Gauge Tubes Research Articles

Extension of thermocouple gauge sensitivity to atmospheric pressure

The amount of heat lost from a heated thermocouple (TC) junction through gaseous conduction varies widely with pressure over the range from 1 mTorr to atmosphere and this has largely confined accurate measurement by this technique to the range of about 1 mTorr to 2 Torr. A new design, which matches the junction temperature to a reference temperature, creates a basic constant temperature gauge controller and is largely responsible for fast response to pressure changes. A second control function which adjusts the reference temperature in a nonlinear manner depending on the pressure, modifies the controller response to the TC gauge’s intrinsic pressure sensitivity in such a way as to enhance response in the 1–15 mTorr and 2–200 T ranges, while attenuating its high sensitivity in the 15 mTorr to 2 Torr and 200 Torr to atmosphere regime. This technique gives rise to an output signal which better approximates the log of pressure over six decades. By time multiplexing the junction heating with measurements of its thermal emf, contamination of the thermal signal by the heating current is eliminated, while requiring only two connections to the remote gauge tube. The inclusion of a baffle in the gauge tube reduces inaccuracies in the response during fast pressure changes.

Some characteristics of an inverted magnetron cold cathode ionization gauge with dual feedthroughs

Single feedthrough cold cathode ionization gauges often suffer from spurious currents due to insulator leakage and field emission which mask the small pressure dependent ionization currents. This paper describes an inverted magnetron gauge tube designed to reduce these problems by using separate feedthroughs for the anode high voltage and the cathode current. The cathode is insulated from the grounded metal envelope. This gauge is useful for pressure measurement from 10−4 to 10−10 Torr in the constant voltage mode and from 10−2 to 10−6 Torr in the constant current mode. The characteristic curves typically show a change of slope at ∼10−9 Torr. When used at a magnetic field of 1200 G the slope above the inflection point is 1.08±0.02, while below it the slope varies from 1.4–1.9. It was found that operating the gauge for some time at a pressure of 10−4 Torr does not change the curve above the inflection point, but can alter the lower portion temporarily.

Microwave hyperthermia for brain tumors

Twelve patients with malignant brain tumors who had failed to respond to conventional therapies were treated with thermotherapy. Hyperthermic temperatures (∼43°C) were induced in the tumors using microwaves at a frequency of 2450 MHz that were guided into the tumors by one or more semirigid coaxial applicators. These applicators fit into 16 gauge tubes or needles and can be inserted into the brain with minimal damage to healthy tissues. During each treatment, the tumors were maintained at hyperthermic temperatures for 1 hour. Several treatments spaced a few days apart were usually administered. The procedure used for producing hyperthermia in brain tumors with microwaves proved to be safe and could be repeated several times without producing toxic effects. Objective tumor responses were obtained in 75% of the patients (decrease in tumor size, 3 patients; slowing of tumor growth, 2 patients; necrosis of tumor tissues verified by pathological examination, 4 patients). Favorable clinical responses were observed in 75% of the patients (rapid decrease in intractable headaches, 5 patients; improvements in clinical deficits, 4 patients). Also, in all patients, the microwave power required to heat for a given time or a given volume decreased during most of the thermotherapy sessions, possibly because of heat damage to the tumor vasculature. Our results, taken together with the results of other investigators, indicate that thermotherapy is a promising modality for treating malignant brain tumors, either as the sole therapy or in combination with radiotherapy and chemotherapy. The next logical steps would be Phase I/II type trials of subjects whose disease is less advanced than the disease of patients treated in the current series of investigations. (Neurosurgery 17:387-399, 1985)

4894. Nitrogen sensitivities of a sample of commercial hot cathode ionization gauge tubes: K E McCulloh and C R Tilford, J Vac Sci Technol, 18 (3), 1981, 994–996

4894. Nitrogen sensitivities of a sample of commercial hot cathode ionization gauge tubes: K E McCulloh and C R Tilford, J Vac Sci Technol, 18 (3), 1981, 994–996

An integrated circuit based vacuum ionisation gauge meter

A vacuum ionisation gauge meter using a pulse-width modulation circuit for the stabilisation of the electron emission current is described. This circuit has a wide range of current control for the filament and fits various kinds of ionisation gauge tubes very well. The application of integrated circuits makes the whole system stable, readily constructed and of low cost.

Method for mounting thermocouple gauge tubes

A method for mounting thermocouple gauge tubes which eliminates the need for teflon tape wrapping, ring seals, greases, etc. and essentially eliminates all sources of contamination is described.

EFFECT OF THE TEMPERATURE OF TUBE FEEDING ON GASTRIC MOTILITY IN MONKEYS

The diarrhea sometimes associated with nasogastric tube feeding has been attributed to the cool temperature of the formula. To test the effect of temperature variations of liquid feedings on gastric motility, a strain gauge and feeding tube were surgically implanted in the stomachs of rhesus monkeys. With the monkeys awake and restrained, the investigators infused constant volumes of water and liquid diet formula at varying temperatures and recorded gastric motility. The temperature of the liquid did not significantly alter gastric motility or gastric emptying, suggesting that the temperature of administration of the tube feeding is not a cause of diarrhea.

Characteristics of an Ion Source Made from a Nude Ionization Gauge Tube Element

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Sensitivity variations in the Bayard-Alpert ionization gauge Part one: Experimental measurements with a molecular beam probe and in a randomised gas

Measurements have been made of the variation in the local sensitivity factor within a Bayard-Alpert ionization gauge grid when exposed to an exploring molecular beam. A collimated molecular beam of argon passed through the gauge tube with the gas molecules travelling substantially parallel to the ion collector and cylindrical axis of the grid. Gas from an inlet vessel effused through two spaced collimation tubes (of 0.475 cm diameter) to form a molecular beam. The gauge tube (4 cm diameter) containing a grid of 2 cm diameter, 4 cm in length, was traversed across the fixed beam. Plots of the ion current as a function of the beam position are presented for gauge structures with and without mesh grid caps. Also, comparison tests were made in a chaotic gas atmosphere. The results show that the ion current to the collector was enhanced by a factor of 1.55 when grid caps were added in a random gas atmosphere, whereas the enhancement factor was 2.87 when grid caps were used with a molecular beam. The greater enhancement for the molecular beam was attributed to gas being back-scattered into the grid region by the end cap mesh. The effect of closing the exit end of the gauge tube and scattering a molecular beam in the envelope was also studied and this enhanced the “pressure” reading by a factor of 2.2.

Ion gauge tube of stainless steel: Anon,GEC Co, Vacuum Products Operation, Schenectady, NY.

Ion gauge tube of stainless steel: Anon,GEC Co, Vacuum Products Operation, Schenectady, NY.

The measurement of the speed of pumps

It is proposed to specify an “intrinsic” speed of a pump as well as an “intrinsic” conductance of components as obtained when these are connected to a large chamber or between large chambers. It is shown that by separating out an aperture conductance, both for the case of a component and a pump, the reciprocals of conductances and of pump speeds in composite systems are additive in the usual way, provided that the number of aperture conductances have been correctly accounted for. On the othe other hand Dayton suggested that the pump speed should be specified as measured with a test dome of the same diameter as the pump. In this case, the conductance of a tube of the same diameter as the pump needs to be modified to allow for the beaming effect of the gas into the pump mouth. It is shown that the alternative procedure based on the use of intrinsic speed and conductance is preferable in many ways and gives identical results for the net speed of a composite system, as obtained by the method of Dayton. Finally, it is shown that by moving the position of a tubulated gauge along a test dome of the same diameter as the pump, a position can be found where the measured pump speed is approximately equivalent to the intrinsic speed. For a test dome of effective length equal to the diameter, the gauge tube should be at a position on the wall, half a diameter away from the pump mouth.

Transistorized emission regulator for ion gauge and RF mass spectrometer tubes

Transistorized emission regulator for ion gauge and RF mass spectrometer tubes

Transistorized emission regulator for ion gauge and RF mass spectrometer tubes: N C Petersen and I W Price, Rev Sci Instrum, 35 (2), 1964, 1620–1621

Transistorized emission regulator for ion gauge and RF mass spectrometer tubes: N C Petersen and I W Price, Rev Sci Instrum, 35 (2), 1964, 1620–1621

Transistorized Emission Regulator for Ion Gauge and rf Mass Spectrometer Tubes

A circuit is described which was used for regulating the electron current in a Bayard-Alpert ionization gage and in a r-f mass spectrometer tube. Its operation and some of the results obtained are described. (D.L.C.)

775. Discharge suppressor for glass tubes with neutral gas flow and for Pirani gauge tubes: F. Karger, Vakuum Technik, 13(5), June 1964, 152–155

775. Discharge suppressor for glass tubes with neutral gas flow and for Pirani gauge tubes: F. Karger, Vakuum Technik, 13(5), June 1964, 152–155

Triggered discharge gauge tube and control

Triggered discharge gauge tube and control

Regulation of Ionization Gauge Emission Current to Better than 0.05%

A control system is described for regulating the temperature-limited emission current from the filament of an ionization gauge tube. A dc transistor circuit is used with a lamp and a photosensitive resistor to provide electrical isolation between the control and the controlled circuits. Emission currents from 10 to 0.5 mA can be maintained with a stability of better than 0.05% with the system.

熱陰極フイリップス型電離真空計に就て

By adding a thermal electron emitter to the ordinary cold cathode Philips gauge, a high sensitive ionization gauge is expected which works with the linear characteristics at normal operating voltage where usual ion gauges are operated, An additive fine needle extended at the cylindrical axis of the hot-cathode philips type ion gauge to collect the ion current, enables one to extend its measurable range to the ultra-high-vacuum region, in accordance to the principle of Bayard-Alpert ionization gauge with greater ease, Under these considerations, we have prepared several gauge tubes and have measured their characteristics.With such Philips-Alpert type ion gauge, the experimental results were satisfactory. The sensitivity was about 5 microamperes for the pressure p=1×10-6 mmHg under the working condition of 600 volts to the anode, -200 volts to the repeller and the needle at a magnetic flux density of about 200 gauss. At this time the electron c current Ie was about 1 mA. The linearity was confirmed over the pressure range from 2×10-6 to 1×10-4mmHg, and a good stability was found.The simpler hot-cathode Philips type ion gauge showed also a large sensitivity, but its characteristics was meager in its linearity and stability.

A Stabilized Ionization Gauge Circuit with Vacuum Tube Voltmeter

A complete control circuit for use with the usual triode ionization gauge tube is described. A modified Ridenour Lampson type circuit is employed to stabilize grid and plate voltage, as well as emission current. A simple vacuum tube voltmeter circuit permits the use of a relatively rugged 0–1 milliameter to read plate current. Special provision is made for outgassing, and for leak hunting.

Atomic Hydrogen Welding in Aircraft Production

In the early part of last year, the author was asked to examine and report on a number of welded test pieces. These test pieces were cruciform joints in T.45 tube, and had been oxy‐acetylene welded by skilled aircraft welders using DTD. 82A (soft iron) filler rod and had been tensile tested. The tubes were rather larger than are commonly met with in aircraft practice, being 1½ in. o/d and 16G. and 10G. in thickness. Some of the test joints comprised tubes of equal thickness and others of unequal thickness. The lighter gauge tubes were generally satisfactory, all failures occurring in the tube away from the welds, but the heavy gauge tubes all failed in the welds and showed that difficulty had been experienced in obtaining adequate penetration without the welds becoming over‐heated and of excessive size. These indications were still more pronounced in the joints comprising tubes of unequal size in that, in spite of all failures occurring in the lighter gauge tubes, the latter suffered from excess penetration and some oxidation, and the welds on the heavy tubes lacked penetration and were in parts defective. These findings suggested that oxy‐acetylene welding was not suitable for this particular application.