PAC2013 - List of Authors (Draganic, I.N.)

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.

MOPMA17	Design Requirements and Expected Performance of the New LANSCE H⁺ RFQ	336
	L. Rybarcyk, Y.K. Batygin, I. Draganić, C.M. Fortgang, R.W. Garnett, S.S. Kurennoy, R.C. McCrady, T.P. Wangler LANL, Los Alamos, New Mexico, USA J. Haeuser Kress GmbH, Biebergemuend, Germany A. Schempp IAP, Frankfurt am Main, Germany
	LANSCE provides H⁻ and H⁺ beams to several user facilities for fundamental and applied research, including a 100-MeV, 250-μA proton beam to the Isotope Production facility (IPF). Each beam species is initially accelerated to 750 keV in separate Cockcroft-Walton (C-W) accelerators. Due to the age and possible failure modes of the C-W’s and the potential impact of a C-W failure to the IPF program, we have begun the process of replacing the aging H⁺ C-W with a modern Radio Frequency Quadrupole (RFQ) accelerator-based system. In addition, the complexity of combined species operations imposes further restrictions on the beam performance and configuration that must be incorporated into the design process. This paper will cover the physics design requirements of this new RFQ and the expected performance based upon the results of PARMTEQM simulations.

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.

TUPSM18	Design of a Duoplasmatron Extraction Geometry and LEBT for the LANSCE H⁺ RFQ Project	673
	C.M. Fortgang, Y.K. Batygin, I. Draganić, R.W. Garnett, R.C. McCrady, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	Funding: This work is supported by the U. S. Department of Energy, Contract DE-AC52-06NA25396. The 750 keV H⁺ Cockcroft-Walton at LANSCE will be replaced with a 4-rod RFQ with injection energy of 35 keV. The existing duoplasmatron source extraction optics need to be modified to produce up to 35 mA of H⁺ current with an emittance <0.02 pi-cm-mrad (rms,norm) for injection into the RFQ. In addition to source modifications we need a new LEBT for transport and matching into the RFQ. The LEBT uses 2 magnetic solenoids with enough drift space between them to accommodate diagnostics and a beam deflector. The LEBT is designed to work over a range of space-charge neutralized currents and emittances. The LEBT is optimized in the sense that it minimizes the beam size in both solenoids for a point design of a given neutralized current and emittance. Special attention has been given to estimating emittance growth due to solenoid aberrations. Examples of source-to-RFQ matching and emittance growth (due to both non-linear space charge and solenoid aberrations) are presented over a range of currents and emittances about the design point. A preliminary mechanical layout drawing will also be presented.

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.

MOPMA17

Design Requirements and Expected Performance of the New LANSCE H⁺ RFQ

336

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

LANSCE provides H⁻ and H⁺ beams to several user facilities for fundamental and applied research, including a 100-MeV, 250-μA proton beam to the Isotope Production facility (IPF). Each beam species is initially accelerated to 750 keV in separate Cockcroft-Walton (C-W) accelerators. Due to the age and possible failure modes of the C-W’s and the potential impact of a C-W failure to the IPF program, we have begun the process of replacing the aging H⁺ C-W with a modern Radio Frequency Quadrupole (RFQ) accelerator-based system. In addition, the complexity of combined species operations imposes further restrictions on the beam performance and configuration that must be incorporated into the design process. This paper will cover the physics design requirements of this new RFQ and the expected performance based upon the results of PARMTEQM simulations.

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.

TUPSM18

Design of a Duoplasmatron Extraction Geometry and LEBT for the LANSCE H⁺ RFQ Project

673

C.M. Fortgang, Y.K. Batygin, I. Draganić, R.W. Garnett, R.C. McCrady, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Funding: This work is supported by the U. S. Department of Energy, Contract DE-AC52-06NA25396.
The 750 keV H⁺ Cockcroft-Walton at LANSCE will be replaced with a 4-rod RFQ with injection energy of 35 keV. The existing duoplasmatron source extraction optics need to be modified to produce up to 35 mA of H⁺ current with an emittance <0.02 pi-cm-mrad (rms,norm) for injection into the RFQ. In addition to source modifications we need a new LEBT for transport and matching into the RFQ. The LEBT uses 2 magnetic solenoids with enough drift space between them to accommodate diagnostics and a beam deflector. The LEBT is designed to work over a range of space-charge neutralized currents and emittances. The LEBT is optimized in the sense that it minimizes the beam size in both solenoids for a point design of a given neutralized current and emittance. Special attention has been given to estimating emittance growth due to solenoid aberrations. Examples of source-to-RFQ matching and emittance growth (due to both non-linear space charge and solenoid aberrations) are presented over a range of currents and emittances about the design point. A preliminary mechanical layout drawing will also be presented.

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%.