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Superconducting Electron Cyclotron Resonance ion source with Advanced design in Lanzhou (SECRAL) is an advanced fully superconducting ECR ion source at IMP designed to be operational at the microwave frequency of 18--24 GHz. The existing SECRAL beam transmission line is composed of a solenoid lens and a 110° analyzing magnet. Simulations of particle tracking with 3D space charge effect and realistic 3D magnetic fields through the line were performed using particle-in-cell code. The results of the beam dynamics show that such a low energy beam is very sensitive to the space charge effect and significantly suffers from the second-order aberration of the analyzing magnet resulting in large emittance. However, the second-order aberration could be reduced by adding compensating sextupole components in the beam line. On this basis, a new 110° analyzing magnet with relatively larger acceptance and smaller aberration is designed and will be used in the design of low energy beam transport line for a new superconducting ECR ion source SECRAL-II. The features of the analyzer and the corresponding beam trajectory calculation will be detailed and discussed in this paper. [ABSTRACT FROM AUTHOR]

Parameters governing forward and reverse pumping of a device mechanism have an important influence on the cutoff and output characteristics of a drift-step-recovery diode (DSRD). Therefore, we analyzed the driving circuit for the DSRD that was used to adjust pumping parameter values. With multiple modules in parallel, a driving method exploiting narrow-pulse pumping is proposed in developing a high-repetition-frequency DSRD pulse generator. In experiments and simulations, one key factor affecting the working stability of this pulse generator operating at repetition frequencies in the megahertz range was found that helped in further optimizing the parameter settings of our 2 kV DSRD driving circuit. From this insight, a 2 kV-5 MHz all-solid-state high-repetition-frequency pulse generator based on the DSRD was developed.

Material properties of SiC determine the application potential of corresponding sensors in a high temperature and harsh environment. However, few reports are available to describe basic design principles of SiC sensors. In this paper, aiming at improving the sensitivity of the sensor, the structural design of a full-SiC piezoresistive pressure sensor is studied from the aspects of diaphragm structure, material, piezoresistor arrangement, and dimension. The differences between the isotropy theoretical calculation and the anisotropy simulation are analyzed. Furthermore, in order to conform to the anisotropic intrinsic properties of the SiC material, a fitting curve between the diaphragm stress and the corresponding design parameter a/h is obtained by using a quadratic function. Through comparison, a square diaphragm can obtain more stress than a circular diaphragm; however, it is not suitable for SiC pressure sensors due to the process difficulties in anisotropic etching. Both experiment and simulation results show that higher output sensitivity can be obtained when the four piezoresistors are distributed along the radial direction of the diaphragm. With the control variable method, we found that when the area of the edge piezoresistors is increased by 10 times, output sensitivity will decline by 23.66%. Instead, the size of the two piezoresistors at the center shows a minor impact. Therefore, the size of edge piezoresistors has a significant effect on output sensitivity, which is worth paying attention to and should be minimized. Sensor prototypes were fabricated with optimal design, and preliminary experimental results show that zero output is only slightly affected by temperature due to the good thermal stability of SiC materials.

A beam-profile monitor has been constructed based on a two-dimensional cross-connected-pixels anode and a 128-channel picoammeter system. It can provide the total beam current, as well as the current projections in the x- and y-directions with a spatial resolution of ∼1 mm. It is suitable for diagnosis of low-energy charged-particle beams ranging from subpicoamperes to nanoamperes, e.g., the ion beams extracted from an electron beam ion source.

Because of its simple principle and high adaptability to severe operational conditions, the capillary-tube viscometer has been widely used for viscosity measurement. However, difficulties in accurately correcting the end effect induced measurement deviation will result in great uncertainty for measurement results. In order to solve this problem, in this work, we studied factors affecting the end effect by conducting the high pressure nitrogen viscosity measurement at low flow velocity with an improved capillary-tube viscometer. The experimental results indicated that the influence of the end effect became less significant with the decrease in flow velocity (v) and tube inner diameter (d) and varied inversely with the length of tube (L). We defined the ratio of measured viscosity to standard viscosity obtained from the NIST database as the viscosity deviation coefficient (C e ). From the C e vs v, C e vs d, and C e vs L curves, we have observed that there existed a threshold velocity (v threshold ), a threshold diameter (d threshold ), and a threshold length (L threshold ) at which C e got closer to 1.0. It suggested that under certain experimental conditions, the influence of the end effect on gas viscosity measurement became negligible. Based on that, we established end effect free capillary-tube viscometry and compared the nitrogen viscosity results measured by this method with the data provided by the NIST database. The results presented a good match with error within 1.2%. These insights will contribute to improving the accuracy of a capillary-tube viscometer especially under high pressure.

Among high power microwave (HPM) generators without guiding magnetic field, Cerenkov-type oscillator is expected to achieve a relatively high efficiency, which has already been realized in X-band in our previous simulation work. This paper presents the preliminary experimental investigations into an X-band Cerenkov-type HPM oscillator without guiding magnetic field. Based on the previous simulation structure, some modifications regarding diode structure were made. Different cathode structures and materials were tested in the experiments. By using a ring-shaped graphite cathode, microwave of about one hundred megawatt level was generated with a pure center frequency of 9.14 GHz, and an efficiency of about 1.3%. As analyzed in the paper, some practical issues reduce the efficiency in experiments, such as real features of the electron beam, probable breakdown regions on the cathode surface which can damage the diode, and so forth.

At Institute of Modern Physics (IMP), Chinese Academy of Sciences (CAS), the superconducting Electron Cyclotron Resonance (ECR) ion source SECRAL (Superconducting ECR ion source with Advanced design in Lanzhou) has been put into operation for about 10 years now. It has been the main working horse to deliver intense highly charged heavy ion beams for the accelerators. Since its first plasma at 18 GHz, R&D work towards more intense highly charged ion beam production as well as the beam quality investigation has never been stopped. When SECRAL was upgraded to its typical operation frequency 24 GHz, it had already showed its promising capacity of very intense highly charged ion beam production. And it has also provided the strong experimental support for the so called scaling laws of microwave frequency effect. However, compared to the microwave power heating efficiency at 18 GHz, 24 GHz microwave heating does not show the ω(2) scale at the same power level, which indicates that microwave power coupling at gyrotron frequency needs better understanding. In this paper, after a review of the operation status of SECRAL with regard to the beam availability and stability, the recent study of the extracted ion beam transverse coupling issues will be discussed, and the test results of the both TE01 and HE11 modes will be presented. A general comparison of the performance working with the two injection modes will be given, and a preliminary analysis will be introduced. The latest results of the production of very intense highly charged ion beams, such as 1.42 emA Ar(12+), 0.92 emA Xe(27+), and so on, will be presented.

In this work, we develop an instrument to study the ablation and oxidation process of materials such as C/SiC (carbon fiber reinforced silicon carbide composites) and ultra-high temperature ceramic in extremely high temperature environment. The instrument is integrated with high speed cameras with filtering lens, infrared thermometers and water vapor generator for image capture, temperature measurement, and humid atmosphere, respectively. The ablation process and thermal shock as well as the temperature on both sides of the specimen can be in situ monitored. The results show clearly the dynamic ablation and liquid oxide flowing. In addition, we develop an algorithm for the post-processing of the captured images to obtain the deformation of the specimens, in order to better understand the behavior of the specimen subjected to high temperature.