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

1 february 2002 2

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

1 february 2002 3

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

1 february 2002 4

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

1 february 2002 5

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

1 february 2002 6

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

1 february 2002 7

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

1 february 2002 8

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

1 february 2002 9

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

1 february 2002 10

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

1 february 2002 11

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

1 february 2002 12

PS PS

Remember that theTiming of the second injection

can also be adjusted by the Timing_f_t program

1 february 2002 13

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

1 february 2002 14

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

1 february 2002 15

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

1 february 2002 16

-100

0

100

200

300

400

500

600

700

800

900

1000

100 600 1100 1600 2100Time [ms]

prot

ons

nbr

(e10

)

-1000

1000

3000

5000

7000

9000

11000

13000

15000

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

1 february 2002 17

0

50

100

150

200

250

300

350

2000 2050 2100 2150 2200 2250 2300 2350 240010000

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

1 february 2002 18

PS PS

Start of the bunch rotation process

Synchro with The extraction

1 february 2002 19

0

50

100

150

200

250

300

350

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

1 february 2002 20

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

1 february 2002 21

ns/div300

ns/div30

ns/div1

PS PS Longitudinal beam structure in the last turn of the PS

1 february 2002 22

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

1 february 2002 23

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

1 february 2002 24

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)

1 february 2002 25

SPS and LHC fillingSPS and LHC filling

Bunch disposition in the LHC, SPS and PS

1 february 2002 26

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

1 february 2002 27

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

1 february 2002 28

Fast LHC cycleFast LHC cycle2.4 s - 26 GeV/c cycle for double-batch injection in the PS

0

2000

4000

6000

8000

10000

12000

14000

0 1200 2400 3600

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)

1 february 2002 29

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/