Transcript The Wild, Wild West Confronts Big Science

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Fourier engineering: progress on
alternative TESLA kickers
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George Gollin
Department of Physics
University of Illinois at Urbana-Champaign
USA
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
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Damping ring beam (TESLA TDR):
•2820 bunches, ~20 nsec spacing (~ 17 kilometers)
•Eject every nth bunch into linac (leave adjacent bunches undisturbed)
Kicker speed determines minimum damping ring circumference.
We are investigating a “Fourier series kicker”: use a series of rf cavities
to create a kicking function with periodic zeroes and an occasional
spike. Perhaps closer bunches/smaller damping ring will be possible?
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
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. TDR):
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Linac beam
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. . bunches, 337 nsec spacing
•2820
(~. .300 kilometers)
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•Cool an entire
pulse
in
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damping
rings
before
linac
injection
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Introduction
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Leo Bellantoni
David Finley
Chris Jensen
George Krafczyk
Shekhar Mishra
François Ostiguy
Vladimir Shiltsev
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Fermilab
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University .of Illinois
Guy Bresler
Keri Dixon
George Gollin
Mike Haney
Tom Junk
Jeremy Williams
Cornell University
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Physics
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Gerry Dugan
Joe Rogers
Dave Rubin
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. project. is. part of the
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This
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university-based
Linear
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Collider. R&D
effort
(LCRD/UCLC)
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Participants
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George Gollin, Fourier engineering… Victoria, LC 2004
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Fast kicker specs (à la TDR):
•  B dl = 100 Gauss-meter = 3 MeV/c (= 30 MeV/m  10 cm)
• stability/ripple/precision ~.07 Gauss-meter = 0.07%
Physics
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. bunch “collides”
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. pulses traveling
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TDR design:
with
electromagnetic
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in the
a series
of .traveling wave structures.
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Hard. to turn. on/off
fast enough.
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. à la TDR
TESLA damping
ring
kicker
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damping ring beam
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Fourier kicker
damping ring beam
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George Gollin, Fourier engineering… Victoria, LC 2004
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kicker field vs. time
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kicker field vs. time
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Kicker is always on.
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kicker .
Fields when kicker is
empty of beam are
irrelevant.
Synthesize kicker impulse
from Fourier components
of something with good
peaks and periodic zeroes.
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conventional
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Kicker
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zero. when unkicked
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bunches pass through..
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Since it’s hard to turn on/off, why
not leave
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it ON all the time?
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Three. functions with
good peaks
and . zeroes:
#1
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1.. part of the .series
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. d function (w. is linac
. frequency):
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Fourier amplitudes
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a. k
k=N
k
N=16
A problem: field has non-zero
time derivative at the zeroes.
Bunch head and tail experience
different (non-zero) fields.
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George Gollin, Fourier engineering… Victoria, LC 2004
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“Features” (peaks and zeroes)
are evenly spaced.
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Three. functions with
good peaks
and . zeroes:
#2
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Fourier amplitudes
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2.. “square” of. last
zero
slope…
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. zeroes also have
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k=N
k
Better… but frequencies
range from 3 MHz to 180
MHz.
kicker
fields
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kicker fields
0.04
0.8
0.03
A 3 MHz RF device is very
different from a 180 MHz
device.
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
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Three. functions with
good peaks
and . zeroes:
#3
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3.. high-frequency
modulate:
this
way
fractional
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bb bbbbbbbbbbbb
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Fourier amplitudes
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k=N
k
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2N
kicker
This is what we’re actually
studying now, but with
N = 60 and  = 10:
1.78 GHz ± 10% bandwidth
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(Graph uses N = 16,  = 4.)
fields
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damping
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We. don’t want
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the kicker
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Fourier series kicker
would be located in a
bypass section.
kick
While damping, beam
follows the upper
path.
During injection/extraction, deflectors route beam through bypass
section. Bunches are kicked onto/off orbit by kicker.
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Damping ring .operation with an
FS kicker
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fhigh +
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Original idea: kicker would be a series of 60 “rf cavities,” each
oscillating at one of the desired Fourier components. (60 cavities
would allow the damping ring to fit into the Tevatron tunnel.)
A bunch “sums” the impulses as it travels through the system.
There are lots of cavities, but they’re all nearly the same.
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extraction path
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fhigh +
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kicker rf cavities
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So what is it, actually?
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Summing signals in a. single cavity…
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Well
yes, maybe…
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• dumb: build a 3MHz cavity and drive it so that multiple modes
are populated. (cavity is huge, lots of modes to control…)
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• promising: launch different frequencies down a long
(dispersive) waveguide to a low-Q cavity. Send the frequency
with slowest group velocity first, fastest last. Signals arrive at
cavity properly phased to make a short pulse. Q ~ 25 cavity can
support an acceptable range of frequencies. (This was originally
Joe Rogers’ idea.)
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Is there another way to sum the
Fourier
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. guide compresses
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(Commercial
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RF
amplifier
~100kW,
but
compression
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generates large peak power for kicking pulse in low-Q
cavity.
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RF
amplifier
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function
generator
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kicker
cavity
(dispersive) wave guide
c
upstream
end
of
waveguide
fields
including
cavity
response
kicker
fields ,
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ns
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wave guide group velocity vs. frequency
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Pulse .compression kicker
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.
.
.
.
.
. .
.
.
.
. kicker
cavity
.
.
.
.
.
(dispersive)
wave guide
.
.
.
.
.
.
.
. .
.
.
.
.
.
.
.
.
.
.
. .
.
. .
.
function. .
RF
.
generator. amplifier
.
.
.
.
.
..
.
.
.
Cavity center.
frequency is 600 times.
linac frequency, 10
times damping ring
frequency.
.
.
.
.
.
.
.
.
.
..
.
Kicker
cavity
. field for.
.
.
. .
~6. ns. bunch spacing.
.
.
.
..
.
.
.
.
.
.
..
.
.
fields
0.75
Field inside cavity
0.5
kicker fields ,
10 ns
1
0.25
0.5
-1.5
10
-7
-1
10
-7
-5
10
-8
5
10
-8
1
10
-7
1.5
10
-7
-0.25
-1 10
-8
-5 10
-9
5 10
-9
1 10
-8
-0.5
-0.5
....
. ..
. . .
. .. .
. .
. .
.
.
.. .
.
.
.
George Gollin, Fourier engineering… Victoria, LC 2004
.. .
.
.
..
-1
. .
-0.75
.
I
Physics
P
llinois
±10 ns
13
.
.
.
.
.
Trace
the signal from kicker back
to amplifier
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
end of waveguide
fields
including
.
.
.
.
.
..
.
.
.
. .
.
.
.
..
downstream
.
.
.
.
.
.
.
.
.
. kicker
cavity
.
.
.
.
.
.
.
.
.
.
.
(dispersive)
wave guide
.
.
.
.
. .
.
.
.
.
.
.
. .
.
.
.
.
.
.
.
..
.
downstream
. .
.
.
.
Waveguide peak
field
.
is about 1/10 that
inside the cavity.
Note phase shift
relative to cavity
field.
.
function. .
RF
.
generator. amplifier
.
.
.
.
.
.
.
.
..
.
.
Wave
guide. field
at
.
.
. .
cavity
entrance.
. .
.
.
.
..
.
.
.
.
.
.
..
.
.
cavity
response
0.1
end of waveguide
fields including
cavity response
0.05
Wave guide field at
cavity entrance
0.1
0.05
-1.5
-1 10
-8
-5 10
-9
10
-7
-1
5 10
10
-7
-9
-5
1 10
10
-8
5
10
-8
1
10
-7
1.5
10
-7
-8
-0.05
-0.05
.
.. .
.
.. .
.
.
.
..
.
.
George Gollin, Fourier engineering… Victoria, LC 2004
....
. ..
. . .
. .. .
. .
. .
. .
±10 ns
.
I
Physics
P
llinois
-0.1
14
.
.
.
.
.
Field
at the downstream end of the
wave guide
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
fields including
fields
.
.
.
.
..
.
.
.
.
Wave guide field at
z = 45 meters
.
.
.
.
.
.
.
. .
.
end of waveguide
.
. kicker
cavity
.
.
.
.
.
.
downstream
.
.
.
.
.
10 % from
end of waveguide
.
.
.
.
(dispersive)
wave guide
.
..
.
10 % from downstream
.
.
.
.
Note incomplete
pulse compression at
this point.
. .
.
.
.
.
.
.
.
.
.
.
. .
.
. .
.
function. .
RF
.
generator. amplifier
.
.
.
.
.
..
.
.
.
.
.
..
.
.
.
Wave
guide. field
.
.
. .
90%
down
the
length
. .
of the. wave guide..
.
.
.
.
..
.
.
.
.
.
.
..
.
.
including
cavity
response
0.06
0.04
cavity response
0.06
0.02
0.04
0.02
-1.5
1 10
-8
2 10
-8
10
-7
3 10
-8
-1
4 10
10
-7
-8
-5
5 10
10
-8
5
10
-8
1
10
-7
1.5
10
-7
-8
-0.02
-0.02
-0.04
-0.04
0 - 50 ns
....
. ..
. . .
. .. .
. .
. .
.
.
.. .
.
.
.
George Gollin, Fourier engineering… Victoria, LC 2004
.. .
.
.
..
-0.06
. .
.
I
Physics
P
llinois
-0.06
15
.
.
.
Field 4/5 of the way down the. wave guide
.
.
.
.
.
.
.
.
.
.
.
.
. .
.
.
.
.
.
(dispersive)
wave guide
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
50 % from
downstream
end of waveguide
fields
.
.
.
..
.
.
..
.
.
.
.
.
.
.
.
.
.
. kicker
cavity
.
.
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. .
.
.
..
.
. .
.
.
..
function. .
RF
.
generator. amplifier
.
.
.
.
.
.
.
.
Wave
guide field
.
.
. .
.
50% .down
the length
.
.
of the wave guide.
.
.
.
.
.
.
.
.
..
.
.
.
including
cavity
response
Wave guide field at
z = 25 meters
0.02
0.01
5
10
-8
1
10
-7
1.5
10
-7
2
10
-7
2.5
10
-7
3
10
-7
-0.01
.
.. .
.
.. .
.
.
.
..
.
.
George Gollin, Fourier engineering… Victoria, LC 2004
....
. ..
. . .
. .. .
. .
. .
. .
.
I
Physics
P
llinois
-0.02
16
.
.
.
.
.
.
.
.
.
.
.
.
Field half-way down the wave
guide
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
upstream
end of waveguide
fields
including
cavity
.
.
.
.
.
.
.
.
.
..
.
.
.
. .
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
. kicker
cavity
.
.
.
.
.
.
response
0.015
0.01
..
.
.
.
.
.
.
0.005
Pulse compression,
plus energy storage
in the cavity!
1.5
10
-7
2
10
-7
2.5
10
-7
3
10
-7
3.5
10
-7
4
10
-7
-0.005
-0.01
.
.
.
.
.. .
.
.. .
George Gollin, Fourier engineering… Victoria, LC 2004
..
.
.
. .
-0.015
.
I
Physics
P
llinois
....
. ..
. . .
. .. .
. .
. .
17
.
.
.
.
.
.
.
.
(dispersive)
wave guide
.
.
.
.
.
.
.
. .
.
.
. .
.
.
..
Note that peak field
is about .018 here, in
comparison with 1.0
inside cavity.
.
.
Field at upstream
end
.
of the wave guide.
.
. .
.
.
.
.
.
.
function. .
RF
.
generator. amplifier
.
.
.
.
.
.
..
.
.
.
.
.
.
.
..
.
.
.
.
.
.
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.
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.
.
.
.
.
.
Field at entrance to the wave
guide
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Into wave
guide last
.
8
7
1
10
9
2
1.3
10
2
9
3
10
3
9
4
10
9
4
5
10
9
5 GHz
....
. ..
. . .
. .. .
. .
. .
.
.. .
.
.. .
.
.
.
..
George Gollin, Fourier engineering… Victoria, LC 2004
. .
.
.
.
18
.
.
.
.
.
.
.
.
vs . frequency
.
8
.
.
.
.
.
0
I
.
.
..
8
0
Physics
P
llinois
.
10
. .
.
5
.
..
10
.
.
1
..
.
.
.
10
.
1.5
.
.
.
.
0.5 c
Into
.
guide
first
.
10
.
wave
.
2
8
.
.
10
velocity
. .
.
2.5
.
group
.
.
.
.
.
.
.
. .
.
..
.
.
.
.
.
c
.
. .
.
guide.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
1.3
GHz cutoff
frequency
wave. .
.
. .
.
.
.
.
.
Group velocity vs. frequency
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. .
.
.
..
.
.
.
.
.
.
.
.
.
.
..
.
.
.
. of
.
.
Unlike
Fourier
series kicker, in . which bunches.
the. effects
.
. .
.
.
. .
. .
. sum.
different
frequencies,
this
design
uses
the
to
form
the
. cavity
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
System is linear, so low-power tests can be used to evaluate
concept.
(Fermilab is interested in pursuing this.)
Programmable function generator can be reprogrammed to
compensate for drifts and amplifier aging.
Underway: studies of how sensitive kicker is to parameter errors:
•What if Q isn’t exactly 25?
•What if amplitude, phase, losses in wave guide,… drift?
.
.
.
.
.. .
.
.. .
George Gollin, Fourier engineering… Victoria, LC 2004
..
.
.
. .
.
I
Physics
P
llinois
....
. ..
. . .
. .. .
. .
. .
19
.
.
.
.
.
.
.
“sum”
.
.
.
.
. .
.
.
. .
.
..
.
.
.
.
..
.
.
.
.
.
.
.
..
.
.
.
..
.
.
.
.
.
.
.
Pulse compression kicker
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. .
.
..
..
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
..
. .
.
. by wave guide
.
.
Cavity response
to
drive
fields
delivered
depends
on
Q.
.
.
.
.
.
. .
.
.
.
.
.
.
.
. cavity fields are not as expected.
If Q .is. different. from nominal
value,
. .
.
.
.
..
.
.
.
.
Cavity response
.
.
12
0.0006
Cavity
field
error
at ideal
zeroes
.
vs . time
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
12
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Q differs from nominal by 0.1%
0.0005
10
0.0004
8
kicked bunch: 6.310-4 error
0.0003
6
1.65
1.7
1.75
1.8
1.85
1.9
1.95
0.0002
0.0001
50
60
pT error vs. bunch number (< 710-4)
.
.
.
George Gollin, Fourier engineering… Victoria, LC 2004
..
.
.
....
. ..
. . .
. .. .
. .
. .
.. .
.
40
.. .
30
.
I
Physics
P
llinois
20
.
10
. .
Cavity response vs. f
20
.
. .
.
. .
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
An example: what if Q 
25?
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. .
.
..
.
..
.
.
.
.
.
.
.
.
..
.
.
.
..
. .
.
.
.
.
. a relativistic
A0 photoinjector
lab
at
Fermilab
produces
(16 MeV
.
.
.
.
.
.
.
.
.
.
.
.
.
. .
. . 50 MeV in a few months),
now,
bunched
low-emittance
electron
.
.
.
.
.
.
.
.
.
.
beam. (It’s. rather like a TESLA injector.)
..
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. .
.
. .
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
This should be an excellent facility for kicker studies!
First order of business: understand how well the A0 beam will work
for kicker tests
Physics
P
.
.
.
.
.. .
.
.. .
George Gollin, Fourier engineering… Victoria, LC 2004
..
.
.
. .
llinois
.
I
....
. ..
. . .
. .. .
. .
. .
21
.
.
.
.
.
.
.
EOI submitted to Fermilab to. begin tests
..
.
.
.
.
.
.
.
.
.
.
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.
.
.
.
.
.
. .
.
.
..
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
. be.
. calculable and can
Start
with a simple
kicker
whose
properties
are
.
.
.
.
.
.
.
.
. .
. .
.
.the A0
.
.
measured
independently
of
on
electron. beam..
. its effects
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
Most important: how well can we measure a device’s amplitude and
timing stability with the A0 beam?
flanges
conventional beam pipe
BPM
BPM
conducting rods
BPM’s are separated by about a meter.
.
.
George Gollin, Fourier engineering… Victoria, LC 2004
.. .
.
.
.
.
.
.. .
.
I
Physics
P
llinois
....
. ..
. . .
. .. .
. .
. .
..
ceramic
beam pipe
BPM
. .
BPM
conventional beam pipe
22
.
.
.
.
.
.
.
. .
.
..
.
.
.
.
..
.
.
. .
.
..
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Simple .kicker for initial. tests
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
. .
.
.
..
.
.
.
.
.
.
.
.
.
..
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
Two pairs of 50 m resolution
BPM’s determine deflection
to ± 100 mrad
.
.
.
.
.
Aluminum housing
alternate +HV feed
+HV feed
termination resistors
ceramic beam pipe
3 cm
down
-HV feed
.
.
.. .
.
.
.
.
.
.. .
~60 cm
George Gollin, Fourier engineering… Victoria, LC 2004
..
Physics
P
llinois
....
. ..
. . .
. .. .
. .
. .
. .
plan view
.
I
alternate -HV feed
23
.
. .
.
.
.
.
.
.
..
. .
. with ±750
. FNAL linac
.
.
Driving
kicker
volt
pulse
from
chopper
pulser
.
.
.
.
.
. .
.
.
.
.
.
.
.
.
.
will deflect
16 MeV
beam by
(See EOI for calculations.)
. . 3.3 mrad.
. .
.
.
.
.
.
. .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
Simple
kicker
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
. .
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.SLAC
parts. are on hand at Fermilab.
sent us .a ceramic
.
.
.
.
vacuum pipe. which is already flanged. . .
.
.
.
.
.
.
.
.
.
.
.
..
.
.
.
.
.
.
.
.
.
. .
.
We would like to assemble the kicker, developing instrumentation to
measure (“on the bench”) its field strength and time dependence in
collaboration with Fermilab’s technical division.
After we feel we understand the kicker we would like to install it in the
A0 beam to measure its properties there.
.
.
.
.
.. .
.
.. .
George Gollin, Fourier engineering… Victoria, LC 2004
..
.
.
. .
.
I
Physics
P
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Most. kicker
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Simple kicker
instrumentation
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The
on a real
TESLA
damping
ring
kicker
are
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shown
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quantity
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value
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precision
kicking field integral
100 Gauss-meters ±0.07 Gauss-meters
"off" field integral
0
±0.07 Gauss-meters
kicking pulse "flattop" at least 40 ps
less than 6 ns
pulse fall time
less than 64 ns
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
P
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I
pulse rise time
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Rough estimate
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time
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. calculation
. estimated 3%
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A most naïve
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accuracy
from the BPM's and
stability
goal
of
0.07%.
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If only BPM precision. contributed to the measurement
uncertainties (we
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should be so lucky!), it would take (3% / 0.07%)2  2000 pulses per
measurement point to reach this level of accuracy.
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Arbitrarily increasing this by a factor of three to 6000 pulses would
allow the 10 Hz A0 repetition rate to deliver one point's data in 10
minutes.
A scan of 100 points in which the relative timing of the arrival of the
beam and the firing of the kicker is varied could be done in a few
shifts.
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
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Rough estimate of running
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What
might. a .damping
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. .to fit
ring,
small
enough
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into the
Tevatron or
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HERA or tunnels,
actually look like?
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We had a small workshop
in March at Fermilab to
think about this.
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George Gollin, Fourier engineering… Victoria, LC 2004
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I
Physics
P
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6 kms, 6 straight sections,
25 wigglers.
this version:
16 March,
2004 ..
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Participants: ANL,
LBNL, SLAC, Cornell,
DESY, FNAL…
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Small Damping Ring Studies .at Fermilab
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Transverse damping time td 28 ms / 44 ms
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6.12 km
8 mm·mr
0.02 mm·mr
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. +/e.-) .
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Small
ring
(e
Dogbone
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5 GeV
5 GeV
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Horizontal emittance gex
Vertical emittance gey
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17
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8 mm·mr
0.02 mm·mr
28 ms / 50 ms
Current
Energy loss/turn
Radiated power
443 mA
160 mA
7.3 MeV / 4.7 MeV 21 MeV / 12 MeV
3.25 MW / 2.1 MW 3.2 MW / 1.8 MW
Tunes Qx, Qy
62.95, 24.52
-112, -64
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
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Chromaticities x, y
72.28, 44.18
-125, -68
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Energy
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Circumference
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Parameter
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Comparison
of the two
designs
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. out if it is
It
be interesting to see how various
optimizations
turn
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possible to. remove the .20 ns minimum bunch
spacing requirement.
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A small damping ring could be built and tested before linac
construction was complete. (Independent tunnels) This is an
appealing idea! It could allow beam to be injected into the linac as
soon as the main linac was under construction.
Exploration of technical issues associated with damping rings is
becoming a major focus of LC activity at Fermilab.
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Physics
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Comments
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•Dynamic aperture studies
•Instability studies
•Kicker work…
…all are underway.
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
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•Lattice design
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Fermilab.. damping ring
studies
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It is possible
that
TESLA
damping
ring
kicker
designs
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will allow the construction
of smaller rings.
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Simulations are encouraging; we will begin testing some of these
ideas over the next few months at Fermilab.
Kicker and damping ring are planned to become major activities
at Fermilab.
Stay tuned!
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George Gollin, Fourier engineering… Victoria, LC 2004
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Physics
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alternative
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Summary/conclusions
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