Development
Development of
of High
HighPowered
PoweredTarget
TargetSystems
Systemsfor
forthe
the
Spallation
Neutron
Source
and
the
Muon
Spoliation Neutron Source and the Muon
Collider/Neutrino
Collider/NeutrinoFactory
Factory
T. Gabriel*, J. Haines*, B. Riemer*
T. Gabriel*, J. Haines*, B. Riemer*
P. Spampinato*, T. McManamy*, N. Mokhov#
P. Spampinato , T. McManamy , N. Mokhov
H*
___
H*
ti
*
Spallation Neutron Source, Oak Ridge, TN 37830
* Spallation
Neutron Source,
Oak Ridge,
TN 37830
Fermi
National Accelerator
Laboratory,
Batavia,
IL 60510
#
Fermi National Accelerator Laboratory, Batavia, IL 60510
#
Abstract. The purpose and requirements of the Spallation Neutron Source (SNS) and the target area of the Muon
Abstract. The purpose
of of
thethe
Spallation
Neutron
(SNS)
andtothedesign
targetthese
area facilities
of the Muon
Collider/Neutrino
Factoryand
are requirements
presented. Parts
technologies
that Source
are being
utilized
are
Collider/Neutrino
Factory
aretopresented.
Partsissues
of thethat
technologies
are being
utilized
to design these facilities are
discussed.
Emphasis
is given
the technology
present thethat
greatest
scientific
challenges.
discussed. Emphasis is given to the technology issues that present the greatest scientific challenges.
shipped toto ORNL
ORNL for
for installation];
installation]; BNL,
BNL, the
thehighhighshipped
energy beam
beam transport
transportsystem
systemand
andaccumulator
accumulatorring;
ring;
energy
ORNL, Target
Target Systems
Systems and
and Conventional
ConventionalFacilities;
Facilities;
ORNL,
andANL,
ANL,the
theneutron
neutronscattering
scatteringinstruments.
instruments.
and
SPALLATION NEUTRON
NEUTRON SOURCE
SOURCE
SPALLATION
In
many areas
areas of
of physics,
physics, chemistry,
chemistry, biology,
biology,
In many
materials,
and nuclear
nuclear engineering,
engineering, itit isis extremely
extremely
materials, and
valuable
to have
have aa very
very intense
intense source
source of
of neutrons
neutrons so
so
valuable to
that
structure and
and functionality
functionality of
of materials
materials can
can be
be
that the
the structure
studied. Discussions
Discussions on
on all
all the
the Spallation
Spallation Neutron
Neutron
studied.
Sources
under
consideration
or
development
are
given
Sources under consideration or development are given
in
Refs.
1-3.
One
facility
under
construction
at
ORNL
in Refs. 1−3. One facility under construction at ORNL
for
is the
the Spallation
Spallation Neutron
Neutron Source
Source
for this
this purpose
purpose is
(SNS). This
This facility
facility will
will consist
consist basically
basically of
of three
three
(SNS).
parts: 1)
1) aa high-energy
high-energy (~1
(-1 GeV)
GeV) and
and high-powered
high-powered
(60 Hertz,
Hertz, <1.0
<1.0 µs/pulse,
us/pulse,
((<~< 2 MW) proton accelerator (60
<33 kJ/pulse), 2)
2) aa target/moderator/reflector/
target/moderator/reflector/
[Target Systems
Systems (TS)]
(TS)]
shielding/shutter/utility [Target
assembly, which converts part
part of
of the
the proton
proton beam
beam
power to low-energy ((<~< 2eV)
2eV) neutrons
neutrons through
through
them to
to the
the third
third part,
part, 3)
3) the
the
spallation and delivers them
neutron scattering instruments.
instruments. A
A picture
picture showing
showing the
the
overall facility is given in
in Fig.
Fig. 1.
1. LBNL
LBNL isis responsible
responsible
for the front
currently being
being shipped
shipped to
to
front end, which is currently
ORNL for installation; LANL/JLAB,
LANL/JLAB, the
the linac
linac [parts
[parts
of the Drift
Drift Tube Linac (DTL)
(DTL) and
and klystrons
klystrons have
havebeen
been
AcceleratorComponents
Components
Accelerator
The SNS
SNS isis composed
composed ofof several
several sequential
sequential
The
accelerator
systems
with
a
resultant
proton
energyofof
accelerator systems with a resultant proton energy
-1.0
GeV
delivered
to
the
neutron
production
Hg
~1.0 GeV delivered to the neutron production Hg
target.
target.
Beginningthe
theprocess
processisisaaCesium
Cesiumenhanced
enhancedH-H-ion
ion
Beginning
source,
the
Front
End
(FE)
system.
The
next
source, the Front End (FE) system. The next
accelerator unit
unitisisthe
theRFQ,
RFQ,which
whichaccelerates
acceleratesthe
theH-Haccelerator
beam toto an
an energy
energyofof~2.5
-2.5 MeV.
MeV.The
Thelast
lastsection
sectionofof
beam
theFE
FEsystem
systemisisthe
theMedium
MediumEnergy
EnergyBeam
BeamTransport
Transport
the
(MEBT).InInthe
theMEBT,
MEBT,the
theproper
properbunch
bunchstructure
structureofof
(MEBT).
thebeam
beamisisdeveloped
developedusing
usingbuncher
bunchercavities
cavitiestotomatch
match
the
therotation
rotationfrequency
frequencyofofthe
theaccumulator
accumulatorRing.
Ring.
the
After the
thefront
front end,
end,the
theHH-beam
beamenters
entersthe
thefirst
firstofof
After
four distinct
distinct accelerating
accelerating structures
structureswithin
withinthe
theLinac.
Linac.
four
The
The first
first two
two parts
parts are
areaaDTL
DTLwhich
whichaccelerates
acceleratesthe
the
beam
beamtoto~87
-87MeV
MeVand
andaaCoupled
CoupledCavity
CavityLinac
Linac(CCL)
(CCL)
which
which accelerates
accelerates the
thebeam
beamtoto~187
-187MeV.
MeV.The
Thefinal
final
two
two sections
sections are
are Superconducting
Superconducting Radio
Radio Frequency
Frequency
(SRF)
(SRF) structures
structureswith
withaamechanical
mechanical(relativistic)
(relativistic)beta
beta
of
of0.61
0.61(~325
(-325MeV)
MeV)and
and0.81
0.81(~1.06
(-1.06GeV).
GeV).
At
At the
the injection
injection region
region ofofthe
theRing,
Ring,the
theHH-beam
beam
traverses
traverses thin
thincarbon
carbonfoils
foils that
thatstrip
stripthe
thetwo
twoelectrons
electrons
from
from the
theHH-beam
beamand
andallow
allowthe
theresultant
resultantprotons
protonstotobebe
circulated
circulated and
and stored
stored ininthe
theRing.
Ring.After
After ~1000
-1000 turns
turns
are
areaccumulated
accumulatedininthe
theRing,
Ring,a aseries
seriesofoffast
fastrise-time
rise-time
dipole
dipole elements
elements (kickers)
(kickers)are
aretriggered
triggeredtotoextract
extractthe
the
14 protons circulating in the Ring for
< 2x1014
stored
stored ~< 2xl0 protons circulating in the Ring for
delivery
deliverytotothe
theHg
Hgtarget.
target.
FIGURE
FIGURE 1.
1. SNS
SNS configuration.
configuration.
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
186
MUON COLLIDER/NEUTRINO
MUON COLLIDER/NEUTRINO
FACTORY:
FACTORY:
DEVELOPMENT OF THE TARGET
DEVELOPMENT OF THE TARGET
AREA, REMOTE HANDLING, AND
AREA, REMOTE HANDLING, AND
GRAPHITE TARGET FOR THE µ/ν
ν
GRAPHITE TARGET FOR THE ji/v
Scope and Requirements of Target
Scope and Requirements
of Target
Systems
Systems
The scope of TS is to provide low-energy neutrons
scope of TS
is to provide
low-energy
neutrons
fromThe
high-energy
spallation
reactions
for short-pulsed
from
high-energy
spallation
reactions
for
short-pulsed
neutron scattering instruments and to develop threeneutronbeam
scattering
develop
threeproton
dumps,instruments
one for the and
linactoand
two for
the
proton
beam
dumps,
one
for
the
linac
and
two
for
the
storage ring (injection and extraction).
storage ring (injection and extraction).
The first requirement for TS is to safely and
The receive
first requirement
for in
TSa is
to safely
and
reliably
a proton beam
flowing
mercury
reliably
receive
a
proton
beam
in
a
flowing
mercury
target with the characteristics defined in the
target with the characteristics defined in the
Introduction. As a second requirement, TS must be
Introduction. As a second requirement, TS must be
able to convert part of the proton beam power into
able to convert part of the proton beam power into
short, high-intensity pulses of low-energy neutrons
short, high-intensity pulses of low-energy neutrons
(both ambient and cold) which can be used by up to 24
(both ambient and cold) which can be used by up to 24
neutron beam lines, and which meet the requirements
neutron beam lines, and which meet the requirements
of the neutron scattering instruments.
of the neutron scattering instruments.
Building a TS for the SNS requires the
Building a TS for the SNS requires the
development of a target, in this case a flowingdevelopment of a target, in this case a flowingmercury
mercury target,
target, which
which can
can give
give maximum
maximum neutron
neutron
yield;
a
reflector/moderator
assembly
yield; a reflector/moderator assembly to
to trap,
trap, reflect,
reflect,
and
andthermalize
thermalize(ambient
(ambient and
and cryogenic
cryogenic temperatures)
temperatures)
the
theneutrons;
neutrons;aavessel
vesselsystem
system toto contain
contain the
the reflector/
reflector/
moderator
assembly
and
provide
support
moderator assembly and provide support and
and
alignment
alignment for
for the
the start
start ofof the
the neutron
neutron guides;
guides; bulk
bulk
shielding
shielding and
and shutter
shutter assemblies
assemblies toto shield
shield the
the
personnel
from
the
neutrons
and
to
allow
the
personnel from the neutrons and to allow the closing
closing
ofofthe
thelow
lowenergy
energyneutron
neutronpathways
pathwaysso
sosamples
samples can
can be
be
replaced
in
the
neutron
scattering
instruments;
utilities
replaced in the neutron scattering instruments; utilities
(light
(lightand
andheavy
heavywater,
water,vacuum
vacuumand
and He)
He) toto help
help with
with
the
the cooling
cooling and
and functions
functions of
of the
the various
various systems;
systems;
remote
remotehandling
handlingtotoaccommodate
accommodatethe
thechange
changeout
out of
of the
the
target,
inner
reflector
assembly,
neutron
guides
target, inner reflector assembly, neutron guides and
and
shutters,
shutters,proton
proton beam
beam window,
window, etc.;
etc.; and
and Instruments
Instruments
and
Controls
for
the
majority
of
the
and Controls for the majority of the subsystems
subsystems
mentioned
mentionedabove.
above.Currently,
Currently,the
thedetailed
detailed design
design of
of the
the
TS
is
almost
complete
and
many
procurements
TS is almost complete and many procurements have
have
been
beenplaced.
placed.
The development of a high-intensity source of
Thethat
development
high-intensity
source
of
muons
can be usedofforacollider
experiments
or for
muons
that
can
be
used
for
collider
experiments
or
for
the production of high-energy neutrinos opens the door
the production
of high-energy
opens the
door
for
a broad range
of physicsneutrinos
experiments.
A large
for
a
broad
range
of
physics
experiments.
A
large
effort is underway in this country to develop such a
effort is underway in this country to develop such a
source. The concept is to use a high-intensity proton
source. The concept is to use a high-intensity proton
beam (~24 GeV, ~1MW, ~15 hz) incident on a Hg jet
beam (-24 GeV, ~1MW, -15 hz) incident on a Hg jet
or graphite target to produce pions which decay to give
or graphite target to produce pions which decay to give
the muons. These muons will be magnetically captured
the muons. These muons will be magnetically captured
and then accelerated in a collider ring or in a “race
and then accelerated in a collider ring or in a "race
track” system. The “race track” itself can be pointed at
track" system. The "race track" itself can be pointed at
a detector located many hundred kilometers away. This
a detector located many hundred kilometers away. This
part of the paper describes some of the target remote
part of the paper describes some of the target remote
handling
at such
such aa facility,
facility,
handling needs,
needs, which
which are
are necessary
necessary at
and
also
on
some
of
the
R&D
that
is
underway
on the
the
and also on some of the R&D that is underway on
graphite
target.
graphite target.
Remote
with the
the
Remote Handling
Handling Associated
Associated with
Target
Target Area
Area
Facility
been developed
developed for
for
Facility design
design concepts
concepts have
have been
graphite
and
mercury
target
systems
based
on
the
graphite and mercury target systems based on the
requirements
maintain these
these different
different
requirements to
to operate
operate and
and maintain
targets.
A
picture
of
a
possible
layout
of
the
target
targets. A picture of a possible layout of the target
Target
TargetDevelopment
DevelopmentR&D
R&D
Five
Fiveareas
areashave
havebeen
been defined
defined as
as needing
needing R&D
R&D to
to
develop
a
successful
Target
Systems[4].
These
develop a successful Target Systems [4]. These are
are (1)
(1)
steady-state
steady-statepower
powerhandling,
handling, (2)
(2)remote
remote handling
handling and
and
operation,
operation, (3)
(3) radiation
radiation damage,
damage, (4)
(4) material
material
compatibility,
compatibility,and
and(5)
(5)thermal
thermalshock.
shock. All
All of
of the
the issues
issues
have
havebeen
beenaddressed
addressedoror solved
solved except
except for
for the
the erosion
erosion
through
throughcavitation
cavitation induced
induced pitting
pitting brought
brought on
on by
by the
the
thermal
thermalshock
shockofofthe
thebeam.
beam.After
After testing
testing atat the
the WNR
WNR
inin2001,
2001,pitting
pitting(both
(both large
large and
and small)
small) was
was detected.
detected.
Additional
Additionaltests
testsare
areplanned
plannedinin2002
2002totoassess
assess possible
possible
solutions
solutionsbased
basedon
ongeometry,
geometry,mitigation
mitigation methods,
methods, and
and
materials.
materials.
FIGURE.
decay
FIGURE. 2.
2. Layout
Layout of the target area, decay
channel,
nuclear
shielding,
and
remote
handling
channel, nuclear shielding,
handling
for
for the
the muon/neutrino
muon/neutrino factory.
area,
remote
area, decay
decay channel,
channel, nuclear shielding, and remote
handling
have
handling devices
devices is given in Fig. 2. Both systems have
highly
replaced
highly activated
activated components that must be replaced
periodically
and
periodically using remote handling equipment and
tools.
tools. For
For the
the case
case of aa graphite target, overhead access
was
hot cell
cell was
was
was the
the preferred approach and the hot
located
target,
located above
above the target area. For the mercury target,
overhead
access
overhead access
access combined with below-grade access
187
was necessary in order to maintain the mechanical
components of the system, i.e., pumps, valves, and
mercury storage. A more detailed writeup can be
found in Refs. 5 and 6.
REFERENCES
Graphite Rod Test at the Lansce-WNR
and ORNL
Graphite rods were instrumented with fiber optic
strain gages to measure the dynamic response from the
LANSCE 800 MeV proton beam pulses. The energy
deposition produced by the protons in the graphite is
similar to that anticipated at a Mu/Nu facility.
Structural analysis simulations of the response were
performed with the finite element code, ABAQUS/
Explicit.[7] The predicted and measured strains at the
mid length location compare favorably.
Sublimation of the radiatively cooled graphite
target is a limiting feature of the target's lifetime.
Tests have been carried out in a vacuum environment
to determine the useful lifetime at about 2000QC. The
data, which is in reasonable agreement with theoretical
data, indicates that the lifetime is short, but acceptable.
This experiment is described in detail in Ref. 8. Tests
are also underway to determine the lifetime in a 1 atm
He environment, which should increase the lifetime.
Neutronics and Shielding
Substantial analysis based on the MARS code [9]
simulations have been carried out [10] which includes
pi/mu production and collection, energy deposition
and residual dose levels, shielding and component
lifetimes. The optimized system would provide 0.37
captured muons per proton at 36 meters from the tilted
mercury jet impacted by 24-GeV protons. If a graphite
target had been used, this number would be reduced by
about a factor of two. Peak energy deposition and
dynamic heat loads in the superconducting coils of a
20-T hybrid solenoid are kept below the tolerable
limits via carefully designed shielding made of watercooled tungsten-carbide balls. With the current setup,
the anticipated lifetime of main components exceeds
15 years. The inner shielding is very radioactive, with
residual dose rate up to 1 kSv/hr. This will require
remote control and robotics for the inner parts of the
system. This dose drops by two orders of magnitude
after several weeks. The residual dose outside the
cryostat is significantly lower, of the order of 100
mSv/hr.
1.
K. N. Clausen, "The European Spoliation Source (ESS)
Project," ICANS-XV 15th Meeting of the International
Collaboration on Advanced Neutron Sources,
Proceedings-Volume 1, November 6-9, 2000, Tsukuba,
Japan.
2.
Y. Oyama, S. Ikeda, and JAERI-KEK Joint Project
Team, "Status of Spallation Neutron Source Program in
High Intensity Proton Accelerator Project," ICANS-XV
15th Meeting of the International Collaboration on
Advanced Neutron Sources, Proceedings—Volume 1,
Nov. 6-9, 2000, Tsukuba, Japan.
3.
T. E. Mason, T. A. Gabriel, R. K. Crawford, K. W.
Herwig, F. Klose, and J. F. Ankner, "The Spallation
Neutron Source: A powerful tool for materials
research," 20th International Linac Conference, August
21-25, 2000, Monterey, California, published on the
LANL e-print server.
4.
T. A. Gabriel, "An Overview of the SNS," published in
the proceedings of the "Golden Anniversary" of
Nuclear Engineering at North Carolina State, Raleigh,
NC, Dec. 2-4, 2000.
5.
P. T. Spampinato, J. B. Chesser, D. L. Conner, T. A.
Gabriel, F. X. Gallmeier, J. R. Haines, and T. J.
McManamy, "Support Facility for a Graphite Target
Neutrino Factory," ORNL/TM-2000/153 (August
2000).
6.
P. T. Spampinato, J. B. Chesser, D. L. Conner, T. A.
Gabriel, F. X. Gallmeier, J. R. Haines, and T. J.
McManamy, "Support Facility for a Mercury-Jet Target
Neutrino Factory," ORNL/TM -2001/124 (September
2001).
7.
ABAQUS Finite Element Analysis Software, Hibbitt,
Karlsson & Sorensen, Inc., Pawtucket, RL
8.
J. R. Haines and C. C. Tsai, "Graphite Sublimation
Tests for the Muon Collider/Neutrino Factory Target
Development Program," ORNL/TM-2002/27.
9.
N. V. Mokhov, "The MARS Code System User's
Guide," Fermilab-FN-628 (1995); N.V. Mokhov, O.E.
Krivosheev, "MARS Code Status," Fermilab-Conf00/181 (2000).
10. N. V. Mokhov, "Particle Production and Radiation
Environment at a Neutrino Factory Target Station,"
Proc. 2001 Part. Accel. Conf., Chicago, p. 745 (2001);
Fermilab-Conf-01/134 (2001).
188