Recent results of PADReS, the Photon Analysis Delivery and REduction System, from the FERMI FEL commissioning and user operations

The Photon Analysis Delivery and REduction System of FERMI (PADReS) has been routinely used during the machine commissioning and operations of FERMI since 2011. It has also served the needs of several user runs at the facility from late 2012. The system is endowed with online and shot-to-shot diagnostics giving information about intensity, spatial-angular distribution, spectral content, as well as other diagnostics to determine coherence, pulse lengthetc. Moreover, PADReS is capable of manipulating the beam in terms of intensity and optical parameters. Regarding the optics, besides a standard refocusing system based on an ellipsoidal mirror, the Kirkpatrick–Baez active optics systems are key elements and have been used intensively to meet users' requirements. A general description of the system is given, together with some selected results from the commissioning/operations/user beam time.

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Friedrich Richard Ulbricht’s Kugelphotometer

Sandbows and Black Lights ◽

10.1093/oso/9780197518571.003.0006 ◽

2021 ◽

pp. 27-30

Author(s):

Stephen R. Wilk

Keyword(s):

Angular Distribution ◽

19Th Century ◽

Rapid Development ◽

Electric Arc ◽

Simple Solution ◽

Spectral Content ◽

Meaningful Comparison ◽

Uniform Region ◽

The 19Th Century ◽

Incandescent Lamps

With the rapid development of many new and varied sources of light in the 19th century—Argand lamps of different designs and which burned various fuels, Carcel lamps, stearin candles, paraffin candles, and spermaceti candles, electric arc lamps, Drummond lamps, incandescent lamps with various filaments, Nernst glowbars, and many others —some method was needed to compare their output. But with the sources varying in spectral content and the angular distribution of the light, how could a meaningful comparison be made? After various fruitless attempts were made to concentrate the light onto a uniform region a surprisingly simple solution was proposed.

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Importance of Internal Ion Beam Parameters on the Self-organized Pattern Formation with Low-energy Broad Beam Ion Sources

MRS Proceedings ◽

10.1557/proc-1181-dd13-13 ◽

2009 ◽

Vol 1181 ◽

Author(s):

Marina I Cornejo ◽

Bashkim Ziberi ◽

Michael Tartz ◽

Horst Neumann ◽

Frank Frost ◽

...

Keyword(s):

Angular Distribution ◽

Surface Topography ◽

Incidence Angle ◽

Ion Beam ◽

Plasma Sheath ◽

Low Energy ◽

Optical Parameters ◽

Broad Beam ◽

Beam Parameters ◽

Total Voltage

AbstractThe low energy ion beam erosion of solid surfaces is a simple bottom-up approach for the generation of nanostructures. For certain sputtering conditions caused by self-organization processes well ordered nanostructures on the surface like one-dimensional ripples or regular arrays of dots can be formed [1]. Using broad beam sources, the low energy ion beam erosion can be a cost-efficient method to produce large-area nanostructured surfaces in a one-step process.The processes involved have been studied in the last decades and the pattern formation is attributed to the competition of curvature dependant sputtering and various relaxation mechanisms. It is also well known that the ion beam incidence angle (the angle between the sample surface normal and the axis of the beam source) is one critical parameter that determines the surface topography. However, inherent to all broad beam sources, the ion beam exhibits a certain divergence, i.e. the ion trajectories are not parallel to each other. This generates a spread of the local incidence angle with respect to the geometrically defined beam incidence angle.Recent studies showed that the divergence angle and angular distribution of the ions, here called internal beam parameters, also affect the surface topography [2].The angular distribution can be controlled by the total voltage applied on the geometrical defined ion optical system of the broad beam ion source. For the given multi-aperture two-grid ion optical system the total voltage is the sum of the voltages applied to the first (screen) and second (accelerator) grid. This total voltage, together with the geometrical characteristics of the used grid systems, including the shape of the plasma sheath boundary at the screen grid, define the overall ion-optical parameters of the source, i. e. the divergence angle and angular distribution of the ions within the beam.In this contribution a first approach of the effect of the internal beam parameters on the surface topography is presented. It was analyzed the effect on the topography on Si surfaces of some experimental parameters that affect the internal beam parameters by changing the ion-optical parameters and the shape of the plasma sheath boundary. Explicitly, the influence of the discharge voltage, the operation time and the distance between the screen and accelerator grid is shown.[1] B. Ziberi, M. Cornejo, F. Frost, B. Rauschenbach, J. Phys.: Condens. Matter (submitted).[2] B. Ziberi, F. Frost, M. Tartz, H. Neumann, B. Rauschenbach, Appl. Phys. Lett. 92, 063102 (2008)

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Correlation analysis of radiation damage

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108210 ◽

1978 ◽

Vol 36 (1) ◽

pp. 214-215

Author(s):

R. Hegerl ◽

A. Feltynowski ◽

B. Grill

Keyword(s):

Electron Microscopy ◽

Independent Random Variables ◽

Optical Parameters ◽

Bright Field Image ◽

Bright Field ◽

Expectation Value ◽

All Optical ◽

Image Element ◽

Stochastic Series ◽

The Common

Till now correlation functions have been used in electron microscopy for two purposes: a) to find the common origin of two micrographs representing the same object, b) to check the optical parameters e. g. the focus. There is a third possibility of application, if all optical parameters are constant during a series of exposures. In this case all differences between the micrographs can only be caused by different noise distributions and by modifications of the object induced by radiation.Because of the electron noise, a discrete bright field image can be considered as a stochastic series Pm,where i denotes the number of the image and m (m = 1,.., M) the image element. Assuming a stable object, the expectation value of Pm would be Ηm for all images. The electron noise can be introduced by addition of stationary, mutual independent random variables nm with zero expectation and the variance. It is possible to treat the modifications of the object as a noise, too.

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Electron Scattering in Solids

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133618 ◽

1990 ◽

Vol 48 (2) ◽

pp. 4-5

Author(s):

Ryuichi Shimizu ◽

Ze-Jun Ding

Keyword(s):

Monte Carlo Simulation ◽

Monte Carlo ◽

Angular Distribution ◽

Elastic Scattering ◽

Electron Scattering ◽

Cross Sections ◽

Expansion Method ◽

Electron Excitation ◽

Partial Wave Expansion ◽

Backscattered Electrons

Monte Carlo simulation has been becoming most powerful tool to describe the electron scattering in solids, leading to more comprehensive understanding of the complicated mechanism of generation of various types of signals for microbeam analysis.The present paper proposes a practical model for the Monte Carlo simulation of scattering processes of a penetrating electron and the generation of the slow secondaries in solids. The model is based on the combined use of Gryzinski’s inner-shell electron excitation function and the dielectric function for taking into account the valence electron contribution in inelastic scattering processes, while the cross-sections derived by partial wave expansion method are used for describing elastic scattering processes. An improvement of the use of this elastic scattering cross-section can be seen in the success to describe the anisotropy of angular distribution of elastically backscattered electrons from Au in low energy region, shown in Fig.l. Fig.l(a) shows the elastic cross-sections of 600 eV electron for single Au-atom, clearly indicating that the angular distribution is no more smooth as expected from Rutherford scattering formula, but has the socalled lobes appearing at the large scattering angle.

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Experimental study on the restoration from a tilt-azimuth series for improvement in resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013955x ◽

1995 ◽

Vol 53 ◽

pp. 636-637

Author(s):

Norio Baba ◽

Norihiko Ichise ◽

Syunya Watanabe

Keyword(s):

Experimental Study ◽

Spherical Aberration ◽

Incident Beam ◽

Optical Parameters ◽

Beam Tilting ◽

Illumination Method ◽

Restoration Method ◽

Illumination Mode

The tilted beam illumination method is used to improve the resolution comparing with the axial illumination mode. Using this advantage, a restoration method of several tilted beam images covering the full azimuthal range was proposed by Saxton, and experimentally examined. To make this technique more reliable it seems that some practical problems still remain. In this report the restoration was attempted and the problems were considered. In our study, four problems were pointed out for the experiment of the restoration. (1) Accurate beam tilt adjustment to fit the incident beam to the coma-free axis for the symmetrical beam tilting over the full azimuthal range. (2) Accurate measurements of the optical parameters which are necessary to design the restoration filter. Even if the spherical aberration coefficient Cs is known with accuracy and the axial astigmatism is sufficiently compensated, at least the defocus value must be measured. (3) Accurate alignment of the tilt-azimuth series images.

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Computer-Assisted High-Re Solution TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179567 ◽

1990 ◽

Vol 48 (1) ◽

pp. 162-163

Author(s):

F.A. Ponce ◽

H. Hikashi

Keyword(s):

Signal To Noise Ratio ◽

Accurate Determination ◽

Computer Software ◽

Video Camera ◽

Image Contrast ◽

Objective Lens ◽

Computer Assisted ◽

Optical Parameters ◽

Astigmatism Correction

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.

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Hearing in Mice by GSR Audiometry: II. Magnitude of Unconditioned GSR as a Function of Intensity and Frequency Interactions

Journal of Speech and Hearing Research ◽

10.1044/jshr.1101.169 ◽

1968 ◽

Vol 11 (1) ◽

pp. 169-178 ◽

Cited By ~ 4

Author(s):

Alan Gill ◽

Charles I. Berlin

Keyword(s):

Power Law ◽

Response Magnitude ◽

Single Units ◽

Spectral Content ◽

Hearing Sensitivity ◽

Subjective Magnitude ◽

Orderly Fashion ◽

Viiith Nerve

The unconditioned GSR’s elicited by tones of 60, 70, 80, and 90 dB SPL were largest in the mouse in the ranges around 10,000 Hz. The growth of response magnitude with intensity followed a power law (10 .17 to 10 .22 , depending upon frequency) and suggested that the unconditioned GSR magnitude assessed overall subjective magnitude of tones to the mouse in an orderly fashion. It is suggested that hearing sensitivity as assessed by these means may be closely related to the spectral content of the mouse’s vocalization as well as to the number of critically sensitive single units in the mouse’s VIIIth nerve.

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