CYCLOTRONS 2010 - List of Authors (Brandenburg, S.)

Paper

Title

Page

Progress towards High Intensity Heavy Ion Beams at the AGOR-Facility

21

S. Brandenburg, J.P.M. Beijers, M.A. Hevinga, M.A. Hofstee, H.R. Kremers, V. Mironov, J. Mulder, S. Saminathan, A. Sen
KVI, Groningen, The Netherlands

Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM).
The on-going upgrade program of the AGOR-facility aiming at intensities beyond 10¹² pps for heavy ion beams up to Pb will be discussed. The progress in the main elements of the program (further development of the ECR-source; improvement of the transmission into and through the cyclotron and protection of equipment agains excessive beam loss) will be reported. Further improvement of the ECR ion source is facilitated by the installation of a second source. Redesign of the LEBT to compensate aberrations is in progress; simulations predict a significant increase in transmission. A new, cooled electrostatic extractor is being commissioned and the beam loss control system has been completed. The main remaining issue is vacuum degradation induced by beam loss caused by charge exchange on the residual gas. Experiments at GSI[1] have shown that scrapers and surface coatings can strongly reduce this effect. Tracking calculations of the distribution of the beam losses over the vacuum chamber to determine the optimum location of scrapers and application of a gold coating to relevant parts of the vacuum chamber are underway.
[1] C. Omet, H. Kollmus, H. Reich-Sprenger, P. Spiller; Ion catcher system for the stabilisation of the dynamic pressure in SIS18; http://jacow.org/e08/papers/mopc099.pdf

Slides MOM2CCO03 [1.532 MB]

MOPCP053

ECR Ion Source Development at the AGOR Facility

156

V. Mironov, J.P.M. Beijers, S. Brandenburg, H.R. Kremers, J. Mulder, S. Saminathan
KVI, Groningen, The Netherlands

Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM).
This paper reports on recent work to improve the performance of the 14 GHz KVI-AECR ion source, which is used as an injector for the AGOR cyclotron. We have installed stainless-steel screens at the injection and extraction sides and an additional collar around the extraction aperture resulting in better plasma stability and an increase of extracted ion currents. Stability and output are also improved by the use of additional RF power at 12 GHz. Source tuning is aided by continuously observing the visible light output of the plasma through the extraction aperture with a ccd camera. We now routinely extract 700 μA of O⁶⁺ and 50 μA of Pb²⁷⁺ ions. Source optimization is supported by extensive computational modeling of the ion transport in the low-energy beam line and measuring the transverse emittance of the extracted ion beam with a pepperpot emittance meter. These efforts have shown that second-order aberrations in the analyzing magnet lead to a significant increase of the effective beam emittance. Work to compensate these aberrations is underway

MOPCP083

Vacuum Simulation for Heavy Ion Beams in the AGOR-Cyclotron

221

A. Sen, S. Brandenburg, M.A. Hofstee, M.J. van Goethem
KVI, Groningen, The Netherlands

Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM).
The vacuum in the AGOR cyclotron and thereby the beam transmission is beam intensity dependent for heavy ions. The onset of significant vacuum and transmission degradation is dependent on the ion species and final energy. For ²⁰Ne⁶⁺ @ 23 MeV/A no significant effects are observed for intensities up to at least 2 x 10¹² pps, while for ²⁰⁶Pb²⁷⁺ @ 8.5 MeV/A degradation sets in at around 10¹¹ pps. This process is driven by the loss of particles through charge exchange with the residual gas and subsequent desorption from the chamber walls induced by the lost particles. We are developing a model based on particle tracking simulations of beam particles after charge exchange and 3D vacuum simulation including the experimentally determined 'regular' out gassing and induced desorption. An experimental setup to measure beam induced desorption was built and tested. It will be used to evaluate the mitigation measures such as surface treatment and stimulated out gassing. Improvement of the vacuum in the injection line, which is limiting the overall transmission, is also presented.

MOPCP087

Beamloss Monitoring and Control for High Intensity Beams at the AGOR-Facility

227

M.A. Hevinga, S. Brandenburg, T.W. Nijboer, J. Vorenholt
KVI, Groningen, The Netherlands

Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM).
The experiments at the AGOR facility require intense heavy ion beams with a beam power up to 500 W. Examples are 6 x 10¹² pps of ²⁰Ne at 23 MeV/A and 10¹² pps ²⁰⁶Pb at 8.5 MeV/A. To prevent damage to components by the beam (power density >100 W/mm³ in unfavorable cases) a modular beam loss monitoring and control system has been developed for the cyclotron and high energy beam lines. The architecture of the system will be described and the considerations for the major design choices discussed. The system uses the CAN-bus for communication and verification of system integrity. The injected beam is chopped at 1 kHz with a variable duty factor up to 90 %. The beam intensity at injection and a number of locations in the high energy beam line is measured by inductive pick-ups. Furthermore localized beam losses on slits and diaphragms are directly measured. When beam loss in any section exceeds the predefined maximum value the duty factor of the beam is automatically reduced. Beam diagnostics are protected by switching off the beam when they are inserted at too high intensity.

Paper	Title	Page
MOM2CCO03	Progress towards High Intensity Heavy Ion Beams at the AGOR-Facility	21
	S. Brandenburg, J.P.M. Beijers, M.A. Hevinga, M.A. Hofstee, H.R. Kremers, V. Mironov, J. Mulder, S. Saminathan, A. Sen KVI, Groningen, The Netherlands
	Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM). The on-going upgrade program of the AGOR-facility aiming at intensities beyond 10¹² pps for heavy ion beams up to Pb will be discussed. The progress in the main elements of the program (further development of the ECR-source; improvement of the transmission into and through the cyclotron and protection of equipment agains excessive beam loss) will be reported. Further improvement of the ECR ion source is facilitated by the installation of a second source. Redesign of the LEBT to compensate aberrations is in progress; simulations predict a significant increase in transmission. A new, cooled electrostatic extractor is being commissioned and the beam loss control system has been completed. The main remaining issue is vacuum degradation induced by beam loss caused by charge exchange on the residual gas. Experiments at GSI[1] have shown that scrapers and surface coatings can strongly reduce this effect. Tracking calculations of the distribution of the beam losses over the vacuum chamber to determine the optimum location of scrapers and application of a gold coating to relevant parts of the vacuum chamber are underway. [1] C. Omet, H. Kollmus, H. Reich-Sprenger, P. Spiller; Ion catcher system for the stabilisation of the dynamic pressure in SIS18; http://jacow.org/e08/papers/mopc099.pdf
	Slides MOM2CCO03 [1.532 MB]

MOPCP053	ECR Ion Source Development at the AGOR Facility	156
	V. Mironov, J.P.M. Beijers, S. Brandenburg, H.R. Kremers, J. Mulder, S. Saminathan KVI, Groningen, The Netherlands
	Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM). This paper reports on recent work to improve the performance of the 14 GHz KVI-AECR ion source, which is used as an injector for the AGOR cyclotron. We have installed stainless-steel screens at the injection and extraction sides and an additional collar around the extraction aperture resulting in better plasma stability and an increase of extracted ion currents. Stability and output are also improved by the use of additional RF power at 12 GHz. Source tuning is aided by continuously observing the visible light output of the plasma through the extraction aperture with a ccd camera. We now routinely extract 700 μA of O⁶⁺ and 50 μA of Pb²⁷⁺ ions. Source optimization is supported by extensive computational modeling of the ion transport in the low-energy beam line and measuring the transverse emittance of the extracted ion beam with a pepperpot emittance meter. These efforts have shown that second-order aberrations in the analyzing magnet lead to a significant increase of the effective beam emittance. Work to compensate these aberrations is underway

MOPCP083	Vacuum Simulation for Heavy Ion Beams in the AGOR-Cyclotron	221
	A. Sen, S. Brandenburg, M.A. Hofstee, M.J. van Goethem KVI, Groningen, The Netherlands
	Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM). The vacuum in the AGOR cyclotron and thereby the beam transmission is beam intensity dependent for heavy ions. The onset of significant vacuum and transmission degradation is dependent on the ion species and final energy. For ²⁰Ne⁶⁺ @ 23 MeV/A no significant effects are observed for intensities up to at least 2 x 10¹² pps, while for ²⁰⁶Pb²⁷⁺ @ 8.5 MeV/A degradation sets in at around 10¹¹ pps. This process is driven by the loss of particles through charge exchange with the residual gas and subsequent desorption from the chamber walls induced by the lost particles. We are developing a model based on particle tracking simulations of beam particles after charge exchange and 3D vacuum simulation including the experimentally determined 'regular' out gassing and induced desorption. An experimental setup to measure beam induced desorption was built and tested. It will be used to evaluate the mitigation measures such as surface treatment and stimulated out gassing. Improvement of the vacuum in the injection line, which is limiting the overall transmission, is also presented.

MOPCP087	Beamloss Monitoring and Control for High Intensity Beams at the AGOR-Facility	227
	M.A. Hevinga, S. Brandenburg, T.W. Nijboer, J. Vorenholt KVI, Groningen, The Netherlands
	Funding: This work is supported by the European Union through EURONS, contract 506065 and the "Stichting voor Fundamenteel Onderzoek der Materie" (FOM). The experiments at the AGOR facility require intense heavy ion beams with a beam power up to 500 W. Examples are 6 x 10¹² pps of ²⁰Ne at 23 MeV/A and 10¹² pps ²⁰⁶Pb at 8.5 MeV/A. To prevent damage to components by the beam (power density >100 W/mm³ in unfavorable cases) a modular beam loss monitoring and control system has been developed for the cyclotron and high energy beam lines. The architecture of the system will be described and the considerations for the major design choices discussed. The system uses the CAN-bus for communication and verification of system integrity. The injected beam is chopped at 1 kHz with a variable duty factor up to 90 %. The beam intensity at injection and a number of locations in the high energy beam line is measured by inductive pick-ups. Furthermore localized beam losses on slits and diaphragms are directly measured. When beam loss in any section exceeds the predefined maximum value the duty factor of the beam is automatically reduced. Beam diagnostics are protected by switching off the beam when they are inserted at too high intensity.