PAC2013 - List of Authors (O'Hara, J.F.)

Paper	Title	Page
MOPMA14	Status of the LANSCE Front-End Upgrade	327
	R.W. Garnett, Y.K. Batygin, I. Draganić, C.M. Fortgang, S.S. Kurennoy, R.C. McCrady, J.F. O'Hara, R.J. Roybal, L. Rybarcyk LANL, Los Alamos, New Mexico, USA J. Haeuser Kress GmbH, Biebergemuend, Germany A. Schempp IAP, Frankfurt am Main, Germany
	Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396 Initial acceleration of the beams in the LANSCE linear accelerator at Los Alamos National Laboratory is still presently accomplished through the use of two 750-keV Cockcroft-Walton (CW) based injectors. To reduce long-term operational risks and to realize future beam performance goals, plans are underway to replace the existing H⁺ CW injector with a modern replacement, 4-rod Radio-Frequency Quadrupole (RFQ) based front end. Significant technical progress has been made since we last reported on this project. Status and progress of the design and fabrication of the RFQ, the RF system, beam transports, and integrated accelerator test stand will be discussed.

MOPSM05	Diagnostics for the LANSCE RFQ Front-End Test Stand	354
	R.C. McCrady, Y.K. Batygin, I. Draganić, C.M. Fortgang, R.W. Garnett, S.S. Kurennoy, J.F. O'Hara, E.R. Olivas, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	Plans are underway at the Los Alamos Neutron Science Center to replace the existing H⁺ Cockcroft-Walton injector with a modern 4-rod Radio-Frequency Quadrupole (RFQ) based front end. This will provide protons for injection into the downstream linac, where H⁻ ions are also accelerated. This dual-species operation of the linac imposes constraints on the injectors, resulting in particular requirements on the transverse and longitudinal emittances and phase-space distributions of the beam from the RFQ proton injector. Good measurements of these quantities are therefore required during the testing phase of the RFQ injector. In this paper we describe the measurements to be made and plans for the systems for carrying out the measurements.

TUPSM16	Progress Report of H⁻ Ion Beam Production at the LANL Ion Source Test Stand	667
	I. Draganić, Y.K. Batygin, C.M. Fortgang, R.W. Garnett, J.G. Gioia, S.S. Kurennoy, R.C. McCrady, J.F. O'Hara, G. Rouleau, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	As part of the Los Alamos Neutron Science Center (LANSCE) the Ion Source Test Stand (ISTS) is a flexible, stand-alone facility used for H⁻ ion beam source development and studies of low energy beam transport. It consists of a surface convertor ion source with a multi-cusp permanent-magnet plasma confinement structure, an 80-kV high-voltage electrostatic extraction column, a low-energy ion beam transport line, and beam phase-space diagnostics. After resolving several technical issues, the ISTS was successfully restarted during the summer of 2012. Since then we have performed several long duration experiments. A development program is ongoing with the goals of improving source performance (reliability, availability, increased current, etc.) and beam transport efficiency (beam neutralization at low energy, beam dynamics with/without noble gas injection, etc.). Several enhancements to performance are being investigated in order to achieve a forthcoming upgrade requirement of LANSCE operations in 2014: beam current of 16-18 mA, 120-Hz operation at a duty factor of 10% and a source lifetime of 28 days. We present recently obtained results and a short description of the ISTS apparatus.

WEPAC33	Results of the New High Power Tests of Superconducting Photonic Band Gap Structure Cells	850
	E.I. Simakov, S. Arsenyev, W.B. Haynes, S.S. Kurennoy, D. C. Lizon, J.F. O'Hara, E.R. Olivas, D.Y. Shchegolkov, N.A. Suvorova, T. Tajima LANL, Los Alamos, New Mexico, USA S. Arsenyev MIT/PSFC, Cambridge, Massachusetts, USA C.H. Boulware, T.L. Grimm Niowave, Inc., Lansing, Michigan, USA
	Funding: This work is supported by the Department of Defense High Energy Laser Joint Technology Office through the Office of Naval Research. We present an update on the 2.1 GHz superconducting rf (SRF) photonic band gap (PBG) resonator experiment in Los Alamos. The new SRF PBG cell was designed with the particular emphasis on changing the shape of PBG rods to reduce the peak magnetic fields and at the same time to preserve its effectiveness for suppression of the higher order modes (HOMs). The new PBG cells have great potential for outcoupling long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. Using PBG structures in superconducting particle accelerators will allow operation at higher frequencies and moving forward to significantly higher beam luminosities thus leading towards a completely new generation of colliders for high energy physics. Here we report the results of our efforts to fabricate 2.1 GHz PBG cells with elliptical rods and to test them with high power in a liquid helium bath at the temperature of 2 Kelvin. The high gradient performance of the cells will be evaluated and the results will be compared to electromagnetic and thermal simulations.

THPAC23	Lifetime Study of Tungsten Filaments in an H⁻ Surface Convertor Ion Source	1190
	I. Draganić, J.F. O'Hara, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	The tungsten filaments are critical components that limit the lifetime of the H⁻ surface convertor ion source. Their finite lifetime has a huge impact on the maintenance schedules and overall availability of an accelerator facility. We present in this work a simple analytical filament lifetime model and 3D thermal simulation explaining basic phenomena of filament erosion and electrical resistance changes during a normal run of an H⁻ production ion source at the Los Alamos Neutron Science Center (LANSCE). The calculation of filament longitudinal temperature profile takes into consideration the effects of ohmic heating, thermal conductivity and total emissivity for tungsten wires in high vacuum. The simulation includes the DC voltage operation of the filament with and without pulsed arc discharge current and gives the differential filament resistance changes, metal evaporation rates and theoretical electron emission currents. The results of the computation are compared with observed experimental data recorded using the EPICS control system during a normal LANSCE production cycle of 28 days with pulse repetition of 60 Hz and duty factor of 5%.

Paper

Title

Page

Status of the LANSCE Front-End Upgrade

327

R.W. Garnett, Y.K. Batygin, I. Draganić, C.M. Fortgang, S.S. Kurennoy, R.C. McCrady, J.F. O'Hara, R.J. Roybal, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA
J. Haeuser
Kress GmbH, Biebergemuend, Germany
A. Schempp
IAP, Frankfurt am Main, Germany

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396
Initial acceleration of the beams in the LANSCE linear accelerator at Los Alamos National Laboratory is still presently accomplished through the use of two 750-keV Cockcroft-Walton (CW) based injectors. To reduce long-term operational risks and to realize future beam performance goals, plans are underway to replace the existing H⁺ CW injector with a modern replacement, 4-rod Radio-Frequency Quadrupole (RFQ) based front end. Significant technical progress has been made since we last reported on this project. Status and progress of the design and fabrication of the RFQ, the RF system, beam transports, and integrated accelerator test stand will be discussed.

MOPSM05

Diagnostics for the LANSCE RFQ Front-End Test Stand

354

R.C. McCrady, Y.K. Batygin, I. Draganić, C.M. Fortgang, R.W. Garnett, S.S. Kurennoy, J.F. O'Hara, E.R. Olivas, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Plans are underway at the Los Alamos Neutron Science Center to replace the existing H⁺ Cockcroft-Walton injector with a modern 4-rod Radio-Frequency Quadrupole (RFQ) based front end. This will provide protons for injection into the downstream linac, where H⁻ ions are also accelerated. This dual-species operation of the linac imposes constraints on the injectors, resulting in particular requirements on the transverse and longitudinal emittances and phase-space distributions of the beam from the RFQ proton injector. Good measurements of these quantities are therefore required during the testing phase of the RFQ injector. In this paper we describe the measurements to be made and plans for the systems for carrying out the measurements.

TUPSM16

Progress Report of H⁻ Ion Beam Production at the LANL Ion Source Test Stand

667

I. Draganić, Y.K. Batygin, C.M. Fortgang, R.W. Garnett, J.G. Gioia, S.S. Kurennoy, R.C. McCrady, J.F. O'Hara, G. Rouleau, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

As part of the Los Alamos Neutron Science Center (LANSCE) the Ion Source Test Stand (ISTS) is a flexible, stand-alone facility used for H⁻ ion beam source development and studies of low energy beam transport. It consists of a surface convertor ion source with a multi-cusp permanent-magnet plasma confinement structure, an 80-kV high-voltage electrostatic extraction column, a low-energy ion beam transport line, and beam phase-space diagnostics. After resolving several technical issues, the ISTS was successfully restarted during the summer of 2012. Since then we have performed several long duration experiments. A development program is ongoing with the goals of improving source performance (reliability, availability, increased current, etc.) and beam transport efficiency (beam neutralization at low energy, beam dynamics with/without noble gas injection, etc.). Several enhancements to performance are being investigated in order to achieve a forthcoming upgrade requirement of LANSCE operations in 2014: beam current of 16-18 mA, 120-Hz operation at a duty factor of 10% and a source lifetime of 28 days. We present recently obtained results and a short description of the ISTS apparatus.

WEPAC33

Results of the New High Power Tests of Superconducting Photonic Band Gap Structure Cells

850

E.I. Simakov, S. Arsenyev, W.B. Haynes, S.S. Kurennoy, D. C. Lizon, J.F. O'Hara, E.R. Olivas, D.Y. Shchegolkov, N.A. Suvorova, T. Tajima
LANL, Los Alamos, New Mexico, USA
S. Arsenyev
MIT/PSFC, Cambridge, Massachusetts, USA
C.H. Boulware, T.L. Grimm
Niowave, Inc., Lansing, Michigan, USA

Funding: This work is supported by the Department of Defense High Energy Laser Joint Technology Office through the Office of Naval Research.
We present an update on the 2.1 GHz superconducting rf (SRF) photonic band gap (PBG) resonator experiment in Los Alamos. The new SRF PBG cell was designed with the particular emphasis on changing the shape of PBG rods to reduce the peak magnetic fields and at the same time to preserve its effectiveness for suppression of the higher order modes (HOMs). The new PBG cells have great potential for outcoupling long-range wakefields in SRF accelerator structures without affecting the fundamental accelerating mode. Using PBG structures in superconducting particle accelerators will allow operation at higher frequencies and moving forward to significantly higher beam luminosities thus leading towards a completely new generation of colliders for high energy physics. Here we report the results of our efforts to fabricate 2.1 GHz PBG cells with elliptical rods and to test them with high power in a liquid helium bath at the temperature of 2 Kelvin. The high gradient performance of the cells will be evaluated and the results will be compared to electromagnetic and thermal simulations.

THPAC23

Lifetime Study of Tungsten Filaments in an H⁻ Surface Convertor Ion Source

1190

I. Draganić, J.F. O'Hara, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

The tungsten filaments are critical components that limit the lifetime of the H⁻ surface convertor ion source. Their finite lifetime has a huge impact on the maintenance schedules and overall availability of an accelerator facility. We present in this work a simple analytical filament lifetime model and 3D thermal simulation explaining basic phenomena of filament erosion and electrical resistance changes during a normal run of an H⁻ production ion source at the Los Alamos Neutron Science Center (LANSCE). The calculation of filament longitudinal temperature profile takes into consideration the effects of ohmic heating, thermal conductivity and total emissivity for tungsten wires in high vacuum. The simulation includes the DC voltage operation of the filament with and without pulsed arc discharge current and gives the differential filament resistance changes, metal evaporation rates and theoretical electron emission currents. The results of the computation are compared with observed experimental data recorded using the EPICS control system during a normal LANSCE production cycle of 28 days with pulse repetition of 60 Hz and duty factor of 5%.