Flange Insulation and Grounding in the SPS Jose E. Varela 06 October 2015

Outline Overview of present situation for enameled flanges Implications for Impedance Conclusions

Overview of the present situation for enamelled flanges The main source of enamelled flanges in the SPS are the, approximately, 100 BPHs and 100 BPVs. Each has two enamelled flanges. Flange group #1Number Enamelled QD – QD 103 Enamelled BPV – QD 94 Non-enamelled QD – QD 69 PP – Long QD Bellows 76 PP - VVSA – Long QD Bellows17 Special Positions Group I 33 TOTAL 392 Flange group #2Number Enamelled QF – MBA82 Enamelled MBA – MBA14 Enamelled BPH – QF40 (104) Non-enamelled QF – QF27 Non-enamelled QF – QF No Bellows 21 Unshielded PP MBA - QF17 Special Positions Group II38 TOTAL239 (303) Flanges currently accounted for in the longitudinal impedance model. (Simplified classification - Only SSS accounted for)

Overview of the present situation for enamelled flanges Current longitudinal impedance model for the flanges. NOTE Below ≈50MHz the contribution of the enamel flanges is unknown.

Below ≈ 50 MHz, the impedance of enamelled flanges is not known. Enamelled flanges resonate somewhere between 1 and ≈50MHz This was reported several times in the past after tunnel and lab measurements. Overview of the present situation for enamelled flanges This ‘low frequency’ resonances were not considered to be important.

Measurement on the ENAMELLED flange LIU-SPS BD meeting Imaginary Part of the reflection coefficient

Measurement on the NON-ENAMELLED flange LIU-SPS BD meeting Imaginary Part of the reflection coefficient

Outline Overview of present situation for enameled flanges Implications for Impedance Conclusions

Implications for Impedance Right now, we would have higher impedance without enamel. Could be much worse without damping resistors.

Implications for Impedance Currently, we have: Low frequency effects: Unknown/Not quantified High frequency effects: On first order approximation, the enamel layer damps the resonances. Thus non- enamelled flanges have higher Q and higher impedance. QD flanges would have a much higher impedance if the enamel is removed (Q would go from 80 to 1000 for the 1.7GHz resonance). Depending on the action: If the enamel is removed somehow: The low frequency resonance would disappear. The flanges would have ‘much’ higher impedance (especially the QD ones). Shielded/Redesigned flanges would be almost unaffected. If some sort of low pass filter is implemented: The low frequency resonance would disappear. The high frequency impedance would be unaffected.

Outline Overview of present situation for enameled flanges Implications for Impedance Conclusions

There are around 400 enamelled flanges (mainly, 2 per BPM). The low frequency impedance of enamelled flanges is not known/ has not been quantified. We do know that there is a low frequency resonance (between 1 and 50MHz). Impedance wise, the enamel basically damps the flange resonances (significantly). It is thus, a potential source of EMC/EMI problems (as Fritz has pointed out many times). Depending on the way in which the enamel is ‘removed’, impedance could go up significantly. If some sort of low pass filter is implemented, the high frequency impedance would remain unaffected. Even if the enamel is completely removed, the shielded/redesigned flanges would be fine with it.