A miniature reflectron time-of-flight mass spectrometer (TOF MS) with orthogonal extraction coupled with electron impact (EI) ionization source can be used to perform in situ gas composition analysis in a planetary environment. However, performances such as the mass resolution, sensitivity, limit of detection, mass range, and mass accuracy are often decreased because of miniaturization. Herein, a compact instrument for space applications has been developed, and its performance has been evaluated. The mass of the TOF MS is 13.4 kg, with dimensions of 300 mm × 200 mm × 200 mm, and the power consumption is 25 W. In this paper, the design of the ion source, mass analyzer, and detector is discussed in detail. The upper limit of the mass range is greater than 500 amu, and the best resolving power obtained so far on the miniature TOF MS is around 405 at full width half maximum (FWHM); other performance indexes of the instrument are also determined, where the worst case for mass stability is 0.49%, together with a mass accuracy of 0.12% and a sensitivity of 0.6 mV/ppm.

This work reports on the complete design and the properties of an ionization gauge based on a carbon nanotube cathode, which can measure ultrahigh vacuum without thermal effects. The gauge is composed of a pressure sensor and an electronic controller. This pressure sensor is constructed based on a hot-cathode ionization gauge, where the traditional hot filament is replaced by an electron source prepared with multi-wall nanotubes. Besides, an electronic controller was developed for bias voltage supply, low current detection, and pressure indication. The gauge was calibrated in the pressure range of 10 to 10 Pa in a XHV/UHV calibration apparatus. The gauge shows good linear characteristics in different gases. The calibrated sensitivity is 0.035 Pa in N, and the standard deviation of the sensitivity is about 1.1%. In addition, the stability of the sensitivity was learned in a long period. The standard deviation of the sensitivity factor "S" during one year is 2.0% for Ar and 1.6% for N.

The main factor that affects the extension of the lower limit of a constant conductance gas flowmeter is the outgassing of the inner surface of the ballast chamber and pipes. A novel method is demonstrated to extend the lower limit using a non-evaporable getter (NEG) pump to eliminate the outgassing influence. The NEG pump has two remarkable characteristics: one is the large pumping speed for active gases especially for hydrogen at ambient temperature, and the other is no pumping speed for inert gases. It is known from numerous experimental investigations on outgassing that the residual gas inside an ultrahigh vacuum and extremely high vacuum (UHV/XHV) facility made of stainless steel is virtually pure hydrogen. So it can reduce the outgassing influence and maintain a low base pressure without changing the test gas quantity in the ballast chamber when inert gas is used as the test gas. By this method, the lower limit of the constant conductance gas flowmeter is successfully extended to 10 −12 Pa m 3 s −1 (at 23 • C) with a combined relative standard uncertainty of 0.94% (k = 1). A vacuum leak with a leak rate of 10 −10 Pa m 3 s −1 (at 23 • C) is calibrated, and the uncertainty of the non-linearity of a quadrupole mass spectrometer is avoided. An ionization gauge is calibrated in the pressure range from 10 −10 Pa to 10 −6 Pa with the dynamic expansion method, and the uncertainty of conductance ratio is avoided compared with the separated flow method.

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