IPAC2011 - List of Authors (Johnson, R.P.)

Paper

Title

Page

Phase and Frequency Locked Magnetrons for SRF Sources

406

M.L. Neubauer, M.A.C. Cummings, A. Dudas, R.P. Johnson, R. Sah
Muons, Inc, Batavia, USA
A. Moretti, M. Popovic
Fermilab, Batavia, USA

Typically, high power sources for accelerator applications are multi-megawatt microwave tubes that may be combined together to form ultra-high-power localized power stations. The RF power is then distributed to multiple strings of cavities through high power waveguide systems which are problematic in terms of expense, efficiency, and reliability. Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate, when magnetrons are used as power sources for accelerators. Novel variable frequency cavity techniques have been developed which will be utilized to phase and frequency lock magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials will be attached in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. The microwave characteristics of several materials have been tested with magnetic fields to control the frequency of the magnetron. These results will be presented and an optimum material chosen.

WEPZ009

Parametric-Resonance Ionization Cooling in Twin-Helix

2784

V.S. Morozov, Y.S. Derbenev
JLAB, Newport News, Virginia, USA
A. Afanasev, R.P. Johnson
Muons, Inc, Batavia, USA
B. Erdelyi, J.A. Maloney
Northern Illinois University, DeKalb, Illinois, USA

Funding: Supported in part by DOE SBIR grant DE-SC0005589. Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. For the implementation of PIC, we developed an epicyclic twin-helix channel with correlated optics. Wedge-shaped absorbers immediately followed by short rf cavities are placed into the twin-helix channel. Parametric resonances are induced in both planes using helical quadrupole harmonics. We demonstrate resonant dynamics and cooling with stochastic effects off using GEANT4/ G4beamline. We illustrate compensation of spherical aberrations and benchmark COSY Infinity, a powerful tool for aberration analysis and compensation.

THOAB01

Accelerator-driven Subcritical Molten-salt-fueled Reactors

2868

R.P. Johnson
Muons, Inc, Batavia, USA
C. Bowman
ADNA, Los Alamos, New Mexico, USA

Reactors built using solid fissile materials sealed in fuel rods have an inherent safety problem in that volatile radioactive materials in the rods are accumulated and can be released in dangerous amounts. Accelerator parameters for subcritical reactors that have been considered in recent studies have primarily been based on using solid nuclear fuel much like that used in all operating critical reactors as well as the thorium-burning accelerator-driven energy amplifier proposed by Rubbia et al. An attractive alternative reactor design that used molten salts was experimentally studied at ORNL in the 1960s, where a critical molten salt reactor was successfully operated using enriched U235 or U233 tetrafluoride fuels. These experiments give confidence that an accelerator-driven subcritical molten salt reactor will work as well or better than conventional reactors, having better efficiency due to their higher operating temperature, having the inherent safety of subcritical operation, and having constant purging of volatile radioactive elements to eliminate their accumulation and potential accidental release in dangerous amounts.

Slides THOAB01 [5.723 MB]

THPS026

Surface Plasma H⁻ Ion Source with Saddle RF Antenna Plasma Generator

3475

V.G. Dudnikov, R.P. Johnson
Muons, Inc, Batavia, USA
S.N. Murray, T.R. Pennisi, M. Santana, M.P. Stockli, R.F. Welton
ORNL, Oak Ridge, Tennessee, USA

Funding: *Work supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant DE-SC0002690.
In this project is developed a prototype RF H⁻ surface plasma source (SPS) with saddle (SA) RF antenna which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with a small AlN test chamber and different antennas and magnetic field configurations were tested in the SNS ion source Test Stand. A prototype SA SPS was installed in the Test Stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency of 1.6 mA/kW. Control experiments with H⁻ beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma source (TPS) has been designed. A Saddle antenna SPS with water cooling is being fabricated for high duty factor testing.

THPS027

Cesiation in Highly Efficient Surface Plasma Sources

3478

V.G. Dudnikov, R.P. Johnson
Muons, Inc, Batavia, USA

Funding: Work supported in part by STTR grant DE-SC0002690.
Features of cesiation* in different modifications of H-/D- source designs have been considered. New sources under development include advanced versions of Compact Surface Plasma Sources (CSPS) which will efficiently generate brighter beam in noiseless discharge, deliver significantly increased (up to 20 mA) average current with better electrode cooling using new materials, have significantly extended lifetime and reduced cesium consumption. Related ion sources that use cesium are described and an improved cesiation procedure for reproducible production of high efficiency H⁻ ion generation is considered.
* V. Dudnikov, SU Author Certificate, C1.H01 3/04, No. 411542, 10 March, 1972.

Paper	Title	Page
MOPC140	Phase and Frequency Locked Magnetrons for SRF Sources	406
	M.L. Neubauer, M.A.C. Cummings, A. Dudas, R.P. Johnson, R. Sah Muons, Inc, Batavia, USA A. Moretti, M. Popovic Fermilab, Batavia, USA
	Typically, high power sources for accelerator applications are multi-megawatt microwave tubes that may be combined together to form ultra-high-power localized power stations. The RF power is then distributed to multiple strings of cavities through high power waveguide systems which are problematic in terms of expense, efficiency, and reliability. Magnetrons are the lowest cost microwave source in dollars/kW, and they have the highest efficiency (typically greater than 85%). However, the frequency stability and phase stability of magnetrons are not adequate, when magnetrons are used as power sources for accelerators. Novel variable frequency cavity techniques have been developed which will be utilized to phase and frequency lock magnetrons, allowing their use for either individual cavities, or cavity strings. Ferrite or YIG (Yttrium Iron Garnet) materials will be attached in the regions of high magnetic field of radial-vaned, π−mode structures of a selected ordinary magnetron. The microwave characteristics of several materials have been tested with magnetic fields to control the frequency of the magnetron. These results will be presented and an optimum material chosen.

WEPZ009	Parametric-Resonance Ionization Cooling in Twin-Helix	2784
	V.S. Morozov, Y.S. Derbenev JLAB, Newport News, Virginia, USA A. Afanasev, R.P. Johnson Muons, Inc, Batavia, USA B. Erdelyi, J.A. Maloney Northern Illinois University, DeKalb, Illinois, USA
	Funding: Supported in part by DOE SBIR grant DE-SC0005589. Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Parametric-resonance Ionization Cooling (PIC) is proposed as the final 6D cooling stage of a high-luminosity muon collider. For the implementation of PIC, we developed an epicyclic twin-helix channel with correlated optics. Wedge-shaped absorbers immediately followed by short rf cavities are placed into the twin-helix channel. Parametric resonances are induced in both planes using helical quadrupole harmonics. We demonstrate resonant dynamics and cooling with stochastic effects off using GEANT4/ G4beamline. We illustrate compensation of spherical aberrations and benchmark COSY Infinity, a powerful tool for aberration analysis and compensation.

THOAB01	Accelerator-driven Subcritical Molten-salt-fueled Reactors	2868
	R.P. Johnson Muons, Inc, Batavia, USA C. Bowman ADNA, Los Alamos, New Mexico, USA
	Reactors built using solid fissile materials sealed in fuel rods have an inherent safety problem in that volatile radioactive materials in the rods are accumulated and can be released in dangerous amounts. Accelerator parameters for subcritical reactors that have been considered in recent studies have primarily been based on using solid nuclear fuel much like that used in all operating critical reactors as well as the thorium-burning accelerator-driven energy amplifier proposed by Rubbia et al. An attractive alternative reactor design that used molten salts was experimentally studied at ORNL in the 1960s, where a critical molten salt reactor was successfully operated using enriched U235 or U233 tetrafluoride fuels. These experiments give confidence that an accelerator-driven subcritical molten salt reactor will work as well or better than conventional reactors, having better efficiency due to their higher operating temperature, having the inherent safety of subcritical operation, and having constant purging of volatile radioactive elements to eliminate their accumulation and potential accidental release in dangerous amounts.
	Slides THOAB01 [5.723 MB]

THPS026	Surface Plasma H⁻ Ion Source with Saddle RF Antenna Plasma Generator	3475
	V.G. Dudnikov, R.P. Johnson Muons, Inc, Batavia, USA S.N. Murray, T.R. Pennisi, M. Santana, M.P. Stockli, R.F. Welton ORNL, Oak Ridge, Tennessee, USA
	Funding: *Work supported in part by US DOE Contract DE-AC05-00OR22725 and by STTR grant DE-SC0002690. In this project is developed a prototype RF H⁻ surface plasma source (SPS) with saddle (SA) RF antenna which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with a small AlN test chamber and different antennas and magnetic field configurations were tested in the SNS ion source Test Stand. A prototype SA SPS was installed in the Test Stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency of 1.6 mA/kW. Control experiments with H⁻ beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma source (TPS) has been designed. A Saddle antenna SPS with water cooling is being fabricated for high duty factor testing.

THPS027	Cesiation in Highly Efficient Surface Plasma Sources	3478
	V.G. Dudnikov, R.P. Johnson Muons, Inc, Batavia, USA
	Funding: Work supported in part by STTR grant DE-SC0002690. Features of cesiation* in different modifications of H-/D- source designs have been considered. New sources under development include advanced versions of Compact Surface Plasma Sources (CSPS) which will efficiently generate brighter beam in noiseless discharge, deliver significantly increased (up to 20 mA) average current with better electrode cooling using new materials, have significantly extended lifetime and reduced cesium consumption. Related ion sources that use cesium are described and an improved cesiation procedure for reproducible production of high efficiency H⁻ ion generation is considered. * V. Dudnikov, SU Author Certificate, C1.H01 3/04, No. 411542, 10 March, 1972.