Effusion Cell Valve

An effusion cell valve comprising:

• a crucible having an interior chamber and an open end;
• a valve seat adjacent the open end of the crucible comprising a closeable aperture;
• and
• an outlet nozzle downstream from the valve seat aperture.

An effusion cell valve comprising:

• a crucible having an interior chamber, an open end, and an inner diameter CD;
• a valve seat adjacent the open end of the crucible comprising a seating surface and an aperture having a diameter AD in flow communication with the open end of the crucible;
• and
• a valve disk having an inlet diameter DID and comprising a seating surface, wherein the valve disk is axially movable along a length of the effusion cell from a closed position in which the seating surfaces of the valve seat and valve disk contact each other, to an open position in which the seating surfaces of the valve seat and valve disk are disengaged, and wherein the ratio of AD:CD and/or the ratio of DID:CD is greater than 0.1:1.

An effusion cell valve comprising:

• a crucible having an interior chamber and an open end;
• a valve seat adjacent the open end of the crucible comprising an aperture in flow communication with the open end of the crucible;
• a valve member movable with respect to the valve seat to open and close the aperture;
• and
• an outlet nozzle downstream from the valve seat aperture, wherein at least one of the valve seat, valve member and outlet nozzle comprise machined graphite coated with a carbon-containing material.