Photocathode Fabrication Coming On-Line

Photocathode fabrication chamber with vacuum suitcase
Figure 1. Photocathode fabrication chamber with vacuum suitcase

CCR is nearing completion of its photocathode fabrication chamber. The main chamber was assembled and baked in March. The vacuum suitcase was assembled and is currently being baked. Figure 1 shows a photo of the chamber with the suitcase attached.
During the next couple of weeks we’ll be installing the support for the sputtering source and the internal support for the photocathode being processed. We also need to mount the laser and connect the picoammeter. We had a small setback when problems arose with our turbo pump. That’s now been replaced, and we’re moving forward again.
We’ll first fabricate cesium antimonide photocathodes. The antimony source will be installed in the next couple of weeks. We still need to assemble the first test photocathode with parts in stock. I’m hoping we can fabricate our first cathode by the end of November.
This program is funded by U.S. Department of Energy Grant No. DE-SC00009583.

Navy Funds Research to Mitigate Coolant Channel Corrosion and Gun Arcing

The U.S. Navy funded the Phase I Option of CCR’s program to use innovative coatings to suppress arcing in electron guns and reduce or eliminate corrosion in RF systems deployed in the fleet. The corrosion occurs in copper coolant channels in RF sources and solenoids due to excess oxygen and salts in the coolant.

TWT collector setup for application of protective coolant channel coating
Figure 1. TWT collector setup for application of protective coolant channel coating

CCR is developing coatings to prevent coolant channel corrosion in collaboration with N.C. State University. This follows highly successful life test studies that demonstrated coolant channel lifetime could be increased more than 500% using a nanometer-scale coating of ceramic. The coating is applied by flowing a sequence of gases through the device’s cooling system. Figure 1 shows the setup to coat a TWT collector. It is anticipated the coating will be added prior to final device tests. The process would be applicable to any fluid cooled device where high quality coolant is not available.

The arcing issue arises in klystrons following weeks or months of stand-by operation. The sudden application of high voltage creates spurious electron emission from the focus electrode, immediately taking the system off-line.During the next few months, CCR and N.C. State University will test the process on the cooling circuit of a solenoid manufactured by Arnold Magnetic Technologies.

High Voltage Cathode Test Facility
Figure 2. High Voltage Cathode Test Facility

CCR is investigating coatings that preferentially react with oxygen. This program will determine if coatings of carbon, titanium carbide or tantalum carbide will absorb the oxygen and prevent barium oxide formation. High voltage tests are planned during the next few months using CCR’s cathode test chamber (Figure 2).