[en] Neutral beam injection (NBI) is an important method of plasma heating and plasma current driving for magnetic confinement fusion device. A distributed control system is designed in this paper according to experimental operation characteristics of NBI on Experimental Advanced Superconducting Tokamak (EAST). The NBI control system based on network technology, classified according to control level, consists of remote monitoring layer, server control layer and field control layer. The three-layer control systematic architecture is easy for extending system functions and upgrading devices. Both ion sources of one NBI beam line are designed to operate independently, which lays a foundation for developing control system of the second beam line on EAST. Experimental results demonstrate that the visualization and automation of NBI experimental operations are successfully implemented by remote monitoring, interlock protection, and data processing. (authors)

[en] A new type of engineering-channel water flooding system was proposed to mitigate severe accidents for the subcritical energy cladding of China Academy of Engineering Physics (CAEP)'s hybrid reactor. The decay heat of the fuel region can be discharged by injecting cooling water in this system, and the combination of this flooding system with the passive containment cooling system contributes to the establishment of a long-term passive cooling of the fuel region, which prevents the core melting and ensures the integrity of the subcritical energy cladding. Under conservative assumptions, when the fuel temperature reaches 1220 ℃, the engineering-channel water flooding system will start to protect the subcritical energy cladding. (authors)

[en] A radiation hydrodynamic model of the atmosphere in the fusion chamber of Z-FFR is built by MULTI, and the physical processes in the atmosphere such as the X-ray radiation transport, gas temperature and density evolutions, as well as shock wave generating and propagating, are studied. Radiative temperature and impact pressure on surface of the first wall are subsequently obtained. Static calculations of the X-ray deposition in tungsten and the X-ray attenuation in the Ar atmosphere are accomplished by a Geant4 code. Combining the dynamic and static calculations, preliminary design of the fusion X-ray mitigation is accomplished. The X-ray fluence threshold incident on surface of the first wall is determined to be 0.2 J/cm², and the initial pressure of the Ar atmosphere is 2000 Pa. (authors)

[en] The Au-doped melamine-formaldehyde (MF) aerogel was fabricated by γ-irradiation of AuCl₃ solution with MF aerogel monoliths impregnated. The obtained samples were characterized by X-ray diffraction (XRD), energy dispersive spectroscopy (EDX) and transmission electron microscope (TEM). The results show that the well distributed Au nanoparticles presented in MF aerogels and the average particle size was 5.8 nm after irradiation. The nitrogen adsorption characterization reveals the introduction of Au nanoparticles produced a reduction of the surface areas and total, micropore and mesopore volumes. (authors)

[en] In the scheme of electron-driven fast ignition of inertial confinement fusion (ICF), MeV relativistic electron beams driven by ultraintense petawatt laser pulses are required and electron energy of several tens of kilojoules should be deposited in the compressed core of an imploded DT shell. The beam quality is crucial to the success of fast ignition. In order to study the generation and transport of the relativistic electron beam, a three-dimensional high-performance parallel particle-in-cell code is developed and improved. In this review, this paper shows the researches on the generation of high-quality electron beams and the method of beam divergence controlling of our research group. Two main reasons for poor beam quality are firstly introduced: pre-plasma effect and random scattering of the magnetic field produced by the beam instability. In addition, enhancement of electron beam flux and collimation of its propagation are investigated. Four ways to obtain collimated electrons are put forward: 1) reduce the pre-plasma effect with a double cone target; 2) collimate fast electrons in specially engineered targets with the spontaneously generated magnetic field during its transportation; 3) collimate fast electrons with external magnetic field; 4) control the beam instability at the laser-plasma interface. (authors)

[en] Due to the fuel surrounded by a high-Z pusher, the double-shell target differs from the cryogenic single-shell case, and it requires volume ignition of the whole fuel. In the paper, the ignition condition for the fuel surrounded by a high-Z pusher is analyzed, and an indirect-drive cryogenic double-shell ignition target is designed and analyzed, which releases a comparable energy to the hot-spot ignition target to be performed at National Ignition Facility (NIF). The collision between the outer and inner shell is the key in the energy transport. By adjusting the ratio of the mass between the two shells, the efficiency of the energy from the outer shell to the inner shell can be highly elevated, with a purpose of reducing the size of the target and the required energy to achieve ignition. For the double-shell ignition, a new preheating mechanism by the radiative shock is pointed out, which can help stabilize the Rayleigh-Taylor (RT) instability occurring at the outer surface of the inner shell. The preheat of radiative shock, as a potential effect in double-shell target, should be seriously realized and underlined. (authors)

[en] Flash X-ray generator comprises a pulsed power driver and a diode. Pulse forming line (PFL) and transmission line are utilized to generate high voltage with several MV on diode, and the function of the latter is to compress the pulse rise time and match the impedance of PFL to diode's. Impedance and capacitance of these coaxial lines are calculated to get the highest voltage and certain pre-pulse on load, respectively. Configuration of diode insulators are designed based on radial grading rings, and the layout of a flash X-ray generator is proposed. The results show that a voltage of 4 MV is generated on 40 Ω load when 2.6 MV and 3.3 MV voltage charging to immediate storage energy and PFL, respectively. Meanwhile the pre-pulse is about 1.2% of charging voltage to PFL. (authors)

[en] An accurate quantum efficiency (QE) map is very important in characterizing the performances of semiconductor photocathodes. This paper presents the study of a QE mapping system built on a DC high-voltage GaAs photocathode injector. A focusing lens is used to move the laser spot to different locations on the photocathode and to map the quantum efficiency. The control system and the data acquisition are established by LabVIEW. With a single sampling time of 2.3 s and a resolution of 0.32 mm, several quantum efficiency maps of the GaAs photocathode have been measured during 330 h. Both the distribution and the decay of the quantum efficiency have been observed from these maps as non-uniform. The quantum efficiency in the high quantum efficiency region decays slower than that in other regions. This QE mapping system is critically useful in improving the preparation technique of the photocathode. (authors)

[en] The collimator at the end of the ring to target beam transport (RTBT) line is one of the key devices in the Chinese Spallation Neutron Source (CSNS) project. Design reliability of the collimator is extremely important since the high radiation on it due to its closeness to the target station. According to the working principle of the collimator and CSNS physical design requirements, comparing the design experience of similar foreign accelerator, the collimator is designed. Considering strict requirements of thermal deposition, power loss and material performance in the design process, the specific scheme is expounded. Using the result compared between Bethe-Bloch formula and SRIM software to determine the reliability of the simulation tool and simulation methods. According to the result of ANSYS finite element software simulation, the reliability of the collimator structure design is verified. (authors)

[en] In the inertial confinement fusion (ICF) experiment, down-scattered neutrons for fuel areal density measurement need to be separated from other background. The background on Shenguang Ⅲ facility is analyzed in detail by Monte Carlo for the DD fuel. As a result, the background is mostly from the process that primary neutrons scatter through vacuum chamber, surrounding diagnostic platforms, ceiling and floor. According to the analysis, appropriate materials and shielding solution are chosen. And the structure of the collimator is optimized by Monte Carlo. The design meets the experimental requirements. (authors)