The study of orbital ordering with resonant x‐ray scattering

Japan has nearly 50 years of history in synchrotron radiation (SR) research and has realized the importance of synchrotron radiation in science advancement since the very beginning. As a result, many SR facilities have been constructed. Today, there are eight SR facilities in operation and three facilities under construction in Japan. Figure 1 shows the location of these facilities with their opening years. Japan has built the world's largest storage ring with circumference of 1.4 km (SPring-8) and the world's smallest ring with circumference of 3 m (Ritsumeikan SRC).     

Experimental study of conversion from atomic high—order harmonics to x—ray emissions

There are two physical phenomena in a strong laser intensity. One is the high-order harmonic emission; the other is x-ray emission from optical-field ionized plasmas. The experiment of conversion from high-order harmonics to x-ray emissions was given with a 105fs Ti:sapphire laser by adjusting laser intensities. The ingredient in plasma was investigated by the numerical simulations.Our experimental results suggested that the free electrons have detrimental effects on harmonic generation but are favourable for x-ray emission from optical-field ionized plasmas. If we want to obtain more intense harmonic signals as a coherent light source in the soft x-ray region, we must avoid the production of free electrons in plasmas. At the same time, if we want to observe x-rays for the development of high-repetition-rate table-top soft x-ray lasers, we should strip all atoms in the plasmas to a necessary ionized stage by the optical-field-ionization in the field of a high-intensity laser pulse.     

Superconductivity and x—ray photoemission study of MgB2 thin films

Highly c-axis oriented MgB2 thin films with Tc^onset of 39.6K were fabricated by magnesium diffusing into pulsedlaser-deposited boron precursors.The estimation of critical current density Jc,using hysteresis loops and the Bean model,has given the value of 10^7A/cm^2(15K,0T),which is one of the highest values ever reported.The x-ray photoemission study of the MgB2 thin films has revealed that the binding energies of Mg 2p and B 1s are at 49.4eV and 186.9eV,which are close to those of metallic Mg and transition-metal diborides,respectively.     

Ultrafast time‐resolved X‐ray absorption spectroscopy of chemical systems

The semiconductor industry continues in its relentless march to miniaturization [1 See, for instance http://www.itrs.net/Links/2007ITRS/2007_Chapters/2007_Lithography.pdf  [Google Scholar]]. Every four years or so, the dimensions of the features on an integrated circuit are halved, yielding an increase in density and functionality of the electronic “chip.” The economic advantages of more devices per unit area outweigh increases in fabrication costs and performance limitations, pushing the industry to seek ever-smaller patterns. At the time of writing (April 2008) advanced devices are patterned with the smallest features hovering around 45 nm, and the next generation of ～32 nm devices is on the horizon. What is perhaps most remarkable is that this level of nanopatterning is achieved with optical imaging tools and processes that use an actinic wavelength of 193 nm, the ArF laser emission line. As taught in any elementary physics textbook, the wavelength of light ultimately limits the achievable optical resolution [2 Hecht, E. and Zajac, A. 2002. Optics. Addison Wesley, : 471–474.  [Google Scholar]]. So how can we pattern 32 nm features using 193 nm radiation?     

Techniques for inelastic X‐ray scattering with μeV‐resolution

A new spectroscopic technique is introduced that allows tuning of a eVwide beam of synchrotron radiation over a range of a few meV. It relies on nuclear resonant scattering that is subject to the Doppler effect in high speed rotary motion. Two mechanisms are discussed how to extract the resonantly scattered radiation out of the broad band of synchrotron radiation: (a) grazing incidence reflection from a rotating disk in combination with a polarization filtering technique and (b) deflection of resonantly scattered radition via the recently discovered Nuclear Lighthouse Effect. Implications for inelastic Xray scattering and elastic nuclear resonant scattering are discussed.     

X‐ray microscopy at the advanced photon source

In modern third generation synchrotron sources, undulators have become the principal source of X-rays and today a brilliance close to 10²¹ photons/sec?mm²?mrad?0.1%BW is routinely attained for photon energies of 10 keV. However, generating brilliant beams of photons with energies of 50 keV and above leads to conflicting choices for the undulator parameters as the following analysis shows.     

X‐ray sources for studies of ultrafast processes

Radio signals from Jupiter were first detected in 1955 in the radio range at a frequency of 22.2 MHz. The emissions were sporadic in character, and were confined to frequencies below 40 MHz. These decametric (DAM) emissions have been interpreted as coherent cyclotron radiation from electrons in the tens of keV range. The innermost jovian moon Io, which orbits Jupiter in only 1.8 days, appears to modulate the emission: both the intensity and the probability of the occurrence of bursts increase when Io is at certain locations in its orbit with respect to Jupiter and the observer. The emissions originate in Jupiter's aurora, being produced by electrons that travel along magnetic field lines. Particles that enter the atmosphere may locally excite atoms and molecules, which upon de-excitation are visible as aurora at UV and infrared wavelengths (sometimes also at X-ray wavelengths). A fraction of the electrons is reflected back along the field lines, and produces DAM emissions.     

Micro—structural analysis of YBa2Cu3O7—x thin films grown on different substrates by X—ray techniques

YBa2Cu3Ox(YBCO) thin films grown on different substrates with and/or without Eu2CuO4(ECO) buffer layer were investigated by X-ray wide angle diffraction,reflection,diffuse scattering and topography.Theresults show that for the yttria stabilized ZrO2(YSZ) substrate,the presence of an ECO buffer layer improves the crystalline quality of the YBCO film,while a negative effect is observed for the SrTiO3(STO) substrate.The lateral correlation length for a sample grown on a YSZ substrate with ECO buffer Layer is much greater than grown on an STO subetrate.The STO substrate used has mosaic structure.2001 Elsevier Science B.V.All rights reserved.     

National school on Neutron and X‐ray scattering alumni presentations

The 4th joint Stanford–Berkeley summer school on synchrotron radiation and its applications in physical science was held June 12–17, 2005, at the Stanford Linear Accelerator Center (SLAC). The Stanford–Berkeley summer school is jointly organized by Stanford University, University of California Berkeley, Lawrence Berkeley National Laboratory (LBNL), and the Stanford Synchrotron Radiation Laboratory (SSRL). Since 2001, Anders Nilsson (Stanford/SSRL) and Dave Attwood (UC Berkeley) have been the organizers of this annual weeklong summer school, which alternates each year between Stanford and Berkeley. The summer school provides lecture programs on synchrotron radiation and its broad range of scientific applications in the physical science as well as visits to the Stanford Synchrotron Radiation Laboratory and the Advanced Light Source (ALS), where the students also have the opportunity to experience a beam line.     

Superconductivity and magnetism in Y1−x Ca x Sr2GaCu2O7−δ

Samples of Y_1–x Ca _x Sr₂GaCu₂O_7– (x=0, 0.4) doped with⁵⁷Fe, prepared under various oxygen pressures, have been studied by magnetometry and Mössbauer spectroscopy. Most of the iron ions (Fe³⁺) enter the Ga(Cu(1)) site. For thex=0 sample, the Mössbauer spectra of the iron nuclei in the Cu(2) sublattice display magnetic order of Cu,T _N=370 K. The iron ions in the Ga site display magnetic order only at low temperatures. At temperatures above 90 K, these iron ions display a pure quadrupole doublet Mössbauer spectrum. The samplex=0.4 also displays magnetic order of the Cu(2) site,T _N370 K. A sharp drop in the hyperfine field is observed atT _N, probably associated with a first-order phase transition or two-dimensional ordering. The iron nuclei in the Ga site display paramagnetic long spin relaxation time phenomena at 4.2 K. Thex=0.4 sample prepared under 110 atm oxygen pressure, displays superconductivity,T _c50 K. The Mössbauer spectra give evidence of the presence of two phases. One displays magnetic order, the other is paramagnetic, the last is probably associated with the superconducting phase.