LHC
LBOC – 30 March 2011
INJECTION STATUS – TOWARDS 144
BUNCHES
W. Bartmann, C. Bracco, L. Norderhaug-Drosdal, B. Goddard, W. Hofle, D. Jacquet, V. Kain, M.
Meddahi, J. Uythoven, D. Valuch, J. Wenninger
1
Injection Quality Status
LHC
o
24 bunch injection clean:
−
Loss maxima from uncaptured beam
−
TCDI loss maxima: fill 1646 – 200 bunches filling, 24 bunches per inj

LBOC – 30 March 2011
−
beam 2 3 % maximum, beam 1 8 % maximum
Beam 1 trajectory not perfect in H, pointing to HiRadMat switch magnet
TCDIs
2
Fine tuning of some thresholds required
LBOC – 30 March 2011
LHC
o
From time to time: low losses “seem” high
o
BLMQI.06L2.B2I20 threshold too low
Threshold of BLMQI.06L2.B2I20
3
Transverse losses - observations
LHC
o
Scraping in the SPS needs to be well under control and switched on
−
SIS surveillance will come
Beam 2:
8 bunch injection,
no scraping on
LBOC – 30 March 2011
o
o
Correcting back to reference trajectory works well
−
Still more statistics needed for consistency between pilot and nominal intensity
corrections
−
Need to be able to compare steering settings for 2 users and task in nominal sequence for
copy
−
Then steering to be done by OP
For the time being no issues for increasing intensity from transverse losses
4
Longitudinal Losses
LHC
o
Larger capture voltage seems to pay off:
−
But also some filters changed (e.g. TCTVb)
−
Losses at the end of filling: 200 bunch fillings
Max loss in percentage from dump thershold downstream of TDI
Fill Nr
−
LBOC – 30 March 2011
o
Beam 1 [%]
Beam 2 [%]
1645
5
10
1646
10
16
1647
6
8
…need to check losses on TCLIA/TCTH for beam 1 – losses on D2 on other side are higher
than on triplet
More analysis needs to be done. If possible would like to re-calibrate
5
Abort Gap Cleaning @ Injection
LHC
Available now:
o
Sub-Sequence to move abort gap cleaning to injection settings
o
Sub-sequence to stop and start abort gap cleaning:
LBOC – 30 March 2011
o
−
start abort gap cleaning in prepare for filling sequence
−
…and stop before starting the ramp (tune feedback)
Status:
−
Tested with beam: first bucket, NOT with last possible bucket
−
Sub-sequences are not part of nominal sequence yet
−
MCS checks need to be re-enabled and tested
6
Injection Cleaning – not tested with beam
LHC
o
Injection Cleaning – modus operandi:
−
Injection sequencer requests next injection + configures and switches on cleaning
−
No injection event: injection cleaning switched off with injection sequencer time-out or
internal time-out of injection cleaner
−
If injection arriving: automatic switch off cleaning
−
LBOC – 30 March 2011
o

injection forewarning – details still to be discussed

With beam-in
At the end of filling: cleaning amplitude and excitation mode set to zero through sequence
Sequences: prepared, not in nominal sequence

Sub-sequence to prepare cleaning before filling

Sub-sequence to disable cleaning after filling
7
Injection Cleaning in Injection Sequencer
LHC
LBOC – 30 March 2011
o
Implemented as part of the injection sequencing
8
Towards 144 bunch injections
LHC
o
Quantify effect of TI8 shielding installed during TS (1 hour)
o
Check aperture TI2 and TI8 after vacuum intervention Shutdown – needed before
injection of >24b (0.5 shift)
o
75 ns spacing, up to 96 bunches (0.5 – 1.5 shifts)
o
LBOC – 30 March 2011
o
−
Check losses in the line, oscillations, scraping SPS
−
Re-steer if necessary, re-optimise collimators if needed (unlikely...)
50 ns spacing, up to 144 bunches (1 – 3 shifts)
−
Start with 12b
−
Check losses in the line, oscillations, scraping SPS
−
Re-steer if necessary, hope not to have to re-optimise collimators (can open to +/-5 sig if
needed)
−
Increase intensity injected in steps (36, 72, 108, 144)
−
Checks in SPS extraction, TLs and in LHC at each step (losses, trajectories, oscillations,
damping, capture, cleaning, vacuum, ...)
25 ns only after experience
−
Have to obtain more operational experience with up to 144 bunches before increasing the
injected intensity
−
Including experience with abort gap and injection gap cleaning
9
LBOC – 30 March 2011
LHC
10
Beam 2 – 24 bunches
LBOC – 30 March 2011
LHC
11