Spallation Formula Deduced from Cascade and Evaporation Theories Compared with Experiments

1967 ◽  
Vol 22 (6) ◽  
pp. 972-974 ◽  
Author(s):  
U. Schwarz ◽  
H. Oeschger

A semiempirical formula σ(ΔA, E0, A0), giving the sum of the spallation cross sections of the products of an isobar as a function of the mass loss Δ A, the primary energy E0 of the irradiating particle and the atomic mass number A0 of the target nucleus is deduced. The formula is intended to be used for the interpretation of the spallation product distribution in meteorites, in the atmosphere of the earth and hopefully in cosmic dust and lunar surface samples.

1951 ◽  
Vol 29 (6) ◽  
pp. 518-544 ◽  
Author(s):  
L. Katz ◽  
A. G. W. Cameron

A method is presented for the computation of photonuclear cross sections from their X-ray activation or yield curves. It is based on the photon differences between successive Schiff representations of bremsstrahlung spectra and assumes that the activation curves have smooth first and second derivatives. Artificially prepared activation curves have been satisfactorily solved by this method, and the published photonuclear activation curves determined in this laboratory have been reanalyzed. The resulting cross section curves are in essential agreement with those originally determined; however the new values are believed to be more reliable. New constants for two proposed relationships between (γ, n) "resonance" peak energies and atomic mass number have been determined. Appended to the paper are tables of the Schiff bremsstrahlung spectra for maximum photon energies between 8 and 28 Mev. and also of special functions for cross section computations between the same energies.


1998 ◽  
Vol 07 (03) ◽  
pp. 341-355 ◽  
Author(s):  
B. K. Singh ◽  
S. K. Tuli

We report the results on partial production cross sections for Z=2 projectile fragments emitted in 28Si-emulsion interactions at 3.7 A GeV. Scaling behaviour of the multiplicity distribution of Z=2 PFs has been checked. The emission angle of Z=2 PFs has been measured and pseudorapidity distributions for these PFs have been obtained. We observe that the value of momentum spread σ(p) for Z=2 PFs grows with increasing mass number of the projectile. The emission of Z=2 PFs is consistent with a single source with an excitation energy of about 8.9 MeV. The data has been compared with available data reported for lighter as well as heavier projectiles at the same and/or different energies.


2005 ◽  
Vol 13 ◽  
pp. 763-763
Author(s):  
Donald B. Campbell ◽  
John K. Harmon ◽  
Micael C. Nolan ◽  
Steven J. Ostro

Nine comets have been detected with either the Arecibo (12.6 cm wavelength) or Goldstone (3.5 cm) radar systems. Included are six nucleus detections and five detections of echoes from coma grains. The radar backscatter cross sections measured for the nuclei correlate well with independent estimates of their sizes and are indicative of surface densities in the range of 0.5 to 1.0 g cm-3. Like most asteroids, comets appear to have surfaces that are very rough at scales much larger than the radar wavelength. Coma echo models can explain the radar cross sections using grain size distributions that include a substantial population of cm-sized grains. A long term goal of the cometary radar program has been the high resolution imaging of a cometary nucleus. Eleven short period comets are potentially detectable over the next two decades a few of which may be suitable for imaging. We are always waiting for the arrival of a new comet with an orbit that brings it within 0.1 AU of the earth.


1978 ◽  
Vol 11 (3) ◽  
pp. 251-308 ◽  
Author(s):  
L. A. Blumenfeld

The primary energy sources for all the organisms living on the Earth are either sunlight or the energy liberated during chemical transformations (mainly, oxidation) of certain substances – food. Within the cell this energy is transformed, accumulated, and then utilized to ensure a multitude of processes (synthesis of new low- and high-molecular compounds, muscle contraction, luminescence, transfer of ions counter to their concentration gradients, etc.).The role of universal ‘energy keeper’, of the, as it were, ‘energy small change’ in biology is played by the molecules of adenosine tri- phosphate (ATP) whose hydrolytic dissociation in water solutions with the formation of adenosine diphosphate (ADP) and inorganic phosphate (P1) is accompanied by a rather strong decrease of system energy.†


1972 ◽  
Vol 47 ◽  
pp. 22-31 ◽  
Author(s):  
S. K. Runcorn ◽  
S. Hofmann

The determination of the heights of points on the lunar surface by Earth based astronomy using the geometrical librations, although individually of low accuracy, still provides our best method of obtaining the global shape of the Moon. The intrinsic scatter of the results arises from the effects of ‘seeing’ and simple statistical analysis is required to derive valid conclusions about the shape. Baldwin's method of fitting ellipsoidal surfaces to the points on the maria and uplands, separately by the method of least squares proves to be a valuable tool.Analyses of the ACIC points and of the Pic du Midi studies of G. A. Mills show that good first descriptions of the global shape of the Moon for both the maria and uplands are triaxial ellipsoids with their long axes within 10° of the Earth direction, the major axis of the maria being about 1.3 km smaller than that of the uplands. Of particular significance is that the ellipticity of these surfaces is about 2½ times greater than the dynamical ellipticity; thus the non-hydrostatic figure of the Moon is not simply the result of distortion from a uniform Moon during its early history. The angular variation in density within the Moon cannot be simply a phenomena within the crust but must extend to a great depth. Convection could provide an explanation.The departures of the lunar surface from the idealised ellipsoids are also of interest. The circular maria are systematically depressed relative to the maria ellipsoid: can the mascons have adjusted isostatically since their formation? Systematic differences in height between the western and eastern southern uplands are also noted.


Examination of the Moon through large telescopes reveals a multitude of fine detail down to a scale of 1 km or less. The most prominent feature of the lunar surface is the abundance of circular craters. Many investigators agree that a great majority of these craters have been caused by explosions associated with high velocity impacts. It is further generally assumed that the majority of these high velocity impacts took place during the earliest stages of development of the present Earth-Moon system. The morphology of the Moon surface appears in dynamical considerations in the following way. We know from the work of G. H. Darwin that the Moon has been steadily retreating from the Earth. Dynamical considerations suggest that the period of rotation of the Moon on the average equals its period of revolution about the Earth. Thus when the Moon approaches the Earth, its rotation would be accelerated. Since the Moon, like the Earth, approximates to a fluid body, we should expect that a figure of the Moon would have changed in response to its changing rate of rotation. If the craters formed at a time at which the Moon’s figure was markedly different from the present, then initially circular craters would be deformed and any initially circular depression would tend to change into an elliptically shaped depression, with the major axis of the ellipse along the local meridian. Study of the observed distortions of the craters can give evidence as to the past shape of the Moon, provided the craters formed at a time when the Moon possessed a different surface ellipticity. I should like to examine the limitations the present surface structure places on the past dynamical history of the Moon. I will first review briefly calculations bearing on the dynamical evolution of the Earth-Moon system and the implications these calculations have on the past shape of the lunar surface.


Author(s):  
V.V. Shevchenko

Since the early 1990s, in analytical reviews, experts have increasingly been paying attention to the growing scarcity of rare and rare earth metals (REM) necessary for the development of advanced technologies in modern industry. The volume of the world market has increased over the past 50 years from 5,000 to 125,000 tons per year, which is explained by the extensive use of REM in the rapidly developing areas of industry associated with the advancement of high technology. Unique properties of REM are primarily used in the aerospace and other industrial sectors of the economy, and therefore are strategic materials. For example, platinum is an indispensable element that is used as a catalyst for chemical reactions. No battery can do without platinum. If all the millions of vehicles traveling along our roads installed hybrid batteries, all platinum reserves on Earth would end in the next 15 years! Consumers are interested in six elements known as the platinum group of metals (PGM): iridium (Ir), osmium (Os), palladium (palladium, Pd), rhodium (rhodium, Rh), ruthenium (ruthenium, Ru), and platinum itself. These elements, rare on the Earth, possess unique chemical and physical properties, which makes them vital industrial materials. To solve this problem, projects were proposed for the utilization of the substance of asteroids approaching the Earth. According to modern estimates, the number of known asteroids approaching the Earth reaches more than 9,000. Despite the difficulties of seizing, transporting, and further developing such an object in space, this way of solving the problem seemed technologically feasible and cost-effectively justified. A 10 m iron-nickel asteroid could contain up to 75 tons of rare metals and REM, primarily PGM, equivalent to a commercial price of about $2.8 billion in 2016 prices. However, the utilization of an asteroid substance entering the lunar surface can be technologically simpler and economically more cost-effective. Until now, it was believed that the lunar impact craters do not contain the rocks of the asteroids that formed them, since at high velocities the impactors evaporate during a collision with the lunar surface. According to the latest research, it turned out that at a fall rate of less than 12 km/s falling body (drummer) can partially survive in a mechanically fractured state. Consequently, the number of possible resources present on the lunar surface can be attributed to nickel, cobalt, platinum, and rare metals of asteroid origin. The calculations show that the total mass, for example, of platinum and platinoids on the lunar surface as a result of the fall of asteroids may amount more than 14 million tons. It should be noted that the world’s known reserves of platinum group metals on the Earth are about 80,000 tons.


2020 ◽  
Vol 4 (2) ◽  
pp. 27 ◽  
Author(s):  
Marcel Loewert ◽  
Michael Riedinger ◽  
Peter Pfeifer

Climate change calls for a paradigm shift in the primary energy generation that comes with new challenges to store and transport energy. A decentralization of energy conversion can only be implemented with novel methods in process engineering. In the second part of our work, we took a deeper look into the load flexibility of microstructured Fischer–Tropsch synthesis reactors to elucidate possible limits of dynamic operation. Real data from a 10 kW photovoltaic system is used to calculate a dynamic H2 feed flow, assuming that electrolysis is capable to react on power changes accordingly. The required CO flow for synthesis could either originate from a constantly operated biomass gasification or from a direct air capture that produces CO2; the latter is assumed to be dynamically converted into synthesis gas with additional hydrogen. Thus two cases exist, the input is constantly changing in syngas ratio or flow rate. These input data were used to perform challenging experiments with the pilot scale setup. Both cases were compared. While it appeared that a fluctuating flow rate is tolerable for constant product composition, a coupled temperature-conversion relationship model was developed. It allows keeping the conversion and product distribution constant despite highly dynamic feed flow conditions.


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