2011 Particle Accelerator Conference - Table of Session: THOAS (Accelerator Technology IV)

Paper

Title

Page

On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams

2044

Z. Li, C. Adolphsen, A.E. Vlieks, F. Zhou
SLAC, Menlo Park, California, USA

Funding: Work was supported by DOE Contract No. DE-AC02-76SF00515 and used computing resources at NERSC supported by DOE Contract No. DE-AC02- 05CH11231.
The input power of accelerator structure is normally fed through a coupling slot(s) on the outer wall of the accelerator structure via magnetic coupling. While providing perfect matching, the coupling slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance growth as the beam is accelerated in such a field. This effect is especially important for low emittance beams at low energies such as in the injector accelerators for light sources. In this paper, we present studies of multipole fields of different rf coupler designs and their effect on beam emittance for an X-band photocathode gun, being jointly designed with LLNL, and the X-band accelerator structures. We will present symmetrized rf coupler designs for these components to preserve the beam emittance.

Slides THOAS1 [1.512 MB]

THOAS2

Solid State RF Power - The route to 1W per Euro Cent

2047

O. Heid
Siemens AG, Healthcare Technology and Concepts, Erlangen, Germany
T.J.S. Hughes
Siemens AG, Erlangen, Germany

In most particle accelerators RF power is a decisive design constraint due to high costs and relative inflexibility of power sources based on electron beams i.e. Klystrons, Magnetrons, Tetrodes etc. At VHF/UHF frequencies the transition to solid state devices promises to fundamentally change the situation. Recent progress brings 1 Watt per Euro cent installed cost within reach. We present a Silicon Carbide semiconductor solution utilising the Solid State Direct Drive technology [*,**,***] at unprecedented efficiency, power levels and power densities. The proposed solutions allows retrofitting of existing RF solutions and opens the route to novel accelerator designs.
* Heid O., Hughes T. THPD002, IPAC10, Kyoto, Japan
** Hergt M et al, 2010 IEEE International Power Modulator and High Voltage Conf., Atlanta GA, USA
*** Heid O., Hughes T. THP068, LINAC10, Tsukuba, Japan

Slides THOAS2 [1.776 MB]

THOAS3

Status of the Oak Ridge Spallation Neutron Source (SNS) RF Systems

2050

T.W. Hardek, M.T. Crofford, Y.W. Kang, M.F. Piller, A.V. Vassioutchenko
ORNL, Oak Ridge, Tennessee, USA
S.W. Lee, M.E. Middendorf
ORNL RAD, Oak Ridge, Tennessee, USA

The SNS has been delivering production neutrons for five years with first beam delivered to the neutron target at the end of April 2006. On September 18, 2009 SNS officially reached 1 megawatt of beam on target marking the achievement of a decades-old dream of providing a U.S. megawatt class pulsed spallation source. The SNS is now routinely delivering 1 megawatt of beam power to the neutron target at over 85 percent of the scheduled beam time. The present effort is aimed at increasing availability eventually to 95 percent and gradually increasing the intensity to the 1.4 megawatt design level. While the RF systems have performed well since initial installation some improvements have been implemented. This paper provides a review of the SNS RF Systems, an overview of the performance of the various components and a detailed review of RF related issues addressed over the past several years.

Slides THOAS3 [2.759 MB]

THOAS4

Enhancement of RF Breakdown Threshold of Microwave Cavities by Magnetic Insulation

2053

D. Stratakis
UCLA, Los Angeles, California, USA
J.C. Gallardo, R. B. Palmer
BNL, Upton, Long Island, New York, USA

Funding: This work is funded by US Dept. of Energy grant number DE AC02-98CH10886.
Limitations on the maximum achievable accelerating gradient of microwave cavities can influence the performance, length, and cost of particle accelerators. Gradient limitations are widely believed to be initiated by electron emission from the cavity surfaces. Here, we show that field emission is effectively suppressed by applying a tangential magnetic field to the cavity walls, so higher gradients can be achieved. Numerical simulations indicate that the magnetic field prevents electrons leaving these surfaces and subsequently picking up energy from the electric field. Implementation of the proposed concept into prospective particle accelerator applications is studied by two specific examples - a multi TeV lepton-antilepton collider and a linear muon accelerator driver for an intense neutrino source.

Slides THOAS4 [1.441 MB]

Paper	Title	Page
THOAS1	On the Importance of Symmetrizing RF Coupler Fields for Low Emittance Beams	2044
	Z. Li, C. Adolphsen, A.E. Vlieks, F. Zhou SLAC, Menlo Park, California, USA
	Funding: Work was supported by DOE Contract No. DE-AC02-76SF00515 and used computing resources at NERSC supported by DOE Contract No. DE-AC02- 05CH11231. The input power of accelerator structure is normally fed through a coupling slot(s) on the outer wall of the accelerator structure via magnetic coupling. While providing perfect matching, the coupling slots may produce non-axial-symmetric fields in the coupler cell that can induce emittance growth as the beam is accelerated in such a field. This effect is especially important for low emittance beams at low energies such as in the injector accelerators for light sources. In this paper, we present studies of multipole fields of different rf coupler designs and their effect on beam emittance for an X-band photocathode gun, being jointly designed with LLNL, and the X-band accelerator structures. We will present symmetrized rf coupler designs for these components to preserve the beam emittance.
	Slides THOAS1 [1.512 MB]

THOAS2	Solid State RF Power - The route to 1W per Euro Cent	2047
	O. Heid Siemens AG, Healthcare Technology and Concepts, Erlangen, Germany T.J.S. Hughes Siemens AG, Erlangen, Germany
	In most particle accelerators RF power is a decisive design constraint due to high costs and relative inflexibility of power sources based on electron beams i.e. Klystrons, Magnetrons, Tetrodes etc. At VHF/UHF frequencies the transition to solid state devices promises to fundamentally change the situation. Recent progress brings 1 Watt per Euro cent installed cost within reach. We present a Silicon Carbide semiconductor solution utilising the Solid State Direct Drive technology [,,*] at unprecedented efficiency, power levels and power densities. The proposed solutions allows retrofitting of existing RF solutions and opens the route to novel accelerator designs. Heid O., Hughes T. THPD002, IPAC10, Kyoto, Japan Hergt M et al, 2010 IEEE International Power Modulator and High Voltage Conf., Atlanta GA, USA * Heid O., Hughes T. THP068, LINAC10, Tsukuba, Japan
	Slides THOAS2 [1.776 MB]

THOAS3	Status of the Oak Ridge Spallation Neutron Source (SNS) RF Systems	2050
	T.W. Hardek, M.T. Crofford, Y.W. Kang, M.F. Piller, A.V. Vassioutchenko ORNL, Oak Ridge, Tennessee, USA S.W. Lee, M.E. Middendorf ORNL RAD, Oak Ridge, Tennessee, USA
	The SNS has been delivering production neutrons for five years with first beam delivered to the neutron target at the end of April 2006. On September 18, 2009 SNS officially reached 1 megawatt of beam on target marking the achievement of a decades-old dream of providing a U.S. megawatt class pulsed spallation source. The SNS is now routinely delivering 1 megawatt of beam power to the neutron target at over 85 percent of the scheduled beam time. The present effort is aimed at increasing availability eventually to 95 percent and gradually increasing the intensity to the 1.4 megawatt design level. While the RF systems have performed well since initial installation some improvements have been implemented. This paper provides a review of the SNS RF Systems, an overview of the performance of the various components and a detailed review of RF related issues addressed over the past several years.
	Slides THOAS3 [2.759 MB]

THOAS4	Enhancement of RF Breakdown Threshold of Microwave Cavities by Magnetic Insulation	2053
	D. Stratakis UCLA, Los Angeles, California, USA J.C. Gallardo, R. B. Palmer BNL, Upton, Long Island, New York, USA
	Funding: This work is funded by US Dept. of Energy grant number DE AC02-98CH10886. Limitations on the maximum achievable accelerating gradient of microwave cavities can influence the performance, length, and cost of particle accelerators. Gradient limitations are widely believed to be initiated by electron emission from the cavity surfaces. Here, we show that field emission is effectively suppressed by applying a tangential magnetic field to the cavity walls, so higher gradients can be achieved. Numerical simulations indicate that the magnetic field prevents electrons leaving these surfaces and subsequently picking up energy from the electric field. Implementation of the proposed concept into prospective particle accelerator applications is studied by two specific examples - a multi TeV lepton-antilepton collider and a linear muon accelerator driver for an intense neutrino source.
	Slides THOAS4 [1.441 MB]