In an ion source, a rear reflector 10 is electrically insulated from both a plasma production vessel 2 and a filament 6. The rear reflector 10 and an opposed reflector 8 are electrically connected. Further, a DC bias power supply 32 is a power supply individuated from a filament power supply 24 and an arc power supply 26. The DC bias power supply 32 is placed for applying a bias voltage V.sub.B between the opposed reflector 8 and the rear reflector 10 and the plasma production vessel 2 with both the reflectors 8 and 10 as negative potential.

An indirect hot cathode ion source for use in an ion implanter is disclosed. The ion source can be constructed by a chamber formed of two endwalls, two sidewalls, a top and a bottom wall defining a cavity therein for producing plasma ions. An opening, or a slit through one sidewall of the chamber, is used for ejecting the plasma ions therethrough. Inside the ion source chamber, an anode, or an anti-cathode, is positioned in close proximity to a first endwall of the chamber, while a cathode is positioned in close proximity to a second endwall of the chamber opposing the first endwall. The cathode is constructed by a filament for passing an electrical current therethrough, and a filament shield of cylindrical shape surrounding the filament spaced apart from an inner periphery of an opening in the second endwall. The inner periphery of the opening in the second endwall is provided with a torroidal-shaped recess in and along an inner periphery of the opening adjacent to the cavity of the chamber such that deposition of materials on the inner periphery of the opening and electrical shorting or arcing with the filament shield can be avoided.

According to the present invention, an ion beam flux measurement device may include an exposure area, a measuring area disposed a predetermined distance from the exposure area, a moveable target having at least a portion thereof disposed within the exposure area, an actuator coupled to the target, and a radioactive emission detector disposed within the measuring area. The radioactive emission detector also may include a viewing portion and may detect beta rays or gamma rays. The actuator may include a feed roller and a take up roller. The target preferably may include a foil coupled to and extending between the rollers. The foil may be continuously moveable between the rollers or may be moveable in a stepwise manner. The ion beam flux measurement device also may include a collimator, preferably including a high density material when beta rays are to be detected, coupled to the radioactive emission detector. A secondary liner may be coupled to the collimator. At least a portion of the ion beam may be diverted to the exposure area and away from a normal path of the ion beam. The portion of the ion beam may be deflected with an electric charged particle deflector or a magnetic charged particle deflector.

An ion source is described for use with conventional and modified ion implantation equipment to improve safety and increase efficiency when generating radioactive ion beams. The ion source is particularly useful with radioactive species that are volatile at room temperature or react with air molecules to form volatile compounds. One or more components of the ion source, such as a cathode, an anode, an electrostatic electron reflector, a vaporizer, a sputter target, a gas line or a plasma chamber, may be mounted on extensible probes within radiation shielded sealable transfer containers. Other components of the ion source may be fixed in a vacuum chamber, which may have one or more valved openings corresponding to the sealable openings in the transfer containers. The components on the probes may be extended into position inside the vacuum chamber for operation of the ion source, and may be retracted into the sealable transfer containers and transported to an area for servicing or repair.

Making a sputter cathode for applying a radioactive material includes obtaining a wafer containing a base material having a stable precursor dissolved therein. The base material is transmutable into a material having a relatively short atomic half-life. The wafer is atomically activated to transmute a portion of the stable precursor into a radioactive material. The base material may be silicon or germanium. The stable precursor may be .sup.31 P and the radioactive material may be .sup.32 P. Atomically activating the wafer may include exposing the wafer to a source of thermal neutrons by, for example, placing the wafer in a high-flux nuclear reactor for approximately four weeks.