Transcript Injection and Lessons for 2012 M.J. Barnes, W. Bartmann, C. Bracco, K.

Injection and Lessons for 2012
M.J. Barnes, W. Bartmann, C. Bracco, K. Cornelis, L. Drøsdal,
B. Goddard, V. Kain, M. Meddahi, V. Mertens, J. Uythoven
Special thanks to: Collimation, BLM, MPP,OP teams
Outline
2011 Operation
 Injection:



How far did we go? 144 and 288 bunches
Mitigation measures
Transfer line stability:







Shot-by-shot and bunch-by-bunch variations
Source of instabilities
Steering
Improvements
MKI Failures
Other issues
Conclusions and 2012 Operation
LHC Performance Workshop - Chamonix 2012
06/02/2012
Injection Losses and Intensity Limitations
From Chamonix 2011:
Loss type
2011
2010
Losses in % of dump threshold B1/B2
8b
16b
24b
32b
48b
96b
144b
TCDI shower
1/2
3/5
4/6
5/8
23/24
<50?
<75?
Uncaptured beam
4/2
12/3
12/5
16/8
20/8
<40?
<60?
Injection of 144 bunches became
fully operational in 2011!
B1, max loss
4% dump
LHC Performance Workshop - Chamonix 2012
Not optimised
Linear extrapolation for
2011 operation
B1, max loss
62% dump
06/02/2012
Injection of 288 Bunches During MD

288 bunches (1.05e11 ppb, 2.5-2.7 mm) injected at 30% of
thresholds
Beam 1
288 bunches < 27%
LHC Performance Workshop - Chamonix 2012
06/02/2012
Injection of 288 Bunches During MD

288 bunches (1.05e11 ppb, 2.5-2.7 mm) injected at 30% of
thresholds
Beam 1
288 bunches < 27%
Beam 2
288 bunches < 32%
LHC Performance Workshop - Chamonix 2012
06/02/2012
Injection of 288 Bunches During MD

288 bunches (1.05e11 ppb, 2.5-2.7 mm) injected at 30% of
thresholds
Beam 1
288 bunches < 27%
Beam 2
288 bunches < 32%
 Still work to be done to optimize beam in the
SPS/injector chain and accumulation in the LHC
ring and lifetime (RF, transverse damper,
chromaticity…..)
 Vacuum activity observed at the MKI during
injection
 More statistics needed
 Very promising in view of operation with
nominal intensity
LHC Performance Workshop - Chamonix 2012
06/02/2012
Mitigation Techniques

TL showers:







Local shielding between TCDIs and LHC (×2-3)
Beam scraping in SPS (×2)
Opening TCDIs (×4)
Moving/adding TCDIs (under study)
BLM sunglasses (Little Ionisation Chamber LICs)
Improve transfer line stability
Uncaptured beam




Local shielding at TDI (under study)
Injection and abort gap cleaning (×10)
Carefully monitoring beam quality in injectors (transverse
beam size and shape, bunch length, satellites,..)
BLM sunglasses
LHC Performance Workshop - Chamonix 2012
06/02/2012
Scraping in the SPS
K. Cornelis, Evian 2011
 Scraping studies showed the
importance of the scraping position. The
scraper has to cast a shadow on the
transfer line collimators. In this way even
large emittances can be transferred.
L. Drøsdal
LHC Performance Workshop - Chamonix 2012
Too high losses
in the SPS
%
Deeper scraping
 Just increase the scraping when there
are losses at LHC injection is rarely the
best solution
06/02/2012
Open TCDI Gap: Loss Shower on LHC BLMs for B1
W. Bartmann, Evian 2011
factor 4
Q8
MKI
Triplet
TDI
B1
LHC Performance Workshop - Chamonix 2012
06/02/2012
BLM Sunglasses
W. Bartmann, Evian 2011

Why sunglasses:
Unnecessary beam dumps due to TCDI and unbunched beam
showers from outside

Aim of sunglasses:
Factor 5 margin between injection losses and BLM thresholds
for comfortable operation

Options:


replace certain monitors by LICs and relax thresholds at 450 GeV
 no HW modification, certain thresholds constantly higher for 450
GeV (This year)
blind out BIS input from certain BLMs while injection via deploying
additional energy level, regrouping crates, new monitor flag
 need external signal, threshold change only at injection, severe
changes to SIS or BLM system (longer term???)
LHC Performance Workshop - Chamonix 2012
06/02/2012
BLM Sunglasses – LIC Solution
W. Bartmann, Evian 2011




Potential to increase thresholds by factor 60 by replacing
present ICs by LICs
No change to BIS system nor BLM firmware needed
List of monitors to be replaced for B1 and B2 identified
Procedure:




Replace certain monitors: 7 LICs will be installed before start-up
Start with present thresholds (be sure to be aware of bad
injections)
Define maximum thresholds for LICs
Apply increase of thresholds via monitor factor in case
unnecessary dumps limit operation
LHC Performance Workshop - Chamonix 2012
06/02/2012
TL Stability: Observation
L. Drøsdal, Evian 2011
LHC Performance Workshop - Chamonix 2012
06/02/2012
TL Stability: Observation
L. Drøsdal, Evian 2011
5 h later – same super cycle
composition  Trajectory has changed
 Necessary to re-steer the line
•
Tight transfer line collimators – high losses if trajectory not centered (17
dumps for B1 and 10 for B2)
•
Injection oscillations have to be below 1.5 mm to respect available aperture
in the LHC
LHC Performance Workshop - Chamonix 2012
06/02/2012
TL Stability: Observation
L. Drøsdal, Evian 2011
5 h later – same super cycle
composition  Trajectory has changed
 Necessary to re-steer the line
•
Beginning of run: ~ twice a week
•
End of run: every second day
•
Frequently the same corrector proposed (TI 2: RCIBH.20804, in phase with MSE/MST)
•
Offsets drifting back and forth
•
Dependence on SPS supercycle?
LHC Performance Workshop - Chamonix 2012
06/02/2012
Shot-by-shot Stability Studies
L. Drøsdal, Evian 2011

Dedicated periods of repeated
extractions on downstream TEDs
with 12 bunches for study of
shot-by-shot variations

TI 2: 82 Shots, 19 June
•
Horizontal plane: max 760 mm
•
Vertical plane: max 260 mm

TI 8: 117 Shots, 2 November
•
Horizontal plane: max 770 mm
•
Vertical plane: max 260 mm
760 mm
 used data in Model Independent Analysis to find
strongest Eigenmodes of oscillations
Shot-by-shot Variation Sources
L. Drøsdal, Evian 2011
TI2H- instability sources
LHC Performance Workshop - Chamonix 2012
TI8H- instability sources
06/02/2012
Shot-by-shot Variation Sources
L. Drøsdal, Evian 2011
TI2H- instability sources
TI8H- instability sources
Observed variations in the magnet currents:
•
•
•
Observed MSE variations are large enough to produce this oscillation
MST is not strong enough
MKE variations still to be investigated
MSE:
• Low inductance 20 kA circuit
• Power converter ripple was reduced from 18A to 9A  30% improvement
• Improvement by factor 2 in H still necessary for both lines (work ongoing)
LHC Performance Workshop - Chamonix 2012
06/02/2012
Bunch-by-Bunch Variations
L. Drøsdal, Evian 2011
Large bunch-by-bunch trajectory variations observed for TI 8 H –
seen on the bunch-by-bunch injection oscillation amplitudes
Plot from the IQC
B2, 144 bunches
Horizontal plane
Injection Oscillation
amplitude [mm]

Variation > 1mm (max)
Bunch ID
• Suspected too large ripple of the horizontal extraction kicker (MKE)
waveform
LHC Performance Workshop - Chamonix 2012
06/02/2012
MKE4 Waveform Scan
L. Drøsdal, Evian 2011
The MKE4 waveform shows a ripple varying up to 2.5% of kick (max. to min.) at the
flattop (4% at initial overshoot) - specification: 1 % flattop ripple!

Need to improve the MKE4 flat-top ripple (PFN)? - Only possible in LS1

Immediate action: change the delay to move the beam to a flatter part of the waveform
MKE4 waveform scan
4%
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
2.5%
SPS clock + 4.1us
56
55
54
53
52
51
50
49
48
47
46
45
% of votage

44
Kick delay usec
LHC Performance Workshop - Chamonix 2012
06/02/2012
Impact on Operation

Steering is complicated due to several effects:
L. Drøsdal, Evian 2011
Shot-by-shot variations
Need to average over several shots to correct trajectory
Bunch-by-bunch variations
When steering on 12 bunches (intermediate intensity) we only
sample a small part of the waveform – not representative for 144
bunches!
Difficult to optimize injection oscillations and trajectory at TCDIs at TI2 H
the same time
TI8 H
LHC orbit and transfer line
trajectory drifting apart
TI2 H
TI8 H
TI8 H
→In 2011: ~ 30 min – 2 h to steer (excluding some big outliers)
Estimate 2012 if stability is not improved:
1h steering × 0.5/days × 120 days = 60h!
Can we improve?
LHC Performance Workshop - Chamonix 2012
06/02/2012
Impact on Operation

Steering is complicated due to several effects:
L. Drøsdal, Evian 2011
Shot-by-shot variations
Need to average over several shots to correct trajectory
Bunch-by-bunch variations
When steering on 12 bunches (intermediate intensity) we only
sample a small part of the waveform – not representative for 144
bunches!
Difficult to optimize injection oscillations and trajectory at TCDIs at TI2 H
the same time
TI8 H
LHC orbit and transfer line
trajectory drifting apart




TI2 H
TI8 H
TI8 H
Reduce sources of instabilities (MSE ripple, adjust beam delay
wrt MKE waveform)
Time for setup during commissioning  new reference trajectory
Carefully monitoring beam quality in injectors  better detection
of bad beam quality early in the chain (longitudinally already well
covered by BQM, transv. can be improved)
Improve IQC references


Limits at TL BPM (MD to define them)  easier steering
Clear warning level at critical BLMs depending on number of bunches
injected (i.e. MSI ≥ 5% with 12 bunches  steering needed )
LHC Performance Workshop - Chamonix 2012
06/02/2012
MKI Flashover 18/04/2011
Beam was on LOWER TDI jaw and over-kicked, i.e.
breakdown in second half of magnet (LHCb signals
support this)

Nearly all p+ of the 36b impacted on the
TDI/TCLIB (grazing)  11 magnets quenched
B1 72b
B2 72b
B1 is causing the
vacuum pressure
rise in the B2
kicker – this is
not new
B1 72b
B2 72b

B1 72b
B2 72b
Injection of 2 × 36 bunches spaced by 2.2 ms
Breakdown after ~2 ms  All 36b of 2nd batch
were kicked with 110-125% nominal MKI deflection
B1 12b
B2 12b


MKI HW vacuum interlock reduced from 5e-8
mbar to 2e-8 mbar

New SIS to prevent injection if MKI pressure
>2e-9 mbar for 50 ns beam (temporary >2.5e-9
mbar for scrubbing with 25 ns beam)
New  P dt interlock implemented (Xmas stop)


Checked carefully TDI angular alignments in
IR2 and IR8
ALICE
Polarity
+
-


LHC Beam Operation Workshop
B1 left
[mrad]
-70
+86
B1 right
[mrad]
-750
-1035
B2 left
[mrad]
-190
-190
B2 right
[mrad]
-110
-110
TCLI openings  TCLIB to 8.3 s
Solenoids between MKI and Q4/A5 switched ON
Evian, 12/12/2011
IR2 MKI Erratics on 28/7/2011
Current in kicker magnet
M.J. Barnes
55000
MKI2. 28 July 2011, 6:03:09 PM
18:03:09
50000
MS-C
erratic
16:30:43
45000
2µs
4.5µs
Approx PFN Voltage
40000
Erratic turn-on
of MS-C
35000
30000
25000
20000
15000
10000
7/28/2011 6:03:09 PM PFN1
7/28/2011 6:03:09 PM PFN2
7/28/2011 6:03:09 PM PFN3
7/28/2011 6:03:09 PM PFN4
5000
0
Sample Number
Interlocks detected an erratic of the Main Switch of
MKI-C (MS-C) and correctly triggered MS’s and DS’s
of system (within 2µs), emptying PFN via both ends.
 Erratic of MKI2 MSC at 33kV during resonant
charging – sending current to one of the four
kicker magnets
Hence kicker-C pulsed for 6.5ms and 3 other
kicker magnets pulsed for up to 4.5µs, emptying
PFNs of energy.
 Interlocks did NOT detect erratic of MS-C:
hence no immediate action was taken to turn-on
other thyratrons  full 9 ms PFN pulse length
to kicker C.
 Circulating beam was not in IP2 and therefore
not disturbed.
 Batch was extracted from SPS but saw no kick at
MKI2 (current already back to zero in all 4 MKI
magnets) and went straight into the TDI upper jaw.
LHC Beam Operation Workshop
 Failure ~500µs into charging process:
extraction from SPS correctly inhibited;
Circulating beam was swept over aperture and
grazed TDI (~17% of normal kick) for ~8-9µs 
150-190 bunches
Evian, 12/12/2011
IR2 MKI Erratics on 28/7/2011
Current in kicker magnet
M.J. Barnes
55000
MKI2. 28 July 2011, 6:03:09 PM
18:03:09
50000
MS-C
erratic
16:30:43
45000
2µs
4.5µs
Approx PFN Voltage
40000
Erratic turn-on
of MKI2 MS-C
35000
30000
25000
20000
15000
10000
7/28/2011 6:03:09 PM PFN1
7/28/2011 6:03:09 PM PFN2
7/28/2011 6:03:09 PM PFN3
7/28/2011 6:03:09 PM PFN4
5000
0
Sample Number
Interlocks detected an erratic of the Main Switch of
 Erratic of MKI2 MSC at 33kV during resonant
173
- 2.15e13
p+ current
lost (not
dumped)
MKI-C (MS-C) and correctly triggered MS’s
and
DS’sbunchescharging
– sending
to one
of the four
of system (within 2µs), emptying PFN via both
ends.
kicker
magnets
 3 magnets quenched
 ALICE:
Hence kicker-C pulsed for 6.5ms and 3 other
kicker magnets pulsed for up to 4.5µs, emptying
Detector
PFNs of energy.
 Circulating beam was not in IP2 and therefore
not disturbed.
 Batch was extracted from SPS but saw no kick at
MKI2 (current already back to zero in all 4 MKI
magnets) and went straight into the TDI upper jaw.
LHC Beam Operation Workshop
 Interlocks
did NOT
detect
of MS3:
permanent
effects
on
the erratic
Silicon
Drift
hence no immediate action was taken to turn-on
other thyratrons  full 9 ms PFN pulse length
to kicker C.
 Failure ~500µs into charging process:
extraction from SPS correctly inhibited;
Circulating beam was swept over aperture and
grazed TDI (~17% of normal kick) for ~8-9µs 
150-190 bunches
Evian, 12/12/2011
IR2 MKI Erratics on 28/7/2011
Current in kicker magnet
M.J. Barnes
55000
MKI2. 28 July 2011, 6:03:09 PM
18:03:09
50000
MS-C
erratic
16:30:43
45000
2µs
4.5µs
Approx PFN Voltage
40000
Erratic turn-on
of MKI2 MS-C
35000
30000
25000
20000
15000
10000
7/28/2011 6:03:09 PM PFN1
7/28/2011 6:03:09 PM PFN2
7/28/2011 6:03:09 PM PFN3
7/28/2011 6:03:09 PM PFN4
5000
0
Sample Number
Interlocks detected an erratic of the Main Switch of
 Erratic of MKI2 MSC at 33kV during resonant
173
- 2.15e13
p+ current
lost (not
dumped)
MKI-C (MS-C) and correctly triggered MS’s
and
DS’sbunchescharging
– sending
to one
of the four
of system (within 2µs), emptying PFN via both
ends.
kicker
magnets
 3 magnets quenched
 ALICE:
Hence kicker-C pulsed for 6.5ms and 3 other
kicker magnets pulsed for up to 4.5µs, emptying
Detector
PFNs of energy.
 Circulating beam was not in IP2 and therefore
Hardware
not disturbed.
 Interlocks
did NOT
detect
of MS3:
permanent
effects
on
the erratic
Silicon
Drift
hence no immediate action was taken to turn-on
other thyratrons  full 9 ms PFN pulse length
to kicker C.
problem
 ~500µs
faulty into
components
exchanged
 Failure
charging process:
extraction from
SPS correctly
inhibited;
+ additional diagnostic
+ faster
detection
 Batch was extracted from SPS but sawelectronics
no kick at
with
lower voltage
threshold
no other
Circulating
beam was
swept over
aperture
and
MKI2 (current already back to zero in all 4 MKI
(~17% of
normal
kick)
for ~8-9µs 
in 2011grazed
BUTTDI
erratics
can
occur
several
magnets) and went straight into the TDI events
upper jaw.
150-190 bunches
times per year!!
LHC Beam Operation Workshop
Evian, 12/12/2011
IR2 MKI Erratics on 28/7/2011
Current in kicker magnet
M.J. Barnes
55000
MKI2. 28 July 2011, 6:03:09 PM
18:03:09
50000
MS-C
erratic
16:30:43
45000
2µs
4.5µs
Approx PFN Voltage
40000
Erratic turn-on
of MKI2 MS-C
35000
30000
25000
20000
15000
10000
7/28/2011 6:03:09 PM PFN1
7/28/2011 6:03:09 PM PFN2
7/28/2011 6:03:09 PM PFN3
7/28/2011 6:03:09 PM PFN4
5000
0
Sample Number
Interlocks detected an erratic of the Main Switch of
MKI-C (MS-C) and correctly triggered MS’s and DS’s
of system (within 2µs), emptying PFN via both ends.
 Erratic of MKI2 MSC at 33kV during resonant
charging – sending current to one of the four
kicker magnets
Hence kicker-C pulsed for 6.5ms and 3 other
Up to a
kicker magnets pulsed for up to 4.5µs, emptying
in future
PFNs of energy.
 Interlocks
did NOT detect
of MS3:
factor
of 2-4 higher
losseserratic
might
occur
hence no immediate action was taken to turn-on
years
(higher intensity and # bunches,
other thyratrons  full 9 ms PFN pulse length
worse impacttoparameter
at TDI)
kicker C.
 Circulating beam was not in IP2 and therefore
 OK for machine,
but
main
is safety for
 Failure
~500µs
intoconcern
charging process:
not disturbed.
ALICE/LHCb.extraction from SPS correctly inhibited;
 Batch was extracted from SPS but saw no
at
 kick
Detectors
must
be sufficiently
off during
Circulating
beam was swept
over aperture and
MKI2 (current already back to zero in all 4 MKI
grazed TDI (~17% of normal kick) for ~8-9µs 
injection!
magnets) and went straight into the TDI upper
jaw.
150-190 bunches
LHC Beam Operation Workshop
Evian, 12/12/2011
MKI Temperature Interlock
7.10E-07
2.780E-07
7.00E-07
2.760E-07
RISE_TIMEC(V(MagOut)*50kV/250,1.25k,23.75kV)
6.90E-07
2.740E-07
XVALUE_AT_YV(V(MagOut)*50k/250,12.5k)XVALUE_AT_YV(V(MagIn)*50k/250,12.5k)
6.80E-07
2.720E-07
6.70E-07
y = 3.79E-09x + 3.25E-07
R² = 1.00E+00
2.700E-07
6.60E-07
2.680E-07
6.50E-07
y = 7.39E-10x + 2.04E-07
R² = 9.98E-01
2.660E-07
6.40E-07
2.640E-07
6.30E-07
2.620E-07
6.20E-07
M.J. Barnes
2.600E-07
6.10E-07
2.580E-07
6.00E-07
100
97.5
95
92.5
90
87.5
85
82.5
80
77.5
75
During Xmas stop: new diagnostic to measure
delay (more sensitive, better time resolution of
kicker waveform)
2.800E-07
50% Delay (s)
Softstart (no beam)  measure rise-time 
indirect measurement of inductance
(temperature)
Predicted 5% to 95% rise-time versus magnet
Inductance
TMR Voltage Rise Time (s)
 Magnet inductance decreases when reducing
ferrite permeability  magnet strength decreases
 Rise-time decreases with reducing inductance
and/or capacitance
 Delay decreases with reducing inductance
and/or capacitance
Magnet Inductance Scale Value (%)
M.J. Barnes
MKI.UA87.IPOC.?B2:T_RISETIME (October 2011)
SIS interlock presently 62 ˚C (originally
55 ˚C ) cannot be further increased !
0.709
y = -1.325E-05x + 7.069E-01
R² = 1.501E-02
0.708
MKI.UA87.IPOC.AB2:T_RISETIME
0.707
MKI.UA87.IPOC.BB2:T_RISETIME
0.706
MKI.UA87.IPOC.CB2:T_RISETIME
Rise Time (µs)
0.705
MKI Temperature of up to 68 ˚C measured
during physics (10 hours time-constant for
ferrite heating and cooling)
MKI.UA87.IPOC.DB2:T_RISETIME
0.704
0.703
y = -7.324E-05x + 7.041E-01
R² = 7.792E-01
0.702
0.701
0.7
0.699
0.698
y = -2.828E-04x + 7.153E-01
R² = 6.809E-01
y = -3.563E-05x + 7.004E-01
R² = 8.375E-01
0.697
y = -2.065E-05x + 6.970E-01
R² = 3.514E-01
0.696
0.695
20.00
25.00
30.00
35.00
40.00
45.00
50.00
55.00
LHC Beam OperationMKI8
Workshop
Measured Temperature (˚C)
60.00
65.00
70.00
 Soft-start: OK  injection
not Ok  wait for MKI cooling
 24 stripes under investigation for
installation during TS in August 2012.
Evian, 12/12/2011
Other Issues Related to Injection System

UFOs at MKI  several beam dumps at the beginning of the
run (T. Baer’s talk, S07 Thursday )

TDI:

Controls problem TDI in IR2: settings different from measured motor
position and drift of the position reading triggered by electromagnetic noise

Heating Vacuum pressure increase at TDI in IR2 and IR8 when at parking
position (±20 mm)  High background in ALICE (shielding?)  new
parking position ±55 mm (E. Metral’s talk, S02 Monday)

Beam screen deformation discovered during Xmas Stop.
TDI IR8
25 mm
LHC Beam Operation Workshop
38 mm
Investigation on cause
and solutions ongoing!
Evian, 12/12/2011
Conclusions

Injection of 144 bunches fully operational: consistent/better than
predictions (some mitigations applied: scraping, TCDI at 5s, shielding,
injection and abort gap cleaning )

Successful injection of 288 bunches for both beams with losses at ~ 30%
from thresholds  promising (further mitigations available: new TCDI
locations, BLM sunglasses)

TL stability caused a lot of problems:



How to improve TL stability for 2012 operation:




Reduce MSE ripple and optimise delay beam/MKE
Dedicated time for setup during commissioning
Clearer references in IQC
Injection Failures:




Steering: tradeoff between minimum transverse losses (beam position at TCDI) and
injection oscillations  time consuming
big shot-by-shot (MSE) and bunch-by-bunch (MKE) variations
MKI flashover and erratics: magnets quenched, experiments affected…
Replaced faulty components, improved diagnostics, safer interlock limits.
MKI failures can occur several times per year (according to specifications)  respect
safety instruction, time for cooling and reconditioning, interlock limits and
experiment off
TDI heating and beam screen deformation: investigation ongoing to find
cause and short (before LS1) and long term solutions
LHC Performance Workshop - Chamonix 2012
06/02/2012
LHC Performance Workshop - Chamonix 2012
06/02/2012