Fusion Core Imaging Experiment Based on the Shenguang II Facility

A laser fusion experiment was performed based on the Shenguang II facility. An image of thermonuclear burning region was obtained with a Fresnel zone plate-coded imaging technique, where the laser-driven target was served as an a-particle source, and the coded image obtained in the experiment was reconstructed by a numerical way.     

Image reconstruction from Compton scattering data

A new image reconstruction method was developed for a Compton camera. A simulation to determine a γ-ray source position was performed by using the simulation tool, GEANT4. An image reconstruction was made in two steps. First, a three dimensional image was constructed and projected in one selected plane, then the points from each ellipse was picked up by taking the peak points of a density distribution of crossing points between the ellipse and the first step image. The second step procedure improved the accuracy and the spatial resolution of a position determination significantly, comparing with the image obtained by only the first step. The accuracy and the resolution for a point source were obtained to be about 0.02 mm and (1.35 0.15) mm, respectively. The same procedure was applied to an imaging of the distributed y-ray source.     

Measurement of spatial resolution of 11 MeV proton radiography

Proton radiography experiment with a Zumbro lens system was carried out on an 11 MeV proton cyclotron.The experimental results show that the image blurring is improved markedly. Clear images and good spatial resolution of the density step edges are obtained, which is important for hydrotest experiments, and the spatial resolution can achieve ~100 μm.     

Thermal Fatigue Study on the Divertor Plate Materials

Thermal fatigue property of the divertor plate is one of the key issues that governs the lifetime of the divertor plate.Taking tungsten as surface material,a small-mock-up divertor plate was made by hot isostatic press welding (HIP),A thermal cycling experiment for divertor mock-up was carried out in the vacuum,where a high-heat-flux electronic gun was used as the thermal source,A cyclic heat flux of 9MW/m^2 was loaded onto the mock-up,a heating duration of 20s was selcted,the cooling water flow rate was 80ml/s.After 1000 Cycles,the surface and the W/Cu joint of the mock-up did not show any damage,The SEM was used to analyze the microstructure of the welding joint,where no cracks were found also.     

Experimental Investigation of Flow Separation Control Using Dielectric Barrier Discharge Plasma Actuators

Influence of plasma actuators as a flow separation control device was investigated experimentally. Hump model was used to demonstrate the effect of plasma actuators on external flow separation, while for internal flow separation a set of compressor cascade was adopted. In order to investigate the modification of the flow structure by the plasma actuator, the flow field was examined non-intrusively by particle image velocimetry measurements in the hump model experiment and by a hot film probe in the compressor cascade experiment. The results showed that the plasma actuator could be effective in controlling the flow separation both over the hump and in the compressor cascade when the incoming velocity was low. As the incoming velocity increased, the plasma actuator was less effective. It is urgent to enhance the intensity of the plasma actuator for its better application. Methods to increase the intensity of plasma actuator were also studied.     

Continued Study on Hohlraum Radiation Source with Approximately Constant Radiation Temperature

An experiment was performed on the Shenguang III prototype laser facility to continue the study on hohlraum radiation source with approximately constant radiation temperature using a continuously shaped laser pulse.A radiation source with a flattop temperature of about130 e V that lasted about 5 ns was obtained.The previous analytical iteration method based on power balance and self-similar solution of ablation was modified taking into account the plasma movements and it was used to design the laser pulse shape for experiment.A comparison between experimental results and simulation is presented and better agreement was achieved using the modified method.Further improvements are discussed.     

Filament Discharge Phenomena in Fingerprint Acquisition by Dielectric Barrier Discharge

In this paper, the dielectric barrier discharge fingerprint acquisition technique is introduced. The filament discharge phenomena were observed in the process of fingerprint acquisition. The filament discharge reduced the quality of fingerprint images. Obviously, it was necessary to eliminate streamer discharges in order to get good fingerprint images. The streamer discharge was considered to be the cause of the filament discharge in the experiment. The relationship between the critical electric field and the discharge gap was calculated with the Raether＇s model of streamer discharge. The calculated results and our experiment proved that it would be difficult for the streamer discharge to occur when the discharge gap was narrow. With a narrow discharge gap, the discharge was homogeneous, and the fingerprint images were clear and large in area. The images obtained in the experiment are very suitable for fingerprint identification as they contain more information.     

Image fusion using MIM software via picture archiving and communication system

The preliminary studies of the multimodality image registration and fusion were performed using an image fusion software and a picture archiving and communication system (PACS) to explore the methology,Original image voluminal data were acquired with a CT scanner,MR and dual-head coincidence SPECT,respectively.The data sets from all imaging devices were queried,retrieved,transferred and accessed via DICOM PACS.The image fusion was performed at the SPECT ICON work-station,where the MIM(Medical Image Merge)fusion software was installed.The images were created by reslicing original volume on nthe fly.The image volumes were aligned by translation and rotation of these view ports with respect to the original volume orientation.The transparency factor and contrast were adjusted in order that both volumes can be visualized in the merged images.The image volume data of CT,MR and nuclear medicine were transferred.accessed and loaded ia PACS successfully.The perfect fused images of chest CT/^18F-FDG and brain MR/SPECT were obtained.These results showed that image fusion technique using PACS was feasible and practical,Further experimentation and larger validation studies were needed to explore the full potential of the clinical use.     

Experimental Study of Two-Neutron Correlation in ~8He~+

A neutron detector array was used in a breakup reaction experiment at RIKEN with an 82.5 MeV/u 8He beam impinging on the CH2 and C targets. The array was calibrated using the cosmic ray, the γ ray from the 6 He+Pb reaction and the mono-energetic neutrons from the 7Li(p, n)7Be(g.s.+0.43 MeV) reaction. The position resolution, timing resolution and neutron detection efficiency were obtained accordingly. Cross-talk rejection conditions were developed based on analysis of the data taken from the 7Li(p, n) 7Be(g.s.+0.43 MeV) test experiment, and finally a preliminary two-neutron correlation function for the 8 He breakup reaction was investigated.     

Deposition of SiOx on Metal Surface with a DBD Plasma Gun at Atmospheric Pressure for Corrosion Prevention

In this study, SiOx films were deposited by a dielectric barrier discharge （DBD） plasma gun at an atmospheric pressure. The relationship of the film structures with plasma powers was investigated by Fourier transform infrared spectroscopy （FTIR）, and scanning electron microscope （SEM）. It was shown that an uniform and cross-linking structure film was formed by the DBD gun. As an application, the SiOx films were deposited on a carbon steel surface for the anti-corrosion purpose. The experiment was carried out in a 0.1 M NaCl solution. It was found that a very good anti-corrosive property was obtained, i.e., the corrosion rate was decreased c.a. 15 times in 5% NaCl solution compared to the non-SiOx coated steel, as detected by the potentiodynamic polarization measurement.     

Isotope distribution of iridium in the interaction of 47MeV／nucleon^12C with^197Au

Thick gold targets were bombarded with 47 MeV/nucleon ^12C ions and the radioactive isotopes of iridium and platinum were produced through the multi-nucleon transfer reactions. The production cross-sections of iridium isotopes in the reactions have been determined by a combination of radiochemical separation and off-line γ-ray spectroscopy technique. The obtained Ir isotope distribution was compared with those obtained in other experiment as well as calculated by the statistical model.     

Triaxial Shape in ^129Ce

The experiment was carried out in the HI-13 tandem accelerator at the China Institute of Atomic Energy. The high spin states of ^129Ce have been populated via heavy-ion fusion evaporation reaction ^96Mo（^37Cl, 1p3n）^129Ce. The beam energy is 155 MeV and the target is of thickness 1.0 mg/cm^2, mounted on a 19 mg/cm^2 Pb backing. The T-ray from the evaporated residues were detected with an array consisting of fifteen Compton suppressed HPGe-BGO spectrometers.     

Characteristics of Coaxial Vircator in Three Specific Configurations

As a novel vircator device, the coaxial vircator can attain much higher efficiency than the common virtual cathode oscillator. In this paper, coaxial vircators in three specific configurations are studied to describe the efficiency and frequency characteristics and their dependence on geometric parameters. The PIC (Particle in Cell) simulation results show that a power efficiency over 11% can be obtained from the coaxial vircator with a finite inner anode conductor, and a narrow-band output can be achieved. A direct-coupled coaxial vircator has a slightly lower efficiency of about 8%, but in this configuration the efficiency is not strongly dependent on the geometry parameters. The introduction of a reflecting cavity can effectively improve the efficiency under certain parameters. Meanwhile, the research results also indicate that improper cavity parameters will countervail some inherent advantages of the configuration with a finite inner conductor, leading to lower efficiency than that of the direct-coupled one. Meanwhile, an experiment was also carried out to testify the simulation results, and a power efficiency over 3% was obtained from the direct-coupled coaxial vircator.     

Diagnostics of First Wall Materials in Device by Polarization-Resolved a Magnetically Confined Fusion Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy （LIBS） is a powerful analytical tool for real- time diagnostics and detection of multiple elements deposited at the first wall of magnetically confined plasma ft~sion devices. Recently, we have tested LIBS in our laboratory for application to in situ real-time diagnostics in the fusion device EAST. In this study, we applied polarization- resolved LIBS （PR-LIBS） to reduce the background continuum and enhance the resolution and sensitivity of LIBS. We used aluminium （A1） （as a substitute for Be） and the first wall materials tungsten （W） and molybdenum （Mo） to investigate polarized continuum emission and signal-to- background ratio （SBR）. A Nd：YAG laser with first, second and third harmonics was used to produce plasma. The effects of the laser polarization plane, environmental pressure and polarizer detection angle were investigated. The spectra obtained without using a polarizer （i.e. LIBS） were compared with those obtained with a polarizer （PR-LIBS）. Distribution of emission spectral intensity was observed to follow Malus＇ law with respect to variation in the angle of detection of the polarizer. The spectra obtained by PR-LIBS had a higher SBR and greater stability than those obtained by LIBS, thereby enhancing the reliability of LIBS for quantitative analyses. A comparison of A1, Mo and W showed that W exhibited a higher continuum with stronger polarization than the low-Z elements.     

Experimental Investigation on Electromagnetic Attenuation by Low Pressure Radio-Frequency Plasma for Cavity Structure

This paper reports on an experiment designed to test electromagnetic(EM)attenuation by radio-frequency(RF)plasma for cavity structures.A plasma reactor,in the shape of a hollow cylinder,filled with argon gas at low pressure,driven by a RF power source,was produced by wave-transmitting material.The detailed attenuations of EM waves were investigated under different conditions:the incident frequency is 1-4 GHz,the RF power supply is 13.56 MHz and1.6~(-3) k W,and the argon pressure is 75-200 Pa.The experimental results indicate that 5-15 d B return loss can be obtained.From a first estimation,the electron density in the experiment is approximately(1.5-2.2)×1016m~(-3)and the collision frequency is about 11~(-3)0 GHz.The return loss of EM waves was calculated using a finite-difference time-domain(FDTD)method and it was found that it has a similar development with measurement.It can be confirmed that RF plasma is useful in the stealth of cavity structures such as jet-engine inlet.     

A compact gamma-ray detector using wavelength-shifting fibers coupled to YAP scintillation crystal

The performance of a compact position sensitive gamma-ray detector based on wavelength-shifting fibers coupled to YAlO3：Ce scintillation crystal was evaluated using a Monte-Carlo simulation method. The simulation model has been setup using the GEANT4 codes. Compared with the gamma-ray detector based on the YAlO3：Ce scintillation crystal coupled to Hamamastu R2486 position sensitive photomultiplier tube, the results indicate that the gamma-ray detector based on wavelength-shifting fibers readout has good position linearity, good spatial resolution and larger effective field of view. The image and point spread function of measured point were presented. The spatial resolution response as a function of position was obtained. The factors influencing spatial resolution and position linearity were discussed.     

Experimental Results of IBW Heating on the HT-7 Tokmak

Ion Bernstein waves (IBWs) have been proposed to be useful for heating and improving transport in tokamak plasmas. An Ion Bernstein wave heating experiment using different frequency (27 MHz and 30 MHz) was carried out on HT-7 superconducting tokamak in recent experiments. At a frequency of 30 MHz, ne peaked and Hα dropped have been pervasively observed,τp was improved by a factor of 2～4, and τe increased by a factor of 1～1.5. An obvious confinement of particle was observed during the IBW pulse. At 27MHz, both global and localized electron heating were observed depending on the location of the ion resonant layer by changing Bt.Central electron heating effect was obtained in the global heating mode and electron temperature strongly increased near the 2 ΩD resonant layer for localized heating mode.     

Performance of beam size monitor based on Kirkpatrick–Baez mirror at SSRF

High-energy photon source(HEPS) is a 6 GeV ultralow emittance storage ring light source to be built in Beijing, China. Both the horizontal and vertical beam sizes of the HEPS storage ring are below 10 lm. It is a challenge to measure such a small beam size in both directions. To this end, measurement by a Kirkpatrick–Baez(KB) mirror imaging system was evaluated. A test KB system for the Shanghai Synchrotron Radiation Facility storage ring was designed and tested. Two crossed cylindrical mirrors were used to image the dipole source point. Both mirrors can be moved in and out so that the monitor is interchangeable with the original X-ray pinhole monitor. The aberration and point spread function, which would cause image blur, were evaluated. A beam-based calibration scheme was used by varying the beam size with different quadrupole settings and fitting them with the corresponding theoretical values.We updated the original X-ray camera with a new camera having a 5-lm-thick LuAG/Ce scintillator, and the imaging result shows greatly decreased image blur.     

Development of an ultrafast detector and demonstration of its oscillographic application

A dilation X-ray detector(DIXD) based on time dilation and microchannel plate(MCP) gated technology has been reported. The DIXD passes a driving pulse along the transmission photocathode(PC) to obtain a dilated electron signal and finally achieves a high time resolution of 12 ps. Furthermore, the waveform of the PC driving pulse can be obtained using the DIXD, and a DIXD oscillographic function can be obtained. An experiment is presented to demonstrate the DIXD oscilloscope. The waveform of the ...