scholarly journals Untersuchung der harten Röntgen-Strahlung am Theta-Pinch

1965 ◽  
Vol 20 (5) ◽  
pp. 675-682 ◽  
Author(s):  
E. Barbian
Keyword(s):  
Potential Field ◽  
Tube Wall ◽  
Field Configuration ◽  
X Rays ◽  
Degree Of Ionization ◽  
X Ray ◽  
Drift Motion ◽  
Theta Pinch ◽  
High Degree ◽  
Absorption Measurements

Hard X-rays of several 100 keV can be observed during a few halfcycles of a thetapinch discharge before breakdown. No additional preionization was used. This X-ray emission can be explained by bremsstrahlung of freely accelerated electrons colliding with the wall of the tube.Investigation of the location of X-ray emission shows that the drift motion of the electrons to the wall is influenced by the potential field of the coil. On the other hand no influence of this potential field can be observed in the halfwave before breakdown when a high degree of ionization has been reached.Thus time dependent local X-ray emission can indicate the prevailing field configuration.The ratio of X-ray intensities before and behind a Cu absorber is compared with theoretically calculated values. Absorption measurements at the discharge tube wall at the middle and outside of the coil show that a transport mechanism affects the energy distribution of the electrons reaching the wall.

scholarly journals Diffuse cosmic X-rays from non-thermal intergalactic bremsstrahlung

1970 ◽  
Vol 37 ◽  
pp. 392-401
Author(s):  
Joseph Silk
Keyword(s):  
Cosmic Rays ◽  
Intergalactic Medium ◽  
Energy Requirement ◽  
Cosmic Ray ◽  
X Rays ◽  
Degree Of Ionization ◽  
X Ray ◽  
Normal Galaxies ◽  
X Ray Background ◽  
High Degree

The diffuse X-ray background between 1 keV and 1 MeV is interpreted as non-thermal bremsstrahlung in the intergalactic medium. The observed break in the X-ray spectrum at ∼40 keV yields the heat input to the intergalactic medium, the break being produced by ionization losses of sub-cosmic rays. Proton bremsstrahlung is found not to yield as satisfactory an agreement with observations as electron bremsstrahlung: excessive heating tends to occur. Two alternative models of cosmic ray injection are discussed, one involving continuous injection by evolving sources out to a redshift of about 3, and the other model involving injection by a burst of cosmic rays at a redshift of order 10. The energy density of intergalactic electrons required to produce the observed X-rays is ∼ 10−4 eV/cm3. Assuming a high density (∼ 10−5 cm−3) intergalactic medium, the energy requirement for cosmic ray injection by normal galaxies is ∼ 1058–59ergs/galaxy in sub-cosmic rays. The temperature evolution of the intergalactic medium is discussed, and we find that a similar energy input is also required to explain the observed high degree of ionization (if 3C9 is at a cosmological distance).

GENERATION OF X-RAYS WITH A HIGH DEGREE OF LONGITUDINAL COHERENCE

2007 ◽  
Vol 21 (03n04) ◽  
pp. 513-518
Author(s):  
ROBERT ROSSMANITH
Keyword(s):  
Synchrotron Radiation ◽  
Storage Rings ◽  
Light Sources ◽  
X Rays ◽  
X Ray ◽  
Electron Accelerators ◽  
Longitudinal Coherence ◽  
High Degree

Synchrotron radiation produced either in storage rings or SASE-FELs is longitudinally incoherent. In this paper a way to produce short longitudinally coherent X-ray pulses is discussed. In addition it is investigated if these sources can be modified to use them as light sources for vacuum electron accelerators.

scholarly journals STUDIES ON X-RAY EFFECTS

1922 ◽  
Vol 35 (4) ◽  
pp. 475-485 ◽  
Author(s):  
Waro Nakahara ◽  
James B. Murphy
Keyword(s):  
Small Dose ◽  
Biological Effect ◽  
Lymphoid Organs ◽  
X Rays ◽  
Thin Glass ◽  
X Ray ◽  
Spark Gap ◽  
Mitotic Figures ◽  
High Degree ◽  
Ray Effects

A study has been made of the biological effect of a small dose of soft x-rays given off by a special water-cooled tube with a window of thin glass, operated at ½ inch spark-gap and 11 milliamperes. Mice exposed for 1 minute show 2 days later in the blood an increase in the number of lymphocytes and in the lymphoid organs an increased number of mitotic figures. There occurs also a marked dilatation of the vessels of the suprarenals, particularly between the cortex and medulla. The latter condition did not appear until after 24 hours and was still present 14 days after the treatment. No change was detected in other organs. Mice treated in this way showed a high degree of resistance to cancer transplants. The amount of resistance varied with the time of the inoculation after the treatment. The resistance was not increased before 3 days after and was at its highest point 10 days after the treatment.

scholarly journals Divergent-beam X-ray photography of crystals

1947 ◽  
Vol 240 (817) ◽  
pp. 219-250 ◽  
Keyword(s):  
Wave Length ◽  
Impurity Content ◽  
Type I ◽  
X Rays ◽  
Divergent Beam ◽  
X Ray ◽  
Air Temperatures ◽  
High Degree ◽  
Good Agreement

Divergent-beam X-ray photography of single crystals by transmission can be used to study the ‘extinction’, that is, the diminution of the transmitted radiation that takes place at the Bragg reflexion angles. The intensity and geometry of the absorption lines observed give useful information about the texture of the crystal. Divergent beam photographs have shown that many crystals of organic compounds are unexpectedly perfect, and that sudden cooling to liquid-air temperatures will increase the mosaic character of their structure by an important factor and make them more suitable for structural analysis by the usual methods. Type I diamonds, and natural ice even near to its melting-point, are also found to possess a high degree of perfection, which cannot be removed by liquid-air treatment. The divergent beam method may be used for the determination of orientation, but it is important that the wave-length of X-rays employed should be correctly related to the size and nature of the crystal. In certain favourable cases it is possible to make precision measurements of lattice constant or of wave-length from divergent beam photographs, without the use of any kind of precision apparatus. By such means it has been shown that the C—C distance in individual diamonds varies from 1541.53(± 0-02) to 1541.27X, (1.54465-1-54440A), a difference presumably due to varying impurity content. Using diamond and a brass anticathode, the Zn Ka 1 wave-length, relative to Cu K Ka 1 as 1537.40X, is found to be 1432.21 ( ± 0-04) X. Temperature control would improve the accuracy of this measurement, which is, however, in good agreement with the latest value obtained by orthodox precision methods.

X-Ray Investigation of the Amorphous State of Rubber

1955 ◽  
Vol 28 (3) ◽  
pp. 728-731 ◽  
Author(s):  
V. I. Kasatochkin ◽  
B. V. Lukin
Keyword(s):  
Diffraction Pattern ◽  
Amorphous State ◽  
Coherent Scattering ◽  
X Rays ◽  
X Ray Diffraction ◽  
Molecular Liquids ◽  
X Ray ◽  
Large Molecules ◽  
Molecular Substances ◽  
High Degree

Abstract The x-ray diffraction pattern of amorphous rubber, which is an amorphous ring, resembles the pattern of low-molecular liquids. In our previous work, it was established that the diffraction pattern observed is due to the coherent scattering of only those segments of the molecular chains in which the aggregation is analogous to that of low-molecular liquids, and is determined by the presence of a pseudo-order. A large part of the links of the molecular chains, owing to the prevailing disorder, scatters the x-rays incoherently, like scattering by a gas. For one component of amorphous rubber, the concept of “liquid phase” was introduced, and, for the other, that of “gaseous phase”, thereby subdividing them according to the type of scattering of x-rays. Amorphous rubber, according to our data, contains a large number of chair segments which are characterized by a high degree of disorder. The presence of such a disordered molecular phase is a general and characteristic property of high-molecular substances, and is caused by natural obstacles in the dense packing of the large molecules. This characteristic of molecular aggregation is undoubtedly reflected in the physical-mechanical properties of polymers.

scholarly journals Ptychographic X-ray speckle tracking with multi-layer Laue lens systems

2020 ◽  
Vol 53 (4) ◽  
pp. 927-936 ◽  
Author(s):  
Andrew J. Morgan ◽  
Kevin T. Murray ◽  
Mauro Prasciolu ◽  
Holger Fleckenstein ◽  
Oleksandr Yefanov ◽  
...  
Keyword(s):  
High Resolution ◽  
Speckle Tracking ◽  
X Rays ◽  
Chemical Sensitivity ◽  
X Ray ◽  
Laue Lens ◽  
Layer Deposition ◽  
Recent Developments ◽  
Ray Path ◽  
High Degree

The ever-increasing brightness of synchrotron radiation sources demands improved X-ray optics to utilize their capability for imaging and probing biological cells, nano-devices and functional matter on the nanometre scale with chemical sensitivity. Hard X-rays are ideal for high-resolution imaging and spectroscopic applications owing to their short wavelength, high penetrating power and chemical sensitivity. The penetrating power that makes X-rays useful for imaging also makes focusing them technologically challenging. Recent developments in layer deposition techniques have enabled the fabrication of a series of highly focusing X-ray lenses, known as wedged multi-layer Laue lenses. Improvements to the lens design and fabrication technique demand an accurate, robust, in situ and at-wavelength characterization method. To this end, a modified form of the speckle tracking wavefront metrology method has been developed. The ptychographic X-ray speckle tracking method is capable of operating with highly divergent wavefields. A useful by-product of this method is that it also provides high-resolution and aberration-free projection images of extended specimens. Three separate experiments using this method are reported, where the ray path angles have been resolved to within 4 nrad with an imaging resolution of 45 nm (full period). This method does not require a high degree of coherence, making it suitable for laboratory-based X-ray sources. Likewise, it is robust to errors in the registered sample positions, making it suitable for X-ray free-electron laser facilities, where beam-pointing fluctuations can be problematic for wavefront metrology.

scholarly journals Multiepoch, multiwavelength study of accretion onto T Tauri

2018 ◽  
Vol 618 ◽  
pp. A55 ◽  
Author(s):  
P. C. Schneider ◽  
H. M. Günther ◽  
J. Robrade ◽  
J. H. M. M. Schmitt ◽  
M. Güdel
Keyword(s):  
Near Infrared ◽  
Accretion Rate ◽  
Strong Shock ◽  
Field Configuration ◽  
Optical Data ◽  
X Rays ◽  
Coronal Emission ◽  
X Ray ◽  
T Tauri ◽  
The Impact

Classical T Tauri stars (CTTSs) accrete matter from the inner edge of their surrounding circumstellar disks. The impact of the accretion material on the stellar atmosphere results in a strong shock, which causes emission from the X-ray to the near-infrared (NIR) domain. Shock velocities of several 100 km s−1 imply that the immediate post shock plasma emits mainly in X-rays. Indeed, two X-ray diagnostics, the so-called soft excess and the high densities observed in He-like triplets, differentiate CTTSs from their non-accreting siblings. However, accretion shock properties derived from X-ray diagnostics often contradict established ultraviolet (UV)–NIR accretion tracers and a physical model simultaneously explaining both, X-ray and UV–NIR accretion tracers, is not yet available. We present new XMM-Newton and Chandra grating observations of the CTTS T Tauri combined with UV and optical data. During all epochs, the soft excess is large and the densities derived from the O VII and Ne IX He-like triplets are compatible with coronal densities. This confirms that the soft X-ray emission cannot originate in accretion funnels that carry the bulk of the accretion rate despite T Tauri’s large soft excess. Instead, we propose a model of radially density stratified accretion columns to explain the density diagnostics and the soft excess. In addition, accretion rate and X-ray luminosity are inversely correlated in T Tauri over several epochs. Such an anti-correlation has been observed in samples of stars. Hence the process causing it must be intrinsic to the accretion process, and we speculate that the stellar magnetic field configuration on the visible hemisphere affects both the accretion rate and the coronal emission, eventually causing the observed anti-correlation.

scholarly journals A critical-absorption photometer for the study of the Compton effect

1928 ◽  
Vol 119 (783) ◽  
pp. 526-530
Keyword(s):  
Absorption Coefficient ◽  
Wave Length ◽  
Light Element ◽  
Compton Effect ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Length Changes ◽  
Absorption Measurements ◽  
Ray Scattering

That a change of wave-length occurs in X-ray scattering was first indicated by absorption measurements with the ionisation chamber, which showed that the absorption coefficient of a light element like aluminium was slightly greater for the scattered than for the primary X-rays. Later more conclusive and direct evidence was obtained when spectrometric analysis of the scattered X-rays was made first by the ionisation and afterwards by the photographic method. This analysis disclosed the existence of an unshifted as well as the shifted line, and showed also that the latter becomes relatively more prominent with diminishing wave-length and lower atomic number of the scattering element. After the main features of the Compton effect were established by means of spectrometric measurements, however, absorption measurements with the ionisation method have again been employed for a detailed study of the phenomenon, for such measurements are much quicker than the spectrum experiments, where the final energy available is much smaller on account of the double scattering involved. As mentioned above, the absorption measurements were based on the slight increase in the absorption coefficient of a light element when the wave-length changes from the unmodified to the modified value. The much larger and sudden diminution in absorption of X-rays when the frequency is altered from the short to the long wave-length side of the critical K-absorption limit of the element used as a filter, furnishes us with an easy and convenient method of exhibiting the wave-length change in X-ray scattering. In the present paper will be described a photographic wedge photometer based on this principle, which enables the characteristics of the Compton effect to be readily observed. It may be pointed out that the same idea could no doubt be utilised also in connection with the ionisation measurements of the Compton effect.

scholarly journals THE PRODUCTION OF PERSISTENT ALOPECIA IN RABBITS BY X-RAYS OF VARIOUS DEGREES OF HARDNESS

1925 ◽  
Vol 42 (4) ◽  
pp. 517-522 ◽  
Author(s):  
Harry Clark ◽  
Ernest Sturm
Keyword(s):  
X Rays ◽  
Abdominal Skin ◽  
X Ray ◽  
Minimum Dose ◽  
Air Ionization ◽  
High Degree

1. The minimum dose of x-ray, of each of three degrees of hardness, required to produce persistent alopecia of the abdominal skin of normal white rabbits has been studied. 40 kilovolt rays filtered by 0.5 mm., 50 kilovolt rays filtered by 1 mm., and 70 kilovolt rays filtered by 1.5 mm. of aluminium were employed. The 70 kilovolt work is unfinished. 2. Under constant conditions of treatment, the animals were found to react with a high degree of consistency. 3. The values of the critical minimum doses expressed in terms of air ionization (pair of ions per gm. of air divided by 1015), for rays produced at 30, 40, 50, and 70 kilovolt peak, are 2.04, 3.7, 4.5, and over 5.1 respectively. The 30 kilovolt value is taken from a previous paper. 4. It is shown that the alopecia reaction does not run parallel to the erythema and pigmentation reactions.

Valence-contrast studies by resonant diffraction with synchrotron radiation; the rôle of X-ray absorption measurements

1992 ◽  
Vol 25 (5) ◽  
pp. 654-657 ◽  
Author(s):  
A. P. Wilkinson ◽  
A. K. Cheetham
Keyword(s):  
Optical Theorem ◽  
Anomalous Scattering ◽  
X Rays ◽  
Acta Cryst ◽  
X Ray ◽  
X Ray Absorption ◽  
Kronig Relation ◽  
Absorption Measurements ◽  
Good Agreement

The X-ray absorption spectra of GaCl2, GaAlCl4 and GaCl3 have been measured in the vicinity of the Ga K edge and values of f′′ and f′ estimated for GaI and GaIII from the latter two spectra by using the optical theorem and the Kramers–Kronig relation. The resulting f′ values are compared with those previously determined from anomalous-scattering measurements with synchrotron X-rays on the compound GaCl2 [Wilkinson, Cheetham & Cox (1991). Acta Cryst. B47, 155–161] and found to be in good agreement. The use of anomalous scattering methods for distinguishing oxidation states is discussed in the light of these results and others found in the literature.

Sign in / Sign up

Export Citation Format

Share Document