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resonance

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WE2003 LLRF Systems for Modern Linacs: Design and Performance controls, feedback, linac, coupling 498
 
  • A. Brandt
    DESY, Hamburg
  Near-future linac projects put yet unreached requirements on the LLRF control hardware in both performance and manageability. Meeting their field stability targets requires a clear identification of all critical items along the LLRF control loop as well as knowledge of fundamental limitations. Large-scale systems demand for extended automation concepts. The experience gained with present systems as well as dedicated experiments deliver the basis for a design of future systems. Digital hardware has evolved quickly over the past years and FPGAs became common not only in LLRF control. A high degree of digitization in various fields, as for example beam diagnostics, suggests to aim for a convergence of the digital platform designs. Channeling of efforts of different research laboratories may be the key to an affordable solution that meets all requirements and has a broad range of applications.  
 
THP001 Conceptual LLRF Design for the European X-FEL controls, feedback, diagnostics, klystron 559
 
  • S. Simrock, V. Ayvazyan, A. Brandt, M. Huening, W. Koprek, F. Ludwig, K. Rehlich, E. Vogel, H. C. Weddig
    DESY, Hamburg
  • M. K. Grecki, T. Jezynski
    TUL-DMCS, Lodz
  • W. J. Jalmuzna
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  The LLRF System for the superconducting cavities of the European X-FEL must support an amplitude and phase stability of the accelerating fields of up to 0.01% and 0.01 deg. respectively. The stability must be achieved in pulsed operation with one klystron driving 32 cavities. This goal can only be achieved with low noise downconverters for field detection, high gain feedback loops and sophisticated feedforward techniques. State-of-the art technology including analog multipliers for downconversion, fast ADCs (>100 MHz) with high resolution (up to 16 bit), and high performance data processing with FPGAs with low latency (few hundred ns) allow to meets these goals. The large number of input channels ( >100 including probe, forward and reflected signal of each of the 32 cavities) and output channels (>34 including piezo tuners for each cavity) combined with the tremendous processing power requires a distributed architecture using Gigalink interfaces for low latency data exchange.  
 
THP011 High Gradient Operation with the CEBAF Upgrade RF Control System controls, feedback, linac, electron 589
 
  • C. Hovater, G. K. Davis, H. Dong, A. S. Hofler, K. King, J. Musson, T. E. Plawski
    Jefferson Lab, Newport News, Virginia
  The CEBAF Accelerator at Jefferson Lab is presently a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. It is planned to increase the energy to 12 GeV with the addition of 10 new high gradient cryomodules (17+ MV/m). The higher gradients pose significant challenges beyond what the present analog low level RF (LLRF) control systems can handle reliably; therefore, a new LLRF control system is needed. A prototype system has been developed incorporating a large FPGA and using digital down and up conversion to minimize the need for analog components. The new system is more flexible and less susceptible to drifts and component nonlinearities. Because resonance control is critical to reach high gradients quickly, the new cryomodules will include a piezoelectric tuner for each cavity, and the LLRF controls must incorporate both feedback and feed-forward methods to achieve optimal resonance control performance. This paper discusses development of the new RF system, system performance for phase and amplitude stability and resonance control under Lorentz detuning measured during recent tests on a prototype cryomodule.  
 
THP013 Adaptive Control of a SC Cavity Based on the Physical Parameters Identification controls, klystron, feedback, radio-frequency 595
 
  • T. Czarski, W. J. Jalmuzna, W. Koprek, K. T. Pozniak, R. S. Romaniuk
    Warsaw University of Technology, Institute of Electronic Systems, Warsaw
  • S. Simrock
    DESY, Hamburg
  The paper presents preliminary results of SRF cavity control by FPGA system called "SIMCON". Algebraic model of the control system including calibration and correction procedure of the signal path was discussed. In particular, there were debated the following aspects of the automatic control procedures: compensation of the input offset, calibration of the cavity channel and correction of the klystron channel (linearization). Functional structure of FPGA based SIMCON board for LLRF Cavity Control System was explained. Alghoritm of adaptive control for cavity driven with FPGA controller supported by MATLAB system was discussed. Experimental results for 8 cavities of ACC1 module controlled by the SIMCON board were shown. The resuls lead to novel method of parameters identification of cavity system in noisy and no stationary conditions.  
 
THP024 Development of Ultra-fast Silicon Switches and their Applications on Active X-Band, High-Power RF Compression Systems simulation, coupling, plasma, laser 619
 
  • J. Guo, S. G. Tantawi
    SLAC, Menlo Park, California
  In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer inserted into a cylindrical waveguide operating in the TE 01 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. A switch module is composed of the silicon switch, a circular waveguide T with the silicon switch at the center port and a movable short at the other end of silicon switch. The module can tune the S-matrix of on and off states to desired value. Our current design uses a CMOS compatible process and the fabrication is accomplished at SNF (Stanford Nanofabrication Facility). The switch has achieved <300ns on time with ~3% loss on the wafer. The RF energy is stored in a room-temperature, high-Q 400 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has a achieved a gain of 7, which is the ratio between output and input power. Power handling capability of the switch is estimated at the level of 10MW.  
 
THP028 Master Oscillator for Fermilab ILC Test Accelerator controls, simulation, power-supply, linear-collider 631
 
  • J. Branlard, B. Chase, E. Cullerton
    Fermilab, Batavia, Illinois
  The low phase-noise master oscillator generates and distributes the various frequencies required for the LLRF system controlling ILCTA cavities. Two chassis have been developed for this design, generating the programmable frequencies and performing the distribution and amplification, respectively. It has been successfully used with the SNS and the DESY-SIMCON LLRF systems, driving two different superconducting cavities. The design approach and a full characterization of the master oscillator are presented in this paper. The measurement results include the frequency stability and the phase and amplitude noise spectrums of the multiple frequency outputs.  
 
THP037 Wide-Range Frequency Compensation by Coaxial Ball-Screw Tuner acceleration, linear-collider, booster, monitoring 658
 
  • T. Higo, Y. Higashi, Y. Morozumi, K. Saito, K. Ueno, H. Yamaoka
    KEK, Ibaraki
  Low-loss 9-cell 1.3GHz cavities are studied at KEK aiming at a high-gradient operation for the International Linear Collider. One of the most important issues to realize such a high gradient in a pulsed operation of super-conducting cavities is the issue of how to compensate the Lorentz detuning. The Lorentz detuning of the cavity amounts to 3kHz at 45MV/m acceleration field. None of the tuners to date have achieved this range. A coaxial ball-screw tuner was designed and proved to reach this level in the room temperature operation. The performance at liquid Nitrogen temperature is also studied. From these results, we try to evaluate the feasibility of the operation at 2K.  
 
THP047 Prototyping of a Single-Cell Half-Reentrant Superconducting Cavity simulation, superconductivity, vacuum, coupling 685
 
  • M. S. Meidlinger, J. Bierwagen, S. Bricker, C. Compton, T. L. Grimm, W. Hartung, M. J. Johnson, J. Popielarski, L. Saxton, R. C. York
    NSCL, East Lansing, Michigan
  • E. Zaplatin
    FZJ, Jülich
  As superconducting niobium cavities achieve higher gradients, it is anticipated they will reach a performance limit as the peak surface magnetic field approaches the critical magnetic field. "Low loss" and "reentrant" cavity designs are being studied at CEBAF, Cornell, DESY, and KEK, with the goal of reaching higher gradients via lower surface magnetic field, at the expense of higher surface electric field. At present, cavities must undergo chemical etching and high-pressure water rinsing to achieve good performance. It is not clear whether this can be done effectively and reliably for multi-cell low loss or reentrant cavities using traditional techniques. A "half-reentrant" cavity shape has been developed with RF parameters similar to the low loss and reentrant cavities, but with the advantage that the surface preparation can be done easily with existing methods. Two prototype single-cell half-reentrant cavities are being fabricated at 1.3 GHz; the non-reentrant wall angle is 8 degrees, the beam tube radius is 29 mm, and the cell-to-cell coupling is 1.47%. The half-reentrant cavity design and the results and status of the prototyping effort will be presented.  
 
THP049 LANSCE DTL Longitudinal Field Measurements at High Power insertion, linac, proton, acceleration 691
 
  • G. O. Bolme, S. Archuletta, J. Davis, L. Lopez, J. T.M. Lyles, D. J. Vigil
    LANL, Los Alamos, New Mexico
  Shifts in proton beam tuning were observed in the DTL portion of the Los Alamos Neutron Science Center (LANSCE) Accelerator corresponding with cooling system obstructions during the 2003 operational cycle. A diagnostic system was developed to measure longitudinal field changes at the operational field levels to confirm the source of the tune shifts and track the effectiveness of cooling system repairs. This paper describes the diagnostic system and the results of field distribution measurements at high RF power in the accelerating structures.  
 
THP060 Capture Cavity II at Fermilab vacuum, klystron, instrumentation, cryogenics 719
 
  • T. W. Koeth
    Rutgers University, The State University of New Jersey, Piscataway, New Jersey
  • J. Branlard, R. H. Carcagno, B. Chase, P. Czarapata, H. Edwards, R. P. Fliller, C. M. Ginsburg, B. M. Hanna, A. Hocker, A. Klebaner, M. J. Kucera, M. McGee, D. F. Orris, P. S. Prieto, J. Reid, J. K. Santucci, W. M. Soyars, C.-Y. Tan
    Fermilab, Batavia, Illinois
  Capture Cavity II is a 9-cell high gradient TESLA Superconducting cavity intended to upgrade the existing Fermilab Photoinjector electron beam energy from 15MeV to 40Mev. DESY provided the cavity which performed to 33MV/m. Beam tube component preparation and installation onto the cavity was completed at DESY. The cavity was shipped to FNAL under vacuum. Installation and testing of this cavity has provided an opportunity to demonstrate Fermilab’s SCRF High Power Testing infrastructure. We report on the high power RF tests performed with Capture Cavity II at both 4.5K and 1.8K, Cryogenic System Performance, Piezo Electric based fast tuner, and low level RF control.  
 
THP061 High Field Test Results of Superconducting 3.9-GHz Accelerating Cavities at FNAL simulation, pick-up, linac, pulsed-power 722
 
  • N. Solyak, H. Edwards, M. Foley, I. G. Gonin, T. K. Khabiboulline, D. V. Mitchell, A. M. Rowe
    Fermilab, Batavia, Illinois
  The XFEL facilities are planning to use section with a few third harmonic cavities (3.9GHz) to improve beam performance [1]. Fermilab is developing superconducting third harmonic section for the FLASH(TTF/DESY) upgrade. This section will include four cavities equiped with couplers and blade tuners installed in cryostat. Up to now, two cavities are completed and one of them is under vertical test. The gradient of the cavity was limited by multipactor in HOM coupler. The visual inspection of the HOM couplers after cold tests showed that both couplers were damaged. In paper we discuss the results of vertical tests, multipactoring analysis in HOM coupler and a new design for HOM coupler.  
 
THP063 First High-Power ACS Module for J-PARC Linac linac, vacuum, pick-up, ion 725
 
  • H. Ao, K. Hasegawa, K. Hirano, T. Morishita, A. Ueno
    JAEA/LINAC, Ibaraki-ken
  • M. Ikegami
    KEK, Ibaraki
  • V. V. Paramonov
    RAS/INR, Moscow
  • Y. Yamazaki
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  J-PARC Linac will be commissioned with energy of 181-MeV using 50-keV ion source, 3-MeV RFQ, 50-MeV DTL and 181-MeV SDTL (Separated DTL) on December 2006. It is planed to be upgraded by using 400-MeV ACS (Annular Coupled Structure), in a few years from the commissioning. The first high-power ACS module, which will be used as the first buncher between the SDTL and the ACS has been fabricated, and a few accelerating modules are also under fabrication until FY2006. Detail of cavity design and tuning procedure has been studied with RF simulation analysis and cold-model measurements. This paper describes RF measurement results, fabrication status, and related development items.  
 
THP064 Tuning a CW 4-Rod RFQ rfq, acceleration, pick-up, vacuum 728
 
  • P. Fischer, A. Schempp
    IAP, Frankfurt-am-Main
  A 4-Rod RFQ has been built, which operates cw and will accelerate 5mA D beams up to 3 MeV. The length of the structure is 3.8 m, the power consumption as high as 250 kW. The tuning of a 4-Rod RFQ with 30 rf-cells at the frequency of 175 MHz is difficult, so procedures have been developed, to facilitate this work. The properties of the RFQ accelerator, the tuning procedure and the status of the project will be discussed.  
 
THP086 Mitigation of Power Loss Due to Skin Effect by Thin-Layered Film controls, vacuum, electromagnetic-fields 785
 
  • Y. Iwashita
    Kyoto ICR, Uji, Kyoto
  The AC current flows only on the metal surface, which is known as skin effect. The current concentration on the surface increases power loss. This results higher transmission loss of cable and degradation of Q in cavities. Skin effect on a metal film that is thinner than a skin depth is investigated starting from general derivation of skin depth on a bulk conductor. The reduction of the skin effect power loss with layered conductor films is reported and discussed.  
 
FR2003 New Materials and Designs for High-Power, Fast-Phase Shifters klystron, linac, impedance, rfq 829
 
  • R. L. Madrak, D. Sun, D. Wildman
    Fermilab, Batavia, Illinois
  • E. E. Cherbak, D. Horan
    ANL, Argonne, Illinois
  In the 100 MeV H- Linac to be constructed at Fermilab, the use of fast ferrite high power phase shifters will allow all accelerating RF cavities to be driven by a single 2.5 MW, 325 MHz klystron. This results in substantial cost savings. The tuners are coaxial with aluminum doped Yttrium Iron Garnet (YIG) ferrite. In combination with a branch line couplers, they will provide independent phase and amplitude control for each cavity. This is achieved by adjusting the solenoidal magnetic field applied to the ferrite. We report on our results in both low power (timing) and high power tests, for both 3'' and 1-5/8'' OD phase shifters. The low power measurements demonstrate that the rate of phase shift is well within the spec of 1 degree/us. The high power tests were performed at the Advanced Photon Source at Argonne National Lab. We measured phase shifts and the failure point (applied power) for tuners in various configurations. In addition, we performed phase and amplitude measurements for a setup consisting of a 1-5/8'' OD phase shifter along with a prototype branch line coupler.