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Observation of cosmic-ray particles with Z greater than 35.

The results of two flights conducted in Texas in September 1968 are reported, giving attention to experimental details, the charge spectrum, and the primary flux of very very heavy cosmic rays. Considerable interest is attached to the observation of uranium, thorium, and transuranic nuclei in the cosmic radiation. It is found that the relative abundances of the charge groups in the ranges from 35 to 40 and from 41 to 50 deviate significantly from solar system abundances.

Blanford, G. E., Jr.↗

Elemental abundances in interplanetary dust

The paper reports on measurements taken of elemental abundances in two interplanetary dust grains. Meteoroidal residue found inside micrometeoritic craters was discovered by optically scanning the 800 sq cm aluminum surface of the S-228 transuranic cosmic-ray experiment exposed to space for 67d during the Skylab-IV mission. Crater analyses for two randomly sampled meteoroids showed a composition consistent with troilite in the 9 micron-minute particle. Chondritic abundances were found in the 30 micron-minute particle. Particles of similar size and chemistry were common in carbonaceous chondrite meteorites. The inferred grain sizes within the 30 micron-minute particle provided evidence for the similarity to carbonaceous chondrites rather than to other meteorite types.

Brownlee, D. E.↗

TREK - A cosmic-ray experiment on the Russian space station Mir

The goals of the TREK experiment, now in place on the Mir space station, are to resolve and measure the composition of both odd-Z and even-Z cosmic-ray nuclei up to uranium, to measure the isotopic composition of Fe-group nuclei, and to search for transuranic nuclei and exotic particles such as strangelets. To collect tracks of ultraheavy cosmic rays, exterior panels holding an array of BP-1 phosphate glass 1.2 sq m in area and 16 plates thick are now mounted outside the Kvant-2 module on Mir. Heaters and relays regulate the temperature of the glass at 25 +/- 5 C. The detectors will record about 1000 cosmic-ray tracks with Z greater than or equal to 50 during about 2.5 years. An interior panel consisting of an array 0.09 sq m in area and 32 plates thick and mounted on the inside wall of the Soyuz spacecraft will collect tracks of about 13,000 Fe and 500 Ni nuclei.

Price, P. B.↗

The Energetic Trans-Iron Cosmic-ray Experiment (ENTICE)

The ENTICE experiment is one of two instruments that comprise the "Orbiting Astrophysical Spectrometer in Space (OASIS)", which is presently undergoing a NASA "Astrophysics Strategic Mission Concept Study". ENTICE is designed to make high precision measurements of the abundances of individual elements from neon through the actinides and, in addition, will search for possible superheavy nuclei in the galactic cosmic rays. The ENTICE instrument utilizes silicon detectors, aerogel and acrylic Cherenkov counters, and a scintillating optical fiber hodoscope to measure the charge and energy of these ultra-heavy nuclei for energies greater than 0.5 GeV/nucleon. It is a large instrument consisting of four modules with a total effective geometrical factor of approx.20 sq m sr. Measurements made in space for a period of three years with ENTICE will enable us to determine if cosmic rays include a component of recently synthesized transuranic elements (Pu-94 and Cm-96), to measure the age of that component, and to test the model of the OB association origin of galactic cosmic rays. Additionally, these observations will enable us to study how diffusive shock acceleration of cosmic rays operates differently on interstellar grains and gas. Keywords: cosmic rays Galaxy:abundances

Binns, W. R.↗