Search results for "Cathode ray"
showing 10 items of 96 documents
Radiation emission at channeling of electrons in a strained layer undulator crystal
2013
Abstract Experiments have been performed at the Mainz Microtron MAMI to explore the radiation emission spectra from a crystalline undulator at electron beam energies of 270 and 855 MeV. The epitaxially grown graded composition strained layer Si 1 - x Ge x undulator had 4-period with a period length λ u = 9.9 μ m . Spectra taken at the beam energy of 270 MeV at channeling in the undulating (110) planes exhibit a broad excess yield around the theoretically expected photon energies of 0.069 MeV, as compared with a flat silicon reference crystal. Model calculations on the basis of synchrotron-like radiation emission from finite single arc elements, taking into account also coherence effects, su…
Impulsive coronal heating from large-scale magnetic rearrangements: from IRIS to SDO/AIA
2019
The Interface Region Imaging Spectrograph (IRIS) has observed bright spots at the transition region footpoints associated with heating in the overlying loops, as observed by coronal imagers. Some of these brightenings show significant blueshifts in the Si iv line at 1402.77 A (logT[K] = 4.9). Such blueshifts cannot be reproduced by coronal loop models assuming heating by thermal conduction only, but are consistent with electron beam heating, highlighting for the first time the possible importance of non-thermal electrons in the heating of non-flaring active regions. Here we report on the coronal counterparts of these brightenings observed in the hot channels of the Atmospheric Imaging Assem…
Direct Measurement of Focusing Fields in Active Plasma Lenses
2018
Physical review accelerators and beams 21(12), 122801 (2018). doi:10.1103/PhysRevAccelBeams.21.122801
Transient and stable color centers in pure and Cu-doped LiNbO3
2003
The present work is devoted to investigation of stable and transient color centers that are induced by radiation and temperature in pure and Cu-doped LiNbO 3 single crystals. The transient changes of absorption of the crystals induced by pulsed electron beam (E=0.25 MeV) are studied in 0-5000 ns time range, as well as stable changes of absorption induced by reducing annealing and irradiation with γ-quanta, high energy electrons or fast reactor neutrons.
Pulsed gas injection for X-ray spectroscopy of highly charged ions stored in the magnetic trapping mode of an electron beam ion trap
1998
Abstract Highly charged atoms produced in an electron beam ion trap were stored after the electron beam was turned off by operating the trap in the magnetic trapping mode. Such storage allowed monitoring charge exchange reactions between the stored ions and residual neutral gas present in the trap by X-ray detection. The charge exchange reactions were enhanced by the application of a pulse of neutral gas. The method was exemplified for the case of H-like uranium interacting with neutral neon, where the K-shell X-rays and the series limit for the electron capture of U91+ were observed.
Formation of luminescence centres under excitation with electron beams in PbWO 4 and ZnWO 4 crystals
2005
The leading edge of intrinsic luminescence pulse in PbWO 4 and ZnWO 4 single crystals is studied. The rise of luminescence intensity is observed after excitation with electron beam pulse. The luminescence rise is shown tobe a result of luminescence center formation via electron-hole recombination within spatially correlated pairs. An electron of a geminate electron-hole pair of PbWO 4 crystal self-traps and stimulates self-trapping of a hole at a close distance. In the ZnWO 4 crystal a hole of a geminate electron-hole pair self-traps and stimulates self-trapping of the electron producing a W 5 + center at a short distance. The rise-time of luminescence depends on spatial separation of recom…
Structure of the new mineral sarrabusite, Pb5CuCl4(SeO3)4, solved by manual electron-diffraction tomography.
2012
The new mineral sarrabusite Pb5CuCl4(SeO3)4 has been discovered in the Sardinian mine of Baccu Locci, near Villaputzu. It occurs as small lemon–yellow spherical aggregates of tabular crystals (< 10 µm) of less than 100 µm in diameter. The crystal structure has been solved from and refined against electron diffraction of a microcrystal. Data sets have been measured by both a manual and an automated version of the new electron-diffraction tomography technique combined with the precession of the electron beam. The sarrabusite structure is monoclinic and consists of (010) layers of straight chains formed by alternating edge-sharing CuO4Cl2 and PbO8 polyhedra parallel to the c axis, which sha…
Structure solution with automated electron diffraction tomography data: different instrumental approaches
2011
Summary Over the past few years automated electron diffraction tomography has become an established technique for structure solution of nano-crystalline material. The intentional choice of an arbitrary tilt axis and thus, the use of nonoriented diffraction patterns (off-zone acquisition) together with fine equidistant sampling of the reciprocal space result in high quality intensity data sets. Coupling automated electron diffraction tomography with electron beam precession (Vincent & Midgley, 1994) enables sampling of intensities between the static slices of reciprocal space and therefore enhances the quality of intensity data further; relatively complex structures have been solved using 3D…
<title>Forward diffracted parametric X radiation from a thick Tungsten single crystal at 855 MeV electron energy</title>
2007
Features of forward diffracted Parametric X-Radiation (PXR) were investigated at experiments with the 855 MeV electron beam of the Mainz Microtron MAMI employing a 410 micrometer thick tungsten single crystal. Virtual photons from the electron field are diffracted by the (10-1) plane at a Bragg angle of 3.977 degree. Forward emitted radiation was analyzed at an energy of 40 keV with the (111) lattice planes of a flat silicon single crystal in Bragg geometry. Clear peak structures were observed in an angular scan of the tungsten single crystal. The results were analyzed with a model which describes forward diffracted PXR under real experimental conditions. The experiments show that forward d…
Stable and transient color centers in Gd3Ga5O12 crystals
2004
The work is devoted to investigation of stable color centers (CC) that are created in Gd3Ga5O12 (GGG) crystals under irradiation with γ-quanta (E = 1.25 MeV, D = 105 Gy ) as well as transient CC created in the crystals under irradiation with pulsed electron beam (E = 0.25 MeV, pulse duration 10 ns, fluence 1012 cm-2, time interval of registration 0-500 ns). On the basis of the performed study of optical absorption spectra of the as-grown and irradiated crystals it was established the correlation between a defect subsystem of as-grown crystals and a type of CC induced by radiation in the crystals. The role of Ca2+ dopant ions in the processes of CC formation is examined. Models of the stable…