H. W. Koch

Scintillation Spectrometers for Measuring the Total Energy of X‐Ray Photons

X‐ray spectrometers are described that operate on the principle of totally absorbing the energy of an individual x‐ray photon in a scintillator. Experiments with scintillators of xylene containing terphenyl, and of sodium iodide activated by thallium, show that detection efficiencies better than 80 percent and energy resolutions better than 10 percent are attainable in the x‐ray energy range from ½ to 50 Mev. Monte Carlo calculations and crude scaling laws that simplify extrapolations to other size scintillators are discussed.

Experimental Depth Dose for 5, 10, 15 and 20-Million-Volt X-Rays

With the 20-million-volt electron beam of good intensity now produced in the University of Illinois betatron, questions about the practical use of high-energy radiations can be examined. The most promising way to use the betatron in therapy would be to send the original electrons accelerated in the vacuum tube directly into the patient. At 20 million volts these electrons will penetrate as far as 10 cm. and no farther. Thus no damage is done to the back of the patient. Furthermore, the ionization should reach a maximum 7 or 8 cm. beyond the entrance surface for the electrons, and the damage could be well localized within the body. About a 25- or 30-million-volt betatron would be ideal for this work, since it has the right energy and a reasonable size. Although a sufficiently intense beam of electrons now comes out of the betatron, it is not yet in a good enough state of collimation or control for practical use. The x-rays produced by this electron stream when it strikes a target cause an ionization intens...

An 80‐Mev Model of a 300‐Mev Betatron

The construction and operation of a flux‐biased 80‐Mev betatron is described. This betatron was built as a model to test design features later to be incorporated in a 300‐Mev betatron. Particular attention is paid to factors influencing design and to considerations of magnetic problems which are common to betatrons and synchrotrons such as the construction of field magnets which are uniform, the testing of fields at injection time, the mechanism of electron capture, and the influence of field inhomogeneities. The dimensions and operating characteristics are included together with many comparisons with the 300‐Mev betatron.

Magnetic Field Calculations for Large Cross‐Section Cloud‐Chamber Coils

A method is described and equations are presented which permit the calculation of the magnetic field characteristics of large cross‐section air core coils. The method is applied to the determination of the field non‐uniformities on the median plane to be expected with annular cloud‐chamber coils of rectangular cross section. The field non‐uniformity results are provided in graph form to facilitate the design of cloud‐chamber coils.

Recollections on Sixty Years of NBS Ionizing Radiation Programs for Energetic X Rays and Electrons.

These recollections are on ionizing radiation programs at the National Bureau of Standards (NBS) that started in 1928 and ended in 1988 when NBS became the National Institute of Standards and Technology (NIST). The independent Council on Ionizing Radiation Measurements and Standards (CIRMS) was formed in 1992. This article focuses on how measurements and standards for x rays, gamma rays, and electrons with energies above 1 MeV began at NBS and how they progressed. It also suggests how the radiation processors of materials and foods, the medical radiographic and radiological industries, and the radiological protection interests of the government (including homeland security) represented in CIRMS can benefit from NIST programs.