2011 Particle Accelerator Conference - Classification: Sources and Medium Energy Accelerators / Tech 12: Injection, Extraction, and Transport

Paper	Title	Page
WEP267	Estimates of the Number of Foil Hits for Charge Exchange Injection	1975
	D. Raparia BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. For high intensity circular proton machines, one of the major limitations is the charge exchange injection foil. The number of foil hits due to circulating beam may cause the foil to fail and cause radiation due to multiple nuclear scattering and energy straggling. This paper will describe methods to estimate these quantities without going through lengthy simulations.

WEP283	Simulations of Transverse Stacking in the NSLS-II Booster	2014
	R.P. Fliller, T.V. Shaftan BNL, Upton, Long Island, New York, USA
	Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme. We show that the booster lattice has sufficient orbit correction and dynamic aperture at injection to maintain the charge and emittance of the first beam while it circulates waiting for the next train to arrive. We also show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature.

WEP290	A Novel Electron Gun for Off-axis Beam Injection	2029
	Yu.A. Kubyshin UPC, Barcelona, Spain A.V. Aloev, N.I. Pakhomov, V.I. Shvedunov MSU, Moscow, Russia
	For certain type of electron accelerators injection from an off-axis cathode is required. This is the case of a race-track microtron (RTM), in which the beam passes several times through the accelerating structure, or of a high power standing wave electron linac, for which the lifetime of an on-axis cathode would be strongly reduced by the electron back-bombardment. The standard solution with the beam injection via a dipole magnet from an electron gun placed off-axis is too bulky, moreover in case of RTMs it requires special compensating dipoles. An annular ring cathode gun used in some accelerators leads to large beam emittance and divergence. As a new solution we describe a 3D on-axis electron gun with an off-axis cathode and a central hole for the beam passage. Results of the design optimization and performance of an electron gun built for a miniature 12 MeV RTM for medical applications are presented. We also discuss results of the beam parameters measurements and estimates of the beam emittance.

WEP293	Design and Fabrication of the Lithium Beam Ion Injector for NDCX-II	2032
	J.H. Takakuwa, J.-Y. Jung, J.T. Kehl, J.W. Kwan, M. Leitner, P.A. Seidl, W.L. Waldron LBNL, Berkeley, California, USA A. Friedman, D.P. Grote, W. M. Sharp LLNL, Livermore, California, USA
	Funding: This work is performed under the auspices of the U.S. Department of Energy by LBNL under contract DE-AC02-05CH11231. A 130 keV injector is developed for the NDCX-II facility. It consists of a 10.9 cm diameter lithium doped alumina-silicate ion source heated to ~1300 °C and 3 electrodes. Other components include a segmented Rogowski coil for current and beam position monitoring, a gate valve, pumping ports, a focusing solenoid, a steering coil and space for inspection and maintenance access. Significant design challenges including managing the 3-4 kW of power dissipation from the source heater, temperature uniformity across the emitter surface, quick access for frequent ion source replacement, mechanical alignment with tight tolerance, and structural stabilization of the cantilevered 27” OD graded HV ceramic column. The injector fabrication is scheduled to complete by May 2011, and assembly and installation is scheduled to complete by the beginning of July.

WEP295	Status of Laser Stripping at the SNS	2035
	T.V. Gorlov, A.V. Aleksandrov, V.V. Danilov ORNL, Oak Ridge, Tennessee, USA Y. Liu ORNL RAD, Oak Ridge, Tennessee, USA
	Funding: This work was supported by SNS through UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy. This paper presents an overview of experimental and theoretical studies on laser stripping that have been conducted up to the present time in the SNS project. The goal of this work is to develop techniques to achieve the experimental preconditions necessary for the successful realization of a future intermediate experiment on laser stripping. The experimental work consists of the tuning and measurement of H־ beam parameters in readiness for the intermediate experiment, and also takes into account the features and possibilities of the SNS accelerator.

WEP296	Effects of Errors of Velocity Tilt on Maximum Longitudinal Compression During Neutralized Drift Compression of Intense Beam Pulses	2038
	I. Kaganovich, R.C. Davidson, E. Startsev PPPL, Princeton, New Jersey, USA A. Friedman LLNL, Livermore, California, USA S. Massidda Columbia University, New York, USA
	Funding: Research supported by the U.S. Department of Energy. Neutralized drift compression offers an effective means for particle beam focusing and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt is applied to the beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam intensity can increase more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limits the maximum longitudinal compression. It is found in general that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, part of pulse where the errors are small may compress to much higher values determined by the initial thermal spread of the beam pulse. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied.

Paper

Title

Page

Estimates of the Number of Foil Hits for Charge Exchange Injection

1975

D. Raparia
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
For high intensity circular proton machines, one of the major limitations is the charge exchange injection foil. The number of foil hits due to circulating beam may cause the foil to fail and cause radiation due to multiple nuclear scattering and energy straggling. This paper will describe methods to estimate these quantities without going through lengthy simulations.

WEP283

Simulations of Transverse Stacking in the NSLS-II Booster

2014

R.P. Fliller, T.V. Shaftan
BNL, Upton, Long Island, New York, USA

Funding: This manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster. The linac needs to deliver 15 nC in 80 - 150 bunches to the booster every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source. We have developed a scheme to transversely stack two bunch trains in the NSLS-II booster in order to alleviate the charge requirements on the linac. This scheme has been outlined previously. In this paper we show particle tracking simulations of the tracking scheme. We show that the booster lattice has sufficient orbit correction and dynamic aperture at injection to maintain the charge and emittance of the first beam while it circulates waiting for the next train to arrive. We also show simulations of the booster ramp with a stacked beam for a variety of lattice errors and injected beam parameters. In all cases the performance of the proposed stacking method is sufficient to reduce the required charge from the linac. For this reason the injection system of the NSLS-II booster is being designed to include this feature.

WEP290

A Novel Electron Gun for Off-axis Beam Injection

2029

Yu.A. Kubyshin
UPC, Barcelona, Spain
A.V. Aloev, N.I. Pakhomov, V.I. Shvedunov
MSU, Moscow, Russia

For certain type of electron accelerators injection from an off-axis cathode is required. This is the case of a race-track microtron (RTM), in which the beam passes several times through the accelerating structure, or of a high power standing wave electron linac, for which the lifetime of an on-axis cathode would be strongly reduced by the electron back-bombardment. The standard solution with the beam injection via a dipole magnet from an electron gun placed off-axis is too bulky, moreover in case of RTMs it requires special compensating dipoles. An annular ring cathode gun used in some accelerators leads to large beam emittance and divergence. As a new solution we describe a 3D on-axis electron gun with an off-axis cathode and a central hole for the beam passage. Results of the design optimization and performance of an electron gun built for a miniature 12 MeV RTM for medical applications are presented. We also discuss results of the beam parameters measurements and estimates of the beam emittance.

WEP293

Design and Fabrication of the Lithium Beam Ion Injector for NDCX-II

2032

J.H. Takakuwa, J.-Y. Jung, J.T. Kehl, J.W. Kwan, M. Leitner, P.A. Seidl, W.L. Waldron
LBNL, Berkeley, California, USA
A. Friedman, D.P. Grote, W. M. Sharp
LLNL, Livermore, California, USA

Funding: This work is performed under the auspices of the U.S. Department of Energy by LBNL under contract DE-AC02-05CH11231.
A 130 keV injector is developed for the NDCX-II facility. It consists of a 10.9 cm diameter lithium doped alumina-silicate ion source heated to ~1300 °C and 3 electrodes. Other components include a segmented Rogowski coil for current and beam position monitoring, a gate valve, pumping ports, a focusing solenoid, a steering coil and space for inspection and maintenance access. Significant design challenges including managing the 3-4 kW of power dissipation from the source heater, temperature uniformity across the emitter surface, quick access for frequent ion source replacement, mechanical alignment with tight tolerance, and structural stabilization of the cantilevered 27” OD graded HV ceramic column. The injector fabrication is scheduled to complete by May 2011, and assembly and installation is scheduled to complete by the beginning of July.

WEP295

Status of Laser Stripping at the SNS

2035

T.V. Gorlov, A.V. Aleksandrov, V.V. Danilov
ORNL, Oak Ridge, Tennessee, USA
Y. Liu
ORNL RAD, Oak Ridge, Tennessee, USA

Funding: This work was supported by SNS through UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy.
This paper presents an overview of experimental and theoretical studies on laser stripping that have been conducted up to the present time in the SNS project. The goal of this work is to develop techniques to achieve the experimental preconditions necessary for the successful realization of a future intermediate experiment on laser stripping. The experimental work consists of the tuning and measurement of H־ beam parameters in readiness for the intermediate experiment, and also takes into account the features and possibilities of the SNS accelerator.

WEP296

Effects of Errors of Velocity Tilt on Maximum Longitudinal Compression During Neutralized Drift Compression of Intense Beam Pulses

2038

I. Kaganovich, R.C. Davidson, E. Startsev
PPPL, Princeton, New Jersey, USA
A. Friedman
LLNL, Livermore, California, USA
S. Massidda
Columbia University, New York, USA

Funding: Research supported by the U.S. Department of Energy.
Neutralized drift compression offers an effective means for particle beam focusing and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt is applied to the beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam intensity can increase more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limits the maximum longitudinal compression. It is found in general that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, part of pulse where the errors are small may compress to much higher values determined by the initial thermal spread of the beam pulse. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied.