initial beam-beam studies

1

Initial Beam-Beam studies

January 20, 2014

2

Contents

• The beam-beam code and the two parameter sets used.

• The beam-beam effects on the phase space of the proton beam.

• Effects of shifting the waist of the beam.• Effects on the spent beams.• Effects on the phase space of the spent

electron beam.

3

Beam code and Parameters• The code in use is Guinea pig, two versions are

used for the different simulations, the C version, guinea 1.4.4 and the c++ version guinea_pig++

Value Nominal Parameters

High Luminosity

Particle number (ion/electron) 1010 17/0.3 22/0.2

β* ion mm 100 50

β* electron mm 120 32

ϵx,y ion mm mr 3.75 2

ϵx,y electron mm mr 50 50

4

Transverse EffectsNominal High Luminosity

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Longitudinal Effects

Nominal High Luminosity

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Longitudinal Effects

7

Luminosity Measurements with Offsets

Nominal Parameters High Luminosity

Lum

inos

ity m

-2s-1

Horizontal Offset x/σ Horizontal Offset x/σ

Lum

inos

ity m

-2s-1

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Angles With Offsets (Protons)

Horizontal Offset x/σ Horizontal Offset x/σ

Mea

n An

gle

μr

Mea

n An

gle

μr

9

Angles With Offsets (Electrons)

Horizontal Offset x/σ Horizontal Offset x/σM

ean

Angl

e μr

Mea

n An

gle

μr

10

Trajectories with offsetsNominal Parameters High Luminosity

Head-on

1σ offset

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Luminosity Measurements with TrackingLu

min

osity

m-2

s-1

Turns x10Turns x10

Lum

inos

ity m

-2s-1

Turns x10 Turns x10

Nominal Parameters High Luminosity

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Induce an instability

Attempt to induce instability in recirculating proton beam by matching the electron beam to always hit with a set offset at the same section of the beam, based on the horizontal tune.

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Induced Instability

• Red= nominal without longitudinal motion• Green=nominal with longitudinal motion• Blue=HL without longitudinal motion• Purple=HL with longitudinal motion

Turn

Horiz

onta

l Pos

ition

m

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Induced Instability (cont’d)

Red lines indicate no longitudinal motion, green lines indicate longitudinal motion

Nominal Parameters High Luminosity

Turn Turn

Nor

mal

ized

Emitt

ance

Nor

mal

ized

Emitt

ance

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Waist ShiftsNominal Parameters High Luminosity

1.1% increase 18.7% increase

16

Waist Shifts Combined with OffsetsNominal Parameters High Luminosity

Wai

st S

hift

Wai

st S

hift

Offset Offset

17

Trajectories with offsets and waist shiftNominal Parameters High Luminosity

Head-on

1σ offset

30,000 μm

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Spent Electron BeamNominal Parameters High Luminosity

Red particles show the beam without beam-beam effects, green particles show the electron beam with beam-beam effects.

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Spent Electron Beam (At Max Luminosity Waist Shift 0.6 σz)

Nominal Parameters High Luminosity

Red particles show the beam without beam-beam effects, green particles show the electron beam with beam-beam effects.

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Conclusions

• The beam beam effects on the ion beam are rather small

• The beam beam effects on the electron beam are quite large

• The effects on the spent beam are of particular importance in the high luminosity parameter set

• Could have a nonlinear response to offsets

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Backup 1

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Backup 2

Horizontal Offset x/σ Horizontal Offset x/σ

STDE

V An

gle

μr

STDE

V An

gle

μr

23

Backup 3

Horizontal Offset x/σ Horizontal Offset x/σ

STDE

V An

gle

μr

STDE

V An

gle

μr