Bjarne P. Byrnak

On cosmic-ray cut-off terminology

SummaryThe study of cosmic-ray access to locations within the geomagnetic field has evolved over the past fifty years. Cosmic-ray cut-off terminology, originally developed to describe particle access and cut-off rigidities, has not evolved with the scientific advances in the field, and misunderstandings and misapplications of historical work have occurred. This paper is an attempt to remedy this situation by clarifying the areas in which changes have occurred and by providing a cross reference between the historical terms and those terms now in use for innovative cosmic-ray studies which are underway in several laboratories.

Doubly curved imaging Bragg crystal spectrometer for x-ray astronomy

An x-ray spectrometer which is sensitive in the 0.5–7-keV energy range and is intended for use onboard astronomical satellites has been studied. The Bragg reflected rays from a doubly bent crystal positioned downstream of the focal plane of a grazing-incidence concentrator are focused along the axis of a position sensitive detector. A high throughput concentrator with densely nested thin-foil conical mirrors approximating a Wolter-1 system can be used without loss of spectral resolution. Other advantages include simultaneous (scanning free) coverage of the spectral range of interest, nearly stigmatic imaging, and crystal-limited resolution.

Bragg imaging of extended cosmic x-ray sources: the objective crystal spectrometer

A need exists for a high resolution (E/DeltaE greater, similar 500-1000), imaging (~5 x 5 arcmin pixel) spectrometer capable of studying cosmic x-ray sources with appreciable angular extent (up to 1-2 degrees ) and which emit a broad range of line spectra from highly ionized plasmas (oxygen through iron). A large flat objective crystal couples nicely to a modest resolution but high throughput x-ray concentrating telescope to produce high dispersion images of diffuse x-ray sources in each of the several lines present in the spectrum. Unprecedented spectral resolution is provided for point sources and, provided that they do not vary on rapid time scales, a spectrum can be scanned over a wide energy range with unparalleled sensitivity.

X-ray scattering measurements from thin foil X-ray mirrors

Thin foil X-ray mirrors are to be used as the reflecting elements in the telescopes of the X-ray satellites Spectrum-X-Gamma (SRG) and ASTRO-D. High resolution X-ray scattering measurements from the Au coated and dip-lacquered Al foils are presented. These were obtained from SRG mirrors positioned in a test quadrant of the telescope structure and from ASTRO-D foils held in a simple fixture. The X-ray data is compared with laser data and other surface structure data such as STM, atomic force microscopy (AFM), TEM, and electron micrography. The data obtained at Cu K-alpha(1), (8.05 keV) from all the mirrors produced on Al foils shows a scatter which limits the obtainable half-power width to above 1.5 arcmin. Mirrors based on electroformed Ni foils, however, show local regions with a factor of 4 better performance, and they are being developed for future applications.

Objective crystal spectrometer for the SPECTRUM-X-gamma satellite

The status of the Objective Crystal Spectrometer (OXS) to be flown on the Soviet Spectrum-X-Gamma satellite together with the X-ray investigation of two of the three natural crystals (LiF(220), Ge(111) and RAP(001) which are chosen as the baseline option are presented. An important result of this study is the approximately 50 percent higher resolution obtained by polishing the LiF(220) surface. The measured X-ray data has been used to determine the OXS specifications. A simulation of the performance of the OXS for the LiF(220)-case are presented. A novel design in which multilayers are coated on the LiF(220) and Ge(111) surfaces is presented. This design allows simultaneous spectroscopy in two energy bands each centered on cosmically interesting line emission regions. X-ray reflectivity measurements demonstrate that the crystal surface can be made sufficiently smooth for the application of the multilayer coating. The first X-ray reflectivity data of multilayers deposited on these surfaces are also reported.

Objective Crystal Spectrometer (OXS) For Bragg Imaging Of Extended X-Ray Sources

There exists a need for a high resolution (E/ΔE >500-1000), imaging (~5x5 arcmin pixel) spectrometer which is capable of studying sources with appreciable angular extent (up to 1-2 deg) and which emits line spectra from a broad range of highly ionized plasmas (oxygen through iron). A large flat objective crystal couples nicely to a modest resolution but high throughput x-ray concentrating telescope to produce high dispersion images of diffuse x-ray sources in each of the several lines present in the spectrum. Unprecedented spectral resolution is provided for point sources and, provided that they do not vary on rapid time scales, a spectrum can be scanned over a wide energy range with unparalled sensitivity.

High-Throughput Imaging Doubly Curved Bragg Crystal Spectrometer

An X-ray spectrometer which is sensitive in the 0.5-7 keV energy range has been studied. The rays which are Bragg reflected from a doubly bent crystal positioned downstream of the focal plane of a grazing-incidence concentrator are focused along the axis of a position sensitive detector. High throughput, simultaneous (scanning free) photon recording throughout the spectral range of interest, and crystal limited resolution which is achieved with a concentrator using a conical approximation to Wolter-1 optics are the main advantages. The sensitivity for spectral line detection in the presence of background may compete with that of broadband detectors.