Advanced Accelerator Design/Development Proton Accelerator Research and Development at RAL Shinji Machida ASTeC/STFC/RAL 24 March 2011.

Advanced Accelerator Design/Development

Proton Accelerator Research and Development at RALShinji Machida

ASTeC/STFC/RAL24 March 2011

Advanced Accelerator of protonswhat is it?

• = Fixed Field Alternating Gradient (FFAG) accelerator in today’s talk.

• Not “advanced” in terms of fundamental principle.• But “advanced” from practical view point

– easy construction and operation– Potential to get high beam power– possibly cheaper

FFAG acceleratorswhat is it? (1 slide)

• Alternating Gradient focusing accelerator without ramping magnet.

• Momentum independent bending and focusing is provided in space not in time.

FFAG accelerators“advanced”

• DC magnets– Free from eddy current issue.– No expensive AC resonant power supply.– No tracking between dipole and quadrupole.

• Repetition is only determined by available rf power.– no tracking between magnet and rf.– Higher the voltage, higher the repetition and higher the

beam power.

FFAG acceleratorsno difference from others

• DC magnets– Like the one for storage ring (PSR, SNS).– Field can be highly nonlinear, but not complex.

• rf cavity– Ferrite (Magnetic Alloy) loaded cavity.– Fixed frequency cavity without material.

• Injection and extraction– Same problems of kicker and septum.

Applications

• Accelerator for particle therapy [- high repetition -]– Proton as well as carbon.

• Proton drivers for [- high average current -]– Neutron (muon) source.– ADSR (Accelerator Driven Subcritical Reactor).

• Accelerator for secondary particles [- fast acceleration -]– Muon– Unstable nuclei

• Accelerator for industry and security [- easy operation -]

H. Tanaka, et al, cyclotron2004

Projects at RAL (or in UK)

• EMMA– Demonstration of rapid acceleration.– Proof of principle of nonscaling FFAG for many

applications.

• PAMELA– An accelerator complex for proton and carbon therapy.

• Others– Design study of (proton and muon) accelerator for

neutrino factory.– Design study of accelerator for neutron source and ADSR.– Beam transport with FFAG optics.

EMMA (1)

• EMMA is an electron model, but its principle (nonscaling FFAG) should be used for proton and muon acceleration rather than electron.

• In UK, only project of FFAG beyond paper study.

EMMA (2)goals

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• Rapid acceleration with large tune variation due to natural chromaticity.

• Serpentine acceleration or acceleration outside rf bucket.

• Large acceptance for huge muon beam emittance.

EMMA (3)in pictures

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IonPump

Girder

IonPump

IonPump

Cavity FQUADDQUAD

EMMA (4)complete ring

• A beam circulates first for three turns and then for thousands turns a few day later.– on 16 August 2010

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First Turn Second Turn

EMMA (5)fixed momentum mode

• Beam position around the ring with fixed momentum.– Orbit shift in horizontal.– COD distortion is rather

large.– Peak at cell 25 is not real.

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EMMA (6)acceleration mode

• With rf voltage of 2 MV, orbit seems to start moving outward.

• Detailed study is underway.

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PAMELA (1)

• Prototype of proton and carbon therapy.• Prototype of proton driver for neutron source and

ADSR.

PAMELA (2)our involvement 1

• Novel FFAG optics– Nonscaling but has scaling features such as zero

chromaticity.

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(0.25, 0.25)

(0.75, 0.25)

qy=0.50

qy=0.0

qx=0.50

– Operate at the second stable area of Hill’s equation, which makes orbit shift ~5 times less.

Normal cell Dispersion suppressor

PAMELA (3)our involvement 2

• FFAG beam transport– Momentum acceptance of +/- a few 10%– Between acc and gantry.– To beam dump when trip occurs.

Neutron source and ADSR (1)potential to high beam power

• Beam power is a product of– Particle per pulse: N [ppp]– Repetition rate: F [Hz]– Particle energy: E [GeV]

• N is similar to synchrotron.• F can be 100 times higher.• E is between cyclotron and synchrotron.

Neutron source and ADSR (2)potential to high beam power

• N = 2 x 1013, F = 1 kHz, E = 2.5 GeV gives 8 MW.

• However, space charge limit at injection is one of big issues.– e.g. at J-Parc, tune shift of -0.25 at 400 MeV with N=8.33 x

1013.– Need space charge study in FFAG.– A lot of expertise is here at RAL.

Neutron source and ADSR (3)

• FFAG proton driver (no update since 2009.)

31 MeV injector cyclotron

250 MeV booster FFAG

1.5 GeV main FFAG

Summary

• FFAG accelerator is not a fancy new comer.• Hardware is similar or same with the one for

synchrotrons.• It operates differently to maximize repetition and

beam power.

• One criticism: no operational machine exists.– Hardware R&D for synchrotron directly applies.– Operation experience of EMMA and others helps.

Backup slides

EMMA (2)Muon FFAG and EMMA

• Requirement of rf is much lower, a factor of 1000.• Space is more packed in longitudinal than in transverse.

– Relatively large aperture magnets.– Injection/extraction might be harder than Muon FFAG.

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Muon FFAG EMMA Ratio

Momentum 12.6 – 25 GeV/c 10 – 20 MeV/c 1 : 0.001

rf voltage 1214 MV 2.28 MV 1 : 0.002

Number of cell 64 42 1 : 0.66

Circumference 667 m 16.6 m 1 : 0.025

QD/QF length 2.251/1.087 m 0.0777/0.0588 m 1 : 0.035/0.054

Straight section 5 m 0.2 m 1 : 0.04

Aperture ~ 300 mm ~ 30 mm 1 : 0.1

EMMA (4)ALICE and EMMA at Daresbury

• Accelerators and Lasers in Combined Experiments

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Parameter Value

Nominal Gun Energy 350 keV

Injector Energy 8.35 MeV

Max. Energy 35 MeV

Linac RF Frequency 1.3 GHz

Max Bunch Charge 80 pC

Emittance 5-15 mm-mrad

EMMA

EMMA (5)betatron oscillation measurement

• Beam position at consecutive 7 cells tells– Betatron oscillation

frequency (cell tune)– Dispersion function from

the average of these.– Both consistent to model.

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Horizontal

Vertical

EMMA (6)time of flight measurement

• BPM signal is measure w.r.t. 1.3 GHz rf wave form.– Use different magnetic strength as easier than changing

ALICE injector momentum.

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Variable ALICE energy fixed EMMA fields

Fixed ALICE EnergyVariable EMMA fields