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Potential of Cyclotrons. Werner Joho, PSI FFAG 2007, Grenoble 12.april 2007. State of the Art Accelerator Facilities. Ringcyclotron 590 MeV protons. superconducting cyclotron. 1.2 MW average Beam Power. Radiation Therapy with Spot Scanning and rotating Gantry. - PowerPoint PPT Presentation
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W.Joho 2007
Potential of Cyclotrons Potential of Cyclotrons
Werner Joho, PSI
FFAG 2007, Grenoble 12.april 2007
W.Joho 2007
State of the Art Accelerator FacilitiesState of the Art Accelerator Facilities
Ringcyclotron 590 MeV protonsRingcyclotron 590 MeV protons
1.2 MW average Beam Power
high Intensity Muon Beams 5•108 /s , 108 /s
Spallation Neutron Source 1014 n/s
Radiation Therapywith Spot Scanning and rotating Gantry
Swiss Light Source SLS(2.4 GeV Electron Storage Ring)
Swiss Light Source SLS(2.4 GeV Electron Storage Ring)
• extremely stable photon beams ( < 0.5 m)
• „top-up“ and „fast orbit feedback“ (FOFB)
superconducting cyclotron
superconducting cyclotron
W.Joho 2007
PSI East
PSI West
Aare
psi forum
Auditorium
SLS
Neutron Source
Aerial View
W.Joho 2007
The first Cyclotron 1931
The first Cyclotron 1931
E.O.Lawrence,
M.S.Livingston
Berkeley, California
4 inch diameter
1 kV on the Dee
80 keV Protons
W.Joho 2007
43 years later (1974)
43 years later (1974)
Ring Cyclotron
590 MeV Protons
15 m Diameter
Hans Willax,
Jean Paul Blaser,
Villigen, Switzerland
W.Joho 2007
Comet CyclotronComet Cyclotron
Radiation Therapy with
250 MeV Protons
Cyclotron:
superconducting Magnet, 3m Ø
Collaboration: ACCEL & PSI
W.Joho 2007
Comet Cyclotron, 250 MeV Protons
Comet Cyclotron, 250 MeV Protons
superconducting Magnet
with 4 Sectors
The spiral structure
is responsible for the
vertical beam focusing
0.5 m
W.Joho 2007
Proton Therapy with PROSCAN(3D-spot scanning)
Proton Therapy with PROSCAN(3D-spot scanning)
SC-CYCLOTRON
DEGRADER=> Rangeshifter
(2-30cm)
sweeper 1Does Modulation
Patient-table
sweeper 2
Proton Beam250 MeV
Dipole
Gantry
W.Joho 2007
Cyclotrons
Cyclotrons
Synchro-
cyclotron
Isochronous Cyclotron
classicalCyclotron
CW-beamsingle polewith sectors
CW-beam
pulsed beam
Ring Cyclotron
non relativisticenergy limit
single pole
FFAG with sectors
W.Joho 2007
Accelerator Facilities with 4 Cyclotrons
Accelerator Facilities with 4 Cyclotrons
Injector 1:
Nuclear Physics + Eye
Tumours
Injector 2:
Injection + Isotopes for
Hospitals
Ring Cyclotron:
Muons, Pions, Neutrons,
Proton Therapy
superconducting Cyclotron:
Proton Therapy
W.Joho 2007
Injector IIInjector II
Injection Line
870 keV
Extraction Line
72 MeV Protons
(after 100 turns)
Resonator
50 MHz
W.Joho 2007
Recipe for high Intensity
Recipe for high Intensity
continuos beam (cw)
very low extraction losses
=> separated turns with
large turn separation dR
at extraction
=> high energy gain per turn,
powerful RF-system with
high voltage cavities
dR ~ Radius R
=> large machine radius !!
the last 5 turns in the Injector II
dR
W.Joho 2007
RingcyclotronRingcyclotron
590 MeV Protons
1.2 MW Beam Power
(world record!)
8 Magnet à 250 Tons
4 Cavities à 700 kV
(upgrade to 1MV)
Extraction ≈ 99.97 %
W.Joho 2007
RF CavityRF CavityRing Cyclotron 590 MeV , 50.7 MHz
original version:
aluminum , V=730 kV
300 kW power loss
216 turns
at 2 mA: 300 kW power/cavity
delivered to the beam
new cavity:
copper , V = 1 MV
500 kW power loss
160 turns , current limit > 3 mA ?
W.Joho 2007
Ring Cyclotron
Ring Cyclotron
y [mm]
x [mm]
Contour lines of the
magnetic field
scaling of average field:
B0(R) ~ γ
Increase from 72-590 MeV: 55%
2 T
1.5 T
W.Joho 2007
Orbits in Ring Cyclotron
Orbits in Ring Cyclotron
Extraction
Septum
RF Cavity
Magnet
Sector
6 Orbits plotted at
equidistant energies:
75, 177, 279, 381, 483, 585 MeV
(R ~ β)
W.Joho 2007
how to scare young
students!!
how to scare young
students!!
better approach to get
focusing frequencies:
1. simple
approximations
2. numerical calculations Qr
2 ≈ +k
Qz2 ≈ -k +F (1+2tan2
)
(Al Garren 1962)
W.Joho 2007
Flattop Voltage gives minimum energy
spread
Flattop Voltage gives minimum energy
spread
W.Joho 2007
Ring Cyclotron (1980) turns 26-315, 100-590 MeV
Ring Cyclotron (1980) turns 26-315, 100-590 MeV
W.Joho 2007
Advantages of Ring Cyclotron (Hans Willax 1963)
Advantages of Ring Cyclotron (Hans Willax 1963)
magnetic field and RF system are decoupled
many cavities (incl. flattop!)
with high voltage
strong vertical focusing
small magnet gap
low power consumption
total magnet weight as low as
for a compact warm magnet
straight sections
easy construction of injection and extraction elements(no kickers !)
lots of space for diagnostic and correction elements
fast crossing of resonances
good turn separation, low extraction losses
high intensity
penalty: requires injector!
W.Joho 2007
Properties of Cyclotrons
Properties of Cyclotrons
=> high Intensity (few mA)
=> polarized Ions (few A)
Coincidence Experiments with
high Event Rates
continuos Beam allows
easy Tuning of
Accelerator
in all 6 Dimensions
transv.: 1 mm mrad (norm.)
E/E ≈ 10-3
t ≈ 0.3 ns
Pulse Selection at low Energy gives flexible microscopic Time Structure for Time of Flight Experiments
all Ions from p to U
Energies:
p: up to 600 MeV => limit ≈ 10 GeV ?
Ions: up to 500 MeV/n
versatile
CW-Beams
excellent Beam Quality
W.Joho 2007
Current Limit in
Ring Cyclotron
Current Limit in
Ring Cyclotron
Longitudinal space charge forces
increase the energy spread
=> higher extraction losses
=> limit on beam current
Remedy:
higher voltage V on the RF cavities
=> lower turn number n (V·n = const.)
There are 3 effects, each giving a factor V(~1/n):
1) beam charge density ~ n
2) total path length in the cyclotron ~ n
3) turn separation ~ V
W.Joho, 9th Int. Cyclotron conference CAEN (1981)
current limit ~ V3 !
2000
W.Joho 2007
Cyclotrons are still attractive !
Cyclotrons are still attractive !
Commercial Cyclotrons for
Radiation Therapy and Isotope Production
Acceleration of Radioactive Beams
Injectors for Ion Storage Rings
Intense Neutron Sources, replacing Reactors
Energy Amplifier Concept (Carlo Rubbia)
Transmutation of Nuclear Waste
W.Joho 2007
„slow“ Neutrons for Material Research
„slow“ Neutrons for Material Research
• Production of fast Neutrons
• slowing down in Moderator
1. Fission of Uranium (U235)
in a Reactor
2. Spallation of heavy Nuclei
(e.g. lead) by Bombardment with
Protons from an Accelerator
=> safe and fast turning off !
W.Joho 2007
Spallation Neutrons
Spallation Neutrons
W.Joho 2007
Energy Amplifier Concept (C.Rubbia)
Energy Amplifier Concept (C.Rubbia)
Example for a test facility:
the 600 MeV PSI Cyclotron
operating at 3 mA (1.8 MW)
could produce 100 MWth from a
reactor running with a
criticality factor k=0.95
For a real power plant with
1 Gwel one needs an accelerator
with 50 mA at 1 GeV => Linac
W.Joho 2007
Proton TherapyProton Therapy
Irradiation of Tumour
from different
Directions with Gantry
minimal Dose at
Surface
W.Joho 2007
Spotscanning (E.Pedroni)Spotscanning (E.Pedroni)
still world wide the only Gantry with Proton Scanning !
X Sweepermagnet (fast) 5 ms/step
Y Range-shifter (moderate speed) 30 ms
Z Patient Table (slow) 10 mm/s
Tim Spot-Dosis Monitor + Kicker 100 us
Scanning Elements :
– Pencil Beam: 7 mm in Air
– Volume Scanning on a 5 mm Grid: 10’000 Application Points per Liter
W.Joho 2007
Brain TumourBrain Tumour
Irradiation with
Protons by
Spot-Scanning
(E.Pedroni, PSI)
W.Joho 2007
ReferencesReferences
More information on the PSI Accelerator Facilities can be found in:
www.psi.ch
Some foils from talks by the author are found in:
http://abe.web.psi.ch/accelerators/vortraegeWernerJoho/
vortraegeWernerJoho.php
In the paper “Fun with Formulas” there is e.g. a cute approximation
for the end fields of a magnet with a binomial formula.