Part IV

Applications

Prototype of Cancer therapy machine with proton

• 150 MeV FFAG as a prototype• Commissioning to accelerate up to ~15 MeV is done.• Tune survey

Requirements

• Accurate positioning

– Irradiate a well defined 3-dimensional volume (and not outside.)

• Accurate dose

– Dose at each point should be controlled with accuracy of 1%.

Broad beam method (Conventional)

Final collimator

Bolus

Ridge filter

•Inevitable irradiation outside of the treatment field.

•Each patient needs his own shaped bolus.

Spot scanning method

•A small beam spot makes it possible to irradiate a well defined area.

•Non-uniform irradiation in the area is possible.

•Simultaneous dose measurement using supersonic waves.

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Supersonic wave detector Reconstruction of

irradiated volume in 3D space.

Treatment volume

Pulsed beam produces pulsed supersonic wave from irradiated position

Experiment (green)

Calculation (red)P

ressure of sound

Detection of supersonic waves induced proton beam pulse

Disadvantage of spot scanning

•Sensitive to respiratory motion•Organ motion during scanning should be suppressed.•Beam irradiation time should be shortened much less than respiratory motion.

•Intensity of each pulsed beam should be accurately controlled.

Dream machine

• Small spot beam with variable extraction energy (pulse by pulse).– A beam is delivered to localized volume (no other places.)

• Beam intensity is well controlled (pulse by pulse).– Accurate dose distribution.

• High intensity (per pulse) pulsed beam.– Short irradiation time compared to respiratory motion.

• Pulsed beam with very high repetition frequency– Simultaneous dose measurement using supersonic waves.

• Small size, low cost, and easy operation.

FFAG as a medical accelerator

• Spot scanning with 1kHz or more repetition rate.

• Variable energy extraction, pulse by pulse.

• 1% level of does control in a pulse using beam chopper after ion source.

• High peak as well as high average current is available due to very rapid cycling and alternating gradient (strong) focusing.

• Small size, low cost, and easy operation.

Injector (Cyclotron)

RF system

Extraction beam line

The system for

Spot scanning

5m

150MeV FFAG - Overview

Commissioning at East-Experimental hall of KEK-PS

Schematic view of 150MeV FFAG

Parameters

Design of the magnet pole

Magnetic field in the center of the sector BL

•Gap is not exactly rk in low momentum region.•Rogowski like patch is attached on focusing magnet.•BL is adjusted instead of local B().

with patch

w/o patch

Correction of magnet• The design of the edge of the F-sector pole

• The final design of the poles

with extension

w/o extension

BL-F/D ratio vs. radius

75.75400

21 ⎟⎠

⎞⎜⎝

⎛=r

halfgap

32.95400

20 ⎟⎠

⎞⎜⎝

⎛=r

halfgap

57.94900

9.39555.11

+⎟⎠

⎞⎜⎝

⎛=r

halfgap

Focusing sector

Defocusing sector

)49004500( Å`=r

)54004900( Å`=r

Unit : mm

A comparison of F-sector magnetic field

on the medium plane

excursion

Before and after correction

Tune excursion is reduced after correction.

before after

Betatron tunes

• Betatron tunes by a beam simulation with final design of the magnet.

Betatron tunes

vs. mean radius

integer resonance

half integer resonance

third resonance

Tune diagram

Return Yoke Free Magnet

• “Return Yoke Free Magnet ” The return yoke of Focusing sector is removed.

F Sector

D Sector

Shunt

ΦF: Magnetic field in F Sector

ΦD: Magnetic field in D Sector

ΦS: Magnetic field in Shunt Yoke

F coil D coil

•Space for the extraction

150 MeV FFAG - Return Yoke Free Magnet

150 MeV FFAG magnet, the view from the center of the ring.

Measurements of magnetic field.

-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.02.53.0

-120 -100 -80 -60 -40 -20 0 20X (cm)

É¢B/BÅ@(Åì)

Discrepancy (ΔB/B)

Measurements of magnetic field with hole probe.

The discrepancy between any two magnets is 0.3% at most. The alignment error of hole probe explained that discrepancy.

Y=-35~+45cm

5cm step

-15000

-10000

-5000

0

5000

10000

15000

20000

-120 -100 -80 -60 -40 -20 0 20

X (cm)

Bz (G

auss

)

Magnetic Field (Bz)

X

Y

D F D

Defocus

sector

Focus

sector

Defocus

sector

Focus sector

Magnet center

Chamber

2m

1.2m

alignment

Injector cyclotron and beam transport

Beam is circulating on April 25, 2003.

Beam position in first 3 turns

Without (left) and with (right) injection bump

ES

MS

Commissioning with SAD

• demonstration

Circulating beam and its tune

• BPM raw data and its frequency

Tune of design and measurement

calculationcalculation

Effects of neighboring components

• Fe next to magnets distorts

closed orbit.

Tune shift by COD

• Tune is a function

of COD.

acceleration

Goal of study

Prototype machine (150MeV) is under commissioning.

• MA based RF cavity

• Yoke-free magnet

• Demonstration of 3D spot scanning

PRISM phase rotator

• To study muon rare decay, mono chromatic muons are necessary.• Secondary particles produced by intense protons have large momentum

spread.– Phase rotation to convert large dp/p and small dt to small dp/p and large dt.– 5 turns in FFAG makes 1/4 synchrotron oscillation.

• PRISM specifications– Number of sector 8 (or 10)– Radius 5 m– Triplet sector– Acceptance 10,000 pi mm-mrad

Physics goal of PRISM project

-> e conversion in Muonic Atom

Phase rotation

PRISM layout

Simulation study with GEANT3.21

Phase rotation with two RF waveform

Momentum compression projected in horizontal plane

PRISM issues

• Large aperture RF core

• Large aperture kicker

• High repetition

FFAG for ADS

• Feasibility study of ADSR

– Five year program from 2002 to 2006

• Subjects

– Accelerator technology

• Variable energy FFAG

– Reactor technology

• Basic experiments for energy dependence of the reactor physics

• Hosted by Kyoto University Research Reactor Institute (KURRI)

What is ADSR?

• Accelerator driven Sub-critical Reactor

• Chain reaction is controlled by beam.

acceleratorSub-critical reactor

Target for generatingneutrons

Accelerator driven sub-critical reactor (ADSR)

• Basic study of accelerator driven system.• 3 stage FFAG

– 2.5 MeV spiral (ion beta) FFAG with induction cores– 25 MeV radial (booster) FFAG with RF and flat gap– 150 MeV radial (main) FFAG with RF and tapered gap

• Variable output energy become possible by– Variable k value at booster FFAG

• Orbit excursion should be the same to locate the same injection and extraction radius.

• Momentum ratio at main FFAG is constant. Magnetic strength is variable.

• Upgrade to 1 GeV system is considered.

Layout of ADSR FFAG

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are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

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QuickTime™ and aTIFF (Uncompressed) decompressor

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Neutrino factory

• Accelerate muons to 20 - 50 GeV/c• Initial momentum is 0.3 - 1 GeV/c• 3 or 4 FFAG cascade

– 0.3 - 1 GeV/c (0.3 - 1 GeV/c with nuon cooling)– 1 - 3 GeV/c or 1 - 4.5 GeV/c– 3 - 10 GeV/c 4.5 - 20 GeV/c– 10 - 20 GeV/c

• JPARC 50 GeV Main Ring is a proton driver.

Neutrino factory with JPARC proton driver

Acceleration of muons

• No time to modulate RF frequency.• 1 MV/m (ave.) RF voltage gives large longitudinal acceptance.• From 10 to 20 GeV/c within 12 turns.

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Issues

• Kicker

• Non scaling FFAG