Mao Wang

Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis.

The masses of ten proton-rich nuclides, including the N=Z+1 nuclides ⁸⁵Mo and ⁸⁷Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical x-ray bursts. Surprisingly low α separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.

First isochronous mass measurements with two time-of-flight detectors at CSRe

Isochronous mass spectrometry (IMS) established in heavy-ion storage rings has proven to be a powerful tool for mass measurements of short-lived nuclides. In IMS, the revolution times of stored ions should be independent of their velocity spread. However, this isochronous condition is fulfilled only in the first order and in a small range of revolution times. To correct for non-isochronicity, an additional measure of the velocity or magnetic rigidity of each stored ion is required. For this purpose two new time-of-flight (TOF) detectors were installed in one of the straight sections of the experimental cooler storage ring in Lanzhou. It is expected that the resolving power of the IMS will significantly be improved with such a double-TOF arrangement. The double-TOF system was tested in a recent experiment with the Kr-78 fragments. Some of the experimental results are presented in this contribution.

Design of a Multijunction Antenna Unit for EAST Lower Hybrid Current Drive

A multijunction antenna unit has been designed and will be used to fabricate the new 4.6GHz Lower Hybrid Current Drive (LHCD) launcher for the long pulse operation of the Experimental Advanced Superconducting Tokamak (EAST). In this paper, the construction and design method of the multijunction antenna unit are described, and then the reflection coefficients of the unit with the matched load and with the plasma load are analyzed and discussed respectively by using High Frequency Structure Simulator (HFSS) code and by using numerical calculation based on linear coupling theory. The simulation result shows that the return loss of the antenna unit keeps below −25dB in a bandwidth of 100MHz and the power is distributed equally in the secondary waveguides of the unit. Numerical calculation result also shows that the unit has good coupling property in a wide range of tokamak plasma parameters.Copyright

Design of the klystron filament power supply control system for EAST LHCD

A filament is a critical component of the klystron used to heat the cathode. There are totally 44 klystrons in experimental advanced superconducting tokamak (EAST) lower hybrid current drive (LHCD) systems. All klystron filaments are powered by AC power suppliers through isolated transformers. In order to achieve better klystron preheat, a klystron filament power supply control system is designed to obtain the automatic control of all filament power suppliers. Klystron filament current is measured by PLC and the interlock between filament current and klystron high voltage system is also implemented. This design has already been deployed in two LHCD systems and proves feasible completely.

High power continuous wave microwave test bench at 4.6 GHz for experimental advanced superconducting tokamak

The lower hybrid current drive (LHCD) is an effective approach for auxiliary heating and non-inductive current drive in the experimental advanced superconducting tokamak. The 6 MW/4.6 GHz LHCD system is being designed and installed with twenty-four 250 KW/4.6 GHz high power klystron amplifiers. The test bench operating at 250 KW/4.6 GHz in continuous wave mode has been set up, which can test and train microwave components for the 6 MW/4.6 GHz LHCD system. In this paper, the system architecture and software of the microwave test bench are presented. Moreover, the test results of these klystrons and microwave units are described here in detail. The long term operation of the test bench and improved performance of all microwave component samples indicated that the related technologies on test bench can be applied in the large scale LHCD systems.

The design of intelligent fault diagnosis system for high power microwave systems

Faults often cause serious damages on high power microwave system (HPMS). An intelligent diagnosis system is introduced in this paper. It helps operators in monitoring and diagnosing abnormal situations of HPMS. The HPMS architecture, the structure of the intelligent diagnosis system, the knowledge base, and the inference process are presented in detail. A diagnostic tree of HPMS is built by domain experts, and the diagnostic priorities of nodes in the tree are determined based on a fuzzy group multiple attribute decision making method. QNX operation system has been used in developing the proposed diagnosis system. Preliminary test has been carried out in actual engineering project, and satisfactory results were achieved.

A Fault Diagnosis Expert System for LHCD System on EAST

Lower hybrid current drive (LHCD) is an efficient method for noninductive current drive in fusion devices. The LHCD system has been constructed on the Experimental Advanced Superconduct Tokamak (EAST). It is a complex system due to lots of devices involved. Each device has possibility of faults, which causes great difficulties in fault diagnosis. Consequently, a fault diagnosis expert system is essential for a safe and steady operation of the LHCD system. This paper proposes an expert system called LFDES (lower hybrid current drive fault diagnosis expert system) to aid operators in diagnosing and analyzing abnormal situations of the LHCD system. After a brief description of the structure of LHCD system, the LFDES architecture, the knowledge base, the inference engine and the database are presented in detail. Based on an empirical knowledge, the diagnostic tree of LHCD system is built. A fuzzy group multiple attribute decision making method is used to determine the priorities of nodes in the diagnostic tree. KDevelop tool, QT Designer tool and Linux operation system have been used in developing the proposed system. In the study, satisfactory results were obtained. The analyses of the results indicated that LFDES can provide reliable, efficient and economical service.Copyright