Beam Delivery System and
Interaction Region of a Linear
Collider
Nikolai Mokhov, Mauro Pivi, Andrei Seryi
The US Particle Accelerator School
January 15-26, 2007 in Houston, Texas
Lecture
RECENT DESIGN
DEVELOPMENTS
2
Evolution of ILC BDS design in 2006
Vancouver baseline
Diagnostics
BSY
b-collim.
tune-up dump
E-collim.
2mr IR
FF
20mr IR
Two collider halls separated
longitudinally by 138m
Valencia baseline
14mr IR
14mr IR
One collider hall
3
14(20)mrad IR
4
BNL, B.Parker, et al
5
BNL, B.Parker, et al
FD14 design
Interface region being optimized
with forward detector region
Sizes optimized for detector opening
BNL
Feedback kicker area
Focus on 14mr design to push technology
Size and interface of shared cryostat being
optimized with detector
Feedback area being designed
6
2mrad IR
Shared Large Aperture
Magnets
SF1
QD0
SD0
Disrupted beam & Sync radiations
Q,S,QEXF1
QF1
Beamstrahlung
Incoming beam
pocket coil quad
Rutherford cable SC
quad and sextupole
7
60 m
100W/m hands-on limit
Losses in
extraction line
20mr: 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
20mrad
Losses are mostly due to SR. Beam loss
is very small
2mrad
250GeV Nominal, 0nm offset
Radiation conditions and
shielding to be studied
100W/m
45.8kW integr. loss
J. Carter, I. Agapov, G.A. Blair, L. Deacon
(JAI/RHUL), A.I. Drozhdin, N.V. Mokhov
(Fermilab), Y.M. Nosochkov, A.A. Seryi (SLAC)
8
Losses are due to SR and beam loss
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
Physics Benchmarks for the ILC Detectors, hep-ex/0603010,
M. Battaglia, T. Barklow, M. E. Peskin, Y. Okada, S. Yamashita, P. Zerwas
9
Study of SUSY reach
• SUSY reach is challenged for the large crossing angle when Dm
(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 Dm=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
10
Backscattering of SR
Photon flux within 2 cm BeamCal aperture:
Rate
#gs at
IP/BX
250 GeV
1.1x10-8
500 GeV
2.9x10-8
2200
11700
#gs in
SiTracker
from pairs
700
1900
Flux is 3-6 times larger than from pairs.
More studies & optimization needed
SR from 250 GeV
disrupted beam, GEANT
FD produce SR and part will
hit BYCHICMB surface
Total Power = 2.5 kW
<Eg>=11MeV (for 250GeV/beam)
From BYCHICB
Takashi Maruyama
11
Downstream diagnostics evaluation (1)
Study achievable precision of polarization and
energy measurements, background & signal/noise,
requirements for laser, etc.
Compton IP
GEANT tracking
in extraction lines
(cm)
Ken Moffeit, Takashi Maruyama, Yuri Nosochkov,
Andrei Seryi, Mike Woods (SLAC), William P. Oliver
(Tufts University), Eric Torrence (Univ. of Oregon)
12
Compton Detector Plane
20mrad
2mrad
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
13
Brainstorm to design magnets in 2mrad
extraction
Some magnet sizes on this drawing are tentative
14
Brainstorm for
2mrad magnets
BHEX1
Recent suggestions
Power @ 1TeV CM is 1MW/magnet.
Temperature rise is very high. Use of HTS?
Pulsed? Further feasibility study and design
optimization are needed
> 2m
QEX5
B1
should have
6-60GS field!
Power @ 1TeV CM is 635-952
KW/magnet. Pulsed may be feasible?
beamstrahlung
Vladimir Kashikhin , Brett Parker, John Tompkins, Cherrill
Spencer, Masayuki Kumada, Koji Takano, Yoshihisa Iwashita,
Eduard Bondarchuk, Ryuhei Sugahara
15
QEX3
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
16
Magnet current (Amp*turn)
per coil and total power
Bend
I(A)=B(Gs)*h(cm)*10/(4p)
P(W)=2*I(A)*j(A/m2)*r(W*m)*l(m)
I(A)=1/2*B(Gs)*h(cm)*10/(4p)
Quad
P(W)=4*I(A)*j(A/m2)*r(W*m)*l(m)
I(A)=1/3*B(Gs)*h(cm)*10/(4p)
Sextupole
P(W)=6*I(A)*j(A/m2)*r(W*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 r~2*10-8 W*m.
For water cooled magnets the conductor area chosen so
that current density j is in the range 4 to 10 A/mm2
17
Drivers of the cost
and Dcost
Total 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
–
18
Installation; Controls
Additional costs for
IR20 and IR2
from MDI panel statement
• The physics mode most affected by crossing angle is the slepton pair
production where the slepton-LSP Dm is small. The main
background is 2-g 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.
19
Valencia 14/14 baseline.
Conceptual CFS layout
muon wall
tunnel widening
polarimeter
laser borehole
9m shaft for
BDS access
IP2
10m
alcoves
beam dump
service hall
1km
20
IP1
CFS designs for two IRs
Vancouver
Valencia
21
Beam Delivery System tunnels
9m shaft for
BDS access &
service hall
muon wall
tunnel widening
alcoves
beam dump
service hall
beam dump
and its shield
22
On-surface assembly : CMS approach
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
23
24
BDS with single IR
BSY
Sacrificial
collimators
b-collim.
E-collimator
Diagnostics
FF
14mr IR
Tune-up dump
Extraction
25
MPS
coll
skew correction /
emittance diagnostic
polarimeter
septa
betatron
collimation
fast
kickers
fast
sweepers
tuneup
dump
beta
match
final
transformer
energy
collimation
IP
energy
spectrometer
26
polarimeter
primary
dump
fast
sweepers
energy
final
spectrometer
doublet
500GeV => 1TeV CM upgrade in BSY of 2006e
“Type B” (×4)
polarimeter
chicane
fast
kickers
Magnets and kickers are
added in energy upgrade
septa
QFSM1
moves
~0.5 m
M. Woodley et al
27
Single IR BDS optics (2006e)
Diagnostics
28
b-collim.
E-spectrometer
E-collimator
Polarimeter
BSY
FF
Concept of single IR Final Doublet
vacuum
connection &
feedback kicker
Detector
QD0
common stationary
cryostat
QF1
warm
IP
Original FD and
redesigned for
push-pull (BNL)
29
Redesigned FD
IR magnets
BNL prototype of
sextupoleoctupole magnet
BNL prototype of self shielded quad
30
cancellation of the external field with a shield coil has been
successfully demonstrated at BNL
New optics for extraction FD : push pull compatible
• 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 inand outgoing magnets. In this upgrade,
the location of break-point may slightly
move out. (The considered hall width is
sufficient to accommodate this).
31
Nominal scheme
Push-pull scheme
B.Parker, Y.Nosochkov et al. http://ilcagenda.cern.ch/conferenceDisplay.py?confId=1187
Extraction Lines : shortened by 100m
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.
32
high L parameters
(500 GeV CM)
Concept of single IR with two detectors
The concept is evolving
and details being
worked out
may be
accessible
during run
detector
A
accessible
during run
detector
B
33
Platform for electronic and
services (~10*8*8m). Shielded
(~0.5m of concrete) from five
sides. Moves with detector. Also
provide vibration isolation.
Detector systems connections
detector service platform
or mounted on detector
detector
low V DC for
electronics
high V AC
4K LHe for solenoids
2K LHe for FD
sub-detectors
solenoid
antisolenoid
FD
high I DC for
solenoids
high I DC for FD
low V PS
high I PS
electronic racks
4K cryo-system
2K cryo-system
gas system
high P room T He
supply & return
chilled water
for electronics
gas for TPC
fiber data I/O
electronics I/O
fixed
connections
move together
34
long flexible
connections
Push-pull cryo configuration
Optimized for fast switch of
detectors in push-pull and fast
opening on beamline
QD0 part
QF1 part
This scheme require lengthening L* to
4.5m and increase of the inner FD drift
central part
35
door
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
IR & rad. safety
18MW loss on Cu target 9r.l \at s=-8m.
No Pacman, no detector. Concrete wall at 10m.
Dose rate in mrem/hr.
• For 36MW MCI, the concrete
wall at 10m from beamline
should be ~3.1m
Wall
25 rem/hr
10m
36
Self-shielding detector
Detector itself is well
shielded except for
incoming beamlines
A proper “pacman”
can shield the
incoming beamlines
and remove the
need for shielding
wall
37
18MW on Cu target 9r.l at s=-8m
Pacman 1.2m iron and 2.5m concrete
18MW lost at s=-8m.
Packman has Fe: 1.2m, Concrete: 2.5m
dose at pacman external wall
0.65rem/hr (r=4.7m)
dose at r=7m
0.23rem/hr
Shielding the IR hall
Self-shielding of GLD
250mSv/h
38
Shielding the “4th“
with walls
Working progress
on IR design…
Mobile Shield Wall
Illustration of ongoing work…
Designs are tentative & evolving
Structural Rib
3m Thickness
Overlapping
Rib
Mobile Platform Electronics/Cryo Shack
20m x 30m
1m Shielded
25m Height
John Amann
39
9m Base
Working progress
on IR design…
Pac Man Open
Illustration of ongoing work…
Designs are tentative & evolving
Recessed Niche
John Amann
40
Pac Man Closed
Beam Line Support Here
Working progress on
IR design…
CMS shield opened
Looking into experience
of existing machines…
SLD pacman closed
pacman open
pacman closed
41
door
tunnel
pacman opened
UA2, CERN
42
Air-pads
at CMS
Single air-pad capacity ~385tons
(for the first end-cap disk which
weighs 1400 tons). Each of airpads 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.]
43
Photo from the talk by Y.Sugimoto,
http://ilcphys.kek.jp/meeting/lcdds/archives/2006-10-03/
14kton ILC detector would require
~36 such air-pads
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
Matlab model, half-space
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
44
ANSYS model
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
45
CFS layout for single IR & central DR
46
CFS layout for single IR
47
Crab crossing
 x , projected   x2  c2 z2
x
 c z
 20mr 100μm  2μm
factor 10 reduction in L!
use transverse (crab) RF
cavity to ‘tilt’ the bunch at IP
x
RF kick
48
Crab cavity requirements
Crab Cavity
IP
~0.12m/cell
~15m
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
49 Slide from G. Burt & P. Goudket
TM110 Dipole mode cavity
View from top
Electric Field
in red
Beam
Magnetic field
in green
For a crab cavity the bunch centre is at the cell
centre when E is maximum and B is zero
50
Crab cavities
• 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 13cell 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.
51
• 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
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.
52
IR coupling compensation
without
compensation
y/ y(0)=32
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
antisolenoid
QD0
with compensation by
antisolenoid
y/ y(0)<1.01
53
SD0
Antisolenoids
Antisolenoids (needed for both IRs to compensate solenoid coupling locally) with High
Temperature Superconductor coils
54
BNL, P.Parker et al.
Preliminary Design of Anti-solenoid for SiD
70mm
cryostat
1.7m long
Four 24cm individual powered 6mm coils,
1.22m total length, rmin=19cm
0.3
15T Force
0.2
0.1
0
-0.1
-0.2
-0.3
0
316mm
456mm
55
2
4
6
8
10
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-eluminosity), 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)
56
Use of DID
or anti-DID
DID field shape and scheme
Orbit in 5T SiD
SiD IP angle
zeroed
w.DID
DID case
anti-DID case
57
ATF and
ATF2
58
ATF2
ATF2 goals
(A) Small beam size
Obtain y ~ 35nm
Maintain for long time
(B) Stabilization of beam center
Down to < 2nm by nano-BPM
Bunch-to-bunch feedback of ILC-like train
59
ATF2 optics
60
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)
Laser wire at ATF
61
Cavity BPMs with
2nm resolution,
for use at the IP
(KEK)
Cavity BPMs, for use with Q
magnets with 100nm
resolution (PAL, SLAC, KEK)
ATF2 schedule
62
ATF ring
63
ATF hall
64