Design of a High-Flux Backscattering Spectrometer for Ultra-High Resolution Inelastic Neutron Measurements

1994 ◽  
Vol 376 ◽  
Author(s):  
P. M. Gehring ◽  
C. W. Brocker ◽  
D. A. Neumann
Keyword(s):  
Phase Space ◽  
High Resolution ◽  
Dynamic Range ◽  
Cold Neutron ◽  
Pyrolytic Graphite ◽  
Inelastic Neutron ◽  
Radius Of Curvature ◽  
High Flux ◽  
Research Facility ◽  
Flux Increase

ABSTRACTWe discuss the design of a new backscattering spectrometer to be installed at the Cold Neutron Research Facility at the National Institute of Standards and Technology. Si (111) crystals cover both monochromator and analyzer which are spherically bent to a radius of curvature of ~ 2 m to focus the incident and scatterered neutron beams. The bending increases the intrinsic lattice gradient of Si beyond its Darwin limit, resulting in an energy resolution of ~ 0.75 μeV FWHM. The monochromator is Doppler-driven, allowing users access to a dynamic range of ±60 μeV. The elastic Q-range covers 0.15 to 1.8 Å-1. The most novel aspect of this design lies in the incorporation of a phase-space-transform chopper. This device rotates at 4700 rpm while neutrons are Bragg-diffracted from sets of pyrolytic graphite crystals affixed to its periphery. The process enhances the neutron flux at the backscattering energy of 2.08 meV, but at the expense of a larger horizontal divergence. Computer simulations indicate a resultant flux increase of order 3 should be obtained.

Optimum velocity of a phase-space transformer for cold-neutron backscattering spectroscopy

2011 ◽  
Vol 44 (3) ◽  
pp. 467-472 ◽  
Author(s):  
Marcus Hennig ◽  
Bernhard Frick ◽  
Tilo Seydel
Keyword(s):  
Phase Space ◽  
Cold Neutron ◽  
Inelastic Neutron Scattering ◽  
Bragg Reflection ◽  
Analytical Framework ◽  
High Energy ◽  
Inelastic Neutron ◽  
High Energy Resolution ◽  
Rotating Disc ◽  
Incident Wavelength

Cold-neutron backscattering spectrometers are designed for inelastic neutron scattering experiments at a high energy resolution, where 0.5 µeV FWHM can routinely be achieved at the incident wavelength λ ≃ 6.3 Å. The phase-space transformation (PST) technique can be used to enhance the neutron flux at the sample position of such backscattering spectrometers at the expense of an acceptable increase of the beam divergence. Technically, the PST is achieved by a rotating disc carrying mosaic crystals on its circumference. Here a new analytical framework to describe the Bragg reflection of a divergent polychromatic beam from a moving mosaic crystal is discussed. Results obtained using this framework are compared with detailed Monte Carlo numerical simulations. The results presented here provide a deeper understanding of the PST and in particular of the optimum circumferential crystal speed of a PST device.

scholarly journals Optimization of the Guide Design of MIRACLES, the Neutron Time-of-Flight Backscattering Spectrometer at the European Spallation Source

2021 ◽  
Vol 6 (1) ◽  
pp. 3
Author(s):  
Félix J. Villacorta ◽  
Damián Martín Rodríguez ◽  
Mads Bertelsen ◽  
Heloisa N. Bordallo
Keyword(s):  
Pulse Shaping ◽  
Dynamic Range ◽  
Inelastic Neutron Scattering ◽  
Time Of Flight ◽  
Inelastic Neutron ◽  
Neutron Guide ◽  
Cold Neutrons ◽  
Sample Position ◽  
Spallation Source ◽  
Flux Increase

To boost the science case of MIRACLES, the time-of-flight backscattering spectrometer at the European Spallation Source (ESS), an optimized neutron guide system, is proposed. This systematic study resulted in an enhancement in the transport of cold neutrons, compared with the previous conceptual design, with wavelengths ranging from λ = 2 Å to 20 Å along the 162.5-m distance from source to sample. This maintained the undisturbed main focus of the instrument, viz, to carry out quasielastic and inelastic neutron scattering (QENS and INS) experiments on a large dynamic range and for both energy-gain and energy-loss sides. To improve the collection of cold neutrons from the source and direct them to the sample position, the vertical geometry was adjusted to an adapted version of a ballistic elliptical profile. Its horizontal geometry was conceived to: (i) keep the high-resolution performance of the instrument, and (ii) minimize the background originating from fast and thermal neutrons. To comply with the first requirement, a narrow guide section at the pulse shaping chopper position has been implemented. To fulfil the second, a curved guide segment has been chosen to suppress neutrons with wavelengths λ < 2 Å. Subsequent tailoring of the phase space provided an efficient transport of cold neutrons along the beamline to reach a 3 × 3 cm2 sample. Finally, additional calculations were performed to present a potential upgrade, with the exchange of the final segment, to focus on samples of approximately 1 × 1 cm2; the proposal anticipates a flux increase of 70% in this 1 cm2 sample area.

scholarly journals ANTARES: Cold neutron radiography and tomography facility

2015 ◽  
Vol 1 ◽  
Author(s):  
Michael Schulz ◽  
Burkhard Schillinger
Keyword(s):  
High Resolution ◽  
Neutron Beam ◽  
Cold Neutron ◽  
Neutron Radiography ◽  
Pinhole Camera ◽  
Neutron Imaging ◽  
High Flux ◽  
Beam Port ◽  
Cold Neutron Beam

The neutron imaging facility ANTARES, operated by the Technische Universität München, is located at the cold neutron beam port SR-4a. Based on a pinhole camera principle with a variable collimator located close to the beam port, the facility provides the possibility for flexible use in high resolution and high flux imaging.

Slow-scan CCD cameras and low-dose High-Resolution Electron Microscopy: Direct and quantitative

1994 ◽  
Vol 52 ◽  
pp. 412-413
Author(s):  
M. Pan
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Structural Damage ◽  
Low Dose ◽  
Dynamic Range ◽  
High Resolution Electron Microscopy ◽  
Operating Conditions ◽  
Digital Data ◽  
Ccd Cameras ◽  
Resolution Electron

It has been known for many years that materials such as zeolites, polymers, and biological specimens have crystalline structures that are vulnerable to electron beam irradiation. This radiation damage severely restrains the use of high resolution electron microscopy (HREM). As a result, structural characterization of these materials using HREM techniques becomes difficult and challenging. The emergence of slow-scan CCD cameras in recent years has made it possible to record high resolution (∽2Å) structural images with low beam intensity before any apparent structural damage occurs. Among the many ideal properties of slow-scan CCD cameras, the low readout noise and digital recording allow for low-dose HREM to be carried out in an efficient and quantitative way. For example, the image quality (or resolution) can be readily evaluated on-line at the microscope and this information can then be used to optimize the operating conditions, thus ensuring that high quality images are recorded. Since slow-scan CCD cameras output (undistorted) digital data within the large dynamic range (103-104), they are ideal for quantitative electron diffraction and microscopy.

scholarly journals High-resolution VLA low radio frequency observations of the Perseus cluster: radio lobes, mini-halo, and bent-jet radio galaxies

2020 ◽  
Vol 499 (4) ◽  
pp. 5791-5805
Author(s):  
M Gendron-Marsolais ◽  
J Hlavacek-Larrondo ◽  
R J van Weeren ◽  
L Rudnick ◽  
T E Clarke ◽  
...  
Keyword(s):  
High Resolution ◽  
Dynamic Range ◽  
Galaxy Cluster ◽  
High Dynamic Range ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Nearby Galaxy ◽  
Cluster Galaxy ◽  
Ngc 1275 ◽  
Perseus Cluster

ABSTRACT We present the first high-resolution 230–470 MHz map of the Perseus cluster obtained with the Karl G. Jansky Very Large Array. The high dynamic range and resolution achieved have allowed the identification of previously unknown structures in this nearby galaxy cluster. New hints of sub-structures appear in the inner radio lobes of the brightest cluster galaxy NGC 1275. The spurs of radio emission extending into the outer X-ray cavities, inflated by past nuclear outbursts, are seen for the first time at these frequencies, consistent with spectral aging. Beyond NGC 1275, we also analyse complex radio sources harboured in the cluster. Two new distinct, narrowly collimated jets are visible in IC 310, consistent with a highly projected narrow-angle tail radio galaxy infalling into the cluster. We show how this is in agreement with its blazar-like behaviour, implying that blazars and bent-jet radio galaxies are not mutually exclusive. We report the presence of filamentary structures across the entire tail of NGC 1265, including two new pairs of long filaments in the faintest bent extension of the tail. Such filaments have been seen in other cluster radio sources such as relics and radio lobes, indicating that there may be a fundamental connection between all these radio structures. We resolve the very narrow and straight tail of CR 15 without indication of double jets, so that the interpretation of such head–tail sources is yet unclear. Finally, we note that only the brightest western parts of the mini-halo remain, near NGC 1272 and its bent double jets.

Performance of the vacuum ultraviolet high-resolution and high-flux beamline for chemical dynamics studies at the Advanced Light Source

1997 ◽  
Vol 68 (5) ◽  
pp. 1945-1951 ◽  
Author(s):  
P. A. Heimann ◽  
M. Koike ◽  
C. W. Hsu ◽  
D. Blank ◽  
X. M. Yang ◽  
...  
Keyword(s):  
High Resolution ◽  
Light Source ◽  
Vacuum Ultraviolet ◽  
High Flux ◽  
Chemical Dynamics ◽  
Advanced Light Source

scholarly journals Measurement of synchrotron-radiation-excited Kossel patterns

2016 ◽  
Vol 23 (1) ◽  
pp. 214-218 ◽  
Author(s):  
G. Bortel ◽  
G. Faigel ◽  
M. Tegze ◽  
A. Chumakov
Keyword(s):  
High Resolution ◽  
Dynamic Range ◽  
Structural Information ◽  
Photon Counting ◽  
Spot Size ◽  
Low Noise ◽  
X Rays ◽  
Technical Problems ◽  
Pixel Detectors ◽  
Exciting Beam

Kossel line patterns contain information on the crystalline structure, such as the magnitude and the phase of Bragg reflections. For technical reasons, most of these patterns are obtained using electron beam excitation, which leads to surface sensitivity that limits the spatial extent of the structural information. To obtain the atomic structure in bulk volumes, X-rays should be used as the excitation radiation. However, there are technical problems, such as the need for high resolution, low noise, large dynamic range, photon counting, two-dimensional pixel detectors and the small spot size of the exciting beam, which have prevented the widespread use of Kossel pattern analysis. Here, an experimental setup is described, which can be used for the measurement of Kossel patterns in a reasonable time and with high resolution to recover structural information.

Enhancement of Differential Interference Contrast Images of Live Cells Obtained With Digital Cameras

1999 ◽  
Vol 5 (S2) ◽  
pp. 1112-1113
Author(s):  
M.V. Parthasarathy
Keyword(s):  
High Resolution ◽  
Contrast Enhancement ◽  
Dynamic Range ◽  
Ccd Camera ◽  
Video Camera ◽  
Live Cells ◽  
Photographic Emulsion ◽  
Digital Cameras ◽  
Structural Detail ◽  
Ccd Cameras

The usefulness of Differential Contrast Interference (DIC) light microscopy for observing fine details within transparent specimens is well known. However, when viewed by the eye or by recording with photographic emulsion, fine structural detail at the limit of resolution is often not visible because of lack of contrast. To overcome this problem, electronic contrast enhancement capabilities of video cameras have been used to enhance structural details that would otherwise be invisible. The technique, commonly referred to as VE-DIC (Video Enhanced DIC), uses first analog contrast enhancement of the image with a video camera followed by a real-time digital image processor to further enhance the image with. We are exploring the feasibility of achieving fine structural detail of live cells by directly acquiring digital images of them with a high resolution CCD camera.High resolution cooled slow-scan 12-bit CCD cameras are well suited for DIC microscopy because of their greater dynamic range than video CCD cameras that are normally 8-bits or lower.

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