ECRIS2012 - List of Authors (Lyneis, C.M.)

Paper

Title

Page

Coupling Microwave Power into ECR Ion Source Plasmas at Frequencies above 20 GHz

1

C.M. Lyneis, J.Y. Benitez, M.M. Strohmeier, D.S. Todd
LBNL, Berkeley, California, USA

Electron Cyclotron Resonance (ECR) ion sources have been built to operate at frequencies from 5 GHz to 28 GHz and typically use a plasma chamber that serves as a multi-mode cavity. For small sources operating at 6 to 14 GHz cavity mode-like behavior has been reported. In these cavities the vacuum mode density is low enough that it may be that the RF power distribution can be understood in terms of excitation of a few modes. The large superconducting ECR ion sources, such as VENUS, operating at higher frequencies have a much greater mode density and very strong damping from plasma microwave adsorption. In this type of source, how the RF is launched into the plasma chamber will strongly affect the microwave coupling and the chamber walls will be less important. The VENUS source uses round over-moded TE01 mode waveguide to couple to the plasma, while most modern fusion devices use quasi-gaussian HE11 waves for injection into plasmas. In this paper we will describe the potential advantages of applying this technology to superconducting ECR ion sources as well as designs for doing so with VENUS.

Slides TUXO01 [18.302 MB]

TUXO02

An Experimental Study of ECRIS Plasma Stability and Oscillation of Beam Current

5

O.A. Tarvainen, T. Kalvas, H. A. Koivisto, J.P.O. Komppula, V. Toivanen
JYFL, Jyväskylä, Finland
C.M. Lyneis, M.M. Strohmeier
LBNL, Berkeley, California, USA

The stability of oxygen ion beams extracted from ECR ion sources has been studied with the superconducting ion source VENUS at LBNL and with the A-ECR type 14 GHz ECRIS at JYFL. Discrete Fourier transform has been used for characterizing beam current oscillations in kHz range exhibited by both ion sources. The effect of source parameters on the frequency and amplitude of the oscillations is discussed. It was found that double frequency heating affects the oscillation frequency, biased disc can be used to mitigate the amplitude of beam current fluctuations, increasing B-minimum results to pronounced instabilities and operating the ion source with significantly higher mirror ratio than suggested by ECRIS scaling laws yields the most stable ion beams. It is argued that the observed beam current fluctuations are correlated with plasma instabilities. A 'roadmap' for identifying the plasma instability mechanisms responsible for beam current fluctuations is presented.

Slides TUXO02 [2.195 MB]

THXO02

Current Developments of the VENUS Ion Source in Research and Operations

153

J.Y. Benitez, K.Y. Franzen, C.M. Lyneis, L. Phair, M.M. Strohmeier
LBNL, Berkeley, California, USA
G. Machicoane
FRIB, East Lansing, Michigan, USA
L.T. Sun
IMP, Lanzhou, People's Republic of China

The VENUS ion source functions as a research and development tool in the ECR community as well as an injector for LBNL's 88-Inch cyclotron. In order to meet the needs of both the ECR community and users at the 88-Inch cyclotron, technology such as ovens and a sputter probe have been developed for introducing metals into the plasma. Using a modified high temperature oven, VENUS has produced 450 eμA of ²³⁸U³³⁺ and 400 eμA of ²³⁸U³⁴⁺, twice the required Uranium beam current needed for FRIB. In addition, after upgrading its high voltage capabilities VENUS produced 11emA of ⁴He²⁺, a capability that remains unparalleled by other ECR ion sources. In addition to its recent record high intensities VENUS is also being developed to deliver low intensity, ultra high charge state ions for the cocktails beams, where many species are produced simultaneously for use by the BASE Facility. ¹²⁴Xe⁴³⁺ is now in regular production for the 16 MeV/u cocktail, and development of ²⁰⁹Bi⁵⁶⁺ for the 10 MeV/u cocktail is in progress and has been accelerated through the 88-Inch cyclotron. This paper presents the latest work towards integrating the VENUS ion source into our research and operational goals.

Slides THXO02 [8.391 MB]

THYO03

Design Status of ECR Ion Sources and LEBT for FRIB

172

G. Machicoane, N.K. Bultman, G. Morgan, E. Pozdeyev, X. Rao
FRIB, East Lansing, Michigan, USA
J.Y. Benitez, C.M. Lyneis
LBNL, Berkeley, California, USA
L.T. Sun
IMP, Lanzhou, People's Republic of China

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
The Facility for Rare Isotope Beams at Michigan State University is currently being designed and will provide intense beams of rare isotopes for research in nuclear physics, nuclear astrophysics and study of fundamental interactions. The FRIB driver linac will accelerate all stable isotopes from Oxygen to Uranium to energies beyond 200 MeV/u at beam powers up to 400 kW. In the case of Uranium about 13.3 pμA of U³³⁺ are required from the ion source to reach the maximum beam power on the target. Such current is at the limit of what an ECR ion source can produce and led us to design the FRIB driver linac to accelerate concurrently two charges. The ECR ion source for FRIB will be based on the VENUS ion source developed at Lawrence Berkeley National Laboratory (LBNL). Recent beam measurements done with VENUS have demonstrated that the ion source can actually produce close to 13pμA of U³³⁺ and therefore could possibly meet the current required for FRIB in one charge state. This paper reviews the status of the FRIB ECR ion source and the modifications that have been made to the VENUS ion source design. The Low energy beam line transport (LEBT) will also be presented and discussed.

Slides THYO03 [6.532 MB]

Paper	Title	Page
TUXO01	Coupling Microwave Power into ECR Ion Source Plasmas at Frequencies above 20 GHz	1
	C.M. Lyneis, J.Y. Benitez, M.M. Strohmeier, D.S. Todd LBNL, Berkeley, California, USA
	Electron Cyclotron Resonance (ECR) ion sources have been built to operate at frequencies from 5 GHz to 28 GHz and typically use a plasma chamber that serves as a multi-mode cavity. For small sources operating at 6 to 14 GHz cavity mode-like behavior has been reported. In these cavities the vacuum mode density is low enough that it may be that the RF power distribution can be understood in terms of excitation of a few modes. The large superconducting ECR ion sources, such as VENUS, operating at higher frequencies have a much greater mode density and very strong damping from plasma microwave adsorption. In this type of source, how the RF is launched into the plasma chamber will strongly affect the microwave coupling and the chamber walls will be less important. The VENUS source uses round over-moded TE01 mode waveguide to couple to the plasma, while most modern fusion devices use quasi-gaussian HE11 waves for injection into plasmas. In this paper we will describe the potential advantages of applying this technology to superconducting ECR ion sources as well as designs for doing so with VENUS.
	Slides TUXO01 [18.302 MB]

TUXO02	An Experimental Study of ECRIS Plasma Stability and Oscillation of Beam Current	5
	O.A. Tarvainen, T. Kalvas, H. A. Koivisto, J.P.O. Komppula, V. Toivanen JYFL, Jyväskylä, Finland C.M. Lyneis, M.M. Strohmeier LBNL, Berkeley, California, USA
	The stability of oxygen ion beams extracted from ECR ion sources has been studied with the superconducting ion source VENUS at LBNL and with the A-ECR type 14 GHz ECRIS at JYFL. Discrete Fourier transform has been used for characterizing beam current oscillations in kHz range exhibited by both ion sources. The effect of source parameters on the frequency and amplitude of the oscillations is discussed. It was found that double frequency heating affects the oscillation frequency, biased disc can be used to mitigate the amplitude of beam current fluctuations, increasing B-minimum results to pronounced instabilities and operating the ion source with significantly higher mirror ratio than suggested by ECRIS scaling laws yields the most stable ion beams. It is argued that the observed beam current fluctuations are correlated with plasma instabilities. A 'roadmap' for identifying the plasma instability mechanisms responsible for beam current fluctuations is presented.
	Slides TUXO02 [2.195 MB]

THXO02	Current Developments of the VENUS Ion Source in Research and Operations	153
	J.Y. Benitez, K.Y. Franzen, C.M. Lyneis, L. Phair, M.M. Strohmeier LBNL, Berkeley, California, USA G. Machicoane FRIB, East Lansing, Michigan, USA L.T. Sun IMP, Lanzhou, People's Republic of China
	The VENUS ion source functions as a research and development tool in the ECR community as well as an injector for LBNL's 88-Inch cyclotron. In order to meet the needs of both the ECR community and users at the 88-Inch cyclotron, technology such as ovens and a sputter probe have been developed for introducing metals into the plasma. Using a modified high temperature oven, VENUS has produced 450 eμA of ²³⁸U³³⁺ and 400 eμA of ²³⁸U³⁴⁺, twice the required Uranium beam current needed for FRIB. In addition, after upgrading its high voltage capabilities VENUS produced 11emA of ⁴He²⁺, a capability that remains unparalleled by other ECR ion sources. In addition to its recent record high intensities VENUS is also being developed to deliver low intensity, ultra high charge state ions for the cocktails beams, where many species are produced simultaneously for use by the BASE Facility. ¹²⁴Xe⁴³⁺ is now in regular production for the 16 MeV/u cocktail, and development of ²⁰⁹Bi⁵⁶⁺ for the 10 MeV/u cocktail is in progress and has been accelerated through the 88-Inch cyclotron. This paper presents the latest work towards integrating the VENUS ion source into our research and operational goals.
	Slides THXO02 [8.391 MB]

THYO03	Design Status of ECR Ion Sources and LEBT for FRIB	172
	G. Machicoane, N.K. Bultman, G. Morgan, E. Pozdeyev, X. Rao FRIB, East Lansing, Michigan, USA J.Y. Benitez, C.M. Lyneis LBNL, Berkeley, California, USA L.T. Sun IMP, Lanzhou, People's Republic of China
	Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 The Facility for Rare Isotope Beams at Michigan State University is currently being designed and will provide intense beams of rare isotopes for research in nuclear physics, nuclear astrophysics and study of fundamental interactions. The FRIB driver linac will accelerate all stable isotopes from Oxygen to Uranium to energies beyond 200 MeV/u at beam powers up to 400 kW. In the case of Uranium about 13.3 pμA of U³³⁺ are required from the ion source to reach the maximum beam power on the target. Such current is at the limit of what an ECR ion source can produce and led us to design the FRIB driver linac to accelerate concurrently two charges. The ECR ion source for FRIB will be based on the VENUS ion source developed at Lawrence Berkeley National Laboratory (LBNL). Recent beam measurements done with VENUS have demonstrated that the ion source can actually produce close to 13pμA of U³³⁺ and therefore could possibly meet the current required for FRIB in one charge state. This paper reviews the status of the FRIB ECR ion source and the modifications that have been made to the VENUS ion source design. The Low energy beam line transport (LEBT) will also be presented and discussed.
	Slides THYO03 [6.532 MB]