[en] The plasma described in this report is generated by a 15 to 34 kV ion beam, consisting primarily of protons, passing through an H₂ gas cell neutralizer. Plasma ions (or ion-electron pairs) are produced by electron capture from (or ionization of) gas molecules by beam ions and atoms. An explanation is provided for the observed anomalous behavior of the electron temperature (T/sub e/): a step-lite, nearly two-fold jump in T/sub e/ as the beam current approaches that which minimizes beam angular divergence; insensitivity of T/sub e/ to gas pressure; and the linear relation of T/sub e/ to beam energy

[en] We are testing operation and H^- yield of a sheet plasma source having a narrow primary electron channel (11 cm high, 30 cm long, and <1 cm wide). The design goal was J/sub H^-/ = 30 mA/cm² at V/sub arc/ = 100V, I/sub arc/ = 200A, B < 200g, and p/sub g/ = 5mT. Conditions outside the sheet are favorable for H^- production; at p/sub g/ = 10mT (cold fill - 8 sccm), V/sub arc/ = 75V, I/sub arc/ = 125A, and B = 200 G, 1 cm from the sheet edge, J⁺ = 380 mA/cm², T/sub e/ = 1.4 eV, and n/sub e/ = 5 . 10¹²/cm³, determined from Langmuir probe measurements. The movable negative ion extractor has a circular source aperture of area 1 cm². J/sub H^-/ is measured calorimetrically as well as electrically. Agreement of these two signals confirms the effectiveness of the carbon electron dump. Initial extraction at the above conditions produced J/sub H^-/ = 7 mA/cm² at 2 cm from the sheet edge. This current density is far below the design goals. We conclude that the sheet geometry is not primarily responsible for the high yield of J/sub H^-/. 2 refs., 5 figs., 1 tab

[en] A diagnostic was developed for the determination of temporal history of an X-ray spot. A pair of thin (0.5 mm) slits image the x-ray spot to a fast scintillator which is coupled to a fast detector, thus sampling a slice of the X-Ray spot. Two other scintillator/detectors are used to determine the position of the spot and total forward dose. The slit signal is normalized to the dose and the resulting signal is analyzed to get the spot size. The position information is used to compensate for small changes due to spot motion and misalignment. The time resolution of the diagnostic is about 1 ns and measures spots from 0.5 mm to over 3 mm. The theory and equations used to calculate spot size and position are presented, as well as data. The calculations assume a symmetric, Gaussian spot. The spot data is generated by the ETA II accelerator, a 2kA, 5.5 MeV, 60 ns electron beam focused on a Tantalum target. The spot generated is typically about 1 mm FWHM. Comparisons are made to an X-ray pinhole camera which images the X-Ray spot (in 2D) at four time slices

[en] As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact ion source is needed. Towards that end, we are testing a pulsed, surface flashover source, with deuterated titanium films deposited on alumina substrates as the electrodes. As the duration of the arc current is varied, it was observed that the integrated deuteron current per pulse initially increases rapidly, then reaches a maximum near a pulse length of 100 ns. Thin film patterning techniques and deuteration parameters will be discussed

[en] The understanding of laser beam propagation through underdense plasmas is of vital importance to laser-plasma interaction experiments, as well as being a fundamental physics issue. Formation of plasma channels has numerous applications including table-top x- ray lasers and laser-plasma-produced particle accelerators. The fast ignitor concept, for example, requires the formation of an evacuated channel through a large, underdense plasma. Scaled experiments have shown that the axial extent of a channel formed by a 100 ps pulse is limited by the onset of the filamentation instability. We have obtained quantitative comparison between filamentation theory and experiment. More recent experiments have shown that by increasing the duration of the channel-forming pulse, the filamentation instability is overcome and the channel extent is substantially increased. This result has important implications for the fast ignitor design and the understanding of time-dependent beam dynamics

[en] The characteristics of a small, water-cooled, 90⁰ magnetic deflection mass spectrometer suitable for analyzing positive and negative hydrogen ion species is described

[en] The authors are testing operation and H^- yield of a sheet plasma source having a narrow primary electron channel (11cm high, 30cm long, and <1cm wide). The design goal was J_Hsup -// - 30 mA/cm² at V_arc=100V, I_arc=200A, B<200g, and pg=5m1. This is similar in geometry and operational parameters to the plasma reported by Uramoto. Conditions outside the sheet are favorable for H^- production; at pg=10mT (cold fill - 8 sccm). V_arc=75V, I_arc=125A, and B=200 g, 1 cm from the sheet edge, J⁺=380 mA/cm², T_e-1.4 eV, and n_e=5 . 10¹²/cm³, determined from Langmuir probe measurements. The movable negative ion extractor has a circular source aperature of area 1cm². J_Hsup -// is measured calorimetrically as well as electrically. Agreement of these two signals confirms the effectiveness of the carbon electron dump. Initial extraction at the above conditions produced J_Hsup -// =7 mA/cm² at 2cm from the sheet edge. This current density is far below the design goals as well as below that reported by Uramoto. The authors conclude that the sheet geometry is not primarily responsible for the high yield of J_Hsup -// in Uramoto's source

[en] As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact ion source is needed. Towards that end, we are testing a pulsed, surface flashover source, with deuterated titanium films deposited on alumina substrates as the electrodes. An electrochemically-etched mask was used to define the electrode areas on the substrate during the sputtered deposition of the titanium films. Deuterium loading of the films was performed in an all metal-sealed vacuum chamber containing a heated stage. Deuterium ion current from the source was determined by measuring the neutrons produced when the ions impacted a deuterium-loaded target held at -90 kV. As the duration of the arc current is varied, it was observed that the integrated deuteron current per pulse initially increases rapidly, then reaches a maximum near a pulse length of 100 ns

[en] Ions extracted from a solid surface or plasma by impact of an high intensity and high current electron beam can partially neutralize the beam space charge and change the focusing system. We have investigated ion emission computationally and experimentally. By matching PIC simulation results with available experimental data, our finding suggests that if a mix of ion species is available at the emitting surface, protons dominate the backstreaming ion effects, and that, unless there is surface flashover, ion emission is source limited. We have also investigated mitigation, such as e-beam cleaning, laser cleaning and ion trapping with a foil barrier. The temporal behavior of beam spot size with a foil barrier and a focusing scheme to improve foil barrier performance are discussed

[en] A novel method for measuring the velocity of ion-acoustic waves is presented. The difference frequency between transmitted and received signals is observed as the transmitted frequency is swept linearly in time. This difference frequency is constant and proportional to the wave velocity. Temperatures inferred from the velocity agree with Langmuir probe measurement made on a hydrogen plasma