This study investigates the prompt radiation field in the accelerator-target reactor coupling region of the China initiative Accelerator-Driven System (CiADS). This coupling region, which is comprised of the subcritical reactor, the radiation shielding room, and the bending magnet room, features a complex, multisource radiation environment arising from fission radiation, spallation radiation, and beam loss radiation. To accurately model this scenario, a hybrid PHITS-MCPL-FLUKA computational approach was developed, enabling the detailed analysis of the source contributions, energy spectra, radiation field spatial distributions, and shielding. The results reveal that the spallation neutrons are the principal contributors to the biological shielding requirements of the subcritical reactor, while beam loss radiation is the primary consideration for the shielding design of the side walls in the radiation shielding room. Moreover, localized shielding applied to the reactor cover can effectively mitigate radiation hazards to certain reactor equipment. This comprehensive evaluation of the radiation characteristics and shielding strategies provides critical guidance for optimizing the radiation protection design, enhancing operational safety, and supporting the long-term stable operation of CiADS.

Understanding evaporation behavior of lead-bismuth eutectic (LBE) is essential for the operation and maintenance of nuclear installations with liquid LBE as coolant or spallation target. In the present study, the nonequilibrium evaporation behavior of LBE has been investigated in the temperature range of 473-673 K in Ar/ 5%H2 atmosphere using transpiration method. An experimental apparatus with a cylindrical containment severing as LBE evaporation pot has been built to simulate the actual operational situations for a nuclear research facility. The concentrations of bismuth and LBE vapors in carrier gas were determined under non-equilibrium conditions. The observed LBE concentration is in the range of 10_6 and 10_ 5 mol/m3 and the corresponding bismuth-to-lead mass ratio of LBE vapor is less than 4% in most of the experiments. Compared to the predicted saturation vapor pressures based on OECD Nuclear Energy Agency (NEA) recommended method, the observed vapor pressures are several orders of magnitude higher. This suggests that extreme cautions should be given when saturated vapor pressure at equilibrium is applied to actual operational scenarios for nuclear facilities operating under non-equilibrium and low temperature conditions. The results obtained in this study provide foundational data for the safe operation of China initiative Accelerator Driven System (CiADS) in the future.

The design, construction, and commissioning of a novel liquid helium-free (LHe-free) Nb3Sn superconducting radio frequency (SRF) electron accelerator at the Institute of Modern Physics of the Chinese Academy of Sciences (IMP, CAS) will be presented. A 650 MHz 5-cell elliptical cavity was coated using the tin vapor diffusion method for electron beam acceleration. The cavity was slowly cooled down across 18 K with the high-precision collaborative control of ten individual GM cryocoolers. This process was accompanied by the characteristic magnetic flux expulsion of Nb3Sn films. Horizontal tests of the LHe-free cryomodule show stable operation in both continuous wave (CW) and pulse modes, with maximum peak electric fields (Epk) of 6.02 and 14.90 MV m(-1), respectively. The Nb3Sn SRF electron accelerator achieved stable beam acceleration, reaching a maximum energy of 4.6 MeV with an average macropulse beam current exceeding 100 mA. Additionally, stable electron beam acceleration was achieved for the first time at a cavity temperature of 10 K. This pioneering achievement demonstrates a principal validation for the feasibility of applying Nb3Sn thin film SRF cavities in both large-scale scientific facilities and compact industrial accelerators. It also opens up possibilities for further upgrades in operating temperature, cooling methods, and refrigeration equipment for SRF accelerators.

An Extended-range Bonner sphere spectrometer (EBSS) has been developed to investigate the neutron spectra of the China initiative Accelerator Driven System. This paper presents the design, calibration, and validation measurements of the EBSS system using a standard 241Am-Be neutron source and the cosmic ray neutrons. The EBSS system was simulated using the PHITS code, and the geometric structures were designed using the response functions obtained by simulations. The EBSS system comprises of seven polyethylene-only spheres and seven extended-range spheres encased in lead, copper, or tungsten shells along with a bare 3He proportional counter. To verify the accuracy of the simulated response functions, the EBSS system was calibrated with monoenergetic neutron beams of 565 keV at the China Institute of Atomic Energy in Beijing. The EBSS system was used to measure neutron count rates of the 241Am-Be neutron source and cosmic ray neutrons. Subsequently, the measured neutron count rates were converted into neutron spectra by the unfolding software. Experimental findings demonstrate the precise capability of the EBSS system to measure neutron spectra across a wide range of neutron radiation fields.

In this paper, K-shell X-ray spectra of nitrogen are measured by the interaction of Nq+ (q = 3, 5) ions with Al and Cu surfaces in the impact energy range of 25–100 keV. K-shell X-ray yields per incident ion and then ionization cross sections are deduced from the measured K-X-ray spectra. It is found that both the yields and cross sections increase quickly with increasing impact energy, but have no apparent dependence on the target material and the charge state of the incident ion. The experimental results reveal that the incident Nq+ (q = 3, 5) ions have been neutralized and achieved a charge-state equilibration before the K-shell electron is ionized. The experimental ionization cross sections are compared with those from the plane wave Born approximation (PWBA) and the classical binary encounter approximation (BEA) theory. The BEA calculations are better consistent with the experimental data than the PWBA. It means that the K-shell ionization of the incident Nq+ (q = 3, 5) ions is due to the direct Coulomb excitation processes that occurred below the target surface. K-shell ionization cross sections of Nq+ ions incident on an Al target. The theoretical calculations of BEA and PWBA models are also shown for comparison

The spectra emitted by highly charged ions, which are abundant in laboratory plasma and stellar systems, cover a wide range of wavelengths from near-infrared to x-rays. Measurements on such spectral lines can provide plasma information such as the electron temperature, electron/ion density, chemical composition, and the evolution of these parameters. To simulate the x-ray emission from comets and other celestial bodies irradiated by solar wind ions in the laboratory, we established an experimental platform for x-ray measurements at Institute of Modern Physics, Chinese Academy of Sciences, and measured the x-ray emission spectra from a series of metal and silicate minerals bombarded by slow highly charged nitrogen and oxygen ions. In this paper, we describe the x-ray measurement platform in detail and report the x-ray emission caused by the interaction of 1.5–20 keV/q Oq+ (q = 3, 5, 6) and Nq+ (q = 3, 5) ions with nickel surface. It is discovered that the measured x-ray yield and production cross section increase rapidly as increasing the impact energy, but have no discernible dependence on the charge state of incident ions. The experimental results reveal that the incident ions have been neutralized and achieved charge state equilibration before the K-shell electron is ionized. When the incident energy is greater than 5 keV/q, the Binary Encounter Approximation calculations are consistent well with the experimental data, indicating that the K-shell ionization of incident ions is due to direct Coulomb excitation processes that occur below the target surface. However, the experimental ionization cross sections clearly deviate from the Binary Encounter Approximation calculations when the impact energy is less than 5 keV/q. The discrepancy at the low collision energy is discussed and explained based on a multi-electron excitation model.

We report on the K X-ray emission for 9–140 keV oxygen ions with initial charge states from 3 to 7 approaching a copper surface. The peak center of the measured X-ray spectrum slightly shifts towards higher energies with the increasing of the initial charge state of the incident ions. For the collisions of oxygen ions with no K-vacancies (q = 3–6), the X-ray yield per incident ion increases gradually with the projectile’s kinetic energy, while for the O7+ ions (with a K-vacancy) it is nearly independent of the energy. The K-shell ionization cross-sections for the oxygen ions with no K-vacancies obtained from the experiments are well consistent with the calculations of the binary encounter approximation model when the collision energy is larger than 30 keV, whereas they are several times larger than the theoretical values at collision energies of less than 30 keV.

Lead-bismuth eutectic(LBE) is the candidate material of spallation target for China initiative Accelerator Driven System(CiADS). Long-term irradiation makes the LBE highly radioactive. Most of the spallation target radionuclide studies focused on the effects of the proton beam and ignored fission neut-rons from the reactor. In this paper, both the fission neutrons and the high-energy protons have been taken into account in the radionuclide calculations of LBE and spallation target structural parts by coup-ling codes FLUKA and MCNP. Contributions from the fission neutron and the high-energy proton have been compared in the aspects of the activity, main radionuclides, toxicity, and the decay photon of radio-active products. The main shell, guide tube, and beam tube are significantly affected by the fission neut-ron activation. When the reactor tends to be critical, the fission neutron-induced LBE target activations are even greater than that induced by the proton beam. In the LBE itself, 96.66％ of 210Po is induced by the fission neutrons. These results illustrate that fission neutrons are also essential for the radionuclides calculation of LBE and its structural parts. In addition, this study provides reference data for the radi-ation protection of CiADS and a more accurate method for the radionuclides study of the spallation tar-get in ADS systems.

The interaction of highly charged ions with solid surfaces is a very complex multi-body process. When the ions are close to the solid surfaces, the potential energy of the ions will be deposited in a tiny area of the target surfaces in a short time and then emitting X rays, which has important scientific significance and application in Astrophysics and plasma diagnosis. For experiments on the interaction of highly charged ions with surfaces, not only the X-ray energy spectrum but also the X-ray yield should be measured accurately. The precise measurement of the X-ray yield depends on the ability to accurately measure the beam-current intensity. In the past, the beam-current intensity was acquired by measuring the target current. Since the interaction between highly charged ions and solids involves the emission of secondary electrons, the actual measured target current is the sum of the initial beam-current intensity and the intensity caused by the secondary electrons, resulting in inaccurate X-ray yield calculations. In this experiment, a new analytical device, beam-current density meter, has been designed, which can measure the beam-current intensity with an accuracy of 0.1 nA. By measuring the current on the density meter instead of the target current, the influence of secondary electrons is almost avoided, and a more accurate X-ray yield is obtained.This paper reports the characteristic X-ray spectra of oxygen atoms emitted from the interaction of 1.5–20 keV/q highly charged \begin{document}${\rm{O}} ^{q+} $\end{document} ions with aluminum surfaces. For the X rays emitted by \begin{document}$ {\rm{O}}^{q+} $\end{document}(q = 3, 5, 6) ions, the experimental results show that it is due to the close collisions with aluminum atoms after entering the surfaces, while the X rays emitted by \begin{document}${\rm{O}} ^{7+} $\end{document} ions mainly come from the decay of hollow atoms. Under the condition of equal kinetic energy, the X-ray yield of \begin{document}${\rm{O}} ^{7+} $\end{document} ions with K-shell vacancy is about one order of magnitude higher than that of \begin{document}$ {\rm{O}}^{q+} $\end{document}(q = 3, 5, 6) ions, and X-ray yield of \begin{document}$ {\rm{O}}^{6+} $\end{document} ions without K-shell vacancy is also significantly higher than that of \begin{document}${\rm{O}} ^{3+} $\end{document} and \begin{document}$ {\rm{O}}^{5+} $\end{document} ions. Generally, the X-ray yield and ionization cross-section is associated with the initial electron configuration of incident ions, and increases with the growth of ions kinetic energy. Based on the semi-classical approximation theory of binary collision, we have estimated the kinetic energy threshold for the emission of the Kα-X rays of \begin{document}$ {\rm{O}}^{q+} $\end{document}(q = 3, 5, 6) ions as interacting with the aluminum target. As the incident kinetic energy is lower than the kinetic energy threshold, for \begin{document}${\rm{O}} ^{6+} $\end{document} ions interacting with the sample, there may have a multi-electron excitation process that induces this K-electron ionization of the incident ions.

BackgroundThe highly charged nitrogen ions (Nq+, q=3, 5, 6) are one of the main charged ions in the solar wind. Study of K-shell X-ray emissions in collisions of Nq+ (q=3, 5, 6) ions with a Cu surface is of great significance for understanding the de-excitation process of "hollow atoms" and the generation mechanism of comet X-rays.PurposeThis study aims to investigate characteristics of K-shell X-ray emission in impacts of Nq+ (q=3, 5, 6) ions with a Cu surface.MethodsThe Nq+ (q=3, 5, 6) ion beam was generated by the electron cyclotron resonance ion source (ECRIS) in Institute of Modern Physics, Chinese Academy of Sciences. The K-shell X-ray spectra resulted from collisions of the Nq+ ions with the Cu surface were acquired by a silicon drift detector (SDD). Based on the X-ray spectra, K-shell X-ray yields and ionization cross sections were calculated.ResultsThe results show that, for the Nq+ (q=3, 5) ion incidence, K-shell X-ray emissions are attributed to close collisions of the ions with Cu atoms on the subsurface of the target, and that the K-shell X-ray yields and ionization cross sections increase monotonically with the increase of kinetic energy of the incident ions. For the N6+ ion incidence, the K-shell X-ray yields have no obvious dependence on kinetic energy of the incident ions. The K-shell X-rays are primarily emitted from the above-surface of Cu target through the de-exciting of the formed "hollow N atoms", and they account for about 97% of the total X-rays. In addition, the X-ray yield of the N5+ ion incidence is higher than that of N3+ ions.ConclusionsThis study provides basic data for the understanding the de-excitation process of "hollow atoms" and the generation mechanism of comet X-rays.

The first Radioactive Ion Beam Line in Lanzhou was a projectile fragment separator located in the HIRFL. The process of production and separation of radioactive ion beams can induce a strong and complex radiation field. The neutron dose equivalent rates were measured in four positions with a 70 MeV/u 40Ar18+ beam. The results were compared with that simulated by the FLUKA code. New shielding walls were installed to reduce the neutron background for spectroscopy measurement in the experimental terminal. In addition, the induced radioactivity of accelerator components and corresponding residual dose rates were analyzed for the radiation safety of accelerator workers. The airborne radioactivity as well as occupational exposure due to immersion in and inhalation of activated air were also estimated. This work aims to provide a valuable experience for the radiation study in the future fragment separator HFRS at HIAF.

The irradiation resistance capability of structural components in nuclear reactors has a great influence on the system's service life and safety. In this work, the CiADS coupling model between spallation target and subcritical reactor is established by MCNPx2.70, and the atomic dissociation cross sections for CiADS candidate materials are processed by the nuclear data processing software NJOY2016. The irradiation damages for three kinds of stainless steels, 316L, 15-15Ti, SIMP and one kind of ZTA ceramics are calculated and analyzed under three conditions with the number of fuel assemblies of 30, 42 and 72, respectively. When used as CiADS fuel cladding, SIMP steel has the lowest rate of irradiation damage among the three candidate steels. The calculated irradiation damage rate are 1.16, 1.61 and 12.0 dpa/a when the number of fuel assemblies are 30, 42 and 72, respectively. The irradiation damage rate for the fuel cladding made of ZTA materials is much higher than that of the candidate steels. The CiADS center tube suffers the strongest neutron irradiation for the portion near the reaction area between the accelerator beam and the spallation target. The maximum irradiation damage rate is about 2.7 dpa/a for the center tube made of 316L steel when the fuel assemblies are 30.

To guarantee the radiation safety of heavy ion medical machine(HIMM)dur-ing operation,the prompt neutron source term was calculated with the FLUKA code,and the effects of secondary neutron and gamma radiation on shielding were analyzed.The semi-empirical formula and FLUKA code were adopted to calculate the shielding thickness,and the shielding design of HIMM treatment room was given.At the condi-tion of full power operation of HIMM,the measured neutron dose rate is in agreement with the simulation result.The results indicate that the calculation method is reasona-ble,and the result is in accordance with the requirements of the national standard.

强流重离子加速器(HIAF)是中国科学院近代物理研究所自主研制的一台高能强流重离子加速器,它可以实现p到U的全离子加速.为了保证HIAF运行时的辐射安全,针对该装置的增强器(BRing)及高能外靶实验终端,利用蒙特卡洛程序FLUKA及外推法计算得到了加速p,C及U三种离子时所需的辐射屏蔽.结果表明,加速质子时所需屏蔽厚度最大,并以此为依据给出了全地下结构的屏蔽设计.在此基础上,提出了一种估算高能质子/重离子加速器束流均匀损失时横向屏蔽厚度的方法.结果显示,估算结果与FLUKA计算结果符合较好,验证了该方法的有效性和准确性.

In this work, the radiation environment in the target area of a fragment separator is evaluated using FLUKA code. The energy deposition in quadrupole coils is presented to provide guidance for a radiation-resistant magnets design. Results show that neutrons dominate in the prompt radiation field. A compact shielding design is recommended for high radiation areas along with the minimization of air activation in the tunnel in order to minimize the radiation effect on nearby beam lines. The displacements per atom results for the graphite target and copper coils indicate that the effect is insignificant. In addition, the activation level of the target is estimated for workers under possible hands-on maintenance condition.

本工作是基于蒙特卡罗模拟软件FLUKA对高能强流重离子加速器(HIAF)高能辐照终端感生放射性进行初步研究.该终端可运行质子最高能量为9.3 GeV,最大流强是1.45×1012 pps(particle per second).研究内容包括:(1)预测高能辐照终端内活化物质的放射性活度特性;(2)预测不同冷却时间高能辐照终端内残余剂量率分布.研究结果表明,HIAF正常运行时高能辐照终端内的感生放射性主要受束流垃圾桶活化产生的放射性核素影响.当加速器连续运行100天冷却4小时,垃圾桶表面残余剂量率为2.375 mSv·h?1.终端内空气中13 N和15 O动态饱和比浓度大于其对应的导出空气浓度.冷却水中13 N和15 O的活度大于对应的ALImin.该研究是HIAF辐射防护基础研究以及加速器环境影响评价的一项重要内容.

The China initiative Accelerator Driven System (CiADS) is the first integrated ADS facility designed to study the safety disposal of nuclear waste.As a nuclear facility,it will cause radiological impact on the environment.Therefore,the assessment of radiological impact on the environment around this facility will not only meaningful to the public health,but also offers significant guides to the shielding design of CiADS.Pebble samplings were collected around the campus of the Heavy Ion Research Facility in Lanzhou (HIRFL) and irradiated by a 241Am-Be neutron source.Based on the γ-spectrum measured by a HPGe detector before and after the neutron irradiation,the specific activities of induced radionuclides 24Na,54Mn,56Mn and 27Mg in these samples were analyzed and compared with the Monte-Carlo simulation values obtained with the Geant4 toolkit.The comparison between the experimental and simulated results indicates that Geant4 toolkit is feasible for radiation impact assessment of nuclear facilities,such as CiADS.Then the neutron spectrum outside the concrete shielding of HEBT tunnel of the CiADS have been simulated by the Geant4 toolkit,and the saturation activities of the induced nuclides in the first 10 cm pebble layer have been predicted.The results show that the saturation activities of induced radionuclides in pebbles outside the CiADS shielding are much lower than their exemption values and their radiation impacts to the environment could be ignored.

Measurement of the neutron yield is performed at a primary energy of 400 MeV/u carbons for the Pb target.Water-bath activation-foil method is used in a moderation measurement with Au foils to detect the moderated neutrons. The neutron yield is determined to be 18.4±2.1 per carbon by integrating the neutron flux over the entire water volume. The corresponding simulation values are performed by Geant4 code with three models to compare with the experimental results. The comparison shows that the calculated result with the INCL model is in good agreement with the experimental data.

As one of the key components of Sector Focusing Cyclotron at the Institute of Modern Physics, Chinese Academy of Sciences, the electrostatic deflector can be activated by primary and secondary particles, because of a mismatch between the actual value and the design value of the emittance and emergence angle. In addition, it will be struck by more particles, since there is a stray magnetic field and outgas from the surface of the electrostatic deflector. The residual radioactivity in the electrostatic deflector has been studied in two aspects: specific activity and residual dose rate, based on the gamma-ray spectrometry and Fluke 451p ionization chamber, respectively. The specific activity of radionuclides in the main components and the dust on the enclosure have been investigated by using gamma-ray spectrometry. The residual dose rate around the electrostatic deflector has been obtained by Fluke 451p ionization chamber. The results of the study show that there is a non-negligible radiological risk to the staff. This result can be provided as guidance for making a maintenance schedule, so that the dose received by staff can be kept as low as reasonably achievable. Based on the results, advice for "hands-on" maintenance and decommissioning of the SFC have been provided.

As one of the key com po nents of Sec tor Fo cus ing Cy clo tron at the In sti tute of Mod ern Phys ics, Chi nese Acad emy of Sci ences, the elec tro static de flec tor can be ac ti vated by pri mary and sec ond ary par ti cles, be cause of a mis match be tween the ac tual value and the de sign value of the emit tance and emer gence an gle. In ad di tion, it will be struck by more par ti cles, since there is a stray mag netic field and outgas from the sur face of the elec tro static de flec tor. The re sid ual ra dio ac tiv ity in the elec tro static de flec tor has been stud ied in two as pects: spe cific ac tiv ity and re sid ual dose rate, based on the gamma-ray spec trom e try and Fluke 451p ion iza tion cham ber, re spec tively. The spe cific ac tiv ity of radionuclides in the main com po nents and the dust on the en clo sure have been in ves ti gated by us ing gamma-ray spec trom e try. The re sid ual dose rate around the elec tro static de flec tor has been ob tained by Fluke 451p ion iza tion cham ber. The re sults of the study show that there is a non-neg li gi ble ra dio log i cal risk to the staff. This re sult can be pro vided as guid ance for mak ing a main te nance sched ule, so that the dose re ceived by staff can be kept as low as rea son ably achiev able. Based on the re sults, ad vice for "hands-on" main te nance and de com mis sion ing of the SFC have been pro vided.