Angle Of Scatter Research Articles

The interactions of π−-mesons with complex nuclei in the energy range (100–800) MeV. I: The interaction lengths and elastic scattering of 88 MeV π−-mesons in G5 emulsion

Abstract A block of emulsion has been exposed to the 96 MEV π−-meson beam of the Liverpool synchrotron and 92·5 m of track have been scanned in the region where the mean energy is 88 MEV. After correction for beam contamination, the interaction lengths for the production of inelastic events and for elastic scatters with projected angle of scatter ≥ 8° are (20·4±1·1) cm and (32·3± 2·1) cm respectively. The geometrical interaction length is 29·3 cm. With the optical model of the nucleus, the absorption coefficient is found to be K = (4·0+2·5 −0·75) 1012cm−1, and the change in wave number is given by ki = − (1·86±0·20) 1012cm−1. This absorption coefficient corresponds to a mean free path in nuclear matter λn = (2·5+0·5 −0·7) 10−13 cm, to an imaginary component of potential Vi = − (32+2 −6) MEV, and with the value of the change in wave number to a real potential Vr = −(28±3) MEV.

Scattering at oblique incidence from ionospheric irregularities(Abstract)

THE PURPOSE of this paper is to supply a review of the experimental investigations conducted by a research group at the National Bureau of Standards on the subject of oblique incidence ionospheric scatter at very high frequencies. Emphasis is placed on the results which contribute to further understanding of the behavior of the scattered signals and the physics of the ionosphere. The main topics discussed are long- and short-term characteristics of scattered signals. Included under the latter are the results of simultaneous observations at closely spaced receiving points. Next experimental techniques are discussed from which the heights of the ionospheric irregularities can be deduced and results of their use at different seasons and times of day are given. It is found that all the scatter which could be observed with the available techniques resulted from irregularities in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> region of the ionosphere, and most of it came from the lower parts of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> region. The following section deals with the dependence of the scattering on frequency; a range of frequencies from 27.775 mc to 107.8 mc is examined. The main part of the report concludes with the results of an experiment which gave information on the dependence of ionospheric scatter on the angle of scatter. A final section reviews the results of some simultaneous observations in Alaska dealing with the characteristics of ionospheric scattering in the auroral zone. This section emphasizes the different and new results from the Arctic.

Cobalt 60 protection design.

The recent report by the National Committee on Radiation Protection, published as Bureau of Standards Handbook 54 (1) includes basic information on cobalt 60 teletherapy shielding. So far as experimental attenuation data for the primary and 90° scattered radiation are concerned, the Handbook is particularly complete; data based on experience with completed installations, however, are limited, since cobalt teletherapy is a rather recent development. It is the purpose of the present report to give this supplementary information. The study includes surveys of completed installations, the design of which was based on experimental attenuation measurements (2–4). In Figure 1 are shown schematically the three types of radiation which should be considered in protection design; the useful beam, scattered radiation, and leakage radiation. Since the intensity and energy of the scattered radiation vary with angle of scatter, size of field, etc., its attenuation presents the more difficult problem. The structural shielding requirements of teletherapy installations vary widely and depend on a number of factors, the most important of which are as follows: 1. Degree of occupancy of nearby regions. 2. Orientation of useful beam. 3. Type of equipment. 4. Weekly work load in r/week at 1 meter (in air). 1. Degree of Occupancy: Handbook 54 is the first protection code to give occupancy factors for areas of various types. This permits the designer to adjust the barrier thickness to meet actual requirements. A stairway, for instance, is assumed to be occupied not more than one-sixteenth of the time by the same personnel. Since an occupancy factor of 1/16 reduces the required thickness by four half-value layers, a primary concrete barrier is reduced by 10 inches. It is obvious, therefore, that significant savings can be gained by proper location of the teletherapy room with respect to occupancy of surrounding regions and by orientation of the equipment so that the beam is directed toward an outside wall. Where there is a possibility of a future increase in the degree of occupancy, it is more economical to provide for this originally. A corner room on the bottom floor, preferably below ground, usually requires minimum shielding. This does not necessarily mean minimum expense, since excavation may cost more than the required additional shielding. In some instances, it is more practical to locate the telecobalt room on an upper floor in order that it be close to existing x-ray therapy facilities. In such cases efficient shielding design is essential. This is not merely a matter of cost. Often the weight of the shielding determines whether an upper-floor location is feasible. 2. Orientation of Useful Beam: The most effective way of reducing the shielding cost and weight is by limiting orientation of the useful beam to actual requirements. Such restriction permits the use of secondary barriers of less thickness for all areas exposed only to scattered and leakage radiation.

The Differential Cross Section for High Energy Nucleon-Nucleon Collisions and the Mean Square Angle of Scatter

In an attempt to account theoretically for the lateral and angular development of the penetrating particles in high energy cosmic-ray showers, we have developed a method for deriving the differential from the total cross section, in the laboratory frame of reference. An integral equation is set up for the differential cross section, and solved assuming that the differential cross section in the centre-of-mass frame of reference is of the form R+S' cos2 θ, where R and S' are functions of the incident and scattered energies only. Using a form of the total cross section derived from the analysis of high-energy cosmic-ray experiments, the mean square angle of scatter in a nucleon-nucleon collision has been calculated and found to be inversely proportional to the energy of the incident particle. The results are compared with experiments.