43_1.PDF

Linac Based
Based Proton
Proton Drivers
Linac
Thomas P.
P. Wangler
Wangler
Thomas
LosAlamos
AlamosNational
NationalLaboratory
Laboratory
Los
LosAlamos,
Alamos,NM
NM87544
87544
Los
Abstract.
overviewis ispresented
presentedofofmodern
modernhigh-power
high-powerproton
proton linacs,
linacs, including
including aa survey
Abstract.
AnAnoverview
survey of
of worldwide
worldwide applications
applicationsthat
that
are
presently
underway.
The
recent
trend
towards
RF
superconducting
linacs
is
also
discussed.
We
present
some
are presently underway. The recent trend towards RF superconducting linacs is also discussed. We present somepreliminary
preliminary
results
from
beam-haloexperiment
experimentrecently
recentlycarried
carriedout
outatatLos
Los Alamos.
Alamos.
results
from
thethe
beam-halo
either
coupled-cavity linac
linac
either aa normal-conducting
normal-conducting coupled-cavity
(CCL),
or
SC
elliptical
cavities
for
high-velocity
(CCL), or SC elliptical cavities for high-velocity
particles.
is used
used throughout
throughout the
the
particles. Magnetic
Magnetic focusing
focusing is
high-velocity
section.
high-velocity section.
INTRODUCTION
INTRODUCTION
Proton
Protonlinacs
linacsarearecapable
capable ofof producing
producing highhighenergy,
high-intensity
beams
with
low
energy, high-intensity beams with lowemittance.
emittance.The
The
high-intensity
performance
high-intensity
performanceisispossible
possiblebecause
becausestrong
strong
focusing
cancan
bebe
easily
provided,
focusing
easily
provided,and
andbecause
becausethe
thebeam
beam
traverses
traversesthetheaccelerator
acceleratorinina asingle
singlepass,
pass, avoiding
avoiding
repetitive
repetitiveerror
errorconditions
conditionsthat
that lead
lead toto destructive
destructive
beam
resonances
as
in
high-current
beam resonances as in high-currentcircular
circularmachines.
machines.
The
linac
cancanoperate
The
linac
operateatatany
anyduty
dutyfactor,
factor,allallthe
theway
waytoto
100%
duty
orora continuous
100%
duty
a continuouswave
wave(CW),
(CW),which
whichresults
results
in in
acceleration
accelerationofofbeams
beamswith
withhigh
highaverage
averagecurrent.
current.At
At
present,
there
present,
therearearetwo
twomajor
majorR&D
R&Dtopics
topicsininthis
thisfield:
field:
1) 1)linac
linacapplications
applicationsofofRF
RF superconducting
superconducting (SC)
(SC)
technology,
technology,and
and2)2)beam
beamhalo
haloformation
formation inin highhighintensity
beams.The
Thelatter
lattertopic
topicisismotivated
motivatedby
bythe
the
intensity
beams.
desire
control
beam
lossesand
andradioactivation
radioactivationofofthe
the
desire
to to
control
beam
losses
accelerator,and
andthetheneed
needforforimproved
improvedreliability
reliabilityand
and
accelerator,
availability.
availability.
DC
Injector
RFQ
50-100
50-100keV
keV
DTL or IntermediateVelocity
Superconducting
Structures
2-7
2-7 MeV
MeV
CCL or
Superconducting-Elliptical
Structures
-100 MeV
MeV
~100
~1GeV
GeV
~1
FIGURE
of aa modern
modern high-power
high-powerproton
proton
FIGURE 1.
1. Block
Block diagram
diagram of
linac.
linac.
Table
for high-power
high-power linac
linac
Table II shows
shows the parameters for
projects
and/or being
being constructed.
constructed.
projects being
being designed and/or
Included
If + and H
H"- beams,
beams, as
as well
well
Included are
are linacs
linacs for both H
as
the
IFMIF
project
that
accelerates
aa deuteron
as the IFMIF project
deuteron beam.
beam.
More details
details about
about most of these
More
these linacs
linacs are
are presented
presented
other papers
papers at this workshop.
workshop. Most
inin other
Most of
of these
theselinacs
linacs
would deliver
deliver final
final beams in the megawatt
would
megawatt average
average
beam-power range,
range, which qualifies them
beam-power
them as
as highhighpower accelerators.
accelerators. Applications
Applications include
power
include linacs
linacs for
for
nuclear-waste transmutation
transmutation (KEK/JAERI,
nuclear-waste
(KEK/JAERI, KOMAC,
KOMAC,
TRASCO), neutrino
neutrino factory
factory (CERN
TRASCO),
(CERN SPL,
SPL, FNAL
FNAL 8-8GeV),
fusion-materials
studies
(IFMIF),
injectors
GeV), fusion-materials studies (IFMIF), injectors for
for
spallation-neutron sources
sources (LANSCE,
spallation-neutron
(LANSCE, SNS,
SNS, ESS),
ESS),and
and
proton radiography
radiography (LANSCE).
(LANSCE). The
proton
The LANSCE
LANSCElinac
linacisis
the
only
high-power
proton
linac
that
has
operated;
the only high-power proton linac that has operated;
firstbeam
beam was
was 30
30 years
years ago.
first
ago. ItIt should
should be
benoted
notedthat
thatthe
the
LANSCE
linac
is
the
only
one
that
does
not
have
LANSCE linac is the only one that does not have an
an
RFQ. The SNS, KEK/JAERI, and KOMAC linacs are
RFQ.
The SNS, KEK/JAERI, and KOMAC linacs are
in various stages of construction, and will become the
in various stages of construction, and will become the
first examples of the modern proton linac architecture
first examples of the modern proton linac architecture
that was just described.
that was just described.
Thispaper
paperis isdivided
dividedinto
intotwo
twoparts.
parts. First,
First, we
we
This
presentananoverview
overviewofofthe
thearchitecture
architectureofof modern
modern
present
high-powerproton
protonlinacs,
linacs, including
including a a survey
survey ofof
high-power
worldwide
applications
that
are
presently
underway,
worldwide applications that are presently underway,
and
we
discuss
the
recent
trend
toward
RF
SClinacs.
linacs.
and we discuss the recent trend toward RF SC
Then,
we
present
some
preliminary
results
from
the
Then, we present some preliminary results from the
beam-halo
experiment
recently
carried
out
at
Los
beam-halo experiment recently carried out at Los
Alamos.
Alamos.
HIGHPOWER
POWERPROTON
PROTONLINAC
LINAC
HIGH
OVERVIEW
OVERVIEW
Figure 1 shows a block diagram of a modern
Figure 1 shows a block diagram of a modern
proton linac. The first linac accelerating structure is
proton
The first linac
accelerating
structure
is
the linac.
radiofrequency
quadrupole
or RFQ,
which
thebunches,
radiofrequency
quadrupole
or
RFQ,
which
electrically focuses, and accelerates the beam
bunches,
electrically
focuses,
andvelocity
accelerates
therange
beamof
from the
DC injector
to a final
in the
from
the
DC
injector
to
a
final
velocity
in
the
range
about β= 0.06 to 0.12. The RFQ is followed byofa
about
p= 0.06 to 0.12. section
The RFQforis acceleration
followed by aof
magnetically-focused
magnetically-focused
section
for
acceleration
medium-velocity particles consisting of either ofa
medium-velocity
particles
consisting
either or
a
normal-conducting
drift-tube
linac of(DTL),
normal-conducting
drift-tube
linacThe (DTL),
or
“intermediate-velocity”
SC cavities.
third section,
"intermediate-velocity"
SC cavities.
thirdconsists
section,of
beginning at a beam velocity
of nearThe
β=0.5,
A new trend during the past decade has been the
A new
during
the past
decade
hasinbeen
interest
in trend
SC proton
linacs.
All the
linacs
Tablethe
I
interest
in
SC
proton
linacs.
All
the
linacs
in
Table I
except for LANSCE and IFMIF have superconducting
except
foreither
LANSCE
IFMIFdesign
have or
superconducting
sections
in theand
baseline
as an option.
sections
either
in the during
baseline
or as an
option.
Technology
progress
thedesign
past decade,
including
Technology
progress
during
the
past
decade,
including
a large increase in accelerating gradients for SC
acavities,
large higher
increase
in input
accelerating
SC
power
couplers,gradients
and pulsedfor
beam
cavities,
higher
power
input
couplers,
and
pulsed
beam
SC electron-linac experience at the TESLA Test
SC
electron-linac
at more
the TESLA
Facility,
has made experience
RF SC linacs
attractive Test
for
Facility,
has applications.
made RF SC linacs more attractive for
proton-linac
beginning at a beam velocity of near p=0.5, consists of
proton-linac applications.
CP642, High Intensity and High Brightness Hadron Beams: 20th ICFA Advanced Beam Dynamics Workshop on
High Intensity and High Brightness Hadron Beams, edited by W. Chou, Y. Mori, D. Neuffer, and J.-F. Ostiguy
2002 American Institute of Physics 0-7354-0097-0
43
flexibility that
that allows
allows for
for continuing
continuing operation
operation even
even
flexibility
with the
the failure
failure of
of an
an accelerating
accelerating module.
module.Fourth,
Fourth, aa
with
worldwide industrial
industrial capability
capability exists
exists for
for fabrication
fabrication
worldwide
of SC
SC cavities
cavities and
and cryomodules.
cryomodules. And
And finally,
finally, SC
SC
of
cavity performance
performance isis still
still improving
improving with
with higher
higher
cavity
accelerating gradients
gradients and
and higher
higher cavity
cavity quality
quality
accelerating
factors. The
The SNS
SNSlinac
linacisis scheduled
scheduledinin2006
2006totobecome
become
factors.
the first
first SC
SC proton
proton linac,
linac, and
andits
its operation
operation will
willprovide
provide
the
even more
more experience
experience for
for pulsed
pulsed SC
SC linac
linac operation.
operation.
even
SC
There are several significant advantages of SC
linacs that account for this trend. First, operating costs
costs
dissipation.
are reduced because of the reduced power dissipation.
affordable bore
bore
Second are the advantages of a larger affordable
radius, which relaxes alignment, steering,
steering, and
and
matching tolerances, reduces beam losses
losses and
and
and improves
improves beam
beam
activation, eases commissioning, and
with
availability. Third, the SC-linac design approach with
independently-phased
provides
short
cavities
provides
TABLE 1.
1. High
High Power
Power Linac
Linac Survey
Survey
TABLE
1^^^^^
Name
Duty IlIlllllillllllllll I'Average Energy
Rep
•iilllilPiBiiiiiiiiiStart
iPulse
iiiiiiii
iiiiiiiiiHi^^^
factor
rate iBiliiii
length iiiiiH^
(mA)
(mA) (GeV)
(MW) date
Ion
bunch
(msec)
LANSCE
+
-
H /H
(Hz)
0.625 100/20 6.2/1.2
16/9.1 1.0/0.1
1.0
60
6.0
38
-
H
2.8
1.2
50
50
14.0
6.0
22
114
ESS Long Pulse
H or H+
2/2.5
16.67
4.2
114/90
FNAL 8 GeV
H+/H-/e-
1.0
10
1.0
25
H-
0.5
50/25
2.5
25
1.25
CW
CW
100
CW
CW
100
CW
CW
100
H
H
CERN SPL
lESS
llIIIIShort
IIHPulse
^
KEK/JAERI 400 MeV
-
-
KEK/JAERI 600 MeV
TRASCO
IFMIF
KOMAC(KAERI)
+
H
D
+
+
-
H /H
Ave rage
(% )
-
SNS
Average
50
30
0.8
0.8/0.08
ON
1.4
1.0
1.4
2006
1.8
2.2
4.0
?
3.75
1.33
5+5
2010
0.25
8.0
2.0
?
0.7
0.4
0.35
0.6
0.21
?
30
>1.0
>30
?
0.040
10.0
2010
2X125 2X125
20
20
0.28/0.14 2006
0.1(1.0) 2.0(20) 2011(?)
component
component was
was aa unique
unique transverse
transverse beam
beam profile
profile
8
scanner
scanner8 consisting
consisting of
of aa thin,
thin, 33
33 µ|i diameter,
diameter, carbon
carbon
wire
wire for
for measurement
measurement of
of the
the dense
dense beam
beam core,
core, and
and aa
pair
pair of
of 1.5-mm
1.5-mm thick
thick scraper
scraper plates
plates totoprovide
providegreater
greater
sensitivity
sensitivity for
for measurement
measurement of
of the
the outer
outer halo
halo regions.
regions.
Each
wire
and
its
associated
pair
of
scraper
Each wire and its associated pair of scraper plates
plateswere
were
mounted
mounted on
on aa common
common movable
movableframe.
frame. As
Asthe
theprotons
protons
passed
passed through
through the
the wire
wire aa signal
signal was
was induced
induced from
from
secondary
secondary electron
electron emission.
emission. The
The scraper
scraper plates
plates were
were
water-cooled
water-cooled and
and were
were constructed
constructed of
of graphite
graphitebrazed
brazed
onto
onto copper.
copper. A
A signal
signal was
was induced
induced by
by the
the beam
beam
protons
protons that
that stopped
stopped in
in the
the plates.
plates. The
The data
data from
from the
the
wires
wires and
and the
the plates
plates were
were combined
combined using
using computer
computer
software
with
software to
to produce
produce aa single
single distribution
distribution
with aa
55
dynamic
intensity
range
of
about
10
:1.
dynamic intensity range of about 10 :1. Nine
Nine
measurement
measurement stations,
stations, shown
shown in
in Fig.
Fig. 2,2, were
were located
located
midway
midway between
between pairs
pairs of
ofquadrupoles;
quadrupoles;atateach
eachlocation
location
both
both the
the horizontal
horizontal and
and vertical
vertical projected
projected distributions
distributions
were
were measured.
measured. The
The first
first station
station was
was located
located after
after
quadrupole
4.
The
next
four
stations
were
located
quadrupole 4. The next four stations were locatedafter
after
the
the beam
beam had
had debunched
debunched at
at quadrupoles
quadrupoles 20,
20, 22,
22, 24,
24,
and
and 26.
26. The
The last
last four
four stations
stations were
were located
located after
after
quadrupoles
quadrupoles 45,
45, 47,
47, 49,
49, and
and51.
51.
LOS ALAMOS BEAM
BEAM HALO
HALO
EXPERIMENT
Theoretical
Theoretical research
research during
during the
the past
past decade
decade has
has led
led
to aa picture
picture of
to
of space-charge
space-charge forces
forces in
in mismatched
mismatched
beams as
beams
as aa major
major source
source of
of beam
beam halo
halo in
in high-current
high-current
proton beams.
proton
beams. The
The nonlinear
nonlinear space-charge
space-charge force
force
experienced by
experienced
by individual
individual particles,
particles, while
while the
the beam
beam is
is
undergoing coherent
undergoing
coherent rms-size
rms-size oscillations,
oscillations, slowly
slowly
drives some
drives
some particles
particles to
to larger
larger amplitudes
amplitudes to
to form
form aa
halo.
The
mechanism
has
been
described
by
a
particlehalo. The mechanism
has been described by a particle1,2,3
1 2 3 and identified as a parametric
core model,
core
model,
'
'
and
identified as a parametric
resonance. 22
resonance.
An experiment
been carried
An
experiment has
has been
carried out
out at
at Los
Los Alamos
Alamos
to test
test these
to
these ideas.
ideas. A
A 52-quadrupole
52-quadrupole FODO
FODO beambeamtransport channel
transport
channel was
was installed
installed at
at the
the end
end of
of the
the LowLowEnergy Demonstration
Energy
Demonstration Accelerator
Accelerator (LEDA)
(LEDA) 6.7-MeV,
6.7-MeV,
CW,
CW, 350-MHz
350-MHz RFQ
RFQ to
to carry
carry out
out aa first
first experimental
experimental
4,5,6
study
of
beam-halo
formation
in
a
study of beam-halo formation in a proton
proton beam.
beam.4'5'6
The channel
The
channel was
was long
long enough
enough for
for the
the development
development of
of
about
10
mismatch
oscillations,
enough
about 10 mismatch oscillations, enough to
to observe
observe the
the
initial stages
initial
stages of
of emittance
emittance growth
growth and
and halo
halo formation
formation
caused by
compliment
of
caused
by mismatch.
mismatch. A
A large
large
compliment
of beam
beam
7
7 The key diagnostic
diagnostics
was
provided.
diagnostics was provided. The key diagnostic
44
RFQ 44
RFQ
20-26
20-26
pure
pure breathing-mode
breathing-mode mismatch.
mismatch. The
The mismatch
mismatch
strength
was
measured
by
a
parameter
µ,
strength was measured by a parameter |i,which
whichequals
equals
the
beam
theratio
ratioofofthe
therms
rmssize
sizeofofthe
theinitial
initialmismatched
mismatched
beam
totothat
thatofofthe
thematched
matchedbeam.
beam.
45-51
45-51
The
1 Hz
Thebeam
beamfrom
fromthe
theion
ionsource
sourcewas
waspulsed
pulsedat at
1 Hz
totoallow
the
use
of
interceptive
beam
diagnostics.
The
allow the use of interceptive beam diagnostics.
The
measurement cycle consisted of the following steps.
measurement cycle consisted of the following steps.
The CW RFQ was de-energized with an RF blanking
The CW RFQ was de-energized with an RF blanking
pulse, when the ion source was turned on. While the
pulse, when the ion source was turned on. While the
75-keV dc-injector beam current increased, the beam
75-keV de-injector beam current increased, the beam
was injected into the unpowered RFQ. After about 2
was injected into the unpowered RFQ. After about 2
msec, the RF blanking pulse was removed; the RFQ
msec, the RF blanking pulse was removed; the RFQ
fields approached a steady state after another 5 µsec.
fields
after on
another
5 (isec.
The
ionapproached
source and aRFsteady
fields state
remained
for another
The
ion
source
and
RF
fields
remained
on
for
another
30 µs for data acquisition. The beam-profile
30 (is forweredata
The beam-profile
diagnostics
all acquisition.
in a fixed position
during a
diagnostics
were
all
in
a
fixed
position
measurement, and only one wire or scraper
wasduring
in the a
measurement,
and
only
one
wire
or
scraper
was
beam at a time; all other wires and scrapers were in
outthe
at a time; aperture.
all other wires
andorscrapers
ofbeam
the beam-pipe
The wire
scraper were
in theout
of theaccumulated
beam-pipe beam-induced
aperture. The charge
wire orover
scraper
beam
aboutin30the
beam Only
accumulated
beam-induced
charge
over10about
µsec.
the charge
collected over
the last
µsec,30
(isec.the
Only
thehad
charge
over the
last 10
(isec,
when
beam
best collected
approximated
a steady
state,
whenselected
the beam
approximated
a steady
state,
was
for had
thebest
recorded
data. Then
the DC
was
selected
for
the
recorded
data.
Then
the
DC
injector was turned off, and the beam profile scanners
FIGURE 2. Block diagram of the 52 quadrupole transport
FIGURE 2. Block diagram of the 52 quadrupole transport
channel showing the locations of the 9 profile scanners.
channel showing the locations of the 9 profile scanners.
Beam matching was done by adjusting the first four
Beam matching was done by adjusting the first four
quadrupoles to produce equal rms sizes in both x and
quadrupoles
to produce equal rms sizes in both x and
y. We estimated a measurement uncertainty for the
y. We estimated a measurement uncertainty for the
rms beam sizes about 50µ, caused mostly by
rms
beam sizes
mostly by
transverse
beam about
jitter. 50|i,
A caused
least-squares-fitting
transverse
beam
jitter.
A
least-squares-fitting
procedure was used based on measurements of
procedure
usedsizes
based
measurements
of
derivatives was
of rms
withonrespect
to the four
derivatives
of
rms
sizes
with
respect
to
the
four
matching quadrupole gradients. The Courant-Snyder
matching
gradients.
parametersquadrupole
of the matched
beamThe
canCourant-Snyder
be calculated
parameters
of
the
matched
beam
can be calculated
from the beam dynamics using the measured
values of
from
the beamrms
dynamics
usingPure
the measured
values of
the matched
beam sizes.
mode mismatches
the
matched
rms beam
sizes. Pure
mismatches
were
calculated
by scaling
the mode
Courant-Snyder
were
calculated
scaling
the and
Courant-Snyder
parameters
to the bydesired
values
finding the
parameters
to the
desiredquadrupoles
values andthatfinding
the
settings of the
matching
produced
settings
of
the
matching
quadrupoles
that
produced
these values. For example, multiplying each of the
these
values. For
example, multiplying
each of αthe
four transverse
Courant-Snyder
ellipse parameters
x,
four
transverse
Courant-Snyder
ellipse
parameters
βx, αy, and βy by the same scaling factor producedOx,
a
injector was turned off, and the beam profile scanners
px, Oy, and py by the same scaling factor produced a
Combined X Dlstn button
Combined X Dlstn button
0
A
0
1
o
\
S-
10
V
~
f"0>
"S
^
/
10
M
H « ———
1
10-10
-20
-10
0
10
20
- 1 5
- 1 0
PosFtlon (mm)
5
10
15
Combined X Dlstn button
Combined X Dlstn button
^
5
0
Position (mm)
10^
niiurF" T&iiin..
i
TflfttH^
jflfifir
/\
-H^
i
1 Qn
~l~
1 10~ 2
_i_
10~
+
10 -a
- 1 5
- 1 0
-
5
0
5
- 1 5
- 1 0
-
5
0
5
10
FIGURE 3. Measured beamPosition
profiles {mm}
in x at 75 mA: (upper left) scanner 22, µ=1.0, matched,;(upper
right)
scanner 22, µ=1.5
Poaftlon
(mm)
mismatched,;(lower left) scanner 51, µ=1.0 matched,;(lower right) scanner 51, µ=1.5 mismatched.
10
15
15
FIGURE 3. Measured beam profiles in x at 75 mA: (upper left) scanner 22, u=1.0, matched,;(upper right) scanner 22, u=1.5
mismatched,;(lower left) scanner 51, ji=1.0 matched,;(lower right) scanner 51, (1=1.5 mismatched.
45
were
cycle.
were repositioned
repositioned for
for the
the next
next cycle.
were repositioned for the next cycle.
Among
to characterize
characterize the
the beam
beam
Among the
the methods
methods used
used to
Among
the
methods
usedand
to characterize
the
beamat
were:
1)
the
rms
emittance,
2)
the
beam
widths
were: 1) the rms emittance, and 2) the beam widths at
were: 1) the rms emittance,
andpeak
2) the intensity.
beam widths
at
different
Rms
different fractions
fractions of
of the
the peak
intensity. Rms
different
fractions
of
the
peak
intensity.
Rms
emittances
45 were
were calculated
calculated from
from
emittances at
at scanners
scanners 20
20 and
and 45
at scanners
20 andusing
45 were
calculated
from
aaemittances
least-squares
procedure
rms
measurements
procedure using rms measurements
a least-squares
least-squares
procedure
using rms
measurements
from
the
profiles
at
the
four
scanners
in each
each
cluster.
from
the
profiles
at the
the four
four scanners
scanners
in
cluster.
from the profiles at
in
each cluster.
Analysis of
of the
the rms-emittance
rms-emittance data
data for
for comparison
comparison
Analysis
Analysis
of the rms-emittance
data
for in
comparison
with
free-energy
theory
is
now
progress.
with free-energy theory is now in progress.
with
free-energy
theory
is now inmismatches
progress.at
Preliminary
results
for
breathing-mode
Preliminary results for breathing-mode mismatches at
Preliminary
results
for breathing-mode
mismatches
75 mA
mA suggest
suggest
rapid
rate of
of emittance
emittance
growth that
thatatis
is
75
aa rapid
rate
growth
75
mA suggest
a rapid
rate of
emittancetransfer
growth of
thatfree
is
consistent
with
a
large
fractional
consistent with a large fractional transfer of free
consistent
with a energy
large fractional
of free
energy to
to thermal
thermal
within only
onlytransfer
few mismatch
mismatch
energy
energywithin
within
aafew
few
energy
to
thermal
energy
only
a
mismatch
oscillations.
oscillations.
oscillations.
Initial multiparticle
multiparticle simulation
simulation work
work has
has resulted
resulted in
in
Initial
Initial
multiparticle
simulation
workgrowth
has resulted
in
smaller
beam
widths
and
emittance
rates
for
smaller beam
beam widths
widths and
and emittancegrowth
growthrates
ratesfor
for
smaller
the mismatched
mismatched
beams emittance
than are
are experimentally
experimentally
the
beams
than
the
mismatched
beamsthe than
observed.
However,
inputare6D
6Dexperimentally
phase space
space
observed.
However,
the input
input
phase
observed.
However,
the
6D
phase
space
distribution
was
not
measured
in
the
experiment.
distribution was
was not
not measured
measured inin the
the experiment.
experiment.
distribution
Simulations of
of the
the experiment
experiment using
using different
different
possible
Simulations
possible
Simulations
of the experiment
using
different
possible
input
distributions
show
that
the
input
distributions
input distributions
distributions show
show that
that the
the input
input distributions
distributions
input
with more
more extended
extended tails
tails generate
generate
more emittance
emittance
with
more
with
moreGood
extended
tails generate
more
emittance
growth.
agreement
between
experiment
and
growth. Good
Good agreement
agreement between
between experiment
experiment and
and
growth.
simulation
may
require
detailed
knowledge
of
the
simulation may
may require detailed
detailed knowledge
knowledge ofof the
the
simulation
initial transverse
transverserequire
phase-space distributions,
distributions, especially
especially
initial
phase-space
initial
phase-space distributions, especially
for the
thetransverse
tails.
for
tails.
for
the tails.
PRELIMINARY
RESULTS
FOR 75
75 MA
MA
PRELIMINARY
RESULTS FOR
FOR
PRELIMINARY RESULTS
75 MA
Measurements
were
made
at 16,
16, 50,
50, 75,
75, and
and 100
100
Measurements
were made
made at
at
Measurements
were
16, 50,
75, µ.
andIn 100
mA
and
for
a
range
of
mismatch
parameters,
this
mA
for aa range
range of
of mismatch
mismatch parameters,
parameters, |i.
µ. In
In this
this
mA and
andwefor
paper
report
preliminary
results
at
75
mA.
The
paper
report
preliminary results
results at
at 75
75 mA.
mA. The
The
paper we
we transverse
report preliminary
measured
profiles
for the
the matched
matched
beams
measured
transverse
profiles
for
beams
measured
transverse profiles
profiles in
forthe
the linear
matched
beams
have
Gaussian-like
plots
(not
have
Gaussian-like
profiles in
in the
the linear
linear plots
plots
(not
have
Gaussian-like
profiles
(not
shown).
The
semilog
plots
for
the
matched
beams
(see
shown).
The
semilog
plots for
for the
the matched
matched beams
beams (see
shown).
The evidence
semilog plots
Fig.
3)
show
of
an
extended
low-density (see
halo
Fig.
3)
show
evidence
of
an
extended
low-density
halo
Fig. may
3) show
evidenceinofthe
an input
extended
low-density
halo
that
be
present
beam.
The
measured
that
be present
present in
in the
the input
input beam.
beam. The measured
measured
that may
may be
transverse
profiles
for
the
mismatchedThe
beams show
show
transverse
profiles for
for the
the mismatched
mismatched
beams
transverse
profiles
beams
show
(see
Fig.
3)
structure
in
the
form of
of shoulders
shoulders in
in
the
(see
Fig.
3)
structure
in
the
form
the
-3
(see Fig.plots,
3) structure
in the
form of shoulders
in 10
the
semilog
and
some
asymmetric
profiles
at
semilog
plots, and
some asymmetric
asymmetric profiles
profiles at
at 10"
103-3
semilog
plots,
and
some
level.
Figures 44 and
show
the xx and
and yy rms
rms sizes
sizes at
at the
the
level.
and 555 show
show the
the
level. Figures
Figures
4 and
x and
and mismatched
y rms sizes
atcase,
the
different
scanners
for
a
matched
different
for aa matched
matched and
and mismatched
mismatched case,
case,
different scanners
scanners for
respectively.
respectively.
respectively.
SUMMARY
SUMMARY
SUMMARY
Proton linacs
linacs are
are capable
capable of producing
producing highhighProton
Proton
linacs are
capable ofof producing
highenergy,
high-intensity
beams
with
low
emittance.
At
energy, high-intensity
high-intensity beams
beams with
with low
lowemittance.
emittance.At
At
energy,
present,
there
are
two
major
R&D
topics
in
the
proton
present,there
thereare
aretwo
twomajor
majorR&D
R&Dtopics
topicsininthe
theproton
proton
present,
linear accelerator
accelerator field:
field: 1)
1) linac
linac applications
applications of RF
RF SC
SC
linear
linear
accelerator field:
1) linac
applications ofofRF
SC
technology,
and
2)
beam
halo
formation
in
hightechnology, and
and 2)
2) beam
beam halo
halo formation
formation inin highhightechnology,
intensity beams.
beams. A new
new trend
trend during
during the
the past
past decade
decade
intensity
intensity
beams. AA new
trend during
the past
decade
has been
been the
the growing
growing interest
interest in
in SC
SC proton
proton linacs,
linacs,
has
has
been the
growing interest
in SC
proton linacs,
resulting
from
advantages
for
reduced
operating
costs,
resulting from
fromadvantages
advantagesfor
forreduced
reducedoperating
operatingcosts,
costs,
resulting
larger
bore
radius,
greater
operating
flexibility,
and
larger bore
bore radius,
radius, greater
greater operating
operating flexibility,
flexibility, and
and
larger
reduced
capital
costs
as
accelerating
gradients
reduced capital
capital costs
costs asas accelerating
accelerating gradients
gradients
reduced
continuetoto
toincrease.
increase.AA
Abeam
beamhalo
haloexperiment
experimenthas
hasbeen
been
continue
increase.
beam
halo
experiment
has
been
continue
carried
out
at
Los
Alamos,
and
analysis
of
the
data
is
carried out
out atatLos
LosAlamos,
Alamos,and
andanalysis
analysisofofthe
thedata
dataisis
carried
now
in
progress.
Analysis
of
the
rms-emittance
data
now inin progress.
progress. Analysis
Analysis ofofthe
therms-emittance
rms-emittancedata
data
now
for comparison
comparison with
with free-energy
free-energytheory
theoryisis
isnow
nowinin
in
for
comparison
with
free-energy
theory
now
for
progress.
Preliminary
results
for
breathing-mode
progress. Preliminary
Preliminary results
results for
for breathing-mode
breathing-mode
progress.
mismatches atat
at 75
75 mA
mA suggest
suggest aaa rapid
rapid rate
rate ofof
of
mismatches
75
mA
suggest
rapid
rate
mismatches
emittance
growth
that
is
consistent
with
a
large
emittance
growth
that
is
consistent
with
a
large
emittance growth that is consistent with a large
fractional transfer
transfer ofof
of free
free energy
energytoto
tothermal
thermalenergy
energy
fractional
transfer
free
energy
thermal
energy
fractional
withinonly
onlyfew
fewmismatch
mismatchoscillations.
oscillations.
within
only
few
mismatch
oscillations.
within
2.5
2.5
Rmssize(mm)
size(mm)
Rms
2.0
2.0
1.5
1.5
1.0
1.0
0.5
0.5
xrms
xrms
yrms
yrms
0.0
0.0
17
17
17
22
22
22
27
27
27
32
32
37
37
37
Scanner
Scanner
42
42
42
47
47
47
52
52
FIGURE
displacements
at 888 profile
profile scanners
scanners for
for
FIGURE 4.
4. Rms
displacements at
at
profile
scanners
for
Rms displacements
matched
beam
case
(µ=1.0)
at
75
mA.
matched beam case (µ=1.0)
75 mA.
mA.
(|i=1.0) at 75
2.5
2.5
Rmssize
size(mm)
(mm)
Rms
2.0
2.0
ACKNOWLEDGMENTS
ACKNOWLEDGMENTS
ACKNOWLEDGMENTS
1.5
1.5
Thankstoto
toR.
R.Garoby,
Garoby,J.J.
J.M.
M.Lagniel,
Lagniel,R.R.
R.Ferdinand,
Ferdinand,
Thanks
Thanks
R.
Garoby,
M.
Lagniel,
Ferdinand,
I. Masanori,
Masanori,
C.
Pagani,
J.
Wei,
W.
Park,
and
others
I.I.
C.
Pagani,
J.
Wei,
W.
Park,
and
Masanori, C. Pagani, J. Wei, W. Park, andothers
others
who
provided
input
or
help
for
the
high-power
linac
who
provided
input
or
help
for
the
high-power
linac
who provided input or help for the high-power linac
survey presented
presented inin
in Table
Table 1.1.
1. I II wish
wishtoto
tothank
thankIngo
Ingo
survey
survey
presented
Table
wish
thank
Ingo
Hofmann for
for sending
sending usus
us aaa draft
draft ofof
ofhis
hispaper
paperonon
on
Hoftnann
Hofmann
for
sending
draft
his
paper
anisotropyeffects
effectsinin
inmismatched
mismatchedbeams,
beams,which
whichisis
isvery
very
anisotropy
anisotropy
effects
mismatched
beams,
which
very
helpfulfor
forinterpreting
interpretingour
ourexperimental
experimentalresults.
results.I IIalso
also
helpful
helpful
for
interpreting
our
experimental
results.
also
want toto
to acknowledge
acknowledge the
the contributions
contributions ofof
of my
my
want
want
acknowledge
the
contributions
my
colleagues
on
the
beam-halo
experiment
team,
colleagues
colleagues on
on the
the beam-halo
beam-halo experiment
experiment team,
team,
particularlyC.
C.K.
K.Alien,
Allen,K.
K.C.
C.D.
D.Chan,
Chan,P.P.
P.Colestock,
Colestock,
particularly
particularly
C.
K.
Allen,
K.
C.
D.
Chan,
Colestock,
1.0
1.0
I i.o0.5
0.5
xrms
xrms
yrms
yrms
0.0
0.0
17
17
22
22
27
27
32
32
37
37
37
42
42
47
47
52
52
Scanner
Scanner
Scanner
FIGURE
displacements
at 88 profile
profile scanners
scanners for
for
FIGURE 5.
5. Rms
Rms displacements
displacements at
profile
scanners
for
the
mismatch
case (|i=1.5)
(µ=1.5) at
at 75
75mA.
mA.
the breathing
breathing mode mismatch
mismatch case
case
(µ=1.5)
at
75
mA.
46
K. R. Crandall, R. W. Garnett, J. D. Gilpatrick, W.
Lysenko, J. Qiang, J. D. Schneider, M. E. Schulze, R.
Sheffield, and H. V. Smith for the work that was
described in this paper.
REFERENCES
1. J.S.
O'Connell, T.P.Wangler, R.S.Mills,
and
K.R.Crandall, Proc. of 1993 Part. Accel. Conf., IEEE
Catalog No. CH3279-7, 3657-3659.
2. R.L. Gluckstern, Phys. Rev.Lett. 73, 1247 (1994).
3. For an overview, see T.P.Wangler, K.R.Crandall,
R.Ryne, and T.S.Wang, Phys.Rev. ST Accel. Beams I
(084201)1998.
4. P.L.Colestock, et.al, "Measurements of Halo Generation
for a Proton Beam in a FODO Channel," Proc. 2001 Part.
Accel. Conf., IEEE Catalog No. 01CH37268, 170-172.
5. Martin Schulze, et al, "Characterization of the Proton
Beam from the 6.7 MeV LEDA RFQ," Proc. 2001 Part.
Accel., IEEE Catalog No. 01CH37268, 591-593.
6. T.P.Wangler, et al., Experimental Study of Proton-Beam
Halo Induced by Beam Mismatch in LEDA," Proc. 2001
Part. Accel., IEEE Catalog No. 01CH37268, 2923-2925.
7. J.D.Gilpatrick, et al., "Experience with the Low Energy
Demonstration Accelerator (LEDA) Halo Experiment
Beam Instrumentation," Proc. 2001 Part. Accel., IEEE
Catalog No. 01CH37268, 2311-2313.
8. J.D.Gilpatrick, et al., "Beam-Profile Instrumentation for
Beam Halo Experiment: Overall Description and
Operation," Proc. 2001 Part. Accel., IEEE Catalog No.
01CH37268, 525-527.
47