Ion Cyclotron Resonance Heating In KMAX Tandem Mirror

As a promising fusion reactor,magnetic mirror has obtained great progress in physics understanding and engineering in 1950s-1980s.As the concept of kinetic-stabilized axi symmetric tandem mirror was proposed and confirmed in experiments in recent years,,the feasibility of mirror approach to fusion neutron source or even fusion reactor continues to grow.The KMAX tandem mirror,as the first axisymmetric tandem mirror device in China,is devoted to the study of stability and confinement of the axisymmetric configuration.The use of ICRH as the main heating method on KMAX lays the foundation for the diagnostics,confinement and instability studies.The home-made ICRH system includes two RF sources with the output power of 100kW and two RF antennas installed in the central cell of KMAX.The pre-amplifier of the RF source is a 2kW push-pull amplifier based on MOS tubes while the power amplifier adopts the class C amplifier circuit which is featured by zero static power and high power efficiency.The difference between the frequencies of the two RF sources,which are 800kHz and 750kHz respectively,is set on purpose to avoid the interactions between them.The double half turn antenna and the half turn antenna are installed at the two sides of the midplane of central cell to launch slow wave for heating.This thesis describes the design,construction and testing methods and processes of the RF sources and antennas,including the parameters of the key parts and matching box.Ion cyclotron wave heating in the magnetic beach is the typical heating method for mirror devices,in which the ion cyclotron wave is launched and absorbed at different axial positions.Ring cusp configuration and diverging magnetic field are formed in the anchor cells and the expanders respectively by adjusting the magnetic field power supply,which is based on super capacitor modules.Target plasma with a density of?1× 1018m-3 and a radius of 15cm are formed in the central cell by the two hydrogen washer guns installed at the two ends of the device.In the ICRH experiments,with a total power of 100 kW radiated by double half-turn(DHT)and half-turn(HT)antennas,the plasma diamagnetism increases by 15-fold,with a corresponding peak ???2%,density?1.5 x 1018m-3,and total temperature?60 eV.The effects of the magnetic configuration on resonance heating and wave emission are studied by varying the magnetic fields at the midplane and at the location of the antennas,respectively;the results confirm that the magnetic beach configuration is key to successful ICRF heating.The axial phase speed measurements suggest that the excited wave is a slow wave in the plasma core and a fast wave at the edge.