Characterization of fusion plasmas in the cylindrical DTU inertial electrostatic confinement device

Abstract

Inertial electrostatic confinement offers a relatively simple and cost-effective means of generating fusion plasmas for research and industrial applications. Here, we present the experimental setup and discharge characteristics of the inertial electrostatic confinement device at the Dept. of Physics, Technical Univ. of Denmark. Special features of this setup include a cylindrical anode and the novel use of 3D printed soccerball-like cathode grids of different sizes. Measurements with these grids show 25% higher fusion neutron rates than with manually manufactured grids with larger wire spacings. Additionally, we observe significantly higher neutron rates with smaller grids, with spherical rather than cylindrical cathodes, and when using the vacuum chamber, rather than a second spherical grid, as the anode. Ion–orbit simulations predict a core density in the ion distribution in good agreement with optical measurements, confirming that asymmetries in the cathode grid potential prevent a fully convergent ion flow. The simulations also demonstrate that the asymmetry of the electric field induced by the voltage stalk lowers the characteristic ion recirculation by a factor of four, and we discuss measures to circumvent this. Comparing measurements and simulations conducted with a spherical and cylindrical grid reveals tentative evidence that fusion reactivity is highly core-localized, pointing to ion–neutral fusion as the dominant reaction. We also quantify the thermionic and impact-induced secondary electron emission in the device, showing that only the latter can potentially suppress the ion current during normal operation.

Evaluation of 3D printed buckyball-shaped cathodes of titanium and stainless-steel for IEC fusion system

“…18,19 Some studies reported that the electrode shape and dimension influence neutron yield. 6,20,21 Other studies focused on the anode material in the context of improving the NPR. 11,22 Elsewhere studies use different cathode materials, operated in a cylindrical anode at < 0.1 Pa gas pressure and < 40 kV applied voltage, in the context of cathode surface fusion and its significant contribution to the NPR.…”

From theory to hands-on: teaching experimental plasma physics using small plasma devices at DTU

“…At the Technical University of Denmark (DTU), we have recently acquired and developed two experimental plasma devices for research and education in fusion-relevant laboratory plasmas: a small tokamak, NORTH [10], for magnetic confinement of plasmas, and an inertial electrostatic confinement device, the DTU Fusor [11], for studies of fusion plasmas. A third experiment, a linear plasma device, is currently being commissioned.…”

Effect of Positive Polarity in an Inertial Electrostatic Confinement Fusion Device: Electron Confinement, X-ray Production, and Radiography

“…Finally, the beambeam or beam-background collision initiates the fusion process as a result of which neutrons are produced 7,9,10 . Since the development of the very first IECF device 11,12 , the researchers carried out geometrical and technical modification of the device in order to increase the neutron yield [13][14][15][16][17][18] , over the years. Recently, our team of researchers at CPP-IPR have a) Also at:Homi Bhabha National Institute, Anushaktinagar, Mumbai, Maharashtra, 400094, India; Email:smruti@cppipr.res.in carried out experiments in the cylindrical IECF device with some success in neutron production and its application in explosive detection [19][20][21][22][23] .…”

“…Pulsed x-ray has been produced in a table-top cylindrical IECF device by another group 26 . In some experiments, both neutron and x-ray has been produced during negative polarity of the grid in which the neutrons are produced from the central region and the x-ray from the wall region of the chamber 16,23 . However, due to the broad x-ray emitting zone the x-ray flux is less in such cases and hence, it has limitations as far as x-ray applications are concerned.…”