High Peak Flux Research Articles

Supersonic jet epitaxy of III-nitride semiconductors

In this review we report on the application of supersonic jets towards growth of the III-nitride semiconductors AlN, GaN, and InN. Certain properties of supersonic jets provide unique advantages for film growth. A seeded jet is able to accelerate precursors to kinetic energies which are one to two orders of magnitude higher than the average kinetic energies in a typical CVD environment, which has been shown to enhance precursor adsorption and thus growth rate. Indeed, dual seeded supersonic jets have been effectively employed to grow GaN and AlN from organometallic precursors and ammonia. Supersonic jets can also be coupled with excitation sources to provide highly reactive precursors for film growth. For example, a supersonic plasma jet has been developed to generate atomic nitrogen, and this source has been used together with an effusion cell for gallium delivery to produce epitaxial GaN films. The tightly focused jet exit stream generates a very high peak flux at the centerline which produced a film growth rate of 0.65 μm/h. However, deposition nonuniformity is quite dramatic due to this focusing and due to the point source nature of supersonic jets. Relatively few studies of III-nitride supersonic jet epitaxy have been reported, so further work is needed to evaluate the usefulness of this growth technique.

Continuous highly charged ion beams from the National Institute of Standards and Technology electron-beam ion trap

We describe our newly modified beam line and present its performance in conjunction with the National Institute of Standards and Technology electron-beam ion trap. We find that, contrary to previously reported results from similar ion sources, the highest intensity time-averaged ion fluxes are achieved by letting the ions boil out of the trap in a continuous stream rather than periodically dumping the trap to produce a pulsed beam. We produced continuous beams of 3.0(6)×106 Xe44+ ions per second and lower flux beams of charge states up to Xe49+. Also, in pulsed mode, we created beams with very high peak flux, over 1010 Xe44+ ions per second.

Perforated-plate magnetics. I. Mode-1 inductor/transformer

Two operating modes have been identified for a matrix inductor/transformer made by weaving conductors through the holes perforated in a flat magnetic plate. The Mode-1 perforated-plate matrix transformer (M1PPMT) is analyzed to assess its suitability for low-profile power converters. Analysis and finite-element simulation suggest that this type of transformer may be approximated as a collection of weakly coupled toroidal cores. Thus, it is possible to derive closed-form expressions relating typical performance parameters, such as magnetizing inductance and losses, to the hole radius, identified as a meaningful design parameter. High peak flux density around the holes appears to be a problem. Nevertheless, it is possible to design a 100 W M1PPMT with acceptable magnetizing inductance, efficiency, and power density. >

Nonlinear Thomson scattering of intense laser pulses from beams and plasmas.

A comprehensive theory is developed to describe the nonlinear Thomson scattering of intense laser fields from beams and plasmas. This theory is valid for linearly or circularly polarized incident laser fields of arbitrary intensities and for electrons of arbitrary energies. Explicit expressions for the intensity distributions of the scattered radiation are calculated and numerically evaluated. The space-charge electrostatic potential, which is important in high-density plasmas and prevents the axial drift of electrons, is included self-consistently. Various properties of the scattered radiation are examined, including the linewidth, angular distribution, and the behavior of the radiation spectra at ultrahigh intensities. Nonideal effects, such as electron-energy spread and beam emittance, are discussed. A laser synchrotron source (LSS), based on nonlinear Thomson scattering, may provide a practical method for generating tunable, near-monochromatic, well-collimated, short-pulse x rays in a compact, relatively inexpensive source. Two examples of possible LSS configurations are presented: an electron-beam LSS generating hard (30-keV, 0.4-\AA{}) x rays and a plasma LSS generating soft (0.3-keV, 40-\AA{}) x rays. These LSS configurations are capable of generating ultrashort (\ensuremath{\sim}1-ps) x-ray pulses with high peak flux (\ensuremath{\gtrsim}${10}^{21}$ photons/s) and brightness [\ensuremath{\gtrsim}${10}^{19}$ photons /(s ${\mathrm{mm}}^{2}$ ${\mathrm{mrad}}^{2}$), 0.1% bandwidth].

Development Of Robust Multilayer Optics For Use In High-Peak Power Radiation Environments

AbstractIn many applications, x-ray mulhilayer mirrors are exposed to high peak fluxes of x-rays with subsequent damage to the mirror. Mirror damage is a particularly severe problem with the use of multilayers as cavity optics for short wavelength x-ray lasers. Intense optical and x-ray radiation, from the x-ray laser plasma amplifier, often damages the multilayer mirror on time scales of hundreds of picoseconds. The phenomenon of multilayer mirror damage by pulsed xray emission has been studied using short duration (500 psec) bursts of soft x-rays from a laser produced gold plasma. The results of the experiments will be compared with some simple models and the possibility of increasing the damage thresholds of short wavelength multilayer mirrors will be discussed.

Characteristics of electron and high-energy proton flares

High-energy proton (Ep > 55 MeV) and electron (Ee > 50 keV) events were observed by University of Iowa experiments on the satellites Explorer 33 and 35. The solar X-ray (2–12 A) flares associated with the energetic proton events were found to have in general higher peak fluxes, considerably longer decay times (Δt) and smaller rise to decay time ratios (r) than the X-ray flares associated with the electron events. The most common decay times and rise to decay time ratios are: 80⩽ Δt ⩽ 100 min, 0.1 ⩽ r ⩽ 0.2 for the proton X-ray flares and Δt ⩽ 20 min, 0.3 ⩽ r ⩽ 0.7 for the electron ones.