A plasma focus is being developed for breeding short-lived radionuclides. The different radiation protection issues and concerns posed by the machine once in operation are analysed and discussed. Activation is shown to be totally negligible and likewise neutron emission is found to pose no concern at all. The only source of radiation risk is found to rest in the radionuclides produced, 18F and 15 O, generating a peak exposure of 1.114 Sv y(-1) at the distance of closest approach of 2.5 m. Shielding to protect against this hazard is calculated to be 5 cm Pb or 54 cm concrete for the operation area and 5.5 cm Pb for the transportation flask.

Plasma focus (PF) technology development today is strictly related to the possibility of a high frequency repetitive working regime. One of the more relevant obstacles to this goal is the heating of structural components due to direct interaction with plasma. In this paper, temperature decay measurements of the inner electrode of a 7 kJ Mather type PF are presented. Data from several series of shots at different bank energies are analysed and compared with theoretical and numerical models. Two possible scale laws are derived from the experimental data to correlate thermal deposition with bank energy. It is found that a fraction of about 10% of total energy is released to the inner electrode. Finally, after some considerations about the cooling and heating mechanisms, an analysis on maximum temperature sustained by materials is presented.

This work presents the results of short circuit tests recently conducted on PFMA1 [1], a 150 kJ Mather-type Plasma Focus [2] designed to run at a repetition rate of 1 Hz for two hours at a time. PFMA1 is operated at 30 kV, with a 350 µF capacitor bank of 32 parallel capacitors. It is equipped with a custom designed fast high-voltage capacitive probe, a Rogowski coil [3] to monitor the total current flowing from the capacitor bank, and a breakdown time jitter analyzer. The short-circuit tests are conducted at 12 ÷ 13 kV. Snowplow-type 2D simulations [4] predict a peak of approximately 1.5 MA for the total current at a filling pressure of 10 Torr of deuterium. In this work a description of PFMA1 will be given, together with analytical computations of the inductance of the device; these computations will be compared with the results from a 2D finite element model in cylindrical symmetry. A full description of the electrical diagnostics used in the experiments will be provided. Experimental results will be presented and discussed, and will be compared with those obtained theoretically. Agreement is found to be very good.

PFMA-1 (Plasma Focus for Medical Applications -1) is the first prototype of a new application of the Plasma Focus technology conceived to produce Short Lived Radioisotopes (SLR) for medical PET-TAC imaging applications. The device is a 30 kV, 150 kJ, 40 nH Mather-type plasma focus designed for repetition frequencies up to 1 Hz and dedicated to the neutronfree endogenous production of 18 F by 3 He -16 O reactions. This paper describes some preliminary tests related to the pressure optimization of the gases used in PFMA-1, and presents some final considerations about performance improvements.

This paper presents some experimental results obtained with the plasma focus PFMA-1 operated at about 20.5 kV, corresponding to a total capacitor bank energy of about 70 kJ, with 4 He as working gas and pressure ranging between 50 and 3000 Pa. The aim of the study is the assessment of the differences in pinch performance with and without the adoption of a cathodic knife edge with the role of improving the electrical breakdown and the formation of the initial plasma layer. The pinch performance is estimated with the introduction of a voltage quality factor, which is related to the overvoltage intensity during the pinch, and of a current dip factor, correlated with the sudden total current reduction. More than 1500 shots have been analyzed with a semiautomated numerical special procedure. It is found that the improvement in the pinch efficiency with the use of a cathodic knife edge in these experiments can be even higher than a factor of 2.