Tornado type closed magnetic trap for an ECR source

We propose to use a Tornado type closed magnetic trap for creation of a source of mul-ticharged ions with plasma heating by microwave radiation. Plasma loss in closed traps is deter-mined by diffusion across the magnetic field, which increases substantially plasma confinement time as compared to the classical mirror trap [1]. We propose to extract ions with the aid of additional coils which partially destroy the closed structure of the magnetic lines in the trap, but don not influence the total confinement time. This allows for producing a controlled plasma flux that depends on the magnetic field of the additional coil. The Tornado trap also possesses merits such as an opportunity to produce high magnetic fields up to 3 T, which makes possible heating and confinement of plasma with a high density of electrons; plasma stability to magneto-hydrodynamic perturbations because the magnetic field structure corresponds to the "min B" configuration; and relatively low costs. All estimates and calculations were carried out for the Tornado 322 pulse installation [2]. The trap had the following parameters: maximal magnetic field 2.8 T, trap diameter 350 mm, magnetic field pulse duration (halfwidth) 7 ms, and pulse repetition rate 0.01. We propose a scenario of plasma heating using sequential switching on of two generators at the frequency of 2.45 GHz for producing initial plasma and at the frequency of 30 GHz for its heating [3]. Ion distribution over charge states was calculated for Argon plasmas within the framework of a 0-dimensional nonstationary set of differential equations for ionization balance, which took into account transverse plasma diffusion as well as recombination and charge exchange in the case of a uniform source of neutral gas. It is shown that, by the end of the magnetic field pulse, ion dis-tribution over charge states may reach a maximum at Ar+15 for the plasma density of 1013 cm-3. To conclude, an ECR source of multicharged ions based on a Tornado type trap is a highly promising and feasible pulse source that may be fabricated in the near future.