Transcript Ring to Main Linac (RTML): Status and Plans ILC January Meeting (KEK) Peter Tenenbaum 19-Jan-2006

Ring to Main Linac (RTML):
Status and Plans
ILC January Meeting (KEK)
Peter Tenenbaum
19-Jan-2006
A Few Improvements
• The RTML is almost unchanged from the design
described in the BCD
• There are a few changes which are proposed
– Move boundary of Damping Ring section to include damping ring
extraction region (DRX)
• Proposed boundary is at zero-dispersion point at end of DRX
– Replace multi-wire emittance station in Emit1 with single wire or
other profile device
– Insert 610 m (approx) transfer line (DRStretch) to optimize DR
position within site boundary
– Remove skew correction section from Emit2
– Extend Linac Launch + diagnostic section (not quite long enough
in BCD)
– Remove first diagnostic section in main linac
• Redundant with last diagnostic station in RTML!
• This talk assumes that these changes will be accepted,
and describes the changed system
19-Jan-2006
Peter Tenenbaum
2
RTML Footprint
Anamorphic Diagram of RTML Footprint
60
Skew Correction
Collimation
DR Stretch
Turnaround
Spin Rotator
Emittance
BC1
BC2
Linac Launch
50
X Position [m]
40
30
20
10
0
-10
-1800
19-Jan-2006
-1600
-1400
-1200
-1000
-800
-600
Z position [m]
Peter Tenenbaum
-400
-200
0
200
3
Basis for Estimates of Lengths and
Components
• Bunch compressors: lattice files of 3rd
generation designs from 2005
• Other systems: scaling from TESLA or
NLC lattices based on changes in beam
parameters, if any
– These estimates are necessarily rougher than
the bunch compressors
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System Lengths
Region
Length
Skew Correction
35 m
Collimation
110 m
DR Stretch
610 m
Turnaround
170 m
Spin Rotator
80 m
Emittance
35 m
BC1
400 m
BC2
1000 m
Linac Launch
60 m
Total
2500 m
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Peter Tenenbaum
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Magnet Counts
Region
Bends
Quads
Sexts
Corrs
Fast
Solenoids
Kickers
Skew
0
17
0
34
0
0
Collimation
0
15
0
30
0
0
DR Stretch
0
24
0
48
0
0
Turnaround
100
100
10?
200
0
0
SpinRot
6
30
0
60
0
4
Emittance
0
13
0
26
4
0
BC1
100
30
0
60
20
0
BC2
100
55
0
110
0
0
LinacLaunch 2
16
0
32
20
0
Total
300
10?
600
44
4
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Peter Tenenbaum
6
Instrumentation
Region
BPMs
WIREs
PROFs
BLMs
Phase
Skew
17
0 or 1
1 or 0
0
1
Collimation
15
0
0
0
0
DR Stretch
24
0
0
0
0
Turnaround
100
0
0
0
0
Spin Rotator
30
0
0
0
0
Emittance
13
6
0
0
0
BC1
32
0
0
1
1
BC2
57
0
0
1
1
Linac Launch
16
4
0
0
0
Total
304
10 or 11
0 or 0
2
3
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BC RF Systems
• BC1 has 3 cryomodules, 1 klystron, plus one spare klystron with
waveguide switch
• BC2 has 57 cryomodules, 19 klystrons, of which 1 klystron + 3
cryomodules are spare
• Gradients modestly lower than 31.5 MV/m needed
• Stations operate far from RF crest
– Need to change klystron amplitude and phase during train to
compensate beam loading
– Larger average power goes to RF loads than in main linac stations
• Phase and amplitude tolerances are tight
– Phase jitter < 0.1°  2% loss of integrated luminosity from longitudinal
jitter of collision point
• Most promising bunch length monitor requires crab cavity
– Based on system prototyped at SPPS and TTF2
– Might need crab cavities for bunch length measurement, depending on
downselect of BLM technology
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Bunch Compressor Wiggler
• Each BC in baseline has 240 meters of bend
magnets arranged in chicanes to generate
compression
– Long!
• Considering two approaches to reducing length
– Enhancing R56 by forcing nonzero D’ at quads
– Replacing wiggler with 4-bend chicane with optimized
lattice functions for emittance preservation
• Issue here is control of vertical dispersion and emittance
growth from pitched cavities
– Studies ongoing at this time
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Beam Stops
• Current design has 3
– Low power (< 1 kW) insertable stopper
• Somewhere in skew correction or collimation section – need to find the best
spot for it
– Allows single-bunch tuneup of beams extracted from DR
– Full power (220 kW and 660 kW) pulsed dumps after BC1 and in Linac
Launch
• Allow bunch length tuneup without sending beam into next RF section
• Also may have machine protection role
• 3 possible modes of operation
– Train-by-train, using pulsed bends
– Intra train, with fast (100 nsec risetime) kickers
– Bunch stealing – take 1 bunch out of train for diagnostic purposes (open to
debate)
• Are these enough?
• Or possibly too much?
• Can we save money in pulsed systems by limiting their average
power but allowing a large peak power?
– Can take a full train for MPS occasionally, or a fraction of a train forever
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Spin Dynamics
• Each side has 1 complete spin rotator
• Implications:
– Can’t simultaneously run to 2 IRs with spin
optimized in both
• Need 2 spin rotators per side
– Can’t to train-to-train spin-flipping of positrons
• Would need either 2 or 4 spin rotators on positron
side
• How important is this?
• Can we do it upstream of the DR? At 250 MeV?
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Tunnels etc.
• Current assumption: RTML is laserstraight
– Main linac is curved
– Somewhere there must be dispersion
matching between RTML and ML
• Two parts of RTML beamline (upstream of
turnaround and downstream) share tunnel
– Is that OK? Is it cost-optimal?
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Collimation
• Assuming 2 phases x 2 planes x 1 iteration of
collimation
• Spoiler survival probably not a problem
– Large geometric emittances
– Close to DR – can halt extraction quickly
• Collimated halo points at BC2 and BC1 RF
stations
– Is that OK?
• Assuming energy collimation in turnaround or
bunch compressor wigglers
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Progress since Frascati
• Work started on shorter BC wigglers and
turnaround optics
• Leaders of all Technical and Global
systems contacted
– Notified about potentially interesting issues in
the RTML
– Dialogue begun – “What do you need from us,
when do you need it, and with whom should
we be corresponding?”
– Most TS and GS have replied already!
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Upcoming Milestones (Tentative
Map)
• 20 Jan
– Finalize boundaries and other changes described on
Slide 2
• 29 Jan
– Site layout, RF unit, PPS / MPS issues finalized
• Impact DR Stretch and other areas
• 12 Feb
– Complete optics for turnaround
– Complete optics for collimation system
– Complete optics for BC wigglers
• 26 Feb:
– Complete optics for pulsed dumplines
– Select BLM technology (or technologies)
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Milestones (2)
• 12 Mar:
– Complete all optics
– Select size monitor technology for Skew section
• 22 Mar:
– Attend Sisters of Mercy concert @ Warfield in San
Francisco
• 27 Mar:
– Complete system integration of lattices (“Woodleyfication”)
• April:
– Review RTML design and place lattices and
documentation under change control
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