Impact of magnetic fields on dose measurement with small ion chambers illustrated in high‐resolution response maps

It is possible to exceed the guaranteed resolution on most electron microscopes by careful attention to microscope parameters essential for high resolution work. While our experience is related to a Philips EM-200, we hope that some of these comments will apply to all electron microscopes.The first considerations are vibration and magnetic fields. These are usually measured at the pre-installation survey and must be within specifications. It has been our experience, however, that these factors can be greatly influenced by the new facilities and therefore must be rechecked after the installation is completed. The relationship between the resolving power of an EM-200 and the maximum tolerable low frequency interference fields in milli-Oerstedt is 10 Å - 1.9, 8 Å - 1.4, 6 Å - 0.8.

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High-resolution calorimetry in pulsed magnetic fields

Review of Scientific Instruments ◽

10.1063/5.0040655 ◽

2021 ◽

Vol 92 (4) ◽

pp. 043901

Author(s):

Shusaku Imajo ◽

Chao Dong ◽

Akira Matsuo ◽

Koichi Kindo ◽

Yoshimitsu Kohama

Keyword(s):

High Resolution ◽

Magnetic Fields ◽

Pulsed Magnetic Fields

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Magnetic Fields in the Lower Corona Associated with the Expanding Limb Burst On March 30th 1969 Inferred from the Microwave High-Resolution Observations

Symposium - International Astronomical Union ◽

10.1017/s0074180900022853 ◽

1971 ◽

Vol 43 ◽

pp. 413-416 ◽

Cited By ~ 4

Author(s):

Shinzo Énomé ◽

Haruo Tanaka

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Magnetic Fields ◽

The West ◽

Lower Corona ◽

Energetic Electrons ◽

West Limb ◽

Flare Region ◽

Solar Microwave ◽

Solar Microwave Burst

An expansion of the source of a great solar microwave burst was observed a little beyond the west limb on March 30, 1969. This expansion is interpreted in terms of diffusion of energetic electrons in a turbulent magnetic field in the flare region. The height of the source is estimated to have been 104 km.

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Magnetic fields of rapidly oscillating Ap stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100117099 ◽

1993 ◽

Vol 139 ◽

pp. 132-132

Author(s):

G. Mathys

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Magnetic Fields ◽

Zeeman Effect ◽

Rotation Frequency ◽

Spectral Lines ◽

Driving Mechanism ◽

Line Splitting ◽

Ap Stars ◽

The Magnetic Field

Magnetic field appears to play a major role in the pulsations of rapidly oscillating Ap (roAp) stars. Understanding of the behaviour of these objects thus requires knowledge of their magnetic field. Such knowledge is in particular essential to interpret the modulation of the amplitude of the photometric variations (with a frequency very close to the rotation frequency of the star) and to understand the driving mechanism of the pulsation. Therefore, a systematic programme of study of the magnetic field of roAp stars has been started, of which preliminary (and still very partial) results are presented here.Magnetic fields of Ap stars can be diagnosed from the Zeeman effect that they induced in spectral lines either from the observation of line-splitting in high-resolution unpolarized spectra (which only occurs in favourable circumstances) or from the observation of circular polarization of the lines in medium- to high-resolution spectra.

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Characterising the surface magnetic fields of T Tauri stars with high-resolution near-infrared spectroscopy

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935695 ◽

2019 ◽

Vol 630 ◽

pp. A99 ◽

Cited By ~ 5

Author(s):

A. Lavail ◽

O. Kochukhov ◽

G. A. J. Hussain

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Magnetic Fields ◽

Large Scale ◽

Near Infrared ◽

Field Measurements ◽

T Tauri Stars ◽

Small Scale ◽

Surface Magnetic Field ◽

T Tauri

Aims. In this paper, we aim to characterise the surface magnetic fields of a sample of eight T Tauri stars from high-resolution near-infrared spectroscopy. Some stars in our sample are known to be magnetic from previous spectroscopic or spectropolarimetric studies. Our goals are firstly to apply Zeeman broadening modelling to T Tauri stars with high-resolution data, secondly to expand the sample of stars with measured surface magnetic field strengths, thirdly to investigate possible rotational or long-term magnetic variability by comparing spectral time series of given targets, and fourthly to compare the magnetic field modulus ⟨B⟩ tracing small-scale magnetic fields to those of large-scale magnetic fields derived by Stokes V Zeeman Doppler Imaging (ZDI) studies. Methods. We modelled the Zeeman broadening of magnetically sensitive spectral lines in the near-infrared K-band from high-resolution spectra by using magnetic spectrum synthesis based on realistic model atmospheres and by using different descriptions of the surface magnetic field. We developped a Bayesian framework that selects the complexity of the magnetic field prescription based on the information contained in the data. Results. We obtain individual magnetic field measurements for each star in our sample using four different models. We find that the Bayesian Model 4 performs best in the range of magnetic fields measured on the sample (from 1.5 kG to 4.4 kG). We do not detect a strong rotational variation of ⟨B⟩ with a mean peak-to-peak variation of 0.3 kG. Our confidence intervals are of the same order of magnitude, which suggests that the Zeeman broadening is produced by a small-scale magnetic field homogeneously distributed over stellar surfaces. A comparison of our results with mean large-scale magnetic field measurements from Stokes V ZDI show different fractions of mean field strength being recovered, from 25–42% for relatively simple poloidal axisymmetric field topologies to 2–11% for more complex fields.

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HIGH–RESOLUTION MEASUREMENT OF THE RESPONSE OF AN ISOLATED BUBBLE DOMAIN TO PULSED MAGNETIC FIELDS

Collected Papers of Carl Wieman ◽

10.1142/9789812813787_0106 ◽

2008 ◽

pp. 761-763

Author(s):

B. R. Brown ◽

G. R. Henry ◽

R. W. Koepcke ◽

C. E. Wieman

Keyword(s):

High Resolution ◽

Magnetic Fields ◽

Pulsed Magnetic Fields ◽

High Resolution Measurement ◽

Resolution Measurement

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High-resolution NMR in inhomogeneous magnetic fields

Journal of Magnetic Resonance (1969) ◽

10.1016/0022-2364(76)90038-x ◽

1976 ◽

Vol 24 (2) ◽

pp. 291-294 ◽

Cited By ~ 7

Author(s):

Geoffrey Bodenhausen ◽

Ray Freeman ◽

Reinhard Niedermeyer ◽

David L Turner

Keyword(s):

High Resolution ◽

Magnetic Fields ◽

High Resolution Nmr

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Are the photospheric sunspots magnetically force-free in nature?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311015481 ◽

2010 ◽

Vol 6 (S273) ◽

pp. 333-337 ◽

Cited By ~ 1

Author(s):

Sanjiv Kumar Tiwari

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Magnetic Fields ◽

Magnetic Energy ◽

Sufficient Conditions ◽

Field Measurements ◽

Magnetic Behaviour ◽

Optical Telescope ◽

Energy Gradient ◽

Necessary And Sufficient

AbstractIn a force-free magnetic field, there is no interaction of field and the plasma in the surrounding atmosphere i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of many magnetic parameters like magnetic energy, gradient of twist of sunspot magnetic fields (computed from the force-free parameter α), including any kind of extrapolations heavily hinge on the force-free approximation of the photospheric magnetic fields. The force-free magnetic behaviour of the photospheric sunspot fields has been examined by Metcalf et al. (1995) and Moon et al. (2002) ending with inconsistent results. Metcalf et al. (1995) concluded that the photospheric magnetic fields are far from the force-free nature whereas Moon et al. (2002) found the that the photospheric magnetic fields are not so far from the force-free nature as conventionally regarded. The accurate photospheric vector field measurements with high resolution are needed to examine the force-free nature of sunspots. We use high resolution vector magnetograms obtained from the Solar Optical Telescope/Spectro-Polarimeter (SOT/SP) aboard Hinode to inspect the force-free behaviour of the photospheric sunspot magnetic fields. Both the necessary and sufficient conditions for force-freeness are examined by checking global as well as as local nature of sunspot magnetic fields. We find that the sunspot magnetic fields are very close to the force-free approximation, although they are not completely force-free on the photosphere.

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