B. Mikulec# A.Findlay - CERN...ThePSBLayout! Injection:#BIline! SeparatedbywallfromPS# zone!...

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


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


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)


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


View inside the PSB tunnel PSB Injection Region PSB section 12


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


PSB Injec)on – Ver)cal SpliAng (2) Action of BI.DIS Action of BI.SMV


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


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


Disadvantages: ☹  Emittance increases

with number of injected turns

☹  Important losses at septum blade

Linac4: New BI.DIS and BI.SMV


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


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)


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


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

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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


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!)


Examples for EmiRance Plots


•  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


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


� 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


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


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


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)


3"4"

2"1"

from 3"from 4"

from 2"t1"

from 1"

PSB Par)cle Transfer

! !


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


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


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???)



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B. Mikulec# A.Findlay - CERN...The*PSB*Layout! Injection:#BIline! SeparatedbywallfromPS# zone!...

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B. Mikulec# A.Findlay - CERN...ThePSBLayout! Injection:#BIline! SeparatedbywallfromPS# zone!...