A co-axial gun source injects a plasma of 1–10% β into a series of mirror cells. When the linked-quadrupole minimum – |B| magnetic mirrors are used, the plasma appears to be MHD-stable with smooth decays of ∼ 100 μs. In contrast, for the simple mirror configuration, the plasma is rapidly lost, suggesting that MHD-instability is present.
The improvements in multi-mirror confinement due to an asymmetrically applied ion cyclotron resonance field (ICRF) are determined. The resonance field is used to selectively reflect ions that travel away from the centre of the device, thus creating a net ion drift towards the centre. The ICRF effects in heating and scattering the ions and modifying the loss cone geometry are determined in detail. A onedimensional, non-ignited (finite Q = fusion power/recirculating power) model of a multiple-mirror system is used to investigate confinement. Various scaling laws are numerically derived and compared to those of a symmetric system without ICRF. Radial diffusion due to classical collisions and ICRF effects is calculated. A 21-cell machine with a peak field of 280 kG and Q = 5 is reduced from 845 m to 580 m in length with the addition of the asymmetric ICRF. The total fusion power generated by the system is reduced from 8 to 6.3 GW.
Boron ions are universally used as a p-type dopant for ion implantation of silicon wafers. In today’s technology, ions are produced from gases in a hot filament magnetron plasma, known as the Freeman ion source, using BF3 as a feedstock. Two problems are that the hot filament corrodes in the fluoride environment and the BF3 is quite toxic. In order to overcome these limitations, we have developed a cold cathode magnetron source which uses a conductive boride cathode liner (B4C and B6Si have been used successfully), and a nontoxic gas feed (such as CF4 or SF6), which produces boron ion fraction yields as high as 15% in beam extraction experiments performed on a low voltage ion source test stand. This is comparable to the performance obtained using a Freeman source and BF3 feed gas.
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