Search

A radioactive target/ion source for material research has been developed at China Institute of Atomic Energy, China. With a proton ion beam from the HI-13 tandem as the primary beam, the low intensity radioactive ion beam is generated on line. The first aim of the source is to produce a radioactive ion beam of 62Zn+ which will serve as nuclear probe in material research. The main features and current status of the source are presented in this article. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Develops the off-line experimental techniques and apparatuses for the direct measurement of effusive-flow delay-times and ionization efficiencies of chemically reactive element in high-temperature target/ion sources. Lists of apparatuses used in the experiment; Usage of molecular feed compounds containing stable complements of the radioactive nuclei.

Due to the difficulty in accurately detecting the health status of cable joints, a new method of identifying and assessing the cable joints' health status based on traveling wave reflection is proposed. By transmitting nanosecond pulse signals at the head end of the cable, the health status characteristics of the cable joints can be obtained, and the noise reduction of the measurement signals is performed by the wavelet function to identify the reflected wave at the joint and the end of the cable. The equivalent circuits and simulation models of contact resistance and leakage resistance are established, and the contact resistance and leakage resistance of the cable joints are calculated according to the amplitude and phase of the reflected signals at the joint and the end of the cable. By comparing with the resistance when the joint is in healthy operation, any measured parameter exceeding the corresponding standard is considered a joint fault. Simulations and test results show that the method can accurately identify the reflected signals of the cable joints in different operating states, and with changes in joint health, clear regular features can be extracted from the reflected signals, and the quality and health of the joints can be determined. The traveling wave method can be used to detect cable joint faults and provide an early warning of defects, which provides a new idea for online monitoring and early warning of cable joints in both theory and engineering practice.

In this paper, an image-based visual servoing (IBVS) controller with a 6 degree-of-freedom robotic manipulator that tracks moving objects is investigated using the proposed Deep Q-Networks and proportional-integral-derivative (DQN-PID) controller. First, the classical IBVS controller and the problem of feature loss and large steady-state error for tracking moving targets are introduced. Then, a DQN-PID based IBVS method is proposed to solve the problem of feature loss and large steady-state error and improve the servo precision, as the existing methods are hard to use for solve the problems. Specifically, the IBVS method is inherited by our controller to build the tracking model, and a value-based reinforcement learning method is proposed as an adaptive law for dynamically tuning the PID parameters in the discrete space, which can track the moving target and keep the servo feature in the field of the camera. Finally, compared with the different existing methods, the DQN-PID based IBVS method has merits of higher accuracy and more stable tracking, or generalization.

Robot grasping has become a very hot research field so that the requirements for robot operation are getting higher and higher. In previous research studies, the use of traditional target detection algorithms for grasping is often very inefficient, and this article is dedicated to improving the deep reinforcement learning algorithm to improve the grasping efficiency and solve the problem of robots dealing with the impact of unknown disturbances on grasping. Using the characteristic that deep reinforcement learning actively explores the unknown environment, a Gaussian parameter Deep Deterministic Policy Gradient (Gaussian-DDPG) algorithm based on the Importance-Weighted Autoencoder (IWAE) is proposed to realize the robot's autonomous learning of the grasping task. Traditional coordinate positioning methods and deep learning methods have poor grasping effects for disturbed situations (such as the movement of the target object). The IWAE algorithm is used to compress the high-dimensional information of the original visual input to the hidden space and pass it to the deep reinforcement learning network as part of the state value. Based on the classic DDPG algorithm, it smoothly adds Gaussian parameters to improve the exploratory nature of the algorithm, dynamically sets the robot grasping space parameters to adapt to the workspace of multiple scales, and finally, realizes the accurate grasping of the robot. Relying on the possible position information deviation of the visual information, the control of the grasping position by the manipulator torque information is further optimized to improve the grasping efficiency of disturbed objects.

Multiple ion beam facilities are powerful tools to simulate the irradiation effects of neutrons on relevant nuclear materials. Since hydrogen and helium are often generated in neutron irradiated materials as transmutation products and they play important roles in the defect evolution, the triple beam accelerator and transmission electron microscope link in situ facility instead of a monobeam or dual-beam facility is necessary to simulate neutron irradiation. A hydrogen-helium dual-beam ion implanter has been developed for a triple ion beam in situ facility at Xiamen University. A Penning ion source has been developed to produce H 2 + and He + simultaneously. A special system consisting of two Wien filters and an Einzel lens has been proposed to purify the species from a single Penning source and allow for the measurement of the He + /H 2 + ratio, without disturbing the accelerator settings. The detail of this dual-beam ion implanter will be introduced in detail.

The injecting time of the picosecond laser in an indirect-drive integrated fast ignition experiment was measured by using an x-ray streak camera. Despite overlapping spatially and temporally in experiments, the soft x-ray signal from the nanosecond laser ablating the inner wall of an Au hohlraum and the hard x-ray signal from the bremsstrahlung radiation of hot electrons generated by a picosecond laser were separated by different image processes by filtering and collimating the two signals differently. The time sequence between the two x-ray signals was analyzed to extract the injection time of the picosecond laser relative to the hohlraum emission. By tracking the neutron yield as a function of the injection time of the picosecond laser, a clear positive correlation between the neutron yield enhancement and the derived injection times was exhibited. The heating effect of the picosecond laser was confirmed. It is concluded that this method could be used to measure the injecting time and validate the picosecond laser injection.