IPAC2012 - List of Authors (Hirshfield, J.L.)

Paper	Title	Page
WEPPP004	A Reciprocity Principle for Wakefields in a Two-Channel Coaxial Dielectric Structure	2726
	G.V. Sotnikov NSC/KIPT, Kharkov, Ukraine J.L. Hirshfield, T.C. Marshall, G.V. Sotnikov Omega-P, Inc., New Haven, USA S.V. Shchelkunov Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
	Funding: Research is supported by U.S. Department of Energy, Office of High Energy Physics. The reciprocity principle* is often used in applications of classical electromagnetism. We have employed this principle for testing wakefields set up by an electron bunch in a two-channel coaxial dielectric structure (CDWA)*. For numerical studies we take a ~1-THz fused silica structure which we plan to test at FACET/SLAC; it has dimensions: outer shell, OD=800 μm, ID=500 μm; inner shell OD=181 μm, ID=50 μm. The structure is energized by a 23-GeV, 3-nC bunch having axial RMS size=25 μm. FACET has no drive bunch of annular shape as required for a CDWA; nevertheless, our analytical studies and simulations prove that for the axial wakefield, an annular drive bunch can be replaced by a pencil-like bunch of the same charge traveling in the annular vacuum channel. The longitudinal electric field along the accelerator channel axis (as recorded by a witness bunch) set up by this pencil-like bunch is the same as in the conventional structure of the CDWA. Moreover, if we interchange the drive bunch and the witness bunch, the witness bunch will register the same axial wakefield. However, the stability of the annular bunch is far superior to that of the pencil bunch. L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media (Addison-Wesley: Reading, MA, 1960). **G. Sotnikov et al., PRST-AB, 061302 (2009).

WEPPP011	Multi-Cavity Proton Cyclotron Accelerator: An Electron Counterpart	2744
	M.A. LaPointe, S.V. Shchelkunov Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA J.L. Hirshfield Omega-P, Inc., New Haven, USA V.P. Yakovlev Fermilab, Batavia, USA
	Funding: Supported by the Department of Energy, Office of Nuclear Physics. A multi-cavity multi-frequency proton cyclotron accelerator has been proposed. It would utilize cyclotron resonance in each of eight cavities of uniformly diminishing frequency in a uniform magnetic field to comprise a compact (25 m) 1 GeV proton accelerator, according to simulation results. A four cavity electron counterpart is under construction to test the mechanism of the multi-cavity setup, including phase acceptance, energy gain, and growth of energy spread and emittance for parameters equivalent to the proton case. The four electron counterpart cavities are driven by kW-level phase coherent RF sources at 1.5, 1.8, 2.1 and 2.4 GHz. Each cavity operates in the rotating TE111 mode and includes two feeds in quadrature to drive the rotating mode and two RF pickoffs for diagnostics. The electron beam source is a low-current gun with a BaO cathode which operates at -1200V and <50 microamps. After traversing the cavities, the beam is collected on either a Faraday cup or is imaged with a phosphor screen. Details of the setup and initial results from experiments with the four cavity electron counterpart will be presented. M.A. LaPointe, V.P. Yakovlev, S.Yu. Kazakov, and J.L. Hirshfield, Proc. of PAC 2009, May 4-8,Vancouver, BC, Canada, pp.3045-3047 (2011).

WEPPP012	High-Gradient THz-Scale Two-Channel Coaxial Dielectric-Lined Wakefield Accelerator	2747
	S.V. Shchelkunov, M.A. LaPointe Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA J.L. Hirshfield, T.C. Marshall Omega-P, Inc., New Haven, USA G.V. Sotnikov NSC/KIPT, Kharkov, Ukraine
	Funding: Research is supported by U.S. Department of Energy, Office of High Energy Physics. A mm-scale THz Coaxial Dielectric Wakefield Accelerator structure is currently under study by Yale University Beam Physics Lab and collaborators for its performance with annular drive bunches. With our recent successful experiments with the cm-scale GHz rectangular module at AWA/Argonne (USA) and planned activity there with yet another cm-scale GHz coaxial structure, the program of new research has two objectives. The first is to design a structure to produce acceleration gradients approaching 0.35 GeV/m per each nC of drive charge when excited by an annular-like bunch; has an attractive feature that the drive and accelerated bunches both have good focusing and stability properties; and also exhibits a large transformer ratio. The second goal is to build and test the structure at FACET/SLAC (USA). At FACET the structure can be excited only with the available pencil-like drive bunch, but the reciprocity principle allows one to observe some of the properties that would be seen if the excitation were to be by an annular drive bunch. This presentation shows our latest findings, discusses related issues, and discusses our plans for experiments.

THPPC041	704 MHz Fast High-power Ferroelectric Phase Shifter for Energy Recovery Linac Applications	3374
	S.V. Shchelkunov Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA J.L. Hirshfield Omega-P, Inc., New Haven, USA A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA S. Kazakov, V.P. Yakovlev Fermilab, Batavia, USA A.B. Kozyrev LETI, Saint-Petersburg, Russia E. Nenasheva Ceramics Ltd., St. Petersburg, Russia
	Funding: Research supported by the U.S. Department of Energy, Office of High Energy Physics Development, tests, and evaluation of a fast electrically-controlled 704 MHz tuner for Energy Recovery Linacs that employs an electrically -controlled ferroelectric component are presented. The tuner is a refinement of an already tested prototype described elsewhere. In the new concept, a collection of ferroelectric assemblies behave as cavities configured as transmission components within a coaxial waveguide. Each assembly is based on a ring-like ferroelectric ceramic with its height, inner and outer diameters, and the shape of edges adjusted to insure a clean operating mode, and relatively low field strength. Several assemblies serve to widen the passband and increase tunability. The tuner is to deliver fast (~100-200 ns) phase adjustment from 0-to-100 degrees when biased by voltages from 0-to-15kV; the design promises to handle 50 kW CW and 900 kW of pulsed power. A scaled version is also considered to operate at 1300 MHz while handling 500 kW of pulsed power. Our latest findings, related issues, and plans for experiments are discussed.

THPPC042	Modified Magnicon for High-Gradient Accelerator R&D	3377
	S.V. Shchelkunov, Y. Jiang, M.A. LaPointe Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA J.L. Hirshfield Omega-P, Inc., New Haven, USA V.P. Yakovlev Fermilab, Batavia, USA
	Funding: Research supported by the U.S. Department of Energy, Office of High Energy Physics A self-consistent design is described of a modified 34.3 GHz magnicon amplifier with a TE311-mode output cavity, to replace the existing magnicon at Yale Beam Physics Lab Test Facility whose output cavity operates in the TM310 mode. The main goal for the new design is to achieve robust reliable operation. This is expected since tube performance – according to simulations – is largely insensitive to the magnitude of external dc magnetic fields, including imperfections in magnetic field profile; small changes in gun voltage and current; changes in electron beam radial size; and even poorly matched external circuitry. The new tube, as with its predecessor, is a third harmonic amplifier, with drive and deflection gain cavities near 11.424 GHz and output cavity at 34.272 GHz. The design calculations predict stable output of power of 20-27 MW at a 10 Hz repetition rate in pulses up to 1.3 μs long, with a low probability of breakdown in the output cavity because of low electric fields (less than 650 kV/cm).

Paper

Title

Page

A Reciprocity Principle for Wakefields in a Two-Channel Coaxial Dielectric Structure

2726

G.V. Sotnikov
NSC/KIPT, Kharkov, Ukraine
J.L. Hirshfield, T.C. Marshall, G.V. Sotnikov
Omega-P, Inc., New Haven, USA
S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA

Funding: Research is supported by U.S. Department of Energy, Office of High Energy Physics.
The reciprocity principle* is often used in applications of classical electromagnetism. We have employed this principle for testing wakefields set up by an electron bunch in a two-channel coaxial dielectric structure (CDWA)**. For numerical studies we take a ~1-THz fused silica structure which we plan to test at FACET/SLAC; it has dimensions: outer shell, OD=800 μm, ID=500 μm; inner shell OD=181 μm, ID=50 μm. The structure is energized by a 23-GeV, 3-nC bunch having axial RMS size=25 μm. FACET has no drive bunch of annular shape as required for a CDWA; nevertheless, our analytical studies and simulations prove that for the axial wakefield, an annular drive bunch can be replaced by a pencil-like bunch of the same charge traveling in the annular vacuum channel. The longitudinal electric field along the accelerator channel axis (as recorded by a witness bunch) set up by this pencil-like bunch is the same as in the conventional structure of the CDWA. Moreover, if we interchange the drive bunch and the witness bunch, the witness bunch will register the same axial wakefield. However, the stability of the annular bunch is far superior to that of the pencil bunch.
*L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media (Addison-Wesley: Reading, MA, 1960).
**G. Sotnikov et al., PRST-AB, 061302 (2009).

WEPPP011

Multi-Cavity Proton Cyclotron Accelerator: An Electron Counterpart

2744

M.A. LaPointe, S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, USA
V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Supported by the Department of Energy, Office of Nuclear Physics.
A multi-cavity multi-frequency proton cyclotron accelerator has been proposed. It would utilize cyclotron resonance in each of eight cavities of uniformly diminishing frequency in a uniform magnetic field to comprise a compact (25 m) 1 GeV proton accelerator, according to simulation results*. A four cavity electron counterpart is under construction to test the mechanism of the multi-cavity setup, including phase acceptance, energy gain, and growth of energy spread and emittance for parameters equivalent to the proton case. The four electron counterpart cavities are driven by kW-level phase coherent RF sources at 1.5, 1.8, 2.1 and 2.4 GHz. Each cavity operates in the rotating TE111 mode and includes two feeds in quadrature to drive the rotating mode and two RF pickoffs for diagnostics. The electron beam source is a low-current gun with a BaO cathode which operates at -1200V and <50 microamps. After traversing the cavities, the beam is collected on either a Faraday cup or is imaged with a phosphor screen. Details of the setup and initial results from experiments with the four cavity electron counterpart will be presented.
* M.A. LaPointe, V.P. Yakovlev, S.Yu. Kazakov, and J.L. Hirshfield, Proc. of PAC 2009, May 4-8,Vancouver, BC, Canada, pp.3045-3047 (2011).

WEPPP012

High-Gradient THz-Scale Two-Channel Coaxial Dielectric-Lined Wakefield Accelerator

2747

S.V. Shchelkunov, M.A. LaPointe
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield, T.C. Marshall
Omega-P, Inc., New Haven, USA
G.V. Sotnikov
NSC/KIPT, Kharkov, Ukraine

Funding: Research is supported by U.S. Department of Energy, Office of High Energy Physics.
A mm-scale THz Coaxial Dielectric Wakefield Accelerator structure is currently under study by Yale University Beam Physics Lab and collaborators for its performance with annular drive bunches. With our recent successful experiments with the cm-scale GHz rectangular module at AWA/Argonne (USA) and planned activity there with yet another cm-scale GHz coaxial structure, the program of new research has two objectives. The first is to design a structure to produce acceleration gradients approaching 0.35 GeV/m per each nC of drive charge when excited by an annular-like bunch; has an attractive feature that the drive and accelerated bunches both have good focusing and stability properties; and also exhibits a large transformer ratio. The second goal is to build and test the structure at FACET/SLAC (USA). At FACET the structure can be excited only with the available pencil-like drive bunch, but the reciprocity principle allows one to observe some of the properties that would be seen if the excitation were to be by an annular drive bunch. This presentation shows our latest findings, discusses related issues, and discusses our plans for experiments.

THPPC041

704 MHz Fast High-power Ferroelectric Phase Shifter for Energy Recovery Linac Applications

3374

S.V. Shchelkunov
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, USA
A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
S. Kazakov, V.P. Yakovlev
Fermilab, Batavia, USA
A.B. Kozyrev
LETI, Saint-Petersburg, Russia
E. Nenasheva
Ceramics Ltd., St. Petersburg, Russia

Funding: Research supported by the U.S. Department of Energy, Office of High Energy Physics
Development, tests, and evaluation of a fast electrically-controlled 704 MHz tuner for Energy Recovery Linacs that employs an electrically -controlled ferroelectric component are presented. The tuner is a refinement of an already tested prototype described elsewhere. In the new concept, a collection of ferroelectric assemblies behave as cavities configured as transmission components within a coaxial waveguide. Each assembly is based on a ring-like ferroelectric ceramic with its height, inner and outer diameters, and the shape of edges adjusted to insure a clean operating mode, and relatively low field strength. Several assemblies serve to widen the passband and increase tunability. The tuner is to deliver fast (~100-200 ns) phase adjustment from 0-to-100 degrees when biased by voltages from 0-to-15kV; the design promises to handle 50 kW CW and 900 kW of pulsed power. A scaled version is also considered to operate at 1300 MHz while handling 500 kW of pulsed power. Our latest findings, related issues, and plans for experiments are discussed.

THPPC042

Modified Magnicon for High-Gradient Accelerator R&D

3377

S.V. Shchelkunov, Y. Jiang, M.A. LaPointe
Yale University, Beam Physics Laboratory, New Haven, Connecticut, USA
J.L. Hirshfield
Omega-P, Inc., New Haven, USA
V.P. Yakovlev
Fermilab, Batavia, USA

Funding: Research supported by the U.S. Department of Energy, Office of High Energy Physics
A self-consistent design is described of a modified 34.3 GHz magnicon amplifier with a TE311-mode output cavity, to replace the existing magnicon at Yale Beam Physics Lab Test Facility whose output cavity operates in the TM310 mode. The main goal for the new design is to achieve robust reliable operation. This is expected since tube performance – according to simulations – is largely insensitive to the magnitude of external dc magnetic fields, including imperfections in magnetic field profile; small changes in gun voltage and current; changes in electron beam radial size; and even poorly matched external circuitry. The new tube, as with its predecessor, is a third harmonic amplifier, with drive and deflection gain cavities near 11.424 GHz and output cavity at 34.272 GHz. The design calculations predict stable output of power of 20-27 MW at a 10 Hz repetition rate in pulses up to 1.3 μs long, with a low probability of breakdown in the output cavity because of low electric fields (less than 650 kV/cm).