Cyclotrons2013 - List of Authors (Johnstone, C.)

Paper

Title

Page

A Compact, GeV, High-Intensity (CW) Racetrack FFAG

73

C. Johnstone
Fermilab, Batavia, Illinois, USA
M. Berz, K. Makino
MSU, East Lansing, Michigan, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

High-intensity and energy compact proton accelerators, especially those requiring milliamp currents, imply both CW operation and high acceleration gradients to mitigate losses. Above a few hundred MeV, losses must be under a per cent to avoid massive shielding and unmanageable activation. As relativistic energies are approached, the orbit separation on consecutive acceleration turns decreases for isochronous performance and to achieve higher acceleration gradients and orbit separation, RF modules must be employed rather than Dees, resulting in the larger separated-sector cyclotron footprint. However, the addition of strong focusing – with reversed gradients to capture both transverse planes – to conventional cyclotron fields promote inclusion of long synchrotron-like straight sections and implementation of high-gradient RF, even SCRF. The nsFFAG design has evolved into a a recirculating linear accelerator form with FFAG arcs. An ultra-compact, 0.2 – 1 GeV RLA FFAG design will be discussed (with a 3m x 5-6m footprint) that uses SC RF cryomodules achieving complete orbit separation at extraction and CW operation.

MO3PB03

High Gradient Superconducting Cavity Development for FFAG

105

S.V. Kutsaev, Z.A. Conway, P.N. Ostroumov
ANL, Argonne, USA
R.D. Ford, C. Johnstone
PAC, Batavia, Illinois, USA

Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357
Like the cyclotron, the Fixed Field Alternating Gradient machine (FFAG) is a compact accelerator with variety of applications in industry and medicine. High intensity, fixed-field compact accelerators require enhanced orbit separation to minimize beam losses especially at extraction. In medium energy and compact FFAGs, this requires a total voltage of ~20 MV per turn with continuous wave accelerating gradients of ~10MV/m, which can only be achieved using superconducting accelerating cavities. This high voltage can be generated using 4 superconducting (SC) cavities operating at higher harmonics of the beam revolution, equal to approximately 200 MHz. The cavities and cryomodule are inserted into a 2m straight section of a racetrack-shaped FFAG. However, as with cyclotrons, the FFAG has a large horizontal acceleration aperture presenting a challenging problem for SCRF cavity design. In this work, we present SC cavity design with 50 cm x 1 cm beam apertures, their electrodynamics optimization, and multiphysics analysis. To achieve a 1 mA average beam current, each cavity is powered by two 100 kW RF couplers.

Slides MO3PB03 [2.819 MB]

Paper	Title	Page
MOPPT019	A Compact, GeV, High-Intensity (CW) Racetrack FFAG	73
	C. Johnstone Fermilab, Batavia, Illinois, USA M. Berz, K. Makino MSU, East Lansing, Michigan, USA P. Snopok Illinois Institute of Technology, Chicago, Illinois, USA
	High-intensity and energy compact proton accelerators, especially those requiring milliamp currents, imply both CW operation and high acceleration gradients to mitigate losses. Above a few hundred MeV, losses must be under a per cent to avoid massive shielding and unmanageable activation. As relativistic energies are approached, the orbit separation on consecutive acceleration turns decreases for isochronous performance and to achieve higher acceleration gradients and orbit separation, RF modules must be employed rather than Dees, resulting in the larger separated-sector cyclotron footprint. However, the addition of strong focusing – with reversed gradients to capture both transverse planes – to conventional cyclotron fields promote inclusion of long synchrotron-like straight sections and implementation of high-gradient RF, even SCRF. The nsFFAG design has evolved into a a recirculating linear accelerator form with FFAG arcs. An ultra-compact, 0.2 – 1 GeV RLA FFAG design will be discussed (with a 3m x 5-6m footprint) that uses SC RF cryomodules achieving complete orbit separation at extraction and CW operation.

MO3PB03	High Gradient Superconducting Cavity Development for FFAG	105
	S.V. Kutsaev, Z.A. Conway, P.N. Ostroumov ANL, Argonne, USA R.D. Ford, C. Johnstone PAC, Batavia, Illinois, USA
	Funding: This work was supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 Like the cyclotron, the Fixed Field Alternating Gradient machine (FFAG) is a compact accelerator with variety of applications in industry and medicine. High intensity, fixed-field compact accelerators require enhanced orbit separation to minimize beam losses especially at extraction. In medium energy and compact FFAGs, this requires a total voltage of ~20 MV per turn with continuous wave accelerating gradients of ~10MV/m, which can only be achieved using superconducting accelerating cavities. This high voltage can be generated using 4 superconducting (SC) cavities operating at higher harmonics of the beam revolution, equal to approximately 200 MHz. The cavities and cryomodule are inserted into a 2m straight section of a racetrack-shaped FFAG. However, as with cyclotrons, the FFAG has a large horizontal acceleration aperture presenting a challenging problem for SCRF cavity design. In this work, we present SC cavity design with 50 cm x 1 cm beam apertures, their electrodynamics optimization, and multiphysics analysis. To achieve a 1 mA average beam current, each cavity is powered by two 100 kW RF couplers.
	Slides MO3PB03 [2.819 MB]