Chinese Academy Of Engineering Physics Research Articles

General Design of Infrared Terahertz Free‑Electron Laser Facility of Chinese Academy of Engineering Physics

General Design of Infrared Terahertz Free‑Electron Laser Facility of Chinese Academy of Engineering Physics

Determination of the half-life of 184gRe and the isomeric ratio of 184m, gRe induced by D-T neutrons* *Supported by the National Natural Science Foundation of China (11975113)

The isomeric ratio of 184m, gRe and the half-life of 184gRe were measured in the 185Re (n, 2n) 184Re reaction at 14.8 MeV, and the uncertainty was discussed in detail. The measurements were performed using the activation method implemented for a rhenium sample using the K-400 neutron generator at the Chinese Academy of Engineering Physics (CAEP). Isomeric state and ground state nuclei of 184Re were identified by their γ-ray spectra. To eliminate the effect of the γ-ray emitted from the isomer on the counting of the ground state characteristic peaks, the isomeric ratio of 184m, gRe was calculated to be 0.29 ± 0.11 according to the neutron activation cross-section formula. This result is consistent with previous data within the uncertainty and can be used to determine parameters that characterize the dependence of the level density on the excitation energy and angular momentum. Through exponential function fitting and a detailed discussion of the uncertainty evaluation, the half-life of 184gRe was determined as 35.43 ± 0.16 d, which is consistent with the currently recommended value; however, the uncertainty assessment of the latter was barely documented. In addition, this study indicates that the half-life of the ground state can be obtained by eliminating the contamination of γ-rays emitted from the isomer, which provides the possibility of determining the half-lives of nuclides containing isomers.

Study on the Influence of Liner Structure on Jet Forming Driven by Electromagnetic Loading

A shaped charge liner driven by a strong electromagnetic field instead of explosives is a new way to form a jet. In this article, a new liner structure is performed, and a CQ-4 device of the Institute of Fluid Physics, Chinese Academy of Engineering Physics is used to load the liner. The jet forming and penetration power of conical liners under strong electromagnetic loading are tested and theoretically analyzed. Experimental results are in good agreement with the theoretical calculation. The results show that the 1- and 1.5-mm-thick liners have formed jets, but the liner with 2-mm wall thickness has failed to form an effective jet. And coming to the conclusion that under the loading conditions studied in this research, the jet velocity and penetration power decrease with the increase in the liner thickness. The liner structure is compared with Grace’s in his experiments and was found that it can improve the electromagnetic energy utilization rate, the peak current increasing by 9.6% and the jet tip velocity increasing by 8%. The influence of the cone angle of the liner on jet forming is also verified by a theoretical calculation taking into account the jet tip velocity, jet length, and the penetration power that increase with the decrease in cone angle.

Correction of coupled higher-order modes in the S-parameter characterization of wideband cavity beam position monitors.

Wideband RF cavity beam position monitors (CBPM) have been increasingly employed for short bunch interval operations in several linear accelerators. At a few nanoseconds of bunch spacing, the loaded quality factor of the CBPM TM110 dipole eigenmode is required to be sufficiently low to minimize the signal interference between consecutive bunches. Moreover, the bunched beam also couples to several unwanted higher-order modes (HOM), such as the TM210 and TE111 eigenmodes, which also may result in an error of the bunch position measurement if no precautions are taken. In the fabrication phase of CBPMs, the mode coupling can alter the TM110 mode frequency and therefore causes an error in its tuning, e.g., 0.3% for a 4.875GHz CBPM with QL = 22.5. This error needs to be identified so that the precise tuning is enabled since the dipole mode frequency becomes critical for the position evaluations as the signal processing is relatively phase-sensitive. This paper presents an approach to extract the pure unperturbed frequency of the dipole mode, not altered by the response to coupled HOMs. An analytic model based on the superposition law applied to electromagnetic fields has been developed to characterize the response of coupled HOMs in the S-parameter measurement. The model has been further verified with numerical simulation in the CST-Studio software by analyzing an approximate single-mode response CBPM. The correction method was applied on a wideband CBPM prototype for the pre-research plan of future high repetition rate hard XFEL at the Chinese Academy of Engineering Physics.

A digital system of acquisition and coincidence for SANS

We have developed multi-channel signal acquisition with a coincidence digital circuit for a two-dimensional detector array of the small-angle neutron scattering spectrometer (SANS) of the Institute of Nuclear Physical Chemistry at the Chinese Academy of Engineering Physics. This paper discusses how to determine such factors as the coincidence time window and program dead time according to the characteristics of the detector signal and how to correct the timer to realize the data coincidence. The whole system can support up to 192 analog channels connected to a fast analog-to-digital converter, supporting speeds of 50 MSPS for each channel managed by a field-programmable gate array (FPGA). The internal clock of the FPGA is 50 MHz and the time accuracy is 20 ns. Preliminary experiments are carried out and the results are presented and discussed. The whole design can fully meet the needs of the spectrometer.

A method of bunch by bunch measurement at nanoseconds interval by using cavity beam position monitors

The application of RF cavity beam position monitors (CBPM) is essential for precise beam position measurements in X-ray Free-Electron Lasers (XFEL) and linear colliders. This paper addresses the solution to the inter-bunch signal interference when the bunch separation is as short as nanoseconds. The signals can overlap from bunch to bunch, which can induce appreciable error in evaluating beam position. We propose a conceptual method to eliminate the dominant signal overlap under a quadrature phase offset condition. Using this method, the elimination automatically occurs in the process of signal digitalization. The dominant interference that is contributed by the last bunch can be reduced over an order of magnitude in a conventional CBPM system. In addition, the required bandwidth can be effectively reduced by a factor of 2, and the design challenge for a wideband CBPM is relaxed. The method was demonstrated in an analytic approach by simulating the signal evolution in the RF front end of electronics built in MATLAB code. In the practical concern of applying this method, the factors that perturb the elimination have been examined as well. Based on the numerical result, the CBPM prototype has been designed for the pre-research plan of future high repetition rate hard XFEL at Chinese Academy of Engineering Physics. The combined simulations in CST and MATLAB on the CBPM prototype indicate agreement with the result obtained in the analytic approach.

Activation cross-sections for the 185Re(n, 2n) reaction and the isomeric cross-section ratio of 184m,gRe in the neutron energy range of 13\u201315 MeV

.Cross-sections and their isomeric ratios ( sigma_{mathrm{m}}/sigma_{mathrm{g}}) for the 185Re(n, 2n)184mRe and 185Re(n, 2n)184gRe reactions in the 13–15 MeV range were measured. The neutron activation technique was applied using the K-400 neutron generator at the Chinese Academy of Engineering Physics (CAEP). Natural Re samples and Nb monitor foils were activated jointly to determine the reaction cross-section and the incident neutron flux. The 3H(d, n)4He reaction was used to generate the neutron beam. The pure cross-section of the ground state was derived from the absolute cross-section of the metastable state using residual nuclear decay analysis. Numerical calculations using the nuclear-model-based computer code TALYS-1.8 with six level density models were used to obtain 185Re(n, 2n)184m, gRe reaction excitation functions and their isomeric cross-section ratios. Finally, experimentally determined cross-sections were compared with corresponding literature data.

Chinese Academy of Engineering Physics – Creator of Chinese Nuclear Weapons

Chinese Academy of Engineering Physics – Creator of Chinese Nuclear Weapons

Recent Progress of Residual Stress Distribution and Structural Evolution in Materials and Components by Neutron Diffraction Measurement at RSND

Neutron diffraction is an effective and nondestructive method to investigate inner structure and stress distribution inside bulk materials and components. Compared with X-ray diffraction, neutron diffraction allows a relatively high penetration depth and covers a larger gauge volume, enabling it to measure the lattice structure and three-dimensional (3D) distribution of residual stress deep inside thick sample materials. This paper presents the recent development of a Residual Stress Neutron Diffractometer (RSND) at the Key Laboratory for Neutron Physics of the Chinese Academy of Engineering Physics, Institute of Nuclear Physics and Chemistry, Mianyang, China. By integrating multiple instruments such as a loading frame, Kappa goniometer, and coupling system, the RSND was constructed as a suitable platform for various neutron diffraction experiments, including residual stress measurement, in situ observation, and texture analysis. Neutron diffraction measurement can be used to study various materials such as steels, aluminum alloys, and titanium alloys, as well as various components such as turbine discs and welding parts. An evaluation method for both polycrystalline and monocrystalline materials was developed, and this method was found to have the capability of solving an agelong technical challenge in characterizing monocrystalline materials. Furthermore, by introducing a texture and thermomechanical coupling system, it is now possible to make effective in situ observations of the structural evolution in single crystal materials under high-temperature tensile conditions.

Isomer ratios and cross sections for the isomeric pair 122mSb and 122gSb in the 123Sb(n,2n) reaction

Cross-sections and their isomeric ratios σm/σg in the energy range of 13–15 MeV for isomeric pair 122mSb and 122gSb produced by the 123Sb(n,2n) reaction have been measured by activation and off-line γ-ray spectrometric technique using the K-400 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). Specifically, the versatile stacked foil irradiation technique and a high resolution HPGe detector were employed. The 3H(d,n)4He reaction was used to produce the neutron beam. Partial cross sections σm and σg were derived from the absolute cross section of the metastable state and residual nuclear decay analysis. The 123Sb(n,2 n)122m,gSb reaction excitation functions and their isomeric cross section ratios were numerically calculated with TALYS-1.8 code with different level density options. Results are discussed and compared with corresponding literature data.

Measurement of cross sections and isomeric cross-section ratios for the (n,2n) reactions on 85,87Rb in energies between 13 and 15 MeV

Abstract The (n,2n) cross sections and their isomeric cross-section ratios (σm/σg) in the neutron energy range 13–15 MeV have been measured for 85,87Rb by an activation and off-line γ-ray spectrometric technique using the Pd-300 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The natural Rb samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The neutrons were produced via the 3H(d,n)4He reaction. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The 85Rb(n,2n)84m,gRb and 87Rb(n,2n)86m,gRb reaction excitation functions and their isomeric cross-section ratios were also calculated theoretically using the TALYS-1.8 code with different level density options. Results are discussed and compared with the corresponding literature data.

Activation cross section and isomeric cross section ratio for the 76Ge(n,2n)75m,gGe process

.We measured neutron-induced reaction cross sections for the 76Ge(n,2n)75m,gGe reactions and their isomeric cross section ratios sigma_{m}/sigma_{g} at three neutron energies between 13 and 15MeV by an activation and off-line gamma-ray spectrometric technique using the K-400 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). Ge samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The monoenergetic neutron beams were formed via the 3H(d,n)4He reaction. The pure cross section of the ground state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The cross sections were also calculated using the nuclear model code TALYS-1.8 with different level density options at neutron energies varying from the reaction threshold to 20MeV. Results are discussed and compared with the corresponding literature data.

Activation cross sections for the 110Pd(n,2n) reaction and the isomeric cross-sections ratio of 109m,gPd in the neutron energy range of 13–15 MeV

The 110Pd(n,2n)109m,gPd reaction cross-sections and the isomeric cross section ratios (σm/σg) in the neutron energy range of 13-15 MeV have been measured by an activation and off-line g-ray spectrometric technique using the 300Pd Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The natural Pd samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The neutron beams were generated via the 3H(d,n)4He reaction. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The 110Pd(n,2n)109m,gPd reaction excitation functions and their isomeric cross section ratios were also calculated theoretically using the computer code TALYS-1.8 with different level density options. Results are discussed and compared with the corresponding literature data.

Structural and size evolution of indium nanoparticles embedded in aluminum synthesized by ion implantation**Project supported by the National Natural Science Foundation of China (Grant No. 11505160) and the Director Foundation of Institute of Materials, Chinese Academy of Engineering Physics (Grant No. SJZD201406).

The structural and the size evolution of embedded In nanoparticles in Al synthesized by ion implantation and subsequent annealing are experimentally investigated. The average radius r of In nanoparticles is determined as a function of annealing time in a temperature range between 423 K and 453 K. The structural transition of In nanoparticles with the crystallographic orientation In (200)[002] Al (200)[002] is observed to change into In (111)[110] Al (002)[110] with a critical particle radius between 2.3 nm and 2.6 nm. In addition, the growth of In nanoparticles in the annealing process is evidently governed by the diffusion limited Ostwald ripening. By further analyzing the experimental data, values of diffusion coefficient and activation energy are obtained.

Activation cross section and isomeric cross section ratios for the ( n,2n ) reaction on Eu153

The $^{153}\mathrm{Eu}(n,2n)^{152}\mathrm{Eu}^{\mathrm{m}1,\mathrm{m}2,g}$ cross section was measured by means of the activation technique at three neutron energies in the range 13--15 MeV. The quasimonoenergetic neutron beam was formed via the $^{3}\mathrm{H}(d,n)^{4}\mathrm{He}$ reaction, in the Pd-300 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The activities induced in the reaction products were measured using high-resolution \ensuremath{\gamma}-ray spectroscopy. The cross section of the population of the second high-spin (${8}^{\ensuremath{-}}$) isomeric state was measured along with the reaction cross section populating both the ground (${3}^{\ensuremath{-}}$) and the first isomeric state (${0}^{\ensuremath{-}}$). Cross sections were also evaluated theoretically using the numerical code TALYS-1.8, with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

Activation Cross Section and Isomeric Cross-Section Ratio for the (n,2n) Reaction on 113,115In

Cross sections of the 113In(n,2n)112m,gIn and 115In(n,2n)114m,gIn reactions and their isomeric cross-section ratios σm/σg have been measured by means of the activation technique at three neutron energies in the range 13 to 15 MeV. Indium samples and niobium monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The monoenergetic neutron beam was produced via the 3H(d,n)4He reaction at the Pd-300 Neutron Generator of the Chinese Academy of Engineering Physics. The activities induced in the reaction products were measured using high-resolution gamma-ray spectroscopy. The pure cross section of the ground state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. Cross sections were also evaluated theoretically using the numerical nuclear model code TALYS-1.8 with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

Activation cross section and isomeric cross-section ratio for the (n,2n) reaction on 132,134Ba

Abstract Cross sections of the 132Ba(n,2n)131m,gBa and 134Ba(n,2n)133m,gBa reactions and their isomeric cross section ratios σm/σg have been measured by means of the activation technique at three neutron energies in the range 13−15 MeV. BaCO3 samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The quasimonoenergetic neutrons beam were produced via the 3H(d,n)4He reaction at the Pd-300 Neutron Generator of the Chinese Academy of Engineering Physics (CAEP). The activities induced in the reaction products were measured using high−resolution γ ray spectroscopy. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. Cross sections were also evaluated theoretically using the numerical nuclear model code, TALYS-1.8 with different level density options at neutron energies varying from the reaction threshold to 20 MeV. Results are discussed and compared with the corresponding literature.

Influence of secondary treatment with CO2 laser irradiation for mitigation site on fused silica surface**Project supported by the National Natural Science Foundation of China (Grant Nos. 61505170, 61505171, and 51535003), the Joint Fund of the National Natural Science Foundation of China, the Chinese Academy of Engineering Physics (Grant No. U1530109), and the China Postdoctoral Science Foundation (Grant No. 2016M592709).

The ablation debris and raised rim, as well as residual stress and deep crater will be formed during the mitigation of damage site with a CO2 laser irradiation on fused silica surface, which greatly affects the laser damage resistance of optics. In this study, the experimental study combined with numerical simulation is utilized to investigate the effect of the secondary treatment on a mitigated site by CO2 laser irradiation. The results indicate that the ablation debris and the raised rim can be completely eliminated and the depth of crater can be reduced. Notable results show that the residual stress of the mitigation site after treatment will reduce two-thirds of the original stress. Finally, the elimination and the controlling mechanism of secondary treatment on the debris and raised rim, as well as the reasons for changing the profile and stress are analyzed. The results can provide a reference for the optimization treatment of mitigation sites by CO2 laser secondary treatment.

Design of a 5-MA 100-ns linear-transformer-driver accelerator for wire array Z-pinch experiments

The linear-transformer-driver (LTD) is a recently developed pulsed-power technology that shows great promise for a number of applications. These include a $Z$-pinch-driven fission-fusion-hybrid reactor that is being developed by the Chinese Academy of Engineering Physics. In support of the reactor development effort, we are planning to build an LTD-based accelerator that is optimized for driving wire-array $Z$-pinch loads. The accelerator comprises six modules in parallel, each of which has eight series 0.8-MA LTD cavities in a voltage-adder configuration. Vacuum transmission lines are used from the interior of the adder to the central vacuum chamber where the load is placed. Thus the traditional stack-flashover problem is eliminated. The machine is 3.2 m tall and 12 m in outer diameter including supports. A prototype cavity was built and tested for more than 6000 shots intermittently at a repetition rate of 0.1 Hz. A novel trigger, in which only one input trigger pulse is needed by utilizing an internal trigger brick, was developed and successfully verified in these shots. A full circuit modeling was conducted for the accelerator. The simulation result shows that a current pulse rising to 5.2 MA in 91 ns (10%--90%) can be delivered to the wire-array load, which is 1.5 cm in height, 1.2 cm in initial radius, and 1 mg in mass. The maximum implosion velocity of the load is $32\text{ }\text{ }\mathrm{cm}/\ensuremath{\mu}\mathrm{s}$ when compressed to 0.1 of the initial radius. The maximum kinetic energy is 78 kJ, which is 11.7% of the electric energy stored in the capacitors. This accelerator is supposed to enable a radiation energy efficiency of 20%--30%, providing a high efficient facility for research on the fast $Z$ pinch and technologies for repetition-rate-operated accelerators.

Stark-Broadened Profiles of the Spectral Line Pα in He II Ions**Supported by the National Natural Science Foundation of China under Grant Nos 11275029 and 11204017, and the Foundation for the Development of Science and Technology of Chinese Academy of Engineering Physics under Grant Nos 2013A0102005 and 2014A0102005.

We report a systematic method to perform calculations of spectral line broadening parameters in plasmas. This method is applied to calculate Stark-broadening line profiles of Pα (n = 4 → n = 3) transitions under certain specific plasma conditions, by treating this case as an example. In the framework of the fully relativistic Dirac R-matrix theory, we calculate the electron-impact broadening operators, which are assumed to be diagonal matrix to simplify the situation. The electric microfield distribution function is calculated by retaining Hooper's formalism. The dipole matrix elements and atomic structure parameters used in these calculations have been obtained from atomic structure GRASP code. Based on this required data, we calculate the Stark-broadened line profiles of the Paschen spectral lines in He II ions in a systematic manner. Overall, there is a very good agreement between our calculated Stark-broadened line profiles and other line broadening numerical simulation codes (SimU and MELS). Our reported spectral line-broadening data have real applications in plasma spectroscopy, plasma diagnosis and also play a fundamental role in plasma modeling.