Simulations for LEP3/TLEP Marco Zanetti (MIT) 1 Introduction - - PowerPoint PPT Presentation

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Simulations for LEP3/TLEP

Marco Zanetti (MIT)

• Beams are squeezed at the IP to push for high luminosity.
• Similar to ILC but in this case beams cannot be disrupted after

the collision.

• Beamstrahlung effects must be mild enough to allow a

reasonable lifetime

– At least larger than burn-out lifetime

• Additional key ingredient is the enhanced momentum

acceptance

– we aim at 4% (by increasing RF voltage)

• LEP3/TLEP parameters already chosen accordingly to

analytical formulation and full beam-beam simulation

– V. Telnov, http://arxiv.org/abs/1203.6563, based on analytic formulation of the problem – MZ at 1st LEP3 workshop, http://tinyurl.com/8lzdad2

Introduction

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• Analytic functional form (red in the plot):
• Constants not checked yet

Simulation – Analytic form

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• BS lifetime results (TLEP)
• Luminosity profile
• Power dissipation
• Multi-turn simulation

Outlook

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Lifetime>4h h=3%

• Single crossing guinea-pig based simulation

– Simulate 360M macroparticles around the working point

• Lifetime features exponential dependency on energy

acceptance

Energy spectrum

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TLEP-T TLEP-H

• As for LEP3, TLEP BS lifetime well above required threshold
• In particular some margin (x2 ?) is there for TLEP-H

• Look at the how much luminosity is delivered within 1% of

nominal √s (L0.01)

– Key quantities for Physics – ISR not included, single crossing simulation

• Beamstrahlung effects much smaller than at ILC
• Almost monochromatic luminosity profile

– Very similar performances for all circular collider options

• To be confirmed by multi-turn simulation

Luminosity profile

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• The photon flux could be problematic for machine and

detector instrumentation

• Run the simulation to estimate the photon rate and energy
• Use that to compute how much power is dissipated as a

function of the polar angle

Power dissipation

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LEP3

• Similar dissipation for LEP3 and TLEP (O(10) kW integrated)
• Should be manageable, most of the power dissipated at very

small angle

– No harm to experiments – Beam pipe needs protection – Flux on quadrupoles rather limited

Power dissipation

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TLEP

• Goal is to check the beam parameters at equilibrium

– Assume TLEP-H parameters

• Integrate beam-beam simulation with simple longitudinal and

transverse dynamics

• Transverse motion:

– Qx,Qy>0.5

• Synchrotron motion:
• Radiation damping:

Multi-turn simulation

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H plane: effect of collision

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• A correlation is introduced

– Linear in the bulk, non-linear in the tails

• Correct it by means of a rotation matrix (quad):

– a determined empirically from the fit of the bulk

H plane: effect of correlation

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Colliding once and then transporting the beams around w/o further collision (divergent otherwise)

H plane: compensating correlation

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• Collide only once, then transport
• Correct right after the collision
• Rotation of the tails not fully corrected

H plane: full simulation

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• Collide at every turn in 1 IP
• Still some beating

• Small correlation also here
• No compensation applied, still beam is not diverging

V plan: full simulation

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• Strong damping
• Not totally clear to me..

Z plane: full simulation

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• Analytic computation verified by simulation

– Very short lifetime for original beam parameters – Negligible effect on energy spread – Number of gammas <1 (0.6)

• First implementation of multi-pass simulation is encouraging

– Need to cope with large a in the H plane

• Long to do list:

– Understand/debug features – Compute relevant quantities at equilibrium – Implement 4 IPs – ..

Summary

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