Compact sub-kilojoule range fast miniature plasma focus as portable neutron source

Abstract

As a first step toward the development of a compact and portable, quasi-continuous pulsed neutron source, we have demonstrated a 'fast miniature plasma focus (PF) device' as a compact nuclear fusion apparatus. The system operates with deuterium gas and produces an average neutron yield (Y 90 • ) of (1 ± 0.27) × 10 4 neutrons/shot at ∼70 kA peak discharge current. In the range of 1.5-4 mbar, a distinct and sharp dip in the current derivative signal indicates a strong pinching action with subsequent emission of hard x-rays followed by a neutron pulse. The yield and the time history of the neutrons were measured by both active and passive detection techniques (such as a 3 He proportional counter, NE102A plastic scintillator and CR-39 SSNTDs). The overall dimensions of the apparatus, which includes a capacitor bank, sparkgap switch and the focus chamber, are 0.2 m × 0.2 m × 0.5 m and the total mass of the system is ∼25 kg. The scope of this paper is to evaluate/demonstrate the potential of such a fast miniature PF device as a compact and portable fusion apparatus producing neutrons while operating at relatively low energy.

Palm top plasma focus device as a portable pulsed neutron source

“…For convenience, it is positioned close to the junction of the high voltage end of the spark gap and the capacitor bank. The neutron yield is measured simultaneously by three 3 He detectors 12,16,17 in proportional counter mode. In fact, each detector is a bank of six 3 He gas filled tubes.…”

Calibration methodology for proportional counters applied to yield measurements of a neutron burst

“…6 (ii) Cross calibration of the accumulated charge, generated in the counter by the burst of neutron, with a foil activation detector used as neutron reference. 7,8 Detectors based on activation by thermal neutrons have usually detection limits higher than 10 5 n per source burst. [9][10][11] Even though it is possible to extrapolate the calibration down to a yield of the order of 10 3 n per source burst, as the detection limits are transferred from the reference detector in a cross calibration, no improvements in the estimation of uncertainties in single shot measurements are obtained when the total neutron emission is less than 10 5 n per source burst.…”

Experimental evaluation of protons emission from a plasma focus device

“…During the past several years, the researchers have employed SSNTD (namely CR-39 and LR-115) to char-acterize ion emissions from plasma focus (PF) device of various bank energy ranges starting from few joules to megajoules (Szydlowski 2003;Takao et al 2003;Verma et al 2008). While investigating ion and neutron emissions from 1-MJ PF device, Szydlowski (2003) observed the fast deuteron fluxes of 10 5 ions/cm 2 emitted downstream along the electrode axis direction and these deuterons had energy of above several dozens of keV.…”