Attenuation Thickness Research Articles

Test cassette for measuring peak tube potential of diagnostic x-ray machines.

A test cassette employing a modification of the Ardran-Crooks attenuation technique for measuring peak tube potential (and half-value layer) is described. The technique employs a radiographic intensifying screen which is exposed to a hardened x-ray beam. Copper penetrameters are used to determine the attenuator thickness which reduces the light output from the screen to that transmitted by an optical attenuator over an adjacent area of the screen. The test cassette was calibrated by using x-ray machines whose high voltages were measured electrically. The test cassette has a measurement precision of +/- 1 kVp and an accuracy of +/- 3 kVp or better in the range 50-130 kVp for x-ray generators with the same voltage waveform.

Studies on the Attenuation of Quasi Millimeter Wave on a Rain and Snow Covered Radome

The quasi millimeter wave performance suffers degradation under rain, due to the high loss tangent of water in the quasi millimeter wave region. This effect cannot be theoretically estimated due to the complex nature of water flow on the radome surface. The above special effect is observed also in the case of snow-covered surface of the dome.In order to ascertain the above-mentioned effect, some model tests were performed. The main results are summarized as follows : (1) Laboratory tests on the effects of water accretion on the radome surfaceThe surface area of the radome used in this experiment is 50cm×50cm, and the frequency used is 24 GHz. It is found that attenuation factor vs. thickness of water film becomes about 18dB/mm. And attenuation factor vs. area percentage of stringy flow of running water is correlative.(2) Field tests on the effects of snow accretion on the practical radome surfaceThe aperture size of the practical radome used in this experiment is 3.3 meters, and this radome is made of dielectric plates (laminated polyester resin reinforced with glass fiber).Diurnal variations of snow accretion on the above radome were observed in the winter of 1973. The maximum thickness of accreted snow layer was about 60 cm. The condition of snow accretion varied quickly over a wide range chiefly with air temperature, especially above 0°C, and with weather conditions (sunny or shaded sides of the radome).

Measurements of 6 MV x rays. II. Characteristics of secondary radiation.

Abstract The measurements reported are for secondary radiation scattered from either a Presdwood phantom or a concrete barrier. The magnitude, angular distribution and attenuation characteristics of these secondary radiations are discussed. The relative dose from radiation scattered by a Presdwood phantom was evaluated at 1 m from the phantom. Expressed as a percentage of the dose at the centre of the phantom it varied from 0·04 per cent at 135 deg. to 0·8 per cent at 15 deg. Expressed as a tenth-value thickness the attenuation thickness for this scattered radiation in concrete varied from 14·7 cm at 135 deg. to 33·3 cm at 15 deg. The attenuation of 90 deg. scatter was also investigated for Presdwood, steel and lead. The 90 deg. scatter has a monochromatic equivalent energy of slightly less than 500 keV. The intensity and angular distribution of scatter from a concrete barrier was examined for both 90 and 60 deg. incidence of the primary beam. For these measurements the scattered dose at 1 m did not excee...

Application of the entropy method to investigation of transonic adiabatic flows

An entropy method is presented for determining energy dissipation in a moving fluid. Methods for calculation of a transonic adiabatic flow are given. Comparison between the theoretical and experimental results shows that the assumptions, being the basis of the theory, are well confirmed in a transonic flow region. The effect of turbulence attenuation during transition through the velocity of sound is noted and discussed. The methods for determining the thickness of the attenuation thickness according to data from single-dimensional blow-down testing are considered.