Improving the technology of gold ore X-ray radiometric separation

Introduction. Gold ore pre-concentration is an urgent issue that can efficiently be solved by the technology of X-ray radiometric separation (XRS). Quarts and quarts-sulfide gold ore XRS is based on the methods of indirect sorting by gold accompanying chemical elements or genetic associate minerals laying the foundation for the creation of separation characteristics for these ores. Additional separation characteristics are required for efficient gold-quartz and gold-quartz-sulfide ore sorting; Irgiredmet Research Institute works on these characteristics search and development. Research methodology. Optimal ore separation characteristics for each specific deposit are chosen after studying and analyzing the spectral information acquired at XRF separators when detecting secondary characteristic radiation from each specific deposit ore samples. The recent modernization of XRF separators significantly enhanced the technological capabilities of XRS concerning intensive search and study of new separation characteristics for gold ore. It has been established that most ores can be efficiently sorted by three characteristics. Research results. A new method of gold ore XRS has been developed which consists of simultaneously applying three, two, or one decision criterion of a lump separation depending on the type, geologicalmineralogical properties, and material composition of the processed ore

Angular Distribution of Characteristic Radiation Following the Excitation of He-Like Uranium in Relativistic Collisions

In this paper, we present an experimental and theoretical study of excitation processes for the heaviest stable helium-like ion, that is, He-like uranium occurring in relativistic collisions with hydrogen and argon targets. In particular, we concentrate on angular distributions of the characteristic Kα radiation following the K → L excitation of He-like uranium. We pay special attention to the magnetic sub-level population of the excited 1s2lj states, which is directly related to the angular distribution of the characteristic Kα radiation. We show that the experimental data can be well described by calculations taking into account the excitation by the target nucleus as well as by the target electrons. Moreover, we demonstrate for the first time an important influence of the electron-impact excitation process on the angular distributions of the Kα radiation produced by excitation of He-like uranium in collisions with different targets.

Observation of electron-induced characteristic x-ray and bremsstrahlung radiation from a waveguide cavity

We demonstrate x-ray generation based on direct emission of spontaneous x-rays into waveguide modes. Photons are generated by electron impact onto a structured anode target, which is formed as an x-ray waveguide or waveguide array. Both emission of characteristic radiation and bremsstrahlung are affected by the changes in mode density induced by the waveguide structure. We investigate how the excited modal pattern depends on the positions of the metal atoms and the distance of the focused electron beam with respect to the waveguide exit side. We compare the results to synchrotron-excited fluorescence. We then discuss how x-ray generation in waveguides can be used to increase the brilliance and directional emission of tabletop x-ray sources, with a corresponding increase in the spatial coherence. On the basis of the Purcell effect, we lastly show that the gain of emission into waveguide modes is governed by the quality factor of the waveguide.

Перспективы использования рентгеновских трубок с автоэмиссионным катодом и "прострельным" анодом в диапазоне мягкого рентгеновского излучения

The use of field emission cathodes in the design of x-ray tubes requires the placement of a cathode assembly with a small distance from the anode, complicating the output of radiation. Most acute this problem occurs when generating a relatively soft spectrum with wavelengths of 1-10 nm: in this case, the accelerating voltage does not exceed several kilovolts, and the inter-electrode distance composes several hundred micrometers. In this work, we experimentally demonstrated the applicability of beryllium-based submicron films as “shot-through” anodes for generating the Be K line ( = 11.4 nm) and the associated bremsstrahlung spectrum. In particular, the characteristic radiation of a tube with a field emission blade cathode and a Be film anode was recorded within the scheme of a grazing incidence grating spectrometer. The characteristics of beryllium films necessary for the development of X-ray tubes of this type with a higher output power are determined.

Hawking radiation may violate the Penrose cosmic censorship conjecture

We analyze the Hawking evaporation process of Reissner–Nordström black holes. It is shown that the characteristic radiation quanta emitted by the charged black holes may turn near-extremal black-hole spacetimes into horizonless naked singularities. This analysis therefore reveals the intriguing possibility that the semi-classical Hawking evaporation process of black holes may violate the fundamental Penrose cosmic censorship conjecture.

Oliver Heaviside: an accidental time traveller

A little discussed aspect of Heaviside's work in electromagnetics concerned faster-than-light (FTL) charged particles, precursors to the hypothetical tachyon and his discovery that such motion should produce a characteristic radiation signature (now called Cherenkov radiation ). When Heaviside wrote, the time travel implications of FTL were not known (Einstein was still a teenager), and in this paper some speculations are offered on what Heaviside would have thought of FTL time travel, and of the associated (now classic) time travel paradoxes, including the possibility (or not) of sending information into the past. This article is part of the theme issue ‘Celebrating 125 years of Oliver Heaviside's ‘Electromagnetic Theory’’.