph; 25.20.Lj     

Scattering and absorption differential cross sections for double photon Compton scattering

The scattering and absorption differential cross sections for nonlinear QED process such as double photon Compton scattering have been measured as a function of independent final photon energy. The incident gamma photons are of 0.662 MeV in energy as produced by an 8 Ci¹³⁷Cs radioactive source and thin aluminum foils are used as scatterer. The two simultaneously emitted photons in this process are detected in coincidence using two Nal(T1) scintillation detectors and a slow-fast coincidence set-up of 30 nsec resolving time. The measured values of scattering and absorption differential cross sections agree with theory within experimental estimated error.     

A novel method for non-destructive Compton scatter imaging based on the genetic algorithm

Compton scattering tomography is widely used in numerous applications such as biomedical imaging, nondestructive industrial testing and environmental survey, etc. This paper proposes the use of the genetic algorithm (GA), which utilizes bio-inspired mathematical models, to construct an image of the insides of a test object via the scattered photons, from a voxel within the object. A NaI(Tl) scintillation detector and a 185 MBq ¹³⁷Cs gamma ray source were used in the experimental measurements. The obtained results show that the proposed GA based method performs well in constructing images of objects.     

Probing a nucleon spin structure at TESLA by the real polarized gamma beam

The recent proposals concerning the usage of the real polarized gamma beam, obtained by Compton backscattering of the laser photons off the electron beams from either the linear or circular accelerators were considered. The heavy quark photoproduction process, which gives a unique opportunity to measure the polarized gluon distribution, was investigated. Received: 22 March 1999 / Revised version: 17 June 1999 / Published online: 14 October 1999     

MeV- and Sub-MeV-photon Sources Based on Compton Backscattering at Spring-8 and KPSI-JAEA

Recently we have constructed two facilities for generating photon beams in the MeV and sub-MeV energy regions by means of the Compton backscattering with a laser and an electron beam at SPring-8 and at Kansai Photon Science Institute of Japan Atomic Energy Agency(KPSIJAEA).The MeV-photon source at SPring-8 consists of a continuous-wave optically-pumped far infrared laser with a wavelength of 118.8 μm and an 8 GeV stored electron beam.Present MeV-photon flux is estimated to be 1.3×10~3 photons/s.On the other hand,the sub-MeV-photon source at KPSI-JAEA consists of a pulse Nd:YAG laser with a wavelength of 1 064 nm and a 150 MeV electron beam accelerated by microtron.In the first trial of the photon production in this source,backscattered photon flux is estimated to be 20 photons/pulse.Both the Compton backscattered photon sources have possibilities to be used for new tools in various fields such as nuclear physics,materials science,and astronomy.     

Statistical simulation of multiple Compton backscattering process

A number of laboratories are currently developing monochromatic sources of X-rays and gamma quanta based on the Compton backscattering (CBS) of laser photons by relativistic electrons. Modern technologies are capable of providing a concentration of electrons and photons in the interaction point such that each primary electron can emit several hard photons. In contrast to the well-known nonlinear CBS process, in which an initial electron “absorbs” a few laser photons and emits a single hard one, the above-mentioned process can be called a multiple CBS process and is characterized by a mean number of emitted photons. The present paper is devoted to simulating the parameters of a beam of back scattered quanta based on the Monte Carlo technique. It is shown that, even in the case of strong collimation of a resulting photon beam, the radiation monochromaticity may deteriorate because of the contribution coming from the multiple photon emission, which is something that must be considered while designing new CBS sources.     

上海激光电子γ源

激光具有高强度、 高极化度等优异的性能。 用激光束轰击高能电子束就可以产生高强度、 高极化度的γ射线束。 上海激光电子γ源就是上海同步辐射装置上的这样一条束线站。 预计可以获得能量范围为1—22 MeV的准单色、 高强度（109—1011 s-1）和高极化度（线极化或圆极化）的γ射线束。 介绍了这条束线站目前的进展情况。 Shanghai Laser Electron Gamma Source (SLEGS) is a high intensity,short pulse and compact γ ray source which is based on inverse Compton scattering via interaction between pulsed high power laser beams and picosecond relativistic electron bunches. One of the attractive features of the laser Compton scattering is the easy control of polarization of the produced high energy photons that duplicates polarization of the applied laser beam. The γ ray with energy up to 22 MeV and intensity of 109—1011s 1 are expected to be produced by Compton backscattering of CO2 laser photons on the 3.5 GeV electrons bunches in the Shanghai Synchrotron Radiation Facility (SSRF). In this communication, we report same simulation results and the progressing status of SLEGS.     

Verification of terahertz-wave spectrophotometry by Compton backscattering of coherent synchrotron radiation

We developed a continuous-spectrum light beam from Compton backscattering by using coherent synchrotron radiation in an L-band linac at the Kyoto University Research Reactor Institute. The ratio of Compton backscattered photons to background photons when coherent synchrotron radiation was used was three times larger than when coherent transition radiation was used. The transmission spectrum of a polystyrene film in the terahertz-wave region was evaluated by measuring the spectrum of the Compton backscattered photons and it roughly agreed with that measured by a Martin–Puplett-type interferometer. The spectrophotometry using Compton backscattering shows promise as a new tool for investigations in terahertz-wave science.     

Generation of high-energy photons with large orbital angular momentum by compton backscattering

Usually, photons are described by plane waves with a definite 4-momentum. In addition to plane-wave photons, "twisted photons" have recently entered the field of modern laser optics; these are coherent superpositions of plane waves with a defined projection hm of the orbital angular momentum onto the propagation axis, where m is an integer. In this Letter, we show that it is possible to produce high-energy twisted photons by Compton backscattering of twisted laser photons off ultrarelativistic electrons. Such photons may be of interest for experiments related to the excitation and disintegration of atoms and nuclei, and for studying the photoeffect and pair production off nuclei in previously unexplored experimental regimes.     

Internal bremsstrahlung of the unique 137Cs β decay

The internal bremsstrahlung differential spectra of the singly forbidden unique ¹³⁷Cs β transition have been experimentally studied at different angles between the escape directions of electrons and γ photons. The measurements were performed on a β-γ-coincidence spectrometer with an effective collimator.     

Laser transmutation of iodine-129

We report the first successful laser-induced transmutation of ¹²⁹I, one of the key radionuclides in the nuclear fuel cycle. ¹²⁹I with a half-life of 15.7 million years is transmuted into ¹²⁸I with a half-life of 25 min through a (, n) reaction using laser-generated Bremsstrahlung. The integral cross-section value for the (, n) reaction is determined. These experiments offer a new approach to studying transmutation reactions with neutral and charged particles without resource to nuclear reactors or particle accelerators. PACS 52.38.Ph; 25.20.Lj     

驱动堆中长寿命核废料碘的嬗变研究

利用理论模拟和实验手段对加速器驱动的快中子堆消除常规反应堆排放的核废料碘进行了研究.实验中,利用加速器加速质子使其能量达到1.0GeV,并轰击重金属铅靶,利用靶中产生的次级中子诱发核废料¹²⁹I的嬗变,使其嬗变为稳定同位素¹³⁰Xe.对实验嬗变效率进行了理论模拟验证,进而拓宽到研究的驱动堆体系中.堆芯区的核燃料为乏燃料铀和钚,靶和初级热交换剂为液态铅.     

Monte Carlo calculation of electron spectra produced in water phantoms by 20 keV-1 GeV photons

Abstract

A Monte Carlo calculation for the energy spectra of electrons and positrons produced in infinite and semiinfinite water phantoms by photons ranging in energies from 20 keV to 1 GeV are presented. The dominant processes considered are the photoelectric effect, Auger effect, Compton effect, pair, and triplet production. Bremsstrahlung produced by electrons and positrons with energies greater than 1 MeV is also included. The effect of multiple Compton scattering, not considered in the earlier calculation, for the infinite phantom for photon energies higher than 2 MeV has been incorporated. For a semi-infinite phantom, multiple Compton scattering and backscattering through the top are considered. The results are compared with the earlier calculations for the first-collision spectrum. It is found that the inclusion of multiple Compton scattering significantly increases the average number of electrons/cm³ per photon/cm² at all energies considered whereas bremsstrahlung reduces the number of high energy electrons and produces more low energy electrons in the spectrum.     

Bremsstrahlung of the free electrons arising in an irradiated specimen

A model of the bremsstrahlung produced by photoelectrons, Auger electrons, and Compton electrons arising in an irradiated specimen is proposed. Calculations have shown that the contribution of the Compton electron bremsstrahlung shows up for monochromatic primary radiation of high-energy photons. For the primary radiation of x-ray tubes, only the bremsstrahlung spectrum of photoelectrons and Auger electrons is significant. The factors affecting the proportions between these components are considered. The bremsstrahlung spectral distribution of the mentioned electrons shows considerable deviations from that predicted by the Kramers theory that are due to the large depth of their occurrence and to the ambiguity of their energy. The region of the spectrum has been determined where the intensity of the electron bremsstrahlung is greater than the intensity of the x-ray tube polychromatic primary radiation scattered by the irradiated object.     

Evaluation of Transmutation of ^137Cs（γ, n） 136Cs Using Ultra-Intense Lasers in Solid Targets

Relativistic electrons produced in ultra-intense laser-solid interaction generate highly collimated γ-ray beams through Bremsstrahlung that can be used to induce photonuclear reactions. Photonuclear transmutation （of （% n） type） of ^137 Cs, one of the hazardous nuclear wastes with half-life of 30.17 years which cannot be transmuted practically with neutron bombardment due to its very low neutron capture cross section, has been considered. Nuclear activity of produced 136Cs with half-life of 13.16 days has been evaluated analytically using available experimental data. With irradiating a ^137Cs sample by p-polarized laser light of 10^20 Wcm^-2 and the repetition rate of 10Hz for 30min, the activity of 0.24 Bq is obtained. It is found that intensity has a large effect in yield around 10^21 Wcm^-2. For similar laser with intensity of 5 ×10^21 Wcm^-2, the activity increases with a factor of 10^5.     

Compton-Polarimeter für 2 MeV-Bremsstrahlung

A polarimeter for bremsstrahlung must simultaneously perform two functions: it must select photons within a small energy interval out of the continuous bremsstrahlung spectrum and it must measure the polarization of these photons. The polarimeter depends on the polarization sensitivity of the Compton process with a 5 mm Si(Li-drift) detector as scatterer and a plastic scintillator as photon detector. To improve the energy resolution of the polarimeter a second 0,5 mm Si(Li-drift) detector behind the scatterer has been placed in anticoincidence with the scatterer.