An ionization gauge for ultrahigh vacuum measurement based on a carbon nanotube cathode

Abstract

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.

A Cylindrical Triode Ultrahigh Vacuum Ionization Gauge with a Carbon Nanotube Cathode

“…In this work, as mentioned above, the anode current was about 20 μA, only one-fiftieth times lower than that for the cylindrical triode hot cathode ionization gauge, which is conducive to greatly reducing the X-ray photocurrent, and is thus beneficial for obtaining lower limits of pressure measurements for the present gauge. The sensitivity values of the ionization gauge, derived from the slopes of the linear regions in Figure 5 , were ~0.05 Pa −1 for nitrogen, ~0.06 Pa −1 for argon, and ~0.04 Pa −1 for air, which are even slightly higher than that of the most prevalent CNT cathode extractor gauge [ 8 , 11 , 12 , 17 ] and BAG [ 16 ], and are acceptable values for extremely low pressure measurements [ 7 ]. The detailed variation of sensitivity of this ionization gauge will be further discussed below.…”

“…Thus, the metrological behaviors of the modified ionization gauge with a CNT electron source were investigated under a low anode current together with constant electrode voltages, as demonstrated in Figure 1 b. In this situation, the anode current was only about 20 μA, which is high enough for extremely low pressure measurement, according to our previous experience [ 11 , 14 , 17 ].…”

“…However, conventional ionization gauges have long-standing intractable problems when measuring extremely low pressure, i.e., X-ray effects, electron-stimulated desorption effects, and outgassing effects [ 1 , 6 , 7 ]. Fortunately, recent studies [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ] have shown that ionization gauges with carbon nanotube (CNT) cathodes have unique advantages, such as low power consumption for electron emissions, fast responses, free from visible to infrared light radiation and thermal radiation, etc., in extremely low pressure measurements, which are largely due to the application of the novel CNT field emission cathode. For instance, Murakami et al [ 9 ] reported the application of a CNT field emission cathode in a Bayard–Alpert gauge (BAG) for the first time in 2001, and the lower limit of pressure measurement by this novel sensor was approximately 1 × 10 −4 Pa. Dong et al [ 8 ] reported on the design and investigation of a commercial extractor gauge (Leybold, IE 514) with a CNT cathode, which showed excellent measurement linearity from 10 −10 to 10 −6 Torr in nitrogen.…”

Applications of Vacuum Measurement Technology in China’s Space Programs

“…Efforts have also been made for the measurement of total pressure in LIP. Since 2013, we have carried out theoretical and experimental research on carbon nanotube (CNT) cathode ionization gauge cooperated with Lanzhou University, Wenzhou University, and Bern University of Switzerland [13][14][15][16][17][18][19][20][21][22]. First, we established a three-dimensional physical model of CNT ionization gauge and used SIMION software to simulate the influence of electrode voltage, gate structure, and physical transmittance, etc.…”

“…Second, preparation process of CNTs with enhanced performance was developed: uniform and vertical multiwall CNTs were prepared by anodic alumina template method and deposition catalyst method to improve field emission performance [14,15]; free distribution CNTs were directly grew and prepared by oxidation-reduction method to improve emission current density and stability [16,17]. Third, a series of CNT cathode ionization gauges, such as Bayard-Alpert type, separation type, and spherical oscillator type, have been developed based on the abovementioned works [18][19][20][21][22] as shown in Figure 1. Among them, the separation-type CNT cathode ionization gauge has reached the best level reported at present.…”