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Argonne Wakefield Accelerator Facility

Cs2Te Deposition Chamber

There are two Cs2Te deposition chambers at AWA. The first chamber is dedicated to the AWA drive beamline. It is a stainless steel UHV chamber with a base pressure of 2×10-10 Torr.

20 nm layer of tellurium is deposited via thermal evaporation. When tellurium deposition is complete, cesium deposition commences and the photocurrent is monitored. Deposition continues for several minutes after maximum photocurrent is achieved. The result of this process is a Cs2Te thin film photocathode on a polished molybdenum substrate with an effective photocathode diameter of 31 mm and a typical initial QE of 15%. A load-lock transfer system is used for transport from the deposition chamber to the gun. The second chamber is still developing now. Its configuration is similar to the first chamber but it has more flexibility. We can use the second chamber to do cathode experiments, such as making different cathodes, observing the QE evolution in different environments.