Behavior of low energy fast Plasma Focus devices as D-D fusion neutron sources
A. E. Tarifeño-Saldivia 1*, L. Soto 1,2
1 Comisión Chilena de Energia Nuclear
2 Center for Research and Applications in Plasma Physics and Pulsed Power, P4, Chile
The deuterium Plasma Focus (PF) is a transient electrical discharge produced by an arrange of coaxial electrodes and driven typically by a capacitive pulsed power generator . The interest on PF discharges started in the late sixties motivated by research programs in Z- pinch physics as candidates for thermonuclear fusion. After several years of research, the interest on thermonuclear fusion was moved to more stable configurations such as Toroidal devices. Notwithstanding, in the last decade several groups around the world, have started research programs with small devices operated at low energies . This renewed interest is motivated among others by the technological perspective of using the PF as a compact, transportable and intense source of pulsed fast neutrons. The strategy has been to construct low energy generators to produce high currents by using a low inductance designing concept. As result of the inductance reduction, characteristic times for the evolution of the discharge have been decreased from microseconds up to hundreds or tens of nanosecond. In addition, to make low energy fast devices competitive for neutron production with other continuous and pulsed sources, the generators should be operated in repetitive mode. Although it has been demonstrated that a similar phenomenology is observed in devices operated in a wide range of energy (0.1J – 1MJ) [3, 4], our knowledge of the behavior of fast plasma focus as neutron sources is still limited. In this work, the experimental characterization as a neutron source of the extreme fast PF-50J plasma focus device is presented . The device was operated in repetitive mode at repetition rates of 0.1 − 0.5Hz. Results of optimal configurations, emission regimes, pulsed emission rate, neutron yield and observed anisotropy are presented; pulsed fast neutron diagnostic techniques are discussed as well. Additionally, engineering aspects affecting neutron emission, such as contaminants and discharge chamber design, were also studied. The shot-to-shot statistical behavior of the neutron yield is presented and compared with theoretical models. Finally, the efficiency for neutron production of fast PF devices including PF-50J is discussed comparatively with devices operating at longer characteristic times. Work supported by FONDECYT grant 1110940.
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