Performance evaluation of a miniature magnetic sector mass spectrometer onboard a satellite in space.

With the rapid development of space technology in China, it is urgent to use mass spectrometer to detect the space environment. In this work, a space miniature magnetic sector mass spectrometer is evaluated, which consists of three subsystems: (1) physical unit, (2) electric control unit, (3) and high voltage power. It has 90° magnetic sector-field analyzer with double trajectory, in which a trajectory measurement range is from 1 to 12 amu, the other range is from 6 to 90 amu.The mass spectrometer has two work models, one is used to measure space neutral gas when the filament of mass spectrometer ion source turned on, the other is used to measure space charged ions when the filament turned off. The absolute resolution of this device is less than 1 amu, the minimum detectable ion current is about 10-13 A, and the sensitivity is 10-6 A/Pa (N2). Its overall size is 170 mm × 165 mm × 170 mm, its weight is 4.5 kg, and its power consumption is 18 W. A series of environmental adaptability tests, including high and low temperature cycle, shock, vibration, thermal vacuum cycle, were carried out on the ground before launching, and sensitivity and peak position were also calibrated on the ground. In November 2012, the mass spectrometer was carried by an experimental satellite to 499 km sun synchronization and is still working right now. It successfully detected the atmosphere compositions both in the satellite orbit and gas-emitted from satellite, including O, He, 12CO2, 13CO2, H2, N2, O2, H2O, and so on.

[Effect of C/N ratio on nitrite accumulation during denitrification process].

Effect of C/N (COD/NO3(-) -N) ratio on nitrite accumulation during denitrification process was investigated in a sequencing batch reactor (SBR) with acetic sodium as the electron donor. The nitrite accumulation ratio was 45% at a C/N ratio of 3 during operation in SBR with HRT at 6 h. According to the results of batch experiments, Nitrite accumulation ratios were higher at C/N ratios of 2.5 and 3.0, and the values were 47.50% +/- 1.005% and 45.28% +/- 5.469%, respectively. The nitrite specific accumulation rate was (30.17 +/- 1.70) mg x (g x h)(-1) at a C/N ratio of 2.5, and was (29.92 +/- 1.90) mg x (g x h)(-1) at a C/N ratio of 3.0. C/N ratios of 2.5-4.0 did not affect the nitrate reduction rate but obviously affected the nitrite accumulation rate. C/N ratios of 2.5 and 3.0 were favorable for nitrite accumulation, and a C/N ratio > or = 3.5 would lead to decrease in nitrite accumulation (SBR).