07 Accelerator Technology

T06 Room Temperature RF

Paper Title Page
THPEA001 Fabrication and Installation of Radio Frequency System for K500 Superconducting Cyclotron at Kolkata 3673
 
  • M. Ahammed, D. Adak, R.K. Bhandari, P. Bhattacharyya, J. Chaudhuri, M.K. Dey, A. Dutta Gupta, B. Hemram, B.C. Mandal, B. Manna, S. Murmu, H.K. Pandey, S. Saha, S. Sarkar, S.K. Singh, T. Viswanathan
    DAE/VECC, Calcutta
 
 

K500 Superconducting Cyclotron (SCC) is already commissioned successfully at VECC, Kolkata by accelerating Ne3+ internal beam with 70 nA beam current at 670 mm extraction radius. The Radio Frequency cavity of SCC is successfully operational since last two years. All these years were very challenging and worthy period from the point of view of gaining experience and knowledge by solving fabrication and assembly problems faced during construction of 10 m tall copper made coaxial RF cavities and tackling RF related commissioning problems. RF system operates within the frequency range of 9 to 27 MHz for generating maximum 100 kV DEE voltage. The construction of the RF system demands making of numerous critical soldering and brazing joints including joints between ceramic and copper along with maintaining close dimensional accuracies, assembly tolerances, mirror symmetricity, surface finish and utmost cleanliness. This paper presents the details of fabrication and installation procedures and their effects on the final performance of the cavities. It also highlights the problems faced during the commissioning process of the RF cavities.

 
THPEA002 RF Systems of the VEC-RIB Facility 3676
 
  • H.K. Pandey, A. Bandyopadhyay, A. Chakrabarti, S. Dechoudhury, D.P. Dutta, T.K. Mandi, V. Naik
    DAE/VECC, Calcutta
  • A.K. Basu, A. Kumar, K. P. Ray
    SAMEER, Mumbai
 
 

An isotope separator on-line Rare Isotope Beam (RIB) facility is presently under development at VECC, Kolkata around the existing K=130 room temp cyclotron. In first stage the low-energy (1.7 keV/u; q/A ≤ 1/14) RIB will be accelerated to about 470 keV/u in the Radio Frequency Quadrupole (RFQ) linac followed by three IH-LINAC. This consists of seven different rf systems for RFQ, three re-buncher and three IH-Linac cavities each operating in CW mode. The 3.4 meter rod type RFQ and the four gap λ/4 re-buncher is designed to operate at 37.8 MHz. The RFQ and re-buncher has been installed and successfully operated at CW rf power. The first beam testing for O5+ has been done with proper phase locking between rf transmitters. Two DTL accelerator systems consist of IH-mode tank operating at 37.8 MHz and other with 75.6 MHz. The first IH linac has been installed in beam line and tested with nominal RF power. The Second IH-linac cavity has been fabricated and is undergoing low power rf test. Two other buncher cavities are presently under development. The rf systems with low power as well as high power testing for above accelerator cavities will be described in this paper.

 
THPEA003 An Analytical Formulation for Prediction of Geometrical Dimensions of a Photocathode Gun for Desired RF Properties 3679
 
  • S. Lal, K.K. Pant
    RRCAT, Indore (M.P.)
  • S. Krishnagopal
    BARC, Mumbai
 
 

Tuning of a photocathode gun for desired RF properties of the pi mode, such as FB ~1, fpi = 2856 MHz, and beta ~1, requires precise tuning of the resonant frequency and beta of its independent cells. In this paper, we present a parametric and analytical formulation to predict geometrical dimensions of independent cells and the coupling slot on the full cell to obtain the desired pi mode RF parameters during operation, taking into account the effect of brazing and vacuum. We also compare results obtained from low power RF measurements on a photocathode gun with those predicted by the above formulation.

 
THPEA006 Beam Energy Upgrade of the Frascati FEL LINAC with a C-band RF System 3682
 
  • R. Boni, D. Alesini, M. Bellaveglia, G. Di Pirro, M. Ferrario, L. Ficcadenti, A. Gallo, F. Marcellini, E. Pace, B. Spataro, C. Vaccarezza
    INFN/LNF, Frascati (Roma)
  • A. Bacci
    Istituto Nazionale di Fisica Nucleare, Milano
  • A. Mostacci, L. Palumbo, V. Spizzo
    Rome University La Sapienza, Roma
  • C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
 
 

In the frame of the SPARC-X project, the energy of the Photo-Injector SPARC, in operation at INFN-LNF, will be upgraded from 180 to 250 MeV by replacing a low gradient S-band traveling wave accelerating section with two C-band units, designed and developed at LNF. The new system will consist of a 50 MW klystron, supplied by a pulsed modulator, to feed the high gradient C-band structures through a RF pulse compressor. This paper deals with the design of the full system, the C-band R&D activity and study of the related beam dynamics.

 
THPEA008 Experimental Characterization of the RF Gun Prototype for the SPARX-FEL Project 3688
 
  • L. Faillace, L. Palumbo
    Rome University La Sapienza, Roma
  • P. Frigola
    RadiaBeam, Marina del Rey
  • A. Fukasawa, B.D. O'Shea, J.B. Rosenzweig
    UCLA, Los Angeles, California
  • B. Spataro
    INFN/LNF, Frascati (Roma)
 
 

The quest for high brightness beams is a crucial key for the SPARX-FEL Project. In this paper, we present the design (including RF modeling, cooling, thermal and stress analyses as well as frequency detuning) of a single feed S-Band RF Gun capable of running near 500 Hz. An alternative design with dual feed has already been designed. Also, experimental results from the RF characterization of the prototype, including field measurements, are presented. The RF design follows the guidelines of the LCLS Gun, but the approach diverges significantly as far as the management of the cooling and mechanical stress is concerned. Finally, we examine the new proprietary approach of RadiaBeam Technologies for fabricating copper structures with intricate internal cooling geometries that may enable very high repetition rate.


* C.Limborg et al., "RF Design of the LCLS Gun".
** P. Frigola et al., "Development of solid freeform fabrication (SFF) for the production of RF Photoinjectors".

 
THPEA009 Construction Status of C-band Main Accelerator for XFEL/SPring-8 3691
 
  • T. Inagaki, N. Adumi, T. Hasegawa, H. Maesaka, S. Matsui, T. Sakurai, T. Shintake
    RIKEN/SPring-8, Hyogo
  • H. Kimura, C. Kondo, K. Shirasawa
    JASRI/SPring-8, Hyogo-ken
 
 

C-band (5712 MHz) accelerator is used as the main accelerator of the XFEL in SPring-8. Since the C-band generates a high accelerator gradient, as high as 35 MV/m, the total length of the 8-GeV accelerator fits within 400 m, including the injector and three bunch compressors. We use 64 C-band rf units, which consists of 128 accelerating structures, 64 rf pulse compressors, 64 klystrons, waveguide components, etc. Mass-production of these high power rf components has been almost completed. Production quality is confirmed by the high power rf test. Installation of the C-band components started in August 2009. So far, about half of the components have been installed on schedule. The accelerating structures are aligned with about 0.1 mm accuracy. By the date of the IPAC'10 conference, we will almost complete the installation. In this presentation, we will report the construction status.

 
THPEA010 High Power RF Test on the Mass-produced C-band RF Components for XFEL/SPring-8. 3694
 
  • T. Sakurai, T. Inagaki, C. Kondo, T. Shintake, K. Shirasawa
    RIKEN/SPring-8, Hyogo
  • S. Suzuki
    JASRI/SPring-8, Hyogo-ken
 
 

We report the high power rf test results of C-band accelerator system for X-ray free electron laser (XFEL) in SPring-8 site. In XFEL main accelerator, 64 C-band systems will be used in total, whose components are under mass production at several industries in Japan. We performed high power RF test with three sets of the mass-produced components in XFEL test bunker. We operate the C-band components with the accelerating gradient, as high as 40 MV/m. We measured the high voltage breakdown rate and the dark current emission.

 
THPEA011 Simulation of Magnetic Alloy Loaded RF Cavity and HOM Analysis 3697
 
  • K. Hasegawa, K. Hara, C. Ohmori, M. Tada, M. Yoshii
    KEK, Ibaraki
  • M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura
 
 

The RF cavity using Magnetic Alloy (MA) cores has been developed for achieving the high field gradient in J-PARC. For reducing the beam loading effects, the Q-value of the RF cavities in the Main Ring (MR) is controlled by using the cut-core configuration. In order to check the effect of HOMs between the cut-core gap, a simulation method of MA cores was studied and electromagnetic fields of excitation modes have been calculated by HFSS. We present the detail of the simulation method of MA cores and the HOM analysis of the cavity with the cut-cores.

 
THPEA012 Various Observables of TW Accelerator Structures Operating 100MV/m or Higher at X-band Facility, Nextef of KEK 3699
 
  • T. Higo, T. Abe, M. Akemoto, S. Fukuda, N. Higashi, Y. Higashi, N.K. Kudo, S. Matsumoto, T. Shidara, T. Takatomi, K. Ueno, Y. Watanabe, K. Yokoyama, M. Yoshida
    KEK, Ibaraki
 
 

Under the CERN-SLAC-KEK collaboration, we have been developing the high gradient TW accelerator structures. One of the main focuses is the feasibility study of CLIC accelerator structure at X-band. A high power facility, Nextef*, was established at KEK in 2007. A few structures have been tested, including an un-damped disk-loaded structure successfully tested beyond 100 MV/m, a heavily damped structure to be tested from late 2009 and a structure made in a quadrant configuration. These structures follow the same accelerating-mode RF parameter profile, called CLIC-C**, but show different features at high gradient operation. Various observables, such as dark current, vacuum activities, light emission, breakdown rate, and so on, are measured. We discuss the high gradient phenomena related to these observables and the possible improvement for stable operation at a higher gradient.


* T. Higo et al., THP038, LINAC06,2006.
**A. Grudiev, http://indico.cern.ch/conferenceDisplay.py?confId=30911

 
THPEA014 TE11/TM11 Mixed-mode Waveguide Valve at X-band 3705
 
  • S. Kazakov, T. Higo, S. Matsumoto
    KEK, Ibaraki
 
 

A waveguide vacuum valve for WR90 waveguide was designed, fabricated and tested. The valve consists of a modified commercial gate valve sandwitched with smooth tapers. The TE10 traveling wave in WR90 waveguide is "transmoded" into TE11+TM11 mode in the taper, going through the gate valve and is tapered back to the normal mode in WR90. The test has been successfully done. The valve stably trasmitted 40MW peak power with 500ns pulse width and this is limited by available RF power source.

 
THPEA016 Developments of Magnetic Alloy Cores with Higher Impedance for J-PARC Upgrade 3711
 
  • C. Ohmori, K. Hasegawa, A. Takagi
    KEK, Ibaraki
  • K. Hara, T. Shimada, H. Suzuki, M. Tada, M. Yoshii
    KEK/JAEA, Ibaraki-Ken
  • M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
 
 

Magnetic alloy cavities are successfully used for J-PARC synchrotrons. These cavities generate much higher RF voltage than ordinary ferrite cavities. For future upgrades of J-PARC facilities, a higher field gradient is necessary. It was found that the characteristics of magnetic alloy is improved by a new annealing scheme under magnetic field. A large production system using an old cyclotron magnet is under construction for the J-PARC upgrade. The status of core development will be reported.

 
THPEA019 Thermal Deformation of Magnetic Alloy Cores for J-PARC RCS RF Cavities 3717
 
  • T. Shimada
    KEK/JAEA, Ibaraki-Ken
  • K. Hara, K. Hasegawa, C. Ohmori, M. Tada, M. Yoshii
    KEK, Ibaraki
  • M. Nomura, A. Schnase, H. Suzuki, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura
 
 

Several magnetic alloy cores of the RF cavities, which are installed in the 3 GeV rapid cycling synchrotron (RCS) of J-PARC have shown buckling after about two years operation. To find the reason, why the local deformation happened, we made a test setup. There we heat up MA cores in air by 500 kHz RF and measure the thermal deformation in order to collect information about the buckling process. The results obtained by comparing the expansion of cores made by different production methods are reported.

 
THPEA020 Design of an RF Input coupler for the IFMIF/EVEDA RFQ Linac 3720
 
  • S. Maebara
    JAEA, Ibaraki-ken
 
 

In the design of prototype RFQ linac for the IFMIF/EVEDA Project, a coupled cavity type of RFQ, which has a longitudinal length of 9.78m, was proposed to accelerate deuteron beam up to 5MeV. The operation frequency of 175MHz was selected to accelerate a large current of 125mA in CW mode. The driving RF power of 1.28 MW by 8 RF input couplers has to be injected to the RFQ cavity. As the RF input coupler design, RF losses including RF vacuum windows, based on a 4 1/16 inch and 6 1/8 inch co-axial waveguide as well as RF coupling factor of a loop antenna with varied insertion depths using an RFQ model were calculated. In this conference, these results and thermal analysis results in CW operation mode will be presented in details.

 
THPEA022 Condition of MA Cores in the RF Cavities of J-PARC Synchrotrons after Several Years of Operation 3723
 
  • M. Nomura, A. Schnase, T. Shimada, H. Suzuki, F. Tamura, M. Yamamoto
    JAEA/J-PARC, Tokai-mura
  • E. Ezura, K. Hara, C. Ohmori, M. Tada, M. Yoshii
    KEK/JAEA, Ibaraki-Ken
  • K. Hasegawa, K. Takata
    KEK, Ibaraki
 
 

We have been operating the RF cavities loaded with MA cores with a high field gradient of more than 20 kV/m since October 2007. We have been measuring the RF cavity impedance at the shutdown periods, and we detected the impedance reductions of RCS RF cavities on January and June 2009. Taking out the RF cavities from the beam line and opening them, we found that many of cores showed a buckling at the inner radius. Also detachment of the epoxy coating intended to prevent rusting was observed. We report the detail of condition of MA cores and the relation between the impedance reduction and core condition.

 
THPEA023 Drift Tube Linac Cavities with Space-saving Amplifier Coupling of New Injector for RIKEN RI-Beam Factory 3726
 
  • K. Suda, S. Arai, Y. Chiba, O. Kamigaito, M. Kase, N. Sakamoto, K. Yamada
    RIKEN Nishina Center, Wako
 
 

A new injector RILAC2 for RIKEN RI-Beam Factory is under construction. The three Drift Tube Linac (DTL) cavities, located downstream of an RFQ linac, are designed to operate at a fixed RF frequency of 36.5 MHz, and to accelerate very heavy ions such as 136Xe20+ and 238U35+ from 100 keV/u to 680 keV/u for the injection to the RIKEN Ring Cyclotron. The first two cavities (DTL1 and 2) are newly constructed, and an existing cavity is modified for the last one (DTL3). The structure is based on the quarter-wavelength resonator. The inner diameter ranges from 0.8 to 1.3 m. In order to save the construction cost and space for the equipments, direct coupling scheme has been adopted for the RF amplifier. A capacitive coupler was designed to match the input impedance to 700, which corresponds to the optimum output impedance of a tetrode. Design of the cavities and couplers will be described in detail.

 
THPEA024 Duct-Shaped SiC Dummy Load of L-band Power Distribution System for XFEL/SPring-8 3729
 
  • J. Watanabe, S. Kimura, K. Sato
    Toshiba, Yokohama
  • T. Asaka, H. Ego, H. Hanaki
    JASRI/SPring-8, Hyogo-ken
 
 

TOSHIBA is manufacturing the L-band acceleration system for the SPring-8 Joint Project for XFEL. We have developed a new type duct-shaped SiC dummy load for its power distribution system. The load terminates a WR650 waveguide and can absorb the maximum mean power of 10kW. In order to reduce VSWR less than 1.1 in the frequency range of 1.428GHz, we shaped the SiC absorber into a 35cm long tapered cylinder and mounted matching stubs in the waveguide near the inlet of the load. The SiC absorber was fit into a cylindrical copper with efficient water-cooling channels. The design and manufacture and the low-power tests of our original dummy load are described in this paper.

 
THPEA025 HOM Characteristics Measurement of Mini-LIA Cavity 3732
 
  • C. Cheng, J.S. Duo, J. Lv, S.X. Zheng
    TUB, Beijing
  • J. Li
    CAEP/IFP, Mainyang, Sichuan
 
 

Mini-LIA was a miniature linear induction accelerator designed and manufactured by China Academy of Engineering Physics and Tsinghua University. To investigate the higher order mode (HOM) of Mini-LIA cavity, especially the frequency and quality factor Q of the TM110 and TM120 in it, both numerical simulation and experiments were performed. Several models of the cavity were established and calculated by using E module of MAFIA code. Network analyzer was applied to measure the frequency and Q in cavity. Both the simulation results and the experiment results are presented in this paper. The results of the experiments were coincident with the calculated results. Finally, The HOM characteristic of Mini-LIA cavity with metglass core in it was explored, and some interesting results was obtained.

 
THPEA026 Investigation of the Genetic Algorithm in the Diagnosis of the Coupled Cavity Chain 3735
 
  • Q.Z. Xing, T.T. Liang, J. Lv, D.C. Tong
    TUB, Beijing
 
 

The application of the genetic algorithm in the diagnosis of the coupled cavity chain is investigated in this paper. One program named GANL2 has already been developed based on the genetic algorithm at Tsinghua University. The cell frequencies, quality factors, and coupling between the cells can be estimated by GANL2 if the pass-band reflection curve is known. This method has been applied in the diagnosis of the S-band and X-band standing-wave linac cavities. In this paper we present the preliminary investigation of the genetic algorithm in the diagnosis of the L-band 9-cell superconducting copper cavity model. The result of the calculation and measurement are compared. Not all the cells are diagnosed well. More precise measurement is needed for further study.

 
THPEA027 Study on Frequency Change by 3D Reconstruction of Deformed Cavities of LINAC Collinear Load 3738
 
  • Z. Shu, L.G. Shen, Y. Sun, X.C. Wang
    USTC/PMPI, Hefei, Anhui
  • Y.J. Pei
    USTC/NSRL, Hefei, Anhui
 
 

Collinear load, consisted of several coaxial cavities, is a substitute for traditional waveguide-type load to absorb the remnant power of the LINAC and makes the accelerating structure compact and small-size. The power loss on the cavities of collinear load brings thermal deformation which affects their resonant frequency deeply. In this paper, a new approach of 3D reconstruction of the thermal deformed cavities is utilized to evaluate the accurate influence on frequency change caused by non-uniform deformation and water cooling strategies of collinear absorbing load are studied. Then the thermal behavior of a six-cavity collinear load, which is coated with Kanthal alloy and FeSiAl alloy and used on a 2856MHz, 2π/3 mode respectively, is researched. The results show that the collinear load with Kanthal alloy can only absorb up to 10kW, while with FeSiAl alloy it can dissipate 15kW when the water flow controlled within 3.0kg/s for energy saving.


* Tian Z. etc., "Finite Element Analysis of RF Cavity", Parietti L. etc., "Thermal/Structural Analysis and Frequency Shift", Anthony, etc. "A NURBS-based Technique for Subject-specific Construction".

 
THPEA028 Prelimimary Study of the Higher-harmonic Cavity for the Upgrade Project of Hefei Light Source 3741
 
  • C.-F. Wu, H. Fan, W. Fan, G. Feng, W.W. Gao, K. Jin, W. Li, G. Liu, L. Wang, S.C. Zhang, Y. Zhao
    USTC/NSRL, Hefei, Anhui
  • R.A. Bosch
    UW-Madison/SRC, Madison, Wisconsin
 
 

A radio frequency system with a higher-harmonic cavity will be used to increase the beam lifetime and suppress coupled-bunch instabilities of the upgrade Hefei Light Source. In the paper, the simulated results confirm that tuning in the harmonic cavity may suppresses the parasitic coupled-bunch instabilities. The higher-harmonic cavity has been designed and the calculated optimum lifetime increase ratio is 2.58.

 
THPEA030 Design and Analysis of RF Cavities for the Cyclotron CYCHU-10 3744
 
  • T. Hu, X. Hu, J. Huang, D. Li, P. Tan, J. Yang, T. Yu
    HUST, Wuhan
 
 

The design study of a 10MeV compact cyclotron CYCHU-10 has been developed at Huazhong University of Science and Technology (HUST). We developed the basic shapes and dimensions and carried out the simulations for the CYCHU-10 cavities with 3D numerical calculation softwares in this paper. The distributions of electromagnetic field are illustrated by means of the electromagnetic and structural analysis, and the wooden model test is preformed as well. In addition, this paper gives mechanical tolerance effects which deformed due to the limit of mechanical working of cavities under practical conditions. This work helps to evaluate the performances of capacitive frequency trimmer design.

 
THPEA031 Development of a 13.56MHz RF Implanter at PEFP 3747
 
  • T.A. Trinh, Y.-S. Cho, I.-S. Hong, J.-H. Jang, H.S. Kim, H.-J. Kwon, H.R. Lee, B.-S. Park
    KAERI, Daejon
 
 

In the RF linac, the RF system is roughly half of the total cost. The 13.56MHz rf generator is cheap and readily available. Therefore, an rf implanter which uses a cavity operating at the frequency of 13.56MHz has now been considered and developed at Proton Engineering Frontier Project (PEFP) - Korea. The implanter consists of a Duoplasmatron ion source, a triplet focusing magnet, an rf cavity, a bending magnet and an end chamber. It can accelerate particles up to 32keV/u for charge to mass ratio of 1/4. The implanter design concept, fabrication, testing and commissioning are presented in this presentation.

 
THPEA032 Commissioning of L-band Intense Electron Accelerator for Irradiation Applications 3750
 
  • S.H. Kim, M.-H. Cho, S.D. Jang, W. Namkung, S.J. Park, H.R. Yang
    POSTECH, Pohang, Kyungbuk
  • K.H. Chung, K.O.LEE. Lee
    KAPRA, Cheorwon
  • J.-S. Oh
    NFRI, Daejon
 
 

An intense L-band electron linac is now being commissioned at ACEP (Advanced Center for Electron-beam Processing in Cheorwon, Korea) for irradiation applications in collaboration with POSTECH (Pohang University of Science and Technology) and KAPRA (Korea Accelerator and Plasma Research Association). It is capable of producing 10-MeV electron beams with average 30-kW. For a high-power capability, we adopted the L-band traveling-wave structure operated with a 2π/3 mode. The RF power is supplied by the pulsed 25-MW and average 60-kW klystron with the matched pulse modulator and the inverter power supplies. The accelerating gradient is 4.2 MV/m with the beam current of 1.45 A which is fully beam-loaded condition. The solenoidal magnetic field is 700 Gauss to focus the electron beam and suppress the BBU instability. In this paper, we present commissioning status with details of the accelerator system.

 
THPEA033 Commissioning of C-band Standing-wave Accelerator 3753
 
  • H.R. Yang, M.-H. Cho, S.D. Jang, S.H. Kim, W. Namkung, S.J. Park
    POSTECH, Pohang, Kyungbuk
  • K.H. Chung, K.O.LEE. Lee
    KAPRA, Cheorwon
  • J.-S. Oh
    NFRI, Daejon
 
 

A C-band standing-wave electron accelerator for a compact X-ray source is being commissioned at ACEP (Advanced Center for Electron-beam Processing in Cheorwon, Korea). It is capable of producing 4-MeV electron beam with pulsed 50-mA. The RF power is supplied by the 5-GHz magnetron with pulsed 1.5 MW and average 1.2 kW. The accelerating column is a bi-periodic and on-axis-coupled structure operated with π/2-mode standing-waves. It consists of 3 bunching cells, 6 normal cells and a coupling cell. As a result of cold tests, the resonant frequency of the accelerating column is 4999.17 MHz at the π/2-mode and the coupling coefficient is 0.92. The field flatness was tuned to be less than 2%. In this paper, we present commissioning status with design details of the accelerator system.

 
THPEA035 Multi-cell RF Deflecting System for Formation of Hollow High Energy Heavy Ion Beam 3756
 
  • A. Sitnikov, N.N. Alexeev, A. Golubev, V.A. Koshelev, T. Kulevoy, S. Minaev, B.Y. Sharkov
    ITEP, Moscow
  • D.H.H. Hoffmann, N.A. Tahir, D. Varentsov
    GSI, Darmstadt
 
 

Terra Watt Accumulator project (ITEP-TWAC) is aiming the accumulation of an ion beam accelerated up to 0.7 GeV/u in a storage ring providing intensity of heavy ions up to 10 power 12 particles per pulse for experiments on heavy ion beam-plasma interaction. For advanced experiments on high energy density physics the hollow cylindrical target is needed. A new method for RF rotation of the ion beam is applied for reliable formation of the hollow cylindrical beam. A principle of fast beam rotation by using a system of the multi-cell RF deflectors is considered in this paper. A four-cell H-mode deflecting cavity operating at the frequency of 298 MHz has been developed; similar 1.5 m long cavities being applied for both x- and y- directions. The shape of the deflecting electrodes has been optimized in order to provide the uniform deflection over the whole aperture taking into account both electric and magnetic components of the RF field. A deflecting system and a focusing quadrupole triplet applied to the beam with the energy of 450 MeV/u and normalized transverse emittance of 10*pi mrad*mm may form the quasi-hollow configuration with the inner radius up to 1.5 mm and thickness of 1 mm.

 
THPEA036 Stabilization of the Polarization Plane in Traveling Wave Deflectors 3759
 
  • N.P. Sobenin, A. Anisimov, I.I.V. Isaev, S.V. Kutsaev, M.V. Lalayan, A.Yu. Smirnov
    MEPhI, Moscow
  • A.A. Zavadtsev, D.A. Zavadtsev
    Nano, Moscow
 
 

New possibilities of the polarization plane stabilization in the traveling hybrid TM11 wave deflectors are considered in this paper. These possibilities are realized in two new structures: DLW with two peripheral recesses in cells and DLW with oval aperture. In terms of electro-dynamic parameters, thermal regimes and manufacturing technology these structures as well as a classical structure with two stabilizing holes show some advantages and some disadvantages. The advantages of the new structures are good RF mode separation and effective cooling. The specifics of such structures tuning are also described.

 
THPEA039 Constructions of DC Potential Input into Resonator of Linear Accelerators 3762
 
  • P.R. Safikanov, S.M. Polozov
    MEPhI, Moscow
 
 

Nowadays the DC potential using was proposed for ion beam focusing in linear accelerators. It was proposed to use the DC potential for combined beam focusing (electrostatic focusing and focusing by using of higher RF field spatial harmonics) in bunching section of linac *. These accelerators use an IH-type resonator. So-called linear undulator accelerator (UNDULAC) was proposed for ribbon ion beam bunching and acceleration **. One of possible scheme of UNDULAC can be realized using an electrostatic undulator in E-type resonator. In this report the different types of the electrostatic potential inputting into resonator will discussed.


* P.А. Demchenko at al., Problems of Atomic Science and Technology, 2008, 5 (50), pp. 28-32.
** E.S. Masunov at al., Radiation Physics and Chemistry, 2001, v. 61, рр. 491-493.

 
THPEA040 Characteristics of the Parallel Coupled Accelerating Structure 3765
 
  • A.E. Levichev, V.M. Pavlov
    BINP SB RAS, Novosibirsk
  • Y.D. Chernousov
    ICKC, Novosibirsk
  • V. Ivannikov, I.V. Shebolaev
    ICKC SB RAS, Novosibirsk
 
 

The prototype of parallel coupled accelerating structure is developed. It consists of five accelerating cavities, common excitation cavity and RF power waveguide feeder. The excitation cavity is a segment of rectangular waveguide loaded by resonance copper pins. The excitation cavity operate mode is T 105. Connection between excitation cavity and accelerating cavities is performed by magnetic field. The theoretical model of the parallel coupled accelerating structure is developed. According to model the tuning and matching of the structure are performed. The electrodynamics characteristics are measured. In storage energy regime the accelerated electron beam is obtained.

 
THPEA041 Manufacturing and Testing of a TBL PETS Prototype 3768
 
  • F. Toral, P. Abramian, J. Calero, D. Carrillo, F.M. De Aragon, L. García-Tabarés, J.L. Gutiérrez, A. Lara, E. Rodríguez García, L. Sanchez
    CIEMAT, Madrid
  • S. Döbert, I. Syratchev
    CERN, Geneva
 
 

The goal of the present CLIC test facility (CTF3) is to demonstrate the technical feasibility of the CLIC scheme. The Test Beam Line (TBL) is used to study a CLIC decelerator focusing on 12 GHz power production and the stability of the decelerated beam. The extracted CTF3 drive beam from the combiner ring (CR) features a maximum intensity of 28 A and 140 ns pulse duration, where the Test Beam Line consists of 16 cells, each one including a BPM, a quadrupole on top of a micrometer-accuracy mover and a RF power extractor so-called PETS (Power Extraction and Transfer Structure). This paper describes the first prototype fabrication techniques, with particular attention to the production of the long copper rods which induce the RF generation. A special test bench for the characterization of the device with low RF power measurements has been developed. Performed mesurements of the scattering parameters and the electric field profile along the structure are carefully described. Finally, the prototype has been installed at CLEX, and first measurements with beam are also reported.

 
THPEA042 Engineering Design of a Multipurpose X-band Accelerating Structure 3771
 
  • D. Gudkov, G. Riddone, A. Samoshkin, R. Zennaro
    CERN, Geneva
  • M.M. Dehler, J.-Y. Raguin
    PSI, Villigen
 
 

PSI-XFEL and Elettra-Fermi-require a X-band RF structure. As CLIC is pursuing a program for producing and testing x-band high-gradient RF structures, a collaboration between PSI, Elettra and CERN, has been established to build a multipurpose X-band accelerating structure. This paper focuses on its engineering design which is based on disk-shaped cells bonded together by different technologies (diffusion bonding, vacuum brazing and laser beam welding). The accelerating structure consists of 2 coupler subassemblies and 73 disks, and include wake field monitor waveguides. The engineering study also comprises the external cooling system, consisting of two parallel cooling circuits, and the tuning system, allowing for the fine-tuning by means of cell deformations. The engineering solution for installation and sealing of wake field monitor feed-through devices inside the accelerating structure RF-cavity is also proposed.

 
THPEA043 RF Pulse Compression Stabilization at the CTF3 CLIC Test Facility 3774
 
  • A. Dubrovskiy, F. Tecker
    CERN, Geneva
 
 

In the CTF3 accelerator, the RF produced by each of ten 3 GHz klystrons goes through waveguides, RF pulse compressors and splitters. The RF phase and power transformation of these devices depend on their temperature. The quantitative effect of the room temperature variation on the RF was measured. It is the major source of undesired changes during the CTF3 operation. An RF phase-loop and a compressor temperature stabilization are developed to suppress the phase fluctuation and the power profile change due to the temperature variation. The implementation is transparent for operators it does not limit anyhow the flexibility of RF manipulations. Expected and measured suppression characteristics will be given. As well RF measurement dependence on the temperature will be mentioned.

 
THPEA045 Development of a Dielectric-loaded Accelerating Structure with Built-in Tunable Absorption Mechanism for High Order Modes 3777
 
  • S.P. Antipov, W. Gai, O. Poluektov
    ANL, Argonne
  • C.-J. Jing, A. Kanareykin, P. Schoessow
    Euclid TechLabs, LLC, Solon, Ohio
 
 

As the dimensions of accelerating structures become smaller and beam intensities higher, the transverse wakefields driven by the beam become quite large with even a slight misalignment of the beam. These deflection modes can cause inter-bunch beam breakup and intra-bunch head-tail instabilities along the beam path. We propose a built-in tunable absorption mechanism for damping the parasitic transverse modes without affecting the operational modes in dielectric loaded accelerating (DLA) structures and wakefield power extractors. The new principle for HOM absorption is based on electron paramagnetic resonance. The dielectric tube of the DLA has to be doped with a material exhibiting high EPR, for example ruby, Al2O3 overdoped ~1% with Cr3+. The absorption frequency can be tuned by an external DC magnetic field to match the frequency of the transverse mode. At the resonance imaginary part of permeability becomes significant and the dielectric tube acts as an absorber for the transverse modes. The external DC magnetic field is solenoidal and has to have a magnitude of about 3 kG. This configuration in fact is desirable to focus the beam and provide additional control of beam break up.

 
THPEA046 The MuCool Test Area and RF Program 3780
 
  • A.D. Bross, M. Chung, A. Jansson, A. Moretti, K. Yonehara
    Fermilab, Batavia
  • D. Huang, Y. Torun
    IIT, Chicago, Illinois
  • D. Li
    LBNL, Berkeley, California
  • J. Norem
    ANL, Argonne
  • R. B. Palmer, D. Stratakis
    BNL, Upton, Long Island, New York
  • R.A. Rimmer
    JLAB, Newport News, Virginia
 
 

TThe MuCool RF Program focuses on the study of normal conducting RF structures operating in high magnetic field for applications in muon ionization cooling for Neutrino Factories and Muon Colliders. This paper will give an overview of the program, which will include a description of the test facility and its capabilities, the current test program, and the status of a cavity that can be rotated in the magnetic field which allows for a more detailed study of the maximum stable operating gradient vs. magnetic field strength and angle.

 
THPEA047 Dielectric Loaded RF Cavities for Muon Facilities 3783
 
  • M. Popovic, A. Moretti
    Fermilab, Batavia
  • C.M. Ankenbrandt, M.A.C. Cummings, R.P. Johnson, M.L. Neubauer
    Muons, Inc, Batavia
 
 

Alternative RF cavity fabrication techniques for accelerator applications at low frequencies are needed to improve manufacturability, reliability and cost. RF cavities below 800 MHz are large, take a lot of transverse space, increase the cost of installation, are difficult to manufacture, require significant lead times, and are expensive. Novel RF cavities partially loaded with a ceramic for accelerator applications will allow smaller diameter cavities to be designed and built. The manufacturing techniques for partially loaded cavities will be explored. A new 200MHz cavity will be built for the Fermilab Proton Source to improve the longitudinal emittance and energy stability of the linac beam at injection to the Booster. A cavity designed for 400 MHz with a ceramic cylinder will be tested at low power at cryogenic temperatures to test the change in Qo due to the alumina ceramic. Techniques will be explored to determine if it is feasible to change the cavity frequency by replacing an annular ceramic insert without adversely effecting high power cavity performance.

 
THPEA049 Normal Conducting RF Cavity for MICE 3786
 
  • D. Li, A.J. DeMello, S.P. Virostek, M.S. Zisman
    LBNL, Berkeley, California
 
 

Normal conducting RF cavities must be used for the cooling section of international Muon Ionization Cooling Experiment (MICE) which is currently under construction at Rutherford Appleton Laboratory (RAL) in UK. Eight 201-MHz cavities are needed for the MICE cooling section; fabrication of the first five cavities is nearly complete. This paper reports the cavity fabrication status that includes the cavity design, fabrication techniques and preliminary low power RF measurements of the first five cavities.

 
THPEA051 A Method for Establishing Q-factors of RF Cavities 3789
 
  • X.D. Ding, S. Boucher
    RadiaBeam, Berkeley, California
 
 

The distribution of electromagnetic fields in an RF cavity is primarily determined by the geometry of the RF cavity. The quality factor (Q-factor) of an RF cavity characterizes RF losses in the cavity: an RF cavity having a higher Q-factor is a more efficient user of RF power. However, a cavity having a lower Q-factor can operate on a wider range of frequencies, shorter filling time and may be more stable and less sensitive to input power perturbations. A method is discussed in this paper for an RF cavity that provided a desired Q-factor for the cavity while enabling a desired field distribution for electron acceleration within the cavity. The structure forming the inner wall of the RF cavity may be comprised of different types of material(such as copper and steel). Using different materials for different portions of the inner walls forming a cavity will cause different Q-factors for the cavity while the shape of the cavity remains constant.


contact: ding@radiabeam.com

 
THPEA052 Design of a Fast Extraction Kicker for the ALPHA Project 3792
 
  • T.H. Luo, S.-Y. Lee
    IUCF, Bloomington, Indiana
 
 

In this report, we present our design of a fast extraction kicker for ALPHA. Due to the fast rise time and high voltage requirement, we choose the traveling wave kicker. Both 2D Posisson and 3D Microwave Studio simulation are carried out. Uniformity of electric field, energy transmission through the stripline structure and time response of the kicker are studied carefully. A prototype kicker will be built and tested soon.

 
THPEA054 Rectangular Box Cavity Tests in Magnetic Field for Muon Cooling 3795
 
  • Y. Torun, D. Huang
    IIT, Chicago, Illinois
  • A.D. Bross, M. Chung, A. Jansson, A. Kurup, J.R. Misek, A. Moretti
    Fermilab, Batavia
  • J. Norem
    ANL, Argonne
 
 

Muon cooling requires high-gradient normal conducting cavities operating in multi-Tesla magnetic fields for muon beam focusing in an ionization cooling channel. Recent experience with an 805-MHz pillbox cavity at the Fermilab MuCool Test Area has shown significant drop in accelerating field performance for the case of parallel electric and magnetic fields. It has been suggested that having the magnetic field perpendicular to the electric field should provide magnetic insulation and suppress breakdown. An 805-MHz Cu rectangular box cavity was built for testing with the fields perpendicular. It was mounted on an adjustable support to vary the angle between the rf electric and external magnetic field. We report on design and operation of the rectangular box cavity.

 
THPEA055 500 MW X-band RF System of a 0.25 GeV Electron LINAC for Advanced Compton Scattering Source Application 3798
 
  • T.S. Chu, S.G. Anderson, C.P.J. Barty, D.J. Gibson, F.V. Hartemann, R.A. Marsh, C. Siders
    LLNL, Livermore, California
  • C. Adolphsen, E.N. Jongewaard, T.O. Raubenheimer, S.G. Tantawi, A.E. Vlieks, J.W. Wang
    SLAC, Menlo Park, California
 
 

A Mono-Energetic Gamma-Ray Compton scattering light source is being developed at LLNL. The electron beam for the interaction will be generated by a X-band RF gun and LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons to energy of 250 MeV or greater. Two high power klystrons, each capable of generating 50 MW, 1.5 msec pulses, will be the main RF sources for the system. These klystrons will be powered by state of the art solid-state high voltage modulators. A RF pulse compressor, similar to the SLED II pulse compressor, will compress the klystron output pulse with a power gain factor of five. For compactness consideration, we are looking at a folded RF line. The goal is to obtain 500 MW at output of the compressor. The compressed pulse will then be distributed to the RF gun and to six traveling wave accelerator sections. Phase shifter and amplitude control are located at the RF gun input and additional control points along the LINAC to allow for parameter control during operation. This high power RF system is being designed and constructed. In this paper, we will present the design, layout, and status of this RF system.

 
THPEA057 Development of a CW NCRF Photoinjector using Solid Freeform Fabrication (SFF) 3804
 
  • P. Frigola, R.B. Agustsson, L. Faillace
    RadiaBeam, Marina del Rey
  • W.A. Clemens, J. Henry, F. Marhauser, R.A. Rimmer, A.T. Wu, X. Zhao
    JLAB, Newport News, Virginia
  • O. Harrysson, T. Horn, K. Knowlson, T. Mahale, G. Prasanna
    NCSU, Raleigh, North Carolina
  • F. Medina, R.B. Wicker
    University of Texas El Paso, W.M. Keck Center for 3D Innovation, El Paso, Texas
  • L.E. Murr
    University of Texas at El Paso, El Paso, Texas
 
 

A key issue for high average power, normal conducting radio frequency (NCRF), photoinjectors is efficient structure cooling. To that end, RadiaBeam has been developing the use of Solid Freeform Fabrication (SFF) for the production of NCRF photoinjectors. In this paper we describe the preliminary design of a high gradient, very high duty cycle, photoinjector combining the cooling efficiency only possible through the use of SFF, and the RF efficiency of a re-entrant gun design. Simulations of the RF and thermal-stress performance will be presented, as well as material testing of SFF components.

 
THPEA059 Ultra-high Gradient Compact S-band Linac for Laboratory and Industrial Applications 3807
 
  • L. Faillace, R.B. Agustsson, P. Frigola, A.Y. Murokh
    RadiaBeam, Marina del Rey
  • V.A. Dolgashev
    SLAC, Menlo Park, California
  • J.B. Rosenzweig
    UCLA, Los Angeles, California
 
 

There is growing demand from the industrial and research communities for high gradient, compact RF accelerating structures. The commonly used S-band SLAC-type structure has an operating gradient of only about 20 MV/m; while much higher operating gradients (up to 70 MV/m) have been recently achieved in X-band, as a consequence of the substantial efforts by the Next Linear Collider (NLC) collaboration to push the performance envelope of RF structures towards higher accelerating gradients. Currently however, high power X-band RF sources are not readily available for industrial applications. Therefore, RadiaBeam Technologies is developing a short, standing wave S-band structure which uses frequency scaled NLC design concepts to achieve up to a 50 MV/m operating gradient at 2856 MHz. The design and prototype commissioning plans are presented.

 
THPEA060 Status of High Power Tests of Normal Conducting Single-Cell Standing Wave Structures 3810
 
  • V.A. Dolgashev, S.G. Tantawi, A.D. Yeremian
    SLAC, Menlo Park, California
  • Y. Higashi
    KEK, Ibaraki
  • B. Spataro
    INFN/LNF, Frascati (Roma)
 
 

We report results of ongoing high power tests of single cell standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the accelerating gradient capability of normal-conducting rf powered particle accelerators. The test setup consists of reusable mode-launchers and short test structures powered by SLAC's XL-4 klystron. We have tested structures of different geometries, cell joining techniques, and materials, including hard copper alloys and molybdenum. We found that the behavior of the breakdown rate is reproducible for different structures of the same geometry and material. The breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for structures of different geometries.

 
THPEA061 A Dual-moded Cavity for RF Breakdown Studies 3813
 
  • C.D. Nantista, C. Adolphsen, F. Wang
    SLAC, Menlo Park, California
 
 

The phenomenon of rf breakdown presents a technological limitation in the application of high-gradient particle acceleration in normal conducting rf structures. Attempts to understand the onset of this phenomenon and to study its limits with different materials, cell shapes, and pulse widths has been driven in recent years by linear collider development. One question of interest is the role magnetic field plays relative to electric field. A design is presented for a single, non-accelerating, rf cavity resonant in two modes, which, driven independently, allow the rf magnetic field to be increased on the region of highest electric field without affecting the latter. The design allows for the reuse of the cavity with different samples in the high-field region. Available high-power data will also be presented.

 
THPEA063 X-band RF Gun Development 3816
 
  • A.E. Vlieks, V.A. Dolgashev, S.G. Tantawi
    SLAC, Menlo Park, California
  • S.G. Anderson, F.V. Hartemann, R.A. Marsh
    LLNL, Livermore, California
 
 

In support of the T-REX program at LLNL and the High Gradient research program at SLAC, a new X-band multi-cell RF gun is being developed. This gun, similar to an earlier gun developed at SLAC for Compton X-ray source program, will be a standing wave structure made of 5.5 cells operating in the pi mode with copper cathode. This gun was designed following criteria used to build SLAC X-band high gradient accelerating structures. It is anticipated that this gun will operate with surface electric fields on the cathode of 200MeV/m with low breakdown rate. RF will be coupled into the structure through a symmetric final cell with a shape optimized to eliminable both dipole and quadruple field components. In addition, geometry changes to the original gun, operated with Compton X-ray source, will include a wider RF mode separation, reduced surface electric and magnetic fields.

 
THPEA064 Fabrication Technologies of the High Gradient Accelerator Structures at 100MV/m Range 3819
 
  • J.W. Wang, J.R. Lewandowski, J.W. Van Pelt, C. Yoneda
    SLAC, Menlo Park, California
  • B.A. Gudkov, G. Riddone
    CERN, Geneva
  • T. Higo, T. Takatomi
    KEK, Ibaraki
 
 

A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of < 5·10-7/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed.

 
THPEA065 RF Choke for Standing Wave Structures and Flanges 3822
 
  • A.D. Yeremian, V.A. Dolgashev, S.G. Tantawi
    SLAC, Menlo Park, California
 
 

SLAC participates in the U.S. High Gradient collaboration whose charter includes basic studies of rf breakdown properties in accelerating structures. These studies include experiments with different materials and construction methods for single cell standing wave accelerating structures. The most commonly used method of joining cells of such structures is the high temperature bonding and/or brazing in hydrogen and/or vacuum. These high temperature processes may not be suitable for some of the new materials that are under consideration. We propose to build structures from cells with an rf choke, taking the cell-to-cell junction out of the electromagnetic field region. These cells will be clamped together in a vacuum enclosure, the choke joint ensuring continuity of rf currents. Next, we propose a structure with a choke joint in a high gradient cell and a view port which may allow us microscopic, in-situ observation of the metal surface during high power tests. And third, we describe the design of a TM01 choke flange for these structures.

 
THPEC044 Design Methodology and Considerations for NOνA 53 MHz RF Cavities 4158
 
  • C.R. Ader, D. Wildman
    Fermilab, Batavia
 
 

The NOνA Experiment will construct a detector optimized for electron neutrino detection in the existing Neutrino at Main Injector (NuMI) beamline. This beamline is capable of operating at 400 kW of primary beam power and the upgrade will allow up to 700 kW. The cavities will operate at 53 MHz and three of them will be installed in the Recycler beamline. Thermal stability of the cavities is crucial since this affects the tuning. Results of finite element thermal and structural analysis involving the copper RF cavity will be presented.