New developments in ESCA-instrumentation

The different components of an ESCA-system are analyzed theoretically and conditions of optimum performance are used as basis for the design of differe     

New developments in nonrelativistic gravity

In this presentation we give a short overview of Newton–Cartan geometry and gravity and some recent results about its matter couplings.     

Investigation of optimum condition in oxygen gas-assisted laser cutting

Laser cutting characteristics including power level and cutting gas pressure are investigated in order to obtain an optimum kerf width. The kerf width is investigated for a laser power range of 50–170 W and a gas pressure of 1–6 bar for steel and mild steel materials. Variation of sample thickness, material type, gas pressure and laser power on the average cut width and slot quality are investigated. Optimum conditions for the steel and mild steel materials with a thickness range of 1–2 mm are obtained. The optimum condition for the steel cutting results in a minimum average kerf width of 0.2 mm at a laser power of 67 W, cutting rate of 7.1 mm/s and an oxygen pressure of 4 bar. A similar investigation for the mild steel cutting results in a minimum average kerf width of 0.3 mm at the same laser power of 67 W, cutting rate of 9.5 mm/s, and an oxygen pressure of 1 bar. The experimental average kerf is about 0.3 mm, which is approximately equal to the estimated focused beam diameter of 0.27 mm for our focusing lens (f=4 cm and 100 W power). This beam size leads to a laser intensity of about 1.74×10⁹ W/m² at the workpiece surface. The estimated cutting rate from theoretical calculation is about 8.07 mm/s (1.0 mm thickness and 100 W power), which agrees with the experimental results that is 7.1 mm/s for 1.0 mm thickness of mild steel at the laser power of 88 W.     

New developments in polarized ion sources

A new atomic beam type polarized alkali ion source has been installed at the MP tandem accelerator in Heidelberg. By thermal evaporation and collimation Li and Na atomic beams are formed. Polarization is produced by optical pumping and a 4-pole Stern-Gerlach magnet which results in beams in a single Zeeman m-state. The population is shifted to any m-state by an adiabatic high frequency transition in a medium field (MFT). The purity of m-state population has been measured to be between 0.95 and 0.98, which results in nuclear polarization P > 0.9, s=z,zz. At the surface ionizer of the ion source beams of 15 to 65 A of positive ions have been extracted of optically pumped Li and Na ions, respectively.     

New developments and trends in NMR-ON

New developments and new trends in NMR-ON are presented, especially in the context of precise measurements of nuclear magnetic moments and electric quadrupole moments of short-lived nuclei far off stability with on-line nuclear orientation techniques. The main emphasis is put on the following items:

1. Quadrupole-interaction-resolved NMR-ON (QI-NMR-ON): It is shown that hcp-Co is an ideal matrix for precise measurements of electric quadrupole moments of radioactive nuclei in the region Hg, Au, Pt, Ir, Os. Recently, the first on-line experiment was performed successfully at NICOLE/ISOLDE-CERN and the very interesting quadrupole moment of¹⁸⁶Au could be determined precisely.
2. General problems with lattice location and NMR-ON line widths in long decay chains, such as “lattice-site conservation” by implantation of a suitable precursor.
3. β-decay-induced lattice site change. In the context of integral nuclear orientation measurements on nuclei far off stability, where the β-decay energies become large, lattice site changes may occur, which make the interpretation of γ-anisotropies measured by integral and even time-differential techniques difficult or even impossible. A pilot experiment is described, in which such a β-decay-induced lattice site change has been identified by a double-resonance NMR-ON measurement.

     

New developments in X-ray storage phosphors

We found a significant PSL effect in Eu²⁺-doped fluorozirconate glasses (ZBLAN) which were additionally doped with Br⁻ or Cl⁻ ions. The PSL is attributed to the characteristic emission of Eu²⁺ present in nano-crystallites of BaBr₂ or BaCl₂, which form in the glass upon annealing. The metastable hexagonal form of BaX₂ (X=Br,Cl) is always formed first before it is converted into the stable orthorhombic form. The particle size increases upon annealing and so does the PSL efficiency of the glass ceramic. However, there is a saturation of the PSL efficiency, which is for Br⁻ doping about 9% and for Cl⁻-doping about 80% of the Eu-doped BaFBr standard. The particle size was determined by transmission electron microscopy (TEM). The TEM results show a clear tendency for bigger particles for longer annealing at the expense of its number. The particle size for the most efficient phosphor is about 100 nm.     

New developments in phase doppler anemometry

This article reviews a number of recent PDA developments designed to either improve accuracy or extend the technique in measurement range or measurand. Many of these developments have depended on improvements in the computation of light scattering from small particles and initially several of these improvements will be discussed. The sensitivity of the dual-mode PDA to particle sphericity will be discussed, followed by possibilities for the sizing of oscillating particles/droplets. Finally, some remarks will be directed to the dual-burst technique and its use in novel optical systems.     

New developments in PAC and PAD

Recent developments in both methods, Perturbed Angular Correlation (PAC) and Perturbed Angular Distribution (PAD) concern improvements in the instrumentation for various applications and sophistications in detail rather than methodology. These will be illustrated by examples from PAC and PAD studies which investigate local structural properties of semiconductors and metallic surfaces, and local magnetic contributions in ferromagnetic metals, nonmagnetic materials, and high-temperature superconductors and related oxides.     

New developments in transient field measurements

New data for electron polarization were obtained in transient field (TF) measurements for H-like ions at high velocities. Spin-exchange scattering calculations with the polarized electrons in bound states of the ferromagnetic host atoms are successful for explaining experimental data. The deteriorating effect of ion-beam-induced perturbations on the TF strength in ferromagnetic materials has been studied systematically. Concepts for its control or elimination are introduced and discussed.     

New phenomena in laser-assisted scattering of an electron by a muon

The scattering of an electron by a muon in the presence of a linearly polarized laser field is investigated in the first Born approximation. The theoretical results reveal the following: i) At medium and large scattering angles, many multiphoton processes occur during scattering, and these nonlinear phenomena may predict the resonant state of the electron and the muon formed in the collision process. ii) The photoabsorption (inverse bremsstrahlung) dominates the photoemission (bremsstrahlung), causing the cross section to increase. iii) When the laser polarization deviates from the incident direction, the lasermodified total cross section depends considerably on the azimuthal angle of the scattered electron. The dependence of the cross section on the field strength, polarization direction, and electron-impact energy are studied.     

New methodical developments for GRANIT

New methodical developments for the GRANIT spectrometer address further improvements of the critical parameters of this experimental installation, as well as its applications to new fields of research. Keeping in mind an extremely small fraction of ultra cold neutrons (UCN) that could be bound in gravitational quantum states, we look for methods to increase statistics due to: developing UCN sources with maximum phase-space density, counting simultaneously a large fraction of neutrons using position-sensitive detectors, and decreasing detector backgrounds. Also we explore an eventual application of the GRANIT spectrometer beyond the scope of its initial goals, for instance, for reflectometry with UCN.     

New developments in solid phase synthesis supports

Developments in solid phase synthesis supports for the end of 1996 and much of 1997 are reviewed. Issues regarding support induced impurities and enhancing solid phase reaction rates are also discussed.     

New developments in processing cathodic arc plasmas

Filtering of plasmas by curved solenoidal ducts is well established as a method of removing macroparticles. By analyzing the interactions of planar probes with the drifting plasma of the cathodic arc, new insights have been obtained into the operation of these ducts. Theoretical modeling of these interactions suggests, and experiment confirms, that the use of a separate biased electrode on the inside of the duct gives enhanced transmission without drawing excessive electron current. Theoretical modeling of a negatively biased planar electrode lying parallel to the drift velocity as well as experiment both show that ions are captured effectively onto the electrode producing a macroparticle free film at good deposition rates. The application of pulsed high voltage to the substrate placed at the exit of the duct is treated theoretically, and a model is proposed which gives a good agreement with the experimental concentration profile for a silicon surface coated and simultaneously implanted with titanium     

New developments in technologically important magnetic materials

In the past decade there has been a number of new developments in magnetic materials that should pave the way for expanded applications. These include: highly oriented high induction silicon steel; new varieties of permalloys, especially near 65% Ni; amorphous soft magnetic materials of the type (Fe, Co, Ni)₈₀ (P, B, Al)₂₀ produced by continuous rapid quenching; rare earth-cobalt permanent magnets with _iH_c to 150 kA/m and (BH)_max to 200 kJ/m³; ductile chromium cobalt iron permanent magnets with properties comparable to the alnicos; new families of ductile semihard magnets particularly for miniature self-latching dry reed contacts; and a new memory technology based on magnetic bubbles. These new developments will be discussed along with prospects for future applications.     

国际医学物理学的新发展

文章评述了国际医学物理学近印年的新发展，着重介绍了数字影像物理学和放射治疗物理学的新进展及其对临床应用高新医疗器械的重要作用，并谈及国际医学物理学的新发展对中国医学物理学发展的启示．     

医学超声体成像新进展

本文叙述了近年来医学超声体成像技术的信号采集,三维重建与显示等方面的新进展,探讨了应用的前景。