Accelerator Options for Hybrid Reactors Hywel Owen School of Physics and Astronomy University of Manchester

Some notable opinions about nuclear electricity “Everything that can be invented, has been invented” - Charles Duell, Commissioner, U.S. Office of Patents (1899). “The energy produced by the breaking down of the atom is a very poor kind of thing. Anyone who expects a source of power from the transformation of these atoms is talking moonshine.”- Ernest Rutherford. “There is no likelihood that man can ever tap the power of the atom. The glib supposition of utilizing atomic energy when our coal has run out is a completely unscientific Utopian dream, a childish bug-a-boo.” - Robert Millikan. “Fooling around with alternating current is just a waste of time. Nobody will use it, ever.”- Thomas Edison. “There is not the slightest indication that nuclear energy will ever be obtainable. It would mean that the atom would have to be shattered at will.” - Albert Einstein.

Leó Szilárd, Ernest Rutherford and the Chain Reaction In a Times article on March 6th 1933, Ernest Rutherford asserted: – ‘The energy produced by the atom is a very poor kind of thing. Anyone who expects a source of power from the transformation of these atoms is talking moonshine’ Leó Szilárd was apparently annoyed by this, and conceived of the nuclear chain reaction while waiting for traffic lights to changed in Bloomsbury, London, in 1933!

World Energy Usage 1 Quad = BTU ~ J ~ 33 GWy (Sankey Diagram)

World and UK Energy Usage World (2006): 471 EJ 15 TW 15,000 x 1 GW Nuclear Reactors UK (2004): 1.3 EJ 44 GW 44 x 1 GW Nuclear Reactors

But a few things have happened lately… Hirsch Report (USA, 2005) – Oil peaking presents a unique challenge… The world has never faced a problem like this. Without massive mitigation more than a decade before the fact, the problem will be pervasive and will not be temporary. Previous energy transitions, wood to coal and coal to oil, were gradual and evolutionary. Oil peaking will be abrupt and revolutionary.'’ European Large Combustion Plant Directive – Coal plants to be clean by Jan 1, 2016! – Most people think that alternative energy/conservation will fix things, but they can’t!

Energy Myths (from David Goodstein, ‘Out of Gas’) Oil companies produce oil We must conserve energy When we run out of oil, the marketplace will take over There’s enough fossil fuel in the ground to last for hundreds of years Nuclear energy is dangerous

Peak Oil (M.K.Hubbert, the original technocrat) Peak oil may or may not have already happened, but it will… Peak coal will happen this century (if we keep using it) Peak uranium will happen soon (disputed) David Goodstein again: – Civilisation as we know it will come to an end sometime in this century, when the fuel runs out M.K. Hubbert, Paper to American Petroleum Institute, Shell Pub. No. 95, (June 1956) A.R.Brandt, ‘Testing Hubbert’, Energy Policy 35, 3074 (2007)

Abundance of Fuel Sources

Thorium, Uranium and Lithium (Lithium figure is disputed) But anyway, fusion is still a long way away! MSR: Bowman et al., NIMA 1992 vol. 320 (1-2) pp Lead-Cooled: Rubbia et al., CERN/AT/94-47 & CERN/AT/95-44

Why proton beams? Idea is to create neutrons for fission Lots of experience with spallation sources Examples/projects of high power proton accelerators – APT – LAMPF – PSI – SNS Experimental measurements by Andrianmonje et al. using CERN PS S. Andriamonje et al., Physics Letters B, 1995 vol. 348 (3-4) pp

Alternatives to protons Deuteron beams – Similar target/geometry to proton spallation – Cross section for neutron production marginally greater – Harder to make deuteron beams – Increased accelerator problems (losses) – No significant advantage Electrons – Bremsstrahlung from e.g. tungsten convertor, then photofission in Th-232/U- 238 – ‘Simpler’ accelerator at much lower energy, but higher currents required – Lower neutron multiplicity – Chosen technology choice for radioisotope production

Mo-99 production Based on development of high-current superconducting technology for energy-recovery linacs Typical parameters are 100 mA, 50 MeV electrons (for 15 MeV photons) Intensity may not be high enough for required reactor neutron flux Single target vs. multiple targets? R. Bennett et al., Nuclear Technology, 1999 vol. 126 (1) pp. 102

Proton Drivers Options: – Linac Normal conducting Superconducting – Conventional cyclotron – FFAG Non-scaling FFAG – Rapid-cycling synchrotron Common issues: – Generation of large source charge – Beam loss (main concentration of current effort); maintainability requires losses ~ 1 W/m – Reliability (still poorly understood) Not issues: – Emittance

Intensity Development in Proton Drivers Thomas Roser, ICFA HB-2004 Workshop, October 18, 2004

Looked at another way… Reliability is the question… Thomas Roser, ICFA HB-2004 Workshop, October 18, 2004

Developments in Proton Drivers Low loss charge exchange injection (PSR, SNS, … Boosters (CERN, FNAL, BNL, KEK, … Rapid cycling synchrotron (FNAL, ISIS, … (CW) RFQs (LEDA,… Super-conducting rf (SNS, … Transition energy jump or avoidance (CERN, AGS, J- Parc, … RF beam loading compensation (AGS, … Electron cloud cures (LANL PSR,… AGS Development Thomas Roser, ICFA HB-2004 Workshop, October 18, 2004

High Power Design Challenges Design:Issues/challenges: CW or high DF:Cyclotron + p sourceE  1 GeV SC Linac + p sourceCW front end (RFQ, DTL) Low DF:Linac + accum. ringE  5 (8?) GeV (H - stripping) Linac + RCSRep. rate < 100 Hz Linac + FFAGRep. rate  1 kHz Linac + n  RCSFor high energy Bunch-to-bucket transfers High gradient, low frequency rf Thomas Roser, ICFA HB-2004 Workshop, October 18, 2004

Bowman proposal (1992) Note the length!! 1km to 2km, based on ~ few MV/m

Rubbia proposal (1995) Key points: – Single turn extraction – Common RF frequency – Higher-harmonic RF to flatten final energy spread – Wallplug efficiency close to 40% Increases with average beam power – Limit maximum dipole field PSI Cyclotron

PSI SINQ Cyclotron * Injection Energy 72 MeV * Extraction Energy 590 MeV * Extraction Momentum 1.2 Gev/c * Energy spread (FWHM) ca. 0.2 % * Beam Emittance ca. 2 pi mm x mrad * Beam Current 2.0 mA DC * Accelerator Frequency MHz * Time Between Pulses ns * Bunch Width ca. 0.3 ns * Extraction Losses ca % Achieved: 590 MeV, 2 mA, 1.2 MW Upgrade: 590 MeV, 3 mA, 1.8 MW Possible: 1000 MeV, 10 mA, 10 MW [M. Humbel (PSI)]

Cyclotron Example ~1000 tons ~3000 tons Cavity model

Intensity limitations (M.Craddock, 1998) Identified Issues: – Beam loss (0.01%/1kW ok, 0.1%/10 kW to a dump). OK – Space charge and extraction. Longitudinal space charge most important High RF or flat-top cavities for good extraction OK – R&D required for > 1 MW on windows. OK – Reliability > 95% (1). Redundancy in design. Not OK 15th International Conference on Cyclotrons and Their Applications, 1998 vol. TRI-PP pp. 1-4

Cyclotron types - more than one! PSI ‘Dream Machine’ (1 GeV) Separated-Orbit Cyclotron (see also Hexatron, VPAC, ‘Fresnel accelerator’ etc.) not yet demonstrated? F.M.Russel, NIM A23, 229 (1963)

VPACs vs. Fresnel Accelerator A.R. Tumanyan et al., Nuclear Instruments and Methods in Physics Research A 482 (2002) 1–11 - looks very similar to what Bruno and I were chatting about recently…

Cyclotrons and FFAGs TRIUMF

Proton FFAGs – KURRI see EPAC’08 paper for progress. 10 nA, not 10 mA! Only 2 proton FFAGs have been constructed

RACCAM Design Study S. Antoine et al., Nuclear Instruments and Methods in Physics Research A 602 (2009) 293–305

Proton FFAGs Renewed interest in Fixed Field Alternate Gradient (FFAG) accelerators [F. Meot (Saclay)] Advantages: High repetition rate (~ kHz), final energy > 1 GeV Successful demonstration of scaling (fixed tune) FFAG [Y. Mori/S. Machida (KEK)] Non-scaling designs with small tune variation are being developed Example: Idea of a 10 MW proton driver: [A. G. Ruggiero (BNL)] 1 GeV, 10 mA, 10 MW, 1 kHz After FFAG: DF: ~ 3 x 10 -4, I peak ~ 30 A Issues: High rf power, fast frequency tuning, complicated magnetic field profile Target 200-MeV DTL 1.0-GeV FFAG H – Stripping Foil DFF SS gg x, cm 200 MeV 1.0 GeV s, m

Proton FFAG Designs Scaling designs – Broadly used for lower energy, higher power – Tune constant with energy – Large magnets – Recent demonstration (KURRI) at low current Non-scaling designs – Must be used at high enough energy – Non-constant tune – requires proof-of-principle (EMMA) – Plenty of designs, no experience Typical scaling designs, A. Ruggiero (Cyclotrons 07)

NS-FFAG Issues Dynamics – True for any NS-FFAG – Fast resonance crossing could cause transverse instabilities, but hopefully won’t – Need a prototype Protons + fixed field + tune variation -> RF frequency sweep – Single bunch per frequency sweep; back to RCS rep. rates! – Similar RF problems to an RCS – Might be possible to overcome that with multiple frequency cavities, or clever longitudinal dynamics – Under exploration (2 x PhD students)

EMMA Prototype (2009) R. Edgecock et al., EPAC’08

Rapid Cycling Synchrotrons, e.g. BNL Design

RAL Proton Driver – RCS at High Energy RCS – Fast cycling magnets – Swept RF – ‘Simple’ dynamically NS-FFAG – DC magnets – Swept RF – Complex dynamics 1.2 GeV, 50 Hz Booster Synchrotrons Achromat for Collimation 2 Bunches of 2.5 x protons in each ring Stacked 5 GeV, 25 Hz Main Synchrotron 4 Bunches of 2.5 x protons in each ring 180 MeV H - Linac

MYRRHA/XADS

MYRRHA/XADS Linac

MYRRHA H.A. Abderahhimet al., Nuclear Instruments and Methods in Physics Research A 463 (2001) 487 Started with a 350 MeV IBA cyclotron, now using a linac…

MYRRHA: Linac vs. Cyclotron IAEA Technical Meeting (38th annual Meeting) to "Review of National Programmes on Fast Reactors & Accelerator Driven Systems (ADS)" Technical Working Group on Fast Reactors (TWG-FR)

MYRRHA linac Taken from ‘From MYRRHA Towards XT-ADS, November 23, 2004, Mol, Belgium’

Superconducting Proton Linac Several proposals, but no existing facility Issues: CW front end (RFQ, DTL), operating efficiency of SC cavities/rf system Low Energy Demonstration Accelerator (LEDA): 6.7 MeV, 100 mA CW (0.7 MW) Successful demonstration of CW front-end Bench-marking of halo simulation codes High Intensity Proton Injector (IPHI, CEA) [R. Ferdinand (CEA)] 3.0 MeV, 100 mA CW (0.3 MW) First beam in 2006, to be used for SPL (CERN) International Fusion Materials Irradiation Facility (IFMIF): 2 x 125 mA D +, 5 MeV (RFQ), 40 MeV (DTL) (2 x 0.6 MW, 2 x 5 MW) Start 2009 (?) Project-X? (FERMILAB):

SC Linacs Super-conducting Linac designs: APT Linac, ESS (Long Pulse) ESS – Long Pulse Reference Design: 1334 MeV, 3.7 mA (3.3% DF), 5 MW Beam / AC power (LP): 24% (NC 19%, SC 28%)

SNS Proton Linac (Existing) S. Henderson, EPAC’08 Availability ~80% Beam loss an issue SC Cavities give operational flexibility (which should raise availability) and increase aperture (gives smaller beam loss)

(My) Conclusion If we had to make a choice today for a test facility, it would be a 390 MeV proton cyclotron If we have some time, we should look at NS-FFAG/RCS/Linac options, and decide which is best. Can’t choose yet between circles and lines for a full facility.