A. Findlay
B. Mikulec
Introduc)on � The PSB within the CERN accelerator complex � Injection � PSB beam types � Adjusting the intensity and transverse parameters � PSB dynamic working point � Extraction and beam transfer to PS and ISOLDE � What will be new in 2011?
� Covered by A. Findlay: capture, acceleration, longitudinal parameters and synchronisation
09.02.2011 OP lectures 2
The PSB within the PS Complex
09.02.2011 OP lectures 3
PSB Injec)on – Transfer from Linac2
� Linac2 (source, RFQ, 3 accelerating tanks) à LT line until LT.BHZ30 à LTB line until LTB.BHZ40 à BI line
� Linac4 will reuse the transfer lines downstream of LT.BHZ20
09.02.2011 OP lectures 4
Linac2 LT.BHZ10
LTE
LTL
LBE
LBS
LT.BHZ20
LT.BHZ30 LTB.BHZ40
PS Booster
To PS and ISOLDE
LT line BI line LTB line
The PSB Layout � Injection: BI line
� Separated by wall from PS zone
� Splitting of Linac2 beam into 4 vertical levels
� Inject in PSB section 16/1 � PSB ring divided into 16 sections
� Extraction from section 15 and recombination: BT line
� Beam transfer: BTM+BTY lines (to ISOLDE) and BTP line (to PS)
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bât.361
The Basic PSB Sec)on
� Above example: PSB section 6 | L1 | Bend1 |L2|QFO|L3| QDE | L4 |QFO|L5| Bend2 |
� 5 straight sub-‐sections (space for equipment in L1, L3 and L4) � PSB lattice: 0.5D – L4 – F – L5 – B – L1 – B – L2 – F – L3 – 0.5D
� QFO (focusing quadrupole): magnetic length ~0.50 m � QDE (defocusing quadrupole): magnetic length ~0.88 m
09.02.2011 OP lectures 6
View inside the PSB tunnel PSB Injection Region PSB section 12
09.02.2011 OP lectures 7
PSB Injec)on – Ver)cal SpliAng (1) � Linac2 continuous pulse has to be split into 4 superimposed PSB rings (36 cm vertical distance) � Aim of 4 rings: reduced direct space charge effects to limit losses for high intensity beams
� Distributor BI.DIS � Separate beams
� Septum BI.SMV � Increase separation
� Bending BI.BVT � Cancel angle
09.02.2011 OP lectures 8
PSB Injec)on – Ver)cal SpliAng (2) Action of BI.DIS Action of BI.SMV
09.02.2011 OP lectures 9
No kick: head dump Kicks 0-‐1-‐2-‐3: inject into rings 4-‐3-‐2-‐1 Kick 4: tail dump
BI.DVT40 and BI.SMV increase separation angle
PSB Mul)-‐Turn Injec)on � Injection of up to equivalent of 13 Linac2 turns
� The number of turns acts on the Linac2 pulse length and the distributor timing
� Use 4 slow kickers (BIi.KSW in sections 16L4, 1L1, 1L4 and 2L1) and the horizontal septum BI.SMH1L1 � To create an injection bump of the circulating beam � To change the angle and bring injected beam onto orbit
09.02.2011 OP lectures 10
Mind! ☝ Playing with
BIXi.SKSWPR has an influence on the transverse emittance!
Principle of Mul)-‐Turn Injec)on � Goal: find optimum between a brilliant beam and low space-‐charge effects by filling uniformly acceptance � Horizontal tune at injection: ~4.28 (beam ellipse advances by slightly more than 90° per turn)
� Add horizontal movement due to slow kickers
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Disadvantages: ☹ Emittance increases
with number of injected turns
☹ Important losses at septum blade
Linac4: New BI.DIS and BI.SMV
09.02.2011 OP lectures 12
Linac4: H-‐ Charge-‐Exchange Injec)on
� Need stripping foil + internal dump � Slow chicane bump with 4 new
magnets � Superimpose faster painting bump
(BIi.KSW) for offset and to limit space-‐charge effects for high intensities 09.02.2011 OP lectures 13
0 340 1072 1329 1587 2319 2654
0
20
40
60
80
100
120
140
160
Drift Space [mm]
Ampl
itude
[mm
]
PSB Injection Geometry for 380mm magnets, 350mm magnetic length, 66mrad, 359mT, 126mTm
32
151
125.7
Injection BumpH+ Beam
InjectedH- Beam
FoilStripping
DUMP
BS1 BS2 BS3 BS4
H0 80.3
H-
Stripping Foil Mechanism
4 new BIi.BSW
� Obtain very small transverse emittances as H-‐ beam from Linac4 and circulating p beam can overlap in phase space
� Transverse phase space painting
PSB Basic Beam Types � H1, h2, h2+1 beams à see Alan’s presentation � High intensity ISOLDE-‐type beams � CNGS, SFTPRO
� CT extracted or MTE type � LHC beams
� Single-‐bunch (LHCPROBE, LHCINDIV) � Multi-‐bunch LHC beams
� Single-‐ or double-‐batch PS transfer
� MD beams
09.02.2011 OP lectures 14
Intensity Regula)on (1) 1. Number of turns: modify injected intensity
� For ISOLDE beams, CNGS, SFTPRO, TOF, AD � Beware! Transverse emittance increase with intensity!
2. Transverse shaving (vertical shavers in 4L4, horizontal shavers in 10L4):
� Prefer vertical shaving for stability reasons � For EAST beams as well as lower intensity LHC25,
LHC50 and LHC75 � Corresponding emittance decreases! � Loose beam on beamscope window (8L2)
09.02.2011 OP lectures 15
Intensity Regula)on (2) 3. Longitudinal shaving: start capturing the beam with
low longitudinal acceptance; adiabatic acceptance increase (change vector 5 of C02 GFA function)
� For LHCPROBE, LHCINDIV
09.02.2011 OP lectures 16
Mind when changing the intensity! ☝ The emittance might change – think if
this is important for that beam and always choose the correct method!
☝ Losses might occur due to different space charge forces à very often the tune has to be readjusted with the Q-‐strips (see later) 0
2
4
6
8
10
0 50 100 150 200 250 300
! x +
!y (!
m)
[norm
.]
Np (x 1010
p)
LHC25 at PSB extraction, spread over the 4 rings
Adjus)ng Transverse EmiRances � Transverse emittances for a fixed intensity can be adjusted by � Tuning the injection:
� BIXi.SKSWPR: slow injection kicker timing (position of injection bump)
� Injection position and angle
� Approaching a resonance line to increase emittance
09.02.2011 OP lectures 17
Transverse EmiRance Measurements � In the rings during the acceleration cycle:
� Beamscope (very rarely used; destructive method): associated dipoles have to be enabled before
� Fast wire scanners (1 per plane per ring) � In the BTM line after extraction:
� SEM grids (3 grids needed to measure emittance) � Remark: different optics (quadrupole settings) are automatically set for each measurement plane (can get stuck in this process leading to losses for normal beam transfer!)
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Examples for EmiRance Plots
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• 1σ normalised emittance • Adjust filter+gain for FWS • Adjust gain for SEM grids and remove
broken channels Don’t forget to enter correct Δp/p from tomoscope for horizontal measurement!
PSB Dynamic Working Point � High intensity beams:
� Inject at Qv~4.65, Qh~4.29
� Extract at Qv~4.20, Qh~4.19
� Lower intensity beams: � Reduce vertical working point below half-‐integer
� Same extraction working point
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Tune measurement with sampler (mostly for programmed tune) or with BBQ system
Working Point and Resonances
4 4.2 4.4 4.6 4.8 5
4
4.2
4.4
4.6
4.8
5
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� Have to avoid destructive resonances
� Tune spread (space charge!) highest at low energy � Use Q-‐strips ~during first 200 ms after injection to minimise losses
� Throughout cycle use multipoles to compensate resonance effects (losses)
PSB resonances up to 4th order; Red: systematic resonances (PSB superperiodicity) Solid blue: normal resonances Dashed blue: skew resonances
PSB Main Power Supply (MPS) � MPS supplies main bendings
and quadrupoles � Trim1+4 power supply for
bendings to compensate for field difference in outer rings � GFA increases with energy
� Q-‐strips (QCF and QCD): additional power supply to tweak tune after injection � GFA during ~first 200 ms
� SBDL: extra windings for bendings per ring to fine-‐tune B-‐field (frequency) � Used mainly at extraction
after synchronisation
09.02.2011 OP lectures 22
MIND: All these GFAs start at 105 ms and not at 0 ms!!!
Beam Extrac)on � Generate horizontal ejection bump using BE.BSW (installed in 14L4, 15L1 and 15L4)
� Kick the beam out of the rings with fast kicker BEi.KFA14L1 such that it gets deflected by extraction septum BE.SMH15L1
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BE.KFA14L1" BE.BSW14L4"
orbit without "bump"
BE.BSW15L1"
ejection bump"septum"BE.SMH15L1" extracted beam"
Beam Recombina)on � Beam recombination in BT line
� Destinations: PS / BTM line / ISOLDE GPS or HRS � Ring extraction in the order: 3 – 4 – 2 – 1
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R1
R4
R3
R2
S
Y
X
Bending
BVT
BVT
BVT
Septum
SMV
SMV
SMV
Kicker
Correct Recombina)on � Check OASIS signals! (pick-‐ups and kicker)
!09.02.2011 OP lectures 25
Bunch Distance � 8 equidistant bunches with Δt=286.4 ns (79 m) to fill PS @ h=8 (double for h1 beams)
� For LHC multi-‐bunch beams Δt=327 ns to fill PS @ h=7 (1 bucket empty) � Add h1 voltage in PSB to increase spacing (h2+h1 scheme)
09.02.2011 OP lectures 26
3"4"
2"1"
from 3"from 4"
from 2"t1"
from 1"
PSB Par)cle Transfer
! !
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Clients: PS and ISOLDE Additional destination: BDUMP
VERY Rough Summary � The PSB is a unique accelerator made of 4 rings
� It’s total circumference is equal to the PS � Some controls are common to all 4 rings, others are individual or for 2 rings
� Multi-‐turn injection spreads the beam in phase space, but influences the transverse emittance
� Available beam instrumentation should be used extensively (with proper setting up) and the beam characteristics surveyed on a regular basis
� Multitude of beams; at limit with 24 users
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Outlook 2011 Opera)on � The LHC will be very demanding in terms of fast response to requested changes and beam quality
� But there are also all our other clients deserving equal attention
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What Will be New in the Future? 2011 2012 and later
� INCA � Deployment ~June
� 3 corrector dipoles per ring and plane (24 in total) under FGC3 control (3L4, 8L1 and 16L1)
� Orbit correction with these dipoles using YASP
� ABS with YASP � All 3 points: summer?
� Multipole renovation (FGC3) � Connection with Linac4 in 2013/2014??? � Change injection region � Commissioning of all beams
� PSB 2 GeV Upgrade?? (2018???)
09.02.2011 OP lectures 30
09.02.2011 OP lectures 31