A Permanent Magnet β-Ray Spectrograph

The method of design followed in the construction of a permanent magnet containing 450 pounds of red dot Alnico and having a total mass of about 3000 pounds is reviewed. The magnet can produce fields which are permanent and highly homogeneous and of any magnitude up to about 3000 oersteds in a gap $8^{\mathrm{\prime \prime }}{\text{×16}}^{\mathrm{\prime \prime }}\text{×1}{\frac{9}{16}}^{\mathrm{\prime \prime }}$ . The moderate cost and excellent performance of the installation indicate that such magnets should be useful for numerous applications. A photographic type spectrograph is described, which is suitable for the study of internally converted electrons. To render quantitative comparisons of electron intensities feasible, the photographic action of β‐rays has been investigated. Examination of β‐spectra emitted by naturally radioactive elements indicates that the performance of the spectrograph is quite satisfactory.