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| MOCO-A02 |
Status Report and Recent Developments with VENUS
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2 |
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- D. Leitner, J. Y. Benitez, D. R. Dietderich, R. Hannaford, M. Leitner, C. M. Lyneis, S. Prestemon, D. S. Todd
LBNL, Berkeley, California
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Since the superconducting ECR ion source VENUS started operation with 28 GHz microwave heating in 2004, it has produced record ion beam intensities such as 860 euA of Ar12+, 200 euA of U34+, or in respect to high charge state ions, 270 euA of Ar16+, 1 euA of Ar18+ and .4 euA of Xe42+. In August of 2006 VENUS has been connected to the 88-Inch Cyclotron as the third injector ion source extending the energy range and available heavy ion beam intensities from the cyclotron. This paper will highlight recent developments and results. In addition, the paper will give an update on the ongoing VENUS repair. Following an unexpected quench in January of 2008, the sextupole coils could not be energized. Most likely the quench was caused by the loss of liquid helium in the upper cryostat, which resulted in localized heating of the lead wire and consequent quenching. After opening the cryostat, it was found that one of the current carrying leads of the sextupole magnet was burned. The wire damage made it necessary to open the cold mass and extract the coil assembly for the repair. An update on the major undertaking of repairing the VENUS magnet and rebuilding the cryostat will be presented.
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Slides
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| MOPO-08 |
High Energy Component of X-Ray Spectra in ECR Ion Sources
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77 |
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- J. Y. Benitez, D. Leitner, C. M. Lyneis, J. D. Noland, D. S. Todd
LBNL, Berkeley, California
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The 88-Inch Cyclotron at LBNL is home to three powerful ECR ion sources, which operate at a range of heating frequencies from 6.4GHz for the ECR to a combination of 18GHz and 28GHz for the VENUS superconducting ECR. Over the last few years we have investigated the production of x-rays from ECR ion sources with the goal of improving the understanding of the electron energy distribution within these sources. By measuring the spectral temperatures (defined as the reciprocal of the slope of the semi-logarithmic plot of the x-ray energy spectra) and using them as relative indicators of the electron temperatures, different plasma conditions and tuning parameters can be evaluated. A comparison of the axial x-ray spectra measured with the 6.4 GHz ECR ion source to spectra obtained using the 18 and 28GHz VENUS source at equivalent power densities will be presented. In addition, the paper will discuss the experimental setup and analysis of the x-ray measurements. In particular, we will discuss how to remove artifacts from the energy spectra resulting from the interaction of x-rays with the detector in order to accurately represent the x-rays emitted from the source.
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| TUCO-A01 |
Conceptual Design of a 56 GHz ECR Ion Source Magnet Structure
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127 |
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- C. M. Lyneis, S. Caspi, P. Ferracin, D. Leitner, S. Prestemon, G. L. Sabbi, D. S. Todd, F. Trillaud
LBNL, Berkeley, California
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Funding: This work was supported by the Director, Office of Science, OFfice of High Energy and Nuclear Physics, Division of Nuclear Physics, US Department of Energy under Contract No. DE-AC02-05CH11231.
The development of a 4th Generation ECR ion source, which could operate at 56 GHz twice that of 3rd Generation sources, presents several technical challenges.* The greatest challenge is to produce a magnet structure with sufficient field strength to adequately confine the plasma. A design study is underway to determine the feasibility and engineering issues associated with a magnet structure that could produce 8 T at injection, 6 T at extraction and 4 T radially. The initial analysis shows that peak fields in the superconductor would be roughly 12 to 14 T and this is above Bc2 for NbTi but less than Bc2 for Nb3Sn. We are evaluating two possible designs; the classic design, where the sextupole coils are places inside the solenoids and the inverted design where the sextupole is placed outside the solenoid magnets. The preliminary results of the ongoing study are being presented and discussed.
* Claude M Lyneis, D. Leitner, D. S. Todd, G. Sabbi, S. Prestemon, S Caspi and P. Ferracin, Rev. Sci. Instrum. 79, 02A321 (2008)
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| THCO-B03 |
Improved ECR Extraction and Transport Simulations Using Experimentally Measured Plasma Sputtering
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219 |
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- D. S. Todd, D. Leitner, C. M. Lyneis
LBNL, Berkeley, California
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Funding: Work supported by the Director, Office of Energy Research, Office of High Energy & Nuclear Physics, Nuclear Physics Division of the U. S. Department of Energy under Contract DE AC03-76SF00098.
Simulations of beam extraction across a plasma sheath in an ECR ion source are critically dependent upon ion density distributions at the plasma extracting face; however, these distributions have not been measured experimentally. We present a new method of defining the initial distributions for simulation based upon the measurement of biased disc sputter marks. Multi-species beam extraction and transport simulations using these initial conditions will be compared with beam imaging and emittance measurements from the superconducting ECR VENUS at several positions along the beam line illustrating this simple model's ability to reproduce measured beam characteristics such as beam hollowing even though the triangular distributions at plasma extraction are of nearly constant density. The various possible sources of the beam hollowing observed both in simulation and experiment will be discussed. In addition, we will present a generalized method to define the initial distribution at extraction using only magnetic field line tracing and extracting aperture geometry.
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