Ion diode research and diagnostics
Ion diode research at Sandia National Laboratories is performed on the PBFA II accelerator. The goal of this research is to deliver a lithium ion beam of approximately 100 TW and greater than 1 MJ to an inertial confinement fusion target. These parameters should be adequate to test ICF ignition physics. During this past year, over 500 kJ of beam energy was generated with peak voltages of over 5 MV. Experiments at 1/4 energy produced a focal spot with a FWHM of 5.7 mm diameter for the proton portion of the beam. Typical diode impedance lifetimes (-Z/(dZ/dt)) of 30-40 ns, and diode current efficiencies (I/sub ion//I/sub total/) of at least 80% were obtained in these experiments. Diode efficiency and impedance were found to be critically dependent on the details of magnetic field profiles in the diode. A new analytic theory of diode operation was developed which explains the operating voltage and current of applied-B diodes. The theory is based on the self-consistent equilibrium position of the virtual cathode. The theory explains the operating impedance of the PBFA II diode and the applied-B diodes fielded on Proto I, Proto II, and PBFA I during the past several years. Particle-in-cell code simulations of diode operation are consistent with the predictions of this theory. To facilitate diode design, a capability was developed to predict ion trajectories in the diode as a function of time and ion species based on the experimentally measured voltage and current, the diode geometry, and the magnetic field profiles in the diode region. This capability provides guidance in modifying the anode geometry and the applied magnetic field profiles for optimum focusing of either protons or lithium ions. 21 refs., 19 figs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6788964
- Report Number(s):
- SAND-88-1896; CONF-880928-2; ON: DE88017118
- Resource Relation:
- Conference: Course and workshop on inertial confinement fusion, Varenna, Italy, 6 Sep 1988; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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