Cooled photocathode structure
View Patent ↗A photocathode for an image intensifier tube includes a faceplate, a glass plate disposed opposite the faceplate, and a span having one end attached to the glass plate and the other end attached to the faceplate for forming a sealed chamber between the faceplate and the glass plate. A semiconductor layer is bonded to a surface of the glass plate, where the surface is disposed outside of the sealed chamber. The semiconductor layer forms a photocathode. A thermal electric cooler (TEC) is disposed inside the sealed chamber for cooling the photocathode. The faceplate is formed from sapphire material. The glass plate is formed from high conductivity glass. The span is formed from either high conductivity glass or low conductivity glass. The faceplate and the glass plate form a path for light to impinge upon the semiconductor layer, and the photocathode of the semiconductor layer is configured to convert the light into electrons for emission toward an electron gain device.
1. A photocathode for an image intensifier tube comprising
a faceplate,
a glass plate disposed opposite the faceplate,
a span having one end attached to the glass plate and the other end attached to the faceplate, for forming a sealed chamber between the faceplate and the glass plate, and
a semiconductor layer bonded to a surface of the glass plate, the semiconductor layer disposed outside of the sealed chamber,
wherein the semiconductor layer transforms light into electrons,
a thermal electric cooler (TEC) is disposed completely inside the sealed chamber for cooling the semiconductor layer,
at least one cantilever bracket is attached to the glass plate at one end, and the cantilever bracket forms a seat for holding the TEC at another end,
the cantilever bracket and the span each extend away from the glass plate and do not touch each other, and
the cantilever bracket provides direct thermal conduction between the TEC and the glass plate.
2. The photocathode of claim 1 wherein the faceplate is an annular structure,
the glass plate is an annular structure, and
the span is an annular bracket extending between the glass plate and the faceplate for providing a separation distance between the faceplate and the glass plate.
3. The photocathode of claim 1 wherein
the faceplate is formed from sapphire material.
4. The photocathode of claim 1 wherein
the faceplate and the glass plate form a path for light to impinge upon the semiconductor layer, and
the semiconductor layer is configured to convert the light into electrons for emission toward an electron gain device.
5. The photocathode of claim 4 wherein
the electron gain device is a microchannel plate (MCP).
6. The photocathode of claim 1 wherein
the at least one cantilever bracket is formed of copper material to provide thermal conductivity between the TEC and the glass plate.
7. The photocathode of claim 1 wherein
the seat includes an indentation formed in the at least one cantilever bracket for receiving the annular TEC.
8. The photocathode of claim 1 wherein
the at least one cantilever bracket is bonded at an end to the glass plate.
9. The photocathode of claim 1 wherein
the sealed chamber is a vacuum.
10. The photocathode of claim 1 including
standoffs formed on top of the glass plate for providing a separation distance between the glass plate and the opposing faceplate.