ECRIS2010 - List of Authors (Strohmeier, M.M.)

Paper

Title

Page

Plasma-to-Target WARP Simulations of Uranium Beams Extracted from VENUS Compared to Emittance Measurements and Beam Images

81

D. Winklehner, J.Y. Benitez, D. Leitner, M.M. Strohmeier, D.S. Todd
LBNL, Berkeley, California, USA
D.P. Grote
LLNL, Livermore, California, USA

The superconducting ECR ion source VENUS was built as injector for the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL) and as prototype injector for the Facility for Rare Isotope Beams (FRIB) in Michigan. This work presents the latest results of an ongoing effort to simulate both, the extraction from ECR ion sources, and the Low Energy Beam Transport (LEBT). Its aim is to help understand the influence of parameters like initial ion distributions at the extraction aperture, ion temperatures and beam neutralization on the quality of the beam and to provide a design-tool for increasing the efficiency of the extraction- and transport-system. The initial conditions (i.e. spatial- and velocity-distribution of the ions prior to extraction from the ion source) are obtained semi-empirically by tracking the ions of different species from sputter marks on the biased disk on the far end of the source to the extraction region by following the magnetic field lines and scaling the Larmor radii of the ions appropriately. Extraction from the plasma and consequently the source is then simulated with the versatile WARP simulation code. The same code is also used for the actual simulation of ion transport through the beam line. Simulations of multi-species Uranium beams with different drain currents, initial ion temperatures and levels of neutralization in the beam line are compared to each other and to emittance measurements and beam profiles of VENUS beams.

Slides TUCOAK03 [2.382 MB]

WECOAK01

Characterization of the Microwave Coupling to the Plasma Chamber of the LBL ECR Ion Source.

162

C.M. Lyneis, J.Y. Benitez, D. Leitner, J.D. Noland, M.M. Strohmeier
LBNL, Berkeley, California, USA
H. A. Koivisto, O.A. Tarvainen
JYFL, Jyväskylä, Finland

The characteristics of the microwave coupling of the 6.4 GHz ECR ion source were measured as a function of frequency, input power and time dependence. In addition the plasma diamagnetism and bremsstrahlung could be measured to help quantify the time dependence of the plasma build up and energy content. The LBL ECR plasma chamber, which has a diameter to wavelength ratio of 1.9 is not as over-moded as the 14 GHz AECR-U, which has a ratio greater than 3. This makes it possible to locate frequencies, where a single RF mode is predominately excited. For one of these modes we were able to demonstrate that with no plasma in the cavity, it is over-coupled and as the power is increased, the plasma density rises and the plasma loading increases it becomes under-coupled. By measuring the ratio of the incident to reflected power it is possible to show the microwave electric field levels saturate with increasing power. In the paper, the time dependence of the plasma loading and plasma diamagnetism as a function of input power and time are analyzed. The measurements of the plasma loading also provide insight into the dynamics of microwave heating in a multimode cavity.

Slides WECOAK01 [1.593 MB]

Paper	Title	Page
TUCOAK03	Plasma-to-Target WARP Simulations of Uranium Beams Extracted from VENUS Compared to Emittance Measurements and Beam Images	81
	D. Winklehner, J.Y. Benitez, D. Leitner, M.M. Strohmeier, D.S. Todd LBNL, Berkeley, California, USA D.P. Grote LLNL, Livermore, California, USA
	The superconducting ECR ion source VENUS was built as injector for the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL) and as prototype injector for the Facility for Rare Isotope Beams (FRIB) in Michigan. This work presents the latest results of an ongoing effort to simulate both, the extraction from ECR ion sources, and the Low Energy Beam Transport (LEBT). Its aim is to help understand the influence of parameters like initial ion distributions at the extraction aperture, ion temperatures and beam neutralization on the quality of the beam and to provide a design-tool for increasing the efficiency of the extraction- and transport-system. The initial conditions (i.e. spatial- and velocity-distribution of the ions prior to extraction from the ion source) are obtained semi-empirically by tracking the ions of different species from sputter marks on the biased disk on the far end of the source to the extraction region by following the magnetic field lines and scaling the Larmor radii of the ions appropriately. Extraction from the plasma and consequently the source is then simulated with the versatile WARP simulation code. The same code is also used for the actual simulation of ion transport through the beam line. Simulations of multi-species Uranium beams with different drain currents, initial ion temperatures and levels of neutralization in the beam line are compared to each other and to emittance measurements and beam profiles of VENUS beams.
	Slides TUCOAK03 [2.382 MB]

WECOAK01	Characterization of the Microwave Coupling to the Plasma Chamber of the LBL ECR Ion Source.	162
	C.M. Lyneis, J.Y. Benitez, D. Leitner, J.D. Noland, M.M. Strohmeier LBNL, Berkeley, California, USA H. A. Koivisto, O.A. Tarvainen JYFL, Jyväskylä, Finland
	The characteristics of the microwave coupling of the 6.4 GHz ECR ion source were measured as a function of frequency, input power and time dependence. In addition the plasma diamagnetism and bremsstrahlung could be measured to help quantify the time dependence of the plasma build up and energy content. The LBL ECR plasma chamber, which has a diameter to wavelength ratio of 1.9 is not as over-moded as the 14 GHz AECR-U, which has a ratio greater than 3. This makes it possible to locate frequencies, where a single RF mode is predominately excited. For one of these modes we were able to demonstrate that with no plasma in the cavity, it is over-coupled and as the power is increased, the plasma density rises and the plasma loading increases it becomes under-coupled. By measuring the ratio of the incident to reflected power it is possible to show the microwave electric field levels saturate with increasing power. In the paper, the time dependence of the plasma loading and plasma diamagnetism as a function of input power and time are analyzed. The measurements of the plasma loading also provide insight into the dynamics of microwave heating in a multimode cavity.
	Slides WECOAK01 [1.593 MB]