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The use of a new extreme-ultraviolet radiation source based on spontaneous anti-Stokes scattering for high-resolution absorption spectroscopy of transition originating from the 3p6 shell of potassium is reported. The region from 546.6 to 536.8 A is scanned at a resolution of about 1.2 Kayser. Within this region, four previously unreported lines are observed.
Plasma-polymerized tetrafluoroethylene (PPTFE) coated potassium bromide IR window are shown to possess better resistance to moisture than either ethylene or chlorotrifluoroethylene. The PPTFE-coated windows tolerated an upper limit relative humidity of about 80% at 297 K, without visible damage to either window or coating, over a period of 24 hours. Elemental analysis of the bulk, and photoelectron spectroscopy of the coating surface, showed that PPTFE coatings deposited downstream of the internal plasma reactor electrodes contained less atmospheric oxygen than coatings deposited between the electrodes; perhaps accounting for the improved moisture resistance.
A single pass flow system was used to test the reactivity of calcium superoxide with respiratory gases and the performance was compared to that of potassium superoxide. The KO2 system is used by coal miners as a self-contained unit in rescue operations. Particular attention was given to the reactivity with carbon dioxide and water vapor at different temperatures and partial pressures of oxygen, carbon dioxide, and water vapor. The calcium superoxide beds were found to absorb CO2 and H2O vapor, releasing O2. The KO2 bed, however, released O2 at twice the rate of CO2 absorption at 37 C. It is concluded that the calcium superoxide material is not a suitable replacement for the KO2 bed, although Ca(O2)2 may be added to the KO2 bed to enhance the CO2 absorption.
Oscillator-strength measurements have been calibrated against the radiative lifetime for the 4s-4p transition of potassium. This yields a value of (8.1 + or - 0.5) times 10 to the -21 sq cm for the photoionization cross section at the series limit, and implies a value for the cross-section minimum in good quantitative agreement with that calculated by Seaton (1951).
The first comprehensive report on the petrology and geochemistry of Apollo 14 VHK (Very High Potassium) basalts and their implications for lunar evolution is presented. The reported data are most consistent with the hypothesis that VHK basalts formed through the partial assimilation of granite by a normal low-Ti, high-Al mare basalt magma. Assimilation was preceded by the diffusion-controlled exchange of alkalis and Ba between basalt magma and the low-temperature melt fraction of the granite. Hypotheses involving volatile/nonvolatile fractionations or long-term enrichment of the source regions in K are inconsistent with the suprachondritic Ba/La ratios and low initial Sr-87/Sr-86 ratios of VHK basalt. An important implication of this conclusion is that granite should be a significant component of the lunar crust at the Apollo 14 site.
Rb-Sr, K-Ar, and Sm-Nd isotopic studies were undertaken for two Apollo 14 very high potassium (VHK) highly radiogenic mare basaltic clasts from breccias 14305 and 14168. Rb-Sr data indicate ages of 3.83 + or - 0.08 b.y., and 3.82 + or - 0.12 b.y. for samples 14305 and 14168 respectively, for lambda(Rb-87) = 0.0 139/b.y. Their corresponding initial Sr-87/Sr-86 ratios are nearly identical, as well as their Ar-39 to Ar-40 age spectra, and it is proposed that they were derived from the same flow. The Sm-Nd isotopic data of whole rock and mineral separates for the two VHK basalts define an internal isochrone age of 3.94 + or - 0.16 b.y. for lambda (Sm-147) = 0.00654/b.y. and an initial Nd-143/Nd-144 of 0.50673 + or - 21. The similarity in isotopic ages suggests that VHK basalts crystallized from a melt about 3.85 b.y. ago. VHK basalts show very large Rb/Sr fractionation but no significant Sm/Nd fractionation at the time of crystallization. The source material had a Rb/Sr ratio similar to those of Apollo 14 high-Al mare basalts and a nearly chrondritic Sm/Nd ratio. Basalt/granite interaction was found to be responsible for the extreme enrichments of Rb/Sr and K/La during the formation of VHK basalts. It is concluded that K, Rb-rich components of granitic wall rocks in the highland crust were selectively introduced into ascending hot high-Al mare basaltic magma upon contact.
The quantum detection efficiency (QDE) of potassium bromide as a photocathode applied directly to the surface of a microchannel plate over the 250-1600 A wavelength range has been measured. The contributions of the photocathode material in the channels and on the interchannel web to the QDE have been determined. Two broad peaks in the QDE centered at about 450 and about 1050 A are apparent, the former with about 50 percent peak QDE and the latter with about 40 percent peak QDE. The photoelectric threshold is observed at about 1600 A, and there is a narrow QDE minimum at about 750 A which correlates with 2X the band gap energy for KBr. The angular variation of the QDE from 0 to 40 deg to the channnel axis has also been examined. The stability of Kbr with time is shown to be good with no significant degradation of QDE at wavelengths below 1216 A over a 15-day period in air.
Analysis of five very high potassium (VHK) basalts from Apollo 14 breccia 14303 shows the presence of a KREEP component. An assimilation and fractional crystallization model is presented to describe the basalt evolution. The influence of granite assimilation on the basalt evolution is discussed. The presence of VHK basalts containing only a granite signature and those with both granite and KREEP signatures suggests that there are at least two different VHK basalt flows at the Apollo 14 site.
The mineralogy and petrography of very high potassium (VHK) and high alumina (HA) basalts from the Apollo 14 site provide an insight into their magmatic evolution. Generally, their parageneses are similar, with olivine and chromite the early liquidus phases, followed by plagioclase and pyroxene, which crystallized together. Although late-stage ilmenite and FeNi metal occur in both VHK and HA samples, the VHKs also crystallize K-feldspar and Fa-rich olivine. Zoning of constituent minerals is similar for both basalt types, demonstrating that the parental magmas for both HA and VHK basalts became enriched in K, Na, Ca, Fe, and Ti and depleted in Mg and Al as crystallization proceeded. Enrichment of K in the VHK basalts is above that expected from normal fractional crystallization.
The understanding of basalt petrogenesis at the Apollo 14 site has increased markedly due to the study of 'new' samples from breccia 'pull-apart' efforts. Whole-rock compositions of 26 new high alumina (HA) and 7 very high potassium (VHK) basalts emphasize the importance of combined assimilation and fractional crystallization in a lunar regime. Previously formulated models for HA and VHK basalt petrogenesis are modified in order to accomodate these new data, although modeling parameters are essentially the same. The required range in HA basalt compositions is generated by the assimilation of KREEP by a 'primitive' parental magma. The VHK basalts can be generated by three parental HA basalts assimilating granite. Results indicate that VHK basalt compositions are dominated by the parental magma, and only up to 8 percent granite assimilation is required. This modeling indicates that at least three VHK basalt flows must be present at the Apollo 14 site.
Observations of neutral potassium (K) in the tenuous lunar atmosphere are described. An echelle spectrograph, CCD, and data acquisition system are used to obtain emission spectra of neutral K atoms in the lunar atmosphere as observed by the 1.54 telescope at the Catalina Observatory at first quarter the night of April 29, 1989. A table of relevant lunar atmosphere parameters summarizes the results of the investigation. It is found that the number density at the surface is 9.5 + or - 1 atoms per cu cm and that there is a large nonthermal component and a deficiency of atoms equilibrated to the surface temperature. The calculated thermalization rate of the nonthermal component through encounters with the lunar surface gives a source of strength for the thermal component factor of 7 greater than loss by photoionization. Possible explanations for the low thermalized population observed are considered.
A relatively simple calculation of the moments of momentum predicts the morphological order of crystal faces for potassium hydrogen phthalate. The effects on the habit caused by the addition of monomeric, dimeric, and larger aggregates during crystal growth are considered. The first six of the seven observed crystal faces are predicted with this method.
Multimegawatt nuclear electric propulsion (NEP) has been identified as a potentially attractive option for future space exploratory missions. A liquid-metal-cooled reactor, potassium Rankine power system that is being developed is suited to fulfill this application. The key features of the nuclear power system are described, and system characteristics are provided for various potential NEP power ranges and operational lifetimes. The results of recent mission studies are presented to illustrate some of the potential benefits to future space exploration to be gained from high-power NEP. Specifically, mission analyses have been performed to assess the mass and trip time performance of advanced NEP for both cargo and piloted missions to Mars.
A critical comment on the work of A.L. Sprague et al. (1990) is presented. It is argued that, in attributing an enhanced emission in the potassium D lines on Oct. 14, 1987 in the equatorial region of Mercury to a diffusion source centered on Caloris Basin, Sprague et al. misinterpreted the data. Sprague et al. present a reply, taking issue with the commenters.
Results are presented from Apollo satellite observations (from May 1988 to July 1991) of sodium and potassium in the lunar atmosphere. The observations of Na and K show a wide range of scale heights, single-component temperatures, and surface number densities, while the column abundances remain within a factor of 3. The observed trends can be explained using a model of competing release mechanisms with different dependences on solar zenith angle and resulting two-component atmospheres. The theory is applied to the budget of atomic oxygen.
Magnetographs, which measure polarized light, allow solar astronomers to infer the magnetic field intensity on the Sun. The Marshall Space Flight Center (MSFC) Vector Magnetograph is such an imaging instrument. The instrument requires rapid modulation between polarization states to minimize seeing effects. The accuracy of those polarization measurements is dependent on stable modulators with small field-of-view errors. Although these devices are very important in ground-based telescopes, extending the field of view of electro-optical crystals such as KD*Ps (potassium di-deuterium phosphate) could encourage the development of these devices for other imaging applications. The work that was done at MSFC as part of the Center Director's Discretionary Fund (CDDF) to reduce the field-of-view errors of instruments that use KD*P modulators in their polarimeters is described.
The start up of a liquid metal heat pipe from the frozen state was evaluated experimentally with a Nb-1%Zr heat pipe with potassium as the working fluid. The heat pipe was fabricated and tested at Los Alamos National Laboratory. RF induction heating was used to heat 13 cm of the 1-m-long heat pipe. The heat pipe and test conditions are well characterized so that the test data may be used for comparison with numerical analyses. An attempt was made during steady state tests to calibrate the heat input so that the heat input would be known during the transient cases. The heat pipe was heated to 675 C with a throughput of 600 W and an input heat flux of 6 W/cm(exp 2). Steady state tests, start up from the frozen state, and transient variations from steady state were performed.
A summary discussion of recent sodium and potassium observations for the atmospheres of the Moon and Mercury is presented with primary emphasis on new full-disk images that have become available for sodium. For the sodium atmosphere, image observations for both the Moon and Mercury are fitted with model calculations (1) that have the same source speed distribution, one recently measured for electron-stimulated desorption and thought to apply equally well to photon-stimulated desorption, (2) that have similar average surface sodium fluxes, about 2.8 x 10(exp 5) to 8.9 x 10(exp 5) atoms cm(exp -2)s(exp -1) for the Moon and approximately 3.5 x 10(exp 5) to 1.4 x 10(exp 6) atoms cm(exp -2)s(exp -1) for Mercury, but (3) that have very different distributions for the source surface area. For the Moon, a sunlit hemispherical surface source of between approximately 5.3 x 10(exp 22) to 1.2 x 10(exp 23) atoms/s is required with a spatial dependence at least as sharp as the square of the cosine of the solar zenith angle. For Mercury, a time dependent source that varies from 1.5 x 10(exp 22) to 5.8 x l0(exp 22) atoms/s is required which is confined to a small surface area located at, but asymmetrically distributed about, the subsolar point. The nature of the Mercury source suggest that the planetary magnetopause near the subsolar point acts as a time varying and partially protective shield through which charged particles may pass to interact with and liberate gas from the planetary surface. Suggested directions for future research activities are discussed.