Measurement of thermionic electron emission values for pointed LaB 6 single-crystal emitter cathodes has shown that 〈110〉 axial orientations yield emission values ten times higher than 〈100〉 orientations at 1545°K. Minimum values were obtained for the 〈510〉 directions. These findings seem encouraging in achieving perhaps two orders of magnitude higher emission fluxes as compared to tungsten emitters.

A description is given of the design and testing of a directly heated, stable, electron source utilizing a single-crystal lanthanum hexaboride (LaB//6) cathode. The emitter mounting fixture consists of an adjustable molybdenum base unit supported on gas-impervious alumina or machinable glass. Single-crystal cathode rods are securely clamped and positioned between vitreous carbon jaws that are resistively heated. The complete assembly is designed to be a direct ″plug-in″ substitute for the conventional tungsten thermionic filaments used in electron-beam instruments. The cathode current density for LT AN BR 110 greater than axial orientations is found to be ten times higher than that for LT AN BR 100 greater than orientations under equivalent conditions, a value of 50 A cm** minus **2 being measured at 1500 degree C with an observed lifetime in excess of 300 h. Optimum vacuum conditions for high lifetime and stable operation are in the range 1 multiplied by 10** minus **6 Torr and lower. Comparison values for the emission at various temperatures from other borides, and tungsten, are also given.

Small-angle neutron experiments show that near the transition from superconductor to ferromagnet in ErRh4B4 scattering peaks occur at a wave vector |q's|=0.06 -1. The temperature and wave-vector dependence suggest this signal is due to oscillatory magnetization fluctuations caused by the electromagnetic coupling of magnetic and superconducting order parameters. The ferromagnetic Bragg scattering shows a 5% hysteresis and transition-temperature-smearing effects which are also due to magnetic-superconducting interactions. © 1980 The American Physical Society.

During the last decade, X-ray free-electron lasers (XFELs) have enabled the study of light-matter interaction under extreme conditions. Atoms which are subject to XFEL radiation are charged by a complex interplay of (several subsequent) photoionization events and electronic decay processes within a few femtoseconds. The interaction with molecules is even more intriguing, since intricate nuclear dynamics occur as the molecules start to dissociate during the charge-up process. Here, we demonstrate that by analyzing photoelectron angular emission distributions and kinetic energy release of charge states of ionic molecular fragments, we can obtain a detailed understanding of the charge-up and fragmentation dynamics. Our novel approach allows for gathering such information without the need of complex ab initio modeling. As an example, we provide a detailed view on the processes happening on a femtosecond time scale in oxygen molecules exposed to intense XFEL pulses.