A Recording Unit and Electronic Shunt Selector for a Mass Spectrometer

Abstract

A direct action shunt selector has been designed that pre-selects the appropriate shunt so that widely different mass spectrometer ion currents can be recorded linearly on a standard chart. In conjunction with a linear direct current amplifier and a Leeds and Northrup Speedomax pen recorder, this unit allows rapid and accurate recording of a given mass spectrum, which can be scanned by varying either the magnetic field or the ion accelerating potential of the mass spectrometer. When used with a 180° Nier type mass spectrometer with well stabilized circuits, a precision of ± 0.2% in measuring the ratio of [Formula: see text] and [Formula: see text] was obtained. Also, samples of xenon were investigated and the abundances of the isotopes determined.

The Isotopic Constitution of Germanium

“…A 180-degree direction focusing mass spectrometer was used (18). The relative ion currents were measured with a linear inverse feedback amplifier coupled to a Leeds and Northrup Speedomax recorder (15). The bombarding electrons were accelerated through a constant potential, the value of which was approximately 85 v. The accelerating potential for the ions so formed was maintained constant a t 1500 v. and the spectrograms were recorded using magnetic scanning.…”

Automatic Operations in Quantitative Analysis

“…Use of magnetism as a separative force (4-58) is made mainly in the so-called mass spectra procedures (53,87,102,378,415,437,441)• The separation is attained by ionizing the gas by electron bombardment, accelerating and focusing the ions by an electrostatic field, and then deflecting them in a magnetic field. The separation of the ions according to their masses is thus accomplished and abundance measurements are then made electrically (320) or photographically. One process control spectrometer (175, 293) programs a series of eight accelerating voltages corresponding to specific preset masses to be separated.…”

Mass Spectrometry

“…The four-element oscillograph (16.9) has been the most widely used recording method. The range limitation of the single element pen-and-ink recorder has been circumvented by the use of an automatic scale expander (55) with some modifications (37,92).…”

“…Research on the theoretical and experimental aspects of electron-gun (50, 91) and eiecton-lens (13, 25, 40,41,43,89,92,100,101,106,110,114,187,142,149,157,158) design continues. To many practical electron microscopists, this work appears to be of little interest.…”