Cosmic particles

Schimmerling, W., Budinger, T.F., Eds. Manned Exploration of Deep Space, Cosmic Particle Biology and Health , Lawrence Berkeley Laboratory Berkeley, California, 1989. 

Preliminary results from measurements of an argon sample collected at Oakland, Calif., Dec. 12, 1967, indicate that the atmospheric argon-37 concentration is approximately 40 times the estimated cosmic particle-produced level. The sample was measured during three months, and the decay followed the argon-37 half-life. This value is preliminary and must be verified by additional sample analysis. Owing to weapons testing,... 

Lai (13) gives the specific activity of argon-37 in the atmosphere produced by cosmic particle reactions as 0.19 d.p.m./kg. air in the stratosphere and 2.1 X 10 2 d.p.m./kg. air in the troposphere. The radioactivity expected in a 10-liter sample of purified argon from the troposphere would be 3.98 X 10"2 d.p.m. It should be possible to measure less than twice this radioactivity level using this detector. 

Atmospheric argon-37 has been measured in the counter at a concentration of about 40 times the estimated cosmic particle concentration. The minimum detectable limit for measuring argon at 10 atm. for a 1000-minute counting is 0.1 d.p.m./meter3 air, or about two times the cosmic particle-produced concentration in the troposphere. It should be possible to measure cosmic particle produced argon in the stratosphere. 

Tiny solid cosmic particles - often referred to as dust - are the ultimate source of solids from which rocky planets, planetesimals, moons, and everything on them form. The study of the dust particles genesis and their evolution from interstellar space through protoplanetary disks into forming planetesimals provides us with a bottom-up picture on planet formation. These studies are essential to understand what determines the bulk composition of rocky planets and, ultimately, to decipher the formation history of the Solar System. Dust in many astrophysical settings is readily observable and recent ground- and space-based observations have transformed our understanding on the physics and chemistry of these tiny particles. 

Nishiizumi K., Arnold J. R., Fink D., Klein J., Middleton R., Brownlee D. E., and Maurette M. (1991c) Exposure history of individual cosmic particles. Earth Planet. Sci. Lett. 104, 315-324. 

There are essentially three sources of radioactive elements. Primordial nuclides are radioactive elements whose half-lives are comparable to the age of our solar system and were present at the formation of Earth. These nuclides are generally referred to as naturally occurring radioactivity and are derived from the radioactive decay of thorium and uranium. Cosmogenic nuclides are atoms that are constantly being synthesized from the bombardment of planetary surfaces by cosmic particles (primarily protons ejected from the Sun), and are also considered natural in their origin. The third source of radioactive nuclides is termed anthropogenic and results from human activity in the production of nuclear power, nuclear weapons, or through the use of particle accelerators. 

When the primary cosmic particles enter the earth s atmosphere, they collide with the matter of the atmosphere and are annihilated. In this annihilation process a large number of new particles are formed whose total kinetic energy is less than that of the original primary radiation but whose total rest mass is larger than that of the primary particle. A 10 GeV cosmic helium ion may produce a shower of 50 - 100 new highly ionizing particles, cf. Fig. 10.2. The main reaction products are particles which are known as pions, designated ir. 

Figure 10.3 shows the effect of high energy cosmic rays hitting the helmets of Apollo 12 astronauts. It is probable that the cosmic ray intensity will put a limit to how long man can endure in outer space it has been calculated that in a journey to the planet Mars about 0.1% of the cerebral cortex will be destroyed. The aimihilation process occurs to such an extent that below an altitude of approximately 25 km above the earth the number of primary cosmic particles has been reduced to quite a small fraction of the original intensity. 

According to Urey, Suess, and others, the accretion of cosmic particles during the formation process released gravitational energy also the higher conc tration of radioactive nuclides in the primordial cloud (Fig. 17.11) contributed to heat and melt the solid material of our Earth-to-be. The Earth s tenqierature was 40 — 50% higher than today about 3.3 Gy ago. Not until a solid crust was formed could the radioactive clock begin to tick. This did... 

J. Under the same assunq>tion as above, what amount of damage will be caused by cosmic radiation Assume that the cosmic particles produce 3 x 10 ion pairs s m of the body. 

All of the peaks due to the nuclides mentioned above will be sat on a continuum due to Compton scattering of the gamma-rays and backscattering and bremmstrahlung due to direct interaction of cosmic particles. This will be discussed further in Section 13.4.6. 

From 2 to 7 MeV, the continuum is attributed to cosmic particles passing through only part of the detector. 

These emissions of light occur over the whole upper atmosphere and should be distinguished from the aurora which are reactions induced by collisions with gas molecules at higher altitude, of charged cosmic particles captured in the Earth s magnetic field, and frequently visible in the night sky of the northern and southern latitudes. 

A simple lifetime monitor can be constructed which makes use of cosmic particles (minimum ionizing particles) as ionization source. A cosmic ray telescope is employed to select particles traversing the parallel plate ionization chamber parallel... 

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