Nude Gauge Research Articles

Detection of volatiles undergoing sublimation from 67P/Churyumov-Gerasimenko coma particles using ROSINA/COPS

Context. In an earlier study, we reported that the ram gauge of the COmet Pressure Sensor (COPS), one of the three instruments of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA), could be used to obtain information about the sublimating content of icy particles, made up of volatiles and conceivably refractories coming from comet 67P/Churyumov-Gerasimenko. Aims. In this work, we extend the investigation to the second COPS gauge, the nude gauge. In particular, we analyse the volume of the volatile content of coma particles, along with a search for possible dependencies between the nude gauge detection rate (i.e. the rate at which icy particles are detected by the nude gauge) and the position of the Rosetta spacecraft. We also investigate the correlations of the nude gauge detection rate with the quantities associated with cometary activity. Methods. We inspected the density measurements made by the nude gauge for features attributable to the presence of icy particles inside the instrument. These data were then analysed statistically based on the amplitude of the feature and on the position of the spacecraft at the time of detection. Results. Although it was not originally designed for such a purpose, the COPS nude gauge has been able to detect ~67 000 features generated by the sublimation of the volatile content of icy particles. The nude gauge detection rate follows a trend that is inversely proportional to the heliocentric distance. This result is interpreted as a confirmation of a possible relation between the nude gauge detection rate and cometary activity. Thus, we compared the former with parameters related to cometary activity and obtained significant correlations, indicating that the frequency of icy particle detection is driven by cometary activity. Furthermore, by representing the volatile part of the icy particles as equivalent spheres with a density of 1 g cm−3, we obtained a range of diameters between 60 and 793 nm, with the smaller ones (<390 nm in diameter) having a size distribution power index of −4.79 ± 0.26.

Time response of protection in event of vacuum failure based on Nude ionization gauge controller

This article describes the design and application of fast-response vacuum protection sensor module, based on the Nude ionization gauge and a homemade controller named GH07X. A simulative test indicated that the controller’s response time was less than 200 μs when 1 atm air rushed into the vacuum system through a pulsed valve with 0.8 mm orifice nozzle and the emitting current of the Nude gauge was 4 mA. The experiment result showed that the response time mainly depended on the gas density as well as the electron emitting current of the Nude gauge filament. Compared with the vacuum protection sensors based on sputter ion pump and cold-cathode gauge, GH07X is faster and reliable besides, GH07X can be used as an ultrahigh-vacuum slow valve interlock controller with response time of 100 ms, which is faster than other gauge controllers. The widely used field–bus interface CAN and common serial interface RS232/RS485 are embedded in GH07X controller system.

Influence of gauge operation on background gases during high vacuum mass spectrometry

The effect of hot filament ionization sources on the residual gases in two UHV systems has been investigated by observing the interaction of Bayard-Alpert gauges with two different mass spectrometers. A glass-enclosed gauge on an oil diffusion pumped system and a nude gauge on a UHV ion pumped system were studied. Experiments with both systems have extended and confirmed earlier studies showing that the presence of a hot filament ionization gauge seriously perturbs the composition of a high vacuum atmosphere. By varying gauge electrode operating conditions at pressures from 10 −5 torr to 10 −9 torr it has been possible to qualitatively describe the mechanisms responsible for these background gas changes. The results indicate that at high pressures (10 −5 torr) surface desorption by ion bombardment in the vicinity of the gauges is the dominating cause of increases in the background level of all gases. However, at low pressures (10 −9 torr) changes are more specific to each individual gas species and the residual gas changes are caused by ionic pumping, thermal outgassing and dissociation, and electron bombardment desorption from the grid.

Free molecular transfer and pumping speeds

The net free molecular mass flow rate to surfaces or openings in low pressure vacuum systems cannot in general be calculated from “pressure” and “orific speed”, since completely random molecular motion only rarely exists. Mass flow rate under such conditions can however be calculated by using network analysis as has been done in radiant heat transfer. The author obtains an expression for the pumping speed in case of a non-uniform temperature distribution and shows that under certain conditions this equals the orific speed as measured by a nude gauge immediately adjacent to the orifice.

A Nude Type Bayard-Alpert Gauge and The Influence of Envelope Wall to Its Characteristics

A nude type Bayard-Alpert gauge of high sensitivity and low x-ray residual current is described. This gauge is featured by platinum grid and ceramic-sealed stem. By carrying out the sensitivity measurement in a large chamber as functions of electrode configuration and electrical parameters, an optimum condition of operation is fixed.The sensitivity for air is 25 Torr-1 and nearly constant for the pressure range between 10-3 to 10-11Torrreduced electron currents. The x-ray residual current corresponds to 1.7× 10-11 Torr.TThe sensitivity is influenced by the proximity of metal envelope. When the spacing between grid and metal cylinder wall decreases to 6.5mm, the sensitivity is increased by 50%. Compering this anomaly with Redhead and McNarry's data on the Nottingham type gauge, it can be shown that the effect of metal cylinder of different diameters at zero potential is very. similar to that of shield grid at different negative potentials. The drop of shield potential is interpreted as equivalent to the pnoximity of virtual zero-potential cylinder″. to the grid.TThe metal envelop has also an effect on the proportionality between ion current and electron current. Experiments show that this proportionality does not hold for the truly nude gauge at the electron currents above lmA, whereas it holds for both the nude gauge in a metal cylinder and normal gauge over the range of electron current from 40μA to 5mA.

Ultra-High Vacuum Use of Bayard-Alpert Ionization Gauges

Comparisons are made between the collected ion current vs electron emission current for a ``nude'' gauge (Veeco BGT-75) and a glass enclosed gauge (Veeco RG-75) both of the Bayard-Alpert type. The ion current is directly proportional to the electron current for the nude gauge, when the electron current is 100 μA or less, down to ion currents as low as the x-ray limit of the gauge which is 3×10−10 Torr. Good agreement between the glass and nude gauges is obtained over the limited range of electron currents where the glass gauge exhibits proportional behavior. A getter-ion pumped ultra-high vacuum system was used for the experiments.