Exposition

Radio frequency coils

Exhibit no. 798

The RF coil is a part of the electronics used to generate radiofrequency for multipole ion guides or ion traps. The typical RF system uses a low power oscillator, boosted by several amplifier stages. 

The oscillator is an LC-resonant circuit consisting of a coil (inductor) and a capacitor. The coils are constructed of a relatively large diameter copper wire (1-2 mm), wound on plastic coil forms, with coil diameters of several centimeters. The coil support prevents changing of the coil shape with temperature and thus prevents the frequency change.

This exhibit is a pair of RF coils from an RF amplifier, which supplied the radiofrequency component of the voltage to the quadrupole mass filter of 5972 mass spectrometry detector (Hewlett-Packard, 1993). The RF amplifier had three main parts: RF modulator, RF transformer and RF detector. The RF modulator generated a 1 MHz square wave with the amplitude 0 to +11 V. The output of the RF modulator drove the primary winding of the RF transformer. Its secondary winding consisted of two adjustable coils (the exhibit), which together with the quadrupole capacitance formed a resonant circuit. The HP SERIES 5972 MSD was a quadrupole mass spectrometer with electron ionization designed for use with a capillary gas chromatograph (GC/MS).

Wikipedia: LC circuit
Wikipedia: Radio frequency

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