Measurement of the high energyγ-rays from heavy ion reactions usingČerenkov detector

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.

Study on absorption coefficients of dual-energy γ-rays in determining phase fractions of multiphase flows

This paper discusses the principle and mathematical method to measure the phase fractions of multiphase flows by using a dual-energy gamma-ray system. The dual-energy gamma-ray device is composed of radioactive isotopes of 241Am and 137Cs with emission energies of 59.5 keV and 662 keV respectively. A rational method to calibrate the absorption coefficient was introduced in detail. The statistical error has been analyzed on the basis of the accurate absorption coefficient which enables determination phrase fractions almost independent of the flow regime. Improvement has been achieved on the measurement accuracy of phase fractions.

Dense positrons and γ-rays generation by lasers interacting with convex target

We use quantum electrodynamics particle-in-cell simulation to study the generation of dense electron–positron plasma and strongγ-ray bursts in counter-propagating laser beam interactions with two different solid targets,i.e.planar(type I)and convex(type II).We find that type II limits fast electron flow most effectively.while the photon density is increased by about an order of magnitude and energy by approx.10%–20%compared with those in type I target.γ-photon source with an ultrahigh peak brilliance of 2?×?1025 photons/s/mm2/mrad2/0.1%BW is generated by nonlinear Compton scattering process.Furthermore,use of type II target increases the positron density and energy by 3 times and 32%respectively,compared with those in type I target.In addition,the conversion efficiencies of total laser energy toγ-rays and positrons of type II are improved by 13.2%and 9.86%compared with type I.Such improvements in conversion efficiency and positron density are envisaged to have practical applications in experimental field.

The Gradient of γ-Rays Irradiation’s Energy and Its Use in Treatment of Cancer Diseases

The Ionising irradiations used mostly in the treatment of tumoral diseasses are: X, γ, β and e irradiations. The discussion will be about γ irradiations, produced in linear accelerator with photon energy 6 MV and 15 MV. It is important to know the absorption performance before and after the electronic equilibrium. This is a reason that we’ve used the function of dose gradient for irradiations γ. It represents the velocity of dose change as a function of depth in tissue. From skin to maximum dose value, the increase of G-function is more accentuated for γ-rays than for β-particles while after that the G-function decreasing is less sharp for γ-rays. Finally, we’ll discuss about the advantages in terms of radiation protection of γ-rays used in radiotherapy.

X and γ-rays emission probabilities of ^(131)I and ^(133)Xe

Radioactive nuclides as 131I and 133Xe are increasingly used for both clinical diagnosis and therapeutic treatment of the patient. For example, 131I is used for the treatment of thyroid gland cancer. Otherwise, 133Xe is used in ventilation studies to assess and evaluate pulmonary function and to provide images of the lungs in both cardiac and pulmonary diseases, such as asthma, pulmonary emphysema, bronchiectasis, carcinoma of the lung, and pulmonary embolism [1,2]. Furthermore, cerebral blood flow is measured using 133Xe inhalation. In this study, the X and γ-rays emission probabilities in the decay of 131I and 133Xe were precisely measured with a calibrated Si(Li) detector. Results of this study were compared using available results in the literature. Good agreement was observed between our results and available results in the literature.

A Study of Changes in the Element Composition and Structure of Surfaces under Irradiation of Dense Xenon Gas （270 bar） by y-Rays with a Maximum Energy of 10 MeV

A high-pressure chamber filled with natural xenon （XeHPC） under initial pressure 270 bar was irradiated during 43 hours by braking γ-rays with a maximum energy of 10 MeV at the MT-25 electron accelerator at an average beam intensity of 20-22 μA. After about 14 hours of irradiation, the pressure in the XeHPC dropped to 185 bar and did not change till the end of the irradiation cycle. Upon completion of exposure, part of the gas from XeHPC was bypassed into a separate reservoir to measure the xenon composition by mass-analyzer QMA-200. After the opening of the XeHPC, an inner assembly without xenon was fixed at the Ge-detector for measurement of γ-spectra of radionuclides produced in the XeHPC and the background during 15 hours. A visual inspection of the inner assembly indicated that the surfaces of its elements were covered with a siskin green layer. Using SEM （scanning electron microscopy） studies and MPRA （microprobe roentgen analysis） , the element compositions of the synthesized micro-objects and micro-particles were determined. In order to explain the observed anomalies in the formation of new elements in the micro-particles and micro-objects, nuclear fission and synthesis reactions should be used.

γ射线辐照改性聚碳硅烷提高热解陶瓷产率

在N2气中用γ射线对聚碳硅烷(Polycarbosilane,PCS)进行辐照,利用傅里叶红外光谱分析、凝胶渗透色谱分析和热重分析等手段研究了不同吸收剂量下PCS的化学结构、分子量和热分解特性。结果显示,经γ射线辐照处理后的PCS轻微失重,分子量和软化点随着吸收剂量的增加而增加,说明PCS经辐照后发生了分子间的交联反应。红外分析表明,PCS的交联主要是通过Si-H键和C-H键的断裂产生新的Si-C-Si结构实现的。热重分析表明,PCS热解为碳化硅的陶瓷产率随吸收剂量的增加显著升高,剂量达到1.5 MGy后PCS样品的陶瓷产率基本提高到稳定值,此时,陶瓷产率从改性前的61.9%提高到80.0%。

Study on γ-Ray Irradiation Mutation of Bacillus subtilis NCD-2

[Objective] To study the effect of 60Co γ-rays irradiation on Botrytis cinerea biocontrol strains—Bacillus subtilis NCD-2. [Method] NCD-2 cells were irradiated at different doses of γ-rays from 100 to 2 000 Gy. The strains were screened by plate confrontation method and Oxford cup diffusion. [Result] The curves of the relationship of irradiation dose and mutation and lethal rate were obtained. The results showed that lethal rate increased with the increasing of irradiation dose. The lethal rate of 1 000 Gy irradiation dose reached 99.50%. The mutation rate increased below 500 Gy and decreased above 500 Gy. The highest mutation rate occurred when the irradiation dose was between 400 and 700 Gy, and the average mutation rate was above 15%. The optimal irradiation dose was 500 Gy, when the average mutation rate was 26.51% and lethal rate was 77.71%. [Conclusion] This study provided references for γ-rays irradiation mutation of Bacillus subtilis.

Mutagenesis of Arabidopsis Thaliana by N^+ Ion Implantation

Ion implantation, as a new biophysically mutagenic technique, has shown a great potential for crop breeding. By analyzing polymorphisms of genomic DNA through RAPD-based DNA analysis, we compared the frequency and efficiency of somatic and germ-line mutations of Arabidopsis thaliana treated with N^＋ ion implantation and γ-rays radiation. Our data support the following conclusions： （1） N^＋ ion implantation can induce a much wider spectrum of mutations than γ-rays radiation does; （2） Unlike the linear correlation between the doses and their effect in γ-rays radiation, the dose-effect correlation in N^＋ ion implantation is nonlinear; （3） Like γ-rays radiation, both somatic and germ-line mutations could be induced by N^＋ ion implantation; and （4） RAPD deletion patterns are usually seen in N^＋ ion implantation induced mutation.

Study on the Phenotypic Mutation Generated from ^(60)Coγ-ray Irradiated Oxlias triangularis Purpurea Regeneration System

Mutations induced from tissue culture are easily to be separated,which might be propagated in the same medium,especially for the color-leaf ornamental grass,Oxalis triaggularis purpurea.Mutations of the ornamental traits in the tissue culture bottle could be investigated easily.The 35 d regeneration system group showed the lowest adventitious bud number and adventitious root number among 4 inoculation dates by 50 Gy dose of ^(60)Coγ radiation.More studies were carried out based on the 35d differentiation state of O.triangularis purpurea regeneration system.The 35 d regeneration system was then irradiated by 10,25 and 50 Gy doses of ^(60)Coγ rays.Numbers of adventitious buds and roots induced from the regeneration system were cut down with the increment of radiation doses.Seedling length was not distinctly reduced at the absorbed doses of 10 and 25 Gy,but reduced distinctly under 50 Gy of ^(60)Coγ irradiation.The optimal irradiation dose for 35 d O.triangularis regeneration system survival and mutation induction was approximately 25 Gy.The M_2 phenotypic mutation rate was 2.9%,especially,and the leaf number mutation accounted for 76%of the total mutation.The phenotypic mutations,especially in the 10 Gy group,on 0.1 m M Vc containing MS medium were recovered,which indicated that ROS plays a key role in the phenotypic mutation induced by ^(60)Coγ -rays.

Sublethal Irradiation Promotes Migration and Invasiveness of Prostate Cancer PC-3 Cells:Implications for Radiotherapy of Human Prostate Cancer

OBJECTIVE To study the changes in the matrix metalloproteinases-2 and 9 （MMP2, MMP9） induced by ^60Co γ-ray external irradiation of human prostate cancer PC-3 cells. METHODS Human prostate cancer PC-3 cells were irradiated with different doses of ^60Co γ-rays. Cell migration and invasiveness were evaluated and the expression of MMP2, and MMP9 was investigated by RT-PCR, Western blotting and flow cytometry（FCM）. RESULTS Irradiation enchances invasive protential at the doses of 1,3 and 5 Gy,whereas it significantly inhibits cell migration. CONCLUSION The different doses of ^60Co γ-ray external irradiation for prostate cancer may have different effects through the changes of MMP2, and MMP9 expression.

Could bright γ-ray burst optical transients have been recorded historically?

The brightest optical flash from a γ-ray burst （GRB） was, briefly, a naked- eye object. Several other GRBs have produced optical transients only slightly fainter. We argue that, based upon the recently accumulated data from hundreds of GRB transients, many such optical events should have been visible to the unaided eye in the course of human history. The most likely repositories of such observations are histor- ical records from the Orient, and we have located and discuss a number of candidates. We also consider the value of such observations, should any very likely ones be uncovered, to modern astrophysics.

由超拍电子伏特加速器产生的超高能伽马射线气泡

We report the detection of aγ-ray bubble spanning at least 100deg2 in ultra-high energy(UHE)up to a few PeV in the direction of the star-forming region Cygnus X,implying the presence super PeVatron(s)accelerating protons to at least 10 PeV.A log-parabola form with the photon indexΓ(E)=(2.71±0.02)+(0.11±0.02)×log10(E/10 TeV)is found fitting the gamma-ray energy spectrum of the bubble well.UHE sources,“hot spots”correlated with very massive molecular clouds,and a quasi-spherical amorphousγ-ray emitter with a sharp central brightening are observed in the bubble.In the core of~0.5°,spatially associating with a region containing massive OB association(Cygnus OB2)and a microquasar(Cygnus X-3),as well as previously reported multi-TeV sources,an enhanced concentration of UHEγ-rays is observed with 2 photons at energies above 1 PeV.The general feature of the bubble,the morphology,and the energy spectrum,are reasonably reproduced by the assumption of a particle accelerator in the core,continuously injecting protons into the ambient medium.

Cross-sections of the ^(238)U(n,γ) ^(239)U reaction in the 3.0-7.0 MeV energy region measured by relative activation method

The reaction cross-sections of^(238)U(n,γ)^(239)U have been experimentally determined at neutron energies of6.117±0.119 MeV,4.626±0.086 MeV,and 3.622±0.348 MeV employing the relative activation approach along with the off-line γ-ray spectroscopy method.The D(d,n)3He reaction was utilized to obtain monoenergetic neutrons of the required energy,and the^(197)Au(n,γ)^(198)Au reaction cross-sections were adopted as the referential standard to ascertain the neutron capture cross-sections of^(238)U.Furthermore,the effects of low-energy scattered neutrons,neutron fluence fluctuations,counting of geometric corrections when measuring γ-rays,and neutron and γ-ray self-absorption caused by the sample thickness have been considered and revised in the present work.For a comparison with experimental results,the cross-sections of the^(238)U(n,γ)^(239)U reaction were calculated theoretically with the original parametric TALYS-1.9 program.The experimental measurements were in contrast to previous experimental re sults and the evaluation data available for ROSFOND-2010,CENDL-3.2 and ENDF/B-VIII.0.

Effect of annealing atmospheres on the scintillation properties of Ce^(3+)‑doped YAG nanoscintillator

Background In this study,three sample detectors have been prepared by using cerium-activated YAG nanoscintillator(Y_(3)Al_(5)O_(12):Ce^(3+))synthesized by sol-gel method and heat-treat at 900°C for 2 h in different atmospheres such as vacuum,air and nitrogen.Purpose Many studies about YAG:Ce^(3+)single crystal have been carried out,but the material at the nanoscale remains not enough understood.The objective of the present paper is to investigate the effects of annealing atmosphere on the scintillation properties and identify the suitable atmosphere that allow to design radiation detectors with high scintillation efficiency.Methods In order to accurately assess the scintillation properties,the nanoscintillator sample powders have been designed as a detector,in which,preparation operations such as surface homogenization and efficiency coupling with photomultiplier tube(PMT)window were developed.The study was performed usingγ-rays 662 keV released from137Cs radioactive source,the bi-alkali GDB-4FF PMT was used as a photodetector.Nuclear instrumentation chain was set up in order to collect the pulse height spectra,NaI:Tl single-crystal scintillator was used as a reference detector to estimate the scintillation light yield.The delayed coincidence method was used for measuring the scintillation decay time of nanoscintillator sample detectors.Results The sample detector annealed at vacuum atmosphere exhibits the best scintillation properties,the scintillation light yield was estimated to be 14,600±3400 ph/MeV and the fast component in the scintillation decay was 90 ns.Conclusion The vacuum is the suitable atmosphere which allows the development of radiation detectors with high scintillation efficiency.

Determination of DNA single-strand breaks by low-energy heavy ion and analysis of dose-effect curves

Calf thymus DNA was exposed to low-energy heavy ions (N+) and 60Co-γ-rays, and the dose-effect on DNA single-strand breaks (SSB) has been investigated. The results indicate that the dose-effect curve by N+ irradiation is different from that of conventional ionizing radiation. While the curve from γ-irradiation follows exponential type, the effect curve produced by N+ ion is of 'saddle type'. The yield of DNASSB per dose unit per DNA unit remained at a certain level under different doses of γ-rays. In contrast, the DNASSB at low dosage region of N+ showed an obvious peak before it decreased rapidly to a lower level.

X-ray flares of γ-ray bursts: Quakes of solid quark stars?

A star-quake model is proposed to understand X-ray flares of both long and short γ-ray bursts (GRBs) in a solid quark star regime. Two kinds of central engines for GRBs are available if pulsar-like stars are actually (solid) quark stars, i.e., the SNE-type GRBs and the SGR-type GRBs. It is found that a quark star could be solidified about 103 to 106 s later after its birth if the critical temperature of phase transi- tion is a few Metga-electron-volts, and then a new source of free energy (i.e., elastic and gravitational ones, rather than rotational or magnetic energy) could be possible to power GRB X-ray flares.

Radio core dominance of Fermi/LAT-detected AGNs

We present a sample of 4388 AGNs with available radio core-dominance parameters—defined as the ratio of the core flux densities to the extended ones, R = S_(core)/S_(ext).—which includes 630 Fermi-detected AGNs from the fourth source catalog(4FGL) of the Fermi Large Area Telescope(Fermi/LAT);the rest are non-Fermi-detected AGNs. In our sample, 584 blazars are Fermi-detected and 1310 are not. The sample also contains other subclasses, such as Seyferts, Fanaroff-Riley I/II galaxies, and normal galaxies.We investigate various properties of the Fermi-detected and non-Fermi-detected AGNs by using core-dominance parameters,capitalizing on a previous study which showed that R is a good indicator of beaming. We then calculate radio spectral indices for the whole sample, and adopt γ-ray-photon indices for the Fermi AGNs from the 4FGL catalog to discuss the properties of different subclasses. We obtain a relation between the core-dominance parameters and the radio spectral indices for both Fermi and non-Fermi sources, assuming a two-component model in the radio band. Our previous study ruled out the assumption that the core-dominance parameters and radio spectral indices are quite different for different AGN subclasses. This holds not only for Fermi sources but also for non-Fermi sources. In particular, R is, on average, greater for the former AGNs than for the latter.In this study, we enlarge our sample with available values of R to 4388 AGNs, and the obtained conclusions are consistent with our previous study. We assume that the same two-component model holds for the γ-ray band as for the radio band, and therefore,adopt the same relation between the core-dominance parameters and the γ-ray-photon indices for Fermi AGNs. Our fitting results indicate that the γ-ray emissions of Fermi blazars originate mainly from the jet, and therefore, we conclude that the Fermi blazars are beamed.

Comparison between Fermi detected and non-Fermi detected superluminal sources

Active galactic nuclei（AGNs） have been attracting research attention due to their special observable properties. Specifically,a majority of AGNs are detected by Fermi-LAT missions, but not by Fermi-LAT, which raises the question of weather any differences exist between the two. To answer this issue, we compile a sample of 291 superluminal AGNs（189 FDSs and 102 nonFDSs） from available multi-wavelength radio, optical, and X-ray（or even γ-ray） data and Doppler factors and proper motion（μ）(or apparent velocity(βapp)); calculated the apparent velocity from their proper motion, Lorentz factor（Γ）, viewing angle（?） and co-moving viewing angle(?co) for the sources with available Doppler factor（δ）; and performed some statistical analyses for both types. Our study indicated that（1） in terms of average values, FDSs have higher proper motions（μ）, apparent velocities(βapp),Doppler factor（δ）, Lorentz factor（Γ）, and smaller viewing angle（?）. Nevertheless, there is no clear difference in co-moving viewing angles（?∞）. The results reveal that FDSs show stronger beaming effect than non-FDSs.（2） In terms of correlations:1) both sources show positive, mutually correlated fluxes, which become closer in de-beamed fluxes; 2) with respect to apparent velocities and γ-ray luminosity, there is a tendency for the brighter sources to have higher velocities; 3) with regard to viewing angle and observed γ-ray luminosity, log? =-（0.23 ± 0.04）log Lγ+（11.14 ± 1.93）, while for the co-moving viewing angle and the intrinsic γ-ray luminosity, log?∞=（0.09 ± 0.01）log Lγn-（1.73 ± 0.48）. These correlations show that the luminous γ-ray sources have smaller viewing angles and a larger co-moving viewing angle, which indicate a stronger beaming effect in γ-ray emissions.

Efficient bright γ-ray vortex emission from a laser-illuminated light-fan-in-channel target

X/γ-rays have many potential applications in laboratory astrophysics and particle physics.Although several methods have been proposed for generating electron,positron,and X/γ-photon beams with angular momentum(AM),the generation of ultra-intense brilliant γ-rays is still challenging.Here,we present an all-optical scheme to generate a high-energy γ-photon beam with large beam angular momentum(BAM),small divergence,and high brilliance.In the first stage,a circularly polarized laser pulse with intensity of 10^(22) W/cm^(2) irradiates a micro-channel target,drags out electrons from the channel wall,and accelerates them to high energies via the longitudinal electric fields.During the process,the laser transfers its spin angular momentum(SAM)to the electrons’orbital angular momentum(OAM).In the second stage,the drive pulse is reflected by the attached fan-foil and a vortex laser pulse is thus formed.In the third stage,the energetic electrons collide head-on with the reflected vortex pulse and transfer their AM to the γ-photons via nonlinear Compton scattering.Three-dimensional particle-in-cell simulations show that the peak brilliance of the γ-ray beam is∼10^(22) photons·s^(-1)·mm^(-2)·mrad^(-2) per 0.1% bandwidth at 1 MeV with a peak instantaneous power of 25 TW and averaged BAM of 10^(6)h/photon.The AM conversion efficiency from laser to the γ-photons is unprecedentedly 0.67%.