Transcript The International Linear Collider: A Detector Physicist

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The International Linear Collider:
A Detector Physicist Describes Accelerator
Physics to String Theorists
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George Gollin
Department of Physics
University of Illinois at Urbana-Champaign
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Doing something different
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. (mixed-signal
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• engineering
electronics
and mechanical devices)
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• software (large .analysis codes)
• theory/phenomenology (results from quantum field theory)
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I have been concentrating on ILC accelerator physics since mid2002. The tools are different:
• engineering (power RF and acoustics)
• software (small modeling codes and test beam data analyses)
• theory/phenomenology (classical mechanics, electrodynamics)
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I am really. a .detector
physicist. My usual tool. set:
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Classical physics as a research tool
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The work is. well-suited
to undergraduate participation.
In
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particular,
small
codes
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classical
physics
permit
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students to
work productively after only a few weeks.
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Doing something different
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So far:
• eight undergraduates, working on two separate projects
• one senior thesis, with a second in the pipeline
The students participate in planning, managing our Fermilab test
beam running, and developing models for systems we study.
It is a great deal of fun, but now we need serious support.
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We. .have been (we
were
the
first)
for
a
small
ILC
. proponents
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damping ring.
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The original damping ring design had a circumference of 17 km.
The UIUC/Fermilab/Argonne design has a circumference of 6 km.
The baseline design report specifies 6.6 km damping rings.
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We have an impact
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A linear collider
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Physics
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A highly simplified view of an e+e- linear collider
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preaccelerator
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5. GeV
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e± source
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120
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detector
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damping ring
250 - 500
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5 GeV
main linac
bunch compressor
final collimation
focus
The ILC accelerator complex will be incredibly complicated.
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The ILC will
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filled
with
cool
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interesting
devices,
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marvelous gizmos. .
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Many of them are easily described using classical mechanics and
classical electrodynamics.
For fun, here are some of the issues and devices that have
interested me.
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Really cool stuff
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What do we mean when we say
E  E  and E   E ?
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Fields of a charge in
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Sensors are 1. . meter from
the origin
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The
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frame
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As sensors B and B align,
they measure the electric. fields
EB and EB
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Two observers prepare to measure E
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As sensors A and A align, they measure the electric fields EA and EA
B
B
B
B
EB = EB
B
B
EA = EA
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A
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B
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EA = EA
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Q
The measurement EA = EA is made when Q is 1/ meters from sensor
A in the unprimed (stationary) frame.
When Q is 1 meter from sensor A, the sensor will measure a field that
is weaker by a factor of 1/ 2.
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= EB
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Two observers prepare to measure E
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
32
E 
as   0

when  1   sin  
2
2

32
 1;
q
4 0 r
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as   90
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2
q
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q
 4 0 r
Physics
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
4 0 r  2 1   2 sin 2  
E  E
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. . frame in .which
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The electric field
in
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q
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E ~ 1/2 and E ~ 
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Fields of a relativistic charge in uniform motion
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Field
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Note that the total number of field lines is the same in both cases.
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5.7 nm
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sy
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sx
nC)
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655
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(3.2
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e±.
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y
top view: beam traveling to the right
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beam coming out of the page
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21010
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y
z
I
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250 GeV
.
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number of bunches 2820
A bunch is 115 times
wider than it is thick…
Physics
P
llinois
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…and 458 times longer
than it is wide.
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bunch charge
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bunch
energy
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Bunch
parameters continue. .to
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evolve.
Here’s a .typical .set..
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ILC bunch parameters
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. . rest frame
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Bunch
is highly
relativistic.
(In its
it is ~147
m long!)
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B
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Fields near an ILC bunch
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eB
E
The fields just above/below the bunch are large in the lab frame:
E ~ 1.5 1011 V/m = 150 V/nm
B ~ 500 T
Energy density in the fields is appreciable: u ~ 1 keV/nm3
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. collide.
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and compresses
the
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as
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v  B force. is. . appreciable
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B
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.......................................................
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B
e+
B
Inside a bunch the focusing force increases with (vertical) distance
from the horizontal median plane of the bunches since B increases
The effect is significant: a naïve estimate shows an e± will oscillate
through the median plane a few times while the bunches cross.
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Particles oscillate around the horizontal median plane
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From Nick Walker’s USPAS Santa Barbara (2003) material:
http://www.desy.de/~njwalker/uspas/coursemat/pp/unit_7.ppt
George Gollin, The International Linear Collider
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Bunch
geometry
here
isn’t quite the same as current
ILC
specs
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http://www.slac.stanford.edu/~seryi/LCD_May28_2002/web/zxy.gif
play the animation…
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19
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Cool bunch collision simulation by Andrei Seryi
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It. also pitches
the. beams vertically if they don’t
hit head-on,
and
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. bunches cross. .
generally
makes a mess of. things .after the
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Approximate the vertical restoring force on an electron as linear
(note that change of variable to z = ct):
y( z )  ky ( z )
“Disruption parameter” Dy characterizes how strong this is:
Dy  k 3s
2
z
so that y( z )  
Dy
3s
2
z
y( z)
It’s a like a spring constant, scaled by sz2 to make it dimensionless.
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Beam position monitors
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Field at ±/2 is  times
stronger
than for a charge at rest.
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
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2 .
2
2
4
. . 0r 
1


sin
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.  
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E 
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4.9105.
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=
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The field falls off appreciably
when  changes by ~1/.
Field lines terminate on the image
charge that travels along the beam
pipe as a bunch as moves through
the accelerator.
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22
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Fields of a relativistic bunch inside a beam pipe
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e+
Magnitudes of image and bunch
charges are identical: 3.2 nC.
21010 e± (3.2 nC)
....
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George Gollin, The International Linear Collider
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Physics
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Field at the inner wall of a beam pipe
with 2 cm radius is 2.8 MV/m.
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Image. charge is concentrated in a .short
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cylinder of . the same z extent as the
.
bunch. It travels along
the vacuum
pipe, keeping pace with the bunch.
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image
charge .traveling
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along. inner wall of
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beam pipe with
radius r
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signal cable
signal current
The 3.2 nC image charge is spread
over a band of circumference 2r.
A BPM button with diameter d will
see ~0.5 nC  d/r if a bunch is
perfectly centered inside the pipe.
t
~1 kV into 50 W
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24
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George Gollin, The International Linear Collider
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Physics
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Pickup electrode for a beam position monitor
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Difference. . in signals
increases.. . with offset
. of the. bunch from .
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the . center of the beam pipe.
Sub-micron
resolution
is
possible.
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Position measurement with a BPM
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(x, y)
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25
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Here is one of the ~50 mm
resolution BPMs we use.
Our bunch charge is about
10% of an ILC bunch.
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26
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George Gollin, The International Linear Collider
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Physics
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We are using
the
16
MeV
e
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.
beam at the AØ photoinjector
lab for damping ring kicker
tests.
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Fermilab AØ BPM
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I am used to
thinking
of
systems
designed
to
see
single
“minimum
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.
ionizing” particles (singly
charged, relativistic particles):
wire
chambers, silicon tracking devices, scintillation counters, and
photomultiplier tubes. Best resolutions of dozens of mm and
hundreds of ps are typical for these kinds of devices.
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With so much charge present in a bunch, there are other ways to
measure position and time that are new to me.
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27
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George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
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Thinking in new ways
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“Phase detector” for bunch
timing
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28
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George Gollin, The International Linear Collider
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I
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Physics
P
llinois
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The AØ photoinjector
lab
uses
a
1.3
GHz
RF
system
to
power
its
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. nicely synchronized to a master
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accelerating
structure.
Everything
is
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.
oscillator
that
generates
the
original
1.3
GHz
signal.
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We can determine timing of beam-induced events with respect to the
RF clock with (to me) amazing precision. Here’s how…
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29
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George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
....
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Using the AØ RF system for timing
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Dispersion in a coaxial
cable broadens the signal to
a full width of ~1 ns.
V
t
~1 ns
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30
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George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
....
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The
device
produces
a very
..
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short bipolar signal
when
a
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bunch
passes .through. it. .
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Phase detector
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V
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I
Physics
P
llinois
resonant structure
.
1300 MHz AØ RF
1300 MHz
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V
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phase detector
signal
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1240 MHz.
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resonant
structure
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Phase detector signal path
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V
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Low pass
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resonant
structure
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1300 MHz
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60 MHz + 2540 MHz
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RF mixer
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I
Physics
P
llinois
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1300 MHz AØ RF
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1240 MHz
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V
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resonant
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structure
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phase detector
signal
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Phase detector signal path
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Mixer output. . contains
and difference
frequencies.
A
low-pass
..
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filter. transmits
only
the
60
MHz
component.
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. t   
sin 1300t  sin 1240
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1
1
cos 1300  1240  t     cos 1300  1240  t   
2
2
Note that  appears unaltered in the 60 MHz term.
 = 90° in the 1240 MHz signal (202 picoseconds) maps into  = 90°
in the 60 MHz signal (4.17 nsec).
Timing accuracy is 1240/60 times better than scope precision.
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33
..
George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
....
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Doing almost nothing yields 100 ps precision
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Down-mixed signal voltage
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20 ns
time
How well we can determine the relative start times for each of the
displayed signals? (Probably to better than 100 ps.) Divide by
1240/60 to obtain bunch timing precision. We think we’re going to
obtain a bunch timing accuracy of ~5 ps or better.
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34
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George Gollin, The International Linear Collider
. .
.
Physics
P
llinois
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AØ data
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Radiation from accelerating
charges
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35
..
George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
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observer:.
.
time t
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Retarded time: t   t  r  rQ  t   c
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Potentials measured by the observer depend on where the moving
charge was, not where it is right now: r  rQ  t   , not r  rQ  t  .
.
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.. .
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36
..
George Gollin, The International Linear Collider
. .
.
I
Physics
P
llinois
....
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r
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v t
rQ  t 
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rQ  t 
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.ˆ  t 
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Retarded time is (distance to charge) / c
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. r  r c 
1   r , t. 
3
.
V  r , t  . 
.d r 
4 0
r  r
all space
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. . and scalar
. . the vector
Including
potentials
are
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. retardation,
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m0 J  r , t  r  r  c  3
Ar ,t   
d r
4
r  r
all space
It is beautiful in its simplicity. But we differentiate the potentials to
calculate E and B, so retardation effects complicate the calculation:
....
. ..
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37
..
George Gollin, The International Linear Collider
. .
.
I
Physics
P
llinois
E  V  A t
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Calculating potentials using retarded time
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. . solution includes
The result of
the
differentiation
is
remarkable:
the
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electromagnetic
radiation.
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Qa
.
.
r  rQ 4 0 c 1  ˆ  v c 
2
3
.
ˆ
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1
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1 r only

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E
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v
For relativistic motion the 1  ˆ  v c  term dominates the angular
dependence so that radiation is emitted primarily along the direction
of motion.
3
The rms width of the radiated power is rms = 1/.
.
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38
..
George Gollin, The International Linear Collider
. .
.
I
Physics
P
llinois
....
. ..
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Differentiating the potentials to obtain E and B
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Electromagnetic radiation, in particular when a  v
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Calculate
power
radiation
.
.radiated in the usual way. For. synchrotron
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we. have
a  v ..
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Radiated power (GeV/sec) is P  4.23 103
E
4
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2
E is the electron’s energy (GeV),  is its trajectory’s radius of
curvature.
Radiated energy (GeV) per orbit is  E  8.85 10
E4

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39
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George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
5
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. use the same magnets to build a bigger
. energy…
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If we
ring
at
higher
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• ring size:   E.
• synchrotron power loss per bunch: P  E4/2
• number of bunches in ring: N  
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Cost ~ ($¥€ per unit length)  E + ($¥€ per MW RF)  E3
Linac cost scales linearly with E, but bunches only collide once.
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40
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
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Linear vs. circular machines
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Beamstrahlung
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41
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
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Beam-beam
induced
synchrotron radiation is called
beamstrahlung.
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Let’s. estimate
its importance
using
classical
electrodynamics:
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B
B
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B
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Vertical oscillations cause beamstrahlung
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............................................................ .....
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......................................................
......... .......................
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................... ......................... ........
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e+
B
B
B
B ~ 500 T; radius of curvature of a 250 GeV e+ is 1.66 m (!!)
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42
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George Gollin, The International Linear Collider
. .
.
I
Physics
P
llinois
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An electron takes about 1.7 ps to pass through the positron bunch.
So it might lose as much as 10 GeV due to beamstrahlung. (!!)
Beamstrahlung broadens the energy spectrum at the point of
annihilation and adds to the uncertainty in c.m. energy of a collision.
A real calculation yields
E  7.0 GeV,
n  1.65 e 
http://www.slac.stanford.edu/econf/C980914/papers/F-Th24.pdf
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43
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George Gollin, The International Linear Collider
. .
.
I
Physics
P
llinois
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 6 10
GeV/sec
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P  4.23
10
E
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Beamstrahlung radiated power
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Radiated power
(GeV/sec)
is
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Characteristic beamstrahlung photon energy
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cone. of .
synchrotron
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radiation
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1/
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Make
a rough
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beamstrahlung
photon
energy
using
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classical
electrodynamics.
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1/
observer sees all radiation emitted between
these two points
Observable radiation is emitted along an arc of length s = /r = 2/().
It arrives during a time interval t = s(1/v – 1/c) =  / (c 3).
c = 2/t and Ephoton ~ hc yields Ephoton ~ 8.7 GeV
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44
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George Gollin, The International Linear Collider
.
I
Physics
P
llinois
Exact (QED) expression for c is 50% larger.
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This
is not a good
thing: photons mixed in with. the colliding
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bunches
allow
large
numbers
of
soft
e
e
pairs
to
swirl
out
from
the
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IP.
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  e  e 
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e   e  e  e 
e e  e ee e
Use largest possible magnetic field in the detector to confine e to
small radii so they don’t wipe out the vertex detector.
Under discussion: SiD (“Silicon Detector”) with 5 T field, 5 m
diameter, 5 m length.
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45
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George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
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Beamstrahlung-induced problems
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Beam dynamics, briefly
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46
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George Gollin, The International Linear Collider
. .
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I
Physics
P
llinois
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. . with exactly
A. single beam
particle
the. “right”
momentum
and
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.
initial
position travels along
the (closed)
reference
orbit in an
ideal
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accelerator.
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Local “wavelength” of oscillations
varies along the reference orbit.
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Orbits of particles that remain
inside the machine’s acceptance
will oscillate around the reference
orbit.
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.
reference orbit
(gray line)
particle orbit oscillates
around reference orbit
l ~ separation between red marks.
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47
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
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Reference orbit
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particle orbit
n = 22.75
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48
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George Gollin, The International Linear Collider
.. .
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ds
 s
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I
.
reference orbit
for s the path length along the
reference orbit.
Physics
P
llinois
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More precisely:

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n
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 ~ l/2
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. of oscillations
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The
number
around
the .reference
orbit
in one turn
is.
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.
called
the
tune
of
the
accelerator.
Shown:
n
=
22.75.
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Tune and 
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Liouville’s theorem:
without dissipative effects
the area of the ellipse will
not change.
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The shape of. the ellipse
.
varies from place to place
along the reference orbit, but
its area remains constant.
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x
x
x
x
Beam’s emittance is the
area of the ellipse.
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49
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George Gollin, The International Linear Collider
..
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I
Physics
P
llinois
x
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x . is the distance
from. the
reference
orbit.
x and its. ..first derivative
x
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.phase plane.
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.
will
lie
on
an
ellipse
in
the
x,
x

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Phase space; Liouville’s theorem
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x
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Normalized emittance is defined as x
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x
The ILC’s normalized (vertical) emittance goal is
y = 0.04 mm.mrad
yielding a luminosity L = 21034 cm-2 s-1.
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50
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George Gollin, The International Linear Collider
. .
.
I
Physics
P
llinois
....
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The
beam’s emittance
(x) is the area of the ellipse.
Since
x.  is
.
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dx/ds,
x

is
an
angle,
not
a
velocity.
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Emittance
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…is. possible if we
cause
the beam to lose
energy. (That makes . the
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.
.
theorem not applicable.)
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We can collapse the ellipse considerably, as is done in a damping
ring. More about this later.
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
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Beating Liouville’s theorem…
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George Gollin, The International Linear Collider
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Polarized
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Physics
P
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Electrons from the photocathode are accelerated to ~120 kV, then
bunched, accelerated more, and eventually sent to a damping ring
to reduce the bunch emittance.
laser beam
Space charge effects
dominate the emittance
coming out of the
electron source:
y ~ 500 too big.
~2 cm
electrons
accelerating voltage
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53
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
photocathode
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This is where
begins: an intense laser
beam
blasts
a
.everything
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. liberate
“strained
GaAs”
photocathode
to
electrons.
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• circularly polarized
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• Epulse. ~ 2 mJ (81012 )
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• timing structure: 2820 pulses spaced 337 ns apart; repeat this
at 5 Hz.
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54
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
http://www.astec.ac.uk/id_mag/BCD/ILC_source_R&D_plan.pdf
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•. 800 nm wavelength. to. match .photocathode
band
structure
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Ti:Sapphire,
90%
circularly
polarized
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55
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http://www.slac.stanford.edu/cgi-wrap/getdoc/slac-pub-11686.pdf
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I
Physics
P
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http://www.astec.ac.uk/id_mag/BCD/ILC_source_R&D_plan.pdf
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. . with .slightly different
. . substrates
By. growing
lattice. sizes
it
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is possible
to
do
“band
gap
engineering.”
Photon
polarization
is
well
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preserved
by ejected
electrons.
80% seems
feasible.
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Photocathode
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George Gollin, The International Linear Collider
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+
e
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Physics
P
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150
GeV electrons
from
a helical
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. . linac . will pass through
. . the main
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undulator,
emitting
circularly
polarized
synchrotron
radiation.
Each
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electron
loses
3.23
GeV
in
the
process.
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Helical undulator positron source
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Photon beam power is. ~150 kW; spot size on a 0.4 radiation
length
conversion target is 0.75 mm.
.
collection
150 GeV e-
helical undulator magnet
100 - 200 m
conversion
Positrons from   e+e- conversions in the target are captured and
accelerated to 5 GeV for injection into a damping ring.
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George Gollin, The International Linear Collider
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Physics
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http://hep.ph.liv.ac.uk/~ibailey/helical/helical_hep2005_cockcroft.pdf
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Physics
P
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Several designs
being
considered.
Here
is
an
NdFeB
permanent
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magnet
version
with
a
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cm
period
and
0.8
T
field.
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Undulator magnet
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Beam electrons
move
in
narrow
helices
along
the
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undulator.
For
1
cm
spatial
period,
orbit
“corkscrew”
period
is
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-11 sec. .
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3.3310
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Photon energy from the undulator
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Radiation emitted during one turn arrives in an interval
1 1 
 1 
  1 cm      3.33 1011  2   1.94 1022 sec
2
v c 


Using  = 2 / and Ephoton ~ h yields Ephoton ~ 22 MeV.
Note that Ephoton ~  2 so that high “drive beam” energy is necessary.
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59
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
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. photon.
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Positrons
will
tend
to
exhibit
the
polarization
of
the
parent
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The . ILC baseline. design. document discusses
the possibility of an
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early upgrade (longer . undulator) to obtain 60% polarization
in the
.
e+ beam.
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SLAC E166 took data in 2005 to study production of polarized e+
using an undulator; it worked. “No surprises,” but they are still
analyzing data from their runs.
Emittance from the positron source: y ~ 500,000  too big.
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I
Physics
P
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Polarized positrons!
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George Gollin, The International Linear Collider
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Physics
P
llinois
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Emittance reduction in the
ILC damping ring
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. emittances. . of the e+ and
The damping
rings
need
to
reduce
the
. e
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beams
considerably
in
~
0.1
second.
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Also, the damping ring
needs to cool all 2820 bunches
at once, then
.
extract them to the main linac with 337 nsec bunch spacing.
.
injected  x,  y
extracted  x
extracted  y
electrons
10-5 m
8  10-6 m
0.02  10-6 m
positrons
10-2 m
8  10-6 m
0.02  10-6 m
The damping ring may be the ILC’s most challenging subsystem.
.
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62
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
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Damping ring issues
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Since synchrotron
radiation
is
nearly
parallel
to
the
particle’s
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. longitudinal and transverse .
.
velocity,
radiation
reduces
both
the
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. orbit.
momentum
components
of
the
particle
relative
to
the
reference
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RF system only restores the longitudinal component.
RF
pz
px
after
radiation
after
RF
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63
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. .
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I
Physics
P
llinois
before
radiation
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Damping via synchrotron radiation
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Damping time
is
inversely
proportional
to
how
rapidly
the
particle
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loses
. .
. energy via radiation:
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2E 
D 
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Small radius (hard bend) reduces damping time. But there is a
minimum (equilibrium) horizontal emittance that can be obtained
due to the discrete nature of photon emission.
Damping ring uses wiggler magnets to speed up the process. Even
so, vertical emittance takes 8D to drop sufficiently.
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Physics
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Damping time
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Original
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circumference damping
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ring (!!)
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“Dogbone” shape would put most of it in the main linac tunnel but:
• access for repairs is not possible when linac is powered
• stray fields from RF system klystrons may disrupt DR beam
Why is it so long?
Because…
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ILC
main linac
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• 2820
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• Cool
an .entire. pulse .in the damping rings
before linac injection
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Damping ring beam (TESLA TDR):
• 2820 bunches, ~20 nsec spacing (~ 17 kilometers)
• Eject every nth bunch into linac (adjacent bunches are undisturbed)
Kicker speed determines minimum damping ring circumference.
Large circumference is worrisome. Tricky beam dynamics?
Wigglers used to cool beam: ~400 m of them.
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Physics
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Original design: 17 km circumference
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If so,
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.figured out
What
if we
a. faster
kicker?
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The problem with the kicker: it is hard to turn on/off quickly.
Two approaches we’re exploring (UIUC + FNAL + Cornell):
1. brute force: robust, faster HV switch.
2. a new kind of kicker that is always running.
In tandem with kicker studies we’ve been investigating a damping
ring lattice for a 6 km ring.
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George Gollin, The International Linear Collider
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Physics
P
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A 6.6 km ring is now the baseline recommendation!
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Thinking differently
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Physics
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ILC damping ring stripline
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A bunch “collides”
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opposite
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Hard
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turn. on/off fast
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Fast kicker specs (à la TESLA TDR):
•  B dl = 100 Gauss-meter = 3 MeV/c (= 30 MeV/m  10 cm)
• stability/ripple/precision ~.07 Gauss-meter = 0.07%
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Physics
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Brute force: stripline kicker
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Start
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kicker
whose properties are calculable and .can be.
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understood independently
of those of the A0 electron
beam.
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Most important: how well can we measure a device’s amplitude and
timing stability with the A0 beam?
A0 runs at 1 Hz, so performance demands on DAQ and offline
analysis processing are not severe.
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Physics
P
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Measuring electrode geometry before final assembly
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Physics
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Physics
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Final assembly of the kicker
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16
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. very .
First
significant
data
were
written
August
11,
2005.
That
was
a
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good day!*
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I
Physics
P
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*You have no idea… come to my other talk.
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Test it in the FNAL AØ photoinjector beam
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We test the stripline kicker in Fermilab’s 16 MeV e- beam.
100W device, 1 cm gap, 15 mrad deflection.
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Physics
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Stripline kicker in A0, looking upstream
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Chris
Jensen
and
colleagues
at
FNAL
built
it. for us.
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Physics
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HV pulsers
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Start with. . a Fermilab
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HV pulser: ±750
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DAQ uses an oscilloscope as a transient digitizer
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Event display, 10 pulses
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Physics
P
llinois
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FID Technology
F5201
Pulser. . Parameters
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. • Dual channel: +/-. 1kV
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• 0.5% - 0.7%
amplitude
stability . .
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• 0.7 ns rise time,
2.0 ns top of pulse, 1.2 ns fall
. time
• 3 MHz max. burst rate, 15 kHz max. average rate
• <20 ps timing jitter
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FID pulser: much faster, but stability unclear
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FID HV: ±1 kV, few ns length
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I
prediction
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Nothing is calibrated yet, and
we have programming artifacts
Physics
Pto remove…
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It kicks the beam! First FID HV pulser data
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As measured after the A0 stripline kicker
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Physics
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llinois
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It broke. Pulse train failure:
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We . tried to generate
pulse
trains with ILC-like
timing structure..
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Pulser burst mode appears to have failed after allowing the FID to
run over night.
• Observed 1st pulse parameters still near nominal
• Trailing pulses do not have stable amplitudes
Cornell met with FID engineer to discuss evaluation and repairs.
Pulser was repaired, then broke after running for a month.
Improvements may make it more reliable.
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Physics
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llinois
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Characterizing
to beam using UIUC DAQ. system
. kick
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Present Status
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Fourier series pulse
compression kicker
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Physics
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Fields when kicker is
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irrelevant.
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kicker .
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conventional
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Kicker
field needs to be
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zero. when unkicked
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bunches pass through..
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damping ring beam
kicker field vs. time
Synthesize kicker impulse
from Fourier components
of something with good
peaks and periodic zeroes.
Fourier kicker
damping ring beam
Kicker is always on.
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84
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
kicker field vs. time
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Since it’s hard to turn on/off, why not leave it
ON all the time?
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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:
~1.8 GHz ± 10% bandwidth
-50
50
100
150
-0.5
85
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-100
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-150
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I
Physics
P
llinois
0.5
....
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(Graph uses N = 16,  = 4.)
fields
1
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bb bbbbbbbbbbbb
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A. high-frequency
the .fractional
.
.modulated signal: this reduces
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bandwidth.
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Fourier amplitudes
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A function with good peaks and zeroes
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injection/extraction
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damping
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We. don’t want
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beam
. to go through
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the kicker
until we’re
.
ready to extract.
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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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86
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George Gollin, The International Linear Collider
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I
Physics
P
llinois
....
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Damping ring operation with an FS kicker
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. .
Construct
a. kicking
pulse
from a . sum
of. its Fourier
.
. .components..
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.
.
Combine
this
with
a
pulse
compression
system
to
drive
a
small
number
.
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.
of low-Q cavities.
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Illinois, Fermilab, Cornell are involved.
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87
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Physics
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llinois
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Fourier series pulse compression kicker
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Into wave
guide last
.
8
8
7
1
9
2
1.3
10
2
9
3
10
3
9
4
10
4
9
5
10
9
5 GHz
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0
10
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10
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5
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10
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1
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10
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1.5
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8
0
I
.
0.5 c
Physics
P
llinois
.
10
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2
8
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10
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.
2.5
.
Into wave
.
guide
first
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vs . frequency
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.
velocity
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group
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Group velocity
vs.
frequency
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1.3
GHz cutoff
frequency
wave. .guide .
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upstream
end of waveguide
fields
including
cavity
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. kicker
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cavity
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(dispersive)
wave. guide
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Note that peak field
is about .018 here, in
comparison with 1.0
inside cavity.
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Field. at upstream
end
.
of the wave guide.
.
function. .
RF
.
generator. amplifier
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.
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
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89
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. .
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I
Physics
P
llinois
-0.015
.
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Field at entrance to the wave guide
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Maximum amplitudes:
•entering ~0.016
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90
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Physics
P
llinois
~0.1
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•exiting
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Pulse compression!
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Waveguide compresses pulse
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..
kicker
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. kicker
.
cavity
.
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
-0.75
.
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.. .
91
..
George Gollin, The International Linear Collider
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frequency is 600 times.
linac frequency, 10
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Signal inside
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(Electrical and Computer
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work.
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We do not have previous RF engineering experience, so we’re learning
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We discuss things with Fermilab’s RF group. When we are further along,
they’ll drive south to spend a few days at UIUC working with us.
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Since then we’ve borrowed real
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Physics
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using aluminum
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Initial
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3. use the stripline kicker to study the timing/stability
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4. build a single-module pulse compression kicker
5. study its behavior at AØ
6. perform more detailed studies in a higher energy, low
emittance beam (ATF??)
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Recent progress
is . even
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now! Single
crystal
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cavities being manufactured
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Physics
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Long bunch spacing
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• . Electroweak. symmetry
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almost certainly will
reveal itself in the 100 GeV
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to 200 GeV mass
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range.
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• If nothing is there, the wheels come off the bus. Everything goes
crazy.
• Even if there’s a higgs, there are enormous cosmological constant
problems without something else (SUSY?)
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Physics at the ILC
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Physics
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The role of LEP in .
refining our
understanding of the
Standard Model is an
example.
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Both
have been
necessary.
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Precision
measurements
experiments:
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Physics at the ILC
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…is mixed.
Our confidence in our. predictions
is influenced
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optimism! .
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• SU(5) and proton decay
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Our success at predicting the unknown…
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• value of / in K   decay (direct CP violation)
We will need both LHC and ILC to understand the physics of
electroweak symmetry breaking
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In stock
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We may be closer than we think
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Physics
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Dark matter: 22.6%
Standard Model
Physics: 4.4%
We will need a goodly amount of data to understand things.
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Politics
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2. “The key to 'revolutionary' social change in
modern societies does not therefore depend, as
Marx had predicted, on the spontaneous
awakening of critical class consciousness but
upon the prior formation of a new alliance of
interests, an alternative hegemony or 'historical
bloc', which has already developed a cohesive
world view of its own.” (quoted by M. Stillo from
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1. The evolution
of
events
is
chaotic,
not
smooth.
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. take
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We
to
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advantage
of opportunities that may arise.
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Will it ever get built?
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Antonio Gramsci
1891 – 1937
Prison Notebooks
(“Hegemony”)
Williams, 1992: 27 in http://www.theory.org.uk/ctr-gram.htm)
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1. . “RIA for. .Illinois”. task force run
by the Illinois Department
for
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. and Economic Opportunity
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Commerce
(DCEO).
Argonne,
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Fermilab,
and
Illinois
Universities
had
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participants.
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2. Considerable strengthening of the Fermilab – Argonne
alliance
has taken place in the last year or two.
3. RIA, ILC, proton driver, and APS direct injector linac are all
superconducting machines that could be built in Illinois. DCEO
appeared to understand that a wider scope for its RIA advocacy is
appropriate. This is still evolving.
4. This was a near-miss: DCEO lost interest when RIA RFP was
postponed. But we learned something from this.
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State of Illinois efforts
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Office
of Science
has. now
stated. that
the. U.S. proposal
to become
the.
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ILC host
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Apparently OS
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reduction
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total
project
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cost relative to what we presently expect ILC to cost. .
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Recent news from Ray Ohrbach, Director, Office of Science of DOE.
If we can:
• show that ILC has good support in HEP (and other physical science) community
• demonstrate that US share will be ~ $3.5B
Then ILC will become a presidential initiative for a 2011 construction
start.
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University R&D
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Accelerators
are BIG, EXPENSIVE
devices.
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Many university
HEP groups have concentrated
on detector
projects,
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perhaps because they believe these are:
• more suitable in scale for a university group
• more practical, given their prior experience in detector
development.
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Is this really true? Should university groups stay away from accelerator
physics projects?
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Can university groups do accelerator physics?
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. are interesting, important projects .whose scope is ideal
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There
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The (inter)national labs welcome our participation and will help us
get started, as well as loaning us instrumentation.
Many projects involve applications of classical mechanics and
classical electrodynamics. These are perfect for bright, but
inexperienced undergraduate students.
The projects are REALLY INTERESTING. (Also, it’s fun to learn
something new.)
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Of course university groups can do
accelerator physics!
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January,
2002:
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• FNAL .was focused on Run II problems.
LC wasn’t on the lab
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directorate’s radar.
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Engaging the university HEP community
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• most university LC groups were already affiliated with SLAC;
most were doing detector simulations.
• there was little planning underway to attract new groups (for
example, with Fermilab orientations).
That wasn’t good!
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8/02
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9/02
9/02
separate accelerator and detector committees
review proposed work for both agencies
9/02
UCLC proponents revise
project descriptions
10/02
10/02
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proposal coordinators create new document combining revised
LCRD and UCLC projects, then transmit to DOE and NSF.
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UCLC proponents write
“project descriptions”
proposal coordinators create one unified document
combining LCRD and UCLC projects
LCRD proponents revise
subproposals
Physics
P
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LCRD proponents write
“subproposals”
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7/02
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ALCPG working group leaders
offer. suggestions
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for revision, collaboration with other
. . groups, etc.
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UCLC (NSF)
proponents
write
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We organized ourselves
LCRD (DOE) proponents
write
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short project
descriptions
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71. new projects
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47
. U.S. universities
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6 labs .
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22 states
11 foreign institutions
297 authors
2 funding agencies
two review panels
two drafts
546 pages
8 months from t0
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117
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*planning grant only
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Funded by NSF* and DOE
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…renewal submitted November 2003
…third year submitted February 2005
…fourth year submitted January 2006
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The result:
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Physics
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The result, first year
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University
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genuine interest from DOE and NSF in supporting .ILC R&D.
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The ILC R&D budget went up $30M this year. An unimaginative
approach would be to have all of it flow to the national labs and
none to the universities.
The unimaginative approach would be irresponsible and would
crash the U.S. HEP program.
Comments of the speaker…
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Physics
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llinois
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Ohrbach’s .message
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It’s time to get serious
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