CLIC Post-Collision LineEdda Gschwendtner, CERN

for the Post-Collision Working Group

Rob Appleby (CERN & Cockcroft Institute)Armen Apyan (CERN)Konrad Elsener (CERN)Arnaud Ferrari (Uppsala University)Mike Salt (Cockcroft Institute)Jan Uythoven (CERN)Volker Ziemann (Uppsala University)

E. Gschwendtner, CERN

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20mrad

detectorbeam1 beam2

dump dumppost-collision line

Post-Collision Line

E. Gschwendtner, CERN

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• e+e- collision creates disrupted beam– Huge energy spread, large x,y div in outgoing beam

total power of ~10MW

• High power divergent beamstrahlung photons– 2.2 photons/incoming e+e-

2.5 E12 photons/bunch train total power of ~4MW

• Coherent e+e- pairs– 5E8 e+e- pairs/bunchX 170kW opposite charge

• Incoherent e+e- pairs– 4.4E5 e+e- pairs/bunchX

78 W

disrupted beam at interaction point

Some Numbers

Coherent pairs

50 Hz repetition rate 156ns bunch train length3.7E9 e/bunch 312 bunches/pulse14MW beam power

E. Gschwendtner, CERN

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Conceptual DesignBaseline: vertical chicane with 2x4 dipoles

1. Separation by dipole magnets of the disrupted beam, beamstrahlung photons and particles with opposite sign from coherent pairs, from low energy tails

Short line to prevent the transverse beam size from growing too much Intermediate dumps and collimator systems

2. Back-bending region with dipoles to direct the beam onto the final dump Long line allowing non-colliding beam to grow to acceptable size

intermediate dump

side view

27.5m

67m

1.5m C-shape magnets

window-frame magnets

carbon based masks

ILC stylewater dump

4m 150m6m

R.B. Appleby, A. Ferrari, M.D. Salt and V. Ziemann, Phys. Rev. ST Accel. Beams 12 (2009) 021001.

E. Gschwendtner, CERN

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beamstrahlung photons

disrupted beam+ same sign coherent pairs

1.5 TeV

300 GeV

90 cm

4MW

10MW

Side view

Conceptual Design

Collided 1.5TeV Beam at 150m from IP

Disrupted beam

beamstrahlung

Right-sign coherent pairs

30mm rms

A. Ferrari, R. Appleby, M.D. Salt, V. Ziemann, PRST-AB 12, 021001 (2009)

Uncollided 1.5 TeV beam at 150m from IP:Spot size of 3mm2

E. Gschwendtner, CERN

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Critical Issues• Background to IP

PhD student at Cockcroft Institute, UK• Luminosity measurements

Project associate Fellow to come in summer

• Beam dump design– Window– Energy deposition and pressure in tank

• Magnet design– Beam blow-up at dump

• Tilted magnets• Kickers

E. Gschwendtner, CERN

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Baseline Dump Design1966: SLAC water based beam dump: 2.2MW2008: ILC 18 MW water dump

– Cylindrical vessel– Volume: 18m3

– Length: 10m– Diameter of 1.5m– Water pressure at 10bar (boils at 180C)

– Cu-window, 1mm thick, 30cm diameter

E. Gschwendtner, CERN

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Energy Deposition in the Beam Dump

Work ongoing/setting up to calculate:– Energy deposition calculations in windows, water, etc… (FLUKA)– Stress, heating, etc… (ANSYS)

– What is the impact on the beam-size?

Energy deposition (MeV/cm3) of an uncollided 1.5TeV electron beam.

A. Apyan

MeV/cm3

E. Gschwendtner, CERN

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Magnet Status

• Main issues– Design of magnets– Defocusing the beam

• (tilting the poles of C-shape magnets, gradient of ~10T/m)– Sweeping magnets

57.7cm < h < 153.1cm

Window-frame magnets45cm

75cm

C-shape magnets

B=0.8T

E. Gschwendtner, CERN

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Summary

Conceptual design exists.

Detailed studies: are ongoing

• Photon and neutron backgrounds at the IP• Beam dump studies of particle production and energy deposition

or need to be setup• Beam dump design• magnets design• beam blowup

E. Gschwendtner, CERN

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IntroductionParameter CLIC

Max. Center of Mass energy [GeV] 3000

Luminosity L99% [cm-2 sec-1] 2 1034

Bunch frequency [Hz] 50

Bunch spacing [ns] 0.5

# Particles per bunch 3.7 109

# Bunches per pulse 312

Bunch train length [s] 0.156

Beam power per beam [MW] 14

Bunch length [m] 44

Crossing angle [mrad] 20

Core beam size at IP horiz. x* [nm] 45

Core beam size at IP vertic. y* [nm] 0.9

E. Gschwendtner, CERN

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Particle distributions in beam dump

Undisrupted beam, 1.5 TeV beam

Primary electron showers in water, depositing energy and producing photons, neutrons (mainly photonuclear) (+ others). Work ongoing to extract the peak GeV/cc deposited to calculate delta-T per train

A. Apyan

PhotonPhoton NeutronNeutron