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Energy error - follow-up
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Europe/Zurich
A. Colinet, M. Fraser, A. Gorn, K. Li, I. Romera, F. Velotti
Failure cases
Change the tune
The first part of the beam that fits the stop bandwidth can be fast extracted to the NA.
In these circumstances, around 20% more beam would be extracted, which is within the operational margin of the BLM running sums thresholds used in the SPS ring.
There is no potential risk to the machine if this happens.
Setting a wrong momentum
The whole SPS machine would scale. The transfer line elements acceptance is of a few percents so the beam would be lost in the MBE. There would be clear losses caught by BLMs in the SPS or transfer line.
Bad trim
It is proposed to use fast running sums on BLMs near the BDF target to interlock. The BLM thresholds must be set during commissioning and scaled with intensity. During operation, the thresholds must be a function of the intensity setting. The fastest BLM running sum window is 2ms, which is well below the requirements from the BDF target to stop the beam within 100ms.
Steering
It is proposed to use automatic steering in YASP with limits.
Sending the SFTSHIP beam to AWAKE
NA and AWAKE use the same energy of 400GeV. Sending the SFTSHIP beam to AWAKE is theoretically possible, but very unlikely in an accidental scenario. The SFTSHIP user would have to declare proper settings for the MKE, and make sure the kicker pulses at the correct time to have the permit from the SPS extraction BIS. Running AWAKE or the NA at different energies would remove any possibility of sending the HI beam to AWAKE because of the energy check.
Conclusions
The machine protection mostly relies on BLM running sums for the energy error.
DI/DT is another hardware interlock. Unfortunately it if often masked because it exceeds the threshold during ramp up. OP would require multiple thresholds along a cycle to be able to use it as a reliable interlock.
No BETS check is required for the operation of the NA.
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