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An experimental and theoretical study of the energy absorption from high voltage radiation by means of ionization measurements with an extrapolation type chamber.

机译：通过外推型腔室的电离测量，对高压辐射的能量吸收进行实验和理论研究。

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摘要

This experimental and theoretical study aims at further investigation, by means of an extrapolation type of ionization chamber, of the ionization measurement of energy absorption from high-voltage radiations within a medium. Wavelengths ranging between 0.08 and 0.5 A0 were used. The walls of the ionization chamber were made of simple elements (graphite, aluminium and copper) or pressed bakelite - graphite mixtures which were loaded with cerium oxide in order to control the effective atomic number of the mixtures. A distinct advantage of the experimental arrangement used is the possibility of measuring the ionization per unit spacing when the air space is vanishingly small which thus eliminates the variable effects of chamber size. The results of earlier workers with chambers of fixed finite dimensions have been difficult to interpret in terms of theoretical considerations because of these effects. Furthermore, by varying the thickness of the upper plane electrode of the chamber, correction could be made for absorption of radiation in this electrode, which, at long wavelengths, maybe considerable in the media of higher atomic number. The results obtained with a chamber of graphite walls show that graphite behaves approximately as air walled material, the ionization per unit volume is constant i.e. the ionization I0 being proportional to V where V is the air volume. With walls of atomic number greater than that of air the ionization per unit spacing increases slightly as the spacing decreases up to a certain threshold spacing blow which it increases very rapidly. The ionization per unit spacing and the threshold spacing both depends upon the material of the electrodes and the wavelength of the radiation. The ionization per unit spacing at zero dimensions may be measured in two ways. Firstly, by drawing at the origin a tangent to the ionization - spacing curve and secondly by extrapolation to zero dimensions of the ionization per unit spacing - spacing curve. It was thus possible to compare these experimental observations with expectations based upon the Bragg -Gray theory of ionization within a cavity. This comparison suggests that the Bragg - Gray theory may be regarded as a satisfactory description of the facts for the range of wavelengths studied, at least for elements of atomic number up to that of aluminium (Z = 13). For copper (Z = 29) and the mixtures (depending upon the electron emission from Ce of Z = 58) the experimental results disagree with the theory except for the shortest wavelengths, and the disagreement increases with increase of wavelength. Suggestions are advanced and a modification made to Gray's equation in an attempt to correct for this disagreement. These are based upon a consideration of the sources and the energy of the photoelectrons omitted from the wall materials.
机译：这项实验和理论研究旨在通过外推型电离室进一步研究介质中高压辐射的能量吸收的电离测量。使用的波长在0.08至0.5 A0之间。电离室的壁是由简单的元素（石墨，铝和铜）或压制的电木-石墨混合物制成的，这些混合物中装有氧化铈，以控制混合物的有效原子序数。所使用的实验装置的显着优点是，当空气空间逐渐减小时，可以测量每单位间距的电离，从而消除了腔室尺寸的可变影响。由于这些影响，很难从理论上解释具有固定有限尺寸腔室的早期工人的结果。此外，通过改变腔室的上平面电极的厚度，可以对该电极中的辐射吸收进行校正，该辐射在长波长下在较高原子序数的介质中可能相当可观。用石墨壁腔室获得的结果表明，石墨的行为大致类似于空气壁材料，单位体积的电离常数是恒定的，即，电离I0与V成正比，其中V是空气体积。当原子序数的壁大于空气的原子序数时，每单位间距的电离会随着间距的减小而略微增加，直至达到某个阈值间距，然后它会迅速增加。每单位间距的电离和阈值间距均取决于电极的材料和辐射的波长。零尺寸处的每单位间距的电离可以两种方式测量。首先，通过在原点绘制与电离-间隔曲线的切线，然后通过外推至单位间距-间隔曲线的电离的零维。因此，有可能将这些实验观察结果与基于腔内电离的布拉格-格雷理论的期望值进行比较。这种比较表明，布拉格-格雷理论可以被视为对所研究的波长范围的事实的令人满意的描述，至少对于原子序数最高的元素是铝（Z = 13）。对于铜（Z = 29）和其混合物（取决于Z = 58的Ce的电子发射），除了最短的波长外，实验结果与理论不一致，并且随着波长的增加，该分歧增加。提出了一些建议，并对Gray方程进行了修改，以纠正这种分歧。这些是基于对壁材料中省略的光电子的源和能量的考虑。

著录项

  • 作者

    Ibrahim, Aly Abdel Kerim.;

  • 作者单位

    University of London, Bedford College (United Kingdom).;

  • 授予单位 University of London, Bedford College (United Kingdom).;
  • 学科 Nuclear physics and radiation.
  • 学位 Ph.D.
  • 年度 1950
  • 页码 195 p.
  • 总页数 195
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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