Neutron Yield Optimization From a Palm Top Plasma Focus Device Using Lee Code

Abstract

A palm top plasma focus (PF) device (100 J, 5 kV,

59 kA, ∼1.5 kg) with tapered anode was demonstrated in a study

earlier by (Rout et al., 2013). To simulate that device, we use

the Lee code (RADPFV5.16). The computed current trace is fit

to Rout’s measured current trace at 2.25 Torr deuterium (D2)

gas. The best- fit values of the model parameters are found as

fm = 0.11, fc = 0.73, fmr = 0.245, fcr = 0.78. Having fixed these

parameters, the computed neutron yields (Yn) 6.12 × 104, 1.72 ×

104, and 0.24 × 104 neutrons/shot are found to be comparable

with the measured values (5.2 ± 0.8) × 104, (2 ± 0.5) × 104,

and (0.2 ± 0.1) × 104 at (2.25 Torr, 5 kV), (1.875 Torr, 4 kV),

and (1.5 Torr, 3 kV), respectively. The remarkable agreement

shows the reliability of the code. Numerical studies are extended

with anode length and taper size optimization, corresponding to

the pressure range (2–3.5) Torr of D2. The optimum Yn (1.56 ×

105) is found at 2.55 Torr which is three times greater than the

highest measured value [(5.2 ± 0.8) × 104] at 2.25 Torr, 5 kV.

At this optimized configuration, using deuterium-tritium (1:1) as

the operating gas, the neutron yield is computed to increase to

107, about 100 times greater than the computed yield with D2.

In addition, we found that reducing the stray inductance L0 of the

device from its present value of 30 to 16 nH, the D-D neutron yield

is increased from computed value of 1.56 × 105 to 2.58 × 105.