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Neutron irradiation of a molten salt tritium breeder is planned to evaluate tritium accountancy in the liquid immersion blanket robust accountancy (LIBRA) project at MIT. A sealed-tube deuterium-tritium (DT) fusion neutron generator (NG) will be used for the irradiation. Hence, the NG’s characterization is necessary to evaluate the tritium accountancy. Specifically, the neutron profile, energy, and flux are essential factors for the analysis in the irradiation experiment. This study aims to investigate the neutron distribution around the NG for the characterization of a DT fusion neutron environment. First, neutrons on the outer surface of the generator were measured using an imaging plate (IP) and aluminum (Al) activation foils. The obtained image reflected the $\beta $ -ray emission from Al activated by fast neutrons. Next, the single-crystal chemical vapor deposition (sCVD) diamond detector was also employed to measure the angular dependence of neutron energy from the generator axis of symmetry. Using the angular distribution of neutron energy, the IP image was corrected. The neutron energy distribution and the energy-corrected spatial distribution around the generator were obtained by these methods. The image contains information about the neutron profile which can be utilized for the analysis of the fusion neutron field.

Measurement of thermal and epithermal neutron spatial distribution inside the fusion breeding blanket is essential for evaluating tritium breeding performance. This work aims to establish the method to measure thermal and epithermal neutron fluxes in the breeding blanket by employing a combination of different material foils and utilizing the differences between the various ( $n$ , $\gamma$ ) reaction cross sections. Material foils were installed inside blanket mock-ups composed of polyethylene graphite and were subsequently activated by neutron irradiation generated by deuterium–deuterium (DD) fusion reactions. Activation analyses were performed and compared with simulated results obtained by both neutron transport and activation analysis codes. Material foils were activated by neutron irradiation with an average neutron production rate (NPR) of 1.22– $1.31\times 10^{7}$ n/s for multiple irradiation experiments. The $\beta $ - and $\gamma $ -rays emitted during each decay process were measured on an imaging plate of 2-D radiation dosimeters. The detection range at measured positions was between $2\times 10^{-3}$ and $5\times 10^{-2}$ cm2/n, and calculation-to-experimental (C/E) values were 0.27–2.4 for the graphite mock-up and 0.30–3.0 for the polyethylene mock-up. These results suggest that the measurement of thermal and epithermal neutron spatial distribution can be obtained in the blanket, while the accuracy of the activation analysis using the imaging plate is required to be improved for the evaluation of tritium production.

This article outlines Kyoto Fusioneering’s (KF’s) initial engineering and development activities for its self-cooled lithium lead-type blanket: Self-Cooled Yuryo Lithium-Lead Advanced (SCYLLA©). We provide details on overall design, including an initial tritium breeding ratio (TBR) assessment via neutronics analysis, as well as the status of SCYLLA©-relevant R&D. This includes silicon carbide composite (SiCf/SiC) manufacturing techniques, tritium extraction, materials compatibility, and heat transfer, which are being explored via collaboration with Kyoto University. Results of previous work in relation to this R&D are presented. Permeability coefficients indicate a promising property of SiCf/SiC tritium hermeticity at high temperatures. Tritium extraction technology via vacuum sieve tray (VST) is shown to be demonstrated at engineering scale. A local TBR of up to 1.4 can be achieved with the SCYLLA© configuration. Fabrication methods for various SiCf/SiC components including the blanket module, heat exchanger, and flow path components are provided. A tritium compatible high-temperature SiCf/SiC heat exchanger is discussed. Commercial viability and reactor adaptability are considered as a theme throughout. Finally, KF’s plans to build a facility for demonstration reactor relevant testing of a SCYLLA© prototype in the mid-2020s, which will provide a significant step toward commercial fusion energy, are presented.

In a DEMO fusion reactor, it is necessary to continuously extract deuterium and tritium from the unburned fuel gas under divertor panels. For the pumping system in the divertor, a new method of transferring hydrogen isotope using proton conductors has been proposed. In this study, we have constructed a new experimental setup using a proton conductor to simulate a divertor pumping system, which extracts hydrogen isotope selectively. Pellets of yttrium-doped cerium oxide and indium-doped zirconium oxide were used as proton conductors. The hydrogen partial pressure on the anode side was set at the atmospheric pressure level and that on the cathode side at $10^{2}$ Pa. A dc current was applied to the proton conductor cell to selectively transfer hydrogen isotopes. The experiments were conducted in the temperature range of 400 °C- 600 °C. Gas analysis of the transported hydrogen isotopes was carried out using H2 and D2 gas mixture to obtain the transport number. Based on the data obtained from these experiments, the main parameters such as the total area of the proton conductor and the operating conditions are discussed.

A glow discharge (GD) fusion neutron source that utilizes nuclear fusion reactions of deuterium has been upgraded. The fusion reactions in this device mainly occur by collisions between the charged or neutral particles and the hydrogen isotopes trapped at the surface of electrodes. In addition, it is known that the metal hydride coating on the electrode enhances the neutron production rate (NPR). Therefore, the elemental distribution, including deuterium, in the depth direction on the electrode is an essential factor in neutron production. However, the distribution on the electrode has not been experimentally investigated. This study aims to analyze the distribution experimentally and indicate the effect of the metal hydride coatings. To achieve this purpose, we prepared the titanium (Ti)-coated cathode and the uncoated cathode, of which the base material was stainless steel. After that, the neutron production test was performed in the range of from 5- to 40-mA currents and from 20- to 60-kV applied voltage. This test indicated that the NPR was improved by coating the cathode with Ti than the uncoated cathode. In addition, depth profiling on the cathodes by glow discharge optical emission spectroscopy (GD-OES) was performed. While the analysis indicated that the concentration of deuterium on both cathodes was increased after the test, there was no significant difference in the concentration of deuterium between both cathodes. Furthermore, the concentration of Ti on the Ti-coated cathode was vastly decreased. The cause of these changes needs to be investigated.

We propose a polarization-controlled ultrasmall single-photon emitter that combines a single photon source and an elliptical split ring (SR) type metamaterial element. Simulations using the finite difference time domain method showed that in elliptical metamaterial elements, the annular mode is suppressed and axial electric field oscillations occur preferentially, resulting in upward light emission from the photon source with controlled polarization. We fabricated prototype devices by focused ion beam lithography and PbS quantum dots. Evaluation of the optical properties of the devices revealed that the emission spectrum width was narrower and the emission lifetime was shorter than those of quantum dot ensemble, and that the polarization was controlled along the minor axis of ellipse. These suggested that the quantum dot emission and the metamaterial element resonated as expected. The combination of a single quantum dot and a single elliptical SR-type metamaterial element was shown to have the potential to operate as a polarization-controlled single-photon emitter.

Bursts of gamma ray showers have been observed in coincidence with downward propagating negative leaders in lightning flashes by the Telescope Array Surface Detector (TASD). The TASD is a 700‐km2cosmic ray observatory located in southwestern Utah, USA. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower‐producing flashes were obtained with a 3‐D lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases colocated with the TASD. National Lightning Detection Network information was also used throughout. The showers arrived in a sequence of 2–5 short‐duration (≤10 μs) bursts over time intervals of several hundred microseconds and originated at an altitude of ≃3–5 km above ground level during the first 1–2 ms of downward negative leader breakdown at the beginning of cloud‐to‐ground lightning flashes. The shower footprints, associated waveforms and the effect of atmospheric propagation indicate that the showers consist primarily of downward‐beamed gamma radiation. This has been supported by GEANT simulation studies, which indicate primary source fluxes of ≃1012–1014photons for 16° half‐angle beams. We conclude that the showers are terrestrial gamma ray flashes, similar to those observed by satellites, but that the ground‐based observations are more representative of the temporal source activity and are also more sensitive than satellite observations, which detect only the most powerful terrestrial gamma ray flashes. Gamma ray showers have been detected in a surface scintillator array coincident with lightning observed by a lightning mapping array or Delta EantennaThe showers were produced less than 4–5 km above ground in the first 1–2 ms of downward negative breakdown during cloud‐to‐ground flashesThe source durations are better resolved than for satellite observations and are consistent with being produced by stepping of the initial leader breakdown

Classical novae are phenomena caused by explosive hydrogen burning onto an accreting white dwarf. Only one classical nova had been identified in X-rays before the actual optical outburst occurred (V2487 Oph). The recently discovered nova, V2491 Cyg, is one of the fastest (He/N) novae observed to date. Using archival ROSAT, XMM-Newton, and Swiftdata, we show that V2491 Cyg was a persistent X-ray source during its quiescent time before the optical outburst. We present the X-ray spectral characteristics and derive X-ray fluxes. The pre-outburst X-ray emission is variable, and, at least in one observation, it exhibits a soft X-ray source.

Aims. We determine the nature of the intermediate polar candidates XSS J00564+4548, IGR J17195–4100, and XSS J12270–4859.

Aims.We present the first X-ray observations with the XMM-Newton and INTEGRAL satellites of the recently discovered cataclysmic variable 1RXS J173021.5-055933, together with simultaneous UV and coordinated optical photometry aiming at characterising its broad-band temporal and spectral properties and classifying this system as a magnetic one.

Aims.We intend to establish the X-ray properties of Swift J0732.5–1331 and therefore confirm its status as an intermediate polar.

Context.XY Ari is the only intermediate polar to show deep X-ray eclipses of its white dwarf. Previously published observations with Gingaand Chandrahave also revealed a broad X-ray orbital modulation, roughly antiphased with the eclipse, and presumed to be due to absorption in an extended structure near the edge of an accretion disc. The X-ray pulse profile is generally seen to be double-peaked, although a single-peaked pulse was seen by RXTEduring an outburst in 1996.

Aims.XMM-Newton observations to determine for the first time the broad-band X-ray properties of the faint, high galactic latitude intermediate polar UU Col are presented.

We investigated effects of interface roughness on the local valence electronic structures at SiO2/Si interface in order to clarify the relation between interface structures and interface electronic properties, by using soft X-ray absorption and emission spectroscopy. For atomically smooth interface, the local valence structures depend on intermediate oxidation states at the interface. For atomically rough interface, on the other hand, the local valence structures at the interface show amorphous-like electronic states irrespective of the intermediated oxidation states.

We present an analysis of 30 archival ASCAand RXTEX-ray observations of 16 intermediate polars to investigate the nature of their orbital modulation. We show that X-ray orbital modulation is widespread amongst these systems, but not ubiquitous as indicated by previous studies that included fewer objects. Only seven of the sixteen systems show a clearly statistically significant modulation depth whose amplitude decreases with increasing X-ray energy. Interpreting this as due to photoelectric absorption in material at the edge of an accretion disc would imply that such modulations are visible for all system inclination angles in excess of 60 degrees. However, it is also apparent that the presence of an X-ray orbital modulation can appear and disappear on a timescale of ~years or months in an individual system. This may be evidence for the presence of a precessing, tilted accretion disc, as inferred in some low mass X-ray binaries.

We report on the first pointed X-ray observations with XMM-Newtonand RXTEsatellites of the X-ray source RX J0757.0+6306 = HT Cam. We detect a strong 515 s X-ray modulation confirming the optical photometric period found in 1998, which definitively assigns this source to the intermediate polar class of magnetic cataclysmic variables. The lack of orbital sidebands in the X-rays indicates that the X-ray period is the spin period of the accreting white dwarf. Simultaneous ultraviolet and optical B-band photometry acquired with the XMM-Newton Optical Monitor and coordinated optical UBVRIphotometric data acquired at the Nordic Optical Telescope (La Palma) show that the optical pulse is in phase with the X-rays and hence originates in the magnetically-confined accretion flow. The lack of ultraviolet spin modulation suggests that accretion-induced heating on the white dwarf surface is not important in this source. Spectral analyses of XMM-Newton EPIC and RGS data show that HT Cam has a multi-temperature spectrum and, contrary to most intermediate polars, it does not suffer from strong absorption. With its 86 min orbital period, HT Cam is the third confirmed system of this class below the 2–3 h period gap accreting at a low rate.

We present broad-band (0.1–90 keV) spectral and temporal properties of the three Intermediate Polars, RE 0751+144 (PQ Gem), RX  J0558.0+5353 (V405 Aur) and RX  J1712.6-2414 (V2400 Oph) based on simultaneous soft and hard X-ray observations with the BeppoSAX satellite. The analysis of their spectra over the wide energy range of BeppoSAX instruments allows us to identify the soft and hard X-ray components and to determine simultaneously their temperatures. The black–body temperatures of the irradiated poles of the white dwarf atmosphere are found to be 60–100 eV, much higher than those found in their synchronous analogues, the Polars. The temperature of the optically thin post–shock plasma is well constrained in RX  J1712.6-2414 and in RE 0751+144 (13 and 17 keV) and less precisely determined in RX  J0558.0+5353. In the first two systems evidence of subsolar abundances is found, similarly to that estimated in other magnetic Cataclysmic Variables. A Compton reflection component is present in RX  J0558.0+5353 and in RE 0751+144 and it is favoured in RX J1712.6-2414. Its origin is likely at the irradiated white dwarf surface. Although these systems share common properties (a soft X-ray component and optical polarized radiation), their X-ray power spectra and light curves at different energies suggest accretion geometries that cannot be reconciled with a single and simple configuration.

We report on the first far-UV observations of the asynchronous polar BY Cam made by the Far-Ultraviolet Spectroscopic Explorer (FUSE). The source is known to exhibit the most extreme NV/CIV emission resonance line ratio observed among polars. The FUSE observations reveal a OVI resonance line weaker than in the prototype of polars, AM Her, with the absence of a detectable narrow component. The OVI broad line is detected with an equivalent width of the same order as in AM Her, the blueward doublet component is clearly present but the redward component is strongly affected by H2absorption. The presence of a strong NIII line and weak CIII lines also confirms the peculiar CNO line flux. We compare the resonance CNO line intensities with the predictions of the CLOUDY plasma code coupled to a geometrical model of the accretion column. Varying the temperature and/or intensity of the ionising spectrum is unable to reproduce the observed broad line ratios. A solution is obtained by significantly altering the element abundances with a strong depletion of C, overabundance of N and a weak underabundance of O. This confirms previous suggestions of non-solar abundances which may result from redistribution in the accreted material following nova outbursts and/or the secondary nuclear evolution. A very significant H2absorption is observed in front of the source, a possible indication for either the existence of a dense interstellar cloud or of circumstellar material.

We combine ASCA and RXTE data of V1062 Tau to confirm the presence of a 62-min X-ray pulsation. We show that the pulsation is caused largely by the variation of dense partial absorption, in keeping with current models of accretion onto magnetic white dwarfs. Further parametrisation of the spin pulse is, however, hampered by ambiguities in the models.

We present optical photometry, spectroscopy and photopolarimetry, as well as ASCAX-ray observations, of the recently discovered intermediate polar 1WGA J1958.2+3232. Through the first detection of an optical beat frequency, we confirm the previously tentative suggestion that the spin period of the white dwarf is twice the X-ray and optical pulsation period, which we also confirm in each case. We detect an orbital modulation in each of the U, B, V, Rand Ibands for the first time, and suggest that the true orbital period is the -1d alias of that previously suggested. We also confirm the presence of circular polarization in this system, detecting a variable polarization which has opposite signs in each of the Band Rbands. The double peaked pulse profile and oppositely signed polarization pulses suggest that 1WGA J1958.2+3232 accretes onto both magnetic poles via a disc which is truncated relatively close to the white dwarf.

We present X-ray observations of the high-inclination low-mass X-ray binary system X2127+119 (AC 211) in the globular cluster M 15 (NGC 7078). The observations consist of data acquired in 1996 with the RXTEsatellite and in 1995 with the ASCAsatellite. Also, the MPC1 data from the 1988 GINGAobservations were de-archived and re-analysed. The phase-folded 2–10 keV hardness ratios from all three missions differ significantly indicating that the system can exhibit different spectral behaviours. We find that the X-ray eclipse profiles can be described relatively well using a simple model where the secondary star passes in front of a large X-ray emitting region. For this we require a mass ratio $(q=M_{1}/M_{2})$of about one. The radius of this X-ray emitting region is ${\sim}0.8~R_{\rm L1}$and its vertical extent ${\sim}60^{\circ}$above the orbital plane. We suggest that if this X-ray emitting region were an optically thick corona, it would explain various puzzling aspects of this system. We also show that the X-ray dip observed at phases around 0.65 does not conform with the idea that the dip is caused by vertically extended material associated with the stream/disc impact region, but that it could be due to structure in the inner parts of the disc.

We present RXTE and BeppoSAX observations of the Intermediate Polar V 709 Cas acquired in 1997 and 1998 respectively. The X-ray emission from 0.1 to 30 keV is dominated by the strong pulsation at the rotational period of the white dwarf (312.8 s) with no sign of orbital or sideband periodicity, thus confirming previous ROSAT results. However, we detect changes in the power spectra between the two epochs. While the second harmonic of the spin period is present during both observations, the first harmonic is absent in 1997. An increase in the amplitude of the spin pulsation is found between 1997 and 1998 together with a decrease in the X-ray flux. The average X-ray spectrum from 0.1 to 100 keV is well described by an isothermal plasma at ~27 keV plus complex absorption and an iron Kαfluorescent line, due to reflection from the white dwarf surface. The rotational pulsation is compatible with complex absorption dominating the low energy range, while the high energy spin modulation can be attributed to tall shocks above the accreting poles. The RXTE spectrum in 1997 also shows the presence of an absorption edge from ionized iron likely located in the pre-shock accretion flow. The variations along the spin period of the partial covering absorber and of reflection are compatible with the classical accretion curtain scenario. The variations in the spin pulse characteristics and X-ray flux indicate that V 709 Cas experiences changes in the mass accretion rate on timescales from months to years.

AbstractIn the medium-sized heliotron device Heliotron J, edge density fluctuation has been measured simultaneously with a high-speed video camera and a Langmuir probe. Poloidally propagating, parallel elongating filamentary structures with 20- to 30-kHz frequency and ~14-cm poloidal wavelength were observed by a camera. However, the radial position of this density mode is not well known with only camera data because the camera lens axis is perpendicular to the torus plane. To identify the span of this density mode, plasma-surface interaction (PSI) between the probe and the plasma has been analyzed. As the probe scanned into the plasma, enhanced brightness due to PSI was clearly observed in camera images. By comparing this enhanced brightness among different probe positions, the outmost margin of the 20- to 30-kHz mode observed by the camera has been identified to be within 10 mm outside from the last closed flux surface. This conclusion is supported by the spectrum of the probe data.

Aims. We aim to establish the X-ray properties of the intermediate polar candidate IGR J15094–6649 and therefore confirm its inclusion into the class.

AbstractExperimentally measured cross sections are presented for the natCu(a, xn)66,67,68Ga and 68Zn(p, xn)67,68Ga nuclear processes up to 36 and 20 MeV, respectively. Based on these results and the reliable cross section data available in the literature, the possible thick target yields were also calculated. Two different 68Ga production routes (Cu+aand Zn+p) are discussed in detail, especially with regard to the 66Ga and 67Ga contamination levels as a function of the target enrichment level and the incident bombarding energies. Both processes can be used for in-house 68Ga production with low (<1%) 66Ga and/or 67Ga EOB contamination using enriched 68Zn (>80%) or 65Cu (>95%) target. The maximum available yield on 100% enriched 68Zn and 65Cu (irradiation time: 2.25 h; bombarding energy: Ep=20 MeV and Ea=18 MeV) is 352.45 mCi/µA (13.04 GBq/µA) and 14.28 mCi/µA (528.36 MBq/µA), respectively.

In a dwarf nova, the accretion disk around the white dwarf is a source of ultraviolet, optical, and infrared photons, but is never hot enough to emit X-rays. Observed X-rays instead originate from the boundary layer between the disk and the white dwarf. As the disk switches between quiescence and outburst states, the 2-10 keV X-ray flux is usually seen to be anticorrelated with the optical brightness. Here, we present RXTEmonitoring observations of two dwarf novae, VW Hyi and WW Cet, confirming the optical/X-ray anticorrelation in these two systems. However, we do not detect any episodes of increased hard X-ray flux on the rise (out of two possible chances for WW Cet) or the decline (two for WW Cet and one for VW Hyi) from outburst, attributes that are clearly established in SS Cyg. The addition of these data to the existing literature establishes the fact that the behavior of SS Cyg is the exception, rather than the archetype as is often assumed. We speculate on the origin of the diversity of behaviors exhibited by dwarf novae, focusing on the role played by the white dwarf mass.

Context. A significant number of cataclysmic variables have been detected as hard X-ray sources in the INTEGRAL survey, most of them of the magnetic intermediate polar type.Aims. We present a detailed X-ray broad-band study of two new sources, IGR?J00234+6141 and 1RXS?J213344.1+510725, that allow us to classify them as secure members of the intermediate polar class.Methods. Timing and spectral analysis of IGR?J00234+6141 are based on an XMM-Newton observation and INTEGRAL publicly available data. For 1RXS?J213344.1+510725, we use XMM-Newton and Suzaku observations at different epochs, as well as INTEGRAL publicly available data.Results. We determine a spin period of 561.64?? 0.56?s for the white dwarf in IGR?J00234+6141. The X-ray pulses are observed up to ?2?keV. From XMM-Newton and Suzaku observations of 1RXS?J213344.1+510725, we find a rotational period of 570.862?? 0.034?s. The observations span three epochs where the pulsation is observed to change at different energies both in amplitude and shape. In both objects, the spectral analysis spanned over a wide energy range, from 0.3 to 100?keV, shows the presence of multiple emission components absorbed by dense material. The X-ray spectrum of IGR?J00234+6141 is consistent with a multi-temperature plasma with a maximum temperature of ?50?keV. In 1RXS?J213344.1+510725, multiple optically thin components are inferred, as well as an optically thick (blackbody) soft X-ray emission with a temperature of ?100?eV. This adds 1RXS?J213344.1+510725 to the growing group of soft X-ray intermediate polars.Conclusions. Though showing similar rotational periods and being hard X-ray sources, these two intermediate polars appear different in several respects, among which the presence of a soft X-ray component in 1RXS?J213344.1+510725. This source also emits circularly polarized light in the optical band, thus joining the group of soft and polarized intermediate polars as a fifth member. How the hard X-ray and polarized emission are thermalized in these systems is a timely question.

Aims. We analyze the first X-ray observations with XMM-Newton of 1RXS?J070407.9+262501 and 1RXS?180340.0+401214, in order to characterize their broad-band temporal and spectral properties, also in the UV/optical domain, and to confirm them as intermediate polars.Methods. For both objects, we performed a timing analysis of the X-ray and UV/optical light curves to detect the white dwarf spin pulsations and study their energy dependence. For 1RXS?180340.0+401214 we also analyzed optical spectroscopic data to determine the orbital period. X-ray spectra were analyzed in the 0.2?10.0?keV range to characterize the emission properties of both sources.Results. We find that the X-ray light curves of both systems are energy dependent and are dominated, below 3?5?keV, by strong pulsations at the white dwarf rotational periods (480?s for 1RXS?J070407.9+262501 and 1520.5?s for 1RXS?180340.0+401214). In 1RXS?180340.0+401214 we also detect an X-ray beat variability at 1697?s which, together with our new optical spectroscopy, favours an orbital period of 4.4?h that is longer than previously estimated. Both systems show complex spectra with a hard (temperature up to 40?keV) optically thin and a soft (kT ~ 85?100?eV) optically thick components heavily absorbed by material partially covering the X-ray sources.Conclusions. Our observations confirm the two systems as intermediate polars and also add them as new members of the growing group of ?soft? systems which show the presence of a soft X-ray blackbody component. Differences in the temperatures of the blackbodies are qualitatively explained in terms of reprocessing over different sizes of the white dwarf spot. We suggest that systems showing cooler soft X-ray blackbody components also possess white dwarfs irradiated by cyclotron radiation.

We investigated effects of interface roughness on the local valence electronic structures at SiO2/Si interface in order to clarify the relation between interface structures and interface electronic properties, by using soft X-ray absorption and emission spectroscopy. For atomically smooth interface, the local valence structures depend on intermediate oxidation states at the interface. For atomically rough interface, on the other hand, the local valence structures at the interface show amorphous-like electronic states irrespective of the intermediated oxidation states.

This contribution describes part 1 of process development of a novel aldose reductase inhibitor FK366 (1). The original process applied on a laboratory scale was improved from the safety viewpoint to manufacture materials on 500-L scale suitable for toxicological and pharmacological evaluations. A new process, including regioselective alkylation of silylated quinazolinedione, provided a practical and cost-effective synthesis of FK366 in a dramatically increased yield.

Accretion in white–dwarf binary systems can occur through discs, accretion columns or a combination of these, depending on the magnetic field of the white dwarf. Recent high–quality X–ray observations with the XMM–Newton and Chandra observatories have significantly advanced our understanding of the physics of the accretion process, and place severe tests on our existing models. There have been some surprises, such as the strong dependence of atmospheric heating on accretion rate. However, we believe that we are now confident that we understand in general the physical processes in the accretion region, although some complicating factors, such as absorption, remain. We also discuss new developments in ultra–short–period white–dwarf binary systems.

Magnetic susceptibilities (χM) of three kinds of 3-(aryl-substituted)-1,5-diphenyl-verdazyl radical crystals (aryl:  4-fluorophenyl (p-FPDV), 4-pyridyl (p-PyDV), and 3-pyridyl (m-PyDV)) have been measured between 1.8 and 300 K, showing a broad maximum Tmax at 200, 272, and 157 K, respectively. The values of Tmax observed are 1 or 2 orders of magnitude larger than those for usual organic neutral radical crystals, suggesting strong intermolecular antiferromagnetic (AFM) exchange interactions (J) in the crystals. The temperature dependence of the susceptibilities cannot be explained by a simple model, such as the one-dimensional (1D) Heisenberg AFM linear- and alternating-chain model. The values of χM observed for the p-FPDV, p-PyDV, and m-PyDV radicals are about 42, 76, and 35% larger than the corresponding values calculated by a 1D Heisenberg AFM linear-chain model at each temperature. The result of the crystal structure analysis of p-FPDV indicates the existence of butterfly-type spin frustration in the system. The origin of the anomalous magnetic behavior observed for these verdazyl radical crystals has been discussed based on the results of the crystal structure analysis and unpaired spin density calculation.

Doping effect of nonmagnetic impurities, p-CyDOV-H (reduced form of p-CyDOV), on the organic spin-Peierls (SP) system, 3-(4-cyanophenyl)-1,5-dimethyl-6-oxoverdazyl (p-CyDOV) radical crystal, has been studied by measuring the temperature dependence of the magnetic susceptibility (T = 2.0−300 K) and the field dependence of the magnetization (H = 0−55 T) of the diluted p-CyDOV radical crystals, (p-CyDOV)1-x(p-CyDOV-H)x (x = 0, 0.01, 0.03, 0.05, 0.07, and 0.10). The effect of doping on SP system is very remarkable. The SP transition temperature (TSP = 15.0 K) decreases rapidly upon p-CyDOV-H doping and the SP state almost disappears in the lightly doped sample with x = 0.05. The susceptibility and magnetization of diluted radical crystal with x = 0.01 and 0.03 below TSP can be explained by the sum of the susceptibilities and magnetizations of the spin-Peierls state, antiferromagnet, and Curie impurity, respectively, indicating the coexistence of SP and antiferromagnetic phases in the doped SP system at low temperature. This work is the first report of the high-field magnetization study of the doping effect of nonmagnetic impurities on the organic SP transition system.

Previous investigations on the effects of temperature and impurities on the surface tension of molten silicon, and relevant measurement methods have been reviewed, and the influence of oxygen partial pressure (PO2) in the atmosphere has been analyzed emphatically, on the basis of the results obtained by the sessile drop method and calculations. In the case of PO2 ≤ PO2,sat (the saturated oxygen partial pressure in the Si(l)−O2(g)−SiO2(s) system), the surface tension first remains almost constant and then decreases remarkably with the increase of PO2, the temperature coefficient of surface tension (∂σ/∂T) is negative and increases with the oxygen partial pressure, and the molten silicon drop is very sensitive to outside vibrations. However, in the case of PO2 > PO2,sat, the surface tension increases slightly with the oxygen partial pressure, ∂σ/∂T is higher and also increases with PO2, the molten silicon drop is not influenced by environmental disturbances and remains stable, and EPMA (electron probe microanalyzer) analysis indicates the formation of a thin SiO2(s) film on the surface of the molten silicon drop which might account for the surface tension increase.

Adsorbed states of cyclopentene on Si(100)(2×1) have been investigated by means of low energy electron diffraction (LEED), valence and Si 2p photoelectron spectroscopy (PES) using synchrotron radiation, and high-resolution electron energy loss spectroscopy (HREELS). Valence and Si 2p PES results indicate that the dangling bonds of the Si(100)(2×1) dimer and the π-bond of cyclopentene interact with each other, resulting in the formation of Si−C bonds. The valence electronic structure of adsorbed cyclopentene is similar to that of gas-phase cyclopentane. In addition, the HREELS spectra of cyclopentene on Si(100)(2×1) resemble the vibrational spectra of free cyclopentane and the cyclopentene di-σ bonded to Pt(111). Therefore, we conclude that cyclopentene is di-σ bonded to the Si(100)(2×1) surface and the molecular structure is similar to that of cyclopentane (all the carbon atoms are in sp³ state); the possible adsorbed structures are discussed. At saturation, 76% of the dimers are reacted, indicating that the unreacted dimer sites exist owing to the steric hindrance of adjacent molecules.

The adsorption state of 1,4-cyclohexadiene on a Si(100)(2×1) surface is studied with synchrotron radiation photoelectron spectroscopy (PES), high-resolution electron energy loss spectroscopy (HREELS), and scanning tunneling microscopy (STM). The existence of one π bond in the chemisorbed 1,4-cyclohexadiene is confirmed by valence band PES and HREELS measurements. The bonds between the 1,4-cyclohexadiene molecule and Si surface are characterized by the observation of a Si−C stretching mode in HREEL spectra and the interface component due to the Si−C bond in high-resolution Si 2p spectra. The remaining outermost π states in the adsorbed molecule are observed directly in the STM images. From HREELS and PES results, it is also clarified that the chemisorption state is basically invariable at any coverage.

The models of vitamin K and vitamin E linked molecule, (1-(1,4-naphthoquinone-2-oxy)-6-(hydroxy-2,5,7,8-tetramethylchroman-2-carbonyloxy)-hexane), was synthesized as a model of vitamin K and vitamin E which coexist in biological membranes. The time-resolved EPR (TR-EPR) spectra of this molecule could be assigned to vitamin K and E radicals and showed that the excited triplet state of the vitamin K moiety was rapidly quenched by abstraction of hydrogen from the vitamin E moiety. The broad and emissive CIDEP spectra observed in ethanol suggested that the intramolecular interaction between vitamin K and vitamin E radicals was strong there. The relatively resolved spectra observed in a TX-100 micelle system, on the other hand, indicated that the interaction between these radicals was very weak. These results suggest that the vitamin K and E radicals existed around the water−oil interface of the micelle independently. The absence of a deuterium effect in our experiments showed that tunneling does not contribute significantly to the quenching reaction.