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Cyclotron K-Value: → K Is the Kinetic Energy Reach for Protons from Bending Strength in Non-Relativistic Approximation

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Cyclotron K-Value: → K Is the Kinetic Energy Reach for Protons from Bending Strength in Non-Relativistic Approximation 1 Cyclotrons - Outline • cyclotron concepts history of the cyclotron, basic concepts and scalings, focusing, classification of cyclotron-like accelerators • medical cyclotrons requirements for medical applications, cyclotron vs. synchrotron, present research: moving organs, contour scanning, cost/size optimization; examples • cyclotrons for research high intensity, varying ions, injection/extraction challenge, existing large cyclotrons, new developments • summary development routes, Pro’s and Con’s of cyclotrons M.Seidel, Cyclotrons - 2 The Classical Cyclotron two capacitive electrodes „Dees“, two gaps per turn internal ion source homogenous B field constant revolution time (for low energy, 훾≈1) powerful concept: simplicity, compactness continuous injection/extraction multiple usage of accelerating voltage M.Seidel, Cyclotrons - 3 some History … first cyclotron: 1931, Berkeley Lawrence & Livingston, 1kV gap-voltage 80keV Protons 27inch Zyklotron Ernest Lawrence, Nobel Prize 1939 "for the invention and development of the cyclotron and for results obtained with it, especially with regard to artificial radioactive elements" John Lawrence (center), 1940’ies first medical applications: treating patients with neutrons generated in the 60inch cyclotron M.Seidel, Cyclotrons - 4 classical cyclotron - isochronicity and scalings continuous acceleration revolution time should stay constant, though Ek, R vary magnetic rigidity: orbit radius from isochronicity: deduced scaling of B: thus, to keep the isochronous condition, B must be raised in proportion to (R) the field index describes the (normalized) radial slope of the bending field, is negative if isochronous! contradicting findings! from equation of motion, betatron tunes in cyclotron: M.Seidel, Cyclotrons - 5 sector cyclotrons – solution to the focusing problem hill / valley variation of magnetic field (Thomas focusing) makes it possible to design cyclotrons for higher energies Flutter factor: with flutter and additional spiral angle [illustration of focusing at edges] of bending field: strong term e.g.: =27: 2tan2 = 1.0 M.Seidel, Cyclotrons - 6 in a cyclotron two conditions must be met 1.) resonant acceleration 2.) vertical focusing - limit energy / ignore problem [classical cyclotron] - negative field slope [classical/synchro cyclotron] - frequency is varied, slope neg [synchro- cyclotron] - avg. field slope positive - focusing by flutter, spiral angle [isochronous cyclotron] [AVF/sector cyclotron] M.Seidel, Cyclotrons - 7 Azimuthally Varying Field vs. Separated Sector Cyclotrons PSI/Varian comet: 250MeV sc.cyclotron medical comet: PSI/Varian PSI PSI Ring cyclotron • AVF = single pole with shaping • modular layout, larger cyclotrons possible, • often spiral poles used sector magnets, box resonators, stronger • internal source possible focusing, injection/extraction in straight • D-type RF electrodes, rel. low energy gain sections • compact, cost effective • external injection required, i.e. pre- • depicted Varian cyclotron: 80% extraction accelerator efficiency; not suited for high power • box-resonators (high voltage gain) • high extraction efficiency possible: e.g. PSI: 99.98% = (1 - 2·10-4) M.Seidel, Cyclotrons - 8 energy reach - K value • cyclotron K-value: → K is the kinetic energy reach for protons from bending strength in non-relativistic approximation: → K can be used to rescale the energy reach of protons to other charge-to-mass ratios: → K in [MeV] is often used for naming cyclotrons examples: K-130 cyclotron / Jyväskylä (Finland) cyclone C230 / IBA (Belgium) M.Seidel, Cyclotrons - 9 cyclotron radius increment nonrelativistic: cyclotron language relativistic: (theoretical number) radius increment per turn decreases with increasing radius → extraction becomes more and more difficult at higher energies M.Seidel, Cyclotrons - 10 cyclotrons work at intermediate A.Einstein relativistic energies 1879-1955 푑훽 1 푑퐸푘 푑퐸 훾 + 1 푑푝 = 푘 = 훽 훾 훾 + 1 퐸푘 energy 퐸푘 훾 푝 퐸 = 훾퐸0 kinetic energy: 퐸푘= 훾 − 1 퐸0 velocity momentum PSI cyclotron for protons 푣 = 훽푐 푝 = 훽훾푚0푐 Ek p [MeV] [MeV/c] revolution time: bending strength: 푑푝 2 푑훽 = 훾 590 1.63 0.79 1207 2휋푅 푝 훽 푚0푐 휏 = 퐵푅 = 훽훾 훽푐 푒 M.Seidel, Cyclotrons - 11 classification of cyclotron like accelerators classical cyclotron [B() = const] Thomas cyclotron [Azimuthally Varying Field, AVF concept – harmonic pole shaping, electron model, Richardson et al (1950), e.g. B() b+cos(3), one pol] courtesy of Lawrence Berkeley National Laboratory separated sector Fixed Focus Alternating synchro-cyclotron cyclotron [varying RF frequency] Gradient Accelerator FFAG [separated magnets, resonators] [varying RF, strong focusing] high intensity high energy compact machine M.Seidel, Cyclotrons - 12 • next: medical cyclotrons – particle therapy; scanning technology – new developments – isotope production M.Seidel, Cyclotrons - 13 cancer treatment: X-rays vs. Protons Xröntgenstraling-rays tumourtumor Dose Dosis DiepteDepth inin tissueweefsel (cm) (cm) [M.Schippers] M.Seidel, Cyclotrons - 14 Why Cyclotrons for Cancer Dee 4 Treatment? Dee 1 H- in favour of cyclotrons: chimney • 250MeV: suited energy for cyclotrons H2+ • cost effective and compact; single s.c. magnet possible • continuous beam; lots of Dee 3 slit Dee 2 intensity reserve, e.g. repainting, moving organs • precise and fast intensity modulation at low energy possible chimney = ion source deflector electrode for intensity regulation M.Seidel, Cyclotrons - 15 However, Cyclotron needs degrader : • cyclotron has fixed energy; need degrader for energies down to 70MeV • collimation after degrader to keep emittance lose intensity with degrader degrader: (carbon wedges in vacuum) and laminated beam line magnets for fast energy changes < 80 ms / step M.Seidel, Cyclotrons - 16 PSI‘s Proscan Facility s.c. cyclotron Comet Gantry 3 0.8m extraction under construction radius OPTIS eye melanoma Gantry 1 treatment, 70MeV range shifter Gantry 2 fast scanning, innovative M.Seidel, Cyclotrons - 17 250 MeV proton cyclotron (ACCEL/Varian) ACCEL Closed He system 4 x 1.5 W @4K 300 kW Proton source 90 tons 4 RF-cavities ≈100 kV on 4 Dees superconducting coils 1.4 m => 2.4 - 3.8 T 3.4 m M.Seidel, Cyclotrons - 18 PSI developments: different scanning options [D.Meer] a) Spot scanning as the default mode b) Lines scanning for max. repainting c) Contours scanning for optimizing repainting and lateral fall-off (?) • Vertical deflector plate for intensity modulation – Fast intensity control on time scale of 100 ms • Requires flexible control system – control of fast actuators (sweepers, deflector plate) with 100 kHz – tabulated dose delivery based on state-of-the-art electronics (FPGA) – example: Painting shaped energy iso-layer M.Seidel, Cyclotrons - 19 new development by IBA: compact treatment facility using the high field synchro-cyclotron Beam analysis 2D - PBS SC 5.6T 230 MeV synchro-cyclotron Degrader 20x25 cm2 field • required area: 24x13.5m2 (is small) • 2-dim pencil beam scanning M.Seidel, Cyclotrons - 20 W.Kleeven, IBA S2C2 overview General system layout and parameters Synchro-Cyclotron field decreasing with radius ! RF-system W.Kleeven, IBA layout Adjustable stub Liner RF pick-up Dee Oscillator Line through Pyrometer cryostat Rotco Vacuum Servo motor feedthrough Turbo pump RF-system W.Kleeven, IBA Rotco=> Coaxially mounted with 8-fold symmetry Innovative/patented design: Latest stator blade excellent mechanical stability and optimization good pulse reproducibility Stator: 8 blades with a carefully designed profile to have the desired df/dt curve. Rotor: wheel with 2x8 electrodes turning at 7500rpm (1 kHz pulse) measured RF-frequency during a pulse 95 90 85 80 75 frequency (MHz) frequency - 70 RF 65 60 0 200 400 600 800 1000 time (msec) Carbon Ions vs. Protons Pro Carbon: • higher dE/dx produces more correlated damage in DNA of cancer cells; hence more effective; potentially less fractions • smaller rms scattering angles within body tissue allows better focusing of beam in target volume Contra Carbon: • significantly higher bending strength required accelerator, beam transport and Gantry are more expensive • tail of dose can reach to higher depth since C- Heidelberg Gantry for Carbon, nucleus could be split, which is not the case for p 670 tons 250 MeV Protons: p vs. C 450 MeV/nucleon Carbon: for same depth M.Seidel, Cyclotrons - 24 Cyclotron for carbon ions Archade project, Caen (Fr) IBA Carbon ions protons 700 tons SC coils Ø 7 m Int. Conf. Cyclotron and appl, Tokyo 2004 M.Seidel, Cyclotrons - 25 compact cyclotrons for Isotope production vertical setup (!) M.Seidel, Cyclotrons - 26 next: High Intensity Cyclotrons – PSI facility; technological aspects; beam loss – application for ADS systems – ions and RIB’s figure: person inside resonator M.Seidel, Cyclotrons - 27 High Intensity Beams – Applications • neutron production for neutron sources and ADS; e.g. 800MeV • muon production in targets via Pi-production (PSI, ISIS, TRIUMF, BNL?) • neutrino production: Daedalus study n vs p-energy: losses: 100Watt acceptable optimum 1.2GeV -2 -1 ADS: 10 …10 trips per day(!) A. Letourneau et al. / Nucl. Instr. and Meth. in Phys. Res. B 170 (2000) 299±322 M.Seidel, Cyclotrons - 28 Example: PSI Facility Beam: 1.3MW, Grid: 10MW Muon production targets Ring Cyclotron 590 MeV loss 10-4 Power transfer through SINQ 4 amplifier chains spallation 4 resonators 50MHz source 2.2 mA /1.3 MW 50MHz resonator proton therapie center dimensions: [250MeV sc. cyclotron] 120 x 220m2 M.Seidel, Cyclotrons - 29 PSI Ring Cyclotron 8 Sector Magnets:
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