overview of clic bds
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Overview of CLIC BDS. Frank Zimmermann CLIC BDS Day 22.11.2005. BDS tasks. focus beams to nm spot size stably collide two beams deliver target luminosity dispose spent beam ensure adequate background conditions protect the machine against self-destruction preserve polarization - PowerPoint PPT PresentationTRANSCRIPT
Frank Zimmermann, CLIC BDS Day, 22.11.2005
Overview of CLIC BDS
Frank ZimmermannCLIC BDS Day 22.11.2005
Frank Zimmermann, CLIC BDS Day, 22.11.2005
BDS tasks• focus beams to nm spot size• stably collide two beams• deliver target luminosity• dispose spent beam• ensure adequate background conditions• protect the machine against self-destruction• preserve polarization• control spin orientation• function at different beam energies• handle multiple bunches and nominal intensity• …
Frank Zimmermann, CLIC BDS Day, 22.11.2005
schematic view of beam delivery system
Frank Zimmermann, CLIC BDS Day, 22.11.2005
modular layout
energy collimationbetatron collimation
compact final focus
interactionregion exit line
IP switch?
dump
Frank Zimmermann, CLIC BDS Day, 22.11.2005
Raimondi FF ~0.5 kmCCS length ~2.0 km
nonzero D’at IP
only 1 stagemomentumcoll.
betatron coll.with low x,y
final focus.
optics
F.Z., CLIC-NOTE-551
Frank Zimmermann, CLIC BDS Day, 22.11.2005
c.o.m. energy 3 TeV
final-focus length 0.5 km
collimation length 2.0 km
hor.,vert. emittance x,y 0.68, 0.01 m
hor.,vert. beta function x,y* 7, 0.09 mm
core spot sizes x,y* 60, 0.7 nm
linear spot sizes 37, 0.5 nm
bunch length z 30.8 m
crossing angle c 20 mrad
bunch population Nb 2.56x109
# bunches / train nb 220
luminosity w/o pinch L0 3.6x1034 cm-2s-1
ideal luminosity w/o pinch L00 9.3x1034 cm-2s-1
beam delivery system & beam parameters
61%luminosityloss
Frank Zimmermann, CLIC BDS Day, 22.11.2005
horizontalphase-spacedistributionat the IPcalculatedwithMerlinfor a nominalbunch
particles arefound evenat amplitudes>1 m, while the beam sizeis about 40 nm
S. Redaelli et al, CLIC Note 577 (Nanobeam’02)
Merlin, x>3x: 6.7%, x>6x: 2.3%, y>3 y: 15.2%, y>6y: 7.7%, large tail population
IP distribution
→ for recent studies see talks by T. Asaka & J. Resta Lopez
Frank Zimmermann, CLIC BDS Day, 22.11.2005
x rms Gaussian fit
MAD 96.3+/-0.7 nm 55.39+/-0.07 nm
DIMAD 99.0+/-1.4 nm 54.59+/-0.17 nm
Merlin 129.7+/-1.5 nm 57.49+/0.13 nm
PLACET 99.3 +/1.3 nm 54.12+/0.17 nm
y rms Gaussian fit
MAD 3.05+/-0.04 nm 0.680+/-0.001 nm
DIMAD 3.35+/-0.06 nm 0.800+/-0.002 nm
Merlin 4.04+/-0.03 nm 0.688+/-0.002 nm
PLACET 3.42+/-0.03 nm 0.775+/-0.002 nm
what is x,y? S. Redaelli et al, CLIC Note 577 (Nanobeam’02)
linear ideal beam sizes:x=37.3 nm, y=0.49 nm Gaussian fit ‘loses’ particles
Frank Zimmermann, CLIC BDS Day, 22.11.2005
CLIC BDS “footprints” at 3 TeV and 500 GeV
F.Z., CLIC-NOTE-551
Frank Zimmermann, CLIC BDS Day, 22.11.2005
compact FF à la Raimondi & Seryi
advantages:larger free length l* from last quad to IP,wider momentum bandwidth,reduced beam tails
drawbacks:tighter collimation in x,sextupoles near final doublet (tuning knobs)
Frank Zimmermann, CLIC BDS Day, 22.11.2005
simulated luminosity w/o pinch & w/o hourglass as a function of full-widthenergy spread with & w/o synchrotron radiation for two different values ofx,y* and assuming y=10 nm; L0=4.6x1034 cm-2 s-1
luminosity losses:
SR in bends→L~-50%
momentum spread→L~-30%
SR in finalquad’s→L~-10%
luminosity performance
F.Z., CLIC-NOTE-551
Frank Zimmermann, CLIC BDS Day, 22.11.2005
system Length [m] Luminosity w/o pinch [1034 cm-2 s-1]
total BDS 2557 3.56
original long BDS 6186 3.92
final focus only 548 4.85
geometric luminosity without hourglass and without pinch (input distribution from PLACET for old linac pararameters, and taking x=6 mm, y=70 mm)
numbers refer to new beam parameters: 2.56e9, 150 Hz, 22 bunches/ train
28% luminosityloss fromcollimation system
CLIC-NOTE-551
Frank Zimmermann, CLIC BDS Day, 22.11.2005
O. NapolyCLIC Note 414, 1999
y~1 nm limitfor y~20 nm
dependence on as y~5/7
x ~30 nm limit
spot-size limit from SR in final quadrupoles (Oide effect)
Frank Zimmermann, CLIC BDS Day, 22.11.2005
top view of
CLIC IR
R. Assmann
crab cavity
crab cavity
CLIC-NOTE-551
Frank Zimmermann, CLIC BDS Day, 22.11.2005
final quadrupole study by M. Aleksa & S. Russenschuckindicated preference for permanent magnet
CLIC-NOTE-506
stability of magnetic center? asymmetric T=1 K (9 kJ/m)→ y=286 nm
Frank Zimmermann, CLIC BDS Day, 22.11.2005
or should we reconsider s.c.quadrupole?
Frank Zimmermann, CLIC BDS Day, 22.11.2005
synchrotron radiation in solenoid (fringe) field together with vertical dispersion due to crossing angle & solenoid causes vertical beam blow → crossing angle limited to 20 mrad
D. Schulte, F. Zimmermann, CLIC-NOTE-484
Frank Zimmermann, CLIC BDS Day, 22.11.2005
spent beam & exit line
at 3 TeV wide energy spread
conceptuallayout of quadrupole-lessexit line
F.Z., CLIC-NOTE-551
D. Schulte,CLIC-NOTE-391
water dump at 4oCB. Jeanneret & E. Wildner, CLIC-NOTE-421
Frank Zimmermann, CLIC BDS Day, 22.11.2005
polarizationspin rotation angle a~ 3404 times bend angle
polarizationvectormust bematched into theBDSto ensurelongitudinalpolarizationat the IP
R. Assmann, F. Zimmermann,CLIC-NOTE-501
Frank Zimmermann, CLIC BDS Day, 22.11.2005
collimation requirements:
• remove beam halo to suppress detector background arising from synchrotron radiation and beam loss
• provide minimum distance from collimators to collision point for muon suppression
• ensure collimator survival and machine protection against errand beam pulses
• not be excessively long
• not amplify incoming trajectory fluctuations via collimator wake fields
Frank Zimmermann, CLIC BDS Day, 22.11.2005
SR fans with beam envelopes at 14 x & 83y
O. Napoly
CLIC-NOTE-446
Frank Zimmermann, CLIC BDS Day, 22.11.2005
collimator survival? surface of 20-m gold-plated Ti-alloycollimator at the endof SLC linac after damage; CLIC beam is ~104 times more intense!
Frank Zimmermann, CLIC BDS Day, 22.11.2005
LC collimation concept: thin spoilers followedby thick absorbers [H. DeStaebler & D. Walz];spoiler increases angular divergence, reducesrisk of fracture and/or melting
Frank Zimmermann, CLIC BDS Day, 22.11.2005
nominal beam sizes at CLICspoilerssuperposedon ‘FJP’ damagethresholddiagram
‘FJP’ = S. Fartoukh, B. Jeanneret & J. Pancin CLIC-NOTE-477
Frank Zimmermann, CLIC BDS Day, 22.11.2005
CLIC failure modes & machine protection
• large betatron oscillations are not easily generatedfrom pulse to pulse; and in the linac they rapidly filament& emittance increases by ~2 orders of magnitude
• energy errors will occur much more frequently, e.g., due to missing or mis-phased drive beams, injection phase errors, or charge fluctuation
CLIC philosophy: demand passive survival for momentum errors; but allow sacrificial betatron collimators
failure mode study by Daniel Schulte & F.Z. at PAC2001
(shorter length)
Frank Zimmermann, CLIC BDS Day, 22.11.2005
simulated effective beam size r=(x y)1/2 at 1st spoiler; error bar indicates minimum and maximum over 10 random seeds
CLIC-NOTE-492
various failure modes
Frank Zimmermann, CLIC BDS Day, 22.11.2005
simulated centroidbetatron oscillationamplitudes at the first spoiler, norma-lized to unperturbedrms beam sizes; error bars showmin. and max. over10 random seeds
these pulses would destroythe betatron collimatorsthese pulses might destroy
the betatron collimators
tighten momentum collimation depth to intercept all dangerous pulses by the momentum spoiler!
various failure modes
CLIC-NOTE-492
Frank Zimmermann, CLIC BDS Day, 22.11.2005
momentum collimation depth: failure modes & machine protection from linac failure modes: about +/- 1.5%
transverse collimation depth: from synchrotron radiation & beam loss in final quadrupoles on incoming side onlyx from SR fan in final doublet: about +/- 10 x
y from SR fan in final doublet: about +/- 80 y
Frank Zimmermann, CLIC BDS Day, 22.11.2005
cm energy 3 TeV 500 GeV
spoiler gap +/- 4 mm (1.5%) +/- 4.8 mm (1.5%)
x spoiler gap +/- 80 m (10 x) +/- 300 m (9 x)
y spoiler gap +/- 104 m (80 y) +/- 215 m (69 y)
spoiler material Be Be
spoiler length 177 mm (0.5 r.l.) 177 mm (0.5 r.l.)
absorber material
Ti (Cu coated) Ti (Cu coated)
absorber length 712 mm (20 r.l.) 712 mm (20 r.l.)
no. of spoilers 1 1
no.x,y spoilers 4, 4 4, 4
collimator parameters
scattered beam size on -absorber: r ~1.1 mm!?should r>r.l.?
Frank Zimmermann, CLIC BDS Day, 22.11.2005
unmagnetized cyl.radius 20 cmunmagnetized cyl.& only 1st photon
magnetized cyl.
unmagnetized cyl.radius 50 cm
Geant-4simulationfor 10000 e- lost on first spoiler(H. Burkhardt)
size of magnetsmatters!
(H. Burkhardt, Nanobeam 2002)
muon background
Frank Zimmermann, CLIC BDS Day, 22.11.2005nominal
max. jitter enhancement from collimator wake
carbon spoilerseems not acceptable;Be spoilerpossible;absorbers fromCu-coatedTi & pureCu both ok
4 spoilers & 4 absorbers(Redaelli)CLIC-NOTE-579
Frank Zimmermann, CLIC BDS Day, 22.11.2005
alternative nonlinear collimation system
basic scheme
→ talks by A. Faus-Golfe & J. Resta Lopez
better optical performancereduced wake fieldsshorter?
Frank Zimmermann, CLIC BDS Day, 22.11.2005
energy distribution alongold CLIC BDS from 1000laser-wire Compton scatters
total energy loss per bunchtrain along the CLIC BDSdue to 0.1% flat halo
backgrounds completely swamp laser-wire signal!G.A. Blair, BDSIM simulation, Nanobeam2002
laser wire as beam-size monitor?
Frank Zimmermann, CLIC BDS Day, 22.11.2005
margins & overheads?
S. Redaelli’s simulations indicate 25-30% luminosity loss due to fast ground motion
1996 NLC ZDR estimated 20% luminosity loss due to limited beam-based tuning precision for 16 important IP aberrations (Irwin et al)
we could expect a total luminosity loss >50% due to these effects
Frank Zimmermann, CLIC BDS Day, 22.11.2005
Frank Zimmermann, CLIC BDS Day, 22.11.2005
simulate luminosity performance with errors, ground motion, component jitter, feedback, and realistic tuning, and noisy diagnostics integrated simulation, including realistic beam distribution from linac with its own errors and tails improve performance of present system, especially collimation (→shorter, wider bandwidth, higher luminosity), characterize collimation efficiency fully master design of compact final focus Be spoilers acceptable? beam size at absorber? wake field effects, electron cloud, etc.
open questions & outstanding tasks
Frank Zimmermann, CLIC BDS Day, 22.11.2005
thank you for your attention!