Ion cyclotron resonance bridge detector for frequency sweep

An electronic ion cyclotron resonance detection system was designed and constructed. The ions are excited by sweeping the frequency of the electric field (3-300 kHz) using a sweep frequency generator with a nonlinear sweep voltage in order to maintain an approximately constant mass resolution. Ion detection is accomplished by a bridge with a phase-sensitive detector as a demodulator. The required reference signal for the phase-sensitive detector is generated by a circuit with a transfer function which approximates that of the ICR signal in order to obtain an accurate phase match between the signal source and the detector. The device is capable of detecting a minimum concentration of 50 ions/cm³ over a mass range of 15 to 1500 amu.