Publisher Summary This chapter describes the general theory, apparatus, and uses of the modern mass spectroscopy. Mass spectrographs and mass spectrometers are electronic instruments, which analyze substances according to the mass of the constituent elements and molecules present. The mass spectrograph is employed for determining what masses are present or to determine mass defects, while the mass spectrometer is used to measure the relative abundances of the different components in the mass spectrum. A number of physical arrangements have been used by the different workers in the field of mass spectroscopy to solve different problems. Direction focusing magnetic analyzers are the simplest mass analyzers used in modern mass spectroscopy. It is the ion detector which determines whether any particular analyzer is a mass spectrometer or a mass spectrograph. The first problem to which the mass spectrograph was applied was that of identifying the isotopic composition of the elements. The second major application of the mass spectroscope was the problem of determining the isotopic composition of the elements. The third important task to which the mass spectrograph was put was that of determining the exact masses of the isotopes.

Modern Mass Spectroscopy

Historically, vacuum technology has played an important part in the development of electron tubes. The operating characteristics of many early devices were dependent on the degree of vacuum obtained. The Roentgen X-ray tube and the Braun cathode-ray tube are examples of these. Improvement in vacuum technology made possible the development of many truly high-vacuum devices in which performance is independent of the inclosed gas pressure. Many modem electronic components no longer operate in a vacuum but are dependent on vacuum technology in their fabrication. These include microminiature circuit elements, cryotrons, photoconductor-electroluminescent devices and ferromagnetic memory systems-all dependent on vacuum evaporated films. Electronic components have also played an important part in the development of modem vacuum technology. These include thermistor gauges, electronic ionization gauges, ion pumps and electronic leak-detection equipment. This paper is devoted to a review of modem ultra-high vacuum systems and the electronic components used in them.

The Interplay of Electronics and Vacuum Technology

Low Temperature Gasket

The principles involved in the transfer of low boiling liquids under their own vapor pressures are indicated and calculations are presented for the specific case of the transfer of liquid nitrogen. A convenient device for transferring liquid nitrogen by this procedure is described and its operating characteristics are compared with the calculations.

A transfer device for low boiling liquids.

Leak detection practice with particular reference to the hydrogen palladium method

An instrument is described which is capable of measuring one part of helium in 400,000 parts of other gases. The instrument is built around a 180° type mass spectrometer tube which is prefocused for helium ions. Use is made of this high sensitivity tube to locate leaks in vacuum equipment. The leaky container can be connected and evacuated by the pumps in the unit. A fine stream of helium played over the surface of the container will enter the leak and register immediately on the output meter. Very small leaks can be located easily to within a quarter of an inch. The unit is completely self‐contained, requiring only a line connection to a 110‐volt a.c. outlet.

J. A. Hipple

Papers

A Mass Spectrometer Type of Leak Detector