CYCLOTRONS 2010 - List of Keywords (vacuum)

Paper	Title	Other Keywords	Page
MOM2CCO03	Progress towards High Intensity Heavy Ion Beams at the AGOR-Facility	beam-losses, ion, cyclotron, acceleration	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]

MOA2CCO02	Current Status of the Cyclotron Facilities and Future Projects at iThemba Labs	controls, cyclotron, ion, proton	42
	J.L. Conradie, L.S. Anthony, A.H. Botha, M.A. Crombie, J.G. De Villiers, J.L.G. Delsink, W. Duckitt, D.T. Fourie, M.E. Hogan, I.H. Kohler, C. Lussi, R.H. McAlister, H.W. Mostert, S.S. Ntshangase, J.V. Pilcher, P.F. Rohwer, M. Sakildien, N. Stodart, R.W. Thomae, M.J. Van Niekerk, D. de Villiers, P.A. van Schalkwyk iThemba LABS, Somerset West, South Africa C. Böhme UniDo/IBS, Dortmund, Germany J. Dietrich FZJ, Jülich, Germany Z. Kormány ATOMKI, Debrecen, Hungary
	For nearly 25 years the cyclotron facilities at iThemba LABS have been utilized for radioisotope production, nuclear physics research, and proton and neutron therapy. The aging systems require continual upgrading and replacement to limit interruptions to the scheduled beam delivery. The distributed computer control system is being migrated to a system running on the EPICS platform. The analogue low-level RF control systems will be replaced with digital systems. The Minimafios ECR ion source has been replaced with an ECR source from the former Hahn Meitner Institute and a second source, based on the design of the Grenoble test source, will be commissioned later this year. To increase the production of radio-isotopes, the 66 MeV proton beam is split to deliver beam simultaneously to two production targets. The first result with the beam splitter will be reported. A beam phase measurement system comprising 21 fixed probes has been installed in the separated sector cyclotron. Progress with these projects and the status of the facilities will be presented. Proposals for new facilities for proton therapy and for acceleration of radioactive beams will also be discussed.
	Slides MOA2CCO02 [4.496 MB]

MOA2CCO03	Status of the LBNL 88-Inch Cyclotron High-Voltage Injection Upgrade Project	cyclotron, ion, injection, ion-source	45
	K. Yoshiki Franzen, P.W. Casey, A. Hodgkinson, M. Kireeff Covo, D. Leitner, C.M. Lyneis, L. Phair, P. Pipersky LBNL, Berkeley, California, USA
	The goal of the project includes design of a new center region that allows external beam injection at injection voltages between 20 and 30 kV for high intensity beams. This new center region will make use of a spiral inflector to eliminate the use of a gridded mirror for high intensity beams. At the same time the mechanical design of the new center region must be flexible enough to allow use of the current center region for less intense beams. The use of two or more different center regions is necessary to cover the wide range of operation parameter space utilized by the 88-Inch Cyclotron Nuclear Science and Applied research program. The project also includes HV upgrades of the external injection lines and HV insulation of the AECR and VENUS source with the goal to provide focusing for beams up to 25 kV or if feasible up to 30 kV. The current spiral inflector design is based on extensive 3D FEM simulations which results will be presented. In addition results from ongoing efforts to improve on the transport efficiency from the AECR ion source to the current mirror inflector will be discussed.
	Slides MOA2CCO03 [1.359 MB]

MOPCP025	Construction of New Injector LINAC at RIBF	linac, rfq, impedance, ion	102
	K. Yamada, S. Arai, M. Fujimaki, T. Fujinawa, N. Fukunishi, A. Goto, Y. Higurashi, E. Ikezawa, O. Kamigaito, M. Kase, M. Komiyama, K. Kumagai, T. Maie, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, Y. Watanabe, Y. Yano, S. Yokouchi RIKEN Nishina Center, Wako, Japan H. Fujisawa Kyoto ICR, Uji, Kyoto, Japan Y. Sato KEK, Ibaraki, Japan
	A new additional linac injector called RILAC2 has been constructed at the RIKEN Nishina Center so that RIBF experiments and synthesis of super-heavy element can be carried out independently. The RILAC2 consists of a 28-GHz superconducting ECR ion source (SC-ECRIS), a low-energy beam transport with a prebuncher, a four-rod RFQ linac, three drift-tube linac tanks (DTL1-3), a rebuncher between the RFQ and DTL1, and strong quadrupole magnets that were placed between the rf resonators for the transverse focusing. Very heavy ions with mass-to-charge ratio of 7, such as ¹³⁶Xe²⁰⁺ and ²³⁸U³⁵⁺, are accelerated up to an energy of 680 keV/u in the cw mode and injected into the RRC without charge stripping. The rf resonators excluding the pre-buncher are operated at a fixed rf frequency of 36.5 MHz, whereas the pre-buncher is operated at 18.25 MHz. The basic design of the RILAC2 was finished in 2006 and the construction has started since the budget was approved at the end of FY2008. The SC-ECRIS is installed in a new room, and other equipments are placed in the existing AVF-cyclotron vault. This contribution mainly presents the details of the construction of linac part.

MOPCP058	Commissioning Experience of the RF System of K500 Superconducting Cyclotron at VECC	cyclotron, controls, radio-frequency, impedance	162
	S.S. Som, R.K. Bhandari, P. Gangopadhyay, A. Mandal, S.P. Pal, P.R. Raj, S. Saha, S. Seth DAE/VECC, Calcutta, India
	Funding: Department of Atomic Energy, Govt. of India. Radio frequency system of Superconducting cyclotron at VECC, has been developed to achieve accelerating voltage of 100 kV max. with frequency, amplitude and phase stability of 0.1 ppm, 100 ppm and ±0.5 degree respectively within 9~27 MHz frequency. Each of the three half-wave coaxial cavity is fed with rf power (80kW max.) from a high power final rf amplifier based on Eimac 4CW150,000E tetrodes. Initially, the whole three-phase RF system has been tuned for operation with RF power to the cavities at 19.1994 MHz and thereafter commissioned the cyclotron with neon 3+ beam at external radius at 14.0 MHz. In this paper, we present brief description of the rf system and behaviour observed during initial conditioning of the cavities with rf power and the way to get out of multipacting zone together with discussion on our operational experience. We have so far achieved dee voltage up to 52 kV at 14 MHz with 20 kW of RF power fed at each of the three dees and achieved vacuum level of 4.5 x 10^-7 mbar inside the beam chamber. We also present discussion on the problems and failures of some RF components during commissioning stage and rectifications done to solve the same.

MOPCP059	Theoritical Analysis and Fabrication of Coupling Capacitor for K500 Superconducting Cyclotron at Kolkata	coupling, cyclotron, extraction, radio-frequency	165
	M. Ahammed, R.K. Bhandari, P. Bhattacharyya, J. Chaudhuri, M.K. Dey, A. Dutta Gupta, B. Hemram, B.C. Mandal, N. Mandal, B. Manna, S. Murali, Y.E. Rao, S. Saha, S. Sur DAE/VECC, Calcutta, India
	K500 SC cyclotron has already been constructed and commissioned after spiraling Ne³⁺ internal beam with 70 nA upto extraction radius(670 mm) at Variable Energy Cyclotron Centre at Kolkata, India. Several problems have been experienced related to the coupling capacitor of the radio frequency system including it's sever burning during commissioning of the cyclotron. Making of the dissimilar joints between alumina ceramic and copper of the coupling capacitor demands the usage of vacuum furnace to avoid the cracking of the ceramic. Therefore exhaustive analysis has been carried out to facilitate the in-house fabrication of the coupling capacitor without using the vacuum furnace in case of emergency. The maximum allowable rate of temperature rise for the ceramic and the optimum thickness ration of the copper to ceramic has been estimated. Finally fabrication of the coupling capacitor has been carried out in-house without employing vacuum furnace. At present the coupling capacitor is performing well as maximum 57 kV DEE voltages were been achieved the till date. This paper presents the details of the analysis and experiences gain during the fabrication of the coupling capacitor.

MOPCP060	Design, Construction and Commissioning of the 100 kW RF Amplifier for CYCIAE-100	cyclotron, site, resonance, factory	168
	Z.G. Yin, B. Ji, Z.G. Li, T.J. Zhang, Z.L. Zhao CIAE, Beijing, People's Republic of China S.D. Wei, H.C. Xiao, Y. Xie CASIC, Beijing, People's Republic of China
	As a major part of the BRIF project, the 100 MeV high intensity cyclotron being constructed at CIAE, CYCIAE-100, will provide 200 μA proton beam ranging from 75 MeV to 100 MeV for RIB production. Two identical 100 kW RF amplifiers will be used to drive two cavities independently to accelerate H⁻ beam up to 100 MeV. The detail technical specification has been investigated, fixed, and initial design has been finished by CIAE. Then, the construction design and manufacture is implemented by China Academy of Aero and Space, and the on site commissioning is successful by mutual efforts. The final commissioning is under way with a full scale prototype cavity at CIAE. A general description of the CYCIAE-100 RF system design will be given, as well as the review of 100 kW amplifier design. In the commissioning of the amplifier with dummy load, different high order resonances are found when operated at different frequencies between 42 MHz to 46 MHz. An equivalent circuit model is carried out to hunt down the problems. The model and related analysis will be reported together with the process and results of high power test with the cavity load through ~35 meters six inch rigid transmission line.

MOPCP073	The Vacuum System of HIRFL Cyclotrons	cyclotron, ion, heavy-ion, extraction	195
	X.T. Yang, J. Meng, J.H. Zhang IMP, Lanzhou, People's Republic of China
	HIRFL has 2 cyclotrons: a sector focus cyclotron (SFC) and a separate sector cyclotron (SSC). SFC was built in 1957. In the past 50 years, the vacuum system of SFC has been upgraded for three times. The vacuum chamber was redesigned to double-deck at the third upgrade. The working pressure in beam chamber was improved from 10^-6 mbar to 10^-8 mbar. SFC has delivered Pb, Bi and U beams in the past few years since the last upgrading of its vacuum chamber. SSC began to operate in 1987. The vacuum chamber of SSC has a volume of 100m³. 8 cryopumps keep the pressure from 4×10^-7 mbar to 8×10^-8 mbar depending on the used pump numbers (2~8). In the past 20 years, because of the contamination of oil vapour and leaks occurred in some components inside the SSC vacuum chamber, the vacuum condition has worsened than the beginning. It is a big problem to accelerate the heavier ions. The upgrade for the SSC vacuum system will be an urgent task for us. The rough pumping system of both SFC and SSC will be rebuilt recently. The oil pump units will be changed by large dry mechanical pumps. As a result, the oil vapour in two cyclotrons will be eliminated and the vacuum condition of them will be improved.

MOPCP075	Cyclotron Vacuum Model and H⁻ Gas Stripping Losses	cyclotron, ion, extraction, target	200
	V. Nuttens, M. Abs, J.L. Delvaux, Y. Jongen, W.J.G.M. Kleeven, L. Medeiros-Romao, M. Mehaudens, T. Servais, T. Vanderlinden, P. Verbruggen IBA, Louvain-la-Neuve, Belgium
	Many proton cyclotrons take the advantage of stripping for the extraction, by accelerating H⁻ ions. However, before extraction, the negative ion beam can suffer losses from stripping by the residual gas. The higher is the pressure, the higher the losses. Moreover, the stripped beam will be stopped on the inner wall of the cyclotron, inducing an additional degassing and increasing the pressure and hence losses in the cyclotron. For high beam current, degassing can be too large compared to the pumping capacity and the beam transmission can drop down to zero. The pressure inside the cyclotron has therefore a large impact on the current that can be extracted from the cyclotron. A simple model has been set up at IBA to determine the vacuum pressure in the hills and in the valleys of the Cyclone 70 cyclotron. The transmission is then computed by integration of the gas stripping cross-section along the ion orbits in the cyclotron. Pressure and transmission provided by the model are in good agreement with experimental data in the ARRONAX Cyclone 70 cyclotron installed in Nantes.

MOPCP076	Operational Experience of Superconducting Cyclotron Magnet at VECC, Kolkata	controls, cyclotron, cryogenics, coupling	203
	U. Bhunia, M. Ahmed, R.K. Bhandari, T. Bhattacharyya, M.K. Dey, R. Dey, A. Dutta, A. Dutta Gupta, C. Mallik, C. Nandi, Z.A. Naser, G.P. Pal, U. Panda, S. Paul, J. Pradhan, S. Saha DAE/VECC, Calcutta, India
	The Kolkata Superconducting cyclotron magnet has been operational in the center since last few years and enabled us to extensively map magnetic fields over a year covering the operating range of the machine and successful commissioning of internal beam. The magnet cryostat coupled with the liquid helium refrigerator performs satisfactorily with moderate currents (<550A) in both the coils. The superconducting coil did not undergo any training and over the years has not suffered from any quench. Author would share the experience and difficulties of enhanced overall heat load to the liquid helium refrigerator at higher excitations of coils. This creates instability in the operation of liquid helium refrigerator and finally leads to slow dump. Rigorous study has been carried out in this regard to understand the problems and operational logic of liquid helium refrigerator has been modified accordingly to alleviate from. Some other measures have also been taken from cryostat and cryogenic distribution point of view in order to reduce the heat load at higher excitations.

MOPCP077	Median Plane Effects and Measurement Method for Radial Component of Magnetic Field in AVF Cyclotrons	cyclotron, extraction, alignment, simulation	206
	N.A. Morozov, G.A. Karamysheva JINR, Dubna, Moscow Region, Russia P. Shishlyannikov JINR/DLNP, Dubna, Moscow region, Russia
	The median plane of the magnetic field in AVF cyclotrons rather often does not coincide with the mid-plane of their magnetic system. The idea of an effective median plane formulated by J.I.M.Botman and H.L.Hagedorn [] for the central region of the cyclotron is extended to the entire working region and tolerances for the horizontal components of the magnetic field are estimated. Equipment based on the search coils is proposed and used for measurement of the radial component of the magnetic field and for correction of the magnetic field median plane. [] J.I.M.Botman, H.L.Hagedorn, 'Median Plane Effects in the Eindhoven AVF Cyclotron', IEEE Trans. On Nucl. Science, Vol. NS-28, No.3, p.2128.

MOPCP082	Design Study of AVF Magnet for Compact Cyclotron	cyclotron, simulation, proton, extraction	218
	H.W. Kim, J.-S. Chai, B.N. Lee, J.H. Oh SKKU, Suwon, Republic of Korea
	K=100 separated sector cyclotron and its injector cyclotron design is started on April, 2010 at Sungkyunkwan University. The main purpose of the K=100 separated sector cyclotron is producing proton and deuteron beam for ISOL which generate rare isotopes to accelerate RI beam for basic science research. In K=100 separated sector cyclotron facilities, two 8 MeV sector focused cyclotrons will be used as an injector cyclotron for the main cyclotron. In this paper, an Azimuthally Varying Field (AVF) magnet for the 8 MeV injector cyclotron is designed to produce 8 MeV proton beam and 4MeV deuteron beam. All field simulations have been performed by OPERA-3D TOSCA for 3D magnetic field simulation. The assignments of these injector cyclotrons are generating 8 MeV, 1 mA proton beam and 4MeV deuteron beam that inject to the main cyclotron.

MOPCP083	Vacuum Simulation for Heavy Ion Beams in the AGOR-Cyclotron	cyclotron, ion, simulation, target	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.

MOPCP095	Experiment and Analysis: Partial Loss of Insulation Vacuum in K-500 Superconducting Cyclotron During Energization	cyclotron, superconducting-magnet, controls, extraction	248
	P. Bhattacharyya, M. Ahammed, S. Bandyopadhyay, R.K. Bhandari, U. Bhunia, J. Chaudhuri, A. De, A. Dutta Gupta, C. Mallik, A. Mukherjee, C. Nandi, U. Panda, S. Saha, S. Saha DAE/VECC, Calcutta, India
	At higher currents in superconducting coil of K-500 Superconducting cyclotron, it was found that the insulation vacuum surrounding the LHe vessel gets worsen with increased current in the coil,finally leading to slow dump of power of the coil. This is a limitation for further increasing current value in the superconducting magnet coil. But once the current value returned to zero, vacuum reading reaches its initial value. Experiment & analysis have been done to quantify the contribution of molecular gas conduction on heat load because of this partial loss of insulation vacuum. Experiment was done to quantify how much betterment in terms of heat load is possible by incorporating additional vacuum pump. The cryostat safety analysis because of loss of insulation vacuum has become very important at this new scenario. Analysis has been done to know what could be the maximum pressure rise with time in case of loss of vacuum. This data has been used to know what should be the relieving mass flow rate to avoid any pressure burst accident. Finally this data has been compared with the existing relief valve. It is found that the existing safety system can take care of such incident.

MOPCP100	Axial Injection Beam Line of a Compact Cyclotron	ion, cyclotron, injection, ion-source	254
	J.Q. Zhang, Y. Cao, L.Z. Ma, A. Shi, M.T. Song, L.P. Sun, X.T. Yang, Q.G. Yao, Z.M. You, X.Q. Zhang, X.Z. Zhang, H.W. Zhao, J.H. Zheng IMP, Lanzhou, People's Republic of China
	Axial injection beam line of the therapy cyclotron is presented. It is intended for transportation of the C⁵⁺ ion beam obtained in the permanent magnet ion source. The beam line is only 3.486 m from the ion source to the entrance of spiral inflector, it consists of two sets glasser lens, one set double 90° bend magnet, one quadrupole lens and two solenoid lens. A big vacuum chamber is installed in the vertical part of the beam line, the sinusoidal buncher, the Faraday cap, the slit collimator and chopper are located in the vacuum chamber. The sinusoidal buncher is used for increasing of the seizing efficiency. The Faraday cap is used for the beam diagnostics. The bend magnet with the slit collimator is used for choice of C⁵⁺ ion beam. The chopper is used for choice of the beam utilizing time.

TUM2CCO02	First Beam Acceleration in Kolkata Superconducting Cyclotron and Its Present Status	cyclotron, extraction, ion, ion-source	292
	C. Mallik, R.K. Bhandari DAE/VECC, Calcutta, India
	Major systems of the superconducting cyclotron at Variable Energy Cyclotron Centre (VECC), Kolkata were functional and integrated by May 2009. After achieving the required acceleration condition internal beam trials were started in July 2009. First internal beam was observed on borescope viewer on August 14th. Ne³⁺ beam at 14 MHz was accelerated to full extraction radius and nuclear reaction observed on August 25th. The trials were not without difficulty and several problems did crop up during the initial phase. Major problems encountered were related to obtaining sufficient dee voltages primarily due to ceramic insulator degradation leading to vacuum breakdown. Earlier the 14 GHz ECR ion source was connected with injection line without much difficulty. The cyclotron magnet with the cryostat has been running smoothly and quite a valuable experience has been gained over the years. An analogue beam was also accelerated before taking a shutdown for installation of extraction system and augmentation of cryogenic plant. Very soon beam extraction and transportation to the experimental area will be started.
	Slides TUM2CCO02 [5.726 MB]

TUA2CIO01	Progress on Construction of CYCIAE-100	controls, extraction, ion, site	308
	T.J. Zhang, Z.G. Li, Y.L. Lu CIAE, Beijing, People's Republic of China
	As a driving accelerator for RIB production, CYCIAE-100 will provide proton beam of 75MeV~100MeV with an intensity of 200 μA~500 μA. The design for each system has been accomplished and about 50% of fabricating work has been finished. The main magnet manufacture has entered the fine machining stage. Two main magnet coils have been completed, two 100 kW RF power supplies and transmission lines are tested with full output power, and the main vacuum chamber and main magnet elevating system will be completed soon. The construction designs and market surveys for other systems are finished and ready for purchase. Some key design and technology experiments are in process and significant results have been achieved in verifications. The Comprehensive Test Stand (CRM) has successfully passed the authoritative certification, and an important progress has been made for a full scale experimental RF cavity and its frequency and Q value measured agree well with the numerical data. The certification test of vacuum cryo-panel structure has been finished with valuable information to cryo-panel design. Key technical problems related to CYCIAE-100 are being solved along with the progress.
	Slides TUA2CIO01 [11.584 MB]

WEM2CCO02	Operating Experience with the RF System for Superconducting Ring Cyclotron of RIBF	cyclotron, acceleration, cryogenics, pick-up	338
	N. Sakamoto, M. Fujimaki, A. Goto, O. Kamigaito, M. Kase, R. Koyama, K. Suda, K. Yamada, S. Yokouchi RIKEN Nishina Center, Wako, Japan
	Since December 2006, Superconducting Ring Cyclotron (SRC) has been operational. Up to now, the beams of ²³⁸U, ⁴⁸Ca, pol-d, N, ⁴He have been provided for nuclear physics experiments. The SRC consists of 6 superconducting sector magnets, 4 accelerating cavities and one flattop cavity. Designed value of the acceleration voltage is 2 MV/turn. The gap voltage of 600 kV is excited with 130 kW rf power in the accelerating cavity. The cavities have been installed at four valley regions of 6 sector magnets and are exposed to a strong stray field of superconducting magnets. The strength of the magnetic field is as large as a few kilogauss. It is found that the condition of multipactor depends drastically on the strength of the stray field. How to treat the multipactor is one of the most important issues for stable operation of the SRC. This paper will discuss on our efforts to settle the problem concerning the cavities. By improving the vacuum, cooling, surface treatment and so on, we finally succeeded to minimize the break time due to the rf break down of the SRC cavities during experiments.
	Slides WEM2CCO02 [9.291 MB]

WEM2CCO03	Disturbance Effects Caused by RF Power Leaking Out From Cavities in the PSI Ringcyclotron	plasma, septum, cyclotron, proton	341
	J.M. Humbel PSI-LRF, Villigen, PSI, Switzerland H. Zhang PSI, Villigen, Switzerland
	While commissioning the PSI high intensity proton beam facility after the shutdown 2010 direct and indirect phenomena of interaction between the electrostatic septa of the injection and extraction region and the RF power, leaking out from the cavities occurred in the Ringcyclotron. As an indirect influence RF fields outside the cavities generate plasma clouds at the edge of magnet poles. Accelerated plasma ions sputtered metallic atoms form the vacuum chamber wall, which then covered the insulator surface with an electrically conductive layer. The septum therefore had to be replaced. Directly RF power, dissipated from the third harmonic cavity was redirected by a beam stopper in such a way, that a linear correlation between the RF pick up signal monitored at the extraction septum EEC and the leak current across the septum insulator could be observed. As an instant mending action the beam stopper, which is not permanently used, has been removed. The leaking out of RF power from a cavity is known to depend on vertical asymmetry. With asymmetrical settings of the hydraulic tuning system we will try to minimize this disturbing effect.
	Slides WEM2CCO03 [3.166 MB]

THM1CIO02	Acceleration above the Coulomb Barrier - Completion of the ISAC-II Project at TRIUMF	linac, acceleration, ion, cyclotron	359
	R.E. Laxdal TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	The ISAC-II project at TRIUMF was proposed to boost the final energy of the radioactive ion beams of the TRIUMF ISAC facility above the Coulomb barrier. The nominal goal of 6.5 MeV/u for ions with A/q=6 was recently achieved. The ISAC-II post-accelerator consists of 40 MV of installed heavy ion superconducting linac to broaden the energy reach and a charge state booster to broaden the mass reach. Details of the project and the ISAC-II commissioning and operation will be presented.
	Slides THM1CIO02 [3.619 MB]

Paper

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Other Keywords

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MOM2CCO03

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

beam-losses, ion, cyclotron, acceleration

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]

MOA2CCO02

Current Status of the Cyclotron Facilities and Future Projects at iThemba Labs

controls, cyclotron, ion, proton

42

J.L. Conradie, L.S. Anthony, A.H. Botha, M.A. Crombie, J.G. De Villiers, J.L.G. Delsink, W. Duckitt, D.T. Fourie, M.E. Hogan, I.H. Kohler, C. Lussi, R.H. McAlister, H.W. Mostert, S.S. Ntshangase, J.V. Pilcher, P.F. Rohwer, M. Sakildien, N. Stodart, R.W. Thomae, M.J. Van Niekerk, D. de Villiers, P.A. van Schalkwyk
iThemba LABS, Somerset West, South Africa
C. Böhme
UniDo/IBS, Dortmund, Germany
J. Dietrich
FZJ, Jülich, Germany
Z. Kormány
ATOMKI, Debrecen, Hungary

For nearly 25 years the cyclotron facilities at iThemba LABS have been utilized for radioisotope production, nuclear physics research, and proton and neutron therapy. The aging systems require continual upgrading and replacement to limit interruptions to the scheduled beam delivery. The distributed computer control system is being migrated to a system running on the EPICS platform. The analogue low-level RF control systems will be replaced with digital systems. The Minimafios ECR ion source has been replaced with an ECR source from the former Hahn Meitner Institute and a second source, based on the design of the Grenoble test source, will be commissioned later this year. To increase the production of radio-isotopes, the 66 MeV proton beam is split to deliver beam simultaneously to two production targets. The first result with the beam splitter will be reported. A beam phase measurement system comprising 21 fixed probes has been installed in the separated sector cyclotron. Progress with these projects and the status of the facilities will be presented. Proposals for new facilities for proton therapy and for acceleration of radioactive beams will also be discussed.

Slides MOA2CCO02 [4.496 MB]

MOA2CCO03

Status of the LBNL 88-Inch Cyclotron High-Voltage Injection Upgrade Project

cyclotron, ion, injection, ion-source

45

K. Yoshiki Franzen, P.W. Casey, A. Hodgkinson, M. Kireeff Covo, D. Leitner, C.M. Lyneis, L. Phair, P. Pipersky
LBNL, Berkeley, California, USA

The goal of the project includes design of a new center region that allows external beam injection at injection voltages between 20 and 30 kV for high intensity beams. This new center region will make use of a spiral inflector to eliminate the use of a gridded mirror for high intensity beams. At the same time the mechanical design of the new center region must be flexible enough to allow use of the current center region for less intense beams. The use of two or more different center regions is necessary to cover the wide range of operation parameter space utilized by the 88-Inch Cyclotron Nuclear Science and Applied research program. The project also includes HV upgrades of the external injection lines and HV insulation of the AECR and VENUS source with the goal to provide focusing for beams up to 25 kV or if feasible up to 30 kV. The current spiral inflector design is based on extensive 3D FEM simulations which results will be presented. In addition results from ongoing efforts to improve on the transport efficiency from the AECR ion source to the current mirror inflector will be discussed.

Slides MOA2CCO03 [1.359 MB]

MOPCP025

Construction of New Injector LINAC at RIBF

linac, rfq, impedance, ion

102

K. Yamada, S. Arai, M. Fujimaki, T. Fujinawa, N. Fukunishi, A. Goto, Y. Higurashi, E. Ikezawa, O. Kamigaito, M. Kase, M. Komiyama, K. Kumagai, T. Maie, T. Nakagawa, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, H. Watanabe, Y. Watanabe, Y. Yano, S. Yokouchi
RIKEN Nishina Center, Wako, Japan
H. Fujisawa
Kyoto ICR, Uji, Kyoto, Japan
Y. Sato
KEK, Ibaraki, Japan

A new additional linac injector called RILAC2 has been constructed at the RIKEN Nishina Center so that RIBF experiments and synthesis of super-heavy element can be carried out independently. The RILAC2 consists of a 28-GHz superconducting ECR ion source (SC-ECRIS), a low-energy beam transport with a prebuncher, a four-rod RFQ linac, three drift-tube linac tanks (DTL1-3), a rebuncher between the RFQ and DTL1, and strong quadrupole magnets that were placed between the rf resonators for the transverse focusing. Very heavy ions with mass-to-charge ratio of 7, such as ¹³⁶Xe²⁰⁺ and ²³⁸U³⁵⁺, are accelerated up to an energy of 680 keV/u in the cw mode and injected into the RRC without charge stripping. The rf resonators excluding the pre-buncher are operated at a fixed rf frequency of 36.5 MHz, whereas the pre-buncher is operated at 18.25 MHz. The basic design of the RILAC2 was finished in 2006 and the construction has started since the budget was approved at the end of FY2008. The SC-ECRIS is installed in a new room, and other equipments are placed in the existing AVF-cyclotron vault. This contribution mainly presents the details of the construction of linac part.

MOPCP058

Commissioning Experience of the RF System of K500 Superconducting Cyclotron at VECC

cyclotron, controls, radio-frequency, impedance

162

S.S. Som, R.K. Bhandari, P. Gangopadhyay, A. Mandal, S.P. Pal, P.R. Raj, S. Saha, S. Seth
DAE/VECC, Calcutta, India

Funding: Department of Atomic Energy, Govt. of India.
Radio frequency system of Superconducting cyclotron at VECC, has been developed to achieve accelerating voltage of 100 kV max. with frequency, amplitude and phase stability of 0.1 ppm, 100 ppm and ±0.5 degree respectively within 9~27 MHz frequency. Each of the three half-wave coaxial cavity is fed with rf power (80kW max.) from a high power final rf amplifier based on Eimac 4CW150,000E tetrodes. Initially, the whole three-phase RF system has been tuned for operation with RF power to the cavities at 19.1994 MHz and thereafter commissioned the cyclotron with neon 3+ beam at external radius at 14.0 MHz. In this paper, we present brief description of the rf system and behaviour observed during initial conditioning of the cavities with rf power and the way to get out of multipacting zone together with discussion on our operational experience. We have so far achieved dee voltage up to 52 kV at 14 MHz with 20 kW of RF power fed at each of the three dees and achieved vacuum level of 4.5 x 10^-7 mbar inside the beam chamber. We also present discussion on the problems and failures of some RF components during commissioning stage and rectifications done to solve the same.

MOPCP059

Theoritical Analysis and Fabrication of Coupling Capacitor for K500 Superconducting Cyclotron at Kolkata

coupling, cyclotron, extraction, radio-frequency

165

M. Ahammed, R.K. Bhandari, P. Bhattacharyya, J. Chaudhuri, M.K. Dey, A. Dutta Gupta, B. Hemram, B.C. Mandal, N. Mandal, B. Manna, S. Murali, Y.E. Rao, S. Saha, S. Sur
DAE/VECC, Calcutta, India

K500 SC cyclotron has already been constructed and commissioned after spiraling Ne³⁺ internal beam with 70 nA upto extraction radius(670 mm) at Variable Energy Cyclotron Centre at Kolkata, India. Several problems have been experienced related to the coupling capacitor of the radio frequency system including it's sever burning during commissioning of the cyclotron. Making of the dissimilar joints between alumina ceramic and copper of the coupling capacitor demands the usage of vacuum furnace to avoid the cracking of the ceramic. Therefore exhaustive analysis has been carried out to facilitate the in-house fabrication of the coupling capacitor without using the vacuum furnace in case of emergency. The maximum allowable rate of temperature rise for the ceramic and the optimum thickness ration of the copper to ceramic has been estimated. Finally fabrication of the coupling capacitor has been carried out in-house without employing vacuum furnace. At present the coupling capacitor is performing well as maximum 57 kV DEE voltages were been achieved the till date. This paper presents the details of the analysis and experiences gain during the fabrication of the coupling capacitor.

MOPCP060

Design, Construction and Commissioning of the 100 kW RF Amplifier for CYCIAE-100

cyclotron, site, resonance, factory

168

Z.G. Yin, B. Ji, Z.G. Li, T.J. Zhang, Z.L. Zhao
CIAE, Beijing, People's Republic of China
S.D. Wei, H.C. Xiao, Y. Xie
CASIC, Beijing, People's Republic of China

As a major part of the BRIF project, the 100 MeV high intensity cyclotron being constructed at CIAE, CYCIAE-100, will provide 200 μA proton beam ranging from 75 MeV to 100 MeV for RIB production. Two identical 100 kW RF amplifiers will be used to drive two cavities independently to accelerate H⁻ beam up to 100 MeV. The detail technical specification has been investigated, fixed, and initial design has been finished by CIAE. Then, the construction design and manufacture is implemented by China Academy of Aero and Space, and the on site commissioning is successful by mutual efforts. The final commissioning is under way with a full scale prototype cavity at CIAE. A general description of the CYCIAE-100 RF system design will be given, as well as the review of 100 kW amplifier design. In the commissioning of the amplifier with dummy load, different high order resonances are found when operated at different frequencies between 42 MHz to 46 MHz. An equivalent circuit model is carried out to hunt down the problems. The model and related analysis will be reported together with the process and results of high power test with the cavity load through ~35 meters six inch rigid transmission line.

MOPCP073

The Vacuum System of HIRFL Cyclotrons

cyclotron, ion, heavy-ion, extraction

195

X.T. Yang, J. Meng, J.H. Zhang
IMP, Lanzhou, People's Republic of China

HIRFL has 2 cyclotrons: a sector focus cyclotron (SFC) and a separate sector cyclotron (SSC). SFC was built in 1957. In the past 50 years, the vacuum system of SFC has been upgraded for three times. The vacuum chamber was redesigned to double-deck at the third upgrade. The working pressure in beam chamber was improved from 10^-6 mbar to 10^-8 mbar. SFC has delivered Pb, Bi and U beams in the past few years since the last upgrading of its vacuum chamber. SSC began to operate in 1987. The vacuum chamber of SSC has a volume of 100m³. 8 cryopumps keep the pressure from 4×10^-7 mbar to 8×10^-8 mbar depending on the used pump numbers (2~8). In the past 20 years, because of the contamination of oil vapour and leaks occurred in some components inside the SSC vacuum chamber, the vacuum condition has worsened than the beginning. It is a big problem to accelerate the heavier ions. The upgrade for the SSC vacuum system will be an urgent task for us. The rough pumping system of both SFC and SSC will be rebuilt recently. The oil pump units will be changed by large dry mechanical pumps. As a result, the oil vapour in two cyclotrons will be eliminated and the vacuum condition of them will be improved.

MOPCP075

Cyclotron Vacuum Model and H⁻ Gas Stripping Losses

cyclotron, ion, extraction, target

200

V. Nuttens, M. Abs, J.L. Delvaux, Y. Jongen, W.J.G.M. Kleeven, L. Medeiros-Romao, M. Mehaudens, T. Servais, T. Vanderlinden, P. Verbruggen
IBA, Louvain-la-Neuve, Belgium

Many proton cyclotrons take the advantage of stripping for the extraction, by accelerating H⁻ ions. However, before extraction, the negative ion beam can suffer losses from stripping by the residual gas. The higher is the pressure, the higher the losses. Moreover, the stripped beam will be stopped on the inner wall of the cyclotron, inducing an additional degassing and increasing the pressure and hence losses in the cyclotron. For high beam current, degassing can be too large compared to the pumping capacity and the beam transmission can drop down to zero. The pressure inside the cyclotron has therefore a large impact on the current that can be extracted from the cyclotron. A simple model has been set up at IBA to determine the vacuum pressure in the hills and in the valleys of the Cyclone 70 cyclotron. The transmission is then computed by integration of the gas stripping cross-section along the ion orbits in the cyclotron. Pressure and transmission provided by the model are in good agreement with experimental data in the ARRONAX Cyclone 70 cyclotron installed in Nantes.

MOPCP076

Operational Experience of Superconducting Cyclotron Magnet at VECC, Kolkata

controls, cyclotron, cryogenics, coupling

203

U. Bhunia, M. Ahmed, R.K. Bhandari, T. Bhattacharyya, M.K. Dey, R. Dey, A. Dutta, A. Dutta Gupta, C. Mallik, C. Nandi, Z.A. Naser, G.P. Pal, U. Panda, S. Paul, J. Pradhan, S. Saha
DAE/VECC, Calcutta, India

The Kolkata Superconducting cyclotron magnet has been operational in the center since last few years and enabled us to extensively map magnetic fields over a year covering the operating range of the machine and successful commissioning of internal beam. The magnet cryostat coupled with the liquid helium refrigerator performs satisfactorily with moderate currents (<550A) in both the coils. The superconducting coil did not undergo any training and over the years has not suffered from any quench. Author would share the experience and difficulties of enhanced overall heat load to the liquid helium refrigerator at higher excitations of coils. This creates instability in the operation of liquid helium refrigerator and finally leads to slow dump. Rigorous study has been carried out in this regard to understand the problems and operational logic of liquid helium refrigerator has been modified accordingly to alleviate from. Some other measures have also been taken from cryostat and cryogenic distribution point of view in order to reduce the heat load at higher excitations.

MOPCP077

Median Plane Effects and Measurement Method for Radial Component of Magnetic Field in AVF Cyclotrons

cyclotron, extraction, alignment, simulation

206

N.A. Morozov, G.A. Karamysheva
JINR, Dubna, Moscow Region, Russia
P. Shishlyannikov
JINR/DLNP, Dubna, Moscow region, Russia

The median plane of the magnetic field in AVF cyclotrons rather often does not coincide with the mid-plane of their magnetic system. The idea of an effective median plane formulated by J.I.M.Botman and H.L.Hagedorn [*] for the central region of the cyclotron is extended to the entire working region and tolerances for the horizontal components of the magnetic field are estimated. Equipment based on the search coils is proposed and used for measurement of the radial component of the magnetic field and for correction of the magnetic field median plane.
[*] J.I.M.Botman, H.L.Hagedorn, 'Median Plane Effects in the Eindhoven AVF Cyclotron', IEEE Trans. On Nucl. Science, Vol. NS-28, No.3, p.2128.

MOPCP082

Design Study of AVF Magnet for Compact Cyclotron

cyclotron, simulation, proton, extraction

218

H.W. Kim, J.-S. Chai, B.N. Lee, J.H. Oh
SKKU, Suwon, Republic of Korea

K=100 separated sector cyclotron and its injector cyclotron design is started on April, 2010 at Sungkyunkwan University. The main purpose of the K=100 separated sector cyclotron is producing proton and deuteron beam for ISOL which generate rare isotopes to accelerate RI beam for basic science research. In K=100 separated sector cyclotron facilities, two 8 MeV sector focused cyclotrons will be used as an injector cyclotron for the main cyclotron. In this paper, an Azimuthally Varying Field (AVF) magnet for the 8 MeV injector cyclotron is designed to produce 8 MeV proton beam and 4MeV deuteron beam. All field simulations have been performed by OPERA-3D TOSCA for 3D magnetic field simulation. The assignments of these injector cyclotrons are generating 8 MeV, 1 mA proton beam and 4MeV deuteron beam that inject to the main cyclotron.

MOPCP083

Vacuum Simulation for Heavy Ion Beams in the AGOR-Cyclotron

cyclotron, ion, simulation, target

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.

MOPCP095

Experiment and Analysis: Partial Loss of Insulation Vacuum in K-500 Superconducting Cyclotron During Energization

cyclotron, superconducting-magnet, controls, extraction

248

P. Bhattacharyya, M. Ahammed, S. Bandyopadhyay, R.K. Bhandari, U. Bhunia, J. Chaudhuri, A. De, A. Dutta Gupta, C. Mallik, A. Mukherjee, C. Nandi, U. Panda, S. Saha, S. Saha
DAE/VECC, Calcutta, India

At higher currents in superconducting coil of K-500 Superconducting cyclotron, it was found that the insulation vacuum surrounding the LHe vessel gets worsen with increased current in the coil,finally leading to slow dump of power of the coil. This is a limitation for further increasing current value in the superconducting magnet coil. But once the current value returned to zero, vacuum reading reaches its initial value. Experiment & analysis have been done to quantify the contribution of molecular gas conduction on heat load because of this partial loss of insulation vacuum. Experiment was done to quantify how much betterment in terms of heat load is possible by incorporating additional vacuum pump. The cryostat safety analysis because of loss of insulation vacuum has become very important at this new scenario. Analysis has been done to know what could be the maximum pressure rise with time in case of loss of vacuum. This data has been used to know what should be the relieving mass flow rate to avoid any pressure burst accident. Finally this data has been compared with the existing relief valve. It is found that the existing safety system can take care of such incident.

MOPCP100

Axial Injection Beam Line of a Compact Cyclotron

ion, cyclotron, injection, ion-source

254

J.Q. Zhang, Y. Cao, L.Z. Ma, A. Shi, M.T. Song, L.P. Sun, X.T. Yang, Q.G. Yao, Z.M. You, X.Q. Zhang, X.Z. Zhang, H.W. Zhao, J.H. Zheng
IMP, Lanzhou, People's Republic of China

Axial injection beam line of the therapy cyclotron is presented. It is intended for transportation of the C⁵⁺ ion beam obtained in the permanent magnet ion source. The beam line is only 3.486 m from the ion source to the entrance of spiral inflector, it consists of two sets glasser lens, one set double 90° bend magnet, one quadrupole lens and two solenoid lens. A big vacuum chamber is installed in the vertical part of the beam line, the sinusoidal buncher, the Faraday cap, the slit collimator and chopper are located in the vacuum chamber. The sinusoidal buncher is used for increasing of the seizing efficiency. The Faraday cap is used for the beam diagnostics. The bend magnet with the slit collimator is used for choice of C⁵⁺ ion beam. The chopper is used for choice of the beam utilizing time.

TUM2CCO02

First Beam Acceleration in Kolkata Superconducting Cyclotron and Its Present Status

cyclotron, extraction, ion, ion-source

292

C. Mallik, R.K. Bhandari
DAE/VECC, Calcutta, India

Major systems of the superconducting cyclotron at Variable Energy Cyclotron Centre (VECC), Kolkata were functional and integrated by May 2009. After achieving the required acceleration condition internal beam trials were started in July 2009. First internal beam was observed on borescope viewer on August 14th. Ne³⁺ beam at 14 MHz was accelerated to full extraction radius and nuclear reaction observed on August 25th. The trials were not without difficulty and several problems did crop up during the initial phase. Major problems encountered were related to obtaining sufficient dee voltages primarily due to ceramic insulator degradation leading to vacuum breakdown. Earlier the 14 GHz ECR ion source was connected with injection line without much difficulty. The cyclotron magnet with the cryostat has been running smoothly and quite a valuable experience has been gained over the years. An analogue beam was also accelerated before taking a shutdown for installation of extraction system and augmentation of cryogenic plant. Very soon beam extraction and transportation to the experimental area will be started.

Slides TUM2CCO02 [5.726 MB]

TUA2CIO01

Progress on Construction of CYCIAE-100

controls, extraction, ion, site

308

T.J. Zhang, Z.G. Li, Y.L. Lu
CIAE, Beijing, People's Republic of China

As a driving accelerator for RIB production, CYCIAE-100 will provide proton beam of 75MeV~100MeV with an intensity of 200 μA~500 μA. The design for each system has been accomplished and about 50% of fabricating work has been finished. The main magnet manufacture has entered the fine machining stage. Two main magnet coils have been completed, two 100 kW RF power supplies and transmission lines are tested with full output power, and the main vacuum chamber and main magnet elevating system will be completed soon. The construction designs and market surveys for other systems are finished and ready for purchase. Some key design and technology experiments are in process and significant results have been achieved in verifications. The Comprehensive Test Stand (CRM) has successfully passed the authoritative certification, and an important progress has been made for a full scale experimental RF cavity and its frequency and Q value measured agree well with the numerical data. The certification test of vacuum cryo-panel structure has been finished with valuable information to cryo-panel design. Key technical problems related to CYCIAE-100 are being solved along with the progress.

Slides TUA2CIO01 [11.584 MB]

WEM2CCO02

Operating Experience with the RF System for Superconducting Ring Cyclotron of RIBF

cyclotron, acceleration, cryogenics, pick-up

338

N. Sakamoto, M. Fujimaki, A. Goto, O. Kamigaito, M. Kase, R. Koyama, K. Suda, K. Yamada, S. Yokouchi
RIKEN Nishina Center, Wako, Japan

Since December 2006, Superconducting Ring Cyclotron (SRC) has been operational. Up to now, the beams of ²³⁸U, ⁴⁸Ca, pol-d, N, ⁴He have been provided for nuclear physics experiments. The SRC consists of 6 superconducting sector magnets, 4 accelerating cavities and one flattop cavity. Designed value of the acceleration voltage is 2 MV/turn. The gap voltage of 600 kV is excited with 130 kW rf power in the accelerating cavity. The cavities have been installed at four valley regions of 6 sector magnets and are exposed to a strong stray field of superconducting magnets. The strength of the magnetic field is as large as a few kilogauss. It is found that the condition of multipactor depends drastically on the strength of the stray field. How to treat the multipactor is one of the most important issues for stable operation of the SRC. This paper will discuss on our efforts to settle the problem concerning the cavities. By improving the vacuum, cooling, surface treatment and so on, we finally succeeded to minimize the break time due to the rf break down of the SRC cavities during experiments.

Slides WEM2CCO02 [9.291 MB]

WEM2CCO03

Disturbance Effects Caused by RF Power Leaking Out From Cavities in the PSI Ringcyclotron

plasma, septum, cyclotron, proton

341

J.M. Humbel
PSI-LRF, Villigen, PSI, Switzerland
H. Zhang
PSI, Villigen, Switzerland

While commissioning the PSI high intensity proton beam facility after the shutdown 2010 direct and indirect phenomena of interaction between the electrostatic septa of the injection and extraction region and the RF power, leaking out from the cavities occurred in the Ringcyclotron. As an indirect influence RF fields outside the cavities generate plasma clouds at the edge of magnet poles. Accelerated plasma ions sputtered metallic atoms form the vacuum chamber wall, which then covered the insulator surface with an electrically conductive layer. The septum therefore had to be replaced. Directly RF power, dissipated from the third harmonic cavity was redirected by a beam stopper in such a way, that a linear correlation between the RF pick up signal monitored at the extraction septum EEC and the leak current across the septum insulator could be observed. As an instant mending action the beam stopper, which is not permanently used, has been removed. The leaking out of RF power from a cavity is known to depend on vertical asymmetry. With asymmetrical settings of the hydraulic tuning system we will try to minimize this disturbing effect.

Slides WEM2CCO03 [3.166 MB]

THM1CIO02

Acceleration above the Coulomb Barrier - Completion of the ISAC-II Project at TRIUMF

linac, acceleration, ion, cyclotron

359

R.E. Laxdal
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

The ISAC-II project at TRIUMF was proposed to boost the final energy of the radioactive ion beams of the TRIUMF ISAC facility above the Coulomb barrier. The nominal goal of 6.5 MeV/u for ions with A/q=6 was recently achieved. The ISAC-II post-accelerator consists of 40 MV of installed heavy ion superconducting linac to broaden the energy reach and a charge state booster to broaden the mass reach. Details of the project and the ISAC-II commissioning and operation will be presented.

Slides THM1CIO02 [3.619 MB]