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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-D02 |
Ion Cyclotron Resonance Heating in a Plateau-ECRIS
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168 |
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- M. Kahnt, B. Albers, L. Hupe, L. Nowack, H. W. Ortjohann
Institut fur Kernphysik, Westfalische Wilhelms-Universitat Munster, Munster
- J. H. Andrä
Westfaelische Wilhelms-Universität Muenster, Muenster
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It is shown why static or low frequency electric fields perpendicular to the magnetic field can penetrate into a magnetized plasma of high density. A configuration of electrodes is chosen for the application of radio-frequency electric fields to heat by ion-cyclotron-resonance (ICR) Ar(q+)-, H-, and He-ions in PECRIS V with a magnetic plateau and a great resonance volume. It is shown that all ions ICR-heated in this resonance volume gain rotational energy E(rot) and stay thus better confined leading to a drop so that their extracted currents. E(rot) of these ions thermalizes while they are further ionized by electron collisions so that the extracted currents of Ar((q+n)+)-ions do show a considerable increase with 2<n<7. The extracted currents of the two ICR-heated light ions do show only drops which will be discussed in detail. As proof of their gain of E(rot) the energy gain of extracted He-ions has been measured. The ICR-heating of multi-charged ions may thus be a technique to considerably improve the currents of the highest charge states.
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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-D04 |
Effects of Roll Angles on Halbach Array Efficiency
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173 |
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- D. Maybury, M. M. Scannell, F. E. Spada
ANL, Argonne, Illinois
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The Halbach Array was first described by Mallinson in 1973 (IEEE Transactions on Magnetics, 9, 678-682, 1973). Named after Klaus Halbach, the Berkeley physicist who first applied Halbach arrays in the construction of wigglers, Halbach Arrays have seen increased use in applications that require high weight to magnetic field efficiency. Since magnet geometry is often dictated by the application, weight, and/or cost requirements, the progression of the angular orientation (roll angle) of the array is a frequent target for optimizing array performance. The effect of different roll angles of a magnet system is studied here on a canonical linear array modeled with two different magnet alloys – one high-energy, low-coercivity alloy, and one high-coercivity alloy. All models studied are comprised of square cross-sections. The integrated flux on each side of the array is compared for efficiency, while the half-maximum distances are compared for projection strength. To validate the model results, the candidate arrays are physically constructed, measured and compared to the modeled outcomes.
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Slides
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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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