ns FFAGs and ADSRs what they are and

ns. FFAGs and ADSRs what they are and why you need them 1. The current ns. FFAG programme 2. Thorium ADSRs and their advantages 3. Matching the two Roger Barlow Manchester University Seminar 10 th June 2009

Accelerators 101 Cyclic accelerators use dipole magnets p=0. 3 B R 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 2

RF acceleration Positive kicks to the particles every time round f. RF= N fcirculating Problem: putting these together How to keep p = 0. 3 B R with increasing p? How to keep RF frequency in sync with changing particle revolution frequency 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 3

Solution 1: the Cyclotron • p=0. 3 B R – let R increase, B constant • frequency is constant Continuous current 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 4

Solution 2: The Synchrotron p=0. 3 B R – let B increase, R constant B Pulsed current 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs t 5

Solution 3: the FFAG Field varies in space But not in time – Fixed Field Increase in R is medium/small p=0. 3 B R holds 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 6

Focussing Particles in a bunch diverge Need to focus using quadrupole magnet Problem: a quad which focusses in X defocusses in Y Solution: a pair of quads has a net focussing effect Alternating Gradient (aka Strong Focussing) FFAG field contains quadrupole components 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 7

Accelerators 101 (contd. ) Off-axis particles oscillate about the reference orbit: Betatron Oscillations Tune: Number of betatron oscillations per turn Integer Tune (Resonance) =death 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs Imperfections: Errors in position, current etc in a magnet means a particle gets the wrong ‘kick’ Over many turns this smears out – if the particle is a different points on its betatron oscillation each time 8

Scaling Synchrotron during acceleration cycle: p=0. 3 B R • Bending dipoles and focussing quadrupoles carry same (increasing) current • The optics – prisms and lenses – looks the same • Tune stays constant • Setting the tune to something sensibly nonresonant means it stays there 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 9

Scaling FFAGs FFAG dipole and quadrupole fields not automatically in step To achieve needs complicated and slowly-varying magnetic field (B ~ Rk) – and hence large beam pipes Built in 1950 s for electrons – superseded by synchrotrons Now revived for protons in Japan 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs Why were FFAGs abandoned? Increase in momentum in FFAG ring limited to factor of 2 -5(? ) by geometry. Synchrotron AC magnets have much larger dynamic range – better for highest energies 10

Nonscaling FFAGs accelerate fast (hence great for muons): Limited by RF power, not by magnet ramping If we can go through a resonance quickly enough it may not matter. Drop scaling requirement – simpler and more compact. Will it work? Only one way to find out 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 11

EMMA Electron Machine with Many Applications 10 -20 Me. V electron accelerator 42 cells. 19 RF cavities. Accelerates in ~16 turns 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 12

ns. FFAG Benefits • • • High currents – like a cyclotron High energies – like a synchrotron A ring not a disc – cheaper than cyclotron Simple DC magnets Very large acceptance Fast acceleration time Smaller, more compact systems for proton acceleration – applications in medicine and power 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 13

Part 2. Shrinking our Carbon Footprint We all know fossil fuels are BAD because 1. They cause climate change 2. They are increasingly concentrated in countries with dodgy politics 3. They are going to run out Alternatives (windmills, solar power, improved insulation, retreat to the middle ages) can’t supply the deficit without …. 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 14

Nuclear Power Fossil fuels will need to be replaced by a basket of alternatives It is hard (impossible? ) to put such a basket together without nuclear power Big issues (real or in the eyes of the public? ) with: • Safety: Chernobyl and 3 Mile Island • Waste disposal. Storage for millenia - NIMBY • Proliferation. Rogue states and terrorist organisations 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 15

Safe Subcritical Reactors Each fission absorbs 1 neutron and produces ~2. 5 Some neutrons lost, leaving k neutrons to produce k fissions Conventional: Run with k=1 exactly k<1 stops k>1 explosion 10 th June 2009 Sub Critical Run with k<1 Use accelerator to supply extra neutrons Hence: Accelerator Driven Subcritical Reactor (ADSR) Roger Barlow: ns. FFAGs and ADSRs 16

ADSRs Spallation Target “Manifestly Safe” Switch off accelerator and reaction stops Energy balance is OK: need 5 - Accelerator 10% of power to run accelerator Can use Thorium as fuel 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs Core 17

Thorium Fertile, not fissile 232 Th +n 233 Th 233 Pa 233 U • Abundant. (Like lead) and spread around • Much smaller waste problems (no long-lived actinides) • Proliferation resistant 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 18

Energy Amplifier (Rubbia) Idea has been around for years Nobody’s built one yet! Feeling is that the accelerator is the weak point. 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 19

Waste from ADSR Needs storing – but not forever Minor Actinides (Np, Cm, Cf) are not produced 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 20

Transmutation • Neutron flux can burn actinides produced by conventional reactors. MYRRHA project. • Also destroy most-problematic fission products (e. g. 99 Tc: soluble, T½=211, 000 Y) by ‘Adiabatic Resonance Crossing’. Lead moderator to ensure neutrons hit the resonance for absorption 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 21

Accelerator requirements Proton Energy ~ 1 Ge. V gives ~20 spallation neutrons per proton. For 1 GW thermal power: • Need 3 1019 fissions/sec (200 Me. V/fission) • 6 1017 spallation neutrons/sec (k=0. 98 gives 50 fissions/neutron) • 3 1016 protons/sec Current 5 m. A. Power = 5 MW Reliable! Spallation target runs hot. If beam stops, target cools and stresses and cracks: no more than 3 trips per year Compare: PSI cyclotron: 590 Me. V, 2 m. A, 1 MW ISIS synchrotron: 800 Me. V, 0. 2 m. A, 0. 1 MW Several trips per day 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 22

Reliability: the 3 rd Frontier In the real world: Accelerators often trip for seconds/hours/days. They are complicated systems operating in real world environments But there are complex real world pieces of apparatus trip that trip rarely. Planes, computers, radio sets… 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 23

How to achieve Reliability must be paid for: • Parallelism • Robustness under failure • Under-rating • Preventive Maintenance Must throw money accurately at the problem Need thorough understanding of complete system and to learn from experience (with prototypes? ) 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 24

Accelerators for ADSRs Synchrotron Cyclotron Current far too high. Energy too high for classical cyclotron. On the edge for other types Complicated (ramping magnets) FFAG Linac Looks like the answer Can do the job. But VERY expensive “Cyclotron currents at Synchrotron energies” Simplicity = reliability 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 25

Proliferation: Issues and Questions “Thorium fuel system does not produce weapons” • Explains why nuclear power went the U/Pu route back in the 1950’s • Solves today’s dilemma of states like Iran Is it true? 1. ‘Dirty bomb’ 2. ‘Little boy’ type device 3. ‘Fat man’ type device 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 26

“Dirty Bomb” (Spent) fuel rods will contain fission products Dispersal over civilian areas would cause panic, expense, and few fatalities It is thought that during the 1960 s the UK Ministry of Defence evaluated RDD*s, deciding that a far better effect was achievable by simply using more high explosive in place of the radioactive material. Wikipedia * RDD: Radiological Dispersion Device 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 27

Enriched Thorium Can you build a bomb from Thorium, the counterpart of the 235 U device? No 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 28

233 U device In principle possible Critical mass ~15 kg No spontaneous fission problems: simple guntype device 233 U ratio in fuel stabilises after about 5 years. Extract chemically from Thorium 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 29

Together with 232 U 231 Pa then 231 Pa(n, ) 232 U 14 mb for neutron energies above threshold ~6 Me. V 232 Th(n, 2 n) 231 Th 233 U(n, 2 n) 232 U 4 mb for neutron energies above threshold ~6 Me. V Fast neutrons from tail of fission spectrum – or spallation 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 30

232 U : makes 233 U unworkable 232 U decays with a half life of 69 y, producing 228 Th which decays producing a 2. 8 Me. V ray. Really nasty stuff 50 ppm 232 in 233 gives (long term) ~2 rem/hr for a worker 0. 5 m from a 5 kg sphere. Health and safety limit 5 rem/y. Lethal doses 2001000 rem It is also bad for electronics 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 31

Possible loophole • Can’t separate U isotopes • Can chemically isolate the intermediate 233 Pa. • Wait (27 d half life) for it to decay to pure 233 U • Some MSR schemes use just this 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 32

Ionium to the rescue • Ionium is 230 Th • It does not occur in Thorium, which is pure 232 • It does occur in Uranium, part of the 238 U decay chain • ‘spike’ Thorium with Ionium: get Pa and 232 U 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 33

Proliferation: Conclusions • Safety depends on design • Advantage to have all fuel exposed to fast neutrons to ensure 232 U concentration • Ionium may be needed • Building a device will be very difficult. Technology beyond the reach of back street terrorists, detectable by WMD inspectors 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 34

Summary ADSRs provide a possible form of Nuclear Power that avoids the problems of • Critical accidents • Long-lived waste • Proliferation FFAGs may provide the best accelerator technology We (UK, Particle Physicists, Manchester, Cockcroft Institute) are working hard to make it happen 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 35

A way forward Formation of the Thorium Energy Amplifier Association: Universities and labs and industry A research consortium aimed at • Networking (website, workshops) • Sharing knowledge, within and outside UK • Arousing interest in Research Councils, Whitehall, etc. • Collaborative response to funding opportunities • Design of a Thorium ADSR, aimed at power generation with transmutation as bonus. FFAG is baseline accelerator If you’re interested, see www. thorea. org Next Meeting: Daresbury – July 10 th June 2009 Roger Barlow: ns. FFAGs and ADSRs 36