Ionization gauge and method of using and calibrating same

An ionization gauge comprising:

• an anode defining a cylindrical anode volume and having an axis of substantial symmetry;
• a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis;
• and
• a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured, said collector electrode having a fixed, proximal end and a free, distal end;
• wherein said anode is provided with end caps which extend radially inward at least 25% of the radius of the anode but not more than 75% of said radius;
• wherein said collector electrode extends at its free end at least through said end caps;
• and
• wherein the length of said electron source is within a range which is (a) shorter than to (b) not substantially longer than the axial dimension of the region within said anode volume in which the electric field is predominantly directed radially inward, the electron source being located adjacent substantially only to said region.

An ionization gauge comprising:

• an anode defining a cylindrical anode volume and having an axis of substantial symmetry;
• a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis;
• and
• a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured, said collector electrode having a fixed, proximal end and a free, distal end;
• wherein said anode is provided with end caps which extend radially inward at least 25% of the radius of the anode but not more than 75% of said radius;
• and
• wherein said collector extends at its free end at least through one of said end caps.

An ionization gauge comprising:

• an anode defining a cylindrical anode volume and having an axis of substantial symmetry;
• a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis;
• and
• a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured;
• wherein said anode is provided with end caps which extend radially inward at least 25% of the radius of the anode but not more than 75% of said radius;
• and
• the length of said electron source is within a range which is (a) shorter than to (b) not substantially longer than the axial dimension of the region within said anode volume in which the electric field is predominantly directed radially inward, the electron source being located adjacent substantially only to said region.

An ionization gauge comprising:

• an anode defining a cylindrical anode volume and having an axis of substantial symmetry;
• a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis;
• and
• a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured;
• wherein said anode is provided with end caps which extend radially inward at least 25% of the radius of the anode but not more than 75% of said radius.

An ionization gauge comprising:

• an anode defining a cylindrical anode volume and having an axis of substantial symmetry;
• a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis;
• and
• a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured;
• wherein the length of said electron source is within a range which is (a) shorter than to (b) not substantially longer than the axial dimension of the region within said anode volume in which the electric field is predominantly directed radially inward, the electron source being located adjacent substantially only to said region.

An ionization gauge comprising:

• an anode defining a cylindrical anode volume and having an axis of substantial symmetry;
• a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis for launching the electrons in initially substantially parallel paths such that the emitted electrons follow substantially the same trajectories through the anode volume;
• and
• a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured;
• wherein said collector electrode has a diameter of not less than 0.015 in. and not more than 0.080 in.

An ionization gauge comprising:

• an anode defining a cylindrical anode volume and having an axis of substantial symmetry;
• a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis for launching the electrons in initially substantially parallel paths such that the emitted electrons follow substantially the same trajectories through the anode volume;
• a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured;
• and
• shield means defining a shielded volume within which said electron source, said anode, and said collector electrode are disposed where the shield means is at least partially open to permit transfer of gas molecules into the shielded volume and to permit external electrical connections to the electron source, the anode, and the collector electrode and where the shield means completely electrically encloses the electron source, the anode and the collector electrode so that potentials external to the shield means do not disturb the electric charge distribution on the electron source, the anode, and the collector electrode to thus stabilize the sensitivity of the gauge;
• wherein said anode is provided with a substantially uniformly transparent grid structure in the region where said electrons enter said anode volume and where said electrons exit said anode volume.

A method of measuring pressure with an ionization gauge having an anode defining a cylindrical anode volume and having an axis of substantial symmetry, a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis for launching the electrons in initially substantially parallel paths such that the emitted electrons follow substantially the same trajectories through the anode volume, and a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured, said collector electrode having a fixed, proximal end and a free, distal and wherein said collector electrode has a diameter of not less than 0.015 in. and not more than 0.080 in., said method comprising the steps of

• providing a shield means defining a shielded volume within which said electron source, said anode, and said collector electrode are disposed where the shield means is at least partially open to permit transfer of gas molecules into the shielded volume and to permit external electrical connections to the electron source, the anode, and the collector electrode and where the shield means completely electrically encloses the electron source, the anode and the collector electrode so that potentials external to the shield means do not disturb the electric charge distribution on the electron source, the anode, and the collector electrode to thus stabilize the sensitivity of the gauge;
• providing said anode with end caps which extend radially inward at least 25% of the radius of the anode but not more than 75% of said radius;
• locating said collector electrode so that its free end extends at least through one of said end caps;
• locating said electron source so that it is adjacent substantially only to the region within said anode volume in which the electric field is predominantly directed radially inward, the length of the electron source being within a range which is (a) shorter than to (b) not substantially longer than the axial dimension of said region;
• and
• providing said anode with a substantially uniformly transparent grid structure in the regions where said electrons enter said anode volume and where said electrons exit said anode volume.

A method of measuring pressure with an ionization gauge having an anode defining a cylindrical anode volume and having an axis of substantial symmetry, a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis, and a collector electrode collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured, said collector electrode having a fixed, proximal end and a free, distal end, said method comprising the steps of:

• providing said anode with end caps which radially extend radially inward at least 25% of the radius of the anode but not more than 75% of said radius;
• locating said collector electrode so that its free end extends at least through said end caps;
• and
• locating said electron source so that is it adjacent substantially only to the region within said anode volume in which the electric field is predominantly directed radially inward, the length of the electron source being within a range which is (a) shorter than to (b) not substantially longer than the axial dimension of said region.

A method of measuring pressure with an ionization gauge having an anode defining a cylindrical anode volume and having an axis of substantial symmetry, a source of electrons disposed outside said anode volume and extending in a direction substantially parallel to the anode axis, a collector electrode for collecting ions formed by impact between said electrons and gas molecules within said anode volume so that the pressure of the gas can be measured, said method comprising,

• providing shield means defining a shielded volume within which said electron source, said anode, and said collector electrode are disposed where the shield means is at least partially open to permit transfer of gas molecules into the shielded volume and to permit external electrical connections to the electron source, the anode, and the collector electrode and where the shield means completely electrically encloses the electron source, the anode and the collector electrode so that potentials external to the shield means do not disturb the electric charge distribution on the electron source, the anode, and the collector electrode to thus stabilize the sensitivity of the gauge;
• focusing substantially all of the electrons emitted by the electron source to follow substantially the same trajectories through the anode volume;
• and
• providing said anode with a substantially uniformly transparent grid structure in the region where said electrons enter said anode volume and where said electrons exit said anode volume.