CYCLOTRONS 2010 - Classification: 11 Radio Frequency Systems

Paper

Title

Page

A Compact Solution for DDS-Generator, Turn-on and Protections in RF Accelerator Systems

159

A.C. Caruso, F. Consoli, A. Spartà
INFN/LNS, Catania, Italy
A. Longhitano
ALTEK, San Gregorio (CATANIA), Italy

A single compact rack that includes a Direct Digital Synthesizer generator, a turn-on and protection system provides the smart solution in RF accelerator systems. It synthesizes a high stable RF signal up to 120 MHz, turns the power on into the RF cavities through a step-ramp modulator, protects the RF system against mismatching, sparks and multipactoring. A preliminary prototype has been designed, assembled and tested on the RF system of the k-800 superconducting cyclotron at Infn-Lns. This solution is part of the new computer-based RF control system. The hardware, software, and first test results will be shown in this paper.

MOPCP058

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

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

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

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.

MOPCP061

RF Cavity Simulations for Superconducting C400 Cyclotron

171

G.A. Karamysheva, A.A. Glazov, S. Gurskiy, N.A. Morozov
JINR, Dubna, Moscow Region, Russia
M. Abs, Y. Jongen, W.J.G.M. Kleeven, S. Zaremba
IBA, Louvain-la-Neuve, Belgium
O. Karamyshev
JINR/DLNP, Dubna, Moscow region, Russia

Compact superconducting isochronous cyclotron C400 has designed at IBA (Belgium) in collaboration with the JINR (Dubna). This cyclotron will be the first cyclotron in the world capable of delivering protons, carbon and helium ions for therapeutic use. ¹²C⁶⁺ and ⁴He²⁺ ions will be accelerated to 400 MeV/u energy and extracted by electrostatic deflector, H²⁺ ions will be accelerated to the energy 265 MeV/u and extracted by stripping. It is planed to use two normal conducting RF cavities for ion beam acceleration in cyclotron C400. Computer model of the double gap delta RF cavity with 4 stems was developed in is a general-purpose simulation software CST STUDIO SUITE. Necessary resonant frequency and increase of the voltage along the gaps were achieved. Optimization of the RF cavity parameters leads us to the cavity with quality factor about 14000, RF power dissipation is equal to about 50 kW per cavity.

MOPCP062

TRIUMF Cyclotron Booster Frequency Tuning System

174

Q. Zheng, K. Fong, M.P. Laverty
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

For auto frequency tuning of TRIUMF cyclotron booster, a new control module based upon VXI Bus has been designed, tested and put into commission. This new auto tuning control module, which replaced the old analogue control box, has more features including the implementation of PIC16C71 microprocessor to generate Pulse Width Modulation (PWM) pulse, the utilization of digital RF phase detector and the most important aspect of computer control capability. Thus, the resonant frequency of cyclotron booster RF cavity is tuned automatically by this control module and the reflected RF power is kept at the minimum level in the operation.

MOPCP064

Amplifier Test Stand for the CRM Cyclotron

177

Z.G. Yin, K. Fei, B. Ji, P.Z. Li, G.S. Liu, G.F. Song, T.J. Zhang
CIAE, Beijing, People's Republic of China
C.J. Yu
CASIC, Beijing, People's Republic of China

Abstract: The final stage amplifier stability proves to be an important issue in the process of commissioning CRM cyclotron at CIAE. An air cooled 4CX15,000 tube final stage has been designed to evaluate the anode circuit and neutralization, both of which are weak points of the CRM cyclotron amplifier. Instead of strip line, the design of the new anode structure adopts coaxial form, resulting in less chance of parasitic resonance in the circuits. A tunable neutralization circuits is also included in the design, giving an opportunity to better stability in high power operations. First, the instability in CRM RF system will be analyzed in this paper followed with the new amplifier designs including the tube working line calculations, input/output circuit calculations and finite integral simulations. The mechanical design for tube socket and the anode tank have been successfully carried out using the data provided in this paper. The final stage amplifier is then fabricated, assembled and commissioned. In the power test with dummy load, more than 9.2kW RF fundamental power is provided at the frequency of 44MHz.

MOPCP065

Closed Loop RF Tuning for Superconducitng Cyclotron at VECC

180

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

The RF system of Superconducting cyclotron has been operational within 9 - 27 MHz frequency. It has three tunable half-wave coaxial cavities as main resonators and three tunable RF amplifier cavities. A PC-based system takes care of stepper motor driven coarse tuning of cavities with positional accuracy ~20 μm and hydraulically driven three couplers and three trimmers. The couplers, in open loop, match the cavity impedance to 50 Ω in order to feed power from RF amplifier. Trimmers operate in closed loop for fine tuning the cavity, if detuned thermally at high RF power. The control logic has been simulated and finally implemented with Programmable Logic Controller (PLC). Precision control of trimmer (~20 μm) is essential to achieve the accelerating (Dee) voltage stability better than 100 ppm and also minimizing the RF power to maintain it. Phase difference between Dee-in and Dee-pick-off signals and the reflected power signals (from cavity) together act in closed loop for fine tuning of the cavity. The close loop PID control determines the final positioning of the trimmer in each power level and achieved the required voltage stability.

MOPCP067

Design and Primary Test of Full Scale Cavity of CYCIAE-100

183

B. Ji, P.Z. Li, J. Lin, G.S. Liu, G.F. Pan, Z.H. Wang, J.S. Xing, Z.G. Yin, S.P. Zhang, T.J. Zhang, Z.L. Zhao
CIAE, Beijing, People's Republic of China

The engineering of the RF cavity for cyclotron concerns several aspects of the system including vacuum, cooling, mechanical support etc, Sometime it is even more complex than the RF design itself. With limit space in a compact cyclotron, in order to achieve a voltage distribution of 60kV in central orbit and 120kV for outer orbit, a double stem double gap λ by 2 cavities has been designed for CYCIAE-100[1]. The RF resonance of the cavity is simulated [1] by finite integral codes, while the thermal analysis and mechanical tolerance are studied using other approaches [2, 3]. The mechanical design and fabrications is then carried out under these directions, resulting in a full scale cavity model. The simulations and the mechanical design will be reported in this paper, followed with low level measurement results of quality factor, shunt impedance curve along accelerating gap etc. After surface polishing, the measurement yields an unloaded Q value of 9300, which matches well with the simulation with a neglectable difference of several hundreds. The high power test of the cavity will be carried out later, and will be given in separate paper presented at this conference.
[1] Tianjue Zhang,et al, 100 MeV H⁻ Cyclotron as an RIB Driving Accelerator, CYC 2004
[2] Yuanjie Bi, et al, The Study on RF Cavity Tolerance for CYCIAE-100, CYC 2007
[3] S.M. Wei, et al, Thermal Analysis of RF Cavity for CYCIAE-100, CYC 2007

MOPCP068

Stable Operation of RF Systems for RIBF

186

K. Suda, M. Fujimaki, N. Fukunishi, M. Hemmi, O. Kamigaito, M. Kase, R. Koyama, K. Kumagai, N. Sakamoto, T. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan

At RIKEN RI-Beam Factory (RIBF), heavy ion beams are accelerated up to 345 MeV/u by using the RIKEN heavy ion linac (RILAC) and four ring cyclotrons. In order to provide high intensity beams up to 1puA, all the RF systems must be stable enough for a long term (a few weeks), within ±0.1% in voltages and ±0.1 degrees in phases. For a stable operation of RIBF, we have started to monitor for the RF voltages and phases for all the RF systems, and beam intensity and phases using lock-in amplifiers. We have investigated a degree of stability of the RF systems. Then, we have performed several improvements. The Automatic Gain Control units for RILAC were replaced for a better stability. It was found that the stability of RF systems was considerably affected by the fluctuation of reference signals. The fluctuation was mainly caused by the temperature dependence of power dividers used for a reference signal distribution. Therefore, we have changed the distribution method. The reference signal is first amplified to 40 dBm and divided by directional couplers, and they are delivered to low level circuits. The present degree of stability of the RF systems will be presented.

WEM2CIO01

High Power RF Systems and Resonators for Sector Cyclotrons

332

L. Stingelin, M. Bopp, M. Broennimann, J. Cherix, H. Fitze, M. Schneider, W. Tron
PSI, Villigen, Switzerland

In the framework of the high intensity upgrade of the PSI proton accelerator facility, it is planned to replace two existing 150 MHz resonators of the injector II cyclotron by two new 50 MHz resonators. The first prototype resonator has been manufactured by SDMS and first vacuum- and LLRF-tests were carried out. Tuners, coupler and pickups were mounted and high power RF tests are in progress at the teststand. A new building for the RF installation has been built and is ready to house the power amplifiers and LLRF-systems.

Slides WEM2CIO01 [3.497 MB]

WEM2CCO02

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

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]

Paper	Title	Page
MOPCP057	A Compact Solution for DDS-Generator, Turn-on and Protections in RF Accelerator Systems	159
	A.C. Caruso, F. Consoli, A. Spartà INFN/LNS, Catania, Italy A. Longhitano ALTEK, San Gregorio (CATANIA), Italy
	A single compact rack that includes a Direct Digital Synthesizer generator, a turn-on and protection system provides the smart solution in RF accelerator systems. It synthesizes a high stable RF signal up to 120 MHz, turns the power on into the RF cavities through a step-ramp modulator, protects the RF system against mismatching, sparks and multipactoring. A preliminary prototype has been designed, assembled and tested on the RF system of the k-800 superconducting cyclotron at Infn-Lns. This solution is part of the new computer-based RF control system. The hardware, software, and first test results will be shown in this paper.

MOPCP058	Commissioning Experience of the RF System of K500 Superconducting Cyclotron at VECC	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	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	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.

MOPCP061	RF Cavity Simulations for Superconducting C400 Cyclotron	171
	G.A. Karamysheva, A.A. Glazov, S. Gurskiy, N.A. Morozov JINR, Dubna, Moscow Region, Russia M. Abs, Y. Jongen, W.J.G.M. Kleeven, S. Zaremba IBA, Louvain-la-Neuve, Belgium O. Karamyshev JINR/DLNP, Dubna, Moscow region, Russia
	Compact superconducting isochronous cyclotron C400 has designed at IBA (Belgium) in collaboration with the JINR (Dubna). This cyclotron will be the first cyclotron in the world capable of delivering protons, carbon and helium ions for therapeutic use. ¹²C⁶⁺ and ⁴He²⁺ ions will be accelerated to 400 MeV/u energy and extracted by electrostatic deflector, H²⁺ ions will be accelerated to the energy 265 MeV/u and extracted by stripping. It is planed to use two normal conducting RF cavities for ion beam acceleration in cyclotron C400. Computer model of the double gap delta RF cavity with 4 stems was developed in is a general-purpose simulation software CST STUDIO SUITE. Necessary resonant frequency and increase of the voltage along the gaps were achieved. Optimization of the RF cavity parameters leads us to the cavity with quality factor about 14000, RF power dissipation is equal to about 50 kW per cavity.

MOPCP062	TRIUMF Cyclotron Booster Frequency Tuning System	174
	Q. Zheng, K. Fong, M.P. Laverty TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	For auto frequency tuning of TRIUMF cyclotron booster, a new control module based upon VXI Bus has been designed, tested and put into commission. This new auto tuning control module, which replaced the old analogue control box, has more features including the implementation of PIC16C71 microprocessor to generate Pulse Width Modulation (PWM) pulse, the utilization of digital RF phase detector and the most important aspect of computer control capability. Thus, the resonant frequency of cyclotron booster RF cavity is tuned automatically by this control module and the reflected RF power is kept at the minimum level in the operation.

MOPCP064	Amplifier Test Stand for the CRM Cyclotron	177
	Z.G. Yin, K. Fei, B. Ji, P.Z. Li, G.S. Liu, G.F. Song, T.J. Zhang CIAE, Beijing, People's Republic of China C.J. Yu CASIC, Beijing, People's Republic of China
	Abstract: The final stage amplifier stability proves to be an important issue in the process of commissioning CRM cyclotron at CIAE. An air cooled 4CX15,000 tube final stage has been designed to evaluate the anode circuit and neutralization, both of which are weak points of the CRM cyclotron amplifier. Instead of strip line, the design of the new anode structure adopts coaxial form, resulting in less chance of parasitic resonance in the circuits. A tunable neutralization circuits is also included in the design, giving an opportunity to better stability in high power operations. First, the instability in CRM RF system will be analyzed in this paper followed with the new amplifier designs including the tube working line calculations, input/output circuit calculations and finite integral simulations. The mechanical design for tube socket and the anode tank have been successfully carried out using the data provided in this paper. The final stage amplifier is then fabricated, assembled and commissioned. In the power test with dummy load, more than 9.2kW RF fundamental power is provided at the frequency of 44MHz.

MOPCP065	Closed Loop RF Tuning for Superconducitng Cyclotron at VECC	180
	A. Mandal, R.K. Bhandari, S.P. Pal, U. Panda, S. Saha, S. Seth, S.S. Som DAE/VECC, Calcutta, India
	The RF system of Superconducting cyclotron has been operational within 9 - 27 MHz frequency. It has three tunable half-wave coaxial cavities as main resonators and three tunable RF amplifier cavities. A PC-based system takes care of stepper motor driven coarse tuning of cavities with positional accuracy ~20 μm and hydraulically driven three couplers and three trimmers. The couplers, in open loop, match the cavity impedance to 50 Ω in order to feed power from RF amplifier. Trimmers operate in closed loop for fine tuning the cavity, if detuned thermally at high RF power. The control logic has been simulated and finally implemented with Programmable Logic Controller (PLC). Precision control of trimmer (~20 μm) is essential to achieve the accelerating (Dee) voltage stability better than 100 ppm and also minimizing the RF power to maintain it. Phase difference between Dee-in and Dee-pick-off signals and the reflected power signals (from cavity) together act in closed loop for fine tuning of the cavity. The close loop PID control determines the final positioning of the trimmer in each power level and achieved the required voltage stability.

MOPCP067	Design and Primary Test of Full Scale Cavity of CYCIAE-100	183
	B. Ji, P.Z. Li, J. Lin, G.S. Liu, G.F. Pan, Z.H. Wang, J.S. Xing, Z.G. Yin, S.P. Zhang, T.J. Zhang, Z.L. Zhao CIAE, Beijing, People's Republic of China
	The engineering of the RF cavity for cyclotron concerns several aspects of the system including vacuum, cooling, mechanical support etc, Sometime it is even more complex than the RF design itself. With limit space in a compact cyclotron, in order to achieve a voltage distribution of 60kV in central orbit and 120kV for outer orbit, a double stem double gap λ by 2 cavities has been designed for CYCIAE-100[1]. The RF resonance of the cavity is simulated [1] by finite integral codes, while the thermal analysis and mechanical tolerance are studied using other approaches [2, 3]. The mechanical design and fabrications is then carried out under these directions, resulting in a full scale cavity model. The simulations and the mechanical design will be reported in this paper, followed with low level measurement results of quality factor, shunt impedance curve along accelerating gap etc. After surface polishing, the measurement yields an unloaded Q value of 9300, which matches well with the simulation with a neglectable difference of several hundreds. The high power test of the cavity will be carried out later, and will be given in separate paper presented at this conference. [1] Tianjue Zhang,et al, 100 MeV H⁻ Cyclotron as an RIB Driving Accelerator, CYC 2004 [2] Yuanjie Bi, et al, The Study on RF Cavity Tolerance for CYCIAE-100, CYC 2007 [3] S.M. Wei, et al, Thermal Analysis of RF Cavity for CYCIAE-100, CYC 2007

MOPCP068	Stable Operation of RF Systems for RIBF	186
	K. Suda, M. Fujimaki, N. Fukunishi, M. Hemmi, O. Kamigaito, M. Kase, R. Koyama, K. Kumagai, N. Sakamoto, T. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan
	At RIKEN RI-Beam Factory (RIBF), heavy ion beams are accelerated up to 345 MeV/u by using the RIKEN heavy ion linac (RILAC) and four ring cyclotrons. In order to provide high intensity beams up to 1puA, all the RF systems must be stable enough for a long term (a few weeks), within ±0.1% in voltages and ±0.1 degrees in phases. For a stable operation of RIBF, we have started to monitor for the RF voltages and phases for all the RF systems, and beam intensity and phases using lock-in amplifiers. We have investigated a degree of stability of the RF systems. Then, we have performed several improvements. The Automatic Gain Control units for RILAC were replaced for a better stability. It was found that the stability of RF systems was considerably affected by the fluctuation of reference signals. The fluctuation was mainly caused by the temperature dependence of power dividers used for a reference signal distribution. Therefore, we have changed the distribution method. The reference signal is first amplified to 40 dBm and divided by directional couplers, and they are delivered to low level circuits. The present degree of stability of the RF systems will be presented.

WEM2CIO01	High Power RF Systems and Resonators for Sector Cyclotrons	332
	L. Stingelin, M. Bopp, M. Broennimann, J. Cherix, H. Fitze, M. Schneider, W. Tron PSI, Villigen, Switzerland
	In the framework of the high intensity upgrade of the PSI proton accelerator facility, it is planned to replace two existing 150 MHz resonators of the injector II cyclotron by two new 50 MHz resonators. The first prototype resonator has been manufactured by SDMS and first vacuum- and LLRF-tests were carried out. Tuners, coupler and pickups were mounted and high power RF tests are in progress at the teststand. A new building for the RF installation has been built and is ready to house the power amplifiers and LLRF-systems.
	Slides WEM2CIO01 [3.497 MB]

WEM2CCO02	Operating Experience with the RF System for Superconducting Ring Cyclotron of RIBF	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]