DE1934940A1 - Ionization manometer tube - Google Patents

Description

BALZIiRS + PFEIFFER, HOCHVAKUUM GMBH, IiEINRrCH = IIERTZ-STRASSE 6

FRANKFURT / MAIN

Ionization manometer tube

The present invention relates to the measurement of pressures in vacuum chambers, especially when measuring relatively high pressures up to to a few Torr with the help of ionization tubes.

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Ionization manometer tubes for low pressures below about Io Torr are on the other hand, there are many variants in use, such as those for higher pressures Up to now, because of the disadvantages associated with their operation, we have hardly been able to enforce more details about this and examples of known ionization manometer tubes for higher pressures see “THE REVIEW OP SCIENTIFIC INSTRUMENTS Vol. 28, No. 12, Dec. I967, S 1θ51-1ορ * (O. J. Schultz and A. V. Phelp3i Ionization Gauges for Measuring Pressures, up to the millimeter range) and

PROCEEDINGS OF TIE SYMPOSIUM ON EIBCTRON AiD VACUUM PHYSICS, Hungary 1902, Budapest I963, S ^ oj5- * Ul (G. Hinzpeten Application of Ionization Manor Tube in the rock vacuum area).

This wafcsen an electron-emitting hot cathode, an electrode for Acceleration of the electrons emitted by the hot cathode, as well as one Ion collector (ion collector), which has the task of being accelerated by the To collect electrons in the gas space according to the gas density (and thus the pressure) generated positive ions. The ratio of the measured current of the positive ions J + to the current of the cathode

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emitted electrons J - is then known to be a measure of the goods of the vacuum in the measuring room * In the linear measuring range, the relationship applies · = - ■ PS »where ρ is the pressure to be measured and S is a proportionality con-J-

constant ("Sensitivity ^11" ).

An ionization manometer that can be used in industrial practice should provide a linear display over the entire measuring range. The fraction of the Ions collected by the trapper, however, depends on the mean free path * length of the same in the gas space and therefore decreases with increasing pressure. One cause of this phenomenon is that the more pressure increases, it becomes more and more muddy Ions are lost through recombination »before they reach the ion collector which affects the linearity of the display at higher pressures

In order to keep these pressures as high as possible, it was proposed that The distances between the individual electrodes of the measuring system are as small as possible to make what, however, requires a high precision of the mechanical construction and even slight deviations from the target dimensions, as in the Heating of the electrode system for the purpose of degassing can easily occur, result in large measurement errors. '

E3 is known to use a triode with an axial hot cathode, negative helical lattice as an ion catcher and with an anode that coaxially surrounds this arrangement and accelerates the electrons for measuring gas pressures. With such a system, in Schein the ion-collecting grid was at a distance of approx. 0. fS "nra (1 / 3Z") and the diameter of the anode cylinder was approx. 3 mm (1/8 ¹¹ ), a linear one Display reached up to about 1 Torr. Such an electrode system with the tight tolerances as they are for a measuring tube, which is used in a measuring system. Should be interchangeable, necessary to manufacture industrially, means a lot of effort. The sensitivity of these known measuring tubes was also very low

In other known arrangements were called electron acceleration and

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Ion-collecting electrodes plane-parallel Fiatton with a small distance from each other used, between which an oil cathode was stretched, which also requires high precision.

The present invention has set itself the task of a To provide a solution to the problem of vacuum measurement by means of triodes, which allows for an extended linearity range, with little effort in the Manufacturing manageable dimensions, and at the same time a larger one Sensitivity achieved. . ·

The ionization manometer tube designed as a triode according to the invention with an electron-emitting hot cathode, empty electron acceleration electrode, and with an ion collector arranged between the hot cathode and the electron boao acceleration electrode, is characterized in that the arrangement of the three mentioned. Electrodes and their Dimenionation be chosen so that the triode system has a penetration of 0.25. up to 1.00 having.

By "penetration ¹¹ D for the purposes of this specification the ratio C." / C of the electrostatic capacity between the Elektronenboschleuniguncsolektrode (anode) and the cathode C ^ one hand and the Ionenauffänger and

the cathode C. ". on the other hand understood; D · - “. ^GK - ^C GK

This achieves a linearity range of up to a few Torr despite the significantly larger dimensions of the electrode system than was considered necessary based on previous experience. The larger system dimensions allow larger tolerances in the Fatigjung and result in greater stability Operational.

An exemplary embodiment of the invention is described in more detail below.

FIG. 1 shows the mechanical structure of the triode syste, FIG. 2 a simple measuring circuit

In Fig. 1, 1 denotes a hot cathode capped between the two holding rods 2 and 5, which are simultaneous heating current supply electrodes. Thieves-.

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Numeral 4 denotes four electrically interconnected, of the Plate 5 supported bars, which together form the ion collector * As The electron acceleration electrode is a cylinder 6 which surrounds the hot cathode and the rods 4 and is coaxial with the cathode and which is positioned over the holding rod 7 is connected to the external circuit is provided. The inside diameter of the cylinder 6 is 12 mm, its length 25 mm, the distance between the rods 4 from the cathode 4 mm, the diameter of the hot cathode 0.5 mm, the diameter of the rods about 0.5 mmt

The electrode system described is located in the room in which the Gas pressure is to be measured and can in a simple circuit according to Fig. 2, which shows only the essentials, can be used. As can be seen, the indirectly heated cathode (its conventional heating circuit not shown ist) via a measuring device 11 for measuring the emission current J ″ with earth potential tied together; the ion collector 4 has a negative potential of, for example -5o V and the electron accelerating electrode 6 a positive of issued about loo V to earth. The measuring instrument 12 is provided for measuring the internal current. With the specified dimensions of the pipe system a sensitivity of 1.7 Torr ", more than a hundred times that Sensitivity of the triode mentioned above. The display for Stiek-

-7 substance at an emission current of 7 microamps was linear from Io to 1 Torr. This high sensitivity and the small area of the ion collector result compared to previous versions of known manometer tubes for higher pressures a much deeper so-called X-ray limit} in the case of the one described

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Example this is under Io Torr. This covers a measuring range for which previously two different gauges had to be used.

In addition to the circuit described, other known circuits can also be used for ionization manometer tubes of the same construction as they are for lower pressures are in use, are used, for example, special devices for stabilizing the electron emission current on iron.

PR 6856.

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Claims (1)

Pat en tans pr il'obi Ale Trioda auajebildete lonigationaaianoaieterröhre with a elÄronenemittieirenden iüühkathode, a ftlektronenbeachleunuigungeelektrode, and a "wipe the hot cathode uii dor ^ ^ un ^ lsktronenbeschleuiii stlelctrode be arrange th lonenauffänger, characterized & eke η η?. It is worthwhile, that the arrangement of the three manly electrodes and their integration is chosen as _{follows:; en: v} date the triodenuiuen JiVGh & rxtt from 0.25 to 1.00 aafweit 2, triode after ι ttentanapruchl, d a d u r c h g e k e a η .— draws, daaa der imrohmosaer der iSlektronanbeech acceleri, j; ung30lektiOde .5 M3 .16 now amounted to. 3 · triode according Patsntanapruch 1 with a zylLnderiuantelf ( 'tend [.lekti'ot.txi.ö3cjilt u;! .Igungs (5lektrod0 and Indians axis dee arranged Ulühkathode 2 / lLndera as ύ for ο h-j. Β k s. η ζ ei ch η et, daaa. the XorienauiT-'ätig; it is formed as a jyütem from ctrei - to five achaenjutrallels, around the cathode axially sysiwetrically on _{£ f} eorikietezi rods 4. Triode naoh i-atent claim 3, d a by g β k e η η a ο 1 ο h η e t, dasa four achaan parallel as ion collector voF # e .--. marriages are. PAD ORIGINAL PU 6ö56 00 9818/1 1 A 8 blank