Beam Delivery System Simulation and Detector Backgrounds

Takashi MaruyamaSLAC

Arlington Linear Collider Workshop January 9-11, 2003

“Collimation Task Force”

December 16 - 18, 2002

• Compare performance of the collimation system of TESLA, JLC/NLC and CLIC.

• Review spoiler/absorber settings

• Halo collimation

• Particle loss calculation

• Sync. radiation collimation

NLC: S. Hertzbach, L. Keller, T. Markiewicz,T. Maruyama, T. Raubenheimer, A. Seryi, P. Tennenbaum, M.

Woodley

TESLA: O. Napoly, N. Walker

CLIC: G. Blair, D. Schulte, F. Zimmermann

FNAL: A. Drozhdin, N. Mokhov

TRC: W. Kozanecki

December 16 – 18, 2002

Background and collimation

• Major source of detector background: Halo particles hitting beamline components generate muons and low energy particles.Halo particles generate sync. radiations that hit VXD.Beam-gas scattering generates low energy particles.

• Collimate Halo particles:Spoilers and AbsorbersCollimation depth – (nxx, nyy)

Reduce halo size using Octupoles• What is Halo, and How much: Drozhdin’s 1/x-1/y model

Flat distribution with 50x,50x’,200y,200y’,3%E/E

Calculated halo ~10-6, but design collimation for 10-3.

NLC Detector Masking Plan View w 20mrad X-angle

LD – 3 Tesla SD – 5 Tesla

32 mrad30 mrad

R=1 cm

Apertures: 1 cm beampipe at the IP 1 cm at Z = -350 cm

2001 Collimation System & FF integrated design

New scheme of the Collimation Section and Final Focus with ODs

Energy collimation

Betatroncollimation

Final Focus

IP FD IP FD IP

FD

S SA SA SA A

A

FDA

Final Focuscollimation

AIP

Octupole Doublets

Beam Delivery Systems

TESLA

JLC/NLC

CLIC

Synchrotron radiations

FF doublet aperture 1 cm

bendsquads

Photons from quads

Photons from bends

Sync. Radiation vs. IP

ny

nx

cm

xIP

yIP

Track particle with n• backward from IP to AB10.

Track particle to IP and generate sync. radiations.

Find sync. radiation edge as a function of (nx, ny). nx = 18.5 x+, 17.2 x-

ny = 50.9 y

Find AB10 and AB9 apertures as a function of (nx, ny)

Sync. Radiations at IP

X (cm)

Y

X (cm)

Log10(E) (GeV)

Quad

Bend

.3 Ne-

<E>=4.8 MeVQuad

Bend

Spoiler/Absorber Settings for NLC

Spoilers/Absorbers Settings for NO OCT

Half aperturesX Y (um) xy

Sp1 ~ SP4 settings with OCT x2.5

Spoiler/Absorber Settings

TESLA

CLIC

Halo ModelX’

X (cm) Y (cm)

Y’

10-5

y (cm)

x (cm)

1/x and 1/y density over

Ax = (6 – 16)x and

Ay = (24 – 73)y – NLC/CLIC

Ax = (7 – 18)x and

Ay = (40 – 120)y – TESLA

E/E = 1% (Gaussian)

Halo rate 10-3

Particle loss distribution in NLC

Z (m)

OCT-OFF

OCT-ON

42% to IP

82% to IP

ESP

EAB

AB10

AB7

DP2

Integral Particle Loss Distribution

Integral Particle Loss Distribution NLC/TESLA/CLIC

250 GeV/beam Muon Endcap Background

Engineer for 10-3 Halo

Bunch Train =1012

Calculated Halo is 10-6

CollimationEfficiency 105

Muon Background

Beam Gas Scattering

Detector Background from Beam Gas Scattering

At 50 nT, 8.5 hits/train within +/- 15 m of IP2.5 hits/train on 1.2 cm VXD.

If the vacuum is reduced to 1 nTin the last 250 m of IP,0.2 hits/train within +/- 15 m of IP0.05 hits/train on 1.2 cm VXD.

Summary

• “Collimation Task Force” has been studying the beam delivery system of TESLA, JLC/NLC and CLIC.

• FF absorbers are set so that no sync. radiations hit the detector apertures.

• Assuming 10-3 halo, the particle loss is < 10-8 in FF and the muon background is tolerable.

• Octuples allow x2.5 looser spoiler settings.• Beam gas background in VXD is 0.05 hits/train

if the vacuum is 1 nT.