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Serena barbanotti INFN milano
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Transcript of Serena barbanotti INFN milano
Carlo PaganiUniversity of Milano and INFN Milano-LASA
High Power Accelerators for Very Intense Neutron Sources
International Workshop on Accelerator based Neutron Sources for Medical, Industrial and
Scientific Applications
Turin, Environment Park, 23rd May 2008
Presented by: Serena Barbanotti - INFN Milano-LASA
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 2
Index
Introduction: why accelerators as source for neutrons?– General principles of neutron production with accelerators
What is a high power accelerator and how does it work?– General layout– Superconductive choice
Applications of accelerator driven neutron sources– Waste Transmutation (ADS)– Materials studies (SNS)– Fusion (IFMIF)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 3
Why Accelerators
Easily pulsed beams
No chain reactions
Very high typical fluxes–A 1 mA beam delivers to the target 6·1015 particles per
second
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 4
Accelerators and Neutrons
The accelerator
A particle accelerator is delivering energy to the beam via a rotational electric field acting on the charged particles.
Depending on the reaction chosen for neutron production, either proton or deutons are accelerated (high intensity simple particles with maximum charge to mass ratio).
Superconducting accelerators are preferred for their higher efficiency in the power conversion from plug to beam.
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 5
Accelerators and Neutrons
The neutron source
High intensity charged particle beams are used to produce high intensity neutron fluxes for several applications
The neutron flux is determined by the charged particle flux through a simple nuclear process on a beam target (spallation or stripping reaction)
Different materials are chosen and different particles are accelerated, depending on power density, application, …
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 6
Accelerators and Neutrons
Beam target choice
High Z materials for spallation → high efficiency neutron conversion
Liquid or solid, depending on power density– for good neutron economy is required to minimize target dimension– very high power density on target– liquid target are preferred (heat removal by convection)– solid target have power limit
Beam – liquid target interface: window or windowless ?
Window related problems:– window cooling– cyclic thermal loading on the window under creep condition– very corrosive environment (using lead)– radiation damage induced by proton and neutron in the window
material
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 7
Neutron generation 1/3
Spallation reaction
– An heavy metal target hit by a high energy proton generates neutrons
• proton ~1 GeV → 20 - 30 neutrons
Characteristics:
• High conversion factor neutrons/protons• Wide neutron energy spectrum• For high neutron production efficiency, required high energy
proton beam
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 8
Neutron generation 2/3
Stripping reaction
– An incident deuton hits a Lithium target nucleus; the target emits a neutrons and the deuton proceeds with most of its original momentum in almost its original direction
– Typical reactions:7Li(d,2n)7Be 6Li(d,n)7Be 6Li(n,T)4He
Characteristics:
• Lower conversion factor• Peaked neutron energy spectrum: 14 MeV• Required low energy beam
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 9
Spallation reaction
ADS
SNS
Proton beam
Neutron generation 3/3
Stripping reactionIFMIF
Proton beam
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 10
Applications 1/3
Nuclear fusion (IFMIF)
Fusion reactors will produce high neutron fluxes at 14 MeV
This will bring to high material irradiation
To guarantee reactor operation, required materials with:
– ITER: 3 dpa/lifetime
– DEMO: > 20 dpa/year
Required a material test facility for material verifications
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 11
Applications 2/3
Nuclear Waste Trasmutation (ADS)
Problem: Disposal of Nuclear Waste
– Reduce radiotoxicity of the waste
– Minimize volume/heat load of waste
Strategy: Partitioning and Transmutation
– Separate chemically the waste (Pu, MA, LLFF)
– Use the waste as fuel in dedicated transmuter systems
Solution: a transmuter has 2 ingredients
– A subcritical reactor (k<1), with U-free fuel: chain reaction is not self-sustained
– An intense spallation source (high p flux on liquid lead target) : provides “missing” neutrons to keep the reaction going, with a broad energy spectrum (good for MA burning)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 12
Application 3/3
Material science (SNS)
Neutrons provide unique insight into materials at the atomic level:
– ‘see’ light atoms in biomaterials and polymers
– study magnetic properties and atomic motion
– measure stress in engineering components
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 13
The accelerators
ADS SNS IFMIF
Accelerates protons H-, converted in p at accumulator ring
deutons
Neutron production
Spallation on liquid lead/bismuth
Spallation on liquid mercury
Strippingdeuton - Litium
Target area Windowless With window With window
Neutron energy Wide spectrum Wide spectrum 14 MeV
Beam dimension ~ dm2 ~ dm2 ~ dm2
Beam energy ~ 600-1000 MeV ~ 1 GeV ~ 40 MeV
Average beam current
20-40 mA 1.4 mA 2 * 125 mA
Total beam power ~ 20 MW 1.4 MW 10 MW
Beam operation Continuous Pulsed: 60 Hz – 695 ns Continuous
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 14
Index
Introduction: why accelerators as source for neutrons?– General principles of neutron production with accelerators
What is a high power accelerator and how does it work?– General layout– Superconductive choice
Applications of accelerator driven neutron sources– Waste Transmutation (ADS)– Materials studies (SNS)– Fusion (IFMIF)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 15
Particle Accelerators
The name Particle Accelerator is a historical one connected to the concept of an energy increase related to a velocity change, that is an acceleration.
For protons and ions that has been the case for a while:
– Electrostatic accelerators
– Linacs
– Cyclotrons
Synchrotron concept and strong focusing scheme pushed energies to e level where the Energy increase is dominated by the particle mass increase and the velocity is very close to the speed of light.
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Basic Concepts: Fields
Equation of motion and Lorentz force– Electric field can transfer energy to the particles
– Magnetic field can guide the beam in a stable path
All Particle Accelerators are based on these rules– The beam moves inside a vacuum chamber– Electromagnetic objects placed on the beam path perform the tasks:
• Magnets guide the beam on the chosen trajectory (dipoles) and provide focusing (quadrupoles)
• Resonant RF cavities (exceptions: Betatron, RFQ and Electrostatic Accelerators) are used to apply the electric accelerating field
magelLorentzem FFBvEqdt
pdFF
)(
dtvEqsdFTE em FieldElectricE
EnergyCineticT
GainEnergyE
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Some Milestones for Accelerators
20th centuryfirst 25 years
from 1928to 1932
1928
1929
1944
1946
1950
1951
1956
1970
early 80's
the last years
Prehistory: fundamental discoveries made with "beams" from radioactive source trigger the demand for higher energies
Cockcroft&Walton develop a 700kV electrostatic accelerator based on a voltage multiplier
First Linac by Wideroe based on resonant acceleration
Lawrence invents the cyclotron
MacMillan, Oliphant & Veksler develop the synchrotron
Alvarez builts a proton linac with Alvarez structures (2 mode)
Christofilos patents the concept of strong focusing
Alvarez conceives the tandem
Kerst stresses in a paper the concept of a collider
Kapchinski & Telyakov invent the radio-frequency quadrupole RFQ
superconducting magnets for cylotrons and synchrotrons considerably boost the performance (energy for size)
the development of superconducting accelerating cavities provides very high power conversion efficiency
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 18
Accelerators evolution: the Livingston chart
Around 1950, Livingston made a quite remarkable observation:
Plotting the energy of an accelerator as a function of its year of construction, on a semi-log scale, the energy gain has a linear dependence.
50 years later, that still holds true.
In other words, so far, builders of accelerators have managed exponential growth, every ten years, roughly a factor of 33 is won.
Note that for a given "family" of accelerators, saturation of maximum energy sets in after some time.
future
E = m c2
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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An RF source generates an electric field in a region of a resonant metallic structure; the particles of the beam need to be localized in bunches and properly phased with respect to the field so that the beam is “accelerated”
Two possible designs:– NC Travelling wave structures– SC Standing wave cavities
Linac RF acceleration concept
mode
Traveling waveVph ≈ c and Vg < c
Standing waveVph = 0 and Vg = c
bunches Electric field
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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RF Linac Overview
Particle Source
Linac structure:
Acceleration (cavities)Transverse focusing (magnets)
Electric power
Vacuum
Cooling
RF powerand controls
Output beam (experiments, users,
applications ...)
Subsystems
SNS - ORNL
TTF - DESY
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Energy gain and dissipated power
To accelerate particles efficiently, very high electric field is required
In any structure (cavity) holding an electromagnetic field, both dissipated power and stored energy scale quadratically with the fields
The efficiency of a cavity depends from:
Its quality factor, Q
driven by the surface resistance, Rs
Its shunt impedance, rfunction of the cavity geometry
and of the surface resistance, Rs
For efficient acceleration Q, r and r/Q must all be as high as possible
dtvEqsdFTE Lor
dissP
UQ
dissP
Vr
2
U is the energy stored in the cavity
Pdiss is the power dissipated on its surface
ΔV is the voltage seen by the beam
U
V
Q
r
2 “r over Q” is purely
a geometrical factor
Good material for maximum Q and r (that is minimum Pdiss)
Good design for maximum r/Q
L R C
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Why Superconductivity in RF linacs?
In normal conducting linac a huge amount of power is deposited in the copper structure, in the form of heat, that needs to be removed by water cooling (in order not to melt the structures)
– Dissipated power can be much higher than the power transferred into the beam for acceleration
Superconductivity, at the expenses of higher complexity, drastically reduces the dissipated power and the cavities transfer more efficiently the RF power to the beam
In short:– NC linac: lower capital cost, but high operational cost– SC linac: slightly higher capital cost, but low operational cost
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 23
Superconductivity whenever possible
For a good but not perfect conductor (ρ ≠ 0), the fields and currents penetrate into the conductor in a small layer at the cavity surface (the skin depth, δ)
With RF fields, a SC cavity dissipate power, not all electrons are in Cooper pairs.
In NC linac a huge amount of power is deposited in the copper structure: MW to have MV
– Pulsed operation and Low Duty Cycle
SCSuperConducting
NC or RTNormalConducting
0
sR
S
sdiss dSH
RP 2
2
K
664.17exp
K
GHz109n
24
TT
fRs
GHz8.7m 2
1
fRs
Nb
Cu
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
0 500 1000 1500 2000 2500 3000
f [MHz]
Rat
io b
etw
een
Nb
an
d C
u R
s
2 K4.2 K
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Superconductivity whenever possible
Superconductivity, drastically reduces the dissipated power. But some drawbacks
– Higher complexity: refrigeration and cryomodules• Carnot and refrigeration plant efficiencies
– Higher technology: cavity treatments– Simpler geometries: lower shunt impedance
And two big advantages:– Large bore radius: less beam losses– CW or high duty cicle preferred
K2,K300for150/1
K2.4,K300for70/1
21
21
21
2
TT
TT
TT
TC
K2at1WforK300atW800
K2.4at1WforK300atW250
T
TthCtot
K2at%2015
K2.4at%3025
T
Tth
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Index
Introduction: why accelerators as source for neutrons?– General principles of neutron production with accelerators
What is a high power accelerator and how does it work?– General layout– Superconductive choice
Applications of accelerator driven neutron sources– Waste Transmutation (ADS)– Materials studies (SNS)– Fusion (IFMIF)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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ADS proton beam requirements
Very high duty cycle, possibly CW
Energy of the order of 1 GeV, determined by– neutron production rate per GeV
and per proton(optimum value reached at ~1 GeV)
– energy dissipated in the input window(rapidly decreasing with energy, when E<few GeV)
beam power from several MW up to tensof MW
– few MW for a “demo” plant of ~100 MWth– ~20 MW for an industrial burner of ~1500 MWth
Very few beam trips per year accepted if longer then 1 second
No limitation for very short beam trips: << 1 second
0
10
20
30
40
50
0 0.5 1 1.5 2 2.5
yiel
d / E
p (n
eutro
ns/G
eV)
proton energy, E_p (GeV)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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The proton linacs
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Linac or cyclotron 1/2
Most powerful CW proton accelerators (MW-size facilities)
Linacs– LAMPF/LANSCE (~1970)
• 800 MeV• 1 mA H+ average current • Peak H+ current 16.5 mA @ 100 Hz and 625 s pulse length• NC accelerator
Cyclotrons– PSI – separated sector (1974)
• Original design was for 100 A• From 72 to 590 MeV• ~2 mA average current• Beam losses at extraction < 1 A
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 29
Linac or cyclotron 2/2
Cyclotron
No remarkable R&D programs
Its cost scales quadratically with the output energy
Very high reliability and availability at PSI, but further improvement looks very difficult
Not applicables concepts of redundancy and spare on line
Linear Accelerator
A worldwide R&D effort is in progress
High potentiality of these machines has been proven:– Sources, RFQs and SRF technology successfully operated
cost per MeV is decreasing with energy
Linac (except front end) has intrinsic modularity:– Easy redundant and “spares on line” design
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 30
The ADS Linac
Linac benefits of impressive progresses in the field of SC cavities:
– SC technology can be extended to proton linac down to ~ 0.5
Intrinsic modularity simplify reliability issues
– Redundant design strategy based on the “spare-on-line” concept
– Strong focusing and large beam aperture produce negligible losses
The scheme generally considered consists of four different sections
– The proton source: proton energy 80-100 keV– The Radio Frequency Quadrupole (RFQ): up to 5 MeV– A medium energy section, either NC or SC: up to 100 MeV– A high energy section made of SC elliptical rf cavities: up to final
energy 1 GeV (most of the linac is here!)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 31
Reference Linac Design
Source RFQ ISCL High Energy SC Linac
Microw
ave RF
Source
High current (35 m
A)
80 keV
High transm
ission 90%
30 mA
, 5 MeV
(352 M
Hz)
5 - 85/100 MeV SC linac
Spoke cavities (352 MHz)
Lambda/4 cavities (176 MHz)
Reentrant cavities (352 MHz)
or
NC Drift Tube Linac (DTL)
3 section linac:
– 85/100 - 200 MeV, =0.47
– 200 - 500 MeV, =0.65
– 500 – 1000/2000 MeV, =0.85Five(six) cell elliptical cavities
Quadrupole doublet focussing: multi-cavity cryostats between doublets
– 704.4 MHz
Proton Source
RFQ Medium energy ISCL linac 3 sections high energy SC linac
80 keV 5 MeV ~100 MeV 200 MeV 500 MeV >1000 MeV
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 32
Linac Design
Accelerator design performed in the EU PDS-XADS program (5° FWP)– Choice of superconducting linac– Modular: same concept for Prototype and Industrial scale
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 33
Injector, an example: LEDA at LANL
LEDA RFQ:
Beam current 100 mA (95 %)
Final Energy 6.7 MeV
Length 8 m (4 sections)
RF Power670 kW (beam)
1.2 MW (structure)
RFQ Concept
One Section of LEDA-RFQ
The LEDA-RFQ fully installed
magelLorentz FF)BvE(qdtpd
F
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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High energy section: the test module
Elliptical =0.47 cavities have been produced, vertically tested and will be equipped to be tested in an horizontal test module by INFN - LASA
0 2 4 6 8 10 12 14 16 18 20109
1010
start of electron emission
Q0
Eacc
[MV/m]
Z501 Test #1 Z502
Eacc
=8.5 MV/m @ Q0=1010
multipacting barriers
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 35
The Reliability Issue
The small number (few per year) of beam trips allowed during the accelerator operation, requires a detailed analysis of the accelerator availability and reliability, much deeper that in the past applications
The reliability analysis of a complex system is an iterative process, which starts from a preliminary design of the whole system and its components and is followed by the development of the Reliability Block Diagram (RBD).
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 36
Some Remarks on Linac Reliability
In order to meet the # of stops > 1 s– The beam startup procedure for a multi MW beam will be certainly > 1 s
operation with faulty components needs to be achieved • Linac must tolerate single failures of most of components• Procedures for “adjusting” beam transport and repairing of components
without interrupting the beam while marinating acceptable lossesAs a consequence– Components and subsystems divided in two major categories if they lead to:
• Failures requiring a beam stop• Failures that can be repaired while the beam is on, or later…
As general rules– Components falling in the first category should have the highest reliability
• Typically passive components overdesigned and overtested – Components falling in the second category should have the highest
accessibility for repairing or substitutionFor example, this suggest the choice of a double tunnel design, with most of ancillaries situated in a free-access tunnel (Power supplies, RF generators, etc.)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 37
Index
Introduction: why accelerators as source for neutrons?– General principles of neutron production with accelerators
What is a high power accelerator and how does it work?– General layout– Superconductive choice
Applications of accelerator driven neutron sources– Waste Transmutation (ADS)– Materials studies (SNS)– Fusion (IFMIF)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 38
SNS Guiding Principles
SNS will provide high availability, high reliability operation of the world’s most powerful pulsed neutron source
Research conducted at SNS will be at the forefront of biology, chemistry, physics, materials science and engineering
– SNS will be able to provide cold neutrons (useful for research on polymers and proteins)
SNS expects 1000-2000 users per year from academia, government, and industry
Flexible instrument strategy that supports both general user access and dedicated access for expert instrument teams that contribute to construction and operation of instruments
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 39
The Spallation Neutron Source
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Neutron generation
H- ions are produced in the front end ion source
H- are accelerated to ~1GeV in Linac (NC and SC)
On injection into ring 2x e- are stripped to form p
Protons are accumulated and compressed into a 1 µs pulse width in the ring (~120 turns of the ring, p are traveling at ~0.9c)
A kicker magnet knocks the proton pulse out of the ring orbit into the beamline that takes the p’s to the Hg target
Beam losses need to be preserved below 1 W/m along the whole machine and beamlines to limit activation
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Power Ramp-up Progress
“We are starting to get to real beam power levels”
160 KW: ISIS Power Record
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Beam Target and Neutron Moderation
Spallation target
Mercury was chosen for the target for several reasons
– it is not damaged by radiation, as are solids
– it has a high atomic number, making it a source of numerous neutrons (the average mercury nucleus has 120 neutrons and 80 protons)
– because it is liquid at room temperature, it is better able than a solid target to dissipate the large, rapid rise in temperature and withstand the shock effects arising from the rapid high-energy pulses
Neutron moderation
The neutrons coming out of the target must be turned into low-energy neutrons suitable for research
– moderated to room temperature or colder passing them through cells filled with water (to produce room-temperature neutrons) or through containers of liquid hydrogen at a temperature of 20 K (to produce cold neutrons)
– The moderators are located above and below the target
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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805 MHz, 0.55 MW klystron
805 MHz, 5 MW klystron
402.5 MHz, 2.5 MW klystron
Layout of RF Linac
SRF, ß=0.61, 33 cavities
1
from CCL
186 MeV
86.8 MeV2.5 MeV
RFQ
(1)
DTL
(6)
CCL
(4)
SRF, ß=0.81, 48 cavities
1000 MeV
(81 total powered)
379 MeV
Warm Linac
SCL Linac
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Normal Conducting Linac
CCL Systems designed and built by Los Alamos
805 MHz CCL accelerates beam to 186 MeV
System consists of 48 accelerating segments, 48 quadrupoles, 32 steering magnets and diagnostics
402.5 MHz DTL was designed and built by Los Alamos
Six tanks accelerate beam to 87 MeV
System includes 210 drift tubes, transverse focusing via PM quads, 24 dipole correctors, and associated beam diagnostics
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Superconducting Linac
Designed an built by Jefferson Laboratory
SCL accelerates beam from 186 to 1000 MeV
SCL consists of 81 cavities in 23 cryomodules
Two cavities geometries are used to cover broad range in particle velocities
Cavities are operated at 2.1 K with He supplied by Cryogenic Plant
Medium beta cavity High beta cavity
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Others SNS Parameters
Protons per pulse on target 1.5x1014 protons
Energy per pulse on target 24 kJ
Average linac macropulse H- current 26 mA
Linac beam macropulse duty factor 6%
Front end length 7.5 m
Linac length 331 m
HEBT length 170 m
Ring circumference 248 m
RTBT length 150 m
Ion type (Ring, RTBT, Target) proton
Ring filling time 1.0 ms
Ring revolution frequency 1.058 MHz
Number of injected turns 1060
Ring filling fraction 68%
Ring extraction beam gap 250 ns
Maximum uncontrolled beam loss 1 W/m
Number of ambient / cold moderators 1/3
Number of neutron beam shutters 18
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 47
SNS Instruments
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 49
SNS Reflectometers
Rmin< 5×10-10
Qmax ~ 1.5 Å-1 (Liquids)
~ 7 Å-1 (Magnetism)dmin~ 7 Å50-100× NIST NG-1
Magnetism: vertical sample
Liquids:horizontal sample
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 50
Diffraction
• Highest flux a short wavelengths is crucial for studies of local disorder in complex materials
• Nanoscale Ordered Materials Diffractometer (NOMAD)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 51
High Pressure Cells Limit Sample Volume
• Pressure cell of the type to be employed on SNAP (Spallation Neutrons and Pressure) beamline
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 52
Index
Introduction: why accelerators as source for neutrons?– General principles of neutron production with accelerators
What is a high power accelerator and how does it work?– General layout– Superconductive choice
Applications of accelerator driven neutron sources– Waste Transmutation (ADS)– Materials studies (SNS)– Fusion (IFMIF)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 53
IFMIF general information
IFMIFIrradiation tool to qualify advanced materials resistant to extreme radiation conditions (DEMO reactor)
Requires an intense neutron flux (~1017 n/s/m2) at 14 MeV
Neutrons are generated by stripping deutons on Li target. Deuton provided by accelerator: 2 parallel CW beams 40 MeV, 125 mA for a total power of 10 MW
IFMIF-EVEDA (Engineering Validation Engineering Design Activities)Engineering design of the IFMIF facility, safety assessment for a generic site and preparation of the technical specifications for the longest delivery components
Design and construction of low energy section of the first accelerator
Design, construction and tests of a scale 1:3 model of the Target Facility
Design, construction and tests of mock-ups of the Test Facility (high flux volume and medium flux volume). Irradiation of the test set-up to relevant irradiation dose values to check performance under real operating conditions
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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ITER
3 dpa/lifetime
DEMO
30 dpa/year
IFMIFIFMIF
20-55 dpa/year
Advanced Materials are at a critical path
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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neutron flux
coolant flow (He)
200
50
50
[mm]
IFMIF Main Objectives
Neutron flux: 10 MW deuton beam power on the test module is equivalent to
– 1 MW/m2 neutron beam– 4.5 1017 n/m2/s– 3 10-7 dpa/s for Fe
Neutron spectrum: fit to probable DEMO first wall
Neutron fluence accumulation:DEMO relevant (150 dpa/few years)
Neutron flux gradient: about 10 % in volume
Machine availability: 70 % (quasi continuous operation)
Good accessibility of irradiation volume for experimentation and instrumentation
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 56
Accelerator (x 2) Test Cell
IFMIF Principles
Low flux (< 1 dpa/an, > 8 L)
Medium flux (20 – 1 dpa/an, 6 L)
RFQ HWR HEBT
Typical reactions– 7Li(d,2n)7Be– 6Li(d,n)7Be– 6Li(n,T)4He
Source
Lithium target
High flux (> 20 dpa/an, 0.5 L)
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 57
IFMIF “Artist View”
Ion Source
RF Quadrupole
Post Irradiation ExperimentFacilities
High Energy Beam Transport
Li Target
Li Loop
Test Modules insideTest Cells
Half-wave resonators
0 20 40 m
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 58
IFMIF Accelerator
A high intensity ion source, delivers a beam of deutons of 140 mA to 100 keV
A RFQ (Radio Frequency Quadrupole) cavity put « in packages » and accelerate the deutons until a 5 MeV energy
Elements of linear accelerator to reach the final energy (10 MeV at EVEDA, 40 MeV at IFMIF)
A transport line up to the beam stop of 1,2 MW for EVEDA phase and up to the liquid lithium target of 10 MW for IFMIF
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 59
~ ~
Accelerator Prototype (scale 1:1)
Ion Source
RadioFrequency Quadrupole
Matching Section
Half Wave Resonators linac
HEBT and Beam Dump
Building (at Rokkasho)for the test of the accelerator
Lithium Loop (scale 1:3)
Diagnostics
Erosion/Corrosion
Purification system
Remote Handling
High Flux Test Module (HFTM)
Irradiation in fission reactor
Validation of sample concepts
IFMIF EVEDA design
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 60
Accelerator Reference Design
High Energy Beam Transport (HEBT)Large Bore Quad & Dipoles, 43 m long
SC Half-wave resonatorsacceleration to 40 MeV
Radio Frequency Quadrupole (RFQ)bunching & acceleration 5 MeV; MS to DTL
RF Power System 175 MHz12 RF amplifiers, 1MW CW
100 keV
Injector Ion Source 140 mA D+, 100 keVLEBT transfer/match to RFQ
5 MeV
40 MeV
125 mA deuton beam
Control Command
22
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 61
Injector - Conception
Specifications
rms emittance = 0.25 .mm.mrad (normalized )
beam current = 140 mA
energy = 100 keV
The injector components
the ECR (Electron Cyclotron Resonance) ion source must deliver 140 mA beam current with an output energy of 100 keV
the LEBT (Low Energy Beam Transport) section includes– magnetic lenses (focusing and beam matching to the RFQ)– beam instrumentation : charge, current, profile, size, emittance
measurement
the associated infrastructure: power supplies, control system, water cooling
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 62
Injector – Initial LEBT design
Cone Cameras ACCT
Cameras
Neutron detector
Emittance Monitor
DC toroid on HV cable
Movable ConFlatSpecies identification*
Thermocouples*fluorescence + shifted Doppler lines analysis
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 63
Radio-Frequency Quadrupole
• RFQ Length 9.6 meters
• RFQ transmission OK 99% (w/o error)
• Losses above 1 MeV kept at low level 0.01 %
• Voltage and Power levels moderate
< V > = 102 kV, P = 1200 1480 kW
RF study started
Cu brazing joints
e-beam & laser welding alternatives under study
Mechanical design in a test phase
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 64
Old design: DTL and Matching Section
RF Frequency 175 MHz
Input energy 5.02 MeV
Output energy 9.02 MeV
Internal length 4.67 m
Internal diameter 1.074 m
Number of cells 33
Total power 680 kW
Power dissipation 180 kW
Efficiency 73.5 %
1st
tank
par
amet
ersConventional Alvarez technology
1 RF coupler / tank
Power coupler
Stem-box Cover
Tuning Slug
Post Coupler
Drift Tube Stem
Drift Tube
To vacuum pump
Bulk Tuner
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 65
Present design: Half-wave resonators (HWR)
IFMIF/EVEDA Project Committee meeting (10-11 October 2007)Accelerator Facility Project Plan65
Superconducting solution: existing modules
SARAF* project SC IFMIF
Take 175 MHz HWR with big aperture 30 mm 40-50 mm
and conservative gradients 5.5 MV/m 4.5 MV/m
group cavities in long cryostats 6 8-10-12
module double of the onecurrently operating at SOREQ
L~ 5 m
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 66
Lithium target
Engineering design of the target system includes thermal, thermo-structural and thermo-hydraulic analyses of the target assembly, backplate, Li components, Li loop and purification system
Quench Tank
Deuteron BeamsLi Target(T2.5 cm, W26 cm)
EM Pump
HX(Li / Organic Oil)
Dump Tank(9 m3-Li)
HX(Organic Oil / Water)
130 L/s, 250 C
Cold Trap(220 C)
N Hot Trap(600 C)
T Hot Trap(250 C)
The Lithium circuitThe Lithium target
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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2 m
D+
Medium FluxTest Modules
High FluxTest Module Low Flux
IrradiationTubes
LithiumTarget
Lithium Tank
Shield plug
Principle of Test Modules
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
Carlo Pagani & Serena Barbanotti 68
Upper internal flangeUpper reflectorLateral reflector12 rigs
Lower reflector
Helium inlet duct
Helium exit duct
HFTM VIT
MF-CF
MF-LBVMF-TR
Irradiation modules overview
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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IFMIF Medium Flux Test Module
3 independentsamples
in creep fatigue
Int. Workshop on Accelerator Based Neutron Sources
Turin, 23 May 2008
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Conclusions
Present and future large facilities are based to a large extent on the superconducting RF linac technology that has been pioneered for the High Energy Physics machines in the last decades
– LEP at CERN (e+e- collider with SRF cavities)– CEBAF at TJNAF (recirculated SRF linac)– TESLA and ILC (next generation linear colliders proposed for
precision physics in the Higgs sector after LHC discovery)
SNS moved from NC design to SC after project approval and during construction
Future facilities rely on SC linacs at even lower energies to benefit from SC technology