Abstract. In the early 90's, it was discovered that a Plasma Focus (PF) system self-creates a plasma-tarp in which high energy-threshold nuclear-reactions occur at high reaction rates. Short life radioisotopes (SLR)s such as *F "F, 'b, r40, '% have been genaatd (lo6 -10' per pulse} with a PF-machine using 7 kJ energy storage to produce &e plasmas jY radioactivity from the SLRs is measured with rugged, Geiger counters inserted into the PF-chamber, zmd a sp&fic SLR is identified by its half-life. The PF chamba wore discharge) is Sued with a mixture of gases that constitutes the latter plasma-target -beam system, e.g., the elements required to produce specific SLRs through nuclear mactions. In this paper, arguments are presented showing that a modest sized PF-machine, using a 50 -75 kJ fast capacitor-hank, when operated at pulse f@rencies of l-10 Hz can produce 2 10' SLRs/pulse. This paper reports the results of testing a PF as a e breeder of SLRs with dual applications for: (i) Secondary Radioactive Nuclear Beams ion-sources (2 < 35), and (ii) as a breeder of radioisotopes for biomedicine (Z I 10) and/or PET imaging.

No abstract

An effect of the oscillating acceleration of the current sheet during the compression phase in a plasma focus discharge has been observed using long (60 ns) exposure time schlieren photography. This effect had not been previously observed in experiments using exposure times of a few nanoseconds or less. A 1 J Q-switched ruby laser has been used as a source of light. The photograms are taken in dark-background schlieren with a circular stop (disk) instead of a usually used knife edge. The various acceptance ranges of refraction angle have been selected by the size of the stop and aperture in order to limit the integral of the electron density gradient along the beam within the apparatus range, which is between 3X10'* and 3X 102' cmm3. Raising the sensitivity threshold to 2X1019 cm-a (refraction angle of 4 mrad) has helped to clear the pictures by limiting their image to high gradients of density only. Using this technique and other diagnostic methods, the dynamics of 6-W, 16-kV plasma focus discharges have been investigated. These discharges were made in deuterium at 5 Torr, with a 10% decrease of the magnetic insulation at the breech. The average radial velocity of the current sheet, 5 X lo4 m/s, obtained with this effect agrees with those measured by the smear effect. The peak value of 1 X lo" m/s is consistent with results received with magnetic probes. The electron density gradient has been determined for several instants; its maximum value at the pinch is (1.2?0.2)X1021 cmm4. 8

A MJ-Class Dense Plasma Focus (DPF) facility, is being designed to develop the technology needed for lasma f c c xtype magnetoplasmadynamic (MPD) thrusters.' The facility will be capable of studying various commercial appli the plasma focus also, such as soft x-ray lithography. ity will be located at the University of Illinois, Champaigd Urbana campus. The ultimate objective is to demonstrate the feasibility and attractiveness of the plasma focus MPD c o c c q t for very high specific-impulse space propulsion. Studies include scaling experiments up to and including the 1-MJ level an3 experiments using a gas-injected plasma focus, such as required in the hard vacuum cnvironment of space.The plasma focus thruster differs from the conventional MPD in that it is capable of generating additional thrust from fusion energy released during the pinch phase of the arc rL;idown. The proposed 1-MJ facility would enable studies of thew concepts at a meaningful energy level. If the results are encoc;aging, as expected, a next step would be to construct a Po:+ type thruster for furthzr studies, inc!uding space qualificaticns In addition to thmster scdies, the MJ-class offers considerable flexibility for the study of a variety o tific applications rcquiring an intense, plsed, radiation sourc~. Examples of such uses range from studies of radiation hardering of electronics to trammutation of radioactive wastes. Conscquently, upon completion, it is planned to invite outside users to access the MJ-facility in the time that remains after mainline research. A key ohjective is to establish the DPF facility as a National User's Facility. To accomplish this, it is planned ;G establish an advisory committee for use of the facility next ycar and host a workshop for potential users.

No abstract