ECRIS2010 - List of Authors (Celona, L.)

Paper

Title

Page

Tests of the Versatile Ion Source (VIS) for High Power Proton Beam Production

61

S. Gammino, G. Castro, L. Celona, G. Ciavola, D. Mascali, R. Miracoli
INFN/LNS, Catania, Italy
G. Adroit, O. Delferrière, R. Gobin, F. Senée
CEA/DSM/IRFU, France
F. Maimone
GSI, Darmstadt, Germany

The sources adapted to beam production for high power proton accelerators must obey to the request of high brightness, stability and reliability. The Versatile Ion Source (VIS) is based on permanent magnets (maximum value around 0.1 T on the chamber axis) producing an off-resonance microwave discharge. It operates up to 75 kV without a bulky high voltage platform, producing several tens of mA of proton beams and monocharged ions. The microwave injection system and the extraction electrodes geometry have been designed in order to optimize the beam brightness. Moreover, the VIS source ensures long time operations without maintenance and high reliability in order to fulfil the requirements of the future accelerators. A description of the main components and of the source performances will be given. A brief summary of the possible options for next developments of the project will be also presented, particularly for pulsed mode operations, that are relevant for some future projects (e.g. the European Spallation Source of Lund).

TUPOT002

Enhancement of ECR Performances by Means of Carbon Nanotubes Based Electron Guns

114

F. Odorici, M. Cuffiani, L. Malferrari, R. Rizzoli, G.P. Veronese
INFN-Bologna, Bologna, Italy
G. Castro, L. Celona, G. Ciavola, N. Gambino, S. Gammino, D. Mascali, R. Miracoli, F.P. Romano
INFN/LNS, Catania, Italy
T. Serafino
Università di Messina, Messina, Italy

One of the main goals of the scientific community which deals with ECR Ion Sources is the optimization of the Eelectron Energy Distribution Function (EEDF) inside the plasma. The EEDF consists of three different populations (cold, warm and hot electrons): the cold and the warm populations are responsible of the stabilization and of the efficient ionization of the plasma respectively. The presence of the hot population is doubly detrimental: in high frequency sources they lead to the heating of LHe in the superconducting coils’ cryostat and are also useless for the generation of high intensity ion beams, because of their small cross section. Therefore the injection of additional electrons inside the plasma may increase the density of cold and warm electrons, enabling at the same time to reduce the number of the high energy ones. The CANTES experiment tested the use of carbon nanotubes (CNTs) to emit electrons in presence of strong applied electric fields, in order to provide additional electrons to the plasma core. This technique was used with the Caesar ECR ion source, at INFN-LNS, demonstrating that the total extracted ion current is increased and that a relevant reduction of the number of “high energy” electrons (above 100 keV) can be obtained. This last result is even more important, because CNTs may be an effective and reliable tool to permit the operation of ECRIS at large power and high frequencies without any detrimental effect on the source stability and reliability coming from hot electrons. Details of the construction of CNTs based electron gun and their behaviour in plasma environments are presented. Preliminary results in terms of performances of the Caesar ECR ion source and possible future applications will be also discussed.

Poster TUPOT002 [1.914 MB]

TUPOT010

Effects of Microwave Frequency Fine Tuning on the Performance of JYFL 14 GHz ECRIS

137

V.A. Toivanen, V.P. Aho, J. Ärje, P. Jones, J.A. Kauppinen, H. A. Koivisto, P. Peura, O.A. Tarvainen
JYFL, Jyväskylä, Finland
L. Celona, G. Ciavola, S. Gammino
INFN/LNS, Catania, Italy
A. Galatà
INFN/LNL, Legnaro (PD), Italy
D. Mascali
CSFNSM, Catania, Italy
T. Ropponen
NSCL, East Lansing, Michigan, USA

Measurements have been carried out at Department of Physics, University of Jyväskylä (JYFL) to study the effects of microwave frequency fine tuning on the performance of JYFL 14 GHz electron cyclotron resonance ion source. The frequency was varied within an 85 MHz band around the normal operation frequency of 14.085 GHz. The radial bremsstrahlung emission was measured for plasma diagnostics purposes and mass separated ion beam currents extracted from the ion source were recorded at the same time. Also, beam quality studies were conducted by measuring the ion beam emittance and shape with and without enhanced space charge compensation. The obtained results are presented and possible origins of seen phenomena in measured quantities are discussed.

Poster TUPOT010 [0.678 MB]

TUPOT012

Microwave Frequency Dependence of the Properties of the Ion Beam Extracted From a Caprice Type ECRIS

143

F. Maimone, R. Lang, J. Mäder, J. Roßbach, P. Spädtke, K. Tinschert
GSI, Darmstadt, Germany
L. Celona
INFN/LNS, Catania, Italy
F. Maimone
DMFCI, Catania, Italy

In order to improve the quality of ion beams extracted from ECR ion sources it is mandatory to better understand the relations between the plasma conditions and the beam properties. The present investigations concentrate on the analysis of different beam properties under the influence of various applications of frequency tuning and of multiple frequency heating. The microwave frequency feeding the plasma affects the electromagnetic field distribution and the dimension and position of the ECR surface inside the plasma chamber. This in turn has an influence on the generation of the extracted ion beam in terms of its intensity, of its shape and of its emittance. In order to analyze the corresponding effects measurements have been performed with the Caprice type ECRIS installed at the ECR Injector Setup (EIS) of GSI. The experimental setup uses a new arrangement of one or more microwave sweep generators which feed a Traveling Wave Tube amplifier covering a wide frequency range from 12.5 to 18 GHz. This arrangement provides a precise determination of the frequencies and of the reflection coefficient along with the beam properties. A sequence of viewing targets positioned inside the beam line monitors the beam shape.

Poster TUPOT012 [1.245 MB]

WECOAK02

Some Considerations About Frequency Tuning Effect in ECRIS Plasmas

165

D. Mascali, G. Castro, L. Celona, G. Ciavola, N. Gambino, S. Gammino, R. Miracoli, L. Neri
INFN/LNS, Catania, Italy
F. Maimone
GSI, Darmstadt, Germany

During the last years many experiments have demonstrated that slight variations in microwave frequency used to heat and sustain the plasma of ECRIS may strongly influence their performances (frequency tuning effect) both in terms of extracted current and mean charge state. Theoretical investigations revealed that this phenomenon can be correctly explained assuming that the plasma chamber works as a resonant cavity: standing waves are excited inside of it, and their spatial structure considerably changes even with slight variations of the pumping frequency. Therefore some particular modes present a higher electric field on the resonance surface, that is the only region in which the energy transfer from waves to electrons occurs. Experimental measurements carried out on microwave discharge plasmas at high density (up to 10¹¹ cm^-3) featured that even if the absorption of electromagnetic energy at the ECR surface is evident, the stochastic nature of the wave-electron interaction allows the wave to be reflected at the extraction flange, thus forming a standing wave. The model here proposed, and based on PIC and MonteCarlo collisional simulations, puts in evidence that the frequency tuning effect in ECRIS has a global influence on plasma properties: it strongly affects both ion and electron dynamics. Electron heating, electron density distribution, ion formation and acceleration at resonance surface, beam formation are determined by the particular mode excited inside the cavity. This means that the frequency tuning will be an important tool for future ECRIS for the optimization of the beam quality (emittance, etc.).

Slides WECOAK02 [4.765 MB]

Paper	Title	Page
MOPOT012	Tests of the Versatile Ion Source (VIS) for High Power Proton Beam Production	61
	S. Gammino, G. Castro, L. Celona, G. Ciavola, D. Mascali, R. Miracoli INFN/LNS, Catania, Italy G. Adroit, O. Delferrière, R. Gobin, F. Senée CEA/DSM/IRFU, France F. Maimone GSI, Darmstadt, Germany
	The sources adapted to beam production for high power proton accelerators must obey to the request of high brightness, stability and reliability. The Versatile Ion Source (VIS) is based on permanent magnets (maximum value around 0.1 T on the chamber axis) producing an off-resonance microwave discharge. It operates up to 75 kV without a bulky high voltage platform, producing several tens of mA of proton beams and monocharged ions. The microwave injection system and the extraction electrodes geometry have been designed in order to optimize the beam brightness. Moreover, the VIS source ensures long time operations without maintenance and high reliability in order to fulfil the requirements of the future accelerators. A description of the main components and of the source performances will be given. A brief summary of the possible options for next developments of the project will be also presented, particularly for pulsed mode operations, that are relevant for some future projects (e.g. the European Spallation Source of Lund).

TUPOT002	Enhancement of ECR Performances by Means of Carbon Nanotubes Based Electron Guns	114
	F. Odorici, M. Cuffiani, L. Malferrari, R. Rizzoli, G.P. Veronese INFN-Bologna, Bologna, Italy G. Castro, L. Celona, G. Ciavola, N. Gambino, S. Gammino, D. Mascali, R. Miracoli, F.P. Romano INFN/LNS, Catania, Italy T. Serafino Università di Messina, Messina, Italy
	One of the main goals of the scientific community which deals with ECR Ion Sources is the optimization of the Eelectron Energy Distribution Function (EEDF) inside the plasma. The EEDF consists of three different populations (cold, warm and hot electrons): the cold and the warm populations are responsible of the stabilization and of the efficient ionization of the plasma respectively. The presence of the hot population is doubly detrimental: in high frequency sources they lead to the heating of LHe in the superconducting coils’ cryostat and are also useless for the generation of high intensity ion beams, because of their small cross section. Therefore the injection of additional electrons inside the plasma may increase the density of cold and warm electrons, enabling at the same time to reduce the number of the high energy ones. The CANTES experiment tested the use of carbon nanotubes (CNTs) to emit electrons in presence of strong applied electric fields, in order to provide additional electrons to the plasma core. This technique was used with the Caesar ECR ion source, at INFN-LNS, demonstrating that the total extracted ion current is increased and that a relevant reduction of the number of “high energy” electrons (above 100 keV) can be obtained. This last result is even more important, because CNTs may be an effective and reliable tool to permit the operation of ECRIS at large power and high frequencies without any detrimental effect on the source stability and reliability coming from hot electrons. Details of the construction of CNTs based electron gun and their behaviour in plasma environments are presented. Preliminary results in terms of performances of the Caesar ECR ion source and possible future applications will be also discussed.
	Poster TUPOT002 [1.914 MB]

TUPOT010	Effects of Microwave Frequency Fine Tuning on the Performance of JYFL 14 GHz ECRIS	137
	V.A. Toivanen, V.P. Aho, J. Ärje, P. Jones, J.A. Kauppinen, H. A. Koivisto, P. Peura, O.A. Tarvainen JYFL, Jyväskylä, Finland L. Celona, G. Ciavola, S. Gammino INFN/LNS, Catania, Italy A. Galatà INFN/LNL, Legnaro (PD), Italy D. Mascali CSFNSM, Catania, Italy T. Ropponen NSCL, East Lansing, Michigan, USA
	Measurements have been carried out at Department of Physics, University of Jyväskylä (JYFL) to study the effects of microwave frequency fine tuning on the performance of JYFL 14 GHz electron cyclotron resonance ion source. The frequency was varied within an 85 MHz band around the normal operation frequency of 14.085 GHz. The radial bremsstrahlung emission was measured for plasma diagnostics purposes and mass separated ion beam currents extracted from the ion source were recorded at the same time. Also, beam quality studies were conducted by measuring the ion beam emittance and shape with and without enhanced space charge compensation. The obtained results are presented and possible origins of seen phenomena in measured quantities are discussed.
	Poster TUPOT010 [0.678 MB]

TUPOT012	Microwave Frequency Dependence of the Properties of the Ion Beam Extracted From a Caprice Type ECRIS	143
	F. Maimone, R. Lang, J. Mäder, J. Roßbach, P. Spädtke, K. Tinschert GSI, Darmstadt, Germany L. Celona INFN/LNS, Catania, Italy F. Maimone DMFCI, Catania, Italy
	In order to improve the quality of ion beams extracted from ECR ion sources it is mandatory to better understand the relations between the plasma conditions and the beam properties. The present investigations concentrate on the analysis of different beam properties under the influence of various applications of frequency tuning and of multiple frequency heating. The microwave frequency feeding the plasma affects the electromagnetic field distribution and the dimension and position of the ECR surface inside the plasma chamber. This in turn has an influence on the generation of the extracted ion beam in terms of its intensity, of its shape and of its emittance. In order to analyze the corresponding effects measurements have been performed with the Caprice type ECRIS installed at the ECR Injector Setup (EIS) of GSI. The experimental setup uses a new arrangement of one or more microwave sweep generators which feed a Traveling Wave Tube amplifier covering a wide frequency range from 12.5 to 18 GHz. This arrangement provides a precise determination of the frequencies and of the reflection coefficient along with the beam properties. A sequence of viewing targets positioned inside the beam line monitors the beam shape.
	Poster TUPOT012 [1.245 MB]

WECOAK02	Some Considerations About Frequency Tuning Effect in ECRIS Plasmas	165
	D. Mascali, G. Castro, L. Celona, G. Ciavola, N. Gambino, S. Gammino, R. Miracoli, L. Neri INFN/LNS, Catania, Italy F. Maimone GSI, Darmstadt, Germany
	During the last years many experiments have demonstrated that slight variations in microwave frequency used to heat and sustain the plasma of ECRIS may strongly influence their performances (frequency tuning effect) both in terms of extracted current and mean charge state. Theoretical investigations revealed that this phenomenon can be correctly explained assuming that the plasma chamber works as a resonant cavity: standing waves are excited inside of it, and their spatial structure considerably changes even with slight variations of the pumping frequency. Therefore some particular modes present a higher electric field on the resonance surface, that is the only region in which the energy transfer from waves to electrons occurs. Experimental measurements carried out on microwave discharge plasmas at high density (up to 10¹¹ cm^-3) featured that even if the absorption of electromagnetic energy at the ECR surface is evident, the stochastic nature of the wave-electron interaction allows the wave to be reflected at the extraction flange, thus forming a standing wave. The model here proposed, and based on PIC and MonteCarlo collisional simulations, puts in evidence that the frequency tuning effect in ECRIS has a global influence on plasma properties: it strongly affects both ion and electron dynamics. Electron heating, electron density distribution, ion formation and acceleration at resonance surface, beam formation are determined by the particular mode excited inside the cavity. This means that the frequency tuning will be an important tool for future ECRIS for the optimization of the beam quality (emittance, etc.).
	Slides WECOAK02 [4.765 MB]