Pressure sensor and leak detector

A leak detector comprising, in combination:

• a housing having an axis and first and second compartments spaced along said axis and hermetically separated by a partition;
• means for placing said first compartment in communication with an evacuated space to be monitored for leakage;
• an ionization cell in said first compartment producing an electric current determined by gas in said first compartment;
• means in said second compartment for performing a control function in accordance with the current supplied by said cell, including a cup shaped shield spaced from and opening away from said partition, a relay mounted in said shield, and feed-through filtering means having first ends extending through the bottom of said cup shield and second ends within said compartment beyond said shield;
• and hermetically sealed feed-through means for making electrical connection with said cell through said partition into said second compartment, said partition being of aluminum and said hermetically sealed feed-through means comprising a solderable conductor, a metallic tube surrounding and insulated from said conductor and having a first end portion of stainless steel, a second end portion of aluminum, a solid state diffusion bond joining said end portions, means sealing said first end of said tube to said conductor including a ceramic layer sealed to said conductor and a stainless steel portion sealed to said ceramic layer and welded to said first end portion of said tube, and means welding said second end portion of said tube to said partition to surround an aperture for traversal by said conductor.