Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron p...
Why Accelerators <ul><li>Easily pulsed beams </li></ul><ul><li>No chain reactions </li></ul><ul><li>Very high typical flux...
Accelerators and Neutrons <ul><li>The accelerator </li></ul><ul><li>A particle accelerator is delivering energy to the bea...
Accelerators and Neutrons <ul><li>The neutron source </li></ul><ul><li>High intensity charged particle beams are used to p...
Accelerators and Neutrons <ul><li>Beam target choice </li></ul><ul><li>High Z materials for spallation -> high efficiency ...
Neutron generation 1/3 <ul><li>Spallation reaction </li></ul><ul><ul><li>An heavy metal target hit by a high energy proton...
Neutron generation 2/3 <ul><li>Stripping reaction </li></ul><ul><ul><li>An incident deuton hits a Lithium target nucleus; ...
<ul><li>Spallation reaction </li></ul><ul><li>ADS </li></ul><ul><li>  SNS </li></ul>Neutron generation 3/3 <ul><li>Strippi...
Applications 1/3 <ul><li>Nuclear fusion (IFMIF) </li></ul><ul><li>Fusion reactors will produce high neutron fluxes at 14 M...
Applications 2/3 <ul><li>Nuclear Waste Trasmutation (ADS) </li></ul><ul><li>Problem: Disposal of Nuclear Waste </li></ul><...
Application 3/3 <ul><li>Material science (SNS) </li></ul><ul><li>Neutrons provide unique insight into materials at the ato...
The accelerators ~ dm 2 ~ dm 2 ~ dm 2 Beam dimension 14 MeV Wide spectrum Wide spectrum Neutron energy 10 MW 1.4 MW ~ 20 M...
Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron p...
Particle Accelerators <ul><li>The name Particle Accelerator is a historical one  connected to the concept of an energy inc...
Basic Concepts: Fields <ul><li>Equation of motion and Lorentz force </li></ul><ul><ul><li>Electric field  can transfer ene...
Some Milestones for Accelerators  <ul><li>20th century first 25 years </li></ul><ul><li>from 1928 to 1932 </li></ul><ul><l...
Accelerators evolution: the Livingston chart  <ul><li>Around 1950,  Livingston  made a  quite   remarkable observation : P...
<ul><li>An  RF source  generates an  electric field  in a region of a resonant metallic structure; the  particles  of the ...
RF Linac Overview Particle Source Linac structure : Acceleration (cavities) Transverse focusing (magnets) Electric power V...
Energy gain and dissipated power <ul><li>To accelerate particles efficiently,   very high electric field   is required   <...
Why Superconductivity in RF linacs? <ul><li>In normal conducting linac a  huge amount of power  is deposited in the copper...
Superconductivity whenever possible  <ul><li>For a good but  not perfect conductor  ( ρ   ≠  0) , the  fields and currents...
Superconductivity whenever possible  <ul><li>Superconductivity,  drastically reduces the dissipated power.  But some  draw...
Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron p...
ADS proton beam requirements <ul><li>Very high duty cycle, possibly CW  </li></ul><ul><li>Energy of the order of 1 GeV, de...
The proton linacs
Linac or cyclotron 1/2 <ul><li>Most powerful CW proton accelerators (MW-size facilities) </li></ul><ul><li>Linacs </li></u...
Linac or cyclotron 2/2 <ul><li>Cyclotron </li></ul><ul><li>No remarkable R&D programs </li></ul><ul><li>Its cost scales qu...
The ADS Linac <ul><li>Linac benefits of  impressive progresses  in the field of  SC cavities: </li></ul><ul><ul><li>SC tec...
Reference Linac Design Proton  Source RFQ Medium energy ISCL linac 3 sections high energy SC linac 80 keV 5 MeV ~ 100 MeV ...
Linac Design <ul><li>Accelerator design performed in the EU PDS-XADS program (5° FWP) </li></ul><ul><ul><li>Choice of supe...
Injector, an example: LEDA at LANL RFQ Concept 1.2 MW (structure) 670 kW (beam) RF Power 8 m (4 sections) Length 6.7 MeV F...
High energy section: the test module  Elliptical   =0.47 cavities have been produced, vertically tested and will be equip...
The Reliability Issue <ul><li>The small number (few per year) of beam trips allowed during the accelerator operation, requ...
Some Remarks  on  Linac  Reliability <ul><li>In order to meet the # of stops > 1 s </li></ul><ul><ul><li>The beam startup ...
Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron p...
SNS Guiding Principles <ul><li>SNS will provide  high availability, high reliability  operation of the world’s most powerf...
The Spallation Neutron Source
Neutron generation <ul><li>H-  ions are produced in the front end  ion source </li></ul><ul><li>H-  are  accelerated to ~1...
Power Ramp-up Progress <ul><li>“We are starting to get to real beam power levels” </li></ul>160 KW: ISIS Power Record
Beam Target and Neutron Moderation <ul><li>Spallation target </li></ul><ul><li>Mercury was chosen for the target for sever...
Layout of RF Linac 805 MHz, 0.55 MW klystron 805 MHz, 5 MW   klystron 402.5 MHz, 2.5 MW klystron SRF, ß=0.61, 33 cavities ...
Normal Conducting Linac <ul><li>CCL Systems designed and built by Los Alamos  </li></ul><ul><li>805 MHz CCL accelerates be...
Superconducting Linac <ul><li>Designed an built by Jefferson Laboratory </li></ul><ul><li>SCL accelerates beam from 186 to...
Others SNS Parameters <ul><li>Protons per pulse on target 1.5x10 14  protons  </li></ul><ul><li>Energy per pulse on target...
SNS Instruments
Q-   Diagram for Inelastic Instruments adapted from “Neutron Scattering Instrumentation for a High-Powered Spallation Sou...
SNS Reflectometers R min < 5×10 -10 Q max  ~ 1.5 Å -1  (Liquids)   ~ 7 Å -1  (Magnetism) d min ~ 7 Å 50-100× NIST NG-1 Mag...
Diffraction <ul><li>Highest flux a short wavelengths is crucial for studies of local disorder in complex materials </li></...
High Pressure Cells Limit Sample Volume <ul><li>Pressure cell of the type to be employed on SNAP (Spallation Neutrons and ...
Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron p...
IFMIF general information <ul><li>IFMIF </li></ul><ul><li>Irradiation tool to qualify advanced materials resistant to extr...
ITER 3 dpa/lifetime IFMIF 20-55 dpa/year Plasma Facing Materials Structural Materials Functional Materials Advanced Materi...
IFMIF Main Objectives <ul><li>Neutron  flux :  10 MW deuton beam power on the test module is equivalent to </li></ul><ul><...
IFMIF Principles RFQ HWR HEBT <ul><li>Typical reactions </li></ul><ul><ul><li>7 Li(d,2n) 7 Be </li></ul></ul><ul><ul><li>6...
IFMIF “Artist View” Ion Source RF Quadrupole Post Irradiation Experiment Facilities High Energy Beam Transport Li Target L...
IFMIF Accelerator <ul><li>A high intensity ion source, delivers a beam of deutons of 140 mA to 100 keV </li></ul><ul><li>A...
IFMIF EVEDA design <ul><li>Accelerator Prototype (scale 1:1) </li></ul><ul><li>Ion Source </li></ul><ul><li>RadioFrequency...
Accelerator Reference Design High Energy Beam Transport (HEBT) Large Bore Quad & Dipoles, 43 m long SC Half-wave resonator...
Injector - Conception <ul><li>Specifications </li></ul><ul><li>rms emittance = 0.25   .mm.mrad (normalized ) </li></ul><u...
Injector – Initial LEBT design Cone Cameras ACCT Cameras Neutron detector Emittance Monitor  DC toroid on HV cable Movable...
Radio-Frequency Quadrupole <ul><li>RFQ Length  9.6 meters </li></ul><ul><li>RFQ transmission OK  99% (w/o error) </li></ul...
Old design: DTL and Matching Section 1st tank parameters Conventional Alvarez technology 1 RF coupler / tank RF Frequency ...
Present design:  Half-wave resonators (HWR)  IFMIF/EVEDA Project Committee meeting (10-11 October 2007) Accelerator Facili...
Lithium target <ul><li>Engineering design of the target system includes  thermal, thermo-structural and thermo-hydraulic a...
Principle of Test Modules 2 m D + Medium Flux Test Modules High Flux Test Module Low Flux Irradiation Tubes Lithium Target...
Irradiation modules overview VIT MF-CF MF-LBV MF-TR Upper internal flange Upper reflector Lateral reflector 12 rigs Lower ...
IFMIF Medium Flux Test Module 3 independent samples in creep fatigue
Conclusions <ul><li>Present and future large facilities are based to a large extent on the superconducting  RF linac techn...
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Serena barbanotti INFN milano

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international workshop accelerator based neutron sources for medical industrial and scientific applications torino eurosea international workshop accelerator based neutron sources for medical industrial and scientific applications torino eurosea

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  • Serena barbanotti INFN milano

    1. 2. Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron production with accelerators </li></ul></ul><ul><li>What is a high power accelerator and how does it work? </li></ul><ul><ul><li>General layout </li></ul></ul><ul><ul><li>Superconductive choice </li></ul></ul><ul><li>Applications of accelerator driven neutron sources </li></ul><ul><ul><li>Waste Transmutation (ADS) </li></ul></ul><ul><ul><li>Materials studies (SNS) </li></ul></ul><ul><ul><li>Fusion (IFMIF) </li></ul></ul>
    2. 3. Why Accelerators <ul><li>Easily pulsed beams </li></ul><ul><li>No chain reactions </li></ul><ul><li>Very high typical fluxes </li></ul><ul><ul><li>A 1 mA beam delivers to the target 6·10 15 particles per second </li></ul></ul>
    3. 4. Accelerators and Neutrons <ul><li>The accelerator </li></ul><ul><li>A particle accelerator is delivering energy to the beam via a rotational electric field acting on the charged particles. </li></ul><ul><li>Depending on the reaction chosen for neutron production, either proton or deutons are accelerated (high intensity simple particles with maximum charge to mass ratio). </li></ul><ul><li>Superconducting accelerators are preferred for their higher efficiency in the power conversion from plug to beam. </li></ul>
    4. 5. Accelerators and Neutrons <ul><li>The neutron source </li></ul><ul><li>High intensity charged particle beams are used to produce high intensity neutron fluxes for several applications </li></ul><ul><li>The neutron flux is determined by the charged particle flux through a simple nuclear process on a beam target (spallation or stripping reaction) </li></ul><ul><li>Different materials are chosen and different particles are accelerated, depending on power density, application, … </li></ul>
    5. 6. Accelerators and Neutrons <ul><li>Beam target choice </li></ul><ul><li>High Z materials for spallation -> high efficiency neutron conversion </li></ul><ul><li>Liquid or solid, depending on power density </li></ul><ul><ul><li>for good neutron economy is required to minimize target dimension </li></ul></ul><ul><ul><li>very high power density on target </li></ul></ul><ul><ul><li>liquid target are preferred (heat removal by convection) </li></ul></ul><ul><ul><li>solid target have power limit </li></ul></ul><ul><li>Beam – liquid target interface: window or windowless ? </li></ul><ul><li>Window related problems: </li></ul><ul><ul><li>window cooling </li></ul></ul><ul><ul><li>cyclic thermal loading on the window under creep condition </li></ul></ul><ul><ul><li>very corrosive environment (using lead) </li></ul></ul><ul><ul><li>radiation damage induced by proton and neutron in the window material </li></ul></ul>
    6. 7. Neutron generation 1/3 <ul><li>Spallation reaction </li></ul><ul><ul><li>An heavy metal target hit by a high energy proton generates neutrons </li></ul></ul><ul><ul><ul><li>proton ~1 GeV -> 20 - 30 neutrons </li></ul></ul></ul><ul><ul><li>Characteristics : </li></ul></ul><ul><ul><ul><li>High conversion factor neutrons/protons </li></ul></ul></ul><ul><ul><ul><li>Wide neutron energy spectrum </li></ul></ul></ul><ul><ul><ul><li>For high neutron production efficiency, required high energy proton beam </li></ul></ul></ul>
    7. 8. Neutron generation 2/3 <ul><li>Stripping reaction </li></ul><ul><ul><li>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 </li></ul></ul><ul><ul><li>Typical reactions: </li></ul></ul><ul><li>7 Li(d,2n) 7 Be 6 Li(d,n) 7 Be 6 Li(n,T) 4 He </li></ul><ul><ul><li>Characteristics : </li></ul></ul><ul><ul><ul><li>Lower conversion factor </li></ul></ul></ul><ul><ul><ul><li>Peaked neutron energy spectrum: 14 MeV </li></ul></ul></ul><ul><ul><ul><li>Required low energy beam </li></ul></ul></ul>
    8. 9. <ul><li>Spallation reaction </li></ul><ul><li>ADS </li></ul><ul><li> SNS </li></ul>Neutron generation 3/3 <ul><li>Stripping reaction </li></ul><ul><li>IFMIF </li></ul>Proton beam Proton beam
    9. 10. Applications 1/3 <ul><li>Nuclear fusion (IFMIF) </li></ul><ul><li>Fusion reactors will produce high neutron fluxes at 14 MeV </li></ul><ul><li>This will bring to high material irradiation </li></ul><ul><li>To guarantee reactor operation, required materials with: </li></ul><ul><ul><li>ITER: 3 dpa/lifetime </li></ul></ul><ul><ul><li>DEMO: > 20 dpa/year </li></ul></ul><ul><li>Required a material test facility for material verifications </li></ul>
    10. 11. Applications 2/3 <ul><li>Nuclear Waste Trasmutation (ADS) </li></ul><ul><li>Problem: Disposal of Nuclear Waste </li></ul><ul><ul><li>Reduce radiotoxicity of the waste </li></ul></ul><ul><ul><li>Minimize volume/heat load of waste </li></ul></ul><ul><li>Strategy: Partitioning and Transmutation </li></ul><ul><ul><li>Separate chemically the waste (Pu, MA, LLFF) </li></ul></ul><ul><ul><li>Use the waste as fuel in dedicated transmuter systems </li></ul></ul><ul><li>Solution: a transmuter has 2 ingredients </li></ul><ul><ul><li>A subcritical reactor (k<1), with U-free fuel: chain reaction is not self-sustained </li></ul></ul><ul><ul><li>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) </li></ul></ul>
    11. 12. Application 3/3 <ul><li>Material science (SNS) </li></ul><ul><li>Neutrons provide unique insight into materials at the atomic level: </li></ul><ul><ul><li>‘ see’ light atoms in biomaterials and polymers </li></ul></ul><ul><ul><li>study magnetic properties and atomic motion </li></ul></ul><ul><ul><li>measure stress in engineering components </li></ul></ul>
    12. 13. The accelerators ~ dm 2 ~ dm 2 ~ dm 2 Beam dimension 14 MeV Wide spectrum Wide spectrum Neutron energy 10 MW 1.4 MW ~ 20 MW Total beam power 2 * 125 mA 1.4 mA 20-40 mA Average beam current Continuous Pulsed: 60 Hz – 695 ns Continuous Beam operation Stripping deuton - Litium Spallation on liquid mercury Spallation on liquid lead/bismuth Neutron production deutons H-, converted in p at accumulator ring protons Accelerates With window With window Windowless Target area ~ 40 MeV ~ 1 GeV ~ 600-1000 MeV Beam energy IFMIF SNS ADS
    13. 14. Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron production with accelerators </li></ul></ul><ul><li>What is a high power accelerator and how does it work? </li></ul><ul><ul><li>General layout </li></ul></ul><ul><ul><li>Superconductive choice </li></ul></ul><ul><li>Applications of accelerator driven neutron sources </li></ul><ul><ul><li>Waste Transmutation (ADS) </li></ul></ul><ul><ul><li>Materials studies (SNS) </li></ul></ul><ul><ul><li>Fusion (IFMIF) </li></ul></ul>
    14. 15. Particle Accelerators <ul><li>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. </li></ul><ul><li>For protons and ions that has been the case for a while: </li></ul><ul><ul><li>Electrostatic accelerators </li></ul></ul><ul><ul><li>Linacs </li></ul></ul><ul><ul><li>Cyclotrons </li></ul></ul><ul><li>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. </li></ul>
    15. 16. Basic Concepts: Fields <ul><li>Equation of motion and Lorentz force </li></ul><ul><ul><li>Electric field can transfer energy to the particles </li></ul></ul><ul><ul><li>Magnetic field can guide the beam in a stable path </li></ul></ul><ul><li>All Particle Accelerators are based on these rules </li></ul><ul><ul><li>The beam moves inside a vacuum chamber </li></ul></ul><ul><ul><li>Electromagnetic objects placed on the beam path perform the tasks: </li></ul></ul><ul><ul><ul><li>Magnets guide the beam on the chosen trajectory (dipoles) and provide focusing (quadrupoles) </li></ul></ul></ul><ul><ul><ul><li>Resonant RF cavities (exceptions: Betatron, RFQ and Electrostatic Accelerators) are used to apply the electric accelerating field </li></ul></ul></ul>
    16. 17. Some Milestones for Accelerators <ul><li>20th century first 25 years </li></ul><ul><li>from 1928 to 1932 </li></ul><ul><li>1928 </li></ul><ul><li>1929 </li></ul><ul><li>1944 </li></ul><ul><li>1946 </li></ul><ul><li>1950 </li></ul><ul><li>1951 </li></ul><ul><li>1956 </li></ul><ul><li>1970 </li></ul><ul><li>early 80's </li></ul><ul><li>the last years </li></ul><ul><li>Prehistory : fundamental discoveries made with &quot;beams&quot; from radioactive source trigger the demand for higher energies </li></ul><ul><li>Cockcroft&Walton develop a 700kV electrostatic accelerator based on a voltage multiplier </li></ul><ul><li>First Linac by Wideroe based on resonant acceleration </li></ul><ul><li>Lawrence invents the cyclotron </li></ul><ul><li>MacMillan, Oliphant & Veksler develop the synchrotron </li></ul><ul><li>Alvarez builts a proton linac with Alvarez structures (2  mode) </li></ul><ul><li>Christofilos patents the concept of strong focusing </li></ul><ul><li>Alvarez conceives the tandem </li></ul><ul><li>Kerst stresses in a paper the concept of a collider </li></ul><ul><li>Kapchinski & Telyakov invent the radio-frequency quadrupole RFQ </li></ul><ul><li>superconducting magnets for cylotrons and synchrotrons considerably boost the performance (energy for size) </li></ul><ul><li>the development of superconducting accelerating cavities provides very high power conversion efficiency </li></ul>
    17. 18. Accelerators evolution: the Livingston chart <ul><li>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 . </li></ul><ul><li>50 years later, that still holds true. </li></ul><ul><li>In other words, so far, builders of accelerators have managed exponential growth , every ten years , roughly a factor of 33 is won . </li></ul><ul><li>Note that for a given &quot; family &quot; of accelerators, saturation of maximum energy sets in after some time. </li></ul>future E = m c 2
    18. 19. <ul><li>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” </li></ul><ul><li>Two possible designs : </li></ul><ul><ul><li>NC Travelling wave structures </li></ul></ul><ul><ul><li>SC Standing wave cavities </li></ul></ul>Linac RF acceleration concept Traveling wave V ph ≈ c and Vg < c Standing wave V ph = 0 and Vg = c  mode bunches Electric field
    19. 20. RF Linac Overview Particle Source Linac structure : Acceleration (cavities) Transverse focusing (magnets) Electric power Vacuum Cooling RF power and controls Output beam (experiments, users, applications ...) Subsystems SNS - ORNL TTF - DESY
    20. 21. Energy gain and dissipated power <ul><li>To accelerate particles efficiently, very high electric field is required </li></ul><ul><li>In any structure (cavity) holding an electromagnetic field, both dissipated power and stored energy scale quadratically with the fields </li></ul><ul><li>The efficiency of a cavity depends from: </li></ul><ul><ul><li>Its quality factor, Q </li></ul></ul><ul><ul><li>driven by the surface resistance, R s </li></ul></ul><ul><ul><li>Its shunt impedance, r </li></ul></ul><ul><ul><li>function of the cavity geometry </li></ul></ul><ul><ul><li>and of the surface resistance, R s </li></ul></ul><ul><li>For efficient acceleration Q, r and r/Q must all be as high as possible </li></ul>U is the energy stored in the cavity P diss is the power dissipated on its surface Δ V is the voltage seen by the beam “ r over Q ” is purely a geometrical factor <ul><li>Good material for maximum Q and r (that is minimum P diss ) </li></ul><ul><li>Good design for maximum r/Q </li></ul>L R C
    21. 22. Why Superconductivity in RF linacs? <ul><li>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) </li></ul><ul><ul><li>Dissipated power can be much higher than the power transferred into the beam for acceleration </li></ul></ul><ul><li>Superconductivity , at the expenses of higher complexity, drastically reduces the dissipated power and the cavities transfer more efficiently the RF power to the beam </li></ul><ul><li>In short: </li></ul><ul><ul><li>NC linac: lower capital cost, but high operational cost </li></ul></ul><ul><ul><li>SC linac: slightly higher capital cost, but low operational cost </li></ul></ul>
    22. 23. Superconductivity whenever possible <ul><li>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 ) </li></ul><ul><li>With RF fields, a SC cavity dissipate power, not all electrons are in Cooper pairs. </li></ul><ul><li>In NC linac a huge amount of power is deposited in the copper structure: MW to have MV </li></ul><ul><ul><li>Pulsed operation and Low Duty Cycle </li></ul></ul>SC SuperConducting NC or RT NormalConducting Nb Cu
    23. 24. Superconductivity whenever possible <ul><li>Superconductivity, drastically reduces the dissipated power. But some drawbacks </li></ul><ul><ul><li>Higher complexity : refrigeration and cryomodules </li></ul></ul><ul><ul><ul><li>Carnot and refrigeration plant efficiencies </li></ul></ul></ul><ul><ul><li>Higher technology : cavity treatments </li></ul></ul><ul><ul><li>Simpler geometries: lower shunt impedance </li></ul></ul><ul><li>And two big advantages: </li></ul><ul><ul><li>Large bore radius : less beam losses </li></ul></ul><ul><ul><li>CW or high duty cicle preferred </li></ul></ul>
    24. 25. Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron production with accelerators </li></ul></ul><ul><li>What is a high power accelerator and how does it work? </li></ul><ul><ul><li>General layout </li></ul></ul><ul><ul><li>Superconductive choice </li></ul></ul><ul><li>Applications of accelerator driven neutron sources </li></ul><ul><ul><li>Waste Transmutation (ADS) </li></ul></ul><ul><ul><li>Materials studies (SNS) </li></ul></ul><ul><ul><li>Fusion (IFMIF) </li></ul></ul>
    25. 26. ADS proton beam requirements <ul><li>Very high duty cycle, possibly CW </li></ul><ul><li>Energy of the order of 1 GeV, determined by </li></ul><ul><ul><li>neutron production rate per GeV and per proton (optimum value reached at ~1 GeV) </li></ul></ul><ul><ul><li>energy dissipated in the input window (rapidly decreasing with energy, when E<few GeV) </li></ul></ul><ul><li>beam power from several MW up to tens of MW </li></ul><ul><ul><li>few MW for a “demo” plant of ~100 MWth </li></ul></ul><ul><ul><li>~20 MW for an industrial burner of ~1500 MWth </li></ul></ul><ul><li>Very few beam trips per year accepted if longer then 1 second </li></ul><ul><li>No limitation for very short beam trips: << 1 second </li></ul>
    26. 27. The proton linacs
    27. 28. Linac or cyclotron 1/2 <ul><li>Most powerful CW proton accelerators (MW-size facilities) </li></ul><ul><li>Linacs </li></ul><ul><ul><li>LAMPF/LANSCE (~1970) </li></ul></ul><ul><ul><ul><li>800 MeV </li></ul></ul></ul><ul><ul><ul><li>1 mA H + average current </li></ul></ul></ul><ul><ul><ul><li>Peak H + current 16.5 mA @ 100 Hz and 625  s pulse length </li></ul></ul></ul><ul><ul><ul><li>NC accelerator </li></ul></ul></ul><ul><li>Cyclotrons </li></ul><ul><ul><li>PSI – separated sector (1974) </li></ul></ul><ul><ul><ul><li>Original design was for 100  A </li></ul></ul></ul><ul><ul><ul><li>From 72 to 590 MeV </li></ul></ul></ul><ul><ul><ul><li>~2 mA average current </li></ul></ul></ul><ul><ul><ul><li>Beam losses at extraction < 1  A </li></ul></ul></ul>
    28. 29. Linac or cyclotron 2/2 <ul><li>Cyclotron </li></ul><ul><li>No remarkable R&D programs </li></ul><ul><li>Its cost scales quadratically with the output energy </li></ul><ul><li>Very high reliability and availability at PSI, but further improvement looks very difficult </li></ul><ul><li>Not applicables concepts of redundancy and spare on line </li></ul><ul><li>Linear Accelerator </li></ul><ul><li>A worldwide R&D effort is in progress </li></ul><ul><li>High potentiality of these machines has been proven: </li></ul><ul><ul><li>Sources, RFQs and SRF technology successfully operated </li></ul></ul><ul><li>cost per MeV is decreasing with energy </li></ul><ul><li>Linac (except front end) has intrinsic modularity: </li></ul><ul><ul><li>Easy redundant and “spares on line” design </li></ul></ul>
    29. 30. The ADS Linac <ul><li>Linac benefits of impressive progresses in the field of SC cavities: </li></ul><ul><ul><li>SC technology can be extended to proton linac down to  ~ 0.5 </li></ul></ul><ul><li>Intrinsic modularity simplify reliability issues </li></ul><ul><ul><li>Redundant design strategy based on the “spare-on-line” concept </li></ul></ul><ul><ul><li>Strong focusing and large beam aperture produce negligible losses </li></ul></ul><ul><li>The scheme generally considered consists of four different sections </li></ul><ul><ul><li>The proton source: proton energy  80-100 keV </li></ul></ul><ul><ul><li>The Radio Frequency Quadrupole ( RFQ ): up to  5 MeV </li></ul></ul><ul><ul><li>A medium energy section , either NC or SC: up to  100 MeV </li></ul></ul><ul><ul><li>A high energy section made of SC elliptical rf cavities: up to final energy  1 GeV (most of the linac is here!) </li></ul></ul>
    30. 31. Reference Linac Design 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 <ul><li>3 section linac: </li></ul><ul><ul><li>85/100 - 20 0 MeV,  =0. 47 </li></ul></ul><ul><ul><li>20 0 - 50 0 MeV,  =0.65 </li></ul></ul><ul><ul><li>50 0 – 1 0 00 /2000 MeV,  =0.8 5 </li></ul></ul><ul><li>Five (six) cell elliptical cavities </li></ul><ul><li>Quadrupole doublet focussing: multi - cavity cryostats between doublets </li></ul><ul><ul><li>704.4 MHz </li></ul></ul>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) High transmission 90% 30 mA, 5 MeV (352 MHz) Microwave RF Source High current (3 5 mA) 80 keV High Energy SC Linac ISCL RFQ Source
    31. 32. Linac Design <ul><li>Accelerator design performed in the EU PDS-XADS program (5° FWP) </li></ul><ul><ul><li>Choice of superconducting linac </li></ul></ul><ul><ul><li>Modular: same concept for Prototype and Industrial scale </li></ul></ul>
    32. 33. Injector, an example: LEDA at LANL RFQ Concept 1.2 MW (structure) 670 kW (beam) RF Power 8 m (4 sections) Length 6.7 MeV Final Energy 100 mA (95 %) Beam current LEDA RFQ: One Section of LEDA-RFQ The LEDA-RFQ fully installed
    33. 34. 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
    34. 35. The Reliability Issue <ul><li>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  </li></ul><ul><li>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). </li></ul>
    35. 36. Some Remarks on Linac Reliability <ul><li>In order to meet the # of stops > 1 s </li></ul><ul><ul><li>The beam startup procedure for a multi MW beam will be certainly > 1 s operation with faulty components needs to be achieved </li></ul></ul><ul><ul><ul><li>Linac must tolerate single failures of most of components </li></ul></ul></ul><ul><ul><ul><li>Procedures for “adjusting” beam transport and repairing of components without interrupting the beam while marinating acceptable losses </li></ul></ul></ul><ul><li>As a consequence </li></ul><ul><ul><li>Components and subsystems divided in two major categories if they lead to: </li></ul></ul><ul><ul><ul><li>Failures requiring a beam stop </li></ul></ul></ul><ul><ul><ul><li>Failures that can be repaired while the beam is on, or later… </li></ul></ul></ul><ul><li>As general rules </li></ul><ul><ul><li>Components falling in the first category should have the highest reliability </li></ul></ul><ul><ul><ul><li>Typically passive components overdesigned and overtested </li></ul></ul></ul><ul><ul><li>Components falling in the second category should have the highest accessibility for repairing or substitution </li></ul></ul><ul><li>For 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.) </li></ul>
    36. 37. Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron production with accelerators </li></ul></ul><ul><li>What is a high power accelerator and how does it work? </li></ul><ul><ul><li>General layout </li></ul></ul><ul><ul><li>Superconductive choice </li></ul></ul><ul><li>Applications of accelerator driven neutron sources </li></ul><ul><ul><li>Waste Transmutation (ADS) </li></ul></ul><ul><ul><li>Materials studies (SNS) </li></ul></ul><ul><ul><li>Fusion (IFMIF) </li></ul></ul>
    37. 38. SNS Guiding Principles <ul><li>SNS will provide high availability, high reliability operation of the world’s most powerful pulsed neutron source </li></ul><ul><li>Research conducted at SNS will be at the forefront of biology, chemistry, physics, materials science and engineering </li></ul><ul><ul><li>SNS will be able to provide cold neutrons (useful for research on polymers and proteins) </li></ul></ul><ul><li>SNS expects 1000-2000 users per year from academia, government, and industry </li></ul><ul><li>Flexible instrument strategy that supports both general user access and dedicated access for expert instrument teams that contribute to construction and operation of instruments </li></ul>
    38. 39. The Spallation Neutron Source
    39. 40. Neutron generation <ul><li>H- ions are produced in the front end ion source </li></ul><ul><li>H- are accelerated to ~1GeV in Linac (NC and SC) </li></ul><ul><li>On injection into ring 2x e- are stripped to form p </li></ul><ul><li>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) </li></ul><ul><li>A kicker magnet knocks the proton pulse out of the ring orbit into the beamline that takes the p’s to the Hg target </li></ul><ul><li>Beam losses need to be preserved below 1 W/m along the whole machine and beamlines to limit activation </li></ul>
    40. 41. Power Ramp-up Progress <ul><li>“We are starting to get to real beam power levels” </li></ul>160 KW: ISIS Power Record
    41. 42. Beam Target and Neutron Moderation <ul><li>Spallation target </li></ul><ul><li>Mercury was chosen for the target for several reasons </li></ul><ul><ul><li>it is not damaged by radiation, as are solids </li></ul></ul><ul><ul><li>it has a high atomic number, making it a source of numerous neutrons (the average mercury nucleus has 120 neutrons and 80 protons) </li></ul></ul><ul><ul><li>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 </li></ul></ul><ul><li>Neutron moderation </li></ul><ul><li>The neutrons coming out of the target must be turned into low-energy neutrons suitable for research </li></ul><ul><ul><li>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) </li></ul></ul><ul><ul><li>The moderators are located above and below the target </li></ul></ul>
    42. 43. Layout of RF Linac 805 MHz, 0.55 MW klystron 805 MHz, 5 MW klystron 402.5 MHz, 2.5 MW klystron SRF, ß=0.61, 33 cavities 1 from CCL 186 MeV 86.8 MeV 2.5 MeV RFQ (1) DTL (6) CCL (4) SRF, ß=0.81, 48 cavities 1000 MeV (81 total powered) 379 MeV Warm Linac SCL Linac
    43. 44. Normal Conducting Linac <ul><li>CCL Systems designed and built by Los Alamos </li></ul><ul><li>805 MHz CCL accelerates beam to 186 MeV </li></ul><ul><li>System consists of 48 accelerating segments, 48 quadrupoles, 32 steering magnets and diagnostics </li></ul><ul><li>402.5 MHz DTL was designed and built by Los Alamos </li></ul><ul><li>Six tanks accelerate beam to 87 MeV </li></ul><ul><li>System includes 210 drift tubes, transverse focusing via PM quads, 24 dipole correctors, and associated beam diagnostics </li></ul>
    44. 45. Superconducting Linac <ul><li>Designed an built by Jefferson Laboratory </li></ul><ul><li>SCL accelerates beam from 186 to 1000 MeV </li></ul><ul><li>SCL consists of 81 cavities in 23 cryomodules </li></ul><ul><li>Two cavities geometries are used to cover broad range in particle velocities </li></ul><ul><li>Cavities are operated at 2.1 K with He supplied by Cryogenic Plant </li></ul>Medium beta cavity High beta cavity
    45. 46. Others SNS Parameters <ul><li>Protons per pulse on target 1.5x10 14 protons </li></ul><ul><li>Energy per pulse on target 24 kJ </li></ul><ul><li>Average linac macropulse H- current 26 mA </li></ul><ul><li>Linac beam macropulse duty factor 6% </li></ul><ul><li>Front end length 7.5 m </li></ul><ul><li>Linac length 331 m </li></ul><ul><li>HEBT length 170 m </li></ul><ul><li>Ring circumference 248 m </li></ul><ul><li>RTBT length 150 m </li></ul><ul><li>Ion type (Ring, RTBT, Target) proton  </li></ul><ul><li>Ring filling time 1.0 ms </li></ul><ul><li>Ring revolution frequency 1.058 MHz </li></ul><ul><li>Number of injected turns 1060  </li></ul><ul><li>Ring filling fraction 68% </li></ul><ul><li>Ring extraction beam gap 250 ns </li></ul><ul><li>Maximum uncontrolled beam loss 1 W/m </li></ul><ul><li>Number of ambient / cold moderators 1/3  </li></ul><ul><li>Number of neutron beam shutters 18  </li></ul>
    46. 47. SNS Instruments
    47. 48. Q-  Diagram for Inelastic Instruments adapted from “Neutron Scattering Instrumentation for a High-Powered Spallation Source” R. Hjelm, et al., LA0-UR 97-1272 Momentum Distributions Itinerant Magnets Crystal Fields Molecular Vibrations Lattice Vibrations Small Molecule Diffusion Large Scale Motions Polymers and Biological Systems Tunneling Spectroscopy Electron-Phonon Interactions Hydrogen Modes Molecular Reorientation Ultracold Neutrons Fundamental Physics Slower Motions Larger Objects ARCS THERMAL CHOPPER SPECT COLD NEUTRON CHOPPER SPECT BACKSCATTERING SPECTROMETER
    48. 49. SNS Reflectometers R min < 5×10 -10 Q max ~ 1.5 Å -1 (Liquids) ~ 7 Å -1 (Magnetism) d min ~ 7 Å 50-100× NIST NG-1 Magnetism: vertical sample Liquids: horizontal sample
    49. 50. Diffraction <ul><li>Highest flux a short wavelengths is crucial for studies of local disorder in complex materials </li></ul><ul><li>Nanoscale Ordered Materials Diffractometer (NOMAD) </li></ul>
    50. 51. High Pressure Cells Limit Sample Volume <ul><li>Pressure cell of the type to be employed on SNAP (Spallation Neutrons and Pressure) beamline </li></ul>
    51. 52. Index <ul><li>Introduction: why accelerators as source for neutrons? </li></ul><ul><ul><li>General principles of neutron production with accelerators </li></ul></ul><ul><li>What is a high power accelerator and how does it work? </li></ul><ul><ul><li>General layout </li></ul></ul><ul><ul><li>Superconductive choice </li></ul></ul><ul><li>Applications of accelerator driven neutron sources </li></ul><ul><ul><li>Waste Transmutation (ADS) </li></ul></ul><ul><ul><li>Materials studies (SNS) </li></ul></ul><ul><ul><li>Fusion (IFMIF) </li></ul></ul>
    52. 53. IFMIF general information <ul><li>IFMIF </li></ul><ul><li>Irradiation tool to qualify advanced materials resistant to extreme radiation conditions (DEMO reactor) </li></ul><ul><li>Requires an intense neutron flux (~ 10 17 n/s/m 2 ) at 14 MeV </li></ul><ul><li>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 </li></ul><ul><li>IFMIF-EVEDA (Engineering Validation Engineering Design Activities) </li></ul><ul><li>Engineering design of the IFMIF facility, safety assessment for a generic site and preparation of the technical specifications for the longest delivery components </li></ul><ul><li>Design and construction of low energy section of the first accelerator </li></ul><ul><li>Design, construction and tests of a scale 1:3 model of the Target Facility </li></ul><ul><li>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 </li></ul>
    53. 54. ITER 3 dpa/lifetime IFMIF 20-55 dpa/year Plasma Facing Materials Structural Materials Functional Materials Advanced Materials are at a critical path DEMO 30 dpa/year
    54. 55. IFMIF Main Objectives <ul><li>Neutron flux : 10 MW deuton beam power on the test module is equivalent to </li></ul><ul><ul><li>1 MW/m 2 neutron beam </li></ul></ul><ul><ul><li>4.5 10 17 n/m 2 /s </li></ul></ul><ul><ul><li>3 10 -7 dpa/s for Fe </li></ul></ul><ul><li>Neutron spectrum : fit to probable DEMO first wall </li></ul><ul><li>Neutron fluence accumulation : DEMO relevant (150 dpa/few years) </li></ul><ul><li>Neutron flux gradient : about 10 % in volume </li></ul><ul><li>Machine availability : 70 % (quasi continuous operation) </li></ul><ul><li>Good accessibility of irradiation volume for experimentation and instrumentation </li></ul>neutron flux coolant flow (He) 200 50 50 [mm]
    55. 56. IFMIF Principles RFQ HWR HEBT <ul><li>Typical reactions </li></ul><ul><ul><li>7 Li(d,2n) 7 Be </li></ul></ul><ul><ul><li>6 Li(d,n) 7 Be </li></ul></ul><ul><ul><li>6 Li(n,T) 4 He </li></ul></ul>Source Accelerator (x 2) Test Cell Low flux (< 1 dpa/an, > 8 L) Medium flux (20 – 1 dpa/an, 6 L) Lithium target High flux (> 20 dpa/an, 0.5 L)
    56. 57. IFMIF “Artist View” Ion Source RF Quadrupole Post Irradiation Experiment Facilities High Energy Beam Transport Li Target Li Loop Test Modules inside Test Cells Half-wave resonators 0 20 40 m
    57. 58. IFMIF Accelerator <ul><li>A high intensity ion source, delivers a beam of deutons of 140 mA to 100 keV </li></ul><ul><li>A RFQ (Radio Frequency Quadrupole) cavity put « in packages » and accelerate the deutons until a 5 MeV energy </li></ul><ul><li>Elements of linear accelerator to reach the final energy (10 MeV at EVEDA, 40 MeV at IFMIF) </li></ul><ul><li>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 </li></ul>
    58. 59. IFMIF EVEDA design <ul><li>Accelerator Prototype (scale 1:1) </li></ul><ul><li>Ion Source </li></ul><ul><li>RadioFrequency Quadrupole </li></ul><ul><li>Matching Section </li></ul><ul><li>Half Wave Resonators linac </li></ul><ul><li>HEBT and Beam Dump </li></ul><ul><li>Building (at Rokkasho) for the test of the accelerator </li></ul><ul><li>Lithium Loop (scale 1:3) </li></ul><ul><li>Diagnostics </li></ul><ul><li>Erosion/Corrosion </li></ul><ul><li>Purification system </li></ul><ul><li>Remote Handling </li></ul><ul><li>High Flux Test Module (HFTM) </li></ul><ul><li>Irradiation in fission reactor </li></ul><ul><li>Validation of sample concepts </li></ul>~ ~
    59. 60. Accelerator Reference Design High Energy Beam Transport (HEBT) Large Bore Quad & Dipoles, 43 m long SC Half-wave resonators acceleration to 40 MeV Radio Frequency Quadrupole (RFQ) bunching & acceleration 5 MeV; MS to DTL RF Power System 175 MHz 12 RF amplifiers, 1MW CW 100 keV Injector Ion Source 140 mA D + , 100 keV LEBT transfer/match to RFQ 5 MeV 40 MeV 125 mA deuton beam Control Command  2
    60. 61. Injector - Conception <ul><li>Specifications </li></ul><ul><li>rms emittance = 0.25  .mm.mrad (normalized ) </li></ul><ul><li>beam current = 140 mA </li></ul><ul><li>energy = 100 keV </li></ul><ul><li>The injector components </li></ul><ul><li>the ECR (Electron Cyclotron Resonance) ion source must deliver 140 mA beam current with an output energy of 100 keV </li></ul><ul><li>the LEBT (Low Energy Beam Transport) section includes </li></ul><ul><ul><li>magnetic lenses (focusing and beam matching to the RFQ) </li></ul></ul><ul><ul><li>beam instrumentation : charge, current, profile, size, emittance measurement </li></ul></ul><ul><li>the associated infrastructure: power supplies, control system, water cooling </li></ul>
    61. 62. Injector – Initial LEBT design Cone Cameras ACCT Cameras Neutron detector Emittance Monitor DC toroid on HV cable Movable ConFlat Species identification* Thermocouples *fluorescence + shifted Doppler lines analysis
    62. 63. Radio-Frequency Quadrupole <ul><li>RFQ Length 9.6 meters </li></ul><ul><li>RFQ transmission OK 99% (w/o error) </li></ul><ul><li>Losses above 1 MeV kept at low level 0.01 % </li></ul><ul><li>Voltage and Power levels moderate </li></ul><ul><li>< V > = 102 kV, P = 1200  1480 kW </li></ul>RF study started Cu brazing joints e-beam & laser welding alternatives under study Mechanical design in a test phase
    63. 64. Old design: DTL and Matching Section 1st tank parameters Conventional Alvarez technology 1 RF coupler / tank 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 % Power coupler Stem-box Cover Tuning Slug Post Coupler Drift Tube Stem Drift Tube To vacuum pump Bulk Tuner
    64. 65. Present design: Half-wave resonators (HWR) IFMIF/EVEDA Project Committee meeting (10-11 October 2007) Accelerator Facility Project Plan Superconducting solution: existing modules module double of the one currently operating at SOREQ  L~ 5 m group cavities in long cryostats and conservative gradients Take 175 MHz HWR with big aperture 8-10-12 6 4.5 MV/m 40-50 mm SC IFMIF 5.5 MV/m 30 mm SARAF* project
    65. 66. Lithium target <ul><li>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 </li></ul>The Lithium circuit The Lithium target Quench Tank Deuteron Beams Li Target ( T 2.5 cm, W 26 cm) EM Pump HX(Li / Organic Oil) Dump Tank (9 m 3 -Li) HX(Organic Oil / Water) 130 L/s, 250  C Cold Trap (220  C) N Hot Trap (600  C) T Hot Trap (250  C)
    66. 67. Principle of Test Modules 2 m D + Medium Flux Test Modules High Flux Test Module Low Flux Irradiation Tubes Lithium Target Lithium Tank Shield plug
    67. 68. Irradiation modules overview VIT MF-CF MF-LBV MF-TR Upper internal flange Upper reflector Lateral reflector 12 rigs Lower reflector Helium inlet duct Helium exit duct HFTM
    68. 69. IFMIF Medium Flux Test Module 3 independent samples in creep fatigue
    69. 70. Conclusions <ul><li>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 </li></ul><ul><ul><li>LEP at CERN (e+e- collider with SRF cavities) </li></ul></ul><ul><ul><li>CEBAF at TJNAF (recirculated SRF linac) </li></ul></ul><ul><ul><li>TESLA and ILC (next generation linear colliders proposed for precision physics in the Higgs sector after LHC discovery) </li></ul></ul><ul><li>SNS moved from NC design to SC after project approval and during construction </li></ul><ul><li>Future facilities rely on SC linacs at even lower energies to benefit from SC technology </li></ul>

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