Operation of a 0.2–1.1 keV ion source within a magnetized laboratory plasma

H Boehmer,D Leneman,L Zhao,D Edrich,W W Heidbrink,R Mcwilliams

doi:10.1063/1.1646766

Abstract

To study the physics of energetic ions in magnetized plasma, a rf ion beam is inserted into the 1 kG, ∼3 eV, ∼1012 cm−3 plasma produced by the upgraded LArge Plasma Device (LAPD). The commercial 100–1000 eV argon source normally operates in an unmagnetized microelectronics production environment. Successful operation in the LAPD requires numerous modifications, including electrical isolation of the source housing, relocation of the matching network for the rf, reduction of the gas pressure, pulsed operation to avoid overheating, and care to preserve current neutralization in the presence of a strong magnetic field. With these modifications, a ∼500 eV, milliampere beam that propagates axially more than 6 m is obtained.

Highlights

Fast ionsFIsthat have energies much larger than the thermal, bulk-ion population are pervasive in astrophysical, space, and fusion plasmas
FI physics studies are challenging in both space and laboratory plasmas
The objective of the work reported here is to develop a FI source that can be inserted into a relatively cool laboratory plasma that is accessible to probes and FI diagnostics

Summary

INTRODUCTION

Fast ionsFIsthat have energies much larger than the thermal, bulk-ion population are pervasive in astrophysical, space, and fusion plasmas. The objective of the work reported here is to develop a FI source that can be inserted into a relatively cool laboratory plasma that is accessible to probes and FI diagnostics. As illustrated in Fig. 1͑b, the properties of the source are characterized on a smaller0.3-m-diam, 3.6-m-longtestbed at the University of California, IrvineUCI. This testbed is a mirror machine; the ion source is mounted along the axis beyond the field coils in a region with a strong field gradient. ͑7͒ Small overall size to minimize the perturbation of the background plasma; no magnetic materials A filament creates a low-density background plasma that provides neutralizing electrons for the ion beam.

SOURCE DESCRIPTION AND BASIC OPERATION

BEAM ENERGY AT RELATIVELY LOW PRESSURE

EFFECT OF MAGNETIC FIELD

USE OF A GRADIENT FIELD

FUTURE IMPROVEMENTS