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radio-frequency

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MO6PFP056 Electromagnetic SCRF Cavity Tuner cavity, resonance, linear-collider, collider 262
 
  • V.S. Kashikhin, E. Borissov, G.W. Foster, T.N. Khabiboulline, A. Makulski, Y.M. Pischalnikov
    Fermilab, Batavia
 
 

Funding: Department of Energy, U.S.A.


A novel prototype of SCRF cavity tuner is being designed and tested at Fermilab. This is a superconducting C-type iron dominated magnet having a 10 mm gap, axial symmetry, and a 1 Tesla field. Inside the gap is mounted a superconducting coil capable of moving ± 1 mm and producing a longitudinal force up to ± 1.5 kN. The static force applied to the RF cavity flanges provides a long- term cavity geometry tuning to a nominal frequency. The same coil powered by a fast AC current pulse delivers mechanical perturbation for fast cavity tuning. This fast mechanical perturbation could be used to compensate a dynamic RF cavity detuning caused by cavity Lorentz forces and microphonics. A special configuration of magnet system was designed and tested.

 
TU5PFP040 Novel Geometries for the LHC Crab Cavity cavity, damping, dipole, HOM 909
 
  • B.D.S. Hall, G. Burt
    Cockcroft Institute, Lancaster University, Lancaster
  • R. Calaga
    BNL, Upton, Long Island, New York
  • J.R. Delayen, R.A. Rimmer, H. Wang
    JLAB, Newport News, Virginia
  • J.D.A. Smith
    Lancaster University, Lancaster
 
 

In 2017 the LHC is envisioned to increase is luminosity via an upgrade. This upgrade is likely to require a large crossing angle hence a crab cavity is required to align the bunches prior to collision. There are two possible schemes for crab cavity implementation, global and local. In a global crab cavity the crab cavity is far from the IP and the bunch rotates back and forward as it traverses around the accelerator in a closed orbit. For this scheme a two cell elliptical squashed cavity at 800 MHz is preferred. To avoid any potential beam instabilities all the modes of the cavities must be damped strongly, however crab cavities have lower order and same order modes in addition to the usual higher order modes and hence a novel damping scheme must be used to provide sufficient damping of these modes. In the local scheme two crab cavities are placed at each side of the IP two start and stop rotation of the bunches. This would require crab cavities much smaller transversely than in the global scheme but the frequency cannot be increased any higher due to the long bunch length of the LHC beam. This will require a novel compact crab cavity design.

 
TU6RFP059 Experimental Studies of the ReA3 Triple-Harmonic Buncher cyclotron, linac, quadrupole, ECR 1686
 
  • Q. Zhao, V.A. Andreev, J. Brandon, G. Machicoane, F. Marti
    NSCL, East Lansing, Michigan
 
 

Funding: Michigan State University


The National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) is implementing a system called the ReA3 to reaccelerate rare isotope beams from projectile fragmentation to energies of about 3 MeV/u. The 80.5 MHz triple-harmonic buncher before the ReA3 Radio Frequency Quadrupole (RFQ) linac has recently been implemented and measurements made. Tests using beams from the Electron Cyclotron Resonance (ECR) ion source test stand are being performed. The beam properties after the buncher are fully characterized using various diagnostic tools (e.g. fast Faraday cup, energy analyzer, emittance scanner). As a result, the tuning procedures for the buncher operations are developed. We will present the detailed results of the beam based buncher studies and compare them with simulations.

 
WE4RAI01 Optimal Design and Operation of Helium Refrigeration Systems cryogenics, neutron, target, extraction 1931
 
  • V. Ganni
    JLAB, Newport News, Virginia
 
 

Helium refrigerators are of keen interest to present and future particle physics programs utilizing superconducting magnet or radio frequency (RF) technology. They typically utilize helium refrigeration at and below 4.5-Kelvin (K) temperatures and are very energy intensive. After an overview of the quality of energy, basic processes used for cryogenics, the Carnot step (as defined by the author) and cycle design theory, the concept of overall process optimization is presented. In particular the question of ‘what is an optimum system’ will be discussed. In this regard, the Ganni cycle and floating pressure control philosophy will be examined with respect to a more traditional approach as a solution to an optimum system for new designs and existing systems.

 

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Slides

 
WE5PFP060 Buffered Electropolishing – A New Way for Achieving Extremely Smooth Surface Finish on Nb SRF Cavities to be Used in Particle Accelerators cavity, SRF, cathode, superconductivity 2141
 
  • A.T. Wu, G. Ciovati, R. Manus, H.L. Phillips, C.E. Reece, R.A. Rimmer, W. Sommer, H. Tian, J.S. Williams
    JLAB, Newport News, Virginia
  • F. Eozénou
    CEA, Gif-sur-Yvette
  • S. Jin, L. Lin, X.Y. Lu, E. Wang
    PKU/IHIP, Beijing
  • J. Mammosser
    ORNL, Oak Ridge, Tennessee
 
 

Funding: Notice: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.


A new surface treatment technique for niobium (Nb) Superconducting Radio Frequency (SRF) cavities called Buffered Electropolishing (BEP) has been developed at JLab. It was found that BEP could produce the smoothest surface finish on Nb samples ever reported in the literature. Experimental results revealed that the Nb removal rate of BEP could reach as high as 4.67 μm/min. This is significantly faster* than that of the conventional electropolishing technique employing an acid mixture of HF and H2SO4. An investigation is underway to determine the optimum values for all relevant BEP parameters so that the high quality of surface finish achieved on samples can be realized within the geometry of an elliptical RF cavity. Toward this end, single cell Nb cavities are being electropolished by BEP at both CEA-Saclay and JLAB. These cavities will be RF tested and the results will be reported through this presentation.


*Xiangyang Lu et al, to be published.

 
TH6REP024 A Proposal of a Single Coupler Cavity Beam Position Monitor cavity, coupling, simulation, dipole 4000
 
  • A. Lyapin
    UCL, London
  • S.T. Boogert
    Royal Holloway, University of London, Surrey
 
 

Cavity beam position monitors (CBPM) made a significant progress in the last 10 years with an entire nano-beamline relying on them being currently commissioned at ATF2 (KEK). The major improvement was the introduction of the mode selective coupling allowing for efficient rejection of unwanted monopole modes. We propose another step towards creating a simple and cost effective CBPM - a cavity using just one coupler (instead of 2 or even 4) to couple out both polarisations of the dipole mode. The x and y signals are then split in the mixing stage of the electronics, so that only one expensive high-frequency electronics front-end is used for both x and y. A very good separation of the x and y signals can be achieved with a reasonable performance mixer assembly. In this paper we present the concept and provide some simulation results proving this processing scheme.

 
TH6REP034 Evaluation of Bergoz Instrumentation NPCT vacuum, instrumentation, cavity, HOM 4021
 
  • D.J. Martin, S. Allison, B. Scott, J.J. Sebek, T.A. Trautwein
    SLAC, Menlo Park, California
 
 

Funding: Operated by Stanford University for the U. S. Department of Energy under Contract DE-AC02-76-SF00515 and Office of Basic Energy Sciences.


The Bergoz Instrumentation New Parametric Current Transformer (NPCT) has been evaluated at the SPEAR3 synchrotron light source. The device was tested for vacuum performance and residual gas and was found suitable for installation in the storage ring. The NPCT was installed during August 2008 and has measured beam currents to 500 mA. Performance is compared to the earlier PCT design. The NPCT Sensor Head has been instrumented with thermal sensors for characterization of the internal operating temperature.

 
TH6REP076 Hardware-Based Fast Communications for Feedback Systems feedback, controls, LLRF, alignment 4132
 
  • L.R. Doolittle, A. Ratti, C. Serrano, A. Vaccaro
    LBNL, Berkeley, California
  • L.R. Dalesio, Y. Tian
    BNL, Upton, Long Island, New York
 
 

The performance of feedback control systems is limited by latency. The hardware-based fast communication system described here offers means for deterministic, fault-tolerant data transmission for feedback systems requiring low-latency communications, such as orbit feedback and Radio Frequency (RF) controls.

 
FR5PFP068 Wakefield Simulation of CLIC PETS Structure Using Parallel 3D Finite Element Time-Domain Solver T3P wakefield, simulation, impedance, damping 4467
 
  • A.E. Candel, A.C. Kabel, K. Ko, L. Lee, Z. Li, C.-K. Ng, G.L. Schussman
    SLAC, Menlo Park, California
  • I. Syratchev
    CERN, Geneva
 
 

Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.


In recent years, SLAC's Advanced Computations Department (ACD) has developed the parallel 3D Finite Element electromagnetic time-domain code T3P. Higher-order Finite Element methods on conformal unstructured meshes and massively parallel processing allow unprecedented simulation accuracy for wakefield computations and simulations of transient effects in realistic accelerator structures. Applications include simulation of wakefield damping in the Compact Linear Collider (CLIC) Power Extraction and Transfer Structure (PETS).

 
FR5REP067 Novel Integrated Design Method and Beam Dynamics Simulations for the FETS RFQ Cold Model rfq, simulation, emittance, FEL 4929
 
  • S. Jolly, M.J. Easton, P. Savage
    Imperial College of Science and Technology, Department of Physics, London
  • A.P. Letchford, J.K. Pozimski
    STFC/RAL, Chilton, Didcot, Oxon
 
 

A 4m-long, 324MHz four-vane RFQ, consisting of four coupled sections, is currently being designed for the Front End Test Stand (FETS) at RAL in the UK. Previous beam dynamics simulations, based on field maps produced with a field approximation code, provide a baseline for the new design. A novel design method is presented that combines the CAD and electromagnetic modelling of both the RFQ tank and the vane modulations with more sophisticated beam dynamics simulations using the General Particle Tracer code (GPT). This approach allows the full integration of the optimisation of the RFQ, based on beam dynamics simulations using a 3D EM-field map of the CAD model, with the design and manufacture of the RFQ vane modulations and RFQ tank. The design process within the Autodesk Inventor CAD software is outlined and details of the EM modelling of the RFQ in CST EM Studio are given. Results of beam dynamics simulations in GPT are presented and compared to previous results with field approximation codes. Finally, possible methods of manufacture based on this design process are discussed.