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

Advanced Accelerator of protons what 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 accelerators what 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 accelerators no 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 9 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 10 Ion Pump Girder Ion Pump Ion Pump Cavity FQUAD DQUAD

EMMA (4) complete ring A beam circulates first for three turns and then for thousands turns a few day later. – on 16 August 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. 12

EMMA (6) acceleration mode With rf voltage of 2 MV, orbit seems to start moving outward. Detailed study is underway. 13

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. 15 (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 cellDispersion 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 10 13, 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 at 400 MeV with N=8.33 x – 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 Space is more packed in longitudinal than in transverse. – Relatively large aperture magnets. – Injection/extraction might be harder than Muon FFAG. 22 Muon FFAGEMMARatio Momentum12.6 – 25 GeV/c10 – 20 MeV/c1 : rf voltage1214 MV2.28 MV1 : Number of cell64421 : 0.66 Circumference667 m16.6 m1 : QD/QF length2.251/1.087 m0.0777/ m1 : 0.035/0.054 Straight section5 m0.2 m1 : 0.04 Aperture~ 300 mm~ 30 mm1 : 0.1

EMMA (4) ALICE and EMMA at Daresbury Accelerators and Lasers in Combined Experiments 23 ParameterValue Nominal Gun Energy350 keV Injector Energy8.35 MeV Max. Energy35 MeV Linac RF Frequency1.3 GHz Max Bunch Charge80 pC Emittance5-15 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. 24 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. 25 Variable ALICE energy fixed EMMA fields Fixed ALICE Energy Variable EMMA fields