Yasuo Yamashita

Production of high-current large-area H/sup -/ beams by a bucket-type ion source equipped with a magnetic filter

A negative-ion-based neutral beam injection (NBI) system is planned for plasma heating of the Large Helical Device (LHD). We have developed a negative ion source, which is 1/3 the scale of the source for the NBI. A magnetic filter held was generated by external permanent magnets to lower the electron temperature in a large-area bucket plasma source (35 cm/spl times/62 cm) for efficient H/sup -/ production. We investigated the magnetic field configuration and found a low electron temperature high density plasma ( 15 A: 1/3 current of LHD ion source). Based on the results, we are designing a negative ion source for the LHD.

Advanced microwave ion source for 100 mA-class SIMOX ion implantation

To produce SIMOX wafers with high throughput, a compact and long lifetime microwave ion source for 100 mA-class oxygen ion implantation was newly developed. The ion source operated stably for more than 3 months with no maintenance under the beam extraction condition of 150 mA at 50 kV. When the source was installed in a SIMOX ion implanter, operation test showed that the ion source is suited to 100 mA-class ion implantation, giving volume production of high quality SIMOX wafers.

MONTE CARLO SIMULATION OF TRANSMISSION PROBABILITY IN CRYOPUMPS FOR NEUTRAL BEAM INJECTORS

Neutral Beam Injector (NBI) with negative ion source is under development as one of the most promising heating devices for achieving the objective plasma parameters in the Large Helical Device (LHD) at NIFS. This paper considers the development of high speed cryopumps for the NBI in the LHD. A new type of louvre blind cryopump having parallel 80 K louvre blinds and 3.7K cryopanels, located parallel to the 80 K louvre blinds, is proposed. At the ratios of B/C = 0.92 and D/B = 1.2, the transmission probability of this advanced type is calculated to be 0.72 which means the cryopump system with this louvre blind type can theoretically attain a high pumping speed.

DEVELOPMENT OF A PARALLEL-LOUVRE-BLIND TYPE CRYOPUMP FOR FUSION REACTORS

As a new type of actual sized cryopump with high pumping speed, a parallellouvre-blind type cryopump of a rectangular cross section with opening distance B, width C and depth D, is proposed and is produced as a trial pump unit designed to actual size. The influence of pump depth size ratio Rd(=D/B) and number of secondary cryopanels on the transmission probability Pbc of the pump unit is calculated by Monte Carlo simulation and the hydrogen pumping speed is measured by experiments. The following results are obtained: (1) The transmission probability of a cryopump designed with dimensional ratio of Rd=1.3, is calculated to be 0.66 at ratios of Rc(=B/C)=0.88, which means that hydrogen pumping speed of this sized cryopumps can attain 294m3s−1/m2per opening area. (2)The experimental hydrogen pumping speed of the trial pump unit with 29 secondary cryopanels, is measured to be 295m3s−1/m2.