A high beam energy photoelectron-photofragment coincidence spectrometer for complex anions

2018 ◽  
Vol 89 (12) ◽  
pp. 123304 ◽  
Author(s):  
J. A. Gibbard ◽  
A. J. Shin ◽  
E. Castracane ◽  
R. E. Continetti
Keyword(s):  
Beam Energy ◽  
High Beam ◽  
Coincidence Spectrometer ◽  
Complex Anions ◽  
High Beam Energy

scholarly journals Toward a plasma-based accelerator at high beam energy with high beam charge and high beam quality

2020 ◽  
Vol 23 (3) ◽  
Author(s):  
P. A. P. Nghiem ◽  
R. Assmann ◽  
A. Beck ◽  
A. Chancé ◽  
E. Chiadroni ◽  
...  
Keyword(s):  
Beam Energy ◽  
Beam Quality ◽  
High Beam ◽  
High Beam Energy ◽  
High Beam Quality

scholarly journals Channeling and radiation experiments at SLAC

2019 ◽  
Vol 34 (34) ◽  
pp. 1943006
Author(s):  
U. Wienands ◽  
S. Gessner ◽  
M. J. Hogan ◽  
T. Markiewicz ◽  
T. Smith ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Beam Energy ◽  
Narrow Band ◽  
Test Facility ◽  
Test Beam ◽  
High Beam ◽  
Silicon Crystals ◽  
Volume Reflection ◽  
Series Of Experiments ◽  
First Time

Since 2014, a SLAC-Aarhus-Ferrara-CalPoly collaboration augmented by members of ANL and MIT has performed electron and positron channeling experiments using bent silicon crystals at the SLAC End Station A Test Beam as well as the FACET accelerator test facility. These experiments have revealed a remarkable channeling efficiency of about 24% under our conditions. Volume reflection is even more efficient with almost the whole beam taking part in the reflection process. A positron experiment demonstrated quasi-channeling oscillations for the first time at high beam energy. In our most recent experiment we measured the spectrum of gamma radiation for crystal orientations covering channeling and volume reflection. This series of experiments supports the development of more advanced crystalline devices capable e.g. of producing narrow-band gamma rays with electron beams or studying the interaction of the electrons with the wakefields generated in the crystal at high beam intensity.

Ultra-high resolution column for the scanning electron microscope

1994 ◽  
Vol 52 ◽  
pp. 486-487
Author(s):  
V. Drexel ◽  
E. Weimer ◽  
J.-P. Martin
Keyword(s):  
High Resolution ◽  
Beam Energy ◽  
High Performance ◽  
Ideal Point ◽  
Image Resolution ◽  
Operating Conditions ◽  
Electron Optics ◽  
High Beam ◽  
Working Distance ◽  
Novel Design

1.IntroductionThe demands made on the design of a high-performance SEM column are multiple and contradictory. It should provide outstanding image resolution at all beam energies with samples of all sizes and at any (reasonable) tilt angle. It should also allow excellent signal detection under all operating conditions and a high x ray take-off angle at a working distance suitable for high-resolution microscopy. A novel design concept for the electron optics of the SEM has been implemented in a new high-performance instrument (named DSM 982 GEMINI) in order to meet these goals.2.Advanced electron-optical columnA Schottky field emission source is used in the new SEM. This gun type exhibits the ideal point-source properties for a high-performance instrument. Optimum conservation throughout the column of the very high beam brightness (107 A/cm2.sr.kV) and the very low beam energy spread (0.4 eV) supplied by the gun is achieved by the implementation of a new electron optical principle: a high beam energy is maintained throughout the column (regardless of of the electron probe energy selected by the operator) and any beam cross-over is avoided (Fig. 1).

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.

LVSEM: Past Present and Future

1990 ◽  
Vol 48 (1) ◽  
pp. 364-365
Author(s):  
James B. Pawley
Keyword(s):  
Field Emission ◽  
Line Width ◽  
Time Scales ◽  
Silicon Oxide ◽  
Beam Current ◽  
High Brightness ◽  
High Beam ◽  
Fixed Charges ◽  
Beam Voltage ◽  
Deposited Metal

Past: In 1960 Thornley published the first description of SEM studies carried out at low beam voltage (LVSEM, 1-5 kV). The aim was to reduce charging on insulators but increased contrast and difficulties with low beam current and frozen biological specimens were also noted. These disadvantages prevented widespread use of LVSEM except by a few enthusiasts such as Boyde. An exception was its use in connection with studies in which biological specimens were dissected in the SEM as this process destroyed the conducting films and produced charging unless LVSEM was used.In the 1980’s field emission (FE) SEM’s came into more common use. The high brightness and smaller energy spread characteristic of the FE-SEM’s greatly reduced the practical resolution penalty associated with LVSEM and the number of investigators taking advantage of the technique rapidly expanded; led by those studying semiconductors. In semiconductor research, the SEM is used to measure the line-width of the deposited metal conductors and of the features of the photo-resist used to form them. In addition, the SEM is used to measure the surface potentials of operating circuits with sub-micrometer resolution and on pico-second time scales. Because high beam voltages destroy semiconductors by injecting fixed charges into silicon oxide insulators, these studies must be performed using LVSEM where the beam does not penetrate so far.

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.

Surface recombination effects on minority carrier diffusion length measurements using electron beam-induced current

1990 ◽  
Vol 48 (4) ◽  
pp. 744-745
Author(s):  
D.P. Malta ◽  
M.L. Timmons
Keyword(s):  
Electron Beam ◽  
Beam Energy ◽  
Minority Carrier ◽  
Diffusion Length ◽  
Effective Diffusion ◽  
Surface Recombination ◽  
Surface Recombination Velocity ◽  
Logarithmic Scale ◽  
Minority Carrier Diffusion Length ◽  
Carrier Diffusion

Measurement of the minority carrier diffusion length (L) can be performed by measurement of the rate of decay of excess minority carriers with the distance (x) of an electron beam excitation source from a p-n junction or Schottky barrier junction perpendicular to the surface in an SEM. In an ideal case, the decay is exponential according to the equation, I = Ioexp(−x/L), where I is the current measured at x and Io is the maximum current measured at x=0. L can be obtained from the slope of the straight line when plotted on a semi-logarithmic scale. In reality, carriers recombine not only in the bulk but at the surface as well. The result is a non-exponential decay or a sublinear semi-logarithmic plot. The effective diffusion length (Leff) measured is shorter than the actual value. Some improvement in accuracy can be obtained by increasing the beam-energy, thereby increasing the penetration depth and reducing the percentage of carriers reaching the surface. For materials known to have a high surface recombination velocity s (cm/sec) such as GaAs and its alloys, increasing the beam energy is insufficient. Furthermore, one may find an upper limit on beam energy as the diameter of the signal generation volume approaches the device dimensions.

Double beta coincidence spectrometer

Physica ◽  
1952 ◽  
Vol 18 (2) ◽  
pp. 1139-1141
Author(s):  
C MALLMANN
Keyword(s):  
Coincidence Spectrometer
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