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Diagnostics and scaling of fusion-produced neutrons in PF experiments

Schmidt H.

Nukleonika

2011

Vol. 56, No. 2

107-112

Neutrons from a plasma focus (PF) device operated in a deuterium gas, measured as a function of time, location and direction of emission, reveal quite a number of important parameters on fusion reactions occurring in the dense high-current phase of the experiment. In addition the determination of the energy spectra of the emitted neutrons is important for understanding the mechanisms taking place for the neutron production. Results of neutron measurements in large experiments such as the former POSEIDON experiment in Stuttgart and the PF-1000 experiment in Warsaw are presented. The neutron diagnostic methods that had been utilized include nuclear track detectors, plastic scintillators coupled to photomultipliers, activation measurements, time-of-flight methods as well as pinholes for spatial resolution of the neutron source. The well known scaling law according to which the neutron yield scales roughly as the square of the energy input or the fourth power of the current is discussed. Reasons for strong deviation from this law for high energies - known as the saturation effect - are still a subject of debate.

Recent progress in 1 MJ Plasma-Focus research

Scholz M., Karpiński L., Paduch M., Tomaszewski K., Miklaszewski R., Szydlowski A.

Nukleonika

2001

Vol. 46, nr 1

35-39

The paper reports on actual operational characteristics of the PF-1000 facility and it presents results of the first neutron experiments performed with a new set of large Mather-type electrodes, which were designed for shots up to 1000 kJ. Dynamics of a current-sheath was studied by means of two high-speed streak cameras and a two-frame camera. The last one was used for the side-on observation of the pinch column. The high-speed streak pictures were taken side-on behind slits oriented in the radial or axial direction. On the basis of the pictures taken behind the radial slit, average values of the radial compression and expansion velocities were estimated. Time-resolved X-ray signals were measured with PIN diodes covered by different filters, and they were compared with other traces (voltage waveforms, dI/dt signals, and neutron-induced pulses) in order to determine their correlation. The total neutron yield (Ytot), i.e. the number of neutrons produced during a single discharge and emitted in various directions, was measured by means of several silver-activation detectors placed at different angles around the PF-1000 experimental chamber.