Publications

Permanent URI for this collection

https://hdl.handle.net/10217/100413

Browse

Now showing 1 - 20 of 565

Open Access
Potential use of radar differential reflectivity measurements at orthogonal polarizations for measuring precipitation
(Colorado State University. Libraries, 1976) Seliga, T. A., author; Bringi, V. N., author; American Metereological Society, publisher
The potential use of differential reflectivity measurements at orthogonal polarizations to determine rainfall rate is examined. The method involves measurements of ZH and ZV, the radar reflectivity factors due to horizontally and vertically polarized incident waves respectively. The differential reflectivity, ZDR= 10 log (ZH/ZV), which should be precisely determinate, occurs as a result of the distortion of raindrops as they fall at terminal velocity. The approximate theory of Gans for electromagnetic scattering by spheroids is applied to the distorted raindrops. Assuming a general exponential form for the raindrop size distribution, equation sare derived relating the distribution parameters to the measurements. The determination of rainfall rate follows directly. Finally, the sensitivity of the distribution parameters to radar inaccuracies is examined, and several methods of implementing the measurements are suggested. It is concluded that good estimates of rainfall rate using a single non-attenuating wavelength radar are possible under ideal conditions.
Open Access
Reliable passive mode locking with slow Q switching
(Colorado State University. Libraries, 1980) Marconi, Mario Carlos, author; Martinez, Oscar Eduardo, author; Diodati, Francisco Piero, author; American Institute of Physics, publisher
An electro-optic modulator (EOM) has been added to a passive mode-locked Nd:glass laser in order to slow Q-switch the cavity. This guarantees that the laser will work near threshold even if the gain of the laser medium or the losses change from shot to shot. The losses at the EOM are used as the output coupling. This new configuration allows more reliable operation of the system.
Open Access
The effect of an axial magnetic field on the spontaneous emission from an argon hollow cathode discharge
(Colorado State University. Libraries, 1981) Fetzer, G. J., author; Rocca, Jorge J., author; Collins, G. J., author; North-Holland, publisher
An applied longitudinal magnetic field is observed to decrease the equilibrium population of excited argon ion levels in a hollow cathode discharge, whereas the excited state populations of neutral argon atoms are not significantly altered. The longitudinal magnetic field is shown to decrease the effective density of beam electrons in the negative glow.
Open Access
Perfect mode locking of solid-state lasers by a double passive modulation
(Colorado State University. Libraries, 1982) Martinez, Oscar Eduardo, author; Marconi, Mario Carlos, author; Diodati, F. P., author; American Institute of Physics, publisher
A new configuration, which incorporates a second passive modulation, has permitted complete selectivity in passive mode locking of solid-state lasers. A theoretical study is presented showing the existence of qualitatively different types of emission depending on the parameters of the system. Computed simulations are made to show the dependence of the emission on such parameters, and are used to determine their optimum range. Experimental results are presented confirming computed predictions.
Open Access
Cw ion lasers pumped by electron beams
(Colorado State University. Libraries, 1982) Rocca, Jorge J., author; Yu, Zengqi, author; Meyer, D., author; Collins, G. J., author; Springer-Verlag, publisher
We have obtained cw laser radiation from singly ionized Hg, I, Cd, Se, and As by exciting He metal-vapor mixtures with a dc electron beam. The beam is generated by glow discharge electron guns located apart from the active medium. This is the first time that cw ion laser action has been obtained using electron beam excitation.
Open Access
Cw iodine ion laser excited by an electron beam
(Colorado State University. Libraries, 1982) Meyer, J. D., author; Yu, Z., author; Rocca, Jorge J., author; Collins, G. J., author; IEEE, publisher
CW laser oscillation has been obtained on the 5760.7 and6127.5 Å transitions of singly ionized iodine in an He-I2 plasma excited by a dc electron beam.
Open Access
Zn II and As II CW laser transitions excited by an electron beam
(Colorado State University. Libraries, 1982) Meyer, J. D., author; Rocca, Jorge J., author; Collins, G. J., author; IEEE, publisher
CW laser action was obtained on the 4911.6, 4924.0, 6102.5, and 7588.5 Å transitions of Zn II and on the 6511.7 Å transition of As II using electron beam excitation of He-Zn and He-As mixtures, respectively.
Open Access
Laser-induced chemical vapor deposition of SiO2
(Colorado State University. Libraries, 1982) Boyer, P. K., author; Ritchei, W. H., author; Roche, G. A., author; Collins, George J., author; American Institute of Physics, publisher
We have demonstrated rapid (3000 Å/min) photochemical deposition of silicon dioxide from gas phase donor molecules. An ArF (193 nm) laser was used to excite and dissociate gas phase SiH4 and N2O molecules in contrast to earlier work with incoherent mercury lamps. We have achieved 20 times the deposition rate, limited the dissociation volume to a localized region, and minimized the direct impingement of UV photons on the substrate. Although the SiO2 deposition rate was insensitive to substrate temperature from 20 to 600 °C, film quality noticeably improved above 200 °C, Metal-oxide-semiconductor capacitors were fabricated and characterized in order to measure SiO2 electrical properties. Film composition was investigated using Auger and infrared spectroscopy techniques and showed that the SiO2 is stoichiometric and contains less than 5% nitrogen.
Open Access
Electron beam pumped cw Se II laser
(Colorado State University. Libraries, 1982) Meyer, J. D., author; Rocca, Jorge J., author; Collins, G. J., author; North-Holland, publisher
We have observed cw laser action in 15 transitions of singly ionized selenium using an electron beam to excite a He-Se mixture. The variation of the laser output power as a function of the electron beam discharge parameters is reported.
Open Access
Multikilowatt electron beams for pumping cw ion lasers
(Colorado State University. Libraries, 1982) Collins, G. J., author; Farrell, M., author; Yu, Z., author; Meyer, J. D., author; Rocca, Jorge J., author; American Institute of Physics, publisher
A glow discharge electron gun capable of producing a well collimated de electron beam at energies between 1and 6 keV and currents up to 1A is described. The electron beam is produced in helium at pressures between 0.1 and 2 Torr without differential pumping. Beam generation efficiencies up to 80% have been measured. The electron guns are designed to pump cw ion lasers and are constructed to provide an optical path through the axis. Continuous-wave laser oscillation in Kr II has been obtained using electron-beam pumping of a He-Kr mixture.
Open Access
Hollow cathode electron gun for excitation of cw lasers
(Colorado State University. Libraries, 1982) Meyer, J., author; Rocca, Jorge J., author; Collins, G. J., author; North-Holland, publisher
Well collimated electron beam discharges with an energy of 1 kW, at currents up to 0.1 A, have been obtained at ambient pressures up to 0.4 Torr in Ar and 1.4 Torr in He using hollow cathode electron guns. The guns operate on a continuous or dc basis. These guns have the unique feature of providing a clear optical path through the axis. We suggest the use of such an electron beam discharge for excitation of cw ion lasers.
Open Access
Cw laser oscillations in Cd II in an electron beam created plasma
(Colorado State University. Libraries, 1982) Meyer, J. D., author; Rocca, Jorge J., author; Collins, G. J., author; North-Holland, publisher
A cw Cd II laser has been demonstrated using electron beam excitation. Cw laser oscillation has been obtained on six transitions of Cd 11 in a He-Cd plasma. Output power as a function of electron beam discharge parameters has been investigated.
Open Access
Transverse electron guns for plasma excitation
(Colorado State University. Libraries, 1982) Yu, Zengqi, author; Meyer, Jack, author; Rocca, Jorge J., author; Collins, George, author; American Institute of Physics, publisher
We report a plasma gun, which generates on a continuous basis, kilowatt electron beam discharges (e.g., 0.4 A at 4 kV) in an ambient pressure 0.1-1 Torr without differential pumping. Gun design characteristics, operating parameters, and measured beam profiles are given. Electron beam generation on a pulsed basis has also been studied. More than 100 A of beam current has been measured with a Faraday cup biased to - 100 V. A trapped electron beam scheme for achieving efficient deposition of the electron beam energy in a gas medium is described.
Open Access
Studies of a glow discharge electron beam
(Colorado State University. Libraries, 1983) Rocca, Jorge J., author; Yu, Zengqi, author; Collins, George J., author; American Institute of Physics, publisher
The energy spectrum of a kilovolt electron beam, generated by a helium glow discharge at pressures between 0.15 and 0.8 Torr, was measured with an electrostatic energy analyzer. An abrupt increase in the energy spread of the electron beam was observed to be coincident with an increase in the luminosity of the electron beam created plasma, and with the onset of intense microwave radiation. The relevance of these phenomena in cw electron beam pumped ion lasers is discussed.
Open Access
Electron beam assisted chemical vapor deposition of SiO2
(Colorado State University. Libraries, 1983) Collins, G. J., author; Boyer, P. K., author; Emery, K., author; Rocca, Jorge J., author; Thompson, L. R., author; American Institute of Physics, publisher
We have demonstrated electron beam assisted chemical vapor deposition of silicon dioxide films on silicon substrates via electron impact dissociation of SiH4, and N2O gas. Dissociation of reactant gases occurs primarily in the confined planar region of the electron beam created plasma. Electron beam deposited SiO2 films have been categorized in terms of their electrical, physical, and chemical properties.
Open Access
Compact Hg II laser excited by a transverse electron beam glow discharge
(Colorado State University. Libraries, 1983) McClure, David M., author; Rocca, Jorge J., author; Collins, George J., author; IEEE, publisher
CW laser action at an output power of 6 mW has been obtained on the 6149.5 Å transition of Hg II, using a 10 cm long transverse electron beam glow discharge. Beam energies are typically 1 keV. Laser tube design, discharge characteristics, and laser output power are reported.
Open Access
1-W cw Zn ion laser
(Colorado State University. Libraries, 1983) Meyer, J. D., author; Rocca, Jorge J., author; Collins, G. J., author; American Institute of Physics, publisher
We have obtained 1.2W of cw laser power on the 4911.6- and 4924.0-Å transitions of Zn II by exciting a He-Zn gas mixture with a dc glow discharge electron beam. In addition, 0.25-W output power has been obtained on the 6149.9-Å line of Hg+ using the same excitation scheme. The combination of electron beam ionization of rare gas atoms and subsequent charge transfer excitation to metal ion levels is shown to have the potential of significantly increasing the efficiency of ion lasers. cw multiwatt visible and ultraviolet ion lasers operating at efficiencies > 10-3 appear feasible using this excitation scheme.
Open Access
Large area electron beam annealing
(Colorado State University. Libraries, 1983) Russell, P. E., author; Collins, G. J., author; Johnson, T., author; Rocca, Jorge J., author; Moore, Cameron A., author; American Institute of Physics, publisher
We have achieved wide area (38 cm2) electron beam annealing of ion implanted silicon wafers using a glow discharge electron beam with electron energies between 3 and 7 keV. A continuous beam 7 cm in diameter with a power density up to 90 W/cm2 was used to anneal the 7-cm-diam central portion of boron-implanted (30 keV, 5 × 1015 atoms/cm2) n-type (100) silicon wafers 10 cm in diameter. Annealing was obtained without redistribution of the original dopant profile using a 15-s electron beam exposure. Due to the high electron beam power density achieved over a large area, one can uniformly anneal an entire wafer in a single exposure without sample or beam scanning.
Open Access
The energy of thermal electrons in electron beam created helium discharges
(Colorado State University. Libraries, 1983) Yu, Z., author; Collins, G. J., author; Rocca, Jorge J., author; She, C. Y., author; North-Holland, publisher
We have measured the electron energy of the thermal group of electrons in both longitudinal and transverse electron beam created helium glow discharges. The measurement technique employs the ratio of intensities of spectral lines in the 2s 3S-np 3P He I series. Values of kTe between 0.07 and 0.11 eV were obtained. These energies are typical of the beam generated electric field free plasmas. The competitive loss of helium ions by recombination and by charge transfer in a He-Hg electron beam created plasma is calculated. The results are applied to the Hg+ laser pumping scheme using a electron beam created He-Hg plasma.
Open Access
An error analysis for 2-D block implemented digital filters
(Colorado State University. Libraries, 1983) Azimi-Sadjadi, Mahmood R., author; King, Robert A., author; IEEE, publisher
This correspondence considers error analysis of block implemented 2-D digital filters. Expressions for error bound and mean-square error for roundoff error accumulation are derived using fixed point arithmetic, and compared with the results obtained using ordinary 2-D difference equations.