Standard Rays Research Articles

Study of the effect of photon self-absorption on the detection efficiency of HPGe detector in measurements of an activated uranium sample

The photon self-absorption effect of uranium on the full-energy peak (FEP) efficiency calibration of high purity germanium (HPGe) detector was studied as a function of energy using an activated uranium sample has a thickness of 1 mm. The absolute efficiencies of the detector were obtained with the use of gamma standard sources and gamma rays of radionuclides created by irradiating the uranium sample with secondary neutrons. The measurements were carried out with the use of a Planar HPGe detector. MCNP simulation code was used to verify the experimental results. The comparison of the empirical results with the simulation results showed a good agreement. To interpret the efficiencies, the reaction rates were calculated using two methods: (1) - the use of the efficiency curve from the standard sources combined with the self-absorption correction of the uranium material and (2) - the use of the efficiency curve obtained from gamma rays in the sample.

Boosted Tau Lepton as a Microscope and Macroscope

Anomalies from the LHCb lepton flavour universality and Fermilab muon anomalous magnetic moment show tantalizing hints of possible new physics from the lepton sectors. Due to its large mass and shorter lifetime than muon, the tau lepton is believed to couple more to possible new physics beyond the Standard Model. Traditionally, tau leptons are probed through their decay products due to tau’s short lifetime. On the other hand, at a high energy scale, a large fraction of tau leptons could be boosted to a much longer lifetime and fly a visible distance from several centimetres up to kilometer length scale yet very informative to new physics beyond the standard model or high energy cosmic rays. In this article, we investigate rare, yet promising, tau-physics phenomena, where long-lived taus are exploited either as a microscope (for the measurement of tau’s anomalous magnetic moment to an unprecedented level of accuracy) or as a macroscope (for the detection of 1 TeV to 1 PeV cosmic neutrinos).

Feasibility study of Isfahan MNSR as a calibration thermal neutron source

In the present work, the thermal beam-tube of Isfahan Miniature Neutron Source Reactor (MNSR) with known neutron dose-equivalent rate and flux is investigated as a calibration source of thermal neutrons. It is shown that 90% of the neutrons emerging from this tube are thermal. Measuring the response of TLD-600 and TLD-700 dosimeters exposed to these neutrons reveals that the both dosimeters respond linearly to neutrons in the range of 0.1 to 38 mSv. Moreover, after subtracting the contribution of mixed gamma rays using the calibration curves obtained in a standard 60Co gamma rays field, the response of TLD-600 dosimeter still behaves linearly with dose-equivalent. Finally, it is concluded that the dose-equivalent rate and flux of thermal neutrons in Isfahan MNSR are stable with time and this reactor can reliably be used as a calibration source for thermal neutrons.

Multidimensional Model for Estimating the Error in the Diagnosis of the Organism Elemental Status

The elemental status diagnosis of the body is a medical tool that allows to monitor important vital functions. There are several methods for organizing this diagnosis. This paper considers a new method based on the presentation of diagnostic data in a multidimensional space. Multidimensional space is a convenient mean to represent large amounts of information. The novelty of the approach in this research is based on the fact that the totality of the weight parts of all elements from the periodic table together makes up the weight of a person. In a multidimensional space, organisms with the same weight have the same sum of coordinates and are located on one hyperplane. Since for any norms it is important to have a ratio between the quantities that reflect the content of the elements, a ray becomes the standard for the class, for each point of which the ratio between the coordinates is observed. To compare the methods determination the standard for the class, another multidimensional space is organized, the coordinates of which are the direction cosines of the standard rays. It is shown that in this space the proposed method has an increased accuracy in comparison with the six considered.

Possible breaking of the FIR–radio correlation in tidally interacting galaxies

Far-infrared (FIR)--radio correlation is a well-established empirical connection between continuum radio and dust emission of star-forming galaxies, often used as a tool in determining star-formation rates. Here we expand the point made by Murphy (2013) that in the case of some interacting star-forming galaxies there is a non-thermal emission from the gas bridge in between them, which might cause a dispersion in this correlation. Galactic interactions and mergers have been known to give rise to tidal shocks and disrupt morphologies especially in the smaller of the interacting components. Here we point out that these shocks can also heat the gas and dust and will inevitably accelerate particles and result in a tidal cosmic-ray population in addition to standard galactic cosmic rays in the galaxy itself. This would result in a non-thermal emission not only from the gas bridges of interacting systems, but from interacting galaxies as a whole in general. Thus both tidal heating and additional non-thermal radiation will obviously affect the FIR-radio correlation of these systems, the only question is how much. In this scenario the FIR-radio correlation is not stable in interacting galaxies, but rather evolves as the interaction/merger progresses. To test this hypothesis and probe the possible impact of tidal cosmic ray population we have analyzed a sample of 43 infrared bright star-forming interacting galaxies at different merger stages. We have found that their FIR-radio correlation parameter and radio emission spectral index vary noticeably over different merger stages and behave as it would be expected from our tidal-shock scenario. Important implications of departure of interacting galaxies from the FIR-radio correlation are discussed.

Galactic fly-bys: New source of lithium production

Observations of low-metallicity halo stars have revealed a puzzling result: the abundance of \li7 in these stars is at least three times lower than their predicted primordial abundance. It is unclear whether the cause of this disagreement is a lack of understanding of lithium destruction mechanisms in stars or the non-standard physics behind the Big Bang Nucleosynthesis (BBN). Uncertainties related to the destruction of lithium in stars can be circumvented if lithium abundance is measured in the "pristine" gas of the low metallicity systems. The first measurement in one such system, the Small Magellanic Cloud (SMC), was found to be at the level of the pure expected primordial value, but is on the other hand, just barely consistent with the expected galactic abundance for the system at the SMC metallicity, where important lithium quantity was also produced in interactions of galactic cosmic rays (GCRs) and presents an addition to the already present primordial abundance. Due to the importance of the SMC lithium measurement for the resolution of the lithium problem, we here draw attention to the possibility of another post-BBN production channel of lithium, which could present an important addition to the observed SMC lithium abundance. Besides standard galactic cosmic rays, additional post-BBN production of lithium might come from cosmic rays accelerated in galaxy-galaxy interactions. This might be important for a system such is the SMC, which has experienced galaxy harassment in its history...(abridged)

The Evolution of Galactic Beryllium and Boron Traced by Magnesium and Calcium

ABSTRACTBeryllium and boron abundances are consistently derived on the parameter scale of two recent uniform stellar Mg and Ca abundance studies, one utilizing non‐LTE parameters and abundances, the other assuming LTE. The results are used to explore the BeB‐Mg and BeB‐Ca relations at low metallicity as urged by B. D. Fields and coworkers. The slopes of all logarithmic BeB‐MgCa relations, regardless of light element (Be or B), metallicity tracer (Mg or Ca), or parameter scale (non‐LTE or LTE), are found to lie in the range 1.1–1.3. These results using the α‐elements Mg and Ca confirm the need for a metal‐poor “primary” BeB production mechanism (perhaps in addition to standard Galactic cosmic rays) previously inferred from BeB‐Fe and questioned BeB‐O relations.

Standard cosmic ray energetics and light element production

The recent observations of an approximately linear relationship between both Be and B and iron in metal-poor stars has led to a reassessment of the origin of the light elements in the early Galaxy. In addition to standard secondary production of BeB, it is necessary to introduce a production mechanism which is independent of the interstellar metallicity (primary), and in which freshly synthesized C, O and He are accelerated by supernova shock waves. Primary mechanisms are expected to be dominant at low metallicity. At metallicities higher than , some existing data indicate that secondary production is dominant. In this paper, we focus on the secondary process, related to the standard Galactic cosmic rays, and we examine the cosmic ray energy requirements for both present and past epochs. We find the power input to maintain the present-day Galactic cosmic ray flux is about 1.5 1041 erg/s = 5 1050 erg/century; this estimate includes energy losses from both the escape of high-energy particle and ionization losses from low-energy particles. This implies that, if supernovae are the sites of cosmic ray acceleration, the fraction of explosion energy going to accelerated particles is about ~30% , a value which we obtain consistently both from considering the present cosmic ray flux and confinement and from the present 9Be and 6Li abundances. Using the abundances of 9Be (and 6Li) in metal-poor halo stars, we extend the analysis to show the effect of the interstellar gas mass on the standard Galactic cosmic ray energetic constraints on models of Li, Be, and B evolution. The efficiency of the beryllium production per erg may be enhanced in the past by a factor of about 10; thus the energetic requirement by itself cannot be used to rule out a secondary origin of light elements. Only a clear and indisputable observational determination of the O-Fe relation in the halo will discriminate between the two processes.

Lithium–beryllium–boron: origin and evolution

The origin and evolution of lithium–beryllium–boron is a crossing point between different astrophysical fields: optical and gamma spectroscopy, nonthermal nucleosynthesis, Big Bang and stellar nucleosynthesis and finally galactic evolution. We describe the production and the evolution of lithium–beryllium–boron from Big Bang up to now through (i) the interaction of the Standard Galactic Cosmic Rays with the interstellar medium, (ii) supernova neutrino spallation, and (iii) a low-energy component related to supernova explosions in galactic superbubbles.

Space-time ray method for seismic wave fields

The space-time ray method can be applied to the evaluation and continuation (extrapolation) of the complete seismic wave field in laterally inhomogeneous media with curved interfaces. The wave field propagates along certain space-time curves, called space-time rays. Their space projections correspond to standard rays. Examples of possible applications of the space-time ray method, where the standard ray method fails, are as follows: a) The propagation of seismic waves in slightly dissipative media, b) The computation of seismic wave fields generated by seismic sources with direction-dependent source-time variations. c) Downward continuation of the seismic wave field (actual seismograms) measured at the Earth's surface.

Researches towards establishing a theory of the dispersion of light, No. IV

In his former communications to the Royal Society the author had instituted a comparison of the results of observation and of theory with regard to the dispersion of light, in the instances of the respective indices for the standard rays in fifteen different cases of transparent media; and had found a sufficiently close agreement in the cases which gave the lower numbers; but there yet appeared to be an increasing discrepancy as an advance was made towards the higher. The theoretical formula employed in this investigation was one derived from the undulatory hypothesis, by a process involving some limitations, which rendered it only approximative. By pur­suing the calculations to a greater degree of developement, or by adopting methods of a more precise character, such as those of M. Cauchy and of Mr. Kelland, the author was led to hope that a more close coincidence might be obtained. The formulae of M. Cauchy, however, involved calculations of so elaborate and overwhelming a character, that he was induced to make trial of the method of Mr. Kelland, applying it, in the first instance, to the case of .the most highly dispersive substance, namely, oil of Cassia, in which the greatest discrepancy had before appeared. The object of the present communication is to state the results obtained, together with the necessary data employed in the calculations; and also to elucidate the general method, so as to render it more easily applicable to other cases which may arise in the further prosecution of the determination of specific indices. For this pur­pose a general statement is given of Mr. Kelland’s method, in whose formulae, it is easy, knowing the value of the wave-length in air, and taking the indices as given by observation for that particular medium, to introduce the values of the wave-length in the medium. Two of the constants are then determined for that medium; and by the aid of these, combined with the indices given by observation, a value of the third constant is deduced for each ray: and the veri­fication of the theory will result from the equality of the respective values of this latter constant thus obtained.

Remarks on the theory of the di­spersion of light, as connected with polarization

The present paper is a sequel to those already presented by the author to the Royal Society, in which he had instituted a compari­son of the observations of the refractive indices for the standard rays of light in various media, with the results calculated from theoretical formulæ, deduced from the most improved views of the undulatory hypothesis ; the cases discussed including the greatest range of data as yet furnished by experiment. The comparison exhibited an accordance sufficient to warrant the conclusion that the theory affords a very satisfactory approximation, at least, to the expression and explanation of the actual law of nature. In order, however to remove any possible discrepancy which may still exist, or hereafter be found to obtain, the author considers that farther examination is requisite of the principles on which any extension or modification of the theory might be pursued; and such is the object of the investigation undertaken in the present paper. The phenomena of interference, on which the undulatory theory was originally based by Dr. Young, obliged us to adopt some idea of an alternating motion, as well as a motion of translation, in our conception of light; and this, with all the accessions it has received, especially from the investigation of Fresnel, has, at the present day, been connected by the labours of M. Cauchy and others, with gene­ral dynamical principles, which regulate the propagation of vibratory motions through an elastic medium. From such dynamical prin­ciples there have been deduced certain differential equations of mo­tion, the integration of which gives the well-known expression for a wave, involving the relation between the velocity and the wave­ length which explains the dispersion. The direct and complete in­tegration of these forms, effected by M. Cauchy, and simplified by Mr Tovey and M. Kelland, involves certain conditions; namely, the evanescence of certain terms, the interpretation of which implies peculiar views of the constitution of the ether. Mr. Tovey shows that without these conditions, a certain form of the wave-function is a particular solution of the equations ; and this form is precisely that expressing elliptically polarized light. If the absence of the condition in question be essential to the case of elliptically and cir­cularly polarized light, it follows that all the preceding investiga­tions, which depend on the fulfilment of those conditions, are ap­plicable only to unpolarized and plane-polarized light, and conse­quently the general integration is limited in a most material part of its application; a defect which is only remedied by the supplementary investigation of Mr. Tovey, in which, for this case, a particular solution is assigned. It seemed, then, necessary to show explicitly that the non-fulfilment of the conditions, that is, the non-evanescence of the terms in question, is essential for elliptically polarized light, as their evanescence is for common light, and thus to exhibit distinctly the relation between the cases of elliptically polarized, of plane-polarized, and unpolarized light; and, again, to remove, if possible, the obscurity and discrepancy of opinion in which the phy­sical interpretation of those conditions, with regard to the supposed constitution of the ethereal medium, appeared to be involved.

IV. Researches towards establishing a theory of the dispersion of light. No. IV

Introductory Remarks . In my last communication I laid before the Royal Society a comparison of the results of observation and of theory, with respect to the dispersion of light, in the instances of the refractive indices for the standard rays in fifteen different cases of transparent media (some being the same medium at different temperatures), including those which exhibit the greatest range, and the highest numbers, of any yet subjected to this kind of observation. The agreement with the theory was found to be sufficiently close for the lower cases, but displayed an increasing discrepancy as we advanced towards the higher. The theoretical formula employed was one derived from the undulatory hypothesis, by a process involving some limitations, which rendered it only approximative; and, in conclusion, I remarked that by pursuing the investigation to a greater degree of development, or by adopting methods of a more precise character, it was still reasonably to be hoped that a more close coincidence might be found. I alluded specifically to the methods of M. Cauchy and of Mr. Kelland, as those to which we might look for the means of following up the inquiry with good prospect of success. Of the former (delivered in the Nouveaux Exercices de Mathématiques, Prague, 1835-6, and extending through livraisons 1 to 8 inclusive), I can only say that the investigations are of so extremely elaborate a character, that I was glad, in the first instance at least, to try any other method which might seem to promise results without involving calculations of such overwhelming extent as those by which the distinguished author establishes the exact agreement with theory of all the indices observed by Fraunhofer.

XII. Remarks on the theory of the dispersion of light, as connected with polarization

(1.) In the course of four successive papers, I have laid before the Royal Society the comparison of observations of the refractive indices for the standard rays in various media, with the results calculated from the formula of theory, as deduced upon the most improved views of the hypothesis of undulations; the cases discussed including the greatest range of data which experiment has yet furnished. The degree of accordance thus exhibited between observation and theory, even in the most extreme case, I believe will now be considered sufficient to warrant the conclusion, that the theory at least affords a very satisfactory approximation to the expression and explanation of the actual law of nature; and this in the instance of a class of phenomena which it had long been the reproach of that theory to be supposed incapable of accounting for, if they were not absolutely contradictory to it. At any rate, if, in the instances referred to, the discrepancies should by any be thought still too great, or if it should be contended that other cases may yet arise in which theory may be put to a severer test, yet, with so strong a presumption in its favour, the only fair inference would be, that further examination was required of the principles on which any extension or modification of the theory might be pursued.

Researches towards establishing a theory of the dispersion of light, No. II

The author, in a preceding paper, published in the last part of the Philosophical Transactions, commenced a comparison between the results of M. Cauchy’s system of undulations, expressing the theoretical refractive index for each of the standard rays of the spectrum, and the corresponding index found from observation in different media. Since that paper was communicated, he has received the account of a new series of results obtained by M. Rudberg, and comprising the indices for the standard rays in a prism of calcareous spar, and in a prism of quartz, both for the ordinary and the extraordinary rays; and also the ratios of the velocities in the direction of the three axes of elasticity, respectively, in Aragonite and Topaz. The author was accordingly led to examine this valuable series of data, and the comparison of them with the theory forms the subject of the present paper. He finds the coincidences of theory and observation to be at least as close as those already obtained from Frauenhofer’s results, and to afford a satisfactory extension of the theory to ten new cases, in addition to those already discussed; and a further confirmation of the law assigned by the hypothesis of undulations.

II. Researches towards establishing a theory of the dispersion of light

In my paper inserted in the last part of the Philosophical Transactions, I have commenced a comparison between the results of M. Cauchy’s system of undulations, expressing the theoretical refractive index for each of the standard rays of the spectrum, and the corresponding index found from observation in different media. This comparison is there carried on for all the results obtained by M. Fraunhofer. But these include only a limited range of transparent bodies; and close as is the accordance in these instances, the theory cannot be considered as fully verified, until we shall have extended a similar examination to a greater number of media, and especially to those of higher dispersive power. In this research I am now engaged: but as it will necessarily occupy a considerable period to carry it on, from time to time, as data are furnished, I venture for the present to submit to the Royal Society the following portion of my calculations in continuation of the preceding. In my former communication I had referred to M. Fraunhofer’s results as affording the only precise data which observation had as yet furnished. But through the kindness of Prof. Miller, of Cambridge, I have since become acquainted with the series of results obtained by M. Rudberg. They are given in Poggendorff’s Annalen, band xiv. and xvii., and comprise the indices observed by him for the standard rays, or the ratios of the velocities in air to the velocities within the crystal, in a direction perpendicular to the axis of the rhombohedron, in a prism of calcareous spar, having its edge parallel to that axis; and in a prism of quartz similarly cut; in either case, both for the ordinary and extraordinary ray: also the ratios of the velocities in the direction of the three axes of elasticity respectively, in aragonite and topaz.