Elias Metral, SSWG meeting, 21/11/2000

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Nominal PS beam for the future LHC Electron cloud build-up visible on electrostatic pick-ups

Effect of a solenoidal field Effect of a gap in the bunch train Simulations by F. Zimmermann Next studies

OBSERVATIONS OF ELECTRON CLOUD

BUILD-UP IN THE CERN PS

R. Cappi, E. Metral, G. Metral, M. R. Cappi, E. Metral, G. Metral, M. GiovannozziGiovannozzi

SPS Studies Working Group meetingSPS Studies Working Group meeting

Elias Metral, SSWG meeting, 21/11/2000

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Nominal PS beam for the furture LHC (1/6) Nominal PS beam for the furture LHC (1/6)

-100

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100 600 1100 1600 2100

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I [e10]

B [Gauss]

inj1 +10msC180

inj2 -10msC1360

inj2 +5msC1375

ej -6msC2389

Magnetic field and double-batch injection

Elias Metral, SSWG meeting, 21/11/2000

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Nominal PS beam for the furture LHC (2/6) Nominal PS beam for the furture LHC (2/6)

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H54

H64

V75

V85

PSB TT2

inj1 +10msC180

inj2 - 10msC1360

inj2 + 5msC1375

ej - 6msC2389

Normalised transverse emittances at 1

without bunch rotation!

Elias Metral, SSWG meeting, 21/11/2000

4

Nominal PS beam for the furture LHC (3/6) Nominal PS beam for the furture LHC (3/6)

RF gymnastics

At low energy (1.4 GeV kinetic energy)

1st injection => 3 bunches (H7) 2nd injection => 3 bunches (H7) Triple splitting => 6 × 3 = 18 bunches (H21)

At high energy (26 GeV/c momentum)

1st double splitting => 18 × 2 = 36 bunches (H42)

2nd double splitting => 36 × 2 = 72 bunches (H84) with

Bunch rotation => 72 bunches (H84) with

=> 6 bunches (H7)

eVs35.0l

ns16bns4b

Elias Metral, SSWG meeting, 21/11/2000

5

Nominal PS beam for the furture LHC (4/6) Nominal PS beam for the furture LHC (4/6)

ns/div300

The 72 bunches at PS ejection

Elias Metral, SSWG meeting, 21/11/2000

6

Nominal PS beam for the furture LHC (5/6) Nominal PS beam for the furture LHC (5/6)

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

Elias Metral, SSWG meeting, 21/11/2000

7

Nominal PS beam for the furture LHC (6/6) Nominal PS beam for the furture LHC (6/6)

Emittance measurements using the Semfils in TT2 with bunch rotation

H - plane

=> Electrons are created ...

Elias Metral, SSWG meeting, 21/11/2000

8

Electron cloud build-up visible on electrostatic pick-ups Electron cloud build-up visible on electrostatic pick-ups (1/(1/55))

Nominal beam seen on the pick-up 208 in TT2

Without solenoid

With solenoid~ 50-100 G

cf. W. Hofle

Elias Metral, SSWG meeting, 21/11/2000

9

Electron cloud build-up visible on electrostatic pick-ups Electron cloud build-up visible on electrostatic pick-ups ((22//55))

Pick-up 208 in TT2 (with and without solenoid)

Pick-up 03 in the PS (in the last turns)

Elias Metral, SSWG meeting, 21/11/2000

10

Electron cloud build-up visible on electrostatic pick-ups Electron cloud build-up visible on electrostatic pick-ups ((33//55))

Nominal beam (but with 84 bunches) seen on the pick-up 208 in TT2

Without solenoid

With solenoid~ 50-100 G

Elias Metral, SSWG meeting, 21/11/2000

11

Electron cloud build-up visible on electrostatic pick-ups Electron cloud build-up visible on electrostatic pick-ups ((44//55))

Nominal beam (but with 84 bunches) seen on the pick-up 03 in the PS

=> No coupled-bunch instabilities...

Elias Metral, SSWG meeting, 21/11/2000

12

Electron cloud build-up visible on electrostatic pick-ups Electron cloud build-up visible on electrostatic pick-ups ((55//55))

Effect of a gap in the bunch train

=> Helpful as predicted (cf. Roberto’s pictures)

Simulations by F. Zimmermann

=> It predicts the electron cloud build-up in both the PS and TT2 (cf. Frank’s pictures)

Next studies

See if the beam becomes unstable at the end of TT2 (it does not seem to be the case according to recent SPS MDs)

Try to have a clean measurement of the transverse emittances in TT2 using the Semfils => capture of the e-...