Chen Zhuomin

Preliminary Engineering Design of Toroidal Field Magnet System for Superconducting Tokamak HT-7U

HT-7U is a large fusion experimental device. It will be built in the Institute of Plasma Physics of Chinese Academy of Sciences. The mission of HT-7U is to develop the scientific basis for a continuously operating tokamak fusion reactor. This paper describes only a toroidal field (TF) superconducting magnet system of HT-7U. In this paper, design criteria of conductor and stability analysis, coil winding and support structure design of magnet system, mechanical calculation and stress analysis, heat load evaluation are given.

Research of the CICC Stability by the Numerical Code Gandalf

The basic approach to computer analysis of the CICC in superconducting Tokamak HT-7U is given and discussed. We will apply a 1-D mathematical model (Gandalf) to investigate the stability of CICC at real operating modes of Tokamak. 1-D model can be directly adopted to follow the evolution of the zone when the energy input is large enough and the coil quenches. In this report, we will analyze the stability of typical CICC (including pure copper) and discuss effect of copper on the stability of CICC.

Strain Measurement on the Toroidal Field (TF) Coil Cases

The stress-strain state of the structure is a matter of interest to designer. The strain measurement of superconducting magnets at cryogenic temperature is a specific technique. Based on strain measurement of TF coil case for EAST, this paper presents a measuring technique at cryogenic temperature and on intense magnetic field. The compensation methods for both temperature and magnetic field effects of the gauges, together with the measured results are involved, and the discussions of the measured results are given in the paper.

Investigation on the Relation of CICC Stability Margin to Mass Flow Rate and Operating Temperature of Helium

To circulate supercritical helium, a differential pressure between inlet and outlet has to be applied. A differential pressure can be generated by a refrigerating compressor which forces the coolant through cooling channels. A differential pressure corresponds to a constant flow rate in a constant length. The coolant flow rate was set at different values from 0.2 to 2.8 g/s. The numerical simulation was performed using the 1-D mathematical model (Gandalf). The results of the experiment and simulation show that the larger the coolant flow rate, the higher the stability margin is. It is also showed that the shorter the cooling channel, the higher the stability margin is with the same coolant flow rate. Meanwhile, we also introduce the influence of temperature and pressure on the stability margin of CICC.

Evaluation of AC Losses for HT-7U CICC on Plasma Disruption

AC loss is one of the main issues in the design of the CICC used for PF and TF coils of superconducting tokamak. A preliminary calculation of AC loss for the designed HT-7U CICCs used for TF magnets is given in this paper. We only consider the hysteresis and coupling losses related to transversal and longitudinal kinds. In addition to the strand resistive barriers (Pb-30Sn-2Sb coating for NbTi strands), a stainless steel strip has been used inside these cables to reduce the AC loss in this kind of conductor. The available theory has enabled us to emphasize the role played by the stainless steel strip in the reduction of total AC losses in this kind of conductor. In this paper, it was shown that AC losses of cable were affected by the structure and change rate of magnetic field.

Striding Networks of Inter-Process Communication Based on TCP/IP Protocol

A mode of process/thread communication between QNX and WINDOWS operating systems in isomerous computers is described. It is proved in practice to be an entirely feasible mode with high efficiency and reliability. A socket created by Socket API is used to communicate between two operating systems.

Calculation of AC Losses of CICC for Superconducting Outsert Coils in a Hybrid Magnet

This paper is devoted to predict AC loss of cable in conduit conductor (CICC) which is of importance in the design of conductors. The consideration for the conductors design and main parameters for the magnets are introduced. In order to attain a good accuracy in the calculation of AC losses, the field distribution within superconducting outsert should be considered. Calculation of the AC losses, including hysteresis losses and coupling losses, is conducted. An emphasis is put on the hysteresis loss during the ramp up of the current to the operational current (15.3 kA) and the coupling loss of the conductor in a power-down condition for insert. The results are obtained to be 74.9 kJ and 950 J for 40 T hybrid magnets, respectively. Based on the calculation, a brief analysis of losses effect on the conductor design and the operation of magnet is given for the purpose that the capacity of the cryogenertor can be evaluated and the stability regime can be improved in our future work on the hybrid magnets.

Analysis and Calculation of AC Losses Test of EAST PF Model Coil

The poloidal field model coil (PFMC) of EAST was a large NbTi superconducting coil. The PFMC was designed and constructed by Institute of Plasma Physics, CAS, and it was tested during 2003 at our institute. One of the most important performance testing items was the AC (Alternating Current) loss. It was able to measure the AC losses by the calorimetric method. The results will be useful for the evaluation of the AC losses of the poloidal coil and provide meaningful data for future operation of the EAST device.

The Design of Circuit for Checking Short in HT-7U Superconducting Tokamak device

The tokamak HT-7U project has been funded as a Chinese national project since 1998. The main object of the project is to build a nuclear fusion experimental device with divertor configuration, which is designed by the Institute of Plasma Physics, the Chinese Academy of Sciences (ASIPP). It is a full superconducting device, consisting of superconducting toroidal field (TF) coils and superconducting poloidal field (PF) coil. During the operation of the device, the operational parameter of device should be checked by technical diagnosis. This paper describes the design of circuit for checking short between every two parts of the HT-7U device. The main contents of design include circuit of data acquisition and data processing of computer.

New CICC Design Versions with High Copper Fraction for HT-7U Tokamak

The peak fields of HT-7U TF/PF coils are designed at 5.8 T and 4.5 T, respectively. The superconducting (SC) NbTi/Cu strands for the coils have a quite low copper fraction (0.58). To increase the ratio of the limiting current Vs. critical current for the cable in conduit conductor (CICC), the first-stage subcable consists of several copper strands twisted around a SC composite one. The copper strand diameter is different from the SC one. Based on Botturas CICC design approach we take the product of total copper cross-section and wetted perimeter as one of the key design parameters to meet with stability margin requirement. The product reaches 114 cm3 for 15.5 kA TF CICC at operating temperature of 4.2 K and 139 cm3 for 15 kA PF CICC at 3.8 K to obtain stability margins of 280 and 700 mJ/cm3, respectively.