Organization:
Physics (PH)

Description

The mission of the Physics Department is to provide defense-relevant, advanced education and research programs to meet Naval unique needs, and increase the warfighting effectiveness of the U.S. Naval Forces, DoD and allied armed forces.

Website of the organization

https://nps.edu/web/physics

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Publication Search Results

Now showing 1 - 10 of 11

Cerenkov and sub-Cerenkov radiation from a charged particle beam
(Monterey, CA; Naval Postgraduate School, 1987) Neighbours, John R.; Buskirk, Fred R.; Maruyama, Xavier K.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Naval Postgraduate School (U.S.); Physics
As a consequence of the relaxation of the phasing conditions between the moving charge and radiated wave for finite beam path lengths, the Cerenkov peak is broadened and the threshold energy is developed which is applicable to charged beams consisting of single point charge or charge bunch of finite size, as well as beams consisting of periodically repeated bunches
Laser altimeter for use over the ocean
(Monterey, California. Naval Postgraduate School, 1989-04) Bourne, Carlton M.; Crittenden, Eugene Casson; Rodeback, George Wayne; Cooper, Alfred William; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Physics
Charging characteristics of Dynamic Explorer I Retarding Ion Mass Spectrometer and the consequence for core plasma measurements
(Monterey, California. Naval Postgraduate School, 1989-09) Olsen, Richard Christopher; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Physics
The Retarding Ion Mass Spectrometer (RIMS) on the Dynamics Explorer I (DE I) satellite has provided a new range of data, and challenges for studies of the core plasma of the magnetosphere. Analysis of the RIMS data provides a measure of the satellite potential in the inner magnetosphere. As the satellite leaves the inner plasmasphere, it begins to charge positively, crossing the 0 V mark at about 1000/cc. The potential rises slowly initially, reaching about 1 V near the plasmapause, at the 100/cc point. At lower densities, the potential rises relatively rapidly, reaching +5 V or greater at the 10/cc point. For satellite potentials of +1 to +5 V, portions of the ion distribution function are lost to measurement because the ions are repelled by the satellite. In particular, in a multi-temperature plasma, the cold component is easily lost in this potential (density) regime. It is in this regime where aperture bias techniques have been successfully used, particularly in measurements of field- aligned ion flows such as the polar wind, which have sufficient kinetic energy to overcome electrostatic barriers in front of the aperture plane. At lower densities (<10/cc), the satellite potential can exceed +5 V. At such potentials the core plasma is lost to the RIMS, and even the aperture bias techniques are no lower successful. Keywords: Spacecraft charging; Thermal plasmas; Mass spectrometry. (EDC)
Observation of microwave Cerenkov radiation as a diffraction pattern
(Monterey, CA; Naval Postgraduate School, 1985-08-01) Maruyama, Xavier K.; Neighbours, John R.; Buskirk, Fred R.; Snyder, D. D.; Bruce, Robert G.; Vujaklija, Milorad; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Naval Postgraduate School (U.S.); Physics
Measurement of microwave Cerenkov radiation in air exhibits the diffraction pattern predicted in earlier work. The radiation appears only at harmonics of the frequency of periodic electron bunches, angular distribution power measurements are presented for frequencies of 2.86, 5.71, 8.57 and 11 & 12 GHz corresponding to the fundamental and the first three harmonics of an S band RF linac
Frequency content of coherent Cherenkov radiation
(Monterey, California. Naval Postgraduate School, 1989-11) Neighbours, John R.; Buskirk, Fred R.; Maruyama, Xavier K.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Physics
At constant beam energy and propagation angle, the coherent radiation from a charged particle beam is a function of frequency only. The intensity of the radiation oscillates with a frequency dependent on length of the path of the beam and is modulated by the form factor corresponding to the shape of an individual charge bunch. Calculations are presented for line charge distributions which have rectangular, triangular, and trapezodial axial variation. A point charge distribution is also considered for comparison. Keywords: Radiation from electron beam; Cherenkov radiation. (jhd)
Short pulse laser and plasma surface interactions
(Monterey, CA; Naval Postgraduate School, 1984-04-02) Schwirzke, F.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Naval Postgraduate School (U.S.); Physics
Professor John Dyer Memorial Lecture : the origin of the universe from quantum chaos, an introduction to current ideas
(Monterey, California. Naval Postgraduate School, 1989-05) Woehler, Karlheinz E.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Physics
In his recently published book 'A Brief History of Time', S. Hawking describes his remarkable insights into the problem of the origin of our universe. In this talk a more quantitative description of some of the important principles from this book is presented as a mathematical appendix to it. A brief review of the ideas of the Standard Big Bang Model of the Universe is given in terms of the evolution equation that follows from Einstein's theory. The meaning of the Cosmological Constant, its relation to Vacuum Energy, the model of the empty DeSitter Space and Gravity is derived. By analogy to Schrodinger mechanics one can give the general features of Quantum Cosmology', in which the origin of the universe can be viewed as a Quantum tunneling process in imaginary time from a Quantum Chaos state of no space, no time, no matter to an inflationary expanding DeSitter space which eventually transits into the Hot Big Bang Expansion that we see
Emission threshold for Cerenkov radiation
(Monterey, CA; Naval Postgraduate School, 1985) Neighbours, John R.; Buskirk, Fred R.; Maruyama, Xavier K.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Naval Postgraduate School (U.S.); Physics
Modification, testing, and calibration of infrared search and target designator hardware received from NSWC
(Monterey, California. Naval Postgraduate School, 1989-05) Crittenden, Eugene Casson; Cooper, Alfred William Madison; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Physics
Unipolar arcing, a basic laser damage mechanism
(Monterey, CA; Naval Postgraduate School, 1985-05-05) Schwirzke, F.; Physics (PH); Graduate School of Operational and Information Sciences (GSOIS); Naval Postgraduate School (U.S.); Physics
Unipolar arcing has been shown to be the primary plasma-surface interaction process when a laser produced plasma is in contact with a surface. Evidence of unipolar arcing was found on all targets irradiated at atmospheric pressure that also arced in vacuum, stainless steel, titanium, molybdenum, copper, and aluminum. Cratering was observed even for a defocused and low-power laser pulse. The minimum laser power density required for the onset of breakdown on the surface is also sufficient to cause arc damage. Never was there a plasma evident without attendant unipolar arc craters. About 500,000 arc craters per cm have been observed on laser illuminated metal surfaces although no external voltage is applied. Smaller size craters with a density of about 10^/cm^ have been found on higher resistivity materials. The higher resistivity requires the radially inward surface return current to converge to a smaller cathode spot size to achieve sufficient power density to vaporize and ionize the material required for running the unipolar arc. The local increase of the plasma pressure above the cathode spot leads to an electric field configuration which drives the arc current and also facilitates the return current flow to the surface and cathode spot. Unipolar arcing concentrates the available laser-plasma energy towards the cathode spot. Large scale unipolar arcing on metal surfaces increases the coupling of energy from the laser heated plasma into the target. The ejection of a plasma jet from the cathode crater also causes highly localized shock waves to propagate into the target, softening it in the process. Thus, material erosion is much more severe than it would be case for uniform energy deposition over a larger area. This research has wide spread applications. Any situation in which a sufficiently hot surface plasma exists there will be unipolar micro-arcing. The physics relates to other forms of electrical breakdown on surfaces and electrodes.