SPS-BGI NEG coating of ceramic plate
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Europe/Zurich
Present: Wilhelmus, Hikmet, James, Gunn, Teresa
More details can be found here: https://indico.cern.ch/event/1274547/
James Storey on behalf of BI
- Having an electrode made from ceramic instead of stainless steel will reduce the heat load on the top electrode.
- For the LHC-BGI, back in 2006, the top electrode was made from ceramic and a square surface resistance of 60 Ohm/cm^2 NEG coating. The reason for the 60 Ohm/cm^2 is the electrostatic question (to damp the impedance modes). Wilhelmus will send a separate email with a deeper explanation
- The resistance has to be defined by the RF group, so the impedance peak and the heating can be reduced.
Wilhelmus Vollenberg on behalf of SCC
- Both Ti and NEG coating are possible options for heated areas. NEG (Ti alloy) can be activated, when heated above 200 ºC. In addition, it will become a getter surface and oxide free, which reduces the SEY. Ti is a metal. Both Ti and NEG will benefit of beam scrubbing to maintain a low SEY
- Carbon coating is transparent for impedance. R square is in order of MOhms.
- The presentation of P. Krkotic defines the conductivity, penetration depth, surface resistance and temperature range of the different NEG coating options (slides 20-21). For Ti, Hikmet will write an email to P. Krokotic to obtain the values.
- The resistivity changes very little when the layer thickness is modified.
- Test performed by SCC in the past, proved that using MACOR instead of Al3O2 could cause some breakdowns. In addition, the thermal expansion coefficient of MACOR (~9.3 µm/m-°C) is bigger than the one of Al3O2 (~6.4 µm/m-°C), which means that a plate made out of MACOR will enlarge more when
- There are no problems of adhesion with ceramics, so no underlayer is foreseen.
Hikmet Bursali on behalf of RF
- NEG/ Ti coating might cause broadband impedance – which could be beneficial. To be simulated
- It is needed a range of frequencies from 0 to 2.5 GHz.
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