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Helium-hydrogen separation bed is an important part of tritium extraction system. In order to deeply study penetration performance of the radial flow bed and guide the structure design, the mathematical model of radial bed breakthrough capacity was established by coupling material hydrogen absorption kinetics equation, mass transfer equation and fluid flow momentum equation in COMSOL Multiphysics, which was used to carry out parametric scanning of the characteristic parameters, and the effect of the model on the breakthrough capacity was analyzed. The results show that the breakthrough experiment results are in good agreement with the simulated data, and the model is reliable. The effect of temperature, height-diameter ratio and porosity on the breakthrough capacity was analyzed. The adsorption temperature of the bed is from room temperature to 343 K. In this temperature range, increasing the temperature has less effect on the length of the mass transfer zone and the concentration-time curve at the outlet. With the increase of the height-diameter ratio, the efficiency of the bed decreases significantly, in which the high efficiency is maintained for a longer period of time when the hieght-diameter ratio is 2.00-8.33. With the increase of porosity, the adsorption efficiency of the bed decreases significantly. Considering the adsorption efficiency, the flow resistance and the difficulty of powder loading, the powder porosity is recommended from 0.56 to 0.64. Therefore, the model established in this study can better predict the adsorption performance, and can be used to optimize the structure design basis and process parameters.

The resistance temperature characteristics and thermal stability of graphite based flexible grounding materials were studied. With the method of current heating and constant temperature protection, the resistance of grounding body at each temperature was measured by voltammetry, and the average resistance temperature coefficient was derived. With the resistance temperature characteristic parameters of the grounding body obtained from the experiment, the maximum temperature rise of the graphite based flexible grounding body under the power frequency grounding fault current and lightning impulse current was calculated iteratively, which is verified by the calculation of the thermal stability coefficient. The experimental results show that the graphite based flexible grounding body has a negative temperature coefficient. When the maximum allowable service temperature of the graphite based flexible grounding body is 450 ℃, the maximum allowable current under 0.5 s power frequency current is about 1.4 kA, which is 8/20 μs the maximum allowable passing current amplitude of graphite based flexible grounding body under the impact of high frequency lightning current is 287.9 kA.

High-power pulse generators are widely used in civil and military fields. The main switch directly determines the output characteristics of the high-power pulse generators, such as the voltage front time (t f). Pseudospark switches (PSS) show a promising future for middle voltage, high repetitive frequency pulse power applications. However, how to further improve the breakdown behavior without reducing its advantages is a challenging task. In this paper, the influence of operating parameters (anode voltage U A and gas pressure p) and structural parameter (number of cathode holes) on the breakdown behavior are investigated, the related mechanism are explained, and specific improvement schemes are proposed. It is found that the t f of the single channel PSS (SCPSS) decreased significantly with increasing p, but hardly varied with U A under moderate p. However, it is not a sound solution to increase the p excessively to reduce t f. Besides, increasing the number of cathode holes can obtain a shorter t f at low pressures (which implies superior repetition frequency performance). However, at 25 Pa, the jitter (which is defined as the standard deviation of t f in multiple tests) of the 2-channel PSS is larger than that of the SCPSS. And the jitter of the 4-channel and 8-channel PSS is also greater than 6 ns and 2 ns, respectively. Through experimental and simulation analyses, it can be explained as the stepwise penetration of the virtual anode and the non-simultaneous ignition of the channels. A scheme to increase the trigger energy (ϵ) has been adopted to improve the simultaneous ignition probability, while shortening t f and reducing jitter. After optimization, the good ignition probability of the 4-channel PSS has been improved to 82% and the jitter has been reduced to less than 1 ns at 25 Pa and 14.7 mJ. [ABSTRACT FROM AUTHOR]

helium-3 influence was analyzed by combining with the Ortman model. The results showed that helium blanketing effect affected the adsorption performance of Zr0.85Ti0.15Co alloy significantly, but the blanketing effect could not completely inhibit the tritium absorption reaction, and it could continue to absorb tritium at a low rate until the adsorption was completed. The completion time of tritium absorption was mainly affected by helium-3 concentration when helium-3 concentrations was low, while when the helium concentration was high, it was mainly affected by the initial tritium partial pressure. Helium-3 blanketing process included two steps, that was “bulk flow” and “diffusion flow”, and Ortman model could predict the helium shielding pressure in “bulk flow”.

The discharge mode characteristics of cathodes may strongly influence the discharge stability and performance of electrostatic thrusters. In this article, discharge characteristics and mode transition phenomenon of the ring-cusp magnetically confined plasma bridge neutralizer (RCM-PBN) were experimentally studied using argon as the working gas. The dependences of anode current and oscillation amplitude on anode voltage, argon flow rate, heater power, and cathode-to-anode distance were investigated. Plasma properties were measured and plasma plume images were taken under different discharge modes. Two distinct discharge modes were observed during the experiments: high oscillation mode and low oscillation mode. In the high oscillation mode, the plasma plume appears dim, the anode current is low, and the oscillation level is more than 2%. While in the low oscillation mode, a spot-like structure close to the orifice is observed. The plume becomes brighter, the anode current increases, and the oscillation level decreases below 2%. The RCM-PBN was found to transition into the low oscillation mode by increasing anode voltage, flow rate, heater power and by decreasing the cathode-to-anode distance. [ABSTRACT FROM AUTHOR]

The Blumlein pulse forming network (PFN) has widely been used in pulsed power technology to generate square waves with short pulse widths. In this paper, we developed a repetitive frequency square wave generator based on Blumlein PFN and pseudospark switch (PSS). A Blumlein PFN with unequal capacitances has been proposed, and the PFN parameters have been optimized for better output waveforms. A single-gap PSS with a withstand voltage of 40 kV and a repetitive frequency of 100 Hz has been designed to switch the Blumlein PFN. The experiment results show that the square wave generator can output pulses with a voltage of 26 kV, a rise time of 25 ns, and a pulse width of 90 ns on a matched load of 11 Ω. It has operated steadily for 10 h with a repetitive frequency of 100 Hz, and the jitter remains at around 1 ns after 1.05 × 106 shots. [ABSTRACT FROM AUTHOR]

The use of linear transformer drivers (LTDs) is widely considered the most promising technological approach for the development of future pulsed-power accelerators. In large-scale pulsed-power accelerators, abnormal conditions like switch prefire can occur frequently during tests and normal operations due to the presence of a large number of switches. The diagnosis of such faults based on signature waveforms requires further investigation. According to previous research, the characteristics of the magnetic cores greatly influence the fault waveforms. In this paper, a full-cycle mathematical model of the magnetic core is established utilizing a classical Preisach model based on experimental results. This model is coupled with the LTD circuit model in simulations, and simulation results are obtained under the condition of switch prefire. The simulation results are in good agreement with the experimental results from a four-stage LTD module with a sharing shell and de-ionized water insulated transmission line. The magnetization process of the cores is also determined under prefire conditions. Analyses of the magnetization process indicate that the completely demagnetized core shows high permeability under positive excitation and that the permeability abruptly decreases as the excitation is reversed. The hysteresis characteristics result in a phenomenon in which the output voltage in the prefired stage is almost unipolar. Finally, the features of the fault voltages captured in the experiments are also explained. [ABSTRACT FROM AUTHOR]