7 th December 2006 LHC Machine Advisory Committee Status & performance Status & performance of the LHC (proton) of the LHC (proton) Injector Complex Injector Complex G. Arduini – AB/ABP Contributions from: S. Baird, H. Burkhardt, L. Ducimetiere, E. Gaxiola, B. Goddard, K. Hanke, S. Hancock, E. Métral, B. Mikulec, F. Roncarolo, G. Rumolo, E. Shaposhnikova, R. Steerenberg, J. Tan, J. Wenninger, F. Zimmermann et al.
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Status & performance of the LHC (proton) Injector Complex
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7th December 2006 LHC Machine Advisory Committee
Status & performance of the Status & performance of the LHC (proton) Injector ComplexLHC (proton) Injector Complex
G. Arduini – AB/ABP
Contributions from: S. Baird, H. Burkhardt, L. Ducimetiere, E. Gaxiola, B. Goddard, K. Hanke, S.
Hancock, E. Métral, B. Mikulec, F. Roncarolo, G. Rumolo, E. Shaposhnikova, R. Steerenberg, J. Tan, J. Wenninger,
F. Zimmermann et al.
7th December 2006 LHC Machine Advisory Committee
OutlineOutline
The LHC Injector Complex: HW statusThe LHC beamsStatus of the Injector CommissioningPerformancePresent limitationsSummary and Conclusions
7th December 2006 LHC Machine Advisory Committee
The LHC Injector ComplexThe LHC Injector Complex The LHC Proton Injectors:
Upgrade of the PS-SPS Complex to as LHC injector is almost complete.
Installation of the elements for the SPS fast extraction of Beam 1 to TT60 during last SD.
Main remaining item is the installation of TI2 (April-Aug 2007).
7th December 2006 LHC Machine Advisory Committee
ConsolidationConsolidation
Important refurbishment program ongoing for the coils of the PS Main Magnets.– 26 during the 2004-2006 SD– 8 during the 2006-2007 SD– money available for
refurbishing ~50 magnets out of 100
7th December 2006 LHC Machine Advisory Committee
ConsolidationConsolidation
Renovation of the water manifolds of the SPS MBB-type dipoles produced by one of the manufacturers (255):– 75 dipoles during the SD
2006-2007– The rest in ~3 slots in future
machine shut-downs
7th December 2006 LHC Machine Advisory Committee
The LHC proton beam (25 and 75 The LHC proton beam (25 and 75 ns)ns) PSB@inj PSB@extr PS@inj PS@extr SPS@inj SPS@extr
Pilot and Commissioning beamsPilot and Commissioning beams
Production scheme reviewed in 2004 (h=1 instead of h=2 in PSB) it avoids “throwing away” a bunch/ring in the transfer from PSB to PS and it simplifies tuning of the PSB-PS transfer.
BeamNbunch
[1011p]
*H/V
[m]
L
[eV s]#bunches tb [ns]
Probe beam0.05-0.2
0.05< 1
<0.7\<0.7< 0.80.26
11
-
Pilot beam0.050.05
< 1<0.7-6\<0.7-14
<0.80.26
11
-
TOTEM/Commissioning beam
0.2-1.150.31.1
<3.50.95/0.85<1.8\<1.3
<0.80.40.4
1-4-161-4-16
525525
SPS @ 450 GeV/c
Controlled transverse emittance blow-up “pink noise” in the SPS TFB
7th December 2006 LHC Machine Advisory Committee
LHC beam - multibunch LHC beam - multibunch
SPS @ 450 GeV/c
Nominal longitudinal emittance (<0.8 eV.s) achieved in 2002
Improvement resulting from:– Fine synchronization of the injection kicker magnet kick waveforms
(not nominal) still marginal.
– Independent correction of the injection of each (of the 4) batch from PS
– Non-linear chromaticity correction at flat-bottom
Transverse emittance still marginal in the vertical plane
2003 (LHCMAC 12/7/04) 2004
H [m] 2.6 ± 0.5 3.0 ± 0.3
V [m] 4.0 ± 0.2 3.6 ± 0.3
LHC beam - 25 ns
7th December 2006 LHC Machine Advisory Committee
Beam Nbunch
[1011p]
*H/V
[m]
L
[eV s]
#b tb [ns]
Early -75ns 0.1-1.150.6
1.15
2.5\2.50.9±0.05\0.8±0.051.8±0.1\1.5±0.05
<0.80.60.6
1-6x41-4x24
75
Nominal 0.1-1.150.7
1.15
3.5\3.51.7\2
3.0±0.3\3.6±0.3
<0.80.60.6
1-6x121-4x72
25
LHC beam - multibunchLHC beam - multibunch
7th December 2006 LHC Machine Advisory Committee
PSB limitationsPSB limitations
Space Charge limits:– LHC beam brightness.
Feasible for the NOMINAL beam in spite of the margin required to account for losses in PS and SPS (dashed line). Difficult to meet for the ULTIMATE beam, in particular for ring 3
Minimizing the losses in the downstream machines is mandatory as well as understanding the behaviour of PSB ring 3.
TSTLHC
1
1.5
2
2.5
3
3.5
4
4.5
5
100 150 200 250 300
Nbunch [1010]
NO
RM
. HO
R. E
MIT
TA
NC
E [ m
] Ring 1Ring 2Ring 3Ring 4All rings - average
TSTLHC
1.5
2
2.5
3
3.5
4
100 150 200 250 300
Nbunch [1010]
NO
RM
. VE
RT
. EM
ITT
AN
CE
[m
]
Ring 1Ring 2Ring 3Ring 4All rings - average
7th December 2006 LHC Machine Advisory Committee
PS limitationsPS limitations
Losses mainly affecting more intense and/or shorter bunches probably related to space charge driven resonance trapping phenomena. Further optimization of the working point might reduce losses.
LHC beam in the PS
0
2
4
6
8
10
12
150 650 1150 1650 2150
TIME IN THE CYCLE [ms]
INT
EN
SIT
Y [
101
2 p
pp
]
0
5
10
15
20
25
30
p [
GeV
/c]
~1.31011 p/b - ~3% losses
0 500 1000 1500 20000
50
100
150
200
ns
kturns
7th December 2006 LHC Machine Advisory Committee
PS limitationsPS limitations In 2006 observed intermittently
single bunch and coupled bunch (mainly horizontal) instability
– Nth ~ 0.6-0.7x1011 p/bunch– Growth times: few tens of turns– Creating “holes” of at least 12
bunches along the batch increases the threshold
– Dependence on bunch length (stronger instability for shorter bunches)
Found a bad voltage calibration for one of the 40 MHz RF cavities (spare) used for high energy splitting and bunch rotation resulting in shorter bunch length
Bunch length differenceC40-77 or C40-78 at 100 KV and C80 at 0 KV
10
10.5
11
11.5
12
12.5
13
13.5
14
14.5
15
0 10 20 30 40 50 60 70
Bunch number [#]
Bun
ch le
ngth
[ns]
Average (C40-77)
Average (C40-78)Stable beam
Unstable beam
Hardware problem was understood and solved at the end of the run but it showed how little is the margin for operation with nominal beam.
7th December 2006 LHC Machine Advisory Committee
PS limitationsPS limitations Observations are consistent with e-cloud instability observed in
the past but only in a special mode of operation when the bunches where kept short (less than 10 ns) for several tens of ms
We need to build some margin (taking into account that we will have to open the machine vacuum in the future to continue the magnet renovation campaign – at least its first phase):– Review the RF gymnastics at high energy– Complete the commissioning of the transverse feedback– Add flexibility to the control of chromaticity by an independent
powering of the PS magnet pole-face windings (planned for 2007)
7th December 2006 LHC Machine Advisory Committee
SPS limitationsSPS limitations
Low energy losses: reduction from >10 to 7-8
%– New RF voltage
programme (end of 2003)– New working point
compatible with larger momentum spread (end of 2004) and large vertical chromaticity required to fight the ECI. Results confirmed in 2006.
Need to understand better the blow-up and loss mechanisms at the beginning of the ramp (mainly on the tail of the 4th batch). Data collected in 2006 being analyzed.
-14
-12
-10
-8
-6
-4
-2
0
0 5000 10000 15000 20000
TIME IN THE CYCLE [ms]
RE
LA
TIV
E L
OS
S [
%]
16/10/2003
02/07/2004
15/11/2004
NEW WP
INJ. PLATEAU RAMP
7th December 2006 LHC Machine Advisory Committee
SPS limitationsSPS limitations
Short lifetime even after optimization of the working point
“longitudinal” lifetime dominate (capture losses due to Re ZL and bunch shape) Impedance reduction and optimization of the bunch shape from PS
Difference in lifetime between the head and the tail of the batch
– recovers as the intensity decreases– Bunches are getting shorter particularly at
the tail of the batch …..while electron cloud signal disappears
E-cloud density variation during the bunch passage and synchrotron motion lead to periodic tune modulation and trapping-de-trapping on resonance islands halo and losses only cure so far: “scrubbing”
7th December 2006 LHC Machine Advisory Committee
SPS limitationsSPS limitations
Fast vertical instability observed since 2002 and studied in 2003-2004 for single LHC bunches with low longitudinal emittance (L~0.2 eV.s < L LHC
=0.35 eV.s) for Nb>0.6×1011 p Driven by the machine Ztr. Expect instability threshold close to the ultimate intensity for L LHC
Since 2002 a constant increase on the 800 MHz RF voltage required to stabilize the beam has been also observed due to increased Im ZL
0.05y 0.8y
7th December 2006 LHC Machine Advisory Committee
SPS limitationsSPS limitations
2006 results are preliminary
Significant contribution from the kickers (in particular extraction kickers).
7th December 2006 LHC Machine Advisory Committee
Interdigital comb structure 20mm spacing
SPS limitationsSPS limitations
Impedance reduction campaign for the extraction kickers started with a prototype module installed in the machine
Impedance measurements performed in the laboratory effect on beam stability being estimated before continuing with the programme
Plan to build an impedance DB for the SPS (....and ultimately for the injectors)
7th December 2006 LHC Machine Advisory Committee
Summary and ConclusionsSummary and Conclusions
From the point of view of the HW the LHC injectors are ready for the LHC and a consolidation programme is ongoing to allow them to serve reliably the LHC
The Commissioning and Early Physics Beams have been tested during machine studies and can be provided.
Need to turn their operation mode from occasional (MD/expert type) into routine during the 2007 run:– CCC is certainly an advantage– Need to improve beam diagnostics signals/data availability and
reliability (particularly lacking in 2006) in CCC and control tools
7th December 2006 LHC Machine Advisory Committee
Summary and ConclusionsSummary and Conclusions
Nominal beam is feasible but we have to create more margin for a reliable operation in PS and particularly in the SPS where e-cloud together with impedance are the main limitations.
Operation above nominal is for the time being out of range and likely requires a more drastic upgrade programme of the injectors.