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7th CLIC-ILC BDS+MDI meeting II
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Europe/Zurich
CERN
CERN
Andrea presents update on BDS tuning simulations.
The procedure:
1. Multipoles OFF, 1-to-1 correction, Target Dispersion Steering (TDS)
2. knobs
3. Multipoles ON: TDS, knobs
Computing the target orbits from tracking is very important. 0.1% energy deviation
is used. 100K particles/bunch used in computation of targets. For the response matrices
single particle with average SR energy loss is used (this is available now in PLACET).
SR in quadrupoles are treated like a single particle groing trough it with the offset.
First step is to optimize gains and weights via Scans and Simplex.
Daniel comments that Andrea does not use the beta (weight for correction strength) values between 0 and 1,
this is the case for the linac. Daniel also comments that 10mum is on the small side.
Daniel suggests to compare at different gains to understand what plane dominates the gain-dependency.
What is the relative misalignment multipole-to-beam after multipole shunting? -> to be followed up since
magnet information could be more precise.
knobs computed from IP beam correlations. Only 6 knobs are independent from SVD. Application
of knobs is done via Brent minimization algorithm, this is a more appropiate way to apply the knobs
than the usual scan.
DFS after tuning knobs (with multipoles on) deteriorates luminosity.
Dainel suggests a more systematic approach for understanding knobs.
The procedure:
1. Multipoles OFF, 1-to-1 correction, Target Dispersion Steering (TDS)
2. knobs
3. Multipoles ON: TDS, knobs
Computing the target orbits from tracking is very important. 0.1% energy deviation
is used. 100K particles/bunch used in computation of targets. For the response matrices
single particle with average SR energy loss is used (this is available now in PLACET).
SR in quadrupoles are treated like a single particle groing trough it with the offset.
First step is to optimize gains and weights via Scans and Simplex.
Daniel comments that Andrea does not use the beta (weight for correction strength) values between 0 and 1,
this is the case for the linac. Daniel also comments that 10mum is on the small side.
Daniel suggests to compare at different gains to understand what plane dominates the gain-dependency.
What is the relative misalignment multipole-to-beam after multipole shunting? -> to be followed up since
magnet information could be more precise.
knobs computed from IP beam correlations. Only 6 knobs are independent from SVD. Application
of knobs is done via Brent minimization algorithm, this is a more appropiate way to apply the knobs
than the usual scan.
DFS after tuning knobs (with multipoles on) deteriorates luminosity.
Dainel suggests a more systematic approach for understanding knobs.
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