Optimizing the Electrode Configuration of a Cylindrical Discharge-Type Fusion Device by Computational and Experimental Analysis

Abstract

A new design of a cylindrical discharge-type fusion device is proposed to achieve the precise alignment of components and prevent abnormal discharges. Cylindrical insulators that act as parts of the vacuum boundary and fix the relative position between cathode and anodes were used. The configuration of the electrodes was optimized to maintain stable discharge at low pressures and high discharge voltages, which enhances the neutron yield. The optimization was performed via analysis of the electric field and ion movements by developing a 2D code, and the results were experimentally verified. The results show that grounding the anodes is better for stable discharge at lower pressures. The optimized combination of the anode height and cathode overhang is 3 cm and 1 cm, or 2 cm, respectively. The discharge characteristics and neutron production rate were then experimentally measured for the optimized configuration. The attained highest discharge voltage (instantaneous) was ∼50 kV and the neutron production rate of 3 × 10 4 n/s was obtained by continuous discharge with an applied voltage of 30 kV and discharge current of 30 mA.

Anode shape dependency of discharge characteristics and neutron yield of a linear type inertial electrostatic confinement fusion neutron source

“…As can be seen from Figure 6, the relationship between the discharge voltage and the background gas pressure is highly dependent on the anode shape. Trends common to all shapes include being in a low gas pressure discharge state in which the discharge voltage rises as the gas pressure decreases, and being in an abnormal glow discharge state in which the discharge voltage rises due to increases in the current value (the same trends can be seen in the experiment by Noborio et al 19 …”

“…Additionally, since the electrodes can be efficiently cooled by contact heat transfer, it is easier to address the heat load that increases with the NPR. Prior studies on IEC fusion neutron sources with similar electrode arrangements include studies by Noborio 19 and Yamamoto 20 . In this paper, we focus on the anode shape of the linear IEC neutron source and report on the results of our detailed investigation into the effects of anode shape on discharge characteristics and the NPR.…”

2-D Evaluation of Bred Tritium Using Neutron Imaging Plate

“…DD fusion neutrons were generated by a discharge-type cylindrical fusion device, housing a negatively biased cylindrical cathode and a grounded anode [14]. By applying high voltages, a glow discharge plasma was induced.…”

Preparation for a neutronics experiment using a discharge fusion device and an imaging plate neutron detector

“…However, a neutron fluence ten times greater than the limit is required for a clear neutron radiograph and quantitative analysis as a low neutron fluence generates a high statistical error [8]. In the previous work, the maximum neutron yield of the device was less than 10 5 n/s because of the instability of glow plasma at >30 kV caused by overheating [5]. Further improvement in neutron yield by optimizing the discharge condition of the device is necessary for a quantitative 2D measurement.…”

“…This is because errors can be caused by uncertainties in the nuclear data, a discrepancy in the simulated and the actual geometries, and an unexpected neutron absorption by impurities in the blanket materials [1]- [4]. Therefore, it is planned to perform a neutronics experiment with a blanket mock-up initially with a cylindrical discharge-type deuterium-deuterium (DD) fusion device [5], [6], and later with a DT neutron source.…”