IPAC2018 - List of Keywords (induction)

Paper	Title	Other Keywords	Page
THPAK045	Summary of Beam Operation Capability at FXR LIA	operation, cathode, electron, experiment	3316
	Y.H. Wu, J. Ellsworth LLNL, Livermore, California, USA
	Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344. In this paper we summarize the current beam operation capability of FXR linear induc-tion accelerator (LIA) at LLNL. Experi-mental measurements for electron beam pa-rameters at different beam operations are pre-sented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK045
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THPAK046	The Ion-Hose Instability in High-Current Multi-Pulse Induction Linacs	electron, simulation, vacuum, experiment	3320
	C. Ekdahl LANL, Los Alamos, New Mexico, USA
	The ion-hose instability has long been considered a danger for long-pulse, high-current electron linear induction accelerators (LIAs). This instability is enabled by beam-electron ionization of residual background gas in the accelerator. The space-charge of the high-energy beam ejects low-energy electrons from the ionized channel, leaving a positively-charged ion channel that attracts the electron beam. The beam can oscillate in the potential well around the channel position. Likewise, the electron beam attracts the ions, which can oscillate about the beam position. Because of the vast differences in particle mass, the oscillations are out of phase, and the amplitudes grow unstably. The number of instability e-foldings is proportional to the channel ion density, which in turn is proportional to the background pressure and pulse length. This scaling of the instability growth was demonstrated on the long-pulse DARHT-II linear induction accelerator (LIA) at Los Alamos*. The ion-hose instability is also problematic for high-current multi-pulse LIAs, because ion recombination times are so very long at typical background pressures. Moreover, because of low ion channel ion densities, and massive ions, channel expansion is too slow to reduce the instability growth by very much. In particular, the ion channel is expected to persist and its density to increase during the 3-microsecond duration of a four-pulse burst from the 2-kA, 20-MeV Scorpius LIA now being developed. Recent simulations with an experimentally validated code that was used to predict DARHT-II growth rates have shown that the magnetic focusing field designed for Scorpius will be strong enough to inhibit ion-hose instability if the background pressure is kept below a value that is readily attainable with the present designs of induction cells and other accelerator components. Details and results of these calculations are the subject of this presentation. H. L. Buchanan, Phys. Fluids, vol. 30, pp. 221 - 231, 1987 **C. A. Ekdahl, et al., IEEE Trans. Plasma Sci., vol. 34, pp. 460-466, 2006
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK046
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THPML006	Using Drive Rods in Inductions Cells to Reduce the Beam Break Up Instability	impedance, simulation, wakefield, cavity	4658
	N. Pogue, T.L. Houck, B.R. Poole LLNL, Livermore, California, USA
	The Beam Breakup Instability is a critical effect to reduce in high current induction accelerators. The RF modes generated inside the induction cells can deflect or degrade subsequent beam traversing the cell. Significant effort has been invested in minimizing the effect over several decades. One mechanism that is known to reduce the transverse impedance, the main observable experimentally which directly relates to the BBU amplitude, is to introduce ferrites to absorb the fields. Another, less investigated mechanism, is to disturb the modes symmetry by inserting the drive rods at the proper locations in the cell. This paper will show that the drive rods can dramatically reduce the transverse impedance, and will show that simulations are maturing towards predicting this effect. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML006
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Paper

Title

Other Keywords

Page

THPAK045

Summary of Beam Operation Capability at FXR LIA

operation, cathode, electron, experiment

3316

Y.H. Wu, J. Ellsworth
LLNL, Livermore, California, USA

Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52- 07NA27344.
In this paper we summarize the current beam operation capability of FXR linear induc-tion accelerator (LIA) at LLNL. Experi-mental measurements for electron beam pa-rameters at different beam operations are pre-sented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK045

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAK046

The Ion-Hose Instability in High-Current Multi-Pulse Induction Linacs

electron, simulation, vacuum, experiment

3320

C. Ekdahl
LANL, Los Alamos, New Mexico, USA

The ion-hose instability has long been considered a danger for long-pulse, high-current electron linear induction accelerators (LIAs)*. This instability is enabled by beam-electron ionization of residual background gas in the accelerator. The space-charge of the high-energy beam ejects low-energy electrons from the ionized channel, leaving a positively-charged ion channel that attracts the electron beam. The beam can oscillate in the potential well around the channel position. Likewise, the electron beam attracts the ions, which can oscillate about the beam position. Because of the vast differences in particle mass, the oscillations are out of phase, and the amplitudes grow unstably. The number of instability e-foldings is proportional to the channel ion density*, which in turn is proportional to the background pressure and pulse length. This scaling of the instability growth was demonstrated on the long-pulse DARHT-II linear induction accelerator (LIA) at Los Alamos**. The ion-hose instability is also problematic for high-current multi-pulse LIAs, because ion recombination times are so very long at typical background pressures. Moreover, because of low ion channel ion densities, and massive ions, channel expansion is too slow to reduce the instability growth by very much. In particular, the ion channel is expected to persist and its density to increase during the 3-microsecond duration of a four-pulse burst from the 2-kA, 20-MeV Scorpius LIA now being developed. Recent simulations with an experimentally validated code that was used to predict DARHT-II growth rates have shown that the magnetic focusing field designed for Scorpius will be strong enough to inhibit ion-hose instability if the background pressure is kept below a value that is readily attainable with the present designs of induction cells and other accelerator components. Details and results of these calculations are the subject of this presentation.
*H. L. Buchanan, Phys. Fluids, vol. 30, pp. 221 - 231, 1987
**C. A. Ekdahl, et al., IEEE Trans. Plasma Sci., vol. 34, pp. 460-466, 2006

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK046

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML006

Using Drive Rods in Inductions Cells to Reduce the Beam Break Up Instability

impedance, simulation, wakefield, cavity

4658

N. Pogue, T.L. Houck, B.R. Poole
LLNL, Livermore, California, USA

The Beam Breakup Instability is a critical effect to reduce in high current induction accelerators. The RF modes generated inside the induction cells can deflect or degrade subsequent beam traversing the cell. Significant effort has been invested in minimizing the effect over several decades. One mechanism that is known to reduce the transverse impedance, the main observable experimentally which directly relates to the BBU amplitude, is to introduce ferrites to absorb the fields. Another, less investigated mechanism, is to disturb the modes symmetry by inserting the drive rods at the proper locations in the cell. This paper will show that the drive rods can dramatically reduce the transverse impedance, and will show that simulations are maturing towards predicting this effect. Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML006

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)