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radio-frequency

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MOPD003 ILC Cavity Fabrication Optimization for High Production factory, vacuum, electron, linear-collider 451
 
  • A. J. Favale, M. Calderaro, E. Peterson, J. J. Sredniawski
    AES, Medford, NY
  In 2006, AES performed a US based industrial Cost Study of RF units in production quantities sufficient for the ILC. During this study detailed costs were estimated for the fabrication steps of the SRF cavities in high production quantities. In late 2007, AES carried out a more detailed study specifically oriented toward optimizing the high production methods of only the SRF cavities to arrive at a best estimate of cost. We have found that the revised estimate shows a 34% reduction in cavity fabrication cost. We have optimized many of the machining and welding steps to take advantage of automated operations were possible. Our high production cost estimates were based upon actual machining, welding and parts handling times derived during the prototype fabrication of ILC type cavities at AES. These values were then applied with learning as appropriate to more automated operations to reduce labor costs. In addition, the type and size of e-beam welding machines was optimized. We found that the use of all single chamber welders covering three specific sizes was most cost effective. Details of steps leading to the stated conclusions are presented herein.  
 
MOPD024 RF Power System for the IFMIF-EVEDA Prototype Accelerator power-supply, rfq, controls, linac 496
 
  • I. Kirpitchev, M-A. Falagán, A. Ibarra, P. Méndez, M. Weber
    CIEMAT, Madrid
  • M. Desmons, A. Mosnier
    CEA, Gif-sur-Yvette
  The IFMIF-EVEDA accelerator will be a 9 MeV, 125 mA cw deuteron accelerator prototype for verifying the validity of the accelerator design for IFMIF. The RFQ, matching section and DTL resonant cavities must be fed with continuous RF power at 175 MHz frequency with an accuracy of 1% in amplitude and ± 1° in phase. Currently two possible solutions for the DTL design are considered. The first option consists of normal conducting (NC) Alvarez type cavities and the second option consists of superconducting (SC) Half Wave Resonator cavities. Both options impose different demands on the RF system which are analyzed in this paper. The RF power system will be made of several amplification stages and will be based on vacuum tube amplifiers. The main characteristics of RF system including those of the high voltage power sources required to feed the anodes of the high power tubes will be presented in this paper.  
 
MOPP013 Coupler Kick for Very Short Bunches and its Compensation emittance, focusing, betatron, laser 580
 
  • M. Dohlus, I. Zagorodnov
    DESY, Hamburg
  • E. Gjonaj, T. Weiland
    TEMF, Darmstadt
  In this contribution we estimate two different effects: the kick due to asymmetry of the external accelerating field (coupler RF kick) and the kick due to electromagnetic field of the bunch scattered by the couplers (coupler wake kick). We take into acoount the cavities and calculate the periodic solution for bunch with an rms width of 300 mkm. The different possibilities for compensation of the kick are considered.  
 
MOPP121 Full Real-time Temperature Mapping System for 9-cell ILC-type Cavities power-supply, monitoring 841
 
  • A. Canabal, F. L. Krawczyk, R. J. Roybal, J. D. Sedillo, T. Tajima
    LANL, Los Alamos, New Mexico
  • S. Cohen
    Bira, Albuquerque, New Mexico
  • W. Haynes
    Fermilab, Batavia, Illinois
  The mapping of outer-wall temperatures during the vertical test of a superconducting radio-frequency (SRF) cavity has been one of the most successful tools in detecting the cavities’ critical hot spots. However, due to the excessive number of sensors needed, no fixed-type temperature mapping (T-mapping) system that covers all cells has been built for 9-cell cavities. With the consensus that T-mapping analysis is needed in order to improve the yield of high-gradient cavities, a system with a reduced data acquisition time and increased temperature sensitivity, compared to rotating-arm systems, has been developed at Los Alamos National Laboratory. The system consists of ~5,000 100 Ω 1/8W Allen-Bradley resistors placed azimuthally every 10 degrees, a similar number of other resistors and diodes that implement the switching scheme, and data acquisition codes written in Labview. The details of the system and first results are presented and discussed.  
 
MOPP128 Comparison of Stretched-wire, Bead-pull and Numerical Impedance Calculations on 3.9 GHz Dipole Cavities dipole, impedance, simulation, higher-order-mode 859
 
  • P. Goudket, C. D. Beard, P. A. McIntosh
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
  • G. Burt, A. C. Dexter
    Cockcroft Institute, Lancaster University, Lancaster
  • R. M. Jones
    Cockcroft Institute, Warrington, Cheshire
  In order to verify detailed impedance and wakefield simulations, the resonant modes in an aluminium model of the 9-cell ILC crab cavity were investigated using a stretched-wire frequency domain measurement, as well as frequency-domain bead-pull measurements. These measurements were compared to numerical simulations in order to verify that the complete cavity mode spectrum could be experimentally characterised for this high frequency structure. The analysis of the results and the accuracy and/or limitations of each method is presented.  
 
MOPP129 Compensation of Lorentz Force Detuning for SC Linacs (with Piezo Tuners) controls, linac, resonance, monitoring 862
 
  • M. K. Grecki, J. Andryszczak, T. Pozniak, K. P. Przygoda, P. M.S. Sekalski
    TUL-DMCS, Łódź
  The superconducting linacs use niobium cavities working with extremely high quality factor. Therefore the bandwidth of the cavity is very narrow and even subtle deformation caused by Lorentz force detunes the cavity a lot. For high gradient operation (over 15MV/m) the mechanical deformation of the cavity should be compensated by piezo tuner*. The paper presents design of a piezo control system and the results of measurements of its efficiency. It was demonstrated in FLASH accelerator that an initial detuning of 300Hz can be compensated by single pulse excitation of the piezo. The described system consist of multichannel programmable pulse generator driving a 8 channel piezo amplifiers capable to supply piezos with pulses up to 1A and up to 80V. It can compensate for Lorentz force detuning in all three FLASH cryhomodules equipped with piezos (ACC3,5,6).

*Liepe et al. "Dynamic Lorentz Force Compensation with a Fast Piezoelectric Tuner," PAC2001, pp. 1074-1076.

 
 
MOPP130 SRF Technology-Past, Present and Future Options superconductivity, vacuum, electron, controls 865
 
  • G. Myneni, M. Hutton
    Jefferson Lab, Newport News, Virginia
  Superconducting radiofrequency cavities for all recent projects (CEBAF, SNS, KEKB, and TTF) have been built from high purity polycrystalline niobium with a residual resistance ratio (RRR) greater than 250. The procedures and processes used from the initial production of the high RRR polycrystalline niobium sheets to the finished cavities are complex, numerous and very expensive, and the yield of SRF cavities meeting the performance specifications is very low. CBMM – Jefferson Lab invented the large grain and single crystal niobium technologies, and the use of niobium sliced directly from the ingots is expected to change the SRF technology outlook with fewer, and more streamlined, production processes that will not only be cost effective but also generate high yield. In this paper we will show that less stringent commercial niobium specifications are required, and explore the processes and procedures that will lay the foundation for producing SRF cavities with good quality factors at high peak magnetic fields in order to make this technology friendlier for future scientific and technological applications.  
 
MOPP158 Conceptual Design of Automated Systems for SRF Cavity Optical Inspection and Assembly linear-collider, collider, electron 922
 
  • T. Tajima, A. Canabal, T. A. Harden, R. J. Roybal
    LANL, Los Alamos, New Mexico
  The International Linear Collider (ILC) will require ~16,000 Superconducting Radio-Frequency (SRF) cavities at an accelerating gradient of 31.5 MV/m. One of the critical issues that needs to be addressed is the insufficient yield of high-gradient cavities that meet the requirement. This paper describes the design and initial tests of a cavity inner surface optical inspection system. Combined with a full-featured 9-cell cavity temperature mapping system being developed at LANL, we hope to be able to correlate the cavity heating and the surface condition causing it.  
 
TUZG01 IFMIF: Status and Developments target, beam-transport, rfq, plasma 974
 
  • P. Garin
    CEA, Gif-sur-Yvette
  On the way to the fusion demonstrator (DEMO), ITER is designed to tackle the physics properties of thermonuclear plasmas in relevant conditions, as well as the key technologies. But because of its experimental character, the amount of neutrons produced by ITER all along its life will be about two orders of magnitude below what is expected in a fusion Power Plant. A dedicated facility, called IFMIF (International Fusion Materials Irradiation Facility), is thus mandatory to study and analyse the behaviour of materials under a high flux of energetic neutrons (14 MeV). The Engineering Validation and Engineering Design Activities (EVEDA), launched in the framework of a bilateral agreement between Euratom and the Government of Japan in 2007, with a duration of 6 years, aims at producing the detailed design file enabling the construction of IFMIF. The key systems will be also tested during this phase. One of the most important one is the accelerator, bringing a deuteron beam of 125 mA to an output energy of 40 MeV. The whole facility will be described, including the detail of the accelerator, as well as the organisational framework of the project.  
slides icon Slides  
 
TUPC140 The Spallation Neutron Source Cryomodule Test Stand RF System controls, klystron, linac, monitoring 1395
 
  • M. T. Crofford, T. W. Hardek, D. Heidenreich, Y. W. Kang, K.-U. Kasemir, S.-H. Kim
    ORNL, Oak Ridge, Tennessee
  • J. A. Ball, T. L. Davidson
    ORNL RAD, Oak Ridge
  The Spallation Neutron Source (SNS) has recently commissioned a cryomodule test facility for the repair and testing of the super-conducting cryogenic cavities. This facility utilizes the original 402.5/805 MHz Radio Frequency (RF) Klystron Test Stand as its power source along with dual Low Level RF (LLRF) control systems. One control system is based on the standard SNS Linac LLRF controls with a second system for open-loop only control. The system is designed to allow simultaneous testing of devices in the test cave and other devices which can be tested outside of the enclosure. Initial tests have shown good results; some improvements are yet to be implemented. This paper will provide an overview of the RF systems, safety systems, and interlocks.  
 
TUPC153 Hardware-software Simulation for LLRF Control System Development simulation, controls, feedback, monitoring 1428
 
  • A. Vaccaro, L. R. Doolittle, A. Ratti, C. Serrano
    LBNL, Berkeley, California
  Field Programmable Gate Arrays (FPGA) have been used in accelerator controls for a long time. Stricter performance requirements in new accelerator designs force LLRF control systems to continuously improve, and the increasing density of available FPGAs enables such progress. The increased complexity in FPGA design is not always followed by new RF systems availability for development and testing. Therefore, a hardware-software simulation tool has been developed to model RF systems by a software simulator. It simulates the interaction of HDL code that is to be synthesized with both RF systems and communication ports to external controls software, reproducing realistic working conditions of the FPGA. The hardware-software interaction for LLRF control system design is discussed here.  
 
TUPD032 RFQ Vacuum Brazing at CERN vacuum, rfq, alignment, linac 1494
 
  • S. J. Mathot
    CERN, Geneva
  The aim of this paper is to describe the vacuum brazing procedure used at CERN for the brazing of Radio Frequency Quadrupole (RFQ). The RFQ is made of high precision machined OFE copper pieces assembled together. Vacuum brazing is one of the most promising techniques used to join the individual components leading to vacuum tightness and high precision alignment. The RFQ's brazed at CERN are made of four 100 or 120 cm long vanes (two majors and two minor vanes). Our brazing procedure consists of two steps. The first step involves the brazing of the four vanes in a horizontal position. The second step consists of brazing the vacuum stainless steel flanges to the copper structure in a vertical position. The paper describes the problems encountered with the alignment and the vacuum tightness. The difficulties related to the stress relaxation of the machined copper pieces during the brazing heat treatment are discussed. In addition, the solutions developed to improve the alignment of the brazed RFQ's are also presented.  
 
TUPP004 Evolution and Status of the Electronic Logbooks at the ESRF controls, power-supply, storage-ring, synchrotron 1532
 
  • L. Hardy, J. M. Chaize, O. Goudard
    ESRF, Grenoble
  • S. D. Cross, D. Fraser, N. V. Hurley
    St James Software, Cape Town
  In 2004 the ESRF moved to electronic logbooks. Such logbooks should be configurable enough to be used in several situations: document management, exchange of technical information and, in the Control Room, as a powerful tool for storing and retrieving information at a glance. The St James software company developed such a product which met our constraints and which is easy to configure. Moreover, this product can be tailored and evolved with time by its users and allows automatic access to control system parameters. After gaining experience with several logbooks using the old version 4 system, a new more user-friendly version which offers extensive customisation possibilities has been launched. This new version, J5, has already been interfaced to the ESRF control system (Tango) through a Python binding. This allows automatic triggering of records on specific events and the generation of automatic reports from the history database system. J5 can use an LDAP server for security management.  
 
TUPP097 New Formalism in the Spin Tracking Code Spink synchrotron, quadrupole, resonance, extraction 1756
 
  • A. U. Luccio, F. Lin
    BNL, Upton, Long Island, New York
  The code Spink*, in use for more than 10 years to track polarized hadrons in a synchrotron, was overhauled with the introduction of a new system of coordinates based on a generalized Frenet-Serret system in all dimensions in space, which allows a better treatment of the curvature of the reference orbit. Two more improvements are (a) treatment of tensor polarization for particles like polarized deuterons, and (b) inclusion of space charge and beam-beam effects, so the code can be used to track spin in synchrotrons with high luminosity like new generation colliders.

*A. U. Luccio. Proc. Adriatico Research Conf. on Trends in Colliders
Spin Physics. Trieste, Italy, 12/5-8, 1995.

 
 
WEPP056 Aperture Restriction Localisation in the LHC Arcs using an RF Mole and the LHC Beam Position Measurement System vacuum, dipole, monitoring, quadrupole 2644
 
  • O. R. Jones, J. Albertone, S. Bartolome-Jimenez, C. Boccard, T. Bogey, P. B. Borowiec, E. Calvo, F. Caspers, M. Gasior, J. L. Gonzalez, B. Jenninger, L. K. Jensen, T. Kroyer, S. Weisz
    CERN, Geneva
  Ensuring that the two 27km beam pipes of the LHC do not contain aperture restrictions is of utmost importance. Most of the ring is composed of continuous cryostats, so any intervention to remove aperture restrictions when the machine is at its operating temperature of 1.9K will require a substantial amount of time. On warming-up the first cooled sector, several of the sliding contacts which provide electrical continuity for the image current between successive sections of the vacuum chamber were found to have buckled into the beam pipe. This led to a search for a technique to verify the integrity of a complete LHC arc (~3km) before any subsequent cool-down. In this paper the successful results from using a polycarbonate ball fitted with a 40MHz RF transmitter will be presented. Propulsion of the ball is achieved by sucking filtered air through the entire arc, while its progress is traced every 54m via the LHC beam position measurement system which is auto-triggered by the RF transmitter on passage of the ball. Reflectometry at frequencies in the 4-8 GHz range can cover the gaps between beam position monitors and could therefore be used to localise a ball blocked by an obstacle.  
 
THPC142 The Operation Event Logging System of the SLS feedback, controls, linac, beam-losses 3318
 
  • A. Luedeke
    PSI, Villigen
  Modern 3rd generation synchrotron light sources aim for 100% availability. No single beam interruption is acceptable and every distortion of operation should be investigated: What caused the interruption? Can it be avoided in the future? If it can't be avoided, how can the recovery be accelerated? An automated event recording system has been implemented at the Swiss Light Source (SLS) in order to simplify this investigations. The system identifies distortions of the user operation and records automatically type and duration of the event. All relevant information connected to the event, from control system archive data to shift protocols, is linked to the event and presented in web pages. Additional information can be added manually. Each event will be assigned to a failure cause and area. Means to filter the events are provided. The paper will describe the concept and implementation of the even logging system at the SLS and the experiences with the system.