Hard X-rays

Hanford, usefulness of comparative absorptiometry at, 96 Hard" x-rays, 11... 

F. Schotte, S. Techert, P. Anhnrud, V. Srajer, K. Moffat, and M. Wulff, Picosecond structural studies using pulsed synchrotron radiation. In D. M. Mills (ed.), Third-Generation Hard X-Ray Synchrotron Radiation Sources Source Properties, Optics, and Experimental Techniques, Chap. 10, p. 345-402. John Wiley Sons, Hobokon, NJ, 2002. 

The basic function of the spectrometer is to separate the polychromatic beam of radiation coming from the specimen in order that the intensities of each individual characteristic line can be measured. In principle, the wide variety of instruments (WDXRF and EDXRF types) differ only in the type of source used for excitation, the number of elements which they are able to measure at one time and the speed of data collection. Detectors commonly employed in X-ray spectrometers are usually either a gas-flow proportional counter for heavier elements/soft X-rays (useful range E < 6keV 1.5-50 A), a scintillation counter for lighter elements/hard X-rays (E > 6keV 0.2-2 A) or a solid-state detector (0.5-8 A). 

There are a number of experimental factors to be considered in a surface EXAFS experiment. First of all, one needs access to a synchrotron source (for the reasons previously mentioned) with significant flux in the hard X-ray region. In the United States, three such facilities exist and these are ... 

Radiation from AGNs, some of which can also be reprocessed by dust, but which differs from the other two sources in being powered by gravitational rather than nuclear energy and therefore not associated with nucleosynthesis. This contribution is probably minor, however, based on the abundance of massive black holes (Madau Pozzetti 2000), or on that of obscured hard X-ray sources (Brusa, Comastri Vignali 2001). 

Fig. 3.1. Left visible pump/X-ray probe scheme for femtosecond TRXRD experiments. Hard X-ray pulses are generated by shining intense femtosecond laser pulses on a metal target (laser plasma X-ray source). Right geometrical structure factor of bismuth as a function of inter-atomic distance for diffraction from (111) and (222) lattice planes. From [1] and [2]...

Mills, D. M., ed. (2002). Third-Generation Hard X-ray Synchrotron Radiation Sources Source Properties, Optics, and Experimental Techniques. John Wiley and Sons, New York. 

X-rays span three decades in wavelength, frequency, and energy. From about 0.12 to 12 keV they are classified as soft x-rays, and from 12 to 120 keV as hard x-rays, due to their penetrating abilities. X-rays are a form of ionizing radiation, and as such, they can be dangerous to living organisms. 

F. Schotte, S. Techert S, P. A. Anfinrud, V. Srajer, K. Moffat and M. Wulff. Recent Advances in the Generation of Pulsed Synchrotron Radiation Suitable for Picosecond Time-resolved X-ray Studies. Third-Generation Hard X-ray Synchrotron Radiation Sources. Edited by Dennis Mills, (ISBN 0-471-31433-1). 345-401, 2002... 

As the column depth of the supernova ejecta decreases as t 2, 7-rays and hard X-rays suffer from less Compton scattering and photoelectric absorption and eventually emerge from the surface. The timing of their emergences and light curves are sensitive to E, Menv, and the distribution of elements. In other words, X-ray and 7-ray observations provide another good diagnosis of the supernova interior. 

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