ILC BDS Collimation Optimisation

and PLACET simulations

Adina Toader

School of Physics and Astronomy, University of Manchester

& Cockcroft Institute, Daresbury Laboratory

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Outline of talk

Introduction to collimation optimisation

PLACET

Introduction & Capabilities

Examples: CLIC BDS

Relevance to collimation

Results with PLACET

Future plans

Phase advance

2006e 2006e optimised

SP4-SPEX

x: 0.38

y: 0.59

x: 0.5

y: 1.0

SP4-IP x: 2.76

y: 2.34

x: 2.75

y: 3.25

2006e Original 2006e Optimised

matching quadrupoles

SP4

SPEX

SP2

• Use matching quadrupoles to restore correct phase advances between SP4, SPEX and IP.• Multiple solutions available. Choose solution with the best latticebandwidth.

Collimation Optimisation

Collimation Lattice Optimisation

• ILC BDS collimation performance not good compared to NLC

- phase advances not correct and bandwidth poor • Tighter apertures to compensate for poor performance increased wakefields, emittance dilution

• Adjust matching of collimation and final focus optics- open collimators to reduce wakefields

• MERLIN BDS halo tracking, “black” spoilers set at nominal collimation depth, uniform halo dimension 50% larger than nominal collimation depth.

• Clearly improved performance in new lattice.

Original 2006e Performance New Performance

Plot shows halo profile at Final Double Entrance.The black square is the nominal collimation depth (same population in both halos at FD).

2006e Optimised Performance Tracking Results

Collaborators

Prof Roger Barlow University of Manchester

Dr Adriana Bungau

Deepa Angal-Kalinin Daresbury Laboratory, ASTEC

Frank Jackson

Daniel Schulte CERN Geneva

Andrea Latina

Giovanni Rumolo

PLACET

Introduction & Capabilities:

• The program PLACET (Program for Linear Accelerator Correction Efficiency Tests) was initially developed by Daniel Schulte and currently updated by Andrea Latina (CERN) for CLIC (Compact Linear Collider).

• It is a tracking code for linear colliders which implements: wakefileds, synchrotron radiation emission, single or multibunch effects, lattice errors, ground motion, the earth’s magnetic field and beam jitter.

• Interfaced in PLACET there is GUINEA-PIG – a beam-beam interaction code to simulate beam-beam collisions and calculates the luminosity.

• WP1 BDS Lattice Design and Simulation • Began using PLACET as general tool for collimation-

related simulations• Recently used to complement collimation lattice

optimisation by Frank Jackson• Preliminary results with PLACET

Background

Example of PLACET tracking along the

CLIC BDS

Horizontal (left) and vertical (right) phase space portraits at theend of BDS including or not including the collimator wakefieldsin the tracking*.

CLIC Luminosity reduction curves versus vertical collimator offset*.

*EUROTeV-Report-2006-026

Relevance of PLACET to collimation optimisation

• Collimation modifications disturb lattice and may make luminosity more sensitive to errors in quadrupole strength and alignment.

• Can easily introduce quadrupole strength errors and offsetsto check luminosity sensitivity in PLACET.

Results with PLACET

Wakefield results: The y kick varies with the position along the

bunch - the tail is more affected than the head.

Plots show qualitative agreement with MERLIN.

Results with PLACET

Tracking original ILC2006e lattice: Plots of beam size at IP in x, x’, y, y’ agreeing with

designed values.

x y

y’x’

Future Plans

• Collimation optimisation led to improved halo trackingperformance. • Use PLACET to check optimised lattice sensitivity to magnet errors. • Also we can study the effect of the collimator wakefields.

• PLACET is useful to calculate the luminosity deterioration due to these effects.