Gregory R. Piefer

Overview of University of Wisconsin Inertial-Electrostatic Confinement Fusion Research

Abstract In Inertial Electrostatic Confinement (IEC) devices, a voltage difference between concentric, nearly transparent spherical grids accelerates ions to fusion-relevant velocities. The University of Wisconsin (UW) operates two IEC devices: a cylindrical aluminum chamber and a spherical, water-cooled, stainless-steel chamber, with a power supply capable of 75 mA and 200 kV. The research program aims to generate fusion reaction products for various applications, including protons for creating radioisotopes for nuclear medicine and neutrons for detecting clandestine materials. Most IEC devices worldwide, including the UW devices, presently operate primarily in a pressure range (1-10 mtorr) that allows ions to make only a few passes through the core before they charge exchange and lose substantial energy or they collide with cathode grid wires. It is believed that fusion rates can be raised by operating at a pressure where neutral gas does not impede ion flow, and a helicon ion source has been developed to explore operation at pressures of ~0.05 mtorr. The UW IEC research group uses proton detectors, neutron detectors, residual gas analyzers, and spectroscopic diagnostics. New diagnostic techniques have also been developed, including eclipse disks to localize proton production and chordwires to estimate ion fluxes using power balance.

Detection of highly enriched uranium using a pulsed D-D fusion source

Abstract This paper overviews the work that has been done to date towards the development of a compact, reliable means to detect Highly Enriched Uranium (HEU) and other fissile materials utilizing a pulsed Inertial Electrostatic Confinement (IEC) D-D fusion device. To date, the UW IEC device has achieved 115 kV pulses in excess of 2 ampere, with pulsed neutron rates of 1.8x109 n/s during a 0.5 ms pulse at 10 Hz. MCNP modeling indicates that detection of samples of U-235 as small as 10 grams is achievable at current neutron production rates, and initial pulsed and steady-state HEU detection experiments have verified these results.

Recent Progress in Steady State Fusion Using D-3He

Abstract The University of Wisconsin (UW) inertial electrostatic confinement (IEC) facility has made significant progress since 2000. The operating voltage has doubled to 160 kV. The neutron production rate has increased by a factor of 2, from 4.9 x 107/s to 1.1 x 108s-1. The D-3He proton production rate has increased by, a factor of over 40. In addition new diagnostics have been developed, including a method to determine the spatial distribution of fusion reactions A new water cooled stainless steel chamber for higher power and lower pressure has been put into operation. Medical isotopes have been produced in an IEC device for the first time.

Design of an ion source for 3He fusion in a low pressure iec device

Abstract Recent developments in helicon ion sources and Inertial Electrostatic Confinement (IEC) device performance at UW-Madison have enabled low pressure (< 50 μtorr, 6.7 mPa) operating conditions that should allow the 3He-3He fusion reaction to be observed in an IEC device. An ion source capable of delivering a ~ 10 mA 3He ion beam into an IEC device with minimal neutral gas flow has been designed and tested. Furthermore, a new IEC device that has never been operated with deuterium has been constructed to avoid D-3He protons from obstructing the 3He-3He reaction product spectrum, and to minimize Penning ionization of deuterium by excited helium, which in the past is suspected to have limited the ionized density of He. These developments make it possible to study beam-background 3He-3He fusion reactions with > 300 mA recirculating ion currents.

Production of 13N Via Inertial Electrostatic Confinement Fusion

Abstract This paper describes a proof of principle experiment to produce 13N using an inertial electrostatic confinement (IEC) fusion device. This radioisotope is often used in positron emission tomography scans to image the heart. The 10-minute half-life of 13N limits its use to those areas and clinics that possess an accelerator. A portable IEC device could be brought to remote locations, however, and produce short-lived PET isotopes on-site. Using the 14.7 MeV protons produced from the D-3He fuel cycle, the University of Wisconsin IEC device was used to produce approximately 4 - 8 Bq of 13N during two separate experiments.

Alternate Applications of Fusion - Production of Radioisotopes

Abstract A major effort to find near-term, non-electric applications of fusion energy has shown that the production of radioisotopes is attractive. The use of the D3He fusion reaction to produce Positron Emission Tomography (PET) isotopes is described. An Inertial Electrostatic Confinement (IEC) device is particularly well suited to produce low levels of high-energy (14.7 MeV) protons, which in turn, can produce short-lived PET isotopes. The IEC device at the University of Wisconsin has been modified to investigate the potential of this process to be commercially attractive.

D-/sup 3/He fusion in an inertial electrostatic confinement device

Advanced fusion fuels, D and /sup 3/He, have been successfully fused in an inertial electrostatic confinement device at the University of Wisconsin. It is thought that this is the first known fusion of helium-3 with deuterium on a steady state basis. The detection of 14.7 MeV protons has confirmed the reaction of D-/sup 3/He fusion, and has produced a continuous, charged particle flux in excess of 1.4/spl times/10/sup 5/ protons/s. Using the same device with D-D fuel a neutron rate of 2.2/spl times/10/sup 7/ was achieved. Operating parameters that affect the reaction rate are discussed.