Abstract:
PURPOSE:To enable a true ionic current caused due to pressure to be read by constituting an extractor-type ionization vacuum gage by installing an ion-collecting electrode below an ion-drawing hole and inserting an ionic-current controlling electrode between the ion-drawing hole and the ion-controlling electrode. CONSTITUTION:An ion-drawing hole 4 is provided in the center of the lower end of a bell-like ion-drawing electrode 3. An ion-collecting electrode 5 surrounded by an ion-reflecting electrode facilitating collection of ions, is installed below the ion-drawing electrode 3. A proper electric potential is produced by inserting a grid-like ionic-current controlling electrode 7, formed by the use of a meshy material or the like, between the electrodes 3 and 5 so as to read a true ionic current caused due to pressure. As a result, the factors of measurement limit can be completely removed by 100% modulation of ionic current, thereby pressures of 10 -10 Torr can be measured.
Abstract:
A method and apparatus for operating a multi-hot-cathode ionization gauge is provided to increase the operational lifetime of the ionization gauge in gaseous process environments. In example embodiments, the life of a spare cathode is extended by heating the spare cathode to a temperature that is insufficient to emit electrons but that is sufficient to decrease the amount of material that deposits on its surface or is optimized to decrease the chemical interaction between a process gas and a material of the at least one spare cathode. The spare cathode may be constantly or periodically heated. In other embodiments, after a process pressure passes a given pressure threshold, plural cathodes may be heated to a non-emitting temperature, plural cathodes may be heated to a lower emitting temperature, or an emitting cathode may be heated to a temperature that decreases the electron emission current.
Abstract:
A method and apparatus for operating a multi-hot-cathode ionization gauge is provided to increase the operational lifetime of the ionization gauge in gaseous process environments. In example embodiments, the life of a spare cathode is extended by heating the spare cathode to a temperature that is insufficient to emit electrons but that is sufficient to decrease the amount of material that deposits on its surface or is optimized to decrease the chemical interaction between a process gas and a material of the at least one spare cathode. The spare cathode may be constantly or periodically heated. In other embodiments, after a process pressure passes a given pressure threshold, plural cathodes may be heated to a non-emitting temperature, plural cathodes may be heated to a lower emitting temperature, or an emitting cathode may be heated to a temperature that decreases the electron emission current.
Abstract:
A method and apparatus for operating a multi-hot-cathode ionization gauge is provided to increase the operational lifetime of the ionization gauge in gaseous process environments. In example embodiments, the life of a spare cathode is extended by heating the spare cathode to a temperature that is insufficient to emit electrons but that is sufficient to decrease the amount of material that deposits on its surface or is optimized to decrease the chemical interaction between a process gas and a material of the at least one spare cathode. The spare cathode may be constantly or periodically heated. In other embodiments, after a process pressure passes a given pressure threshold, plural cathodes may be heated to a non-emitting temperature, plural cathodes may be heated to a lower emitting temperature, or an emitting cathode may be heated to a temperature that decreases the electron emission current.
Abstract:
An ionization gauge for isolating an electron source from gas molecules includes the electron source for generating electrons, a collector electrode for collecting ions formed by the impact between the electrons and gas molecules, and an electron window which isolates the electron source from the gas molecules. The ionization gauge can have an anode which defines an anode volume and retains the electrons in a region of the anode. The ionization gauge can have a plurality of electron sources and/or collector electrodes. The collector electrode(s) can be located within the anode volume or outside the anode volume. The ionization gauge can have a mass filter for separating the ions based on mass-to-charge ratio. The ionization gauge can be a Bayard-Alpert type that measures pressure or a residual gas analyzer that determines a gas type.
Abstract:
An electron-emitting cathode (6) consists of an electrically conducting emitter layer (7) attached to a side wall (2) which consists of stainless steel and a gate (9) which is fixed at a mall distance inside a concave emitter surface of the emitter layer (7). The cathode (6) surrounds a reaction area (3) containing a cylindrical grid-like anode (5) and a central ion collector (4) which consists of a straight axial filament. An ion collector current (lie) reflecting the densitiy of the gas in the reaction region (3) is measured by a current meter (11) while a gate voltage (V G ) is kept between the ground voltage of the emitter layer (7) and a higher anode voltage (V A ) and is regulated in such a way that an anode current (I A ) is kept constant. The emitter layer (7) may consists of carbon nanotubes, diamond-like carbon, a metal or a mixture of metals or a semiconductor material, e.g., silicon which may be coated, e.g., with carbide or molybdenum. The emitter surface can, however, also be a portion of the inside surface of the side wall roughened by, e.g., chemical etching. The gate (9) may be a grid or it may be made up of patches of metal film covering spacers distributed over the emitter area or a metal film covering an electron permeable layer placed on the emitter surface.