Cathode grid current dependence of D(d, n)~3He reaction rates in an inertial electrostatic confinement device driven by a ring-shaped magnetron ion source

摘要

We presentD(d, n)~3He reaction rates for a newinertial electrostatic confinement (IEC) device which aims to overcome neutralization (charge exchange) of accelerating ions by operating at D_2 gas pressures of just 5-10mPa with the aid of an internal ring-shaped magnetron ion source. Initial experiments with a voltage of -60 kV applied to a central spherical cathode grid yield neutron production rates (NPR) proportional to I ~(1.7) for cathode grid current in the range I = 0.1 - 1 mA. This approaches the ideal ∝ I ~2 dependence for a system dominated by energetically preferred, 'beam-beam' reactions between converging nuclei. However, later measurements show NPR ∝ I and also indicate changes in the pressure dependence. In fact the I ~(1.7) dependence was recovered by increasing the cathode grid voltage to -80 kV, though this too was only temporary. We suggest that time variation of NPR may be partially explained by a significant contribution of beam-grid reactions and temperaturedependent deuteron absorption by the grid cathode.