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Title |
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| MOPO-14 |
Ion Beam Production from Rare Isotopes with GSI ECR Ion Sources
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97 |
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- K. Tinschert, R. Lang, J. Maeder, J. Rossbach, P. Spaedtke
GSI, Darmstadt
- A. Yakushev
Technische Universitat Munchen, Garching
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ECR ion sources (ECRIS) of CAPRICE-type, working at 14.5 GHz, are in use at the High Charge State Injector (HLI) of the accelerator facility at GSI for beam production and at a test bench for development work. The ECRIS is mostly used to produce ion beams from rare isotopes because of its high efficiency and low material consumption. Depending on their material properties beams of rare isotopes are produced from gases, gaseous compounds, solid materials or solid compounds. Gases can be used directly, while solids have to be transformed into the gaseous state for the ECR plasma which is achieved by using resistively heated ovens. As enriched materials are produced by isotopic separation processes their composition including contamination by impurities can be of importance for the handling in the evaporation process and can be detrimental for the beam user if the ion beam contains additional ion species. Characteristics and suitable treatment of materials and production processes will be described. Experimental investigations with different sample materials and operational experiences will be reported.
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| MOPO-18 |
Microwave Power Saving and Reduced Bremsstrahlung Emission for a High Charge State Ion Production in an ECRIS Equipped with MD Structures
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111 |
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- L. Schachter, S. Dobrescu
IFIN, Magurele- Bucuresti
- K. E. Stiebing
IKF, Frankfurt-am-Main
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Metal dielectric structures (MD) installed in the plasma chamber of the Frankfurt 14GHz electron cyclotron resonance ion source (ECRIS), have been used to significantly reduce the level of microwave power, necessary to create comparable ion intensities as for the standard operation of the Frankfurt ECRIS. The measurements indicate that the RF-power may be reduced by a factor of 2-3 to obtain the same output of high argon charge states as in the standard source with stainless steel plasma chamber. This reduced level of microwave power also leads to a much lower level of X-ray emission from the source.
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Poster
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| MOPO-21 |
Modeling ECRIS Plasma Using 2D GEM (General ECRIS Model)
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116 |
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- L. Zhao, B. Cluggish, J. S. Kim
Far-Tech, Inc., San Diego, California
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Funding: Work is supported by US DOE SBIR DE-FG02-04ER83954.
The GEM (General ECRIS Model) code is developed by FAR-TECH, Inc. to model plasmas in ECRIS devices using only experimental knobs such as magnetic field, rf and the geometry of the device. The code models ECRIS plasma electrons by the bounce-averaged Fokker-Planck equation, ions as fluid and neutrals by particle balancing. It has been extended to include 2D (axial and radial) spatial features such as 2D ECR heating and ion radial diffusion. The convergence and consistency of the code have been studied. It is parallelized using the MPI technique to boost the calculation speed. Examples of 2D profiles of ECRIS plasmas and the radial dependence of CSD (charge state distribution) will be presented. Also, GEM 2D is merged with the MCBC (Monte Carlo Beam Capture) code to optimize ECR charge breeders. Results of the GEM 2D code and comparisons of GEM 2D and GEM 1D results will be presented.
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Poster
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| TUCO-B03 |
On the Observation of Standing Waves in Cylindrical Cavities Filled by Microwave Discharge and ECR Plasmas
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140 |
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- L. Celona, G. Ciavola, N. Gambino, S. Gammino, F. Maimone, D. Mascali, R. Miracoli
INFN/LNS, Catania
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Experimental measurements of the scattering parameters carried out in microwave discharge and ECR ion sources will be hereinafter described. The details of different tests performed on a 14.5 GHz operating ECR ion source and on a plasma reactor operating at 2.45 GHz for enviromental purposes are reported. In particular this last device, equipped with a Langmuir probe, has been very useful to verify the presence of stationary waves and to study the electromagnetic wave propagation in plasmas. The evaluation of the Q factor with and without plasma and the determination of its variation with plasma density and temperature will be also presented.
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Slides
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| TUCO-B04 |
Broadband Excitation of ECR Plasmas
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145 |
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- W. D. Cornelius
SSolutions, San Diego CA
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Funding: This material is based upon work supported by the U. S. Department of Energy under Award Number DE-FG02-04ER84166.
Scientific Solutions developed an rf source capable of producing a variety of rf spectra for excitation of ECR plasmas at 2.45, 6.5, 14.5, 18.0, and 28.0 GHz. This device replaces the crystal oscillator in the rf chain and is essentially a software-defined radio transmitter that allows the user to select from a variety of rf spectral patterns via an Ethernet link. Two specific types of patterns were chosen for an initial series of tests: 1) a simultaneous multimode pattern comprised of a number rf-modes within a user-specified bandwidth and 2) a "chirp" spectral pattern comprised of a series of discrete frequencies where the chirp bandwidth, slew direction, and slew rate are user-selectable. The number of modes is a user-defined value between 1 and 1024. This paper describes the design of the rf circuit and its theory of operation. Initial results of our tests with the 6.4 and 14.5 GHz ECR sources at Texas A&M University and with the 14.5 GHz AECR-U source at the Lawerence Berkeley National Laboratory are also presented.
*Current Address: SAIC, 10740 Thornmint Road, San Diego, CA 92127
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Slides
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| TUCO-C01 |
Three-Dimensional Simulation of Electrons and Ions in ECRIS
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154 |
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- J. H. Andrä
Westfaelische Wilhelms-Universität Muenster, Muenster
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Electron-Cyclotron-Resonance-(ECR)-Heating (ECRH) is known to produce non-equilibrium plasmas with the total non-Maxwellian energy in the electrons while the ions stay below 1 eV. Theories based on Maxwell distributions are thus unable to correctly describe ECR-Ion Sources (ECRIS). Particle In Cell (PIC)-techniques are feasible only with significant approximations in the extremely complicated magnetic structure of an ECRIS. This is the reason to concentrate all efforts on the calculation of various electron distributions in an ECRIS taking into account all three-dimensional static fields, dynamic microwave fields, and all collisions of the electrons. To this end the Boris-algorithm is introduced which is shown to be very efficient and precise for all conditions in an ECRIS including the resonance transitions. The electron distributions clearly show the low efficiency of ECRH in a standard ECRIS with a central minimum of the axial magnetic field compared to the high ECRH-efficiency in a plateau-ECRIS with a flat central minimum. A non-relativistic version of the code is used to demonstrate the positive effects of ion-CRH on the confinement of the ions with far reaching consequences.
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Slides
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| TUCO-C02 |
Towards Kinetic Modeling of Ion Transport in an ECRIS Plasma
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155 |
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- P. J. Mullowney, Y. Choi, D. W. Fillmore, P. Messmer, D. S. Smithe
Tech-X, Boulder, Colorado
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Funding: Work supported by DOE Office of Science, Office of High Energy Physics, and Office of Nuclear Physics, Grant #'s DE-FG02-06ER84484 (HighZ) and Tech-X Corporation.
Next generation heavy ion beam accelerators require intense, high charge state ion currents of exotic materials. ECRIS devices can generate these currents however detailed kinetic simulations are needed to optimize the loading of these materials into the plasma. Full Particle-In-Cell simulations of the plasma are highly challenging due to the large discrepancy between length and time scales. However separation of time-scales provides a means of making progress. Electrostatic simulations on ion timescales, though demanding, are capable of modeling the kinetic behavior of the ions. Similarly, electromagnetic simulations on electron time scales can provide the non-thermal kinetic properties of the electron population. In this work, we treat the electrons as a simplified fluid for the longer time-scale evolution of the ions. We characterize and diagnose the electron distribution for use in the ion simulations. Ionization and recombination processes are then modeled in a hybrid fluid-electron / kinetic-ion formulation using the prescribed electron distribution as one of the interaction partners. Progress in the electrostatic modeling of the ion dynamics is also presented.
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Slides
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| TUCO-D01 |
Measurements of Electron Cyclotron Resonance Ion Source Bremsstrahlung Time Evolution and Preglow Effect
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160 |
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- T. Ropponen, P. Jones, T. Kalvas, H. A. Koivisto, P. Peura
JYFL, Jyvaskyla
- P. Suominen
Prizztech Ltd, Magnet Technology Centre, Pori
- O. A. Tarvainen
LANL, Los Alamos, New Mexico
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In order to understand properly the ECR heating and hot electron generation time evolution, measurements of ECRIS bremsstrahlung in radial direction using pulsed RF power with JYFL 14 GHz ECRIS have been performed. The effects of RF power, plasma species, neutral gas pressure and axial magnetic field strength were studied. So-called "preglow effect" for different charge states was studied in conjunction with the bremsstrahlung measurements. An analysis code that combines the bremsstrahlung data i.e. energy and time of incidence from consecutive RF pulses has been written. This method ensures that enough statistics is used for interpretation of the results. Pile-ups, ADC overflows and such disturbances are removed from the Ge detector spectra by using digital signal processing unit. In this paper the time evolution of the electron population with energies over 15 keV in millisecond region time intervals will be presented and the time scale of the preglow effect is connected into the development of the electron energy distribution.
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Slides
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| TUCO-D03 |
Study of the Dependence of ECR Ion Current on Periodic Plasma Disturbance
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169 |
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- Dr. G. S. Taki, R. K. Bhandari, D. K. Chakraborty, P. R. Sarma
DAE/VECC, Calcutta
- A. G. Drentje
KVI, Groningen
- T. Nakagawa
RIKEN Nishina Center, Wako, Saitama
- P. K. Ray
Bengal Engineering and Science University, Howrah
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In a recent work we observed the existence of periodic current bursts from an ECR ion source when a biased disc is used for enhancing the extracted beam current. It was concluded that the current per burst in the source remains essentially constant. When the disc bias voltage is increased, the burst frequency increases, and so does the total current. Further it was seen that the current undergoes a jump at a fixed bias potential. The current jump has been found to be proportional to the charge state. The burst frequency also shows a correlated jump. However, in the case of protons a different trend is observed. As the bias potential is increased, at a particular potential value the current suddenly decreases. In this work we have studied the periodic bursts in the proton current in order to understand the difference in the behaviour of current jump in protons and heavy ions.
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| TUCO-D05 |
Gyrotron Introduction for Ecris 2008
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174 |
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- H. Jory, M. Blank, S. Cauffman, K. Felch
CPI, Palo Alto, California
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Gyrotrons are proving to be very reliable sources of high power at frequencies in the range of 28 to 170 GHz, where other sources are very limited in power capability. As a specific example for ECRIS applications, a 10 kW, 28 GHz CW gyrotron has made possible significant increases in the ion currents generated by the Venus ion source at the Lawrence Berkeley Laboratory*. In this paper we briefly discuss the physics and engineering aspects of the gyrotron oscillator, point out some of the issues that require special treatment in the control system and power supplies for it, review related gyro-devices, and present important applications.
*D. Leitner, C. M. Lyneis, S. R. Abbott, R. D. Dwinell, D. Collins, and M. Leitner, “First Results of the Superconducting ECR Ion Source VENUS with 28 GHz”, Proceedings of the 16th International Workshop on ECR Ion Sources, ECRIS’04, Berkeley, CA, September, 2004.
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Slides
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