Interreg IIIA Symposium

1
Synchrotrons Designs and SolutionsH. Schönauer

• Particle Accelerators for Hadron Therapy
• Synchrotron Varieties
• Design philosophies
• Periodic or composite lattice
• Working point
• Space Charge Tune shift
• Comments and Suggestions for Proton operation
• Aspect ratio
• Round or Flat Beam
• Matching to HEBT
• Properties of the Slow-Extraction beam
• Proposed machines

2
Particle Accelerators in Hadron Therapy
The Future F F A G ?
3
Classical Argumentations FFAG vs. Cyclotron
FFAG Accelerator for Proton Therapy, S. Machida
and Y. Mori, KEK (2004)

• Cyclotron
• Pros
• Continuous beam and high average current.
• Easy operation
• Cons
• Low peak current
• No knobs to change extraction energy
• Big iron core

NO Injector required Constant RF frequency
? IBA 235 MeV p Cyclotron 240 tons ? IBA 400
MeV/u 12C Cyclotron 700 tons
Extraction loss -gt handling of radioactive septum
4
Classical Argumentations FFAG vs. Synchrotron
FFAG Accelerator for Proton Therapy, S. Machida
and Y. Mori, KEK (2004)

• Synchrotron
• Pros
• Variable energy
• High peak current
• Cons
• Low repetition rate due to magnet ramping
• Skilled operation is necessary
• Relatively higher cost
• Uneven emittances/phase space distributions

?
?
5
Characteristics of Hadron Accelerators
Despite the compactness of the cyclotron, the
Synchrotron is frequently used in proton therapy
facilities. Its attraction is that the energy of
the extracted beam can easily be varied from
pulse to pulse. However, the slow extracted beam
is delicate to set up and subject to fluctuations
and ripples, stemming from minute harmonic
components in the power converters for the main
quadrupoles and other magnets. Moreover, the
radial distribution is about rectangular and far
from Gaussian - matching to a gantry is tricky
and controversial. To avoid the problems of slow
extraction (?), rapid cycling medical
synchrotrons (RCMS) with fast extraction have
been proposed S. Peggs. Originally a repetition
frequency of 30 Hz was proposed but 60 Hz
appears just feasible. Compared to an RMCS the
FFAG offers substantially faster rep rates !

• A radically different approach was recently
  proposed by G.H. Rees
• Continuous foil extraction during acceleration of
  a H- Beam in a 10 Hz Synchrotron
• Intensity control by Radial steering very fast!
• Beam transport and Gantry need to be rapidly
  cycling or FFAG!

6
Synchrotron Varieties

• Historical the Bevatron
• Loma Linda UMC (p)
• Hitachi Tsukuba, Anderson (p)
• Mitsubishi
• HIMAC, PATRO
• Compact (project)
• GSI-HIT
• PIMMS-CNAO
• Siemens / Danfysik
• RCMS (p, project)

7
The Bevatron (Historical, 1st Ion Therapy)
Designed for 6 GeV protons, Weak focusing
machine, Mean circumference 120m
8
Loma Linda University Medical Centre1st Proton
Therapy Synchrotron
9
Loma Linda University Medical Centre1st Proton
Therapy Synchrotron

• C20.053m
• Small Weak-Focusing Machine Zero Gradient
  Synchrotron with Edge Focusing ?x0.59, ?y1.31
• Low Injection Energy (2 MeV)
• Edge Focusing, producing a large horizontal
  Dispersion of 9 m.

• Good field region (hor.) ?2.5 cm
• dp/p of RFQ beam 0.7 FWHH In conjunction with
  the unusually high Dx 9 m it is obvious that a
  non-negligible fraction of the (single-turn)
  injected beam will exceed the good field aperture
  and be lost.

10
LLUMC
11
HIMAC Synchrotrons 100-800 MeV/u 42 m diameter
12
HITACHI PROTON Synchrotron (Tsukuba Univ.)
Injection Energy (MeV) Extraction
Energy(MeV) Superperiodicity Tune Qx Qy Bending
Magnet Deflection Angle(deg) Curvature
Radius(m) Max. Field Strength (T) Twiss
Parameters ?x, max ( m) ?y, max (m) D max (
m) Momentum Compaction Factor Transition Gamma
7 70-270 2 1.72 1.74 60 1.4 1.8 1 2 11 2.3 0.36
1.67
13
PATRO Accelerator (Mitsubishi) at HYOGO
Particles Proton, Helium and Carbon Energy
Range 70 - 230 MeV/u for p, He 70 - 320 MeV/u
for Carbon Circumference 93.6 m Beam Intensity
7.3x1010 pps for p 1.8x1010 pps for
He 1.2x109 pps for Carbon (3.8x109 ppp) Dose
Rate 5 GyE/min Beam Range 40 - 300 mm for p
and He 13 - 200 mm for Carbon Field homogeneity
2 (over treatment field) Field size
15cmx15cm for ports A, B 10cmf for port
C 15cmf for gantry ports G1, 2 Displacement of
beam 2mm (from isocenter) Spill length
400ms Maximum repetition 0.5 Hz for He and
Carbon 1 Hz for proton
Separatrices described by unstable particles
with Dp/p in the range 0 to -0.0011 (i.e. the
spread in the beam being extracted)
Separatrices described by unstable particles
with Dp/p in the range 0 to -0.0011 (i.e. the
spread in the beam being extracted)
All separatrices cross the septum wires at the
same angle. This known as the Hardt
Condition and ensures minimum losses on the wires
All separatrices cross the septum wires at the
same angle. This known as the Hardt
Condition and ensures minimum losses on the wires
Stable triangle' for particles that are
off-resonance by Dp/p -0.0011
Stable triangle' for particles that are
off-resonance by Dp/p -0.0011
Disperison trajectory for off-resonance
particles with Dp/p -0.0011
Disperison trajectory for off-resonance
particles with Dp/p -0.0011
Position of the wires of the electrostatic
septum at 35 mm
Position of the wires of the electrostatic
septum at 35 mm
Focal point of separatrices for particles that
are exactly on resonance Dp/p 0
Focal point of separatrices for particles that
are exactly on resonance Dp/p 0
Details of last tracking made for the
off-momentum separatrix tracking
Details of last tracking made for the
off-momentum separatrix tracking
14
Recent Ion Synchrotrons
GSI HIT
Danfysik
C 64.8m ?x , ?y rms 20 ?, 2 ? _at_ injection
C 65m
15
PIMMS CNAO Synchrotron

• Based on PIMMS, optimized by TERA (I)

• Protons 250 (1200) MeV
• C-ions 400 MeV/u
• Multi-turn injection (?10)
• Slow extraction horiz. (5/3)
• Spill time 1s to 10 s
• Extraction with a Betatron core inductive
  acceleration
• Orthogonal control of resonance and
  chromaticity
• ?x , ? v rms 6 (2.5) ?

16
Design Philosophies Periodic or Composite lattice
PIMMS 180deg arcs
Danfysik FODO
17
The Tuneshift Issue (for protons)

• G Form factor Transverse peak / average
  density - depends on the definition of the
  emittance !

18
TsukubaSynchrotronIntensity Gain by working
point shiftA. Molodojentsev et al.
Design Philosophies Choice of Working Point
Typical Working Area of most machines
19
Slow Extraction
Separatrices described by unstable particles
with Dp/p in the range 0 to -0.0011 (i.e. the
spread in the beam being extracted)
Separatrices described by unstable particles
with Dp/p in the range 0 to -0.0011 (i.e. the
spread in the beam being extracted)
All separatrices cross the septum wires at the
same angle. This known as the Hardt
Condition and ensures minimum losses on the wires
All separatrices cross the septum wires at the
same angle. This known as the Hardt
Condition and ensures minimum losses on the wires
Stable triangle' for particles that are
off-resonance by Dp/p -0.0011
Stable triangle' for particles that are
off-resonance by Dp/p -0.0011
Disperison trajectory for off-resonance
particles with Dp/p -0.0011
Disperison trajectory for off-resonance
particles with Dp/p -0.0011
Position of the wires of the electrostatic
septum at 35 mm
Position of the wires of the electrostatic
septum at 35 mm
Focal point of separatrices for particles that
are exactly on resonance Dp/p 0
Focal point of separatrices for particles that
are exactly on resonance Dp/p 0
20
Tracking Results of Slow Extraction Beam at the
Electrostatic Septum x - x Space and Projection
Horizontal phase space (left) of the extracted
beam at the entrance of electrostatic septum
centered on the extraction orbit and
corresponding horizontal profile (right). Usually
a beam ellispse is fitted around.
21
Characteristics of the Slow-Extracted Beamx -
dp/p, x- dp/p Space
Beam position (left) and divergence (right) as a
function of the momentum spread and linear
regression which gives Dx 0.487 and D?x 0.553.
22
Characteristics of the Slow-Extracted Beamx -
x space after subtraction of dispersion component
Horizontal phase space (left) of the extracted
beam at the entrance of electrostatic septum
after subtraction of the momentum dependent terms
and corresponding horizontal profile (right).
23
Fitting an Ellipse to x - x space after
substraction of dispersion component is not
really representative
Horizontal phase space of the extracted beam at
the entrance of electrostatic septum after
subtraction of the momentum dependent terms and
corresponding ellipse with ßx 16m, ax -2.5
and ?x 1.1p mm mrad.
24
PIMMS Approach The Bar of charge

• Due to the peculiarities of slow extraction, the
  phase space properties of the extracted beam are
  radically different in the two planes
• Vertical the usual elliptical footprint in phase
  space
• Horizontal a thin linear shape, the Bar of
  charge

Bar of charge
When the beam propagates down the line, the
phase space pattern rotates. The beam size in the
HOR plane is varied by controlling the phase
advance.
25
Some HEBT Layouts Standard (l.h.s.) vs.
PIMMS (r.h.s.)
Dispersion Matching Section
26
Effect of Dispersion Mismatch at a Gantry
Dispersion at Isocentre
Gantry _at_ 0 deg D 3.2m, D0.3
M. Pavlovic Study of admissible dispersion
at patient (1mm spot size) Dlt0.2 m,
Dlt0.8
90/270 deg D0.5m, Dy ?2.4m, D0.4, Dy ?
4.5
180 deg D 0.7m, D2.5
27
Alternative Approach The RCMS (p)
Rapid Cycling Medical Synchrotron the second
generation
Tandem pre- injector (AES)
Synchrotron accelerator
Gantries (ACCEL)
Horizontal eye fixed lines
Research room line
28
RCMS

• 7 250 MeV protons
• 30 Hz

29
Mitsubishi Compact Carbon / Proton Rings

• PROTONS C IONS
• Max. energy 200 MeV 300 MeV/u
• Inj. Energy 2 MeV 2 MeV/u
• Av. beam current (1 Hz) 20 nA 0.2 nA
• Nr. of particles/pulse 1.25 1011 1.25 109
• Circumference 11.9 m 16.5 m
• Av. radius 1.89 m 2.62 m
• Bending radius 0.72 m (3 T) 1.35 m (4 T)
• Tune (Hor/Ver) 2.25 / 1.25 2.25 / 1.25
• Max. dispersion 0.43 m 0.73 m
• Transition energy 2.29 GeV 2.08 GeV/u
• Lattice structure FODOFB FODOFB
• Long straight section 0.6 m x 8 0.6 m x 8
• Short straight section 0.1 m x 8 0.1 m x 8
• Superperiods 4 4

30
Mitsubishi Compact Carbon / Proton Rings
(EPAC 2002)
4 T (! ?)
31
Carbon Ion Synchrotrons (in scale)
PIMMS - CNAO
Danfysik
5 m
Mitsubishi Compact
GSI - HIT
HIMAC
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No Conclusion Needed Thank you for your
attention - and patience
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MedAustron Centre Layout
34
Choice of Extraction Method

• Energy of extracted beam changes
• Extraction position changes
• On-line corrections needed

• Energy of extracted beam constant
• Extraction position constant
• No on-line corrections