Parallel MD 2025-08-11

MD goals

Measure tune and chromaticity on SFT flat bottom without a momentum ramp at injection.

Ideal supercycle: SFT + MD1 + SHIP + MD1 (x2) with the option to switch on and off the MD1 in front of the MD1.

Tune measurements

The goal is to measure beam properties in operational condition but with with eddy current decays visible (i.e. no momentum ramp at injection to mitigate the effects) and in a condition without MD1 (quadrupole) ramped in front.

We should confirm whether eddy current effects conform with what is measured on the quadrupole bench, or if it’s something similar to what is seen on the main dipoles. The two decays studied are with/without MD1.

Setup

MD user: ?? MD cycle: MD_SHiP_L1230_East_Extraction_2025_clone (later renamed to _V2 during Parallel MD 2025-08-22)

• Copy over settings from SFTPRO1 at injection
• Flatten momentum ramp

Measurement

• Baseline: Measure tune evolution C200 - C1460
• Flatten orbit (add back MBI ramp)
• Reference: Measure tune evolution again with flattened orbit
• Flatten MD1 (main dipole and quadrupole) and flatten orbit
• Measure tune evolution again

Chromaticity measurements

The purpose is to measure the impact on the $b_3$ component on the beam when we have flattened the MD1 dipole cycle.

We need to measure how close we are to 0 chromaticity on the operational beam, and the chromaticity after switching off the main dipole cycle on the preceding MD1.

It’s possible that the beam goes unstable after switching off the MD1, in which case we need to decrease the chromaticity on the reference measurement and re-do it.

Based on these measurements we can compare against lab measurements of the sextupolar component of the remanent field, or determine if we see a chromaticity decay over the injection like on the main dipoles, in which case it would suggest the chromaticity error is caused by dynamic effects.

Setup

• Copy over settings from SFTPRO1 at injection
• Flatten momentum ramp

Measurement

• Baseline: Measure chromaticity evolution C200 - C1460 - Currently operational
• Flatten MD1 (main dipole) and flatten orbit
• Measure chromaticity evolution again

Test tools for Dedicated MD 2025-08-13

We can use any leftover time to prepare for the Dedicated MD and test the new pipeline when using $\dot{B}$ for predicting eddy currents, and the TransformerLSTM implementation.

MD log

I arrive at 14:00:00, beam is not set up so we spend the first hour asking OP to clone PSB, PS, SPS cycles to not affect Tirsis SHiP cycle. We get beam just after 15:00 and Tirsi helps me setting up the beam for tune measurements by gradually lowering intensity and adjusting tune as necessary. We reduce to ~5e12 and stay there.

LHC filling at 15:30-16:30, and we finish setting up at 17:00 and start taking measurements.

BBQ parameters

• chunk_size = 23.1 ms
• start = 0 ms
• end = 989 ms

QH measurements

We start with a vanilla injection without a momentum ramp, and start measuring QH at 17:04:00, and chirping is enabled at 17:05:00. We put back the momentum ramp at 17:16 and start taking measurements at 17:16:40 on QH and finish at 17:21:00. At 17:21:00 we flatten the momentum ramp, but since the orbit then is drifting we put back the MBI/IREF ramp at 17:22:13.

With the momentum ramp flattened we see a clear tune decay in the H plane. We keep the damper on in the V plane so it’s not as apparent.

At 17:29:40 excite H plane again for 10 shots at 0.02 ampl., and finish at 17:35:00.

Flatten MD3 at 17:35:30. Switch back MD3, there is a large orbit jump from injection to ca 100 ms from 1.0mm → -0.8 mm. We don’t know why this is the case. We try fix the RF phase and RF voltage, but no change. We switch back momentum ramp to do QV measurement.

QV measurement

Start acquisition at 18:23:20. Finish 18:28:00.
Flatten momentum ramp at 18:29:00. Acquire 10 shots even when not exciting. Excited at 18:31:00. Beam went unstable so we de-excite it. Finish the measurement at 18:37:00.

Chromaticity measurements

Start first chroma measurement 19:03:20 with momentum ramp.

Finish 19:15:00.

Without momentum ramp at 19:18:50. Finished 19:29:50.

Proceed to flatten MD3/MD1. Fix the initial orbit with previous BHYS correction, but we leave the orbit decay as-is. Then I adjust tune to separate QH and QV.

Start measurement at 19:50:00 without chirp and with 2 samples per acquisition. Finish 19:59. Then new measurement 20:00 with chirp. Finished 20:07:15.

Moved tune from 0.598 to 0.61, moved QH by 0.02 in LSA.

Logbook entries

https://be-op-logbook.web.cern.ch/elogbook-server/#/logbook?logbookId=424&dateFrom=2025-08-11T14%3A00%3A00&dateTo=2025-08-11T20%3A00%3A00

https://logbook.cern.ch/elogbook-server/GET/showEventInLogbook/4362072 https://logbook.cern.ch/elogbook-server/GET/showEventInLogbook/4362096 https://logbook.cern.ch/elogbook-server/GET/showEventInLogbook/4362101 https://logbook.cern.ch/elogbook-server/GET/showEventInLogbook/4362106 https://logbook.cern.ch/elogbook-server/GET/showEventInLogbook/4362111