Full Title Creation of Highly-Charged Ions in the ECR Discharge Sustained by Millimeter-Wave Radiation Tech Area / Field

PHY-PFA: Physics / Particles, Fields and Accelerator Physics

MAT-SYN: Materials / Materials Synthesis and Processing

Brief Description of Technology
The sources using microwave discharge plasma sustained in an open magnetic trap under the conditions of electron-cyclotron resonance (ECR) recently have begun to be considered as prospective sources of multi-charged ions (MCI). Such ECR sources are intended primarily for ion injection into cyclotron accelerators, the efficiency of which strongly depends on the efficiency of the ion source. Materials processing by MCI appears to be a very promising area, too.

The essential increase of electron-cyclotron resonance (ECR) multiply-charged ion (MCI) source efficiency (that is, the increase of the average charge number and current of ion beams) leads to the possibility of achieving denser plasma, and its transfer to the so-called quasi-gas dynamic regime of the plasma confinement in mirror traps as a result of pumping with higher frequency. The first experimental investigation of ion charged state distribution in a pulsed ECR source of MCI with pumping by millimeter wave radiation of a powerful gyrotron were carried out in IAP RAS.

Millimeter wave radiation with a maximum power of W=130 kW, frequency of f=37.5 GHz and pulse duration of up to 1.5 ms was focused along magnetic lines into the trap with a mirror ratio of 3,3. Gas pressure was tuned by a pulsed inlet and maintained on level at more than 3´10^-5 Torr. The plasma density measured by cutting off diagnostic millimeter waves exceeded 2 ´ 10¹³ cm^-3. The ions that flew freely along the axis of the trap were investigated by a two-step ion analyzer (magnetic and electrostatic analysis) with a mass resolution of 3, and by a Langmuir plate probe. If W=130 kW, the position of the charged state distribution maximum corresponded to an argon charge of (+11)-(+12), whereas in the modern ion sources (with pumping by microwave power of centimeter wavelength) the distribution maximum corresponded to a charge of (+8). Total ion saturation current density of the probe achieved 2 A/cm². Thus, high plasma density (more than the order of magnitude exceeding density in traditional sources) and high ion current in our system provide the hope of achieving MCI beams with previously unattainable currents.

Legal Aspects
None.

Special Facilities in Use and Their Specifications
None.

Scientific Papers
S.V. Golubev, S.V. Razin, V.G. Zorin. “Investigation of ion charge state distribution in the ECR source with pumping by gyrotron radiation,” Abst.of 3-rd Int. Workshop "Strong Microwaves in Plasmas," (Nizhgny Novgorod, Aug. 1996), D-14.

Дата добавления: 2015-07-20