The 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.

The Soviet mission Spectrum-X-Gamma is planned to be launched in 1993. The prime instrument is the SODART (Soviet Danish Röntgen Telescope) consisting of two telescope units, each with a thin foil nested mirror assembly and a number of focal plane instruments. These include gas detectors, a solid state detector and a polarimeter. One of the telescopes is equipped with an objective crystal spectrometer for high resolution spectroscopy of strong sources. The expected energy resolution and sensitivities for iron line detection are presented and compared with some current research goals.

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.

The study of cosmic ray access to locations inside the geomagnetic field has evolved in a manner that has led to some misunderstanding and misapplication of the terminology originally developed to describe particle access. This paper presents what is believed to be a useful set of definitions for cosmic ray cutoff terminology for use in theoretical and experimental cosmic ray studies.

We report measurements of the abundances relative to iron of the elements scandium through manganese in galactic cosmic rays in the energy interval 0.7 to 18 GeV/n using data collected by our cosmic ray telescope on the HEAO-3 satellite. The variation versus energy of the abundance ratio of manganese over iron is markedly flatter than that of other iron secondaries. This difference is interpreted as being due to 54Mn survival at E > 15 GeV/n and to its progressive beta decay at lower energies.

A predictor-corrector method for the problem of a charged particle in a time-independent magnetic field is presented. It takes the helix trajectory in a homogeneous field as the basic approximation, and treats magnetic field gradients as a sixth order perturbation. The method is applied to a cosmic-ray problem in which an evaluation of the magnetic field costs ≈ 1000 arithmetic operations. A 75–120% gain in overall computing speed, relative to the Runge-Kutta method, is reported.

Abundances of the light elements in cosmic rays were measured with a balloon-borne telescope containing four Ĉerenkov counters and a neon flash tube hodoscope. In order to extract Li events from the surrounding background of proton and He interactions in the instrument, an event was rejected if the hodoscope indicated the presence of more than one particle near the top of the instrument. The selection strategy led to essentially complete charge separation between He and Li. Some events were lost because the hodoscope was sensitive to δ-electrons; a correction for the charge dependence of this loss was carried out, affecting the measured Li/B ratio by ∼2%. Ratios between integral fluxes were measured above a geomagnetic cut-off ∼1.9 GV/c and above 650 MeV/nucleon kinetic energy. Li/B ratios found in the two cases were 0.73±0.05 and 0.70±0.05; the Li/C ratio was found to be 0.21±0.02 in both cases. These results agree with Li abundances reported by several other observers. They also agree with Li/B ratios predicted from a leaky-box type of propagation model as well as from a recent two-component model by Peters and Westergaard.

A balloon-borne cosmic-ray telescope containing 4 Cerenkov counters and a neon flash tube hodoscope was flown from Sioux City, Iowa in September 1974. The data have been reanalyzed, using information of flashed tubes to reject events due to proton and He interactions. The new event selection has reduced charge overlap between He and Li to an insignificant level, so that abundance ratios involving Li can now be measured with the instrument. Precise correction factors for events lost by inefficiency of the hodoscope have been derived from flight data; they lead to improved accuracy in measurements of light elements.