Beam Heating in Election Irradiated Foils

1974 ◽  
Vol 32 ◽  
pp. 562-563
Author(s):  
H. P. Leighly ◽  
D. E. Campbell ◽  
J. J. Laidler
Keyword(s):  
Thermal Conductivity ◽  
Electron Microscope ◽  
Energy Loss ◽  
Ambient Temperature ◽  
Temperature Rise ◽  
Beam Energy ◽  
Beam Intensity ◽  
Beam Radius ◽  
Beam Heating

Fisher developed an expression for the loss of energy in electron microscope foils. This expression utilizes a theory of Bethe's to describe the energy loss for electrons in a solid. Fisher obtained the following relationship: ΔΤαΙ ρ/k in which ΔΤ is the temperature rise above the ambient temperature, ρ° is density of the foil, k is thermal conductivity, and IO is beam intensity. By using this expression with IO = 1020e/cm2 /sec, he calculated the very substantial heating of foils of various metallic and nonmetallic materials as a function of beam radius, distance to the nearest conductor, and beam energy; i. e., iron has a 2000°C temperature rise for a 10-micron beam, 0.1-MeV electrons, and 900-micron distance to the nearest conductor.

Performance of the Gatan PEELS™ on the VG HB501 STEM

1989 ◽  
Vol 47 ◽  
pp. 410-411
Author(s):  
Ondrej L. Krivanek ◽  
James H. Paterson ◽  
Helmut R. Poppa
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Beam Energy ◽  
Detection Efficiency ◽  
Beam Current ◽  
Scanning Transmission Electron Microscope ◽  
Parallel Detection ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Electron Energy Loss

Parallel-detection electron energy-loss spectrometers offer several hundred times the detection efficiency of serial-detection spectrometers, as well as improved energy resolution. These advantages should be especially important when using a scanning transmission electron microscope (STEM) with a cold field emission gun (FEG), in which the available beam current is typically 10 to 100 times less than in a conventional TEM, while the beam energy spread is typically only 0.3 eV. We have therefore investigated the performance of the Gatan parallel-detection spectrometer (Gatan model 666 PEELS™) when mounted on the VG HB501 FEG STEM.

scholarly journals Experimental and numerical investigation of thermal field for a motor and related factors sensitivities using combined CFD-Taguchi method

2019 ◽  
Vol 23 (Suppl. 4) ◽  
pp. 1065-1077
Author(s):  
Xueqi Liang ◽  
Huiqiang Luo ◽  
Min Zeng ◽  
Yining Wu ◽  
Qiuwang Wang
Keyword(s):  
Thermal Conductivity ◽  
Sensitivity Analysis ◽  
Taguchi Method ◽  
Ambient Temperature ◽  
Temperature Rise ◽  
Convection Heat Transfer ◽  
Axial Direction ◽  
Experimental Result ◽  
Related Factors ◽  
Copper Loss

Over-temperature is a fatal problem when a motor is running. In this work, the temperature and temperature rise of the motor are investigated experimentally and numerically. The experiment is conducted by means of both voltmeter-ammeter method and embedding thermal resistors, to obtain the mean temperature and the local temperature of the stator coils, respectively. The numerical calculation is carried out to study the temperature field of the stator and the rotor, which agrees well with the experimental result. What?s more, the sensitivity analysis of eighteen factors to the temperature is investigated using combined CFD-Taguchi method. The main conclusions are drawn. Firstly, according to the numerical results, the maximal temperature and the maximal temperature rise at rated speed are 143? and 99 K, respectively. The values are 145.8? and 90 K, according to the experimental results, which are lower than the temperature allowed, 180? and temperature rise allowed, 125 K. Secondly, the sensitivity analysis results suggest that the key factors influencing the temperature are in sequence the ambient temperature, the copper loss, the thickness of the layers, the outside convection heat transfer coefficient of crate, the iron loss at the tooth and thermal conductivity of the insulation. The contact thermal resistance and the thermal conductivity of the core in axial direction have little influence on the temperature. The rank to the temperature rise is similar except the ambient temperature, which has little effect on the temperature rise.

Inelastic Electron-Matter Interactions

1978 ◽  
Vol 36 (3) ◽  
pp. 259-267
Author(s):  
J. Silcox
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Chemical Structure ◽  
Inelastic Electron ◽  
Primary Concern ◽  
Unique Probe ◽  
Introductory Paper ◽  
Elastic Processes ◽  
Experimental Level ◽  
Inelastic Processes

In this introductory paper, my primary concern will be in identifying and outlining the various types of inelastic processes resulting from the interaction of electrons with matter. Elastic processes are understood reasonably well at the present experimental level and can be regarded as giving information on spatial arrangements. We need not consider them here. Inelastic processes do contain information of considerable value which reflect the electronic and chemical structure of the sample. In combination with the spatial resolution of the electron microscope, a unique probe of materials is finally emerging (Hillier 1943, Watanabe 1955, Castaing and Henri 1962, Crewe 1966, Wittry, Ferrier and Cosslett 1969, Isaacson and Johnson 1975, Egerton, Rossouw and Whelan 1976, Kokubo and Iwatsuki 1976, Colliex, Cosslett, Leapman and Trebbia 1977). We first review some scattering terminology by way of background and to identify some of the more interesting and significant features of energy loss electrons and then go on to discuss examples of studies of the type of phenomena encountered. Finally we will comment on some of the experimental factors encountered.

Data Acquisition and Handling Unit for a Quantitative Use of Electron Energy Loss Spectroscopy

1977 ◽  
Vol 35 ◽  
pp. 232-233 ◽  
Author(s):  
P. Trebbia ◽  
P. Ballongue ◽  
C. Colliex
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Single Channel ◽  
Detection System ◽  
Surface Barrier ◽  
Solid State Detector ◽  
Electrostatic Mirror ◽  
Electron Energy Loss

An effective use of electron energy loss spectroscopy for chemical characterization of selected areas in the electron microscope can only be achieved with the development of quantitative measurements capabilities.The experimental assembly, which is sketched in Fig.l, has therefore been carried out. It comprises four main elements.The analytical transmission electron microscope is a conventional microscope fitted with a Castaing and Henry dispersive unit (magnetic prism and electrostatic mirror). Recent modifications include the improvement of the vacuum in the specimen chamber (below 10-6 torr) and the adaptation of a new electrostatic mirror.The detection system, similar to the one described by Hermann et al (1), is located in a separate chamber below the fluorescent screen which visualizes the energy loss spectrum. Variable apertures select the electrons, which have lost an energy AE within an energy window smaller than 1 eV, in front of a surface barrier solid state detector RTC BPY 52 100 S.Q. The saw tooth signal delivered by a charge sensitive preamplifier (decay time of 5.10-5 S) is amplified, shaped into a gaussian profile through an active filter and counted by a single channel analyser.

Edge Penetration Effects in the Low-Loss Electron Image in the SEM

1988 ◽  
Vol 46 ◽  
pp. 202-203
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Beam Energy ◽  
Secondary Electron ◽  
Sharp Edge ◽  
Beam Diameter ◽  
Low Loss ◽  
Additional Information ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is useful for the study of uncoated photoresist and some other poorly conducting specimens because it is less sensitive to specimen charging than is the secondary electron (SE) image. A second advantage can arise from a significant reduction in the width of the “penetration fringe” close to a sharp edge. Although both of these problems can also be solved by operating with a beam energy of about 1 keV, the LLE image has the advantage that it permits the use of a higher beam energy and therefore (for a given SEM) a smaller beam diameter. It is an additional attraction of the LLE image that it can be obtained simultaneously with the SE image, and this gives additional information in many cases. This paper shows the reduction in penetration effects given by the use of the LLE image.

Observations on the Structure of Ta2O5

1972 ◽  
Vol 30 ◽  
pp. 540-541
Author(s):  
P. S. Kotval ◽  
C. J. Dewit
Keyword(s):  
Electron Microscope ◽  
Structural Features ◽  
Amorphous Structure ◽  
Polished Surface ◽  
Distilled Water ◽  
Anodic Films ◽  
Amorphous Films ◽  
Beam Heating ◽  
Diffraction Patterns ◽  
Hexagonal Arrays

The structure of Ta2O5 has been described in the literature in several different crystallographic forms with varying unit cell lattice parameters. Earlier studies on films of Ta2O5 produced by anodization of tantalum have revealed structural features which are not consistent with the parameters of “bulk” Ta2O5 crystalsFilms of Ta2O5 were prepared by anodizing a well-polished surface of pure tantalum sheet. The anodic films were floated off in distilled water, collected on grids, dried and directly examined in the electron microscope. In all cases the films were found to exhibit diffraction patterns representative of an amorphous structure. Using beam heating in the electron microscope, recrystallization of the amorphous films can be accomplished as shown in Fig. 1. As suggested by earlier work, the recrystallized regions exhibit diffraction patterns which consist of hexagonal arrays of main spots together with subsidiary rows of super lattice spots which develop as recrystallization progresses (Figs. 2a and b).

Crystallographic Characterization of Dislocation Loops in Irradiated Tungsten

1968 ◽  
Vol 26 ◽  
pp. 290-291
Author(s):  
Robert C. Rau
Keyword(s):  
Electron Microscope ◽  
Ambient Temperature ◽  
Dislocation Loops ◽  
Polycrystalline Specimen ◽  
Post Irradiation ◽  
Neutron Fluences

Previous work has shown that post-irradiation annealing, at temperatures near 1100°C, produces resolvable dislocation loops in tungsten irradiated to fast (E > 1 MeV) neutron fluences of about 4 x 1019 n/cm2 or greater. To crystallographically characterize these loops, tilting experiments were carried out in the electron microscope on a polycrystalline specimen which had been irradiated to 1.5 × 1021 n/cm2 at reactor ambient temperature (∼ 70°C), and subseouently annealed for 315 hours at 1100°C. This treatment produced large loops averaging 1000 Å in diameter, as shown in the micrographs of Fig. 1. The orientation of this grain was near (001), and tilting was carried out about axes near [100], [10] and [110].

Electron beam induced current study of thin silicon layers on insulator substrate

1990 ◽  
Vol 48 (4) ◽  
pp. 618-619
Author(s):  
A. Buczkowski ◽  
Z. J. Radzimski ◽  
J. C. Russ ◽  
G. A. Rozgonyi
Keyword(s):  
Electron Beam ◽  
Energy Loss ◽  
Beam Energy ◽  
Collection Efficiency ◽  
Silicon Layer ◽  
Depletion Layer ◽  
Incident Electron Energy ◽  
Induced Current ◽  
Electron Hole ◽  
Electron Beam Induced Current

If a thickness of a semiconductor is smaller than the penetration depth of the electron beam, e.g. in silicon on insulator (SOI) structures, only a small portion of incident electrons energy , which is lost in a superficial silicon layer separated by the oxide from the substrate, contributes to the electron beam induced current (EBIC). Because the energy loss distribution of primary beam is not uniform and varies with beam energy, it is not straightforward to predict the optimum conditions for using this technique. Moreover, the energy losses in an ohmic or Schottky contact complicate this prediction. None of the existing theories, which are based on an assumption of a point-like region of electron beam generation, can be used satisfactorily on SOI structures. We have used a Monte Carlo technique which provide a simulation of the electron beam interactions with thin multilayer structures. The EBIC current was calculated using a simple one dimensional geometry, i.e. depletion layer separating electron- hole pairs spreads out to infinity in x- and y-direction. A point-type generation function with location being an actual location of an incident electron energy loss event has been assumed. A collection efficiency of electron-hole pairs was assumed to be 100% for carriers generated within the depletion layer, and inversely proportional to the exponential function of depth with the effective diffusion length as a parameter outside this layer. A series of simulations were performed for various thicknesses of superficial silicon layer. The geometries used for simulations were chosen to match the "real" samples used in the experimental part of this work. The theoretical data presented in Fig. 1 show how significandy the gain decreases with a decrease in superficial layer thickness in comparison with bulk material. Moreover, there is an optimum beam energy at which the gain reaches its maximum value for particular silicon thickness.

Some Aspects of Exelfs Analysis in the Electron Microscope

1980 ◽  
Vol 38 ◽  
pp. 118-119
Author(s):  
D. E. Johnson ◽  
S. Csillag
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Energy Loss ◽  
Analytical Electron Microscopy ◽  
Interference Effects ◽  
Interatomic Distances ◽  
X Ray ◽  
Structure Information ◽  
Microanalytical Technique ◽  
Analytical Electron

Recently, the applications area of analytical electron microscopy has been extended to include the study of Extended Energy Loss Fine Structure (EXELFS). Modulations past an ionization edge in the energy loss spectrum (EXELFS), contain atomic fine structure information similar to Extended X-ray Absorbtion Fine Structure (EXAFS). At low momentum transfer the main contribution to these modulations comes from interference effects between the outgoing excited inner shell electron waves and electron waves backscattered from the surrounding atoms. The ability to obtain atomic fine structure information (such as interatomic distances) combined with the spatial resolution of an electron microscope is unique and makes EXELFS an important microanalytical technique.

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