Update on MDs for wideband
feedback system
K. Li
with contributions from
H. Bartosik, J. Fox, W. Hofle, C. Rivetta, B. Salvant, O. Turgut
LIU-SPS Coordination Meeting, 20 July, CERN
MDs on wideband feedback system
Summary:
With the latest upgrades including increased kicker power and new firmware for multi
bunch treatment the first 2 week MD was scheduled to set up and to test the new
system. Studies were foreseen in single bunch and in multi bunch mode to
demonstrate the capabilities of the wideband feedback system.
Content:
1. Status
2. MD plans and accomplishments
3. Next steps
21/06/2016
LIU-SPS Coordination Meeting
Status of the wideband feedback system
2 stripline kickers
+
2 x 2 power
amplifiers
(250 W,
5 – 1000 MHz)
21/06/2016
“The Box”
• 4 Gs/s digital
processing system
• Firmware for
independent control of
up to 64 bunches in
any configuration (e.g.
32 doublets)
LIU-SPS Coordination Meeting
MD plans
Stabilisation of e-cloud instability on multiple bunches of the high intensity
scrubbing beam (4 batches)
Stabilisation of TMCI-like instability on a single bunch
Excite and damp measurements with intra-bunch motion
• Weeks 25 & 26:
• 2 dedicated MDs on bunch train (scrubbing beam Q20)
• Several parallel MDs on single bunches (Q26)
• Availability was not 100%
21/06/2016
LIU-SPS Coordination Meeting
MD accomplishments
• On the feedback side:
• On the machine side:
• Calibration and time alignment
• Open loop measurements
Mo
21/06/2016
We
• Setting up the single beam for
reproducible and controllable
instabilities (Q26)
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
•
•
•
•
•
• On the machine side:
Calibration and time alignment
Open loop measurements
Testing the multi-bunch firmware
Discovering a bug in the firmware
Being frustrated
• Setting up the single beam for
reproducible and controllable
instabilities (Q26)
• Tuning chromaticity, trying to
linearize machine, optimizing
transverse damper, reducing space
charge… no reproducible
instabilities
• Being frustrated
Headtail monitor was not working reliably
Mo
21/06/2016
We
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
•
•
•
•
•
•
• On the machine side:
Calibration and time alignment
Open loop measurements
Testing the multi-bunch firmware
Discovering a bug in the firmware
Being frustrated
Firmware operational for multi
bunch treatment
• First application of the wideband
feedback system on a single batch
of 72 bunches – successfully
stabilized individual bunches
Mo
21/06/2016
We
• Setting up the single beam for
reproducible and controllable
instabilities (Q26)
• Tuning chromaticity, trying to
linearize machine, optimizing
transverse damper, reducing space
charge… no reproducible
instabilities
• Being frustrated
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
• 4 batches of 72 bunches
• Successful stabilization of last
bunches in 4th batch
Mo
21/06/2016
We
• On the machine side:
• Setting up the high intensity
scrubbing beam for reproducible
and controllable instabilities (Q20)
• Tuning chromaticity resulted in
vertical instability – however not
e-cloud like, i.e. rather coupled
bunch like
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
• 4 batches of 72 bunches
• Successful stabilization of last
bunches in 4th batch
Mo
21/06/2016
We
• On the machine side:
• Setting up the high intensity
scrubbing beam for reproducible
and controllable instabilities
• Tuning chromaticity resulted in
vertical instability – however not
e-cloud like, i.e. rather coupled
bunch like
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
• On the machine side:
• On Thursday night during the
Poland-Portugal game we lowered
the RF voltage  fast and
reproducible instability (Q26)
• We left the beam for the feedback
experts to perform open and
closed-loop studies
Headtail monitor operational
Mo
21/06/2016
We
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
• On the machine side:
• On Thursday night during the
Poland-Portugal game we lowered
the RF voltage  fast and
reproducible instability (Q26)
• We left the beam for the feedback
experts to perform open and
closed-loop studies
Mo
21/06/2016
We
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
• On the machine side:
• Transients after injection saturate
the feedback
• We use the transverse damper to
quickly remove the centroid
motion
• We are left with a mode-1 like
pattern – rise time still too fast to
handle by the system
• Chroma and voltage were adjusted
to lower the rise time 
successful mitigation of instability
in presence transverse damper
Mo
21/06/2016
We
• On Thursday night during the
Poland-Portugal game we lowered
the RF voltage  fast and
reproducible instability (Q26)
• We left the beam for the feedback
experts to perform open and
closed-loop studies
Mo
LIU-SPS Coordination Meeting
Fr
MD accomplishments
• On the feedback side:
• On the machine side:
• Transients after injection saturate
the feedback
• We use the transverse damper to
quickly remove the centroid
motion
• We are left with a mode-1 like
pattern – rise time still too fast to
handle by the system
• Chroma and voltage were adjusted
to lower the rise time 
successful mitigation of instability
in presence transverse damper
Mo
21/06/2016
We
• On Thursday night during the
Poland-Portugal game we lowered
the RF voltage  fast and
reproducible instability
• We left the beam for the feedback
experts to perform open and
closed-loop studies
Mo
LIU-SPS Coordination Meeting
Fr
Instrumentation
• The Headtail Monitor is absolutely essential but most of the time was
not fully operational (did not trigger, record, auto-load, read terminal
input,…) – Who are we officially supposed to contact for support?
• The LHC BPMs are important and needed for the multi-bunch studies
• The transverse BQM was not used so far
21/06/2016
LIU-SPS Coordination Meeting
Next steps
• Bring data together
• Schedule dedicated MDs to learn how to create the e-cloud instability
• Schedule parallel MDs to better characterize and understand the nature
of the observed bunch instability
• Optimisation of the transverse damper
• Other suggestions?
21/06/2016
LIU-SPS Coordination Meeting