Besides the original seeded undulator line, in the soft X-ray free-electron laser (SXFEL) user facility in Shanghai, a second undulator line based on self-amplified spontaneous emission is proposed to achieve 2 nm laser pulse with extremely high brightness. In this paper, the beam energy deviation induced by the undulator wakefields is numerically calculated, and 3D and 2D results agree well with each other. The beam energy loss along the undulator degrades the expected FEL output performances, i.e., the pulse energy, radiation power and spectrum, which can be compensated with a proper taper in the undulator. Using the planned time-resolved diagnostic, a novel experiment is proposed to measure the SXFEL longitudinal wakefields.

The bunch length can be measured by comparison of two frequency components of a synchrotron beam signal. An online bunch length measurement system has been implemented based on this method. Working frequencies of 3 GHz and 500 MHz were selected, and the raw data was acquired by digital oscilloscope and was resampled and analyzed using the MATLAB software platform at bunch-by-bunch rate. The constructed system was employed to study the bunch length synchronous oscillation phenomenon during injection. The beam experiments demonstrated a time resolution of less than 0.5 ps.

Direct Monte Carlo (MC) simulation is a powerful probabilistic safety assessment (PSA) method for accounting dynamics of the system. But it is not efficient at simulating rare events. A biasing transition rate method based on direct MC simulation is proposed to solve the problem in this paper. This method biases transition rates of the components by adding virtual components to them in series to increase the occurrence probability of the rare event, hence the decrease of the variance of MC estimator. Several cases are used to benchmark this method. The results show that the method is effective at modeling system failure and is more efficient at collecting evidence of rare events than the direct MC simulation. The performance is greatly improved by the biasing transition rate method.

Amidoxime-functionalized ultra-high molecular weight polyethylene fibers (UHMWPEF-AO) were used to absorb uranium [U(VI)] from acqeous solutions. In this paper, we study effects of pH, initial U(VI) concentration, contact time, and temperature on U(VI) adsorption by UHMWPEF-AO. The adsorption process agrees well with pseudo-second-order and Langmuir model. UHMWPEF-AO exhibits excellent adsorptive performance for U(VI) with a maximum adsorption capacity of 176.12 mg/g at pH 4 and 298 K. The structures of UHMWPEF-AO and U(VI) loaded UHMWPEF-AO are characterized by FT-IR and nano-CT. U(VI) loaded UHMWPEF-AO is sintered after adsorption process to recycle absorbed U(VI). Powders collected after sintering process are examined by scanning electron microscopy and X-ray diffraction. These results indicate that UHMWPEF-AO is a promising candidate to remove U(VI) from uranium aqueous solutions.

The Molten salt fast reactor (MSFR) shows great promise with high breeding ratio (BR), large negative temperature coefficient of reactivity (TCR), high thermal-electric conversion efficiency, inherent safety, as well as on-line reprocessing. Based on an Improved MSFR (IMSFR) optimized by adding axial fertile salt and a graphite reflector, the influences of ⁷Li enrichment on Th-U breeding are investigated, aiming to provide a feasible selection for the molten salts with high fissile breeding and a relatively low technology requirement for ⁷Li concentration. With the self-developed molten salt reactor reprocessing sequence (MSR-RS) based on SCALE6.1, the burn-up calculations with on-line reprocessing are carried out. Parameters are explored including BR, ²³³U production, double time (DT), spectrum, ⁶Li inventory, and neutron absorption, as well as the tritium production. The results show that the ⁷Li enrichment of 99.95% is appropriate in the fast fission reactor. In this case, BR above 1.10 can be achieved for a long time, corresponding to the ²³³U production of 130 kg per year and DT of 36 years. After 80 years’ operation, the tritium production for 99.5% is only about 7 kg, and there is no obvious increase compared to that for 99.9995%.

For designing and optimizing the reactor core of modular pebble-bed fluoride-salt-cooled high-temperature reactor (PB-FHR), it is of importance to simulate the coupled fluid and particle flow due to strong coolant-pebble interactions. Computational fluid dynamics (CFD) and discrete element method (DEM) coupling approach can be used to track particles individually, while it requires a fluid cell being greater than the pebble diameter. However, the large size of pebbles makes the fluid grid too coarse to capture the complicated flow pattern. To solve this problem, a two-grid approach is proposed to calculate inter-phase momentum transfer between pebbles and coolant without the constraint on the shape and size of fluid meshes. The solid velocity, fluid velocity, fluid pressure and void fraction are mapped between hexahedral coarse particle grid and fine fluid grid. Then the total inter-phase force can be calculated independently to speed up computation. To evaluate HYPERLINK "http://cn.bing.com/dict/search?q=suitability&FORM=BDVSP6&mkt=zh-cn" suitability of this two-grid approach, the pressure drop and minimum fluidization velocity of a fluidized bed were predicted, and movements of the pebbles in complex flow field were studied experimentally and numerically. The spouting fluid through a central inlet pipe of a scaled visible PB-FHR core facility was set up to provide the complex flow field. Water was chosen as liquid to simulate the molten salt coolant, and polypropylene balls were used to simulate the pebble fuels. Results show that the pebble flow pattern captured from experiment agrees well with the simulation from two-grid approach, hence the applicability of the two-grid approach for the later PB-FHR core design.

In this paper, the nature and origin of single event effects (SEE) are studied by injecting laser pulses into different circuit blocks, combining with analysis to map pulse width modulators (PWM) circuitry in the microchip die. A time-domain error-identification method is used in the temporal characteristic analysis of SEE.SEE signatures of different injection times are compared. More serious SEE are observed when the laser shot occurs on a rising edge of the device output for blocks of the error amplifier, current sense comparator, and T and SR latches.

An electronic personal dosimeter (EPD) mainly uses a Si-PIN photodiode as X- and gamma-ray detectors. The photon energy response of this instrument is inconsistent in the case of no correction, which seriously affects the accurate monitoring of personal dose equivalent H_p(10) parameters for radiation workers. For this reason, in this paper we propose a method of combining composite screen detection technology, multichannel measurement technology, and the channel ratio method (CRM) to achieve accurate measurement of the personal dose equivalent parameters. According to China National Standard GB/T 13161-2003 and National Verification Regulation JJG 1009-2006, the instrument was tested in the energy range between 48 keV and 1.25 MeV. The experimental results showed that the difference of energy response to ¹³⁷Cs corrected by the new method was almost constant within ±6.0%, which fulfilled the ±30% requirement of GB/T 13161-2003 and JJG 1009-2006. Meanwhile, the method proposed obtained energy information regarding the radiation field.

In this work, a new hybrid MPGD consisting of two GEM foils and a metallic mesh was proposed. Based on the simulation studies, this design can significantly reduce the rise time of the signal and have a better performance in respect to particle identification compared with the triple GEM design. The gain, with various voltages settings, was computed in order to provide us references for future experiments. The simulation results also show that the time and space resolution compared to the triple GEM detector are also improved. The time and space resolution of the hybrid detector with Ar/CO₂(70/30) and Ar/isobutane(95/5) was investigated for various drift electric field intensities. This new hybrid detector shows excellent potential for both fundamental research and imaging applications.

Pulse shaping, which improves signal-to-noise ratio (SNR) excellently, has been extensively used in nuclear signal processing. This paper presents a cusp-like pulse shaping technique developed through the recursive difference equation in time domain. It can be implemented in field programmable gate array (FPGA) hardware system. Another flat-topped cusp-like shaper is developed to optimize the time constant of pulse shaping and reduce the influence of ballistic deficit. The method of both baseline restoration and pile-up rejection is described. The ¹³⁷Cs energy spectra measured with the digital cusp-like pulse shaper are of 6.6% energy resolution, while those by traditional analog pulse shaper are 7.2% energy resolution, under the same conditions. This technique offers flexibility, too, in adjusting the pulse shaper parameters.

A detector setup for the measurement of angular distribution of heavy-ion elastic scattering at energies around the Coulomb barrier on the Radioactive Ion Beam Line in Lanzhou (RIBLL) at the Heavy-Ion Research Facility in Lanzhou (HIRFL) is designed. The beam profile and the scattering angles on the target are deduced by two Parallel Plate Avalanche Counters (PPACs) and four sets of detector telescopes (including Double-sided Silicon Strip Detectors (DSSD)) placed systematically with the beam line, incorporating with Monte Carlo simulations. The data of ¹⁶O on ⁸⁹Y target were analyzed to compare with the simulation results. It is found that the simulated distribution is agreeable with the experimental data. By assuming the pure Rutherford scattering at small scattering angles, the angular distribution of elastic scattering of ¹⁶O + ⁸⁹Y at low energies can be reasonably obtained. It indicates that this set of detector setup can be used for the measurement of angular distributions of heavy-ion elastic scattering at energies around a Coulomb barrier.

In this paper, mass attenuation coefficients of concrete, brickss and cement plaster, as shielding materials, are calculated at 59.5, 356, 662, 1173, 1274 and 1333 keV by using the MCNP-X (version 2.4.0) code. The numerical simulation results are compared with previous Monte Carlo (MC) studies, experimental results and XCOM data. The effects of barite on mass attenuation coefficients are investigated. The mass attenuation coefficients increases with the barite content. Thus, our results agree well with experimental studies on gamma-ray shielding of barite. It is flexible for the MN method to change the barite rates in material by small increments, which is experimentally difficult. Also, modeled geometry can be used for future approaches such as new designs and new structures especially in investigating new barite-containing materials to build nuclear reactors or high energy radiation therapy facilities.

Accelerator mass spectrometry (AMS) is an ultrasensitive technique for measuring long-lived actinides, e.g. ²³⁶U, ²³⁷Np and Pu isotopes. In order to improve the detection limit for actinides abundance, and to increase the detection efficiency in actinides AMS measurement, a 16-strip silicon detector was used to identify actinides at the Center for Isotopic Research on Cultural and Environmental heritage (CIRCE) in Caserta, Italy. The sensitivity of ²³⁶U/²³⁸U was 1×10⁻¹¹ by spacial resolution and 5.0×10⁻¹² by time resolution. The pulse height defect of ²³⁶U in an ion-implanted silicon detector in the low energy range with 17.26 MeV is presented.

To fabricate thorium-based fuel kernel for solid fuel molten salt reactor, a component of tri-structural isotropic (TRISO) fuel particles is mostly based on sol-gel method. The preparation of thorium sol is an important step for fabrication of thorium-based fuel kernels, such as thorium carbide and thorium oxide. The gel quality affects the gel particle dispersion and the final products. In this work, thorium sols were prepared using Th(NO₃)₄ and NH₃·H₂O by sol-gel method. The effects of thorium concentration, mole ratio of NH₄⁺/NO₃⁻ and reaction temperature on the pH, viscosity, turbidity, particle size and the thorium sol distribution were investigated. The results show that, the viscosity and turbidity increased with the NH₄⁺/NO₃⁻ ratio; the turbidity and colloidal particle size increased with the reaction temperature, which affected little the sol viscosity; the sol viscosity increased with the thorium concentration, which virtually did not change the turbidity; and the particle size decreased and the size distribution narrowed with increasing thorium concentration. The sol could be stored at room temperature for one day without significant property changes. Thorium gel spheres of good quality were prepared at 60°C with the NH₄⁺/NO₃⁻ ratio of 75%–85% and the thorium concentration of 1.2–1.4 mol/L.

In this article, we briefly review the recent progress on collective flow and hydrodynamics in large and small systems at the Large Hadron Collider (LHC), which includes the following topics: extracting the QGP viscosity from the flow data, initial state fluctuations and final state correlations at 2.76 A TeV Pb–Pb collisions, correlations, and collective flow in high energy p–Pb and p–p collisions.