Initial operation of a plasma isotope separation system

Summary form only given. A plasma-based isotope separation system has been installed at Theragenics/sup TM/ Oak Ridge, TN facility and has recently been placed into operation. This facility is designed to separate stable isotopes of metallic elements utilizing the Plasma Separation Process´ (PSP). In this process, electron cyclotron resonance heating using a microwave power source forms the plasma. Neutral particles of feed material to be separated are introduced by sputtering a feedstock plate and are ionized by the plasma electrons. Metal ions drift through a highly uniform magnetic field and are subject to ion cyclotron waves tuned to excite a specific isotope mass. The excited ions are separated from low energy off-resonant ions in a louver shaped collector structure. The facility utilizes a 2 T superconducting magnet with a 1 m bore and uniform field length of 5 m. This magnet is a pool-boiling type filled with 5500 L of liquid helium. The plasma chamber inside the bore of the magnet is maintained at high vacuum by two large diffusion pumps and is backfilled with low pressure argon gas to initialize the sputtering process. A 28 GHz CW gyrotron system capable of operating at up to 200 kW provides plasma ionization. Power is transmitted from the gyrotron to the vacuum chamber through a smooth-wall 63.5-mm waveguide and large-radius corrugated bends. A double disk cooled waveguide window is situated inside the vacuum to permit a high-field launch point. The plasma column formed inside the magnet is /spl sim/ 0.4 m diameter and 6 m long. Typical plasma parameters maintained are 5/spl times/10/sup 17/ m/sup -3/ electron density and < 10 eV electron temperature. Feedstock material is introduced into the plasma by sputtering a source plate placed near the electron cyclotron resonance zone and biased to typically -2 kV. The sputtering source power Supply is highly regulated and capable of 160A source current. Sputtered neutrals are ionized in the electron cyclotron z- ne and enter a long uniform drift region where a 4 conductor helical antenna surrounds the plasma. Ion cyclotron drive power is applied to the antenna through a phased matching box that provides rotating electric field for optimum coupling to the ion cyclotron wave. The ICRF drive system is designed to operate from 100-500 kHz to cover a range of elements and generates up to 200 kW CW. A set of scannable Langmuir probes and residual energy analyzer probes are used to diagnose the plasma density and ion energy profile. A microwave interferometer is used to measure and control the average plasma density. Operational performance will be discussed. A number of isotope separation projects are being considered for a variety of medical, scientific and industrial customers.