Beam Delivery System and Interaction Region of
a Linear Collider
Beam Delivery System and Interaction Region of
a Linear ColliderNikolai Mokhov, Mauro Pivi, Andrei SeryiNikolai Mokhov, Mauro Pivi, Andrei Seryi
The US Particle Accelerator SchoolJanuary 15-26, 2007 in Houston, Texas
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LectureRECENT DESIGN
DEVELOPMENTS
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Evolution of ILC BDS design in 2006
20mr IR
2mr IR
FF
E-collim.-collim.
DiagnosticsBSYtune-up dump
Two collider halls separated longitudinally by 138m
14mr IR
14mr IR
One collider hall
Vancouver baseline
Valencia baseline
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14(20)mrad IR
BNL, B.Parker, et al
5BNL, B.Parker, et al
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FD14 design
Sizes optimized for detector opening
Feedback kicker area
Interface region being optimized with forward detector region
BNL
Focus on 14mr design to push technology
Size and interface of shared cryostat being optimized with detector
Feedback area being designed
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QD0SD0 QF1
SF1 Q,S,QEXF1
Disrupted beam & Sync radiations
BeamstrahlungIncoming beam
60 m
Shared Large Aperture Magnets
Rutherford cable SC quad and sextupole
pocket coil quad
2mrad IR
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100W/m hands-on limit
Losses are mostly due to SR. Beam loss is very small
100W/m
Losses are due to SR and beam lossJ. Carter, I. Agapov, G.A. Blair, L. Deacon (JAI/RHUL), A.I. Drozhdin, N.V. Mokhov (Fermilab), Y.M. Nosochkov, A.A. Seryi (SLAC)
20mrad
2mrad
Losses in extraction
line20mr: losses < 100W/m at 500GeV CM and 1TeV CM
2mr: losses are at 100W/m level for 500GeV CM and exceed this level at 1TeV
Radiation conditions and shielding to be studied
250GeV Nominal, 0nm offset
45.8kW integr. loss
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Physics Benchmarks for the ILC Detectors, hep-ex/0603010, M. Battaglia, T. Barklow, M. E. Peskin, Y. Okada, S. Yamashita, P. Zerwas
Benchmarks for evaluation of ILC detectors
Reaction which cares most about crossing angle is
Detection is challenged by copious
which require low angle tagging.
Tagging is challenged by background from pairs and presence of exit hole
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Study of SUSY reach
• SUSY reach is challenged for the large crossing angle when m (slepton-neutralino) is small
• Studies presented at Bangalore (V.Drugakov) show that for 20mrad+DID (effectively ~40mrad for outgoing pairs), due to larger pairs background, one cannot detect SUSY dark matter if m=5GeV
• The cases of 20 or 14mrad with anti-DID have same pairs background as 2mrad. Presence of exit hole affects detection efficiency slightly. The SUSY discovery reach may be very similar in these configurations
• Several groups are studying the SUSY reach, results may be available after Vancouver
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Backscattering of SR
FD produce SR and part will hit BYCHICMB surfaceTotal Power = 2.5 kW<E>=11MeV (for 250GeV/beam)
Takashi MaruyamaFrom BYCHICB
Rate #s at IP/BX
#s in SiTracker from pairs
250 GeV 1.1x10-8 2200 700
500 GeV 2.9x10-8 11700 1900
Photon flux within 2 cm BeamCal aperture:
SR from 250 GeV disrupted beam,
GEANT
Flux is 3-6 times larger than from pairs. More studies & optimization needed
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Ken Moffeit, Takashi Maruyama, Yuri Nosochkov, Andrei Seryi, Mike Woods (SLAC), William P. Oliver (Tufts University), Eric Torrence (Univ. of Oregon)
GEANT tracking in extraction lines
Study achievable precision of polarization and energy measurements, background & signal/noise, requirements for laser, etc.
Compton Detector Plane20mrad 2mrad
Downstream diagnostics evaluation (1)
Compton IP
(cm)
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Downstream diagnostics evaluation (2)
Comparisons for 250GeV/beam 20mr 2mr
Beam overlap with 100mm laser spot at Compton IP
48% 15%
Polarization projection at Compton IP 99.85% 99.85%
Beam loss form IP to Compton IP <1E-7 >2.6E-4
Beam SR energy loss from IP to middle of energy chicane
119MeV 854MeV
Variation of SR energy loss due to 200nm X offset at IP
< 5MeV( < 20 ppm)
25.7MeV(~100 ppm)
The need for SR collimator at the Cherenkov detector
yes No
comparable with the goal for E precision measurements
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Brainstorm to design magnets in 2mrad extraction
Some magnet sizes on this drawing are tentative
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Recent suggestions
Brainstorm for 2mrad magnets
B1
beamstrahlung
> 2
m
Vladimir Kashikhin , Brett Parker, John Tompkins, Cherrill Spencer, Masayuki Kumada, Koji Takano, Yoshihisa Iwashita, Eduard Bondarchuk, Ryuhei Sugahara
BHEX1
Power @ 1TeV CM is 635-952 KW/magnet. Pulsed may be feasible?
Power @ 1TeV CM is 1MW/magnet. Temperature rise is very high. Use of HTS? Pulsed? Further feasibility study and design optimization are needed
QEX3
QEX5
should have 6-60GS field!
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Magnets
• Things to care: – needed aperture, L– strength, field quality,
stability– losses of beam or SR in the area
• E.g., extraction line => need aperture r~0.2m and have beam losses => need warm magnets which may consume many MW => may cause to look to new hybrid solutions, such as high T SC magnets
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Magnet current (Amp*turn) per coil
and total powerI(A)=B(Gs)*h(cm)*10/(4) P(W)=2*I(A)*j(A/m2)*(*m)*l(m)
I(A)=1/2*B(Gs)*h(cm)*10/(4)
P(W)=4*I(A)*j(A/m2)*(*m)*l(m)
I(A)=1/3*B(Gs)*h(cm)*10/(4)
P(W)=6*I(A)*j(A/m2)*(*m)*l(m)
For dipole h is half gap. For quad and sextupole h is aperture radius, and B is pole tip field. Typical bends may have B up to 18kGs, quads up to 10kGs. Length of turn l is approximately twice the magnet length. For copper ~2*10-8 *m.For water cooled magnets the conductor area chosen so that current density j is in the range 4 to 10 A/mm2
Bend
Quad
Sextupole
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Drivers of the cost and cost
• Cost drivers– CF&S– Magnet system– Vacuum system– Installation– Dumps & Colls.
• Drivers of splits between 20/2:– CF&S– Magnet system– Vacuum system– Dumps &
collimators– Installation; Controls
Total Cost
Additional costs for IR20 and IR2
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from MDI panel statement
• The physics mode most affected by crossing angle is the slepton pair production where the slepton-LSP m is small. The main background is 2- processes and an efficient low-angle electron tag by BEAMCAL is needed to veto them.
• Difference in expected background (is due to) different levels of veto efficiency. Signal to noise will be ~4 to 1 with 2mrad crossing angle.
• For a large crossing angle (14 or 20mrad), anti-DID is needed to collimate the pair background along the outgoing beam. For 14mrad crossing with anti-DID, the … background is expected to be comparable to the 2mrad case while the signal efficiency reduces by about 30% to 40%. This is mainly due to the 2nd hole of BEAMCAL that is needed for the large crossing angle which will force additional cuts to remove the 2-photon and other backgrounds.
• for 20mrad crossing with anti-DID was found to be essentially the same as the 2mrad case.
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Valencia 14/14 baseline. Conceptual CFS layout
IP2
IP1
10m
1km
beam dump service hallalcoves
9m shaft for BDS access
polarimeter laser borehole
muon wall tunnel widening
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CFS designs for two IRs
Valencia
Vancouver
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beam dump service hall
alcoves
9m shaft for BDS access & service hall
beam dump and its shield
muon wall tunnel widening
Beam Delivery System tunnels
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CMS assembly approach• Assembled on the surface in parallel with underground work• Allows pre-commissioning before lowering• Lowering using dedicated heavy lifting equipment• Potential for big time saving• Reduces size of required underground hall
On-surface assembly : CMS approach
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BDS with single IR
14mr IR
FF
E-collimator
-collim.
Diagnostics
Tune-up dump
BSY
Sacrificial collimators
Extraction
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polarimeterskew correction /emittance diagnostic
MPScoll
betatroncollimation
fastsweepers
tuneupdump
septa
fastkickers
energycollimation
betamatch
energyspectrometer
finaltransformer
finaldoublet
IP
energyspectrometer
polarimeter
fastsweepers
primarydump
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QFSM1moves~0.5 m
polarimeterchicane
septafastkickers
“Type B” (×4)
500GeV => 1TeV CM upgrade in BSY of 2006e
M. Woodley et al
Magnets and kickers are added in energy upgrade
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Single IR BDS optics (2006e)
FF
E-c
ollim
ator
-collim.Diagnostics
BSY
Pol
arim
eter
E-s
pect
rom
eter
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warm
Detector
IP
common stationary cryostat
QD0QF1
vacuum connection & feedback kicker
Concept of single IR Final Doublet
Redesigned FDOriginal FD and redesigned for push-pull (BNL)
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cancellation of the external field with a shield coil has been successfully demonstrated at BNL
BNL prototype of self shielded quad
IR magnets
BNL prototype of sextupole-octupole magnet
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• Rearranged extraction quads are shown. Optics performance is very similar.
• Both the incoming FD and extraction quads are optimized for 500GeV CM.
• In 1TeV upgrade would replace (as was always planned) the entire FD with in- and outgoing magnets. In this upgrade, the location of break-point may slightly move out. (The considered hall width is sufficient to accommodate this).
http://ilcagenda.cern.ch/conferenceDisplay.py?confId=1187
Nominal scheme
Push-pull scheme
New optics for extraction FD : push pull compatible
B.Parker, Y.Nosochkov et al.
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Extraction Lines : shortened by 100m
high L parameters(500 GeV CM)
For undisrupted beam reliance on beam sweeping on beam dump window using kickers.
Total loss before and at collimators for High L parameters is within acceptable levels. Losses for the nominal case are negligible.
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detectorB
may be accessible during run
accessible during run Platform for electronic and
services (~10*8*8m). Shielded (~0.5m of concrete) from five sides. Moves with detector. Also provide vibration isolation.
Concept of single IR with two detectors
The concept is evolving and details being worked out
detectorA
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Detector systems connections
fixed connections
long flexible connections
detectordetector service platform or mounted on detector
high V AC
high P room T Hesupply & return
chilled water for electronics
low V DC forelectronics
4K LHe for solenoids
2K LHe for FD
high I DC forsolenoids
high I DC for FD
gas for TPCfiber data I/O
electronics I/O
low V PShigh I PSelectronic racks4K cryo-system2K cryo-systemgas system
sub-detectorssolenoidantisolenoidFD
move together
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QD0 part QF1 part
doorcentral part
Optimized for fast switch of detectors in push-pull and fast opening on beamline
This scheme require lengthening L* to 4.5m and increase of the inner FD drift
Opening of detectors on the beamline (for quick fixes) may need to be limited to a smaller opening than what could be done in off-beamline position
Push-pull cryo configuration
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IR & rad. safety
• For 36MW MCI, the concrete wall at 10m from beamline should be ~3.1m
18MW loss on Cu target 9r.l \at s=-8m. No Pacman, no detector. Concrete wall at 10m.Dose rate in mrem/hr.
Wall
25 rem/hr10m
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Self-shielding detector
18MW on Cu target 9r.l at s=-8mPacman 1.2m iron and 2.5m concrete
dose at pacman external wall dose at r=7m 0.65rem/hr (r=4.7m) 0.23rem/hr
Detector itself is well shielded except for incoming beamlines
A proper “pacman” can shield the incoming beamlines and remove the need for shielding wall
18MW lost at s=-8m. Packman has Fe: 1.2m, Concrete: 2.5m
38250mSv/h
Shielding the IR hall
Self-shielding of GLD Shielding the “4th“ with walls
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Working progress on IR design…
John Amann
3m Thickness
9m Base25m Height
Structural Rib
Overlapping Rib
Illustration of ongoing work… Designs are tentative & evolving
Mobile Shield Wall
Mobile Platform20m x 30m
Electronics/Cryo Shack1m Shielded
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Working progress on IR design…
Illustration of ongoing work… Designs are tentative & evolving
John Amann
Recessed Niche
Pac Man Open
Pac Man Closed
Beam Line Support Here
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Working progress on IR design…
Looking into experience of existing machines…
CMS shield opened
pacman closed
pacman openSLD pacman closed door tunnel pacman opened
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UA2, CERN
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Air-pads at CMS
Photo from the talk by Y.Sugimoto, http://ilcphys.kek.jp/meeting/lcdds/archives/2006-10-03/
Single air-pad capacity ~385tons (for the first end-cap disk which weighs 1400 tons). Each of air-pads equipped with hydraulic jack for fine adjustment in height, also allowing exchange of air pad if needed. Lift is ~8mm for 385t units. Cracks in the floor should be avoided, to prevent damage of the floor by compressed air (up to 50bars) – use steel plates (4cm thick). Inclination of ~1% of LHC hall floor is not a problem. Last 10cm of motion in CMS is performed on grease pads to avoid any vertical movements. [Alain Herve, et al.]
14kton ILC detector would require ~36 such air-pads
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Displacement, modeling
Starting from idealized case: -- elastic half-space (Matlab model) -- simplified ANSYS model (size of modeled slab limited by memory)
Short range deformation (~0.1mm) is very similar in both models. Long range (1/r) deformation (~0.3mm) is not seen in ANSYS because too thin slab in the model
More details (3d shape of the hall, steel plates on the floor, etc.) to be included.
Long term settlement, inelastic motion, etc., are to be considered. Parameters: M=14000 ton; R=0.75m (radius of air-pad); E=3e9 kg/m^2, n=0.15 (as for concrete); Number of air-pads=36
J.Amann, http://ilcagenda.cern.ch/conferenceDisplay.py?confId=1225
Matlab model, half-space
ANSYS model
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Schedule for the design goal time (a.u.)
• The hardware can be designed to be compatible with a ~one day move, and this can be a design goal– Need to study cost and reliability versus the move duration – Need to study regulations in each regions
• Recalibration (at Z) may or may not be needed, and may be independent on push-pull – to be studied
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CFS layout for single IR & central DR
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CFS layout for single IR
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x
x
RF kick
Crab crossing
2 2 2,
20mr 100μm 2μm
x projected x c z
c z
factor 10 reduction in L!
use transverse (crab) RF cavity to ‘tilt’ the bunch at IP
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Crab cavity requirements
IP
~0.12m/cell ~15m
Crab Cavity
Slide from G. Burt & P. Goudket
Use a particular horizontal dipole mode which gives a phase-dependant transverse momentum kick to the beam
Actually, need one or two multi-cell cavity
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TM110 Dipole mode cavity
View from top
Beam
Magnetic fieldin green
Electric Fieldin red
For a crab cavity the bunch centre is at the cell centre when E is maximum and B is zero
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Crab cavities
• Top: earlier prototype of 3.9GHz deflecting (crab) cavity designed and build by Fermilab. This cavity did not have all the needed high and low order mode couplers. • Bottom: Cavity modeled in Omega3P, to optimize design of the LOM, HOM and input couplers.FNAL T. Khabibouline et al., SLAC K.Ko et al.Design is being continued by UK-US team
3.9GHz cavity achieved 7.5 MV/m
• BDS has two SC 9-cell cavities located ~13 m upstream of the IP operated at 5MV/m peak deflection. • Based on a Fermilab design for a 3.9GHz TM110 mode 13-cell cavity. • The uncorrelated phase jitter between the positron and electron crab cavities must be controlled to 61 fsec to maintain optimized collisions. • A proof-of-principle test of a 7 cell 1.5GHz cavity at the JLab ERL facility has achieved a 37 fsec level of control. • Other key issues to be addressed are LLRF control and higher-order mode damping.
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Beam dump for 18MW beam
• Water vortex• Window, 1mm thin, ~30cm
diameter hemisphere• Raster beam with dipole
coils to avoid water boiling• Deal with H, O, catalytic
recombination• etc.
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IR coupling compensation
When detector solenoid overlaps QD0, coupling between y & x’ and y & E causes large (30 – 190 times) increase of IP size (green=detector solenoid OFF, red=ON)
Even though traditional use of skew quads could reduce the effect, the local compensation of the fringe field (with a little skew tuning) is the most efficient way to ensure correction over wide range of beam energies
without compensation y/ y(0)=32
with compensation by antisolenoid
y/ y(0)<1.01
QD0
antisolenoid
SD0
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Antisolenoids
Antisolenoids (needed for both IRs to compensate solenoid coupling locally) with High Temperature Superconductor coils
BNL, P.Parker et al.
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Preliminary Design of Anti-solenoid for SiD
456mm
316mm
70mm cryostat
1.7m long
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0 2 4 6 8 10
15T Force
Four 24cm individual powered 6mm coils, 1.22m total length, rmin=19cm
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Detector Integrated Dipole
• With a crossing angle, when beams cross solenoid field, vertical orbit arise
• For e+e- the orbit is anti-symmetrical and beams still collide head-on
• If the vertical angle is undesirable (to preserve spin orientation or the e-e- luminosity), it can be compensated locally with DID
• Alternatively, negative polarity of DID may be useful to reduce angular spread of beam-beam pairs (anti-DID)
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Use of DID or
anti-DID
Orbit in 5T SiD
SiD IP angle zeroed w.DID
DID field shape and scheme DID case
anti-DID case
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ATF and ATF2
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ATF2 goals(A) Small beam size
Obtain y ~ 35nmMaintain for long time
(B) Stabilization of beam center Down to < 2nm by nano-BPM Bunch-to-bunch feedback of ILC-like
train
ATF2
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ATF2 optics
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Advanced beam instrumentation at ATF2
• BSM to confirm 35nm beam size• nano-BPM at IP to see the nm stability• Laser-wire to tune the beam• Cavity BPMs to measure the orbit• Movers, active stabilization, alignment system• Intratrain feedback, Kickers to produce ILC-like
train
IP Beam-size monitor (BSM)(Tokyo U./KEK, SLAC, UK)
Laser-wire beam-size Monitor (UK group)
Cavity BPMs, for use with Q magnets with 100nm resolution (PAL, SLAC, KEK)
Cavity BPMs with 2nm resolution, for use at the IP (KEK)
Laser wire at ATF
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ATF2 schedule
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ATF ring
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ATF hall