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A low-energy proton accelerator named pulsed synchronous linear accelerator (PSLA) is proposed and developed at the Institute of Fluid Physics, which is driven by unipolar-pulsed high voltages. Pulsed-accelerating electric fields and low-energy ion beams are precisely synchronized on temporal and spatial positions for continuous acceleration. The operating mode and the features of the PSLA are introduced. At present, the feasibility of a low-energy proton PSLA has been verified in principle. An average accelerating gradient up to 3 MV/m for protons is achieved.

A modified Kombinierte Null Grad Struktur (KONUS) beam dynamics for inter-digital H-mode (IH) drift tube linac (DTL) is proposed in this study. This modified KONUS beam dynamics, which is aperiodic and is suitable for a short ( injector of a synchrotron-based proton therapy system, is divided into three sections, namely, rebunching ( − 80°), 0°acceleration, and debunching (10°). It is slightly different from the conventional KONUS cavity, and no focusing magnets exist in the cavity to reduce the cost of fabrication. The presence of 21 gaps in the cavity can accelerate a 15 mA proton beam from 3 MeV to 7 MeV. The cavity is tapered to adjust the gap voltage distribution, and the inner diameter varies from 196.8 mm to 232.6 mm. A cavity length of 1 m has a theoretical power consumption of 151 kW, whereas the maximum surface electric field is 40 MV/m (2.3 Kp). A new design process, which is similar to alternating-phase focusing method, is proposed. Details of the design method and results are presented in this study.

Dielectric ceramics have raised particular interest since they enable pulsed-power systems to achieve high voltage gradient and compact miniaturization. In this work, x wt%Ni2O3 doped Al2O3-SiO2-TiO2 based dielectric ceramics were prepared using conventional solid-state reaction and the effects of Ni2O3 on the crystal structure, dielectric properties and dielectric breakdown strength were investigated. It was found that with the doping of Ni2O3, the Al2O3-SiO2-TiO2 based dielectric ceramics became denser and the distribution of each phase was more uniform. For the composition of x = 2.0, the dielectric breakdown strength was increased into 82.1 kV/mm, more than twice compared with that of the undoped one. In addition, the relationship between the dielectric breakdown strength and the resistance of Al2O3-SiO2-TiO2 based dielectric ceramics was discussed. The results show that the doping of Ni2O3 is a very feasible way to improve the dielectric breakdown strength and optimize the dielectric properties for the Al2O3-SiO2-TiO2 based dielectric ceramics.

A pulsed synchronous linear accelerator (PSLA), based on the solid-state pulse forming line, photoconductive semiconductor switch, and high gradient insulator technologies, is a novel linear accelerator. During the prototype PSLA commissioning, the energy gain of proton beams was found to be much lower than expected. In this paper, the degradation of the energy gain is explained by the circuit and cavity coupling effect of the accelerating units. The coupling effects of accelerating units are studied, and the circuit topologies of these two kinds of coupling effects are presented. Two methods utilizing inductance and membrane isolations, respectively, are proposed to reduce the circuit coupling effects. The effectiveness of the membrane isolation method is also supported by simulations. The decoupling efficiency of the metal drift tube is also researched. We carried out the experiments on circuit decoupling of the multiple accelerating cavity. The result shows that both circuit decoupling methods could increase the normalized voltage.

Experimental investigations on the vacuum outgassing of a carbon nanotube (CNT) cathode with high-intensity pulsed electron emission on a 2 MeV linear induction accelerator injector are presented. Under the 1.60 MV diode voltage, the CNT cathode could provide 1.67 kA electron beam with the amount of outgassing of about 0.51 PaL. It is found that the amount of outgassing, which determines the cathode emission current, depends on the diode voltage and the vacuum.

Vacuum surface flashover of the high gradient insulator (HGI), which consists of many alternative layers of conductors and insulators, was found to generally start from one or several dielectric layers adjacent to the anode under nanosecond pulse by using the fast photography. A simple model is proposed to explain the experimental observations. The secondary electron emission avalanche (SEEA) along the dielectric surface adjacent to the anode will be greatly enhanced due to the upstream SEEA starting from the traditional and the intermediate cathode triple junctions. The 15-mm-thick HGI samples with different numbers of dielectric layers were tested and the samples with six and eight dielectric layers showed the best performance. The experimental result proves that as the number of dielectric layers reaches a certain level, the performance of the HGI will decrease as the number of dielectric layers increases.

Lens focused proton radiograph on thin objects is demonstrated using an 11-MeV proton cyclotron at China Academy of Engineering Physics. The proton beam exiting from the tested objects is focused onto the image plane by a magnetic lens system mitigating image blur caused by multiple Coulomb scattering. Both simulations and experiments show that clear images can be obtained with a lens system for the objects with thickness up to 2.7 × 10−2 g/cm2 and the error for the areal density measurement is measured to be less than 2.3%. For the objects with thickness between 2.7 × 10−3 g/cm2 and 2.7 × 10−2 g/cm2, 100–200 μm of spatial resolution is achieved.

Magnifying magnetic lenses can be used in high-energy proton microscopes. The −I lens suggested by Zumbro is analyzed in this paper, and a new type of magnetic lens called a lengthened lens is introduced. Theoretical analysis shows that the lengthened lens can form a magnifying lens, and at the same time the main advantages of a Zumbro lens are inherited. Using the My-BOC beam dynamics code, an example of the design is shown. The results show that the method of designing magnifying magnetic lenses is effective.

The typical response of the X-ray converter material impacted by an intense relativistic electron beam is vaporization and rapid expansion. For the Dragon-I accelerator (2.5 kA, 20 MeV, 60 ns), the slab target is replaced by a multi-foil target in order to reduce the unwanted debris ejected from the target. Comparisons of the output X-ray performance and the hydrodynamic response between the slab target and the multi-foil target are calculated by numerical methods. We found that vaporization and melt ejection dominate the hydrodynamic response in the multi-foil target while the mechanical effect plays an important role in the slab target. We also report the single-pulse experiments which measure the surface density decrease of the converter material after a specified delay. The experimental results show good agreement with the numerical prediction. Hydrodynamic response of the multi-foil target impacted by three successive pulses in 1 μs is also studied by simulation. The results indicate that although the surface density of the material decreases rapidly during the inter-pulse time scale, the X-ray dose produced by the second and the third pulse will nearly maintain the same as the first one.

A 100-mm-diameter scandate dispenser cathode was tested as a photocathode with a 10 ns Nd:YAG laser (266 nm) on an injector test stand for linear induction accelerators. This thermionic dispenser cathode worked at temperatures ranging from room temperature to 930 °C (below or near the thermionic emission threshold) while the vacuum was better than 4×10 −7 Torr. The laser pulse was synchronized with a 120 ns diode voltage pulse stably and they were in single pulse mode. Emission currents were measured by a Faraday cup. The maximum peak current collected at the anode was about 100 A. The maximum quantum efficiency measured at low laser power was 2.4×10 −4 . Poisoning effect due to residual gas was obvious and uninterrupted heating was needed to keep cathode’s emission capability. The cathode was exposed to air one time between experiments and recovered after being reconditioned. Photoemission uniformity of the cathode was also explored by changing the laser spot’s position.

Compact solid-state system is the main development trend in pulsed power technologies. A compact solid-state high-voltage nanosecond pulse generator with output voltage of 300 kV amplitude, 10 ns duration (FWHM), and 3 ns rise-time was designed for a dielectric wall accelerator. The generator is stacked by 15 planar-plate Blumlein pulse forming lines (PFL). Each Blumlein PFL consists of two solid-state planar transmission lines, a GaAs photoconductive semiconductor switch, and a laser diode trigger. The key components of the generator and the experimental results are reported in this paper.

Conduction modes of GaAs photoconductive semiconductor switch (PCSS) and their conditions are expounded. Laser diode and high-power picosecond Nd:YAG lasers are used as triggers for nonlinear mode and quasi-linear mode respectively in high-power conduction experiment. GaAs PCSS`s failure mechanisms and factors influencing lifetime in both modes are analyzed. It is found that the power density of laser at trigger time determines in which mode GaAs PCSS operates. Low-power laser triggers a nonlinear mode conduction in which GaAs PCSS`s lifetime is only 10 3 , while high-power laser triggers a quasi-linear mode conduction in which GaAs PCSS`s lifetime is up to 10 5 . According to the findings, the compact high-power pulsed power system based on mass of GaAs PCSSs demands for miniature high-power laser generators.

Some efforts were made to measure the electron emission characteristics of velvet under multi-pulse mode. The voltages across the diode were 1 MV for two-pulse mode and 500 kV for four-pulse mode. Pulse duration was 100 ns and pulse to pulse separation was 400 ns. The research indicates that under multi-pulse mode the emission of velvet is not uniform and that beam degradation is caused by cathode plasma motion. The factors that determine the plasma motion are analyzed and the experimental results of plasma velocity and its distribution are presented.

Charged particle radiography has become a promising new approach in the field of transmission radiography because of the invention of the magnetic imaging lens. The using of the imaging lens makes it possible for thick objects to get significantly improved transmission radiography. Currently, the conventional charged particle radiography only uses the information of the flux attenuation and the angular scattering of the transmitted particles to determine the properties of the sample. However, the energy loss of the incident particles introduced by ionizations throughout the object limits the spatial resolution of the image because of the chromatic blur. In this paper a new concept of imaging lens that uses the information of the energy loss is proposed. With a specially designed imaging lens, the information of the energy loss could result in apparent contrast in the final image. This design procedure of the energy loss imaging lens is presented, and a preliminary design is verified by numerical simulations. Experimental demonstration is also expected on a cyclotron at the Institute of Fluid Physics, CAEP.

Pulsed power researches for military and civil applications have been conducted at China Academy of Engineering Physics (CAEP) for more than fifty years. The pulsed power research activities include development of pulsed power components such as different kinds of high voltage switches, series of pulsed power sources and pulsed X-ray machines, high current accelerators for Z-pinch and flash X-ray radiography as well as medical application, electro-magnetic launch and so on. The most recent progress of pulsed power researches at CAEP will be presented.

The big-size (Φ100, 135, and 155mm) scandate dispenser cathodes have been fabricated in BVERI and tested in injector system of LIA. The results show that impregnated scandate cathodes which have better emission performance can be applied as the electron source in LIA and satisfied the requirement of the LIA. The pulse current of both Φ135 and Φ155mm cathode assemblies is more than 2000A and the current density is more than 14 A/cm 2 . At the same time, the cathode has good emission stability and repetition with respect to single pulse and three-pulse modes.

According to the situation of the ventilation's door in NO.3 coal mine of JINING can not open and close fully in place, and it is easy to cause accident hidden danger, this paper puts forward four kinds of solutions and uses the automatic control system based on PLC and rotary encoder. Field operation shows that the system is running stably and the ventilation door can open (close) reliably. This automatic control system greatly improves the safety of production in coal mine.

CAN bus is one of the most widely used field bus. In the light of the faults of PLC industrial network established by RS485, this paper presents a scheme for PLC accessing to the CAN bus network, which is based on the 32 bit MCU LPC2294. The author describes in detail the features of 32 bit ARM microcontroller, LPC2294 and CAN TJA1050T transceiver and gives the hardware structure and software design of PLC using as a CAN bus intelligent node. Combining with the actual use of the hardware, the author puts forward the anti interference measures.

An investigation on the plasma-induced field emission (PFE) properties of a large area carbon nanotube (CNT) cathode on a 2 MeV linear induction accelerator injector is presented. Experimental results show that the cathode is able to emit intense electron beams. Intense electron beams of $14.9--127.8\text{ }\text{ }\mathrm{A}/{\mathrm{cm}}^{2}$ are obtained from the cathode. The CNT cathode desorbs gases from the CNTs during the PFE process. The fast cathode plasma expansion affects the diode perveance. The amount of outgassing is estimated to be $0.06--0.49\text{ }\text{ }\mathrm{Pa}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{L}$, and the ratio of outgassing and electron are roughly calculated to be within the range of 170--350 atoms per electron. The effect of the outgassing is analyzed, and the outgassing mass spectrum of the CNT cathode has been studied during the PFE. There is a significant desorption of ${\mathrm{CO}}_{2}$, ${\mathrm{N}}_{2}(\mathrm{CO})$, and ${\mathrm{H}}_{2}$ gases, which plays an important role during the PFE process. All the experiments demonstrate that the outgassing plays an important role in the formation of the cathode plasma. Moreover, the characteristic turn-on time of the CNT cathode was measured to be 39 ns.

Ions released from target surfaces by impact of a high intensity and current electron beam can be accelerated and trapped in the beam potential, and further destroy the beam focus. By solving the 2D Poisson equation, we found that the charge neutralization factor of the ions to the beam under space charge limited condition is $1/3$, which is large enough to disrupt the spot size. Therefore, the ion emission at the target in a single-pulse beam/target system must be source limited. Experimental results on the time-resolved beam profile measurement have also proven that. A new focus scheme is proposed in this paper to focus the beam to a small spot size with the existence of back-streaming ions. We found that the focal spot will move upstream as the charge neutralization factor increases. By comparing the theoretical and experimental focal length of the Dragon-I accelerator (20 MeV, 2.5 kA, 60 ns flattop), we found that the average neutralization factor is about 5% in the beam/target system.

Both kinds of 10cm diameter thermionic dispenser cathode have been fabricated at BVERI. One is impregnated scandate(I-Sc) cathode and the other is traditional Ir-coated “M” cathode with 411 impregnant. Figure1 is the photograph of Φ10cm cathode assembly. The scandate cathode can deliver the same density as “M” cathode but 80–100°C lower in temperature, though it needs higher vacuum than “M” cathode.

"Dragon-I" is a high current pulsed electron linear induction accelerator designed and constructed in IFP/CAEP. It generates a 20 MeV, 2.5 kA, 60ns pulsed electron beam. The whole facility has three parts: injector; accelerator and beam focus system. The accelerator consists of 72 induction cells and 18 connection cells. A solenoid was installed inside each cell forming the beam transport system. During the initial beam test both high frequency and low frequency beam centroid oscillation were found. A lot of simulation and experiment investigations were done to obtain the transverse impedance of the cells and to reduce the corkscrew motion of the electron beam. Details of both the simulation and the experimental methods to control the instability are presented.

Proton radiography is a new scatheless diagnostic tool providing a potential development direction for advanced hydrotesting. Recently a low energy proton radiography system has been developed at the Chinese Academy of Engineering Phyiscs (CAEP). This system has been designed to use an 11 MeV proton beam to radiograph thin static objects. This system consists of a proton cyclotron coupled to an imaging beamline, which is the first domestic beamline dedicated to proton radiography experiments. Via some demonstration experiments, the radiography system is confirmed to provide clear pictures with spatial resolution ~100 μm within 40 mm field-of-view.

The beam transport design of a novel proton dielectric wall accelerator is introduced in this paper. The protons will be accelerated from 40 keV to nearly 1 MeV under an accelerating gradient that is as high as 20 MV/m. A consideration of the beam line as well as the transport simulation is presented. The influences of the injection timing jitter and the accelerating pulse timing jitter are also discussed.

One kind of instantaneous electron beam emittance measurement system based on the optical transition radiation principle and double imaging optical method has been set up. It is mainly adopted in the test for the intense electron-beam produced by a linear induction accelerator. The system features two characteristics. The first one concerns the system synchronization signal triggered by the following edge of the main output waveform from a Blumlein switch. The synchronous precision of about 1 ns between the electron beam and the image capture time can be reached in this way so that the electron beam emittance at the desired time point can be obtained. The other advantage of the system is the ability to obtain the beam spot and beam divergence in one measurement so that the calculated result is the true beam emittance at that time, which can explain the electron beam condition. It provides to be a powerful beam diagnostic method for a 2.5 kA, 18.5 MeV, 90 ns (FWHM) electron beam pulse produced by Dragon I. The ability of the instantaneous measurement is about 3 ns and it can measure the beam emittance at any time point during one beam pulse. A series of beam emittances have been obtained for Dragon I. The typical beam spot is 9.0 mm (FWHM) in diameter and the corresponding beam divergence is about 10.5 mrad.

The experimental system measuring the X-ray spot size for the 12 MeV LIA is given in this paper. By means of one-time discharge, the system adopts the sharpness-edge and big-hole imaging simultaneously, thereby acquiring the size of the X- ray spot and the shape of the spot. Using the density distribution of the image and combining with numerical calculating, the space distribution of spot intensity is simulated. At the same time, the modulation transfer function for the 12 MeV LIA X-ray imaging can be obtained with the system.

In this paper, interferometric measurement is used to establish the spatial- and temporal-resolved plasma-density distribution. The Mach-Zehnder interferometer is established in "Dragon-I" target zone; the experiment with the interferometer was conducted, and interferograms were obtained by the high-speed multiframe CCD camera. By counting the fringe shift on the interferograms, the density of plasma was calculated to be at the order of 1022/m3.

Proton radiography has provided a potential development direction for advanced hydrotesting, and its image blur is a crucial point that needs to be deeply studied. In this article, numerical simulation by using the Monte Carlo code Geant4 has been implemented to investigate the entire physics mechanism of high energy proton beam travelling through the object and beamline and arriving at the image plane. This article will mainly discuss the various factors which cause the image blur, including the chromatic aberration of the imaging beamline, the insufficient modulation of an incident particle's transverse displacement and angle deviation, the longitudinal length of an object, the influence of containment vessel and otherwise.

Some research has been done on making a compact, portable pulse forming line. A kind of ceramic based on SrTiO(3) is used as the dielectric of the planar pulse forming line. The ceramic's dielectric constant is around 300 and can store more energy than water with the same volume. However, it is not easy to manufacture the large ceramic bulk but we did successfully manufacture 80 x 10 x 6 cm(3) ceramic bulks. Using this kind of ceramic bulk as the dielectric, we successfully made a compact, portable line that generated a voltage pulse up to 150 kV with a duration of about 92 ns.

Proof-of-principle experiments on the megahertz burst rate high-voltage triple-pulse induction acceleration concept are described and the experimental results are presented. High-voltage triple pulser supplies a triple-pulse burst at pulse rate of 1.25MHz to the acceleration gap of a ferrite induction device after the ferrite cores reset; a train of three 180kV pulses separated by 800ns was obtained in the accelerating gap. Each pulse has a full width at half maximum of 120ns and ±1% flattop of 50ns, with rise time of 40ns, respectively.