Requirements of the LHC on its injectors What are the nominal & already achieved beams at PS exit?
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Transcript of Requirements of the LHC on its injectors What are the nominal & already achieved beams at PS exit?
1 february 2002 1
Requirements of the LHC on its injectors What are the nominal & already achieved beams at PS exit? How is it obtained in the PS complex?
General aspects PSB PS
LHC beam in 2001 Future work
THE LHC PROTON BEAM
E&G MétralE&G Métral
PS-OP shut-down lectures, 1/02/2002PS-OP shut-down lectures, 1/02/2002
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Requirements of the LHC on its injectorsRequirements of the LHC on its injectorsChoice of the nominal LHC parameters
Energy E [TeV]
7
Dipole field B [T]
8.3
Luminosity L [cm-2 s-1]
1034
Harmonic number h
35640
Number of bunches kb
2808
Protons / bunch Nb
1.11011
Bunch spacing b.s [ns]
25
x&y emittances 1norm,
,yx [m]3.75
Long. emittance 2l [eVs]
0.5 1
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LHC project leader L. Evans
Requirements of the LHC on its injectorsRequirements of the LHC on its injectors
Major upgrade needed all along the injector chain
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What are the nominal & already achieved beams at PS exit?What are the nominal & already achieved beams at PS exit?
The specifications are met in the PS complex
Achieved Nominal Energy E [GeV]
25 25
Harmonic number h
84 84
Number of bunches kb
72 72
Protons / bunch Nb
1.11011 1.11011
Bunch spacing b.s [ns]
25 25
x&y emittances 1norm,
,yx [m]2.5 3
Long. emittance 2l [eVs]
0.35 0.35
Total bunch length b [ns]
4 4
Momentum spread 2p/p
2.210-3 2.210-3
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How is it obtained in the PS complex?How is it obtained in the PS complex?General aspectsGeneral aspects
Main challenges High brightness & very short bunches
Solutions
Double-batch filling of the PS Lowers the space charge effects at PSB Increase of the PS injection energy Lowers the space charge effects at PS
injection
Multi splittings => bunch number, bunch spacing & emittance
Bunch rotation to produce the desired bunch length
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PSB PSB General aspects for PSB
2 consecutive cycles (LHC, TSTLHC) 1 bunch per ring (H1)
Different possibility to fill the 6 buckets of the PS
2 PSB rings + 4 PSB rings, 2 times 3 PSB rings, 4 PSB rings + 2 PSB rings Multi-turn injection : 3 turns exactly (for homogeneous longitudinal distribution) Special tune due to large tune shift
Double harmonics operation (bunch flattening) => decreases the space charge tune shift at injection
Available controlled blow-up C16 (H9) No coupling between the transverse planes
Standard settings of multipoles for resonance compensations
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Synchronization Non-standard bunch spacing at ejection to fit the PS H7 RF system
Adjustment with the phase offsets : BAx.PSYNCOFFSET (ring 3 is always used as the reference) Remember that the Timing used in that process is in H8
more difficulties to adjust the timing for the synchronization & for the instrumentation
Ejection at 1.4 GeV fast extraction towards the PS through the BT/BTP transfer line
ns3277
22907
t 7h TrevPSPS
C805Transfer PSB PSTransfer PSB PS
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Achieved Nominal Protons / bunch 12104.1 121032.1
Hor. emittance 1norm,
x [m] 2.2 5.2
Ver. Emittance 1norm,
y [m] 8.1 5.2
Long. emittance 2l [eVs]
1.4 5.1
Tot. bunch length
b [ns] 195 195
Momentum spread pp /2 (10-3)
2.2 45.2
PSB PSB Beam parameters at PSB extraction
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PS PS General aspects
Double-batch injection : separated by 1.2 s 6 bunches out of 7 buckets Longitudinal beam slicing complicated RF gymnastics
High brightness conservation careful control of collective effects, injection oscillations, working point, chromaticity, non-linearity at extraction…
PSB exit
PS exit
~ 300 ns
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At low energy 1st injection => 2 or 3 bunches (H7)
Transverse matching between PSB and PS, orbit correction... RF phase adjustment (PA.PDISC-H7)
adjusted from the CB if the PSB extraction phase is correct Working point during the long flat-bottom Qh ~ 6.21 and Qv ~ 6.23 RMS current on low energy power supply
2nd injection => 3 or 4 bunches (after the first batch ) Momentum adaptation PSB-PS => PSB synchro. made with PS beam
Same frequency sent to the PSB for the same MRP as the first injection one & same PS magnetic field
RF phase adjustment (PA.PDISC-H7)
Inj42 at C170
Inj42 at C1370
PS 1.4 GeV kinetic energy PS 1.4 GeV kinetic energy
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Time (20 ns/div)
R signal
Beam-Position Monitor(20 revolutions superimposed)
6m
)10(Intensity 10
[ms]Time
Head-Tail resistive-wall instability
A33.0skewI
A4.0skewI
PS 1.4 GeV kinetic energy PS 1.4 GeV kinetic energy
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PS PS
Remember that theTiming of the second injection
can also be adjusted by the Timing_f_t program
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1.4 Gev after second injection Triple splitting
6 × 3 = 18 bunchesH7 to H21
PS 1.4 GeV kinetic energy PS 1.4 GeV kinetic energy
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At transition : -jump + change of the chromaticity sign
Longitudinal coupled-bunch instabilities between 6 and 20 GeV/c cured by controlled longitudinal blow-up
From 20 to 26 GeV/c, horizontal orbit correction => PR.GSDHZ15,60-OC
At high energy (26 GeV/c momentum) Synchronization H1 => the worst 1st double splitting => 18 × 2 = 36 bunches (H42) 2nd double splitting => 36 × 2 = 72 bunches (H84)
1cavity 20MHz
1 cavity 40MHz
Cavities 200MHz
PS Acceleration PS Acceleration C1563
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Orbit correction during the Bump New ABS interface with virtual GFAs
Bump compensation in the RF phase loop system Without, the phase loop is not strong enough
Bunch compression by a step voltage => longitudinal mismatch
=> bunch rotation and ejection after 1/4 of synchrotron period
Ejection at 26 GeV/c fast extraction towards the SPS through the TT2/TT10 transfer line
eVs35.0lns16b ns4b with
Ej 16 at C2395
PS ejectionPS ejection
1 cavity 40 MHz (H84)2 cavities 80 MHz
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-100
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100 600 1100 1600 2100Time [ms]
prot
ons
nbr
(e10
)
-1000
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Gau
ss
I [e10]B [Gauss]
PS PS Inj at C169.8 Inj2 at C1369.8
1011Gauss at C160 B up at C1450 12576Gauss at C2120
Ej at C2395
Transition at C1563
Triple split. C1375 =>C1400
Blow up1 C1400=>C1440
Blow up2 C1725=>C1825
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0
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13000
B(G
auss
)V gp4V gp5V C20V C40V C80b
PS PS
Start firstDouble split.
Start cavity 20MHzC2258
End cavity 10MhzStart cavity 40mhz
C2338
Start sync SPSSynchro H1
PAX.SD1SYNCSPS C2155 Start PL H42
C2318
Lock of a frequency source
on the BEAMPAX.SSYNCH1INT
C2141
Ej at C2395
End cavity 20MhzStart GFA cavity 80mhz
C2388
Start PL H84C2363 Start fine sync
Synchro H21PAX.SD2SYNCSPS
C2365
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PS PS
Start of the bunch rotation process
Synchro with The extraction
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0
50
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2380 2382 2384 2386 2388 2390 2392 2394 2396
V C20V C40V C80
PS PS Ej at C2395
End cavity 20MhzStart GFA cavity 80mhz
C2388Start cavity 80mhz
~ ej –100us
Start of the bump16Start of PA.GSCOMP-BSW16
Ej –7.5ms = C2387.5 External restart For
PA.GSV40 & PA.GSV80By PAX.SBRH84
Ej –5.3ms = C2389.7
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PS RF signals during extraction process
Phase discri H21
Phase discri H42
Other important signals on NAOS
PA.PDISC-H84
PA.SYNCDISC-H21
PA.GSCOMP-BSW16
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ns/div300
ns/div30
ns/div1
PS PS Longitudinal beam structure in the last turn of the PS
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Only 1 measurement is still missing the transverse emittances in TT2 in the presence of bunch rotation
H - plane V - plane
Emittance measurements using the Semfils in TT2 without bunch rotation
PS PS
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Without solenoid
With solenoid~ 50-100 G
Also observed in the PS
Apparently the beam is not affected this is only a measurement problem for the PS (contrary to the SPS and LHC)
PS PS Baseline drift on electrostatic pick-ups in TT2
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This cycle is repeated 12 times for each LHC ring. 3 or 4-batch cycles will be interleaved in the form 334 334 334 333 to fill each ring with a total of 2808 bunches. The LHC filling time will be 12 21.6 s = 4.3 minutes per ring
SPS and LHC fillingSPS and LHC filling
LHC Proton Injection Cycle (21.6 s)
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SPS and LHC fillingSPS and LHC filling
Bunch disposition in the LHC, SPS and PS
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LHC Beam in 2001LHC Beam in 2001
Blow up on the PSB machine Better low energy process in the PS machine
New synchronization at extraction implemented Bunch stability better than 0.5ns at ejection (only measurable in CB)
Better splitting at 26GeV/c (phase loop) Bunch to bunch intensity fluctuations <10% as required
Coupling measurements at different energies H/V coupling at transition (tune crossing) H/V coupling at 26GeV/c
50 ns bunch spacing done Ultimate beam done
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LHC Beam in 2002LHC Beam in 2002
New B train (at the start up) Magnetic cycle to be reviewed LHC beam must be the first operation
Working point at low energy Suppress the ripple on the PFW GFAs
TTSM (type EPTTSM) to monitor the phase stability at extraction
Test of a fast LHC cycle in the PS
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Fast LHC cycleFast LHC cycle2.4 s - 26 GeV/c cycle for double-batch injection in the PS
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14000
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time [ms]
Mag
netic
fiel
d [G
auss
]
B newB Actuel
end of cycleC2370
2nd inj C840
1st injC160
end of cycleC2350
2nd inj C1370
1st injC170
eject C2395
eject C1710
26 GeV/c flat-top240ms (-15ms)
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To find documentationTo find documentation This file
N:\Psop\Doc\PS\Presentation\LHCBeam2002.ppt
All the MD measurements N:\Psop\Archives\data\PS\&MDs\Lhc
Beam reference on the WEB http://srv1ps/psop/cps/BeamRef/lhc/