| Plasma and X-UV Source Characteristics for Al Targets Heated by 40 Nsec Nd-laser Pulses |
16 MAR 1999 |
39 pages |
| Authors:
Robert R. Whitlock; David J. Nagel; Stephen J. Topscher; J. R. Greig; NAVAL RESEARCH LAB WASHINGTON DC
|
 | The total laser energy (3-32 J), temporal history (40 nsec FWHM) and focal energy distribution (3-10(exp 13) W/sq cm peak, 1.5 x 10(exp 13) W/sq cm average) for lambda = 1.06 microns Nd:glass laser interactions with planar Al targets were measured. Laser-produced plasma emissions within the 10 eV - 3 keV ultraviolet and x-ray range were recorded. Primary emphasis was given to obtaining the dependence ... |
|
| Interaction of an Intense Relativistic Electron Beam with Preformed Channels |
12 JUN 86 |
|
| Authors:
D. P. Murphy; M. Raleigh; R. E. Pechacek; J. R. Greig; NAVAL RESEARCH LAB WASHINGTON DC
|
 | The interaction of an intense relativistic electron beam (REB) with preformed channels in gaseous atmospheres demonstrates the effects of reduced density, avalanche ionization, preexisting conductivity, and channel currents. The intense REB for these experiments was produced from a field emission diode driven by the approx. 1.4 MV pulse from a pulse forming line. Peak REB currents up to approx. 16 kA, and current densities up to approx. 2 kA/cm2 were ... |
|
| A Gated Microchannel Plate Image Intensifier Packaged in a Reflex Camera Back |
19 DEC 85 |
22 pages |
| Authors:
S. Hauver; R. E. Pechacek; J. R. Greig; D. P. Murphy; M. Raleigh; NAVAL RESEARCH LAB WASHINGTON DC
|
| We describe a fast (exposure down to approx. 10 ns) electrically triggered camera back/shutter designed for use with the Haselblad 500C still camera. This camera back contains a microchannel plate image intensifier which can be gated and provides a gain of approximately X1000. It reads out on to Polaroid film through a fiber optic face plate. The gated camera back is interchangeable with the regular Polaroid back (or any other) ... |
|
| Electrostatic Charging of the CH-53E Helicopter |
29 NOV 1985 |
47 pages |
| Authors:
R. E. Pechacek; J. R. Greig; D. P. Murphy; J. Spelz; NAVAL RESEARCH LAB WASHINGTON DC
|
| We have measured the effects of electrostatic charging on the CH-53E helicopter. Measurements were made over a clean runway and over sandy terrain in basically desert conditions where electrostatic charging is known to be a problem. While the measured charging current (up to approx. 75 microAmp) and open circuit voltages (up to approx. 140 kV) cannot be claimed as maximum values attainable by the CH-53E, they show that the CH-53E ... |
|
| Beam Propagation Studies at NRL (Naval Research Laboratory) July 1983 to June 1984. Volume 2 |
30 NOV 1984 |
|
| Authors:
R. Hubbard; M. Raleigh; D. Murphy; R. Pechacek; J. R. Greig; NAVAL RESEARCH LAB WASHINGTON DC
|
| This report is comprised of summaries of unclassified papers presented at the DARPA/Services Annual Propagation Review, June 1984, at the Naval Postgraduate School, Monterey, California. A variety of theoretical and experimental studies are covered, including a review of propagation community codes and topics in channel chemistry, holeboring, hose instability, diagnostics, and beam channel tracking. The papers and authors are listed in the order in which they appeared at the meeting. ... |
|
| A Study of Long Aerosol Initiated Laser Induced Air Breakdown Plasmas |
29 JUN 1984 |
|
| Authors:
R. E. Pechacek; M. Raleigh; J. R. Greig; D. P. Murphy; F. Camelio; NAVAL RESEARCH LAB WASHINGTON DC
|
| Results from three separate experiments on aerosol initiated, laser induced, air breakdown are described. The purpose of these experiments was to determine the maximum length of air breakdown plasma that can be created with a given laser pulse. Two separate neodymium glass lasers were used; the first produced an output pulse of 30 J in 60 ns and the second produced 200 J in 4 ns. Both pulses were at ... |
|
| REB (Relativistic Electron Beam)/Channel Tracking Experiments in Low Pressure Ammonia |
26 MAR 1984 |
|
| Authors:
D. P. Murphy; M. Raleigh; E. Laikin; R. E. Pechacek; J. R. Greig; NAVAL RESEARCH LAB WASHINGTON DC
|
| This document presents the results of an investigation of the interaction between an intense relativistic electron beam (REB) and reduced density channels in ammonia (NH3) at 40 Torr. The channels were produced by absorption in the ammonia of energy from a pulsed CO2 laser. Two channel geometries were studied. The first employed an 2.5 cm radius channel with the nominally 1.2 cm radius REB injected coaxially. The second geometry employed ... |
|
| Channel Cooling by Turbulent Convective Mixing |
12 MAR 1984 |
|
| Authors:
J. R. Greig; R. E. Pechacek; M. Raleigh; NAVAL RESEARCH LAB WASHINGTON DC
|
| Results from a series of experiments are described which show that hot, reduced-density channels in the atmosphere usually cool by a process of turbulent convective mixing. Five different types of channels were created (a) by the interaction of a pulsed CO2 laser with aerosols in the atmosphere, (b) by electric discharges in the atmosphere, (c) by laser-guided, electric discharges in the atmosphere, and (d) and (e) by the absorption of ... |
|
| A Transmission Line Bridge for the Diagnostics of Plasma Channels |
07 MAR 1984 |
|
| Authors:
R. E. Pechacek; M. Raleigh; J. R. Greig; T. Dwyer; J. Ehrlich; NAVAL RESEARCH LAB WASHINGTON DC
|
| This paper describes a device for measuring the average electrical conductivity of a long, narrow, cylindrical plasma. Interest in plasmas of this shape originates from two areas of study: the study of electron beam propagation through neutral gas, and the study of long straight electrical discharges for use as a communication antenna. Propagation of an electron beam through a neutral gas produces an ionized channel whose properties and evolution are ... |
|
| Theory of Beam Channel Hydrodynamics |
07 MAR 1984 |
|
| Authors:
J. M. Picone; J. P. Boris; J. H. Gardner; J. R. Greig; M. Raleigh; NAVAL RESEARCH LAB WASHINGTON DC
|
| This document reports on recent theoretical studies and numerical simulations of hot channels produced in a gaseous medium by a beam. Experiments by Greig et al. have demonstrated that similar channels produced by electric discharges and/or laser pulses in air or nitrogen undergo rapid, turbulent cooling. It explains this phenomenon on the basis of vorticity generation by zero-order misalignment of pressure and density gradients as the hot channel expands to ... |
|
| An Experimental Study of the Hydrodynamics of Reduced Density Channels |
10 JUN 1982 |
|
| Authors:
J. R. Greig; R. E. Pechacek; M. Raleigh; K. A. Gerber; NAVAL RESEARCH LAB WASHINGTON DC
|
| Experiments on both the formation and decay of reduced density channels in gaseous atmospheres have been performed using a novel method to produce channels in nitrogen by the absorption of pulsed carbon dioxide laser radiation. These experiments were performed in a chamber consisting of three regions: a nonabsorbing convergence section filled with pure nitrogen in which the CO2 laser beam was focused to small diameter and high intensity; a windowless ... |
|
| Characteristics of an Atmospheric Discharge Plasma as an RF Antenna |
27 MAY 1982 |
22 pages |
| Authors:
J. R. Greig; R. E. Pechacek; M. Raleigh; T. Dwyer; D. P. Murphy; NAVAL RESEARCH LAB WASHINGTON DC
|
| The plasma produced by a laser-guided, electric discharge in the atmosphere has been formed in the shape of a folded monopole antenna with a characteristic frequency of 112 MHz. This plasma antenna has been used to transmit and receive signals at 112 MHz. While the plasma conductivity remained above a certain value, the signal transmitted from, and received on, the plasma antenna was within -l + or - 1 dB ... |
|
| Energy Losses from a Heated Air Column |
17 MAY 1982 |
18 pages |
| Authors:
M. Raleigh; J. R. Greig; R. F. Fernsler; NAVAL RESEARCH LAB WASHINGTON DC
|
| Estimates are made of the energy losses from the hot channel produced by (laser-guided) electric discharges in the atmosphere. The loss processes considered are heat conduction, continuum radiation, and line radiation. For the conditions calculated to exist in such channels (Te approx. 20,000 K, sigma (i) N (i) equal 2x10 to the 18th power c per cu.cm), the total energy loss is found to be small compared to the measured ... |
|
| Dynamics of an Intense Relativistic Electron Beam Injected into Full Density Air |
21 SEP 1981 |
|
| Authors:
R. B. Fiorito; E. W. Fordham; J. R. Greig; R. E. Pechacek; J. D. Sethian; NAVAL RESEARCH LAB WASHINGTON DC
|
| We have injected an intense relativistic electron beam (about 1 Mev, 16 kA, 25 ns) into the atmosphere and observed the beam in visible light caused by direct beam excitation of air molecules. The emitted visible light was primarily emission in the 2nd positive system of N2 which was delayed with respect to the beam current by about 6 ns but had the same duration (FWHM) as the beam current. ... |
|
| Convective Cooling of Lightning Channels. |
14 APR 1981 |
|
| Authors:
J. M. Picone; J. P. Boris; R. F. Fernsler; J. R. Greig; M. Raleigh; NAVAL RESEARCH LAB WASHINGTON DC
|
| We report experimental data which trace the time development of electric discharge channels in air and which demonstrate the turbulent cooling of such channels. These data provide qualitative confirmation of the model proposed and used by Hill, Ranker, and Wilson to calculate the production of nitrogen oxides by lightning. We outline an analytical treatment which identifies asymmetries in the pressure and density gradients of the discharge channel as a significant ... |
|
| An Initial Study of the Injection of an Intense Relativistic Electron Beam into the Atmosphere. |
04 MAR 1981 |
|
| Authors:
R. B. Fiorito; R. F. Fernsler; J. R. Greig; M. Herndon; I. M. Vitkovitsky; NAVAL RESEARCH LAB WASHINGTON DC
|
| Using the VEBA pulse generator (approx. or less than 2 MV, approx 60 kAmp, approx. 60 ns) and a field emission diode with a titanium foil anode (approx. 43 micrometers), relativistic electron beams with v/y approx. 0.5 have been produced and injected into the atmosphere. Typical injected net currents were approx. 35 kAmps and there was little plasma return current (approx. or less than 20%). These beams were observed to ... |
|
| Laser-Initiated, Reduced Density Channels for Transporting Charged Particle Beams. |
13 FEB 1981 |
34 pages |
| Authors:
M. Raleigh; J. R. Greig; R. E. Pechacek; E. Laikin; NAVAL RESEARCH LAB WASHINGTON DC
|
| A charge particle beam driven inertial confinement fusion reactor will require reduced density, current carrying channels through the gas blanket to transport the beams from the diodes to the target. We have created suitable reduced density channels in air at atmospheric pressure by guiding an electric discharge with laser-induced, aerosol-initiated air-breakdown. The resulting channel which is no longer current carrying stabilizes, about 30 microsec after the electric dischage, at a ... |
|
| A Quantitative Schlieren System for Measuring Radial Density Profiles of Reduced Density Channels in Gases. |
12 FEB 1981 |
26 pages |
| Authors:
M. Raleigh; J. R. Greig; NAVAL RESEARCH LAB WASHINGTON DC
|
| A quantitative Schlieren system used to measure the radial density profiles of reduced density channels in gases is described. The system uses a simple, single path optical train and does not require a coherent light source. The cylindrical symmetry of the channels permits an Abel-like inversion of the path integrated bending of the light to yield the radial density profile. The inversion algorithm and a program using it are given ... |
|
| The 24 Inch CUSP Experiment. |
15 FEB 1980 |
|
| Authors:
R. E. Pechacek; J. R. Greig; M. Raleigh; D. W. Koopman; A. W. DeSilva; NAVAL RESEARCH LAB WASHINGTON DC
|
| A spectroscopically pure, fully ionized D2 plasma containing 2 X 10 to the 19th power ions is generated from solid D2 pellets using a sequence of a 100 J Nd-Glass laser pulse and a 1000 J CO2 laser pulse. The plasma is used to fill a cusp configured magnetic field with a beta = 1 plasma. The width of the ring cusp is determined using laser scattering techniques. The laser ... |
|
| submicrosecond x-ray lithography |
NOV 78 |
|
| Authors:
D. J. Nagel; m. c. peckerar; R. R. Whitlock; J. R. Greig; R. E. Pechacek
|
| x-rays from laser-heated plasmas were used to replicate features as fine as 750 nm in the positive resist polybutene-1-sulfone (p.b.s.). the measured sensitivities of p.b.s. to pulsed and d.c. x-rays (approximately 10 to the 9th power ratio in exposure rate) are similar (no reciprocity loss). laser- plasma x-rays produced only small (0-25v) flat-band shifts in m.o.s. capacitors at irradiation levels sufficient to expose p.b.s. (author) |
|
| A Preliminary Study of Aerosol Initiated CO2 Laser Produced Air Sparks and Their Ability to Guide Electrical Discharges. |
NOV 1977 |
|
| Authors:
J. R. Greig; R. E. Pechacek; R. F. Fernsler; I. M. Vitkovitsky; A. W. DeSilva; NAVAL RESEARCH LAB WASHINGTON D C
|
| The time development of air sparks initiated on aerosols near the focal region (f = 3m) of a 1 kJ CO2 laser beam has been studied. The spark at each aerosol produced a shock wave that expanded spherically at approximately 200000 cm/sec during the 1.5 microsec. tail of the laser pulse. In time these spherical waves coalesced forming a turbulent cylindrical column from which a cylindrical blast wave separated. The ... |
|
| The NRL One Kilojoule CO sub 2 Laser. |
SEP 1977 |
|
| Authors:
R. E. Pechacek; J. R. Greig; M. Raleigh; S. R. Rod; NAVAL RESEARCH LAB WASHINGTON D C
|
| This report describes an Ultra-Violet preionized, CO2 laser head developed at NRL for use in plasma production experiments. A 1000 Joule CO2 laser, consisting of four of these heads is to be used with a 100 J ND-glass laser to produce a large, moderately warm plasma (N = 3 x 10 to the 19th power ions, T approx 50 eV), which is to be studied in a variety of magnetic ... |
|
| A 100 J, 40 nsec Q-Switched Nd/Glass Laser. |
FEB 1977 |
|
| Authors:
J. R. Greig; R. E. Pechacek; NAVAL RESEARCH LAB WASHINGTON D C
|
| This report describes the characteristics of a high power Nd/glass laser presently in operation at the Naval Research Laboratory. The laser will produce 100 J of 1.06 micrometer radiation in a 40 nsec pulse, or in two pulses each of which is 40 nsec wide and separated by 300 nsec to 5 microsec. The divergence of the laser beam is approximately 0.0003 radian so that power densities in excess of ... |
|
| Break-Up Dynamics of Polymer Beads under Laser Bombardment. |
FEB 1977 |
|
| Authors:
J. R. Greig; R. E. Pechacek; NAVAL RESEARCH LAB WASHINGTON D C
|
| Spherical polymer beads approximately 1 mm diameter, have been irradiated with a 100 J, 40 nsec Q-switched Nd/glass laser. This is not enough energy to dissociate and ionize all the atoms contained in the polymer bead. Instead a small fraction (about 1%) of the material is ablated from the irradiated side of the bead accounting for about 60% of the laser pulse energy. The remainder of the polymer bead subsequently ... |
|
| Production of Large Warm Plasmas by Staged Laser Heating of Solid Targets. |
FEB 1977 |
|
| Authors:
R. E. Pechacek; J. R. Greig; NAVAL RESEARCH LAB WASHINGTON D C
|
| A 1000 Joule CO2 laser pulse, focussed on a slowly expanding (dr/dt = 200,000 cm/sec) gas cloud in a vacuum chamber, ionizes the gas by laser spark breakdown, and then heats it by inverse bremstrahlung absorption. The resulting plasma contains about 10 to the 19th power ions at a temperature of approximately 50 eV. The gas cloud is created by irradiating a solid plastic target with a 10 J prepulse ... |
|
Reports by Author
