GTS meeting 10 04 16

• Cathode prep chamber
  • A new type of spring from a manufacturer has been ordered (free sample). The spring is Beryllium-copper.
  • The top heater and the rod for the mask are being lengthened to accommodate the travel of the 150 mm translation manipulator.
  • Mamun has been working on the Nb:CsK2Sb cathode QE vs wavelength at various temperatures
• Beam line / magnet
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• Gun HV chamber
  • NEG cartridges have been mounted, but only 6 out of 8.
  • The perforated plate has been dry-fitted
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  • The gun chamber has been baked at 250C with the NEG modules and the perforated screen only.
  • The NEGs were activated, first to 15 Amps while the chamber was at 250C, then a second time to 22 Amps while the chamber was back at room temperature.
  • The bake/activation cycle was performed to generate as much NEG dust as possible, which happens during the first two activation cycles per SAES paper.
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  • We assembled the electrode and even trained Yan on how to do that job!
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  • But we realized that the SS ball electrode did not get aperture for the shed widened from 1.25 in diameter to 2.16 in diameter!, So Bubba brought over the Nb, barrel-polished ball electrode which we assembled using the SS Yan's design shed, and that is why the ball and the shed reflect light differently in the picture below.
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  • BUT the Nb ball is about 1/8" smaller diameter than the SS ball. This means that the front and back cathode end piece cannot press hard enough against the ball, allowing it to be rotate around the puck axis of symmetry. This may lead to non0uniform gap between the ceramic and the shed, which in turns leads to nonuniform potential distribution leading to possible plug arcing.
  • The SS ball is now at the machine shop for opening the shed aperture. Bubba will re-polished and clean it. In this way, we will have an electrode with all SS, barrel polished pieces,