This presentation is to discuss the impact of a reduced nuclear weapons stockpile on the strategic stability. Methodologies used to study strategic stability issues include what are basically strategic-force exchange models. These models are used to simulate a massive nuclear exchange in which one side attacks and the other side retaliates. These models have been of interest to the Strategic Defense Initiative (SDI) program. Researchers have been looking at issues concerning the stability of the transition period, during which some defenses have been deployed and during which deterrence and war-fighting capability reply partly on defense and partly on offense. Also, more recently, with interest in the Strategic Arms Reduction Treaty (START) and force reductions beyond START, the same calculation engines have been used to examine the impact of reduced forces on strategic stability. For both the SDI and the START reduction cases, exchange models are able to address only a rather narrow class of strategic stability issues. Other broader stability questions that are unrelated to nuclear weapons or that relate to nuclear weapons but are not addressed by the calculational tools which are not included in this discussion. 6 refs., 1 fig., 1 tab. (BN)
The efficiency of soft x-ray production from laser-irradiated plasmas is simulated for two different spectral regions. These two regions, 14{Angstrom} {plus minus} 15% and 130{Angstrom} {plus minus} 1%, were chosen for proximity mask or point-projection technological applications. Relatively large conversion efficiencies were obtained from irradiation of a stainless steel target using the conditions suggested by recent Hampshire Instruments' experiments for proximity masking. Pulse-width and laser frequency parameter studies were performed for point-projection applications which suggest that the conversion applications which suggest that the conversion efficiency is sensitive to pulse-width but not to laser frequency. One of the critical components of any x-ray lithographic scheme is of course the x-ray laser source. There are two primary contenders for a reliable, efficient source currently: synchrotron radiation and spectral emission from laser produced plasma. The dominant issue for laser-plasma emission is the conversion efficiency -- output in the intended operating spectral region relative the required incident laser energy. Simulations are described in the following for both high and low energy spectral regions which have been suggested by either the proximity masking or point-projection technology.
Mossbauer spectroscopy (MS) is a viable non-contact'' technique applicable to high-pressure, diamond anvil cells (DAC) with samples containing a wide variety of the elements suitable for MS. The convenience and simplicity of diamond anvil cells as a means to obtain static high pressures even into the megabar regime has resulted in a renewed interest in pressure as a complement to the usual physical measurements. However, the required small sample size and the difficulty of communicating with the sample leave only x-ray and optical spectroscopy as the readily available tools. Mossbauer spectroscopy which involves recoil-free, low-energy {gamma} rays, provides a powerful additional technique to study a myriad of physical properties in a DAC. MS concerns a particular isotope and can provide local information on phase changes and hysteresis, isomer shifts, valence, bonding, magnetic and quadrupolar interactions, lattice dynamics, and multiple sites. The Mossbauer effect has been seen in about a hundred isotopic transitions in about forty different elements; many are suitable for DAC-MS, most notably {sup 57}Fe, {sup 119}Sn, {sup 121}Sb, {sup 125}Te, {sup 129}I, {sup 149}Sn, {sup 151}Eu, {sup 161}Dy, {sup 1976}Au, and {sup 237}Np. Since the information available from MS is obtained from analyzing the precise energy profile of the Mossbauer {gamma} ray from a source/absorber combination, no contacts or difficult coupling to the DAC are required. We review a number of salient features of the DAC-MS method and present some examples, including new work on FeI{sub 2}.
Mossbauer spectroscopy (MS) is a viable ``non-contact`` technique applicable to high-pressure, diamond anvil cells (DAC) with samples containing a wide variety of the elements suitable for MS. The convenience and simplicity of diamond anvil cells as a means to obtain static high pressures even into the megabar regime has resulted in a renewed interest in pressure as a complement to the usual physical measurements. However, the required small sample size and the difficulty of communicating with the sample leave only x-ray and optical spectroscopy as the readily available tools. Mossbauer spectroscopy which involves recoil-free, low-energy {gamma} rays, provides a powerful additional technique to study a myriad of physical properties in a DAC. MS concerns a particular isotope and can provide local information on phase changes and hysteresis, isomer shifts, valence, bonding, magnetic and quadrupolar interactions, lattice dynamics, and multiple sites. The Mossbauer effect has been seen in about a hundred isotopic transitions in about forty different elements; many are suitable for DAC-MS, most notably {sup 57}Fe, {sup 119}Sn, {sup 121}Sb, {sup 125}Te, {sup 129}I, {sup 149}Sn, {sup 151}Eu, {sup 161}Dy, {sup 1976}Au, and {sup 237}Np. Since the information available from MS is obtained from analyzing the precise energy profile of the Mossbauer {gamma} ray from a source/absorber combination, no contacts or difficult coupling to the DAC are required. We review a number of salient features of the DAC-MS method and present some examples, including new work on FeI{sub 2}.
This paper provides a brief and mostly non-technical description of the militarily important features of nuclear weapons, of the physical phenomena associated with individual explosions, and of the expected or possible results of the use of many weapons in a nuclear war. Most emphasis is on the effects of so-called ``strategic exchanges.``
Photocathodes of quantum efficiency above 1% at the doubled YAG frequency of 532 nM are very sensitive to the local vacuum environment. These cathodes must have a band gap of less than 2.3 eV, and a work function that is also on the order of {approximately}2 volts or less. As such, these surfaces are very reactive as they provide many surface states for the residual gases that have positive electron affinities such as oxygen and omnipotent water. Attendant to this problem is that the optimal operating point for some of these cesium based cathodes is unstable. Three of the cesium series were tried, the Cs-Ag-Bi-O, the Cs{sub 3}Sb and the K{sub 2}CsSb. The most stable material found is the K{sub 2}CsSb. The vacuum conditions can be met by a variety of pumping schemes. The vacuum is achieved by using sputter ion diode pumps, and baking at 250{degrees}C or less for whatever time is required to reduce the pump currents to below 1 uA at room temperature. To obtain the required partial pressure of cesium, a simple very sensitive diagnostic gauge has been developed that can discriminate between free alkali and other gases present. This Pressure Alkali Monitor (PAM) can be used cesium sources to provide a low partial pressure using standard feedback techniques. Photocathodes of arbitrary composition have been transferred to a separate vacuum system and preserved for over 10 days with less than a 25% loss to the QE at 543.5 nM.
Photocathodes of quantum efficiency above 1% at the doubled YAG frequency of 532 nM are very sensitive to the local vacuum environment. These cathodes must have a band gap of less than 2.3 eV, and a work function that is also on the order of {approximately}2 volts or less. As such, these surfaces are very reactive as they provide many surface states for the residual gases that have positive electron affinities such as oxygen and omnipotent water. Attendant to this problem is that the optimal operating point for some of these cesium based cathodes is unstable. Three of the cesium series were tried, the Cs-Ag-Bi-O, the Cs{sub 3}Sb and the K{sub 2}CsSb. The most stable material found is the K{sub 2}CsSb. The vacuum conditions can be met by a variety of pumping schemes. The vacuum is achieved by using sputter ion diode pumps, and baking at 250{degrees}C or less for whatever time is required to reduce the pump currents to below 1 uA at room temperature. To obtain the required partial pressure of cesium, a simple very sensitive diagnostic gauge has been developed that can discriminate between free alkali and other gases present. This Pressure Alkali Monitor (PAM) can be used cesium sources to provide a low partial pressure using standard feedback techniques. Photocathodes of arbitrary composition have been transferred to a separate vacuum system and preserved for over 10 days with less than a 25% loss to the QE at 543.5 nM.
This brief status report provides an introduction to what fuel cells are, why they are important, what uses have been made of them to date, the goals and timetables of current programs, and who the players are in this vital technology. Copies of most of the slides presented and additional diagrams are appended to this paper. Further details can be obtained from the comprehensive texts cited in the bibliography. 11 refs., 44 figs.
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