A marginal oscillator detector for ion cyclotron resonance spectrometers

Abstract

Design, construction, and performance of a solid state marginal oscillator for detection of ions in ion cyclotron resonance experiments are described. Special design features include noise matching a high Q tank to an FET preamplifier which sacrifices voltage level for improved S/N ratio, amplitude limiting to remove noise from the feedback signal, and impedance matching the feedback resistor to the tank to minimize phase shift, parasitic capacitive coupling, and tank loading. A simple electrical circuit which simulates power absorption by ions for performance testing and comparison among marginal oscillators for icr applications is also described.

Mechanism of low-pressure chemical ionization mass spectrometry

“…In addition, voltages applied to the upper and lower plates of the cell cause the ions to drift slowly from the source region into the analyzer region where an alternating electric field at frequency is provided by a marginal oscillator (14,15). The mass resolution of this analyzer cell has been shown to be limited primarily by two factors: (1) pressure broadening of the peaks due to the ion-molecule collisions and (2) the limited time for drift of the ions through the analyzer region and into the total ion current region (16).…”

Deep‐level transient conductance spectroscopy of high resistivity semiconductors

“…Alternatively, although possibly less flexible in approach, the sensitivity test circuit described by Warnick et al [9], in which a FET is used to switch resistance electronically across the tank circuit, could be used. In both calibration systems, a more direct measure of sensitivity could be obtained by observing, as it appears on the oscillator radiofrequency output, the demodulated amplified conductance signal rather than the low-level modulating conductance signal, which is difficult to measure.…”

“…The development by Robinson [7] of an amplitude-limiting oscillator having low noise and stable characteristics is of particular note as most later designs have been based on that principle [8,9]. However, several MOD circuits using simple single or dual stage oscillators have also been described, mostly using field-effect transistors as low-noise, positive-feedback amplifiers [10][11][12] For this work, we chose to use the modified Franklin oscillator design described by Idione and Brandenberger [10] and shown in Fig.…”