Development of a Miniaturized Ratio Frequency Power for Quadrupole Mass SpectrometerL

Mass spectrometer is a scientific instrument used to analyze and detect. It is widely used in scientific research fields such as physics, chemistry, geology, astronomy, etc. Most of the mass spectrometers on the market are very expensive, cumbersome and inconvenient. Quadrupole mass spectrometer selects the specific ions by the varying electric field and the different charge-to-mass between multiple ions. And because of the magnetic field constraints are not required, quadrupole mass spectrometer can be miniaturized. The miniaturized experimental equipment can be applied in the non-laboratory environment or the space science satellite. Quadrupole structure can be driven by radio frequency (RF) signals which are composed of two sets of high voltage and high frequency signals. These signals produce an alternating electric field in the quadrupole. According to the demand of miniaturized quadrupole spectrometer, an RF power supply was developed. The power supply was composed of modulation module, amplifier circuit module, feedback module, and DC module. In addition, a small transformer with specially design was used to generate high voltage. The skeleton of the transformer was PTFE whose diameter and length were 40 mm, 100 mm respectively. The amplitude signal and the sine signal were multiplied in the modulation module. An op-amp structure which could amplify signals from 0 V to the maximum with a linear envelope was used in the circuit. The feedback circuit module was used to adjust the waveform of output signals and reduced the error of the UV ratio. In a test, the power supply could output an adjustable amplitude RF high-voltage that the peak-to-peak voltage was up to 3.33 kV and the switch time was less than 1 ms. The power supply drove the quadrupole structure under the input condition of a resonant frequency of 1.33 MHz which could be changed by the input port and the scanning frequency of 10 Hz. The output of the RF power supply was observed by an oscilloscope (Tektronix-MDO3024) with a dedicated probe (Tektronix-P6015A). The RF power supply has good working stability and small interference. According to the data analysis obtained from the oscilloscope, the error of the UV ratio of the power supply is about 0.1% and the power supply can work reliably for a long time. Compared with traditional power supply, the instrument has a higher scanning range, smaller size, and lower power consumption, which is 35 W. In general, the design has high practical value and meets design requirements.