Search

This document summarizes the Bumpy Torus Experiment as a viable fusion reactor concept. Conclusions reached include the following: In 30 years, order-of-magnitude technological advances have occurred in multiple areas of plasma heating and confinement. The ORNL bumpy torus of the 1970s was technology limited. Now that ITER is technology limited, an alternate concept is needed. A device built on such a concept should be current free, CW, modular, have a gentle shutdown, and demonstrable stability. The bumpy torus meets or has the potential to meet all of these criteria. Earlier, stability was not possible due to power limits; it has not been fully tested. It is time to revisit the bumpy-torus concept with a modest new machine.

The ICF program today is investigating three approaches to achieving multi-MJ fusion yields and ignition: (1) laser indirect (x-ray) drive on the National Ignition Facility (NIF), (2) laser direct drive (primarily on the Omega laser facility at the University of Rochester), and (3) magnetic direct drive on the Z pulsed power facility. In this white paper we briefly consider a fourth approach, magnetic indirect drive, in which pulsedpower- driven x-ray sources are used in place of laser driven sources. We first look at some of the x-ray sources studied on Z prior to 2007 before the pulsed power ICF program shifted to magnetic direct drive. We then show results from a series of 1D Helios calculations of double-shell capsules that suggest that these sources, scaled to higher temperatures, could be a promising path to achieving multi-MJ fusion yields and ignition. We advocate here that more detailed design calculations with widely accepted 2D/3D ICF codes should be conducted for a better assessment of the prospects.

Standard state thermodynamic properties for fully ionized aqueous perrhenic acid at temperature in the range of (298.15 to 598.15) K and at psat were determined by high dilution solution calorimetry (10−4 m). A comparison of the standard state thermodynamic properties for fully ionized aqueous perrhenic acid, HReO 4 ( aq ) , and sodium perrhenate, NaReO 4 ( aq ) , establishes for the first time the quantitative values for the differences between H + ( aq ) and Na + ( aq ) from temperature of (298.15 to 598.15) K. Perrhenic acid is believed to be the first strong acid to be thermodynamically well characterized under standard state conditions to date from measurements down to 10−4 m. The value of the Debye–Huckel limiting slope for enthalpies of dilution at temperature of 596.30 K of 122 ± 6 kJ · mol−3/2 · kg1/2, obtained from the integral heats of solution measurement at various concentrations, is in good agreement with theoretical value in literature, 121 kJ · mol−3/2 · kg1/2. This agreement verifies that HReO 4 ( aq ) obeys the simple limiting law for strong electrolytes. Many thermodynamic properties of soluble sodium electrolytes can now be converted to the corresponding acid form.

Standard state thermodynamic properties for aqueous sodium perrhenate at temperature in the range of (298.15 to 598.15) K and at psat were determined by high dilution solution calorimetry down to 10−4 m. Standard state partial molar heat capacities, C p , 2 ∘ , of aqueous sodium perrhenate calculated from present study are compared to literature values up to T = 398.15 K. The differences between C p , 2 ∘ of ReO 4 - ( aq ) and Cl−(aq) at lower temperature is much greater than that due to their internal molecular motions. Consequently, the perrhenate ion appears to have an ionic incomplete primary hydration shell as compared to the chloride ion. The ReO 4 - / Cl - difference in thermodynamic functions has now been well defined up to T = 598.15 K for other important high temperature calculations.

In this communication we report the calorimetric data for the standard state enthalpies of solution of cesium chloride obtained from low concentrations, down to (10−3 m), integral heats of solution measurement up to temperature of 573.30 K and extrapolated to 598.15 K. From these data and the unified theory of electrolytes, the complete standard state thermodynamic properties ( H 2 ∘ , G 2 ∘ , C p , 2 ∘ , V 2 ∘ , ( ∂ V 2 ∘ / ∂ T ) p , ( ∂ V 2 ∘ / ∂ p ) T ) of aqueous cesium chloride were determined up to temperature of 598.15 K.

Pabalan and Pitzer (Geochim. Cosmochim. Acta 1988, 52, 2393-2404) reported a comprehensive set of thermodynamic properties of aqueous solutions of sodium sulfate without using ion association or hydrolysis. However, there is now ample evidence available indicating that the ion association cannot be ignored at temperatures Tor=373 K. For example, even at the lowest concentration of their studies (mor=0.05) and at 573.15 K, less than 20% of SO4(2-)(aq) is available as free ions. In the present study, the integral heats of solution of sodium sulfate were measured to very low concentrations (10(-4) m) up to 573.16 K. The data were analyzed correcting for the hydrolysis of SO4(2-)(aq) and the association of Na+(aq) with SO4(2-)(aq) and NaSO4-(aq) in order to obtain the final standard state thermodynamic properties of completely ionized aqueous sodium sulfate, Na2SO4(aq). From these and the available solubility data, the stoichiometric activity coefficients of saturated aqueous solutions of sodium sulfate were calculated up to 573.15 K and compared with literature data. The stoichiometric activity coefficients of aqueous solutions of sodium sulfate, as a function of temperature at all concentrations (0or=mor=msat), were also calculated up to 573.15 K.

In this communication, we report the first calorimetric data for the standard state enthalpies of a solution of sodium chloride obtained from high dilution, down to (10(-3) m), integral heats of solution measurements to 596.30 K. Although there are no comparable thermodynamic data available at such high dilutions in the literature, the present results for NaCl(aq) can be used for many thermodynamic studies by others to achieve a complete thermodynamic description of this key electrolyte over very wide ranges of concentration. From the recently developed unified theory of electrolytes, the experimental data from this study were used to predict Gibbs free energies of hydration of sodium chloride up to 1100 K. These Gibbs free energies of hydration at different pressures and densities compare well with reported values obtained from ab initio calculations by others.

A new theoretical treatment has been developed for predicting the thermodynamic properties of electrolytes up to and beyond the critical temperature of water (973 K and at pressures up to 1000 MPa). The model is based upon the classical Born equation corrected for non-Born hydration effects. The temperature and pressure behavior of electrolytes can now be accurately predicted from existing low temperature data. Only two constants are needed for each electrolyte at all temperatures and pressures, where data exist to test the theory.

Targets are used for a variety of purposes, but ultimately we use them to validate codes that help us predict and understand new phenomena or effects. The sophistication and complexity of High Energy Density Physics (HEDP) and Inertial Confinement Fusion (ICF) targets has increased in time to match the advances made in modeling complex phenomena. The targets have changed from simple hohlraums, spherical geometries, and planar foils, to 3-dimensional geometries that require precision in construction, alignment, and metrology. Furthermore, material properties, such as surface morphologies and volume texture, have significant impact on the behavior of the targets and must be measured and controlled. In the following we will discuss how experimental physicists view targets and the influence that target construction has on interpreting the experimental results. We review a representative sampling of targets fabricated at the Los Alamos National Laboratory that are used in different experiments in support of ICF and HEDP.

We present spatially, temporally, and spectrally resolved narrow- and broad-band x-ray images of polar-direct-drive (PDD) implosions on OMEGA. These self-emission images were obtained during the deceleration phase and bang time using several multiple monochromatic x-ray imaging instruments fielded along two or three quasi-orthogonal lines-of-sight including equatorial and polar views. The instruments recorded images based on K-shell lines from a titanium tracer located in the shell as well as continuum emission. These observations constitute the first such data obtained for PDD implosions. The image data show features attributed to zero-order hydrodynamics. Equatorial view synthetic images obtained from post-processing a 2D hydrodynamic simulation are consistent with the experimental observation. Polar view images show a pentagonal pattern that correlates with the PDD laser illumination used on OMEGA, thus revealing a 3D aspect of these experiments not previously observed., Comment: 22 pages, 10 figures, submitted for publication

The potential for laser-plasma instability is a serious concern for indirect-drive inertial confinement fusion (ICF), where laser beams illuminate the interior of a cavity (called a hohlraum) to produce x-rays for imploding a fusion capsule symmetrically. The speckled nature of laser beams used in ICF is an important factor in laser-plasma instability processes. For example, models which calculate the spatial growth of convective instability by properly accounting for the laser speckles successfully predict the observed onsets of backscattering due to stimulated Brillouin and Raman scattering instabilities (SBS and SRS). Assuming pump depletion as the only saturation mechanism in these models results in very large predicted levels of SBS and SRS backscattering from the long-scale plasmas expected in ignition hohlraums. However, in the long-scale plasmas studied in the Nova and Trident lasers [E. M. Campbell, Rev. Sci. Instrum. 57, 2101 (1986) and N. K. Moncur et al., Appl. Opt. 34, 4274 (1995)], SRS and S...

A double-slit diffraction experiment is described for measuring pulse coherence time, pulse widths, and maximum power of laser radiation pulses. (AIP)

Standard state thermodynamic properties for completely dissociated hydrochloric acid were fixed by ionic additivity, using the data from other strong electrolytes perrhenic acid, sodium perrhenate, and sodium chloride from 298.15 to 598.15 K and at p(sat). The standard electrode potential for the important silver-silver chloride electrode system and the equilibrium constants for the volatility of HCl from aqueous solutions were then calculated and compared with literature data. Using the experimental data from this study and auxiliary data from literature, the logarithm of the molal association constant of HCl at the critical temperature of water and at 673.15 K up to 1000 MPa was predicted from the unified theory of electrolytes (UTE). The standard state thermodynamic properties for completely dissociated aqueous sodium hydroxide were also calculated by ionic additivity over the same temperature range from aqueous sodium chloride, hydrochloric acid, and the dissociation constant of water. The results were compared with literature data.

The heat of solution of solid cubic gadolinium oxide has been measured in noncomplexing perrhenic acid solutions at very high dilutions (10(-4) m) up to 596.30 K, from which the standard state thermodynamic properties of aqueous gadolinium perrhenate were determined up to 623.15 K. From the measured differences between similar properties of aqueous sodium chloride and perrhenate, thermodynamic properties for aqueous gadolinium chloride were obtained by ionic additivity. Data for the hydrolysis of Gd3+(aq) were obtained by separate determinations. The enthalpy of solution of gadolinium chloride at 623.15 K obtained from this research (-2.7 MJ mol(-1)) is apparently larger than any other recorded for a chemical reaction involving aqueous systems. Standard state partial molal heat capacities for ThCl4(aq) were predicted up to 623.15 K.

It has become apparent in the last few years that the light ion surface contamination on short-pulse laser targets is a major impediment to the acceleration of heavier target ions. Mitigation strategies have been tested in experiments at the Los Alamos Trident Laser facility using one arm of the Trident laser at 150 ps to ablatively clean a large area of heated targets in a single short that are subsequently irradiated by the Trident 30 TW short-pulse arm to accelerate the bulk target ions to high energies. This process was used on targets consisting of 15 microns of vanadium. The 150 ps pulse rids the rear of the target of its omnipresent surface contamination layer, consisting mainly of water vapor and hydrocarbons, and allows the Trident 30 TW short-pulse arm to illuminate the target and accelerate ions via the Target Normal Sheath Acceleration (TNSA) mechanism. Because this mechanism relies on a laser generated electrostatic sheath, the ions with the lightest charge to mass ratio (i.e. protons) would be accelerated preferentially at the expense of heavier ions. However with the contamination layer removed, and hence the bulk of the available protons, the TNSA mechanism is able to accelerate the bulk material ions to high energies. Our experimental results are discussed and compared to the LASNEX rad-hydro code to validate and improve our predictive capabilities for future acceleration experiments.

An understanding of the timing and dynamics of hohlraum filling by laser-induced gold wall ablation is critical to the performance of indirectly-driven fusion ignition designs for the National Ignition Facility [E. Moses and C. Wuest, Fusion Science and Technology, 43 , 420 (2003)]. Hohlraum wall ablation negatively affects ignition hohlraum performance by (1) reducing laser coupling by increasing backscatter by laser plasma instabilities, e.g., stimulated Brillouin scattering, (2) altering where lasers couple by moving the critical surface away from the walls and changing the refractive index, and (3), in the case of vacuum hohlraums, ablating directly into contact with the ablation layer of the fuel capsule. We report on measurements of gold-filling of hohlraums from a series of OMEGA laser [T.R. Boehly, R.L. McCrory, C.P. Verdon et al., Fusion Engineering and Design, 44, 35 (1999)] experiments involving vacuum and gas-filled hohlraums. On-axis x-ray imaging of gold self-emission shows delayed filling for gas-filled hohlraums, as expected. In addition, we present data on the hohlraum temperature penalty incurred with the use of a 1-atmosphere methane-fill. We discuss data and simulation predictions for 1-atmosphere neopentane filled hohlraums driven with a modified laser pulse.

This new project relies on the capabilities collocated at LosAlamos in theTrident laser facility of long-pulse laser drive, for laser-plasma formation, and high-intensity short-pulse laser drive, for relativistic laser-matter interaction experiments. Specifically, we are working to understand quantitatively the physics that underlie the generation of laserdriven MeV0nucleon ion beams, in order to extend these capabilities over a range of ion species, to optimize beam generation, and to control those beams. Furthermore, we intend to study the interaction of these novel laser-driven ion beams with dense plasmas, which are relevant to important topics such as the fast-ignition method of inertial confinement fusion ~ICF!, weapons physics, and planetary physics. We are interested in irradiating metallic foils with the Trident short-pulse laser to generate medium to heavy ion beams ~Z 20–45! with high efficiency. At present, target-surface impurities seem to be the main obstacle to reliable and efficient acceleration of metallic ions in the foil substrate.Inordertoquantifytheproblem,measurementsofsurfaceimpuritiesontypicalmetallic-foillasertargetswere made. To eliminate these impurities, we resorted to novel target-treatment techniques such as Joule-heating and laser-ablation, using a long-pulse laser intensity of ;10 10 W0cm 2 . Our progress on this promising effort is presented in this paper, along with a summary of the overall project.

X-ray imaging is one essential tool for capturing phenomena that occur when high-irradiance lasers interact with complex, optically thick targets. We use x-ray backlighting and emission to measure the result of such interactions at experiments on the Omega laser and the Z-machine z-pinch facilities. In this presentation, we will show some of the images collected with a variety of experiments, we will discuss some of the difficulties we overcame, and look to issues that will arise with higher-energy lasers and larger objects.

This paper describes three diagnostics detecting optical scatter from NOVA laser targets. Detecting such scatter can help to understand instabilities in laser plasmas and to characterize such plasmas, particularly hohlraum plasmas. These diagnostics are the full aperture backscatter station (FABS), presently being built; the oblique scatter array (OSA), just starting operation; and the axial imager, also just starting operation. FABS will allow imaging at high resolution of Brillouin and Raman backscatter. The OSA provides a quantitative measurement of Brillouin and Raman scatter in many directions. The axial imager allows high‐resolution imaging of Brillouin, two‐plasmon decay and Raman scatter emitted toward the direction of the symmetry axis of the NOVA laser beams.

Achieving symmetric capsule implosions with Polar Direct Drive [S. Skupsky et al., Phys. Plasmas 11, 2763 (2004); R. S. Craxton et al., Phys. Plasmas 12, 056304 (2005); F. J. Marshall et al., J. Phys. IV France 133, 153–157 (2006)] has been explored during recent Defect Induced Mix Experiment campaign on the Omega facility at the Laboratory for Laser Energetics. To minimize the implosion asymmetry due to laser drive, optimized laser cone powers, as well as improved beam pointings, were designed using 3D radiation-hydrodynamics code HYDRA [M. M. Marinak et al., Phys. Plasmas 3, 2070 (1996)]. Experimental back-lit radiographic and self-emission images revealed improved polar symmetry and increased neutron yield which were in good agreement with 2D HYDRA simulations. In particular, by reducing the energy in Omega's 21.4° polar rings by 16.75%, while increasing the energy in the 58.9° equatorial rings by 8.25% in such a way as to keep the overall energy to the target at 16 kJ, the second Legendre mode (P2) was reduced by a factor of 2, to less than 4% at bang time. At the same time the neutron yield increased by 62%. The polar symmetry was also improved relative to nominal DIME settings by a more radical repointing of OMEGA's 42.0° and 58.9° degree beams, to compensate for oblique incidence and reduced absorption at the equator, resulting in virtually no P2 around bang time and 33% more yield.

Time resolved x-ray diffraction and scattering have been applied to the measurement of a wide variety of physical phenomena from chemical reactions to shock wave physics. Interest in this method has heightened in recent years with the advent of versatile, high power, pulsed x-ray sources utilizing laser plasmas, electron beams and other methods. In this article, we will describe some of the fundamentals involved in time resolved x-ray diffraction, review some of the history of its development, and describe some recent progress in the field. In this article we will emphasize the use of laser-plasmas as the x-ray source for transient diffraction.

Experiments were performed to develop a platform for the simultaneous measurement of mix and its effects on fusion burn. Two polar direct drive implosions of all-plastic capsules were conducted for the first time on the National Ignition Facility (NIF). To measure implosion trajectory and symmetry, area image backlighting of these capsules was also employed for the first time on NIF, an advance over previous 1-D slit imaging experiments, providing detailed symmetry data of the capsules as they imploded. The implosion trajectory and low-mode asymmetry seen in the resultant radiographs agreed with pre-shot predictions even though the 700 kJ drive energy produced laser beam intensities exceeding laser-plasma instability thresholds. Post-shot simulations indicate that the capsule yield was reduced by a factor of two compared to pre-shot predictions owing to as-shot laser drive asymmetries. The pre-shot predictions of bang time agreed within 200 ps with the experimental results. The second shot incorporated a narrow groove encircling the equator of the capsule. A predicted yield reduction factor of three was not observed.

The Defect Induced Mix Experiment (DIME-II) will measure the implosion and mix characteristics of CH capsules filled with 5 atmospheres of DT by incorporating mid-Z dopant layers of Ge and Ga. This polar direct drive (PDD) experiment also will demonstrate the filling of a CH capsule at target chamber center using a fill tube. Diagnostics for these experiments include areal x-ray backlighting to obtain early time images of the implosion trajectory and a multiple-monochromatic imager (MMI) to collect spectrally-resolved images of the capsule dopant line emission near bangtime. The inclusion of two (or more) thin dopant layers at separate depths within the capsule shell facilitates spatial correlation of mix between the layers and the hot gas core on a single shot. The dopant layers are typically 2 μm thick and contain dopant concentrations of 1.5%. Three dimensional Hydra simulations have been performed to assess the effects of PDD asymmetry on capsule performance.

The reflectivity of a laser due to stimulated Raman scattering (SRS) from long scale-length hohlraum plasmas is shown to depend on the damping of ion-acoustic waves. This dependence is observed in plasmas with either low or high ionization states. Since the SRS process itself is unrelated to acoustic waves, these data are evidence of a nonlinear coupling of SRS to other parametric processes involving daughter acoustic waves. {copyright} {ital 1996 The American Physical Society.}

The Trident Nd:glass ICF laser at Los Alamos National Lab may be operated in a mode that produces high energy ultrashort pulses by the chirp/compression method. The 125-ps pulses from a standard mode-locked, Nd:YLF oscillator are first frequency-broadened to 3-nm bandwidth, chirped in a quartz fiber, and then compressed with a grating pair to 1.5 ps. A second quartz fiber then provides nonlinear polarization rotation for background and satellite suppression and to further broaden the spectrum to 4.5 nm. Pulses are chirped again to 500 ps width with a second grating pair and amplified in a Ti:sapphire regenerative amplifier pumped by frequency-doubled Nd:YAG. Millijoule-level output is then amplified through the existing phosphate glass Trident amplifier chain before compression to < 400 fs. Energy up to 1.5 J with excellent beam quality and contrast ratio is routinely produced by compressing after three rod amplifier stages. Higher energies are possible by compression further along the amplifier chain. Simultaneous use of long (approximately 1 ns) pulses for plasma formation is also possible.

The interaction of intense, subpicosecond laser pulses with solid targets produces intense picosecond x‐ray pulses. With focused laser pulses of several 1018 W/cm2, He‐like and H‐like line radiation from targets such as aluminum and silicon has been produced. The energy conversion efficiency from the laser pulse energy to the 1–2 keV line x‐rays is nearly one percent. The duration of the line x‐ray radiation is of the order of ten picoseconds, although this may be an upper estimate because of the temporal resolution of the x‐ray streak camera. The spatial extent of the x‐ray source region is only slightly larger than the laser focal spot, or about 10 μm in diameter. Given these characteristics, such x‐ray sources emit an intensity of nearly 1014 W/cm2. Experiments and modeling which led to the above conclusions will be discussed.

Experiments performed with a terawatt-class laser system which is based on amplification in XeCl discharge amplifiers are described. Energy extraction in XeCl discharge amplifiers is examined experimentally and theoretically using 0.25-ps nearly transform limited pulses and both 16- and 75-ps strongly chirped pulses of the same bandwidth. We find that while the saturation fluence for the 16-ps pulse is comparable to that of the 0.25-ps pulse, stretching the pulse to a width of 75 ps increases the saturation fluence by 35%. A study of the interaction of the terawatt laser pulses with aluminum targets at irradiances exceeding 5 X 1018 W/cm2 is also presented.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A high-temperature high-pressure isoperibol calorimeter for determining the heats of solution and reaction of very dilute substances in water (10(-4) m) at temperatures up to 623 K is described. The energies of vaporization of water at steam saturation pressure were measured as a function of temperature and the results agree with the corresponding values from steam tables to better than 0.08+/-0.18%. The novelties of the present instrument relative to flow type heat capacity calorimeters are that measurements can be made at orders of magnitude lower concentrations and that measurement of heat of reaction involving solids or gases or in the presence of high concentrations of supporting electrolytes, acids, and bases is possible. Furthermore, the advantage of using enthalpy data over heat capacity data for calculations of the standard state Gibbs free energies of electrolytes is that the experimental heat data of this research need only be integrated once to derive higher temperature free energy data from lower temperatures. The derived heat capacities can be used mathematically to obtain free energies by double integration. However, the resulting errors are much smaller than if experimental aqueous heat capacities were used for the integrations.

We are investigating the generation of short pulse short wavelength x-rays for pumping inner- shell x-ray lasers by photo-ionization. In contrast with previous proposals, we are looking at the use of a single line as an efficient means of pumping these lasers. As a first step we are optimizing the flashlamp x-ray conversion efficiency and characterizing the x-ray pulse length.

The Los Alamos AURORA Laser Facility is now routinely operational at the 1-kJ level with pulses variable between 1 and 5 ns. Target physics experiments at 248 nm are now underway to characterize focal spot distributions, x-ray conversion in planar targets, and the beneficial effects of bandwidth and pulse shaping on target performance.

Au and Si targets have been irradiated using the Aurora KrF laser system, and diagnosed with x-ray and optical diagnostics. The x-ray diagnostics were sensitive to the 0.1--10 keV range. Initial, manually aligned results indicate significant plasma heating and intense x-ray production, with incident peak intensities on target of 1 {minus} 2 {times} 10{sup 14} W/cm{sup 2} in a focal spot of order 500 {mu}m diameter. Total energy delivered to the target in 36 of the available 48 target beams was approximately 1200 J in pulses with FWHM in the 3--5 ns range. M-band radiation was observed from Au foil targets. Initial bandwidth measurements on the laser indicate {approx}20 cm{sup {minus}1} without bandwidth enhancement efforts.

Lasers delivering subpicosecond pulses with energies of a fraction of a Joule have made it possible to generate irradiance levels approaching 1020 W/cm2. We presently operate two such systems, a KrF based excimer laser capable of producing a few 1017 W/cm2 at 248 nm with a repetition rate of 3–5 Hz and a XeCl based excimer laser capable of producing mid 1019 W/cm2 at 308 nm and 1 Hz. We will discuss some experimental results and the theory and modeling of the interaction of such intense laser pulses with aluminum. Because of a small ASE prepulse the high intensity interaction is not at the solid surface but rather at the ne=2×1022 cm−3 (KrF) laser critical density of the blowoff plasma generated by the ASE. The transient behavior of the plasma following the energy deposition by the intense subpicosecond pulse can be viewed as the energy‐impulse response of the plasma. Experimental results and modeling of the x‐ray emission from this plasma are presented.

A dye laser, pumped by ruby second harmonic radiation at 3471 A, emitting ∼5‐mJ, 20‐nsec pulses with a bandwidth of 0.3 A, has been developed as a light source in a schlieren optical system which utilizes enhanced refractivity to examine plasma flow phenomena. When the dye laser is tuned adjacent to the BaII ion resonance line at 4554 A, the sensitivity of the system to density gradients in a barium plasma becomes 100–1000 times greater than can be achieved with nonresonant light sources which rely on the free electron contributions to plasma refractivity. Absorption effects also yield data on plasma flow patterns.

A subpicosecond laser is focused to ${10}^{17}$ W/${\mathrm{cm}}^{2}$ to create an extremely transient Al plasma with a kV radiation time short compared to most of the excitation times. High-resolution spectroscopy is used to analyze the kV line emission from the He- and H-like ions and to determine that the plasma reaches a temperature near 1 keV and cools in less than 10 ps.

The partial molal entropies for oxy‐anions and related species have been correlated as a function of the charge, interatomic distance, and certain structural factors. An equation is given by which the entropy for unknown species can now be estimated fairly accurately. In the few cases where the method does not give good agreement, the data are open to suspicion as indicated by other independent observations. Some applications and extensions of the method are indicated for future study.

A method for estimating the entropy of complex aqueous organic solutes and related species has been developed by a structural extension of a method of Powell and Latimer for simple solutes. The agreement between calculated and observed values is, in general, good, although systematic deviations begin to occur for very complicated and large solutes. The method is extended to the calculation of the entropies of charged organo‐metallic complex ions with good success, and possible applications to systems of biological interest are indicated.Subsequent to the development of the general method for estimating the entropies of aqueous solutes, an empirical equation is also given for calculating gaseous entropies of both inorganic (ionic) and organic molecules from their structures.

Measurements of the thermodynamic properties of electrolytes in hot water have a widespread practical and theoretical interest. The chemistry of many solutes changes rapidly as a solution is heated but the reasons for such changes have not been understood in terms of electrolyte theory. The temperature behaviour of the equilibrium thermodynamic properties is best seen by examining the ionic heat capacities of representative electrolytes, and we report here measurements just completed of C°p2 of NaCl(aq) and BaCl2 (aq) up to 300 °C. The values are so negative that we now believe that the properties of electrolytes at higher temperatures are determined primarily by the electrostatic field of the ions and the bulk dielectric constant of water, and not by structural arrangements of ions and water molecules which characterize solutions at lower temperatures. These new phenomena are summarized in Fig. 1, which not only illustrates the large values at 300 °C for C°p2 for NaCl (aq) and BaCl2 (aq) of −339 and −1,011 cal mol−1 deg−1, but also indicates a continued rapid change above 300 °C. The observations also suggest a need for reexamination of the theory of aqueous electrolytes at 25 °C, a temperature in the transition region between the two types of behaviour.