Cold-cathode Gauge Research Articles

Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence of mere annealing and of growth in vacuum systems to shed light on the reasons behind the reduction of perovskites. When comparing the existing literature regarding the reduction of the perovskite model material SrTiO3 it is conspicuous that one finds different oxygen pressures required to achieve reduction for vacuum annealing and for chemically controlled reducing atmospheres. The unraveling of this discrepancy is of high interest for low pressure physical vapor depositions of thin films heterostructures to gain further understanding of the reduction of the SrTiO3. For thermal annealing, our results prove the attached measurement devices (mass spectrometer/ cold cathode gauge) to be primarily responsible for the reduction of SrTiO3 in the deposition chamber by shifting the thermodynamic equilibrium to a more reducing atmosphere. We investigated the impact of our findings on the pulsed laser deposition growth at low pressure for LaAlO3/SrTiO3. During deposition the reduction triggered by the presence of the laser plume dominates and the impact of the measurement devices plays a minor role. During post annealing a complete reoxidization of samples is inhibited by an insufficient supply of oxygen.

SuperKEKB 真空機器制御システムと総合試験

SuperKEKB is an upgrade project of KEKB, which is a double ring collider of electron and positron beams. The vacuum control system has also been upgraded. Key changes related to the framework of the system are that Computer Automated Measurement And Control (CAMAC) system as a data logger and VME computer as an Input Output Controller (IOC) of Experimental Physics and Industrial Control System (EPICS) have been replaced with CompactRIO (cRIO) and a Linux CPU module of Programmable Logic Controller (PLC), respectively. As an integrative and practical test, we have executed the final evacuation process, including the baking of sputter ion pumps and the activation of Non-Evaporable Getter (NEG) pumps, in a section between two gate valves in the SuperKEKB main ring. The control system supervised the discharge currents of ion pumps, readings of Cold Cathode Gauges (CCGs), heating power for the activation and so on. The new control system is in preparation for a start of the beam commissioning on fiscal 2015 in Japan.

Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source

The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H(-)) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H(-) beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H(-) beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.

Beam induced vacuum measurement error in BEPC II

When the beam in BEPCII storage ring aborts suddenly,the measured pressure of cold cathode gauges and ion pumps will drop suddenly and decrease to the base pressure gradually.This shows that there is a beam induced positive error in the pressure measurement during beam operation.The error is the ...

Inverted magnetron manometer with enhanced operating time

If a cold-cathode ionization gauge is operated in a gas atmosphere with a high content of hydrocarbons at high pressures, the pressure reading of the gauge is disturbed by the contamination after a certain time of operation. Since in the most cases it is not possible to eliminate these disturbing residual gas components, one has to demand that the measuring process may not be substantially influenced by these gas components. To enhance the time of reliable pressure reading of a cold-cathode gauge we have equipped the entrance of an inverted magnetron gauge head with an ion baffle. By this measure the time of a reliable operation of the gauge is increased at least by a factor 3. The construction of this ion baffle is rather simple. It does not require any additional voltage supply or additional magnets. An additional feedthrough is only necessary for the measurement of the discharge current of the measuring system. The gauge has a range of pressure measurement from 10 −9 to 3×10 −3 mbar.

Inverted-magnetron cold-cathode gauge in hybrid-discharge mode

In high-vacuum measurement, cold-cathode ionization gauges have been widely used due to their unique advantages such as being simple and robust, low outgassing, x-ray effects, and so on. But during the measuring process, they show that a considerable pump effect, contamination buildup, and the heating and sputtering of the electrode surface from discharge can also become a serious problem at higher measured pressures. In such circumstances, pulsed operation is a good solution. However, the lowest measurable pressure of cold-cathode ionization gauges in pulsed operation is hard to extend, which limits its application. But if the measurable range of the cold-cathode gauge is divided into two regions, the low-pressure region where it is operated in dc discharge mode to ensure its lowest measurable pressure and the high-pressure region where it is operated in pulsed-discharge mode to reduce its above disadvantages at high pressures, the problem can be well solved. This article describes a pulsed high-voltage generating circuit controlled by a single-chip CPU to perform such a hybrid discharge in an inverted-magnetron gauge. With this circuit, the following problems of an inverted-magnetron gauge were investigated: the difference between pulsed-discharged mode and dc discharge mode, one method of extending the low measurable pressure limit in pulsed-discharge mode, the volt-current characteristics at different pressures, and constant-current pulsed-discharge measurement at pressures above 2×10−2Pa.

ISAC target vacuum system

The Isotope Separator and Accelerator (ISAC) facility at TRIUMF has been in full operation since 1999. The ISAC east and west targets use proton beam from the cyclotron to produce various radioactive isotopes, which are then ionized and extracted. The ions are then passed through the mass separator and selected ions are transferred to the low energy experiments or injected into a radio frequency quadrupole accelerator. The accompanying radioactive contamination from the production of radioactive ions requires a complex vacuum system. The main target vacuum space consists of two semiseparate (primary and secondary) volumes pumped by turbo-molecular pumps. The primary volume uses four pumps while the secondary volume uses two pumps. Two hermetic rotary vane pumps are used as backing pumps. The nominal vacuum in both volumes is about 1.33×10−4Pa(1.0×10−6Torr). The pressure is monitored by two cold cathode and two hot filament ion gauges. The cold cathode gauges are used to interlock the system, which is critical during the bake out of the target and beam production. The exhaust gas from the vacuum pumps can be radioactive. Three gas storage tanks (decay tanks) are used for temporary storage of the radioactive exhaust and its controlled release to the atmosphere. Gas-species insensitive membrane gauges are used for monitoring the pressure in the storage tanks. This article describes the details of the ISAC target vacuum system as well as some procedures related to the handling of the exhaust gas with traces of radioactive contamination produced by the targets.

Pressure/current characteristics of a magnetron cold cathode gauge

The gauge characteristics for a magnetron gauge in the pressure range 10 −8–10 −5 mbar with nitrogen as a test gas have been studied. The discharge current versus pressure was measured at different magnetic fields from 0.10 to 0.15 T and anode voltages from 4.0 to 7.0 kV. The results showed that a change of slope appeared at pressures between 5×10 −8 and 5×10 −7 mbar. At higher magnetic fields, a change of slope appeared at lower pressures. The slope of the curve below the inflection was higher than that above the inflection. At the lowest magnetic field (0.10 T), a divergence of the curves was observed at pressures below the inflection. The slope of the curve showed no clear dependence on applied voltage.

On the possible use of a commercial Penning gauge as a magnetic field sensor

Penning sensors were originally conceived to extend the measurement range of cold-cathode gauges in the direction of low pressures by introducing an additional constant magnetic field. This paper examines the possibility of using a commercially available sensor to measure magnetic field by keeping pressure constant. For the preliminary tests reported, a commercial Penning gauge was exposed to magnetic fields in the range of a few tens of mT to 1.1T. Three different regimes were identified. In the first, up to 150mT, the measured current increases linearly with the applied magnetic field. Following a very irregular transition region of the order of 50mT, for fields between 200mT and 1.1T, the measured current decays relatively smoothly. The results suggest that the principle may be applicable for the measurement of steady-state fields in harsh environments, with high temperature and neutron fluence.

Hybrid PIG–ECR discharge as low-pressure sputtering system

The paper reports on a cold-cathode Penning ionization gauge (PIG) discharge ignited and sustained by microwave electron cyclotron resonance argon plasma at pressures below 0.01 Pa. The discharge was created in a 20-cm-diam PIG anode with a length-to-diameter ratio of two. The experimental data show that the discharge exists in a high-current discharge mode with a considerable cathode fall and a weak anode fall. The measurements of the discharge current and plasma parameters as a function of the discharge parameters are reported. The mechanism of the discharge and its possible applications are discussed.

A low-voltage Penning cell for vacuum measurement and vacuum technology

This paper presents new results on the performance of a special cold-cathode gauge. The use of an AC and DC voltage simultaneously as the power source makes it possible to ignite and sustain a discharge at a significantly lower voltage than normal over a wide pressure range (from 5 to 3×10 −6 Pa). The Penning discharge voltage can be as low as 20 V at a pressure of 0.3 Pa and 300 V in high vacuum. For low values of pressure, the discharge current has a monotonously increasing dependence on the gas pressure. If a low RF voltage is applied to a high-voltage DC discharge, the discharge current increases in many times. These discharge properties can be used to improve the performance of devices that use the Penning and other magnetic discharges (total and partial pressure gauges, leak detectors, ion pumps, ion sources and hot plasma sources). A vacuum gauge of this type combines the best features of magnetic discharge and hot cathode ionization gauges.

Characteristics of a magnetron cold cathode gauge

The discharge characteristics of a cold-cathode gauge of the non-inverted magnetron type were studied in ultra-high vacuum. The experimental magnetron cell of length 56 mm and diameter 32 mm was made of stainless steel. The cathode with a diameter of 6 mm was placed along the anode axis. The diameter of the anode was 25 mm and the length was 50 mm. Discharge current versus voltage and magnetic field was measured in the pressure range between 1×10 −8 and 1×10 −6 mbar. It was found that the current at first slowly increased with increasing voltage, reached a maximum at a certain voltage, and decreased rapidly with further increase of the voltage. The voltage, at which the current reached the maximum, depended on the magnetic field density and slightly on the pressure. A novel type of a cold cathode gauge with a self-adjusting power supply is suggested.

Surface analysis of contamination layers in cold-cathode gauges

The influence of gas atmosphere on the long-term operation characteristics of a commercial cold-cathode gauge was studied. The changes of the electrode surfaces due to contamination effects of the so-called double-plasma gauge CF 2P by ALCATEL (double Penning system) were investigated by Auger-electron spectroscopy, X-ray photoelectron spectroscopy and scanning electron spectroscopy. Contrary to the widespread opinion that particular contamination is mainly caused by the polymerization of hydrocarbons in the discharge chamber of cold-cathode gauges, we found a contamination layer on the electrodes which consists only of sputtered cathode material. The distribution and thickness of the layer can give information about the preferred ion trajectories and convenient design features for a long life and stable operation of this type of gauge. Layer thickness seems to be a direct function of the pressure dose, independent of small changes in chemical composition of the layers and independent of the pressure itself.

Investigations of the long-term measuring stability of cold-cathode gauges

Cold-cathode ionization gauges (CCGs) are used widely for pressure reading in vacuum systems due to large measuring range, robustness and relative low cost. Amongst the many advantages of CCGs, however, these instruments are restricted in use by decreasing measuring accuracy over operating time as internal electrodes become contaminated. Thus, to guarantee a consistently high measuring accuracy, this gauge type needs to be calibrated regularly after a fixed operating time period. With the aim of quantifying the useful lifetime of CCGs we investigated the measuring behavior of different commercial CCGs in several long-term-operation tests. After a first calibration, the gauges were operated in a vacuum atmosphere with a high fraction of hydrocarbons for several thousand hours at varying high-vacuum pressures. After use, the gauges were re-calibrated and changes in their characteristics analyzed. To compare the operating states of the used CCGs a new basic quantity was introduced: the so-called pressure dose. Using this quantity it should be possible to verify roughly the effective lifetime of CCGs until their pressure readings become erroneous due to contamination effects. It was found that the pressure reading of all tested CCGs become inaccurate after a pressure dose of about 1 mbar h.

Cleaning a Cold Cathode Gauge Tube

Abstract This topic appeared on the MSA list server In December 2002 and January 2003. While cleaning my gauge tube recently, I documented the steps. In this article I describe cleaning a Varian 524-2 gauge tube. There are a number of other cold cathode and penning style gauge tubes on the market, Edwards CP-25 (old penning), CVC GPH-001A(old cold cathode), Pfeiffer IRK 250 (new cold cathode) to name a few. The cleaning steps are very similar. Consult the instructions that came with the gauge tube or visit the vendor's websites.

Neural network modelling of cold-cathode gauge parameters

This article describes modelling of the operating characteristics of a cold-cathode ionisation gauge (CCG). The gauge characteristics were measured on a gauge comparison UHV calibration system with a test chamber, an extractor gauge, a spinning rotor gauge, and a gas manifold with a precise leak valve. Discharge intensity was measured vs. anode voltage at different pressures selected in the range from 1×10 −9 to 1×10 −5 mbar, and vs. pressure at different operating voltages ranging from 1.2 to 9 kV. In all cases the magnetic flux density was the same and amounted to about 0.13 T. The CCG exhibits an extremely low thermal outgassing rate and a low measurement limit. Therefore, it is suitable for pressure measurements in the ultrahigh vacuum range; however, it has a significant disadvantage. The discharge current vs. the pressure characteristic is non-linear and, in some cases, even discontinuous. The measured CCG characteristics were used as an input for the artificial neural network, which was used to generate a non-linear CCG input–output function used for linearisation purposes. It is generally known and strictly proven that neural networks are capable of learning and building any kind of real and non-polynomial input–output function. Furthermore, it was also mathematically proven that the single hidden neural layer system can learn any function. Other authors have reported that the learned function characteristics are not always continuous. In our experimental work, no mapping discontinuities in the formed model were detected. Despite the fact that learning of the input–output characteristics can be obtained by the neural networks with only one hidden layer, we have used the multilayer neural networks that exhibit a faster convergent and smoother learning process. The neural networks were trained to perform the transfer function between the input gauge parameters and the pressure. The neural networks are a suitable solution for CCG characteristics modelling and thus offer the possibility to overcome the disadvantages of the CCG.

Comparison of the stability of hot and cold cathode ionization gauges

When ionization gauges are used as reference or secondary standards, their stabilities are the most important features. Generally, only hot cathode gauges are used as reference or secondary standards in calibration services. Some traditional reasons preventing the use of cold cathode gauges are the presence of discontinuities in the current versus pressure characteristic, the ignition delay at very low pressures, and the poor stability especially under contaminating vacuum environments. Though current inverted magnetron designs are believed to avoid some of these problems, at least under clean conditions, no “hard facts” have been published to support this claim. Here, we present the experimental results of calibrations of three hot cathode gauges and two inverted magnetrons against a primary high-vacuum standard over the range 10−7 to 10−3 Pa with gases of N2, Ar, He, and H2, respectively. During a continuous observation period of 72 h at a constant pressure of about 1×10−4 Pa, hot cathode gauges showed better stabilities than inverted magnetrons in N2, Ar, and He, but all gauges behaved similarly in H2. Repeated calibrations over a period of about 6 months showed that all gauges had similar long-term stabilities in N2, Ar, and He. For H2, however, the stability of inverted magnetrons was better than that of hot cathode gauges. For different gases, the discontinuities of inverted magnetrons occurred at different pressures, making their calibrations more elaborate.

The Contamination Effect of Cold Cathode Gauges.

For several decades cold cathode gauges are widely used in vacuum systems for pressure measurement in the medium, high and ultra-high vacuum range. This type of ionization gauge is not only characterized by its wide measuring range, but also by its robustness and its relative low costs. Although cold cathode gauges have many advantages, however, it is known that the measuring accuracy of these instruments decreases with increasing operating time due to cathode sputtering and plasma-chemical reactions within the discharge cells causing contamination of the gauge. This effect, in turn, causes initial failures or disturbances in the pressure reading of these vacuum gauges.In this paper the contamination process is analyzed, the main causes for this perturbing effect are presented and a review of some promising methods for the reduction of the rate of contamination of cold cathode gauge heads are discussed.

冷陰極電離真空計によるＫＥＫ放射光リングＰＦ‐ＡＲの圧力測定

Synchrotron light source PF-AR was improved to realize higher performance in 2001. This improvement involved the renewal of the entire vacuum system to attain lower vacuum pressure for required beam lifetime. Thermal cathode ionization gauges, the most suitable gauges for the pressure measurement in the new system, were unacceptable because of both possible radiation damage to the controllers and the restriction of the budget. Cold cathode gauges (CCGs) were then chosen for the new system, while they usually have instability in the pressure range of 10-7 Pa and lower. For the solution of this problem, we adopted the improved cold cathode gauges that hold the Penning discharge even at 10-8 Pa and acquired calibration data with a pre-calibrated B-A gauge. We have originally designed CCG controllers using the calibration data, which enabled the reliable measurement in 10-8 Pa range.

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.