Transcript . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . George Gollin University of Illinois at Urbana-Champaign and Fermi National Accelerator Laboratory . . . . ..

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George Gollin
University of Illinois at Urbana-Champaign
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Fermi National Accelerator Laboratory
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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Damping ring kickers
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• Current ideas
• Opinions from the speaker
• Illinois/Fermilab efforts
• ILC-America + ILC-global near term goals
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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• The specs
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•. The problem
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Outline
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Linac
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beam
(TESLA
TDR):
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. 340
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• .2820
bunches,
nsec
spacing
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• Cool an entire pulse in. the damping rings
before
linac
injection
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ILC damping ring beam:
• 2820 bunches, closely spaced
• Eject every nth bunch into linac (leave adjacent bunches undisturbed)
• Minimum damping ring circumference depends on minimum
realizable bunch spacing (kicker speed and instability issues)
Kicker:
• 20 ns kicker  17 km circumference (TESLA dog bone)
• 6 ns kicker  6 km circumference (Fermilab small ring)
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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The problem
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. in tackling
There’s
significant
global
interest
the
challenges
posed
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by the damping
ring and kicker.
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We have already started an informal, global “conversation”: see
Andy Wolski’s site at http://awolski.lbl.gov/ILCDR/. for a partial
list of who has made contact.
There are physicists from ANL, CERN, Cornell, Daresbury, DESY.
Fermilab, Frascati, Harvard, Illinois, KEK, LBNL, Minnesota,
SLAC, Tokyo so far.
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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What an.. interesting
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Extraction:
• damping is finished, bunches are small (a few microns in diameter) ;
• kicker must preserve beam emittance for still-orbiting bunches as well
as the kicked bunch.
Performance demands on kicker are different for injection/extraction.
Should we consider separate designs for injection and extraction?
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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Injection:
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• already-orbiting
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transverse
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• kicker must inject new
bunches into damping ring .acceptance
without
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losing already-orbiting bunches.
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What we have to work with
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Dog bone (TESLA TDR)
kicker specs:
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• impulse: 100 G-m (3 MeV/c) ± 0.07 G-m (2 keV/c)
• residual (off) impulse: 0 ± 0.07 G-m (2 keV/c)
• rise/fall time: < 20 ns
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Perhaps larger (but less precise) impulse at injection, smaller (but more
precise) impulse at extraction will be desirable.
Small ring kicker rise, fall times can be asymmetric:
• leading edge < 6 ns, trailing edge < 60 ns
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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. part,
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Kicker .specs
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an .unkicked
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The specs
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Fast
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strip
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Electromagnetic
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transverse
kick to. one bunch,
but .is .
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absorbed in .a load in each
strip line module before next
bunch arrives.
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• switch speed, on-resistance, and stability are concerns
• adequate precision of strip line termination is challenging
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• TESLA and SLAC are thinking about this
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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The ideas (1): strip line kicker. modules
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Demands
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it. only sees every 4. th bunch.
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multiple paths.
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Separate
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The system needs
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what happens
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when it is installed in a damping ring.
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Cornell, Frascati are thinking along these lines.
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George Gollin, Damping ring kickers, SLAC ILC-America, October 2004
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The ideas (2): longitudinal kick +. dispersion
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pulse. from a sum
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Most interesting (to me) .idea now: combine
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pulse
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compression system to. drive a small number of low-Q
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• what are stability requirements on RF components?
• how robust to bunch arrival time errors can the system be made?
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Illinois, Fermilab, Cornell are involved.
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kicking
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The ideas (3): Fourier engineering
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of a pulsed
kicker,
construct
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Fourier
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Damping ring architecture
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optics, etc.) is strongly tied to details of the kicker.
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A fast pulsed kicker might be simplest to operate BUT switch speed and
stability are challenging issues.
Significant proof of the feasibility of at least one design is needed
before a choice of damping ring design (big ring vs. small ring) will be
possible.
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. potential to be. a “show-stopper.”
The kicker
has the
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The speaker’s opinions .(1)
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Perhaps these features should be included in all damping ring designs?
There are three distinct stages in damping process:
• injection and assembly of bunch trains
• damping
• disassembly of bunch trains and extraction
Beam is very different in each of these stages. Should there be distinct
subsystems (including different kickers) for each of them?
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Fermilab
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ring studies
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. ~60
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• damping
ring. bunch trains
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ns inter-train gaps
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• long straight section to. allow installation
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incorporate:
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The speaker’s opinions .(2)
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Large
acceptance
injection
ring:
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• (340
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• assemble .a single bunch train by injecting
successive bunches. into .
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this ring at the tail of
the train already orbiting the. injection
ring
• transfer entire bunch train into the damping ring in one orbit
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Large acceptance damping ring (6 ns bunch spacing)
Small acceptance extraction ring:
• (340 + 6) = 346 ns circumference
• transfer one entire bunch train from the damping ring
• extract by kicking the last bunch in the train on successive orbits
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Separating
injection, damping, extraction
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Separating
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studies: use Fermilab A0 photoinjector
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1. build a fast, simple strip line kicker
2. use the kicker to study the timing/stability properties of the
A0 beam
3. build a single-module pulse compression kicker
4. study its behavior at A0
5. perform more detailed studies in a higher energy, low
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EOI submitted
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A0 photoinjector beam
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. are calculable
Start with. a. simple
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Most important: how. well can we measure a device’s
timing stability with the A0 beam?
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flanges
beam pipe
BPM
beam pipe
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stainless steel
pipe
BPM
conducting rods
Fermilab is currently designing this. Probably ready by January 2005.
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Simple kicker for initial tests
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UIUC HEP electronics design group’s chief is too.
So we’re starting to make progress.
Goals:
• install strip line kicker in A0 by January, 2005
• understand A0 by spring, 2005
• install small pulse compression kicker at A0 by summer, 2005
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Design, then
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• pre-KEK:. discuss tentative plans for kicker
R&D with our .
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colleagues in America, Asia, and Europe to have a sense
of who
would like to do what.
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• at KEK: rough-out an R&D plan aimed at choosing a kicker
technology in ~2 years
• at Snowmass (August, 2005): kicker workshop with international
participation to assess how well we’ve gotten started, and what we
have learned
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Possible
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timelines:
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ILC-America + ILC-global near-term
goals
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The. kicker
and damping ring
scare. .the daylights
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We must build one and
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More information:
• Studies Pertaining to a Small Damping Ring for the International
Linear Collider, FERMILAB-TM-2272-AD-TD
• ILC Damping Rings web site: http://awolski.lbl.gov/ILCDR/
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Physics
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End notes
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