X-Band RF Structure and Beam Dynamics Workshop - 44th ICFA Advanced Beam Dynamics Workshop

Europe/Zurich
Cockcroft Institute

Cockcroft Institute

UK
Roger Jones (Cockcroft Inst)
Description

This will entail RF issues pertinent to X-band accelerating structures in linear colliders and light sources. In particular, RF fields in structures and cavities, wakefields, RF couplers and beam dynamics issues will be explored. The workshop will also embrace both active and passive overmoded and quasi-optical components Accelerating structures, light sources and drive beams will be amongst the areas of interest. A series of invited plenary talks will be given in addition to contributed topics. This will also include breakdown issues pertinent to high gradient structures, but the focus of the workshop will be on RF and impedance issues both from both a theoretical and experimental perspective. Papers submitted will be published on the JaCoW database.

    • 18:30 21:00
      Drinks reception and registration at Hoole Hall
    • 08:30 09:00
      Registration
    • 09:00 09:40
      Welcome and Introduction to Cockcroft Institute
      • 09:00
        Welcome to XB08 and opening announcements 10m
        Speaker: Dr Roger Jones (University of Manchester)
        Slides
      • 09:10
        Introduction to the Cockcroft Institute 15m
        Speakers: Dr Roger Jones (University of Manchester) , Prof. Swapan Chattopadhyay (Cockcroft Institute/University of Liverpool)
        Slides
      • 09:25
        Overview of ASTeC & ALICE 15m
        Speaker: Prof. Michael Poole (STFC Daresbury Laboratory)
    • 09:40 10:20
      Plenary Session (Chair R. Rimmer)
      • 09:40
        Overview of CLIC and Opportunities for Future Collaboration 40m
        Speaker: Prof. Jean-Pierre Delahaye (CERN)
        Slides
    • 10:20 10:40
      Coffee Break
    • 10:40 12:00
      Plenary Session (Chair T. Higo)
      • 10:40
        CLIC Main Linac Beam Dynamics 40m
        The beam dynamics in the CLIC main linac poses an important challenge and has a strong impact on the choice of basic design parameters. Careful beam line design, sophisticated beam-based alignment procedures and excellent stability of the components and RF are essential to preserve the beam quality during transport. The presentation will introduce into the different issues.
        Speaker: Dr Daniel Schulte
        Slides
      • 11:20
        Synergies between X-band for Linear Colliders and Light Sources 40m
        To compensate nonlinearities in the longitudinal phase space at the injector prototype of the PSI-XFEL, PSI requires a high frequency RF structure in X band. At the same time CLIC is pursuing a program for producing and testing high gradient RF structures in the X band, exploring the effect of different geometries and materials on break down limits and rates. Given that the PSI-XFEL has somewhat lower requirements in terms of gradient (40 MV/m) and efficiency, it may be interesting to share work and expense in designing and producing a common CLIC/PSI-XFEL structure. It would provide new data for the CLIC structure tests and be simultaneously a safe and low risk solution for the more relaxed operating gradient used at the PSI-XFEL. At the same time the prolonged operation of such a structure in the PSI FEL injector, albeit not at CLIC parameters, would constitute a good quality test for the procedure employed. As a generic type, we foresee to use a structure with a 5 pi/6 phase advance and an active length of 750 mm similar to NLC type H75. Since the structure should not be used to test higher order mode damping, it will not have any HOM dampers. On the other hand, two wake field monitors near the beginning and the end of the structure are foreseen to allow an optimum alignment to the beam. Wakefield monitors are also planned for CLIC structures and their implementation in the PSI-FEL structures will represent an important performance test. In addition, the structure will feature race track type input and output couplers minimizing quadrupolar kicks in the accelerating field.
        Speaker: Mr Micha Dehler
    • 12:00 13:40
      Lunch (plus CST Tutorial)
    • 13:40 15:20
      Plenary Session (Chair J.P. Delahaye)
      • 13:40
        PETS and drive beam development for CLIC 40m
        The CLIC Power Extraction and Transfer Structure (PETS) is a large-aperture and low-impedance periodic structure, in which the RF power is generated by a bunched drive-beam current. The PETS design procedure and the HOM damping strategy which has been developed for the PETS is reviewed. Control of local RF power production by an "ON/OFF" mechanism is discussed as well. Finally, the PETS high power testing program and recent results are presented.
        Speaker: Igor SYRATCHEV (CERN)
      • 14:20
        High-Gradient Single-Cell Tests at X-Band 20m
        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 gradient potential of normal-conducting, rf powered particle beam accelerators. The test setup consists of reusable mode launchers and short test structures and powered by SLAC’s XL-4 klystron. To date tested structures of different geometries including choke structures and structures made of different copper alloys. *This work was supported by the U.S. Department of Energy contract DE-AC02-76SF00515.
        Speaker: Dr Valery Dolgashev (SLAC)
        Slides
      • 14:40
        Wakefield Computations for the CLIC PETS using the Parallel Finite Element Time-Domain Code T3P 20m
        In recent years, SLAC's Advanced Computations Department (ACD) has developed the high-performance parallel 3D electromagnetic time-domain code, T3P, for simulations of wakefields and transients in complex accelerator structures. T3P is based on advanced higher-order Finite Element methods on unstructured grids with quadratic surface approximation. Optimized for large-scale parallel processing on leadership supercomputing facilities, T3P allows simulations of realistic 3D structures with unprecedented accuracy, aiding the design of the next generation of accelerator facilities. Applications to the CLIC Power Extraction and Transfer Structure (PETS) are presented. Work supported by DOE contract DE-AC02-76SF00515.
        Speaker: Dr Arno Candel (SLAC)
        Paper
        Slides
    • 15:20 15:40
      Coffee Break
    • 15:40 17:45
      WG1 Linear Colliders/Light Sources
      • 16:10
        DIAMOND and the New Light Source 30m
        Speaker: Dr Chris Christou (Diamond Light Source)
        Slides
      • 16:40
        X-Band Cavities - Dynamics Issues for Light Sources 35m
        Speaker: Hywel Owen (University of Manchester)
        Slides
      • 17:15
        FERMI@Elettra 20m
        Speaker: Dr Gerardo D'Auria (Elettra Trieste)
        Slides
      • 17:35
        Collimation studies for Linear Colliders 10m
        Speaker: Dr Steve Malton (RHUL)
        Paper
        Slides
    • 15:40 17:45
      WG2 RF Structures
    • 15:40 17:45
      WG3 Beam Dynamics
    • 15:40 17:45
      WG4 Industrial/Medical
      • 15:40
        CPI Klystron Developments 30m
        Speaker: Tony Johns
        Slides
      • 16:10
        I-Tech Industrial Solution for a Digital LLRF system 30m
        Speaker: Borut Baricevic
        Slides
      • 16:40
        Q-Par High Power RF Distribution Systems 30m
        Speaker: Simon Davies
        Slides
      • 17:10
        Twisted Waveguide Structures- Theory & Experiments 30m
        Speaker: Michael McStravick
        Slides
    • 08:30 10:20
      Plenary Session (Chair T. Garvey)
      • 08:30
        X-band High Gradient Research and a Two-Beam Test Facility at SLAC 30m
        In this presentation I will present a summary of the high-gradient accelerator structure efforts which have been done recently at SLAC. These include geometrical, materials, surface processing and theoretical and modeling studies. I will also discuss a possible test facility at SLAC which takes advantage of the SLAC linac infrastructure and klystrons to produce a 1 GeV, 10 A drive beam to drive a 30 GeV, 100 MeV/m X-band test accelerator.
        Speaker: Prof. Ronald Ruth
        Slides
      • 09:00
        Multipacting and Dark Current Simulations for the CLIC Accelerator Structures 40m
        Normal conducting accelerator structures such as the X-Band NLC structures and the CLIC structures have been found to suffer damage due to RF breakdown and/or dark current when processed to high gradients. Improved understanding of these issues is desirable for the development of structure designs and processing techniques to improve the structure performance at high gradient. While vigorous experimental efforts have been put forward to explore the gradient parameter space, comprehensive numerical simulations would help to gain insight of the problems via dark current and multipacting analysis. Over the past decade, SLAC has been developing a suite of 3D parallel finite-element codes aimed at high-accuracy, high-fidelity electromagnetic and beam physics simulations for the design and optimization of particle accelerators. Running on the latest supercomputers, these codes provide unprecedented capabilities in simulating large scale accelerator structure systems with realistic complexity of 3D details and with a fast turn around time. These codes have been applied to analyze the multipacting and dark current effects of the CLIC accelerator structures. This paper will present the progresses in the simulation of the CLIC HDX structure. *This work was supported by DOE contract No. DE-AC02-76SF00515.
        Speaker: Dr Zenghai Li
        Slides
      • 09:40
        CLIC Accelerating Structure Development 40m
        One of the most important objectives of the CLIC study is to demonstrate the design accelerating gradient of 100 MV/m in a fully featured accelerating structure under nominal operating conditions including pulse length and breakdown rate. The main issues which must be addressed and their interrelations are described along with the development and testing programs which have been put into place to accomplish this feasibility demonstration.
        Speaker: Dr Walter WUENSCH (CERN)
        Movie
        Paper
        Slides
    • 10:20 10:40
      Coffee Break
    • 10:40 12:00
      Plenary Session (Chair W. Wuensch)
      • 10:40
        Ultra-fast beam-based feedback for warm linear colliders 40m
        Review of the FONT all-analogue beam-based feedback system prototypes for use with e+e- colliders with very short bunchtrains
        Speaker: Dr Phil Burrows
        Slides
      • 11:20
        Aspects of Manifold Wakefield Suppression in Linear Colliders 40m
        Moderate damping of transverse wakefields is effected by slot-coupled manifolds and detuning of the characteristic modes. This manages the emittance dilution and also provides a built-in beam and structure diagnostic. A conspectus is presented on this technique together with potential future applications to CLIC.
        Speaker: Dr Roger Jones
        Slides
    • 12:00 13:40
      Lunch
    • 13:40 15:20
      Plenary Session (Chair R.M.Jones)
      • 13:40
        Drive Beam Dynamics for CLIC 40m
        The CLIC Drive Beam decelerator will extract the CLIC RF-power from the 100A Drive Beam. The energy spread in the beam will be up to 90%, and the focussing and alignment systems must ensure transport of particles of all energies through the decelerator sectors, ensuring minimal losses. This presentation summarizes the current status of the beam dynamic studies of the CLIC decelerator, including the effect of wake fields, the focusing strategy, the alignment strategy and resulting static and dynamic tolerances.
        Speaker: Erik Adli (European Organization for Nuclear Research (CERN))
      • 14:20
        Recent Results on CLIC X-Band Prototype Accelerating Structures 20m
        The CLIC study is conducting an extensive testing program towards a prototype accelerating structure suitable for a liner collider. The requirements for CLIC are a loaded gradient of 100 MV/m for pulse duration of 240 ns with a trip rate below 3*10-7 per meter. These accelerating structures are designed, fabricated and tested in collaboration between KEK, SLAC and CERN. Recent results from these experiments will be reported including a low group velocity accelerating structure which reached a gradient in excess of 100 MV/m with an acceptable breakdown rate.
        Speaker: Steffen Doebert (CERN)
        Paper
        Slides
      • 14:40
        A New Local Field Quantity Describing the High-Gradient Limit of Accelerating Structures 20m
        A new local field quantity which gives the high gradient performance limit of accelerating structures in the presence of vacuum rf breakdown is presented. A model of the breakdown trigger based on the pulsed heating of a potential breakdown site by the field emission currents and driven by a new field quantity, a modified Poynting vector, has been derived. The field quantity Sc takes into account both active and reactive power flow on the surface. This new quantity has been evaluated for many X-band and 30 GHz rf tests, both travelling wave and standing wave, and the value of Sc achieved in the experiments agrees well with analytical estimates.
        Speaker: Alexej Grudiev (CERN)
      • 15:00
        First Results from the CLIC Two-Beam Test Stand 20m
        The Two-beam Test Stand (TBTS) is part of the CTF3 complex at CERN and a unique facility which is designed to test key issues of the two-beam acceleration concept. In particular the power extraction structures (PETS) and the acceleration structures will be tested with beam. The installation of the beam lines was completed this Spring and in September the first drive beam passed all the way through to the beam dump. In October, a PETS structure was installed in the drive beam line. We report on design and commissioning of the facility and present results from the first runs with a PETS structure.
        Speaker: Roger Ruber (University of Uppsala)
        Slides
    • 15:20 15:40
      Coffee Break
    • 15:40 17:45
      Joint WG1 , WG2, WG3 & WG4
      • 15:40
        Thales Klystron Development io X-band 30m
        Speaker: Sebastien Berger
        Slides
      • 16:10
        Discussion for X-band Sources 30m
      • 16:40
        Linacs for Hadrontherapy: CABOTO, a X-band CArbon BOoster for Therapy in Oncology 30m
        Speaker: Riccardo Zennaro (CERN)
        Slides
      • 17:10
        Cost/MeV? 30m
    • 19:00 22:00
      Conference Dinner Ruthin Castle

      Ruthin Castle

    • 08:30 10:20
      Plenary Session (Chair R. Rimmer)
      • 08:30
        New Physics on the Horizon with CLIC 30m
        Speaker: Frederic Teubert (CERN)
        Slides
      • 09:00
        International X-band Linear Collider Accelerator Structure R&D 40m
        For more than fifteen years before the International Technology Recommendation Panel (ITRP) decision in August, 2004, there were intensive R&D activities and broad international collaboration among groups at SLAC, KEK, FNAL, LLNL and other labs for the room temperature X-Band accelerator structures. The goal was to provide an optimized design of the main linac structure for the NLC (Next Linear Collider) or GLC (Global Linear Collider). There have been two major challenges in developing X-band accelerator structures for the linear colliders. The first is to demonstrate stable, long-term operation at the high gradient (65 MV/m) that is required to optimize the machine cost. The second is to strongly suppress the beam induced long-range wakefields, which is required to achieve high luminosity. More than thirty X-band accelerator structures with various RF parameters, cavity shapes and coupler types have been fabricated and tested since 1989. A summary of the main achievements and experiences are presented in this talk including the structure design, manufacturing techniques, high power performance, and other structure related issues. Also, the new progress in collaborating with the CLIC, high gradient structures and X-Band structure applications for RF deflectors and others are briefly introduced.
        Speaker: Dr Juwen Wang
        Slides
      • 09:40
        Optimized Photonic Crystal Structures for Accelerators 40m
        Long-range wake fields are significantly reduced in accelerator structures that are based on dielectric photonic crystal cavities, which can be designed to trap modes only within a narrow frequency range (the band gap of the photonic crystal). A 2D photonic crystal structure can be used to create a 3D accelerator cavity by using metal end-plates to confine the fields in the third dimension; however, even when the 2D photonic structure allows only a single mode (in 2D), the 3D structure may trap higher order modes (HOMs), such as guided modes in the dielectric rods, that increase wake fields. For a 3D cavity based on a triangular lattice of dielectric rods, the rod positions can be optimized (breaking the lattice symmetry) to reduce radiation leakage using a fixed number of rods; this optimization can reduce leakage by more than 2 orders of magnitude while reducing the wake fields in the structure. This work is supported by the U.S. Department of Energy grant DE-FG02-04ER41317.
        Speaker: Prof. John Cary
        Slides
    • 10:20 10:40
      Coffee Break
    • 10:40 12:00
      Plenary Session (Chair T. Garvey)
      • 10:40
        Fully Axisymmetric X-Band RF Gun Structure 40m
        Bright, RF photocathode electron guns are the source of choice for most high-performance research accelerator applications. Some of these applications are pushing the performance boundaries of present state-of-the-art guns. A fully axisymmetric radiofrequency electron gun with an upstream power feed has been developed. The present device shows excellent promise in extending the performance of high-brightness sources. Simulations show that it easily breaks the benchmark emittance of one micron for 1 nC of bunch charge when followed by only a short booster accelerator. The pulse length in these simulations is less than 2 ps. While beam testing has not been possible to date, high power RF testing has been performed at a frequency of 11.43GHz using the magnicon facility at the Naval Research Laboratory (NRL). The successful testing proved out the basic design features of the gun with the achievement of a peak cathode accelerating field of 240MV/m. The simulated electron beam performance details will be presented along with the overall design of the gun and the results of the high power RF testing. The same geometry would also lend itself to thermionic applications.
        Speaker: Alan Todd (Advanced Energy Systems)
      • 11:20
        X-band Klystron Development at SLAC 40m
        The development of X-band klystrons at SLAC originated with the idea of building an X-band Linear Collider in the late 1980’s. Since then much effort has been expended in developing a reliable X-band Power source capable of delivering >50 MW RF power in pulse widths >1.5 μs. I will report on some of the technical issues and design strategies which have led to the current SLAC klystron designs.
        Speaker: Dr Arnold Vlieks
        Slides
    • 12:00 13:40
      Lunch
    • 13:40 15:20
      Plenary Session (Chair S. Chattopadhyay)
      • 13:40
        Fundamental Surface Science and Engineering Issues for High Gradient X-Band Structures at KEK 40m
        Since 1990, KEK has been studying the X-band accelerating structure fabrication technologies and has been strongly collaborating with SLAC. So far high gradient and wake field performance tests were carried out with both laboratories. Currently such items are being studied as various materials, surface preparation and assembly technologies in order to understand what determines breakdown performance and pulse heating damage. Especially the microscopic study on materials and surface preparations are experimentally performed. After realization of the high gradient accelerating structure, an order of a few ten thousands structure sections must be manufactured with cost effectively for the construction of a TeV energy range accelerator. In this presentation I will present a summary of the fabrication efforts at KEK for the high gradient structures and a future perspective of accelerating disk/quadrant fabrication technologies.
        Speaker: Dr Higashi Yasuo
        Slides
      • 14:20
        Applications of X-Ray Microfabrication Techniques for Accelerators 20m
        Modern microfabrication techniques based on deep X-ray lithography (LIGA), capable of producing high-aspect-ratio structures, are attractive and can be considered for the fabrication of metallic or dielectric planar structures suitable for high-frequency rf cavities and rf power sources. This paper will present an overview of this technology and a summary of work done at Argonne and elsewhere. * Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
        Speaker: Dr Alireza Nassiri (Argonne National Laboratory - DOE)
        Paper
        Slides
      • 14:40
        X-Band Deflector Development at SLAC 20m
        Design studies on the X-Band transverse rf deflectors operating at HEM11 mode have been made for two different applications. One is for beam measurements of time-sliced emittance and slice energy spread for the upgraded LCLS project, its optimization in rf efficiency and system design are carefully considered. Another is to design an ultra-fast rf kicker in order to pick up single bunches from the bunch-train of the B-factory storage ring. The challenges are to obtain very short structure filling time with high rf group velocity and good rf efficiency with reasonable transverse shunt impedance. Its rf system will be discussed
        Speaker: Dr Juwen Wang
        Slides
      • 15:00
        X-Band Crab Cavities for CLIC 20m
        The CLIC machine incorporates a 20 mrad crossing angle at the IP to aid the extraction of spent beams. In order to recover the luminosity lost through the crossing angle a crab cavity is proposed to rotate the bunches prior to collision. The crab cavity is chosen to have the same frequency as the main linac (11.9942 GHz) as a compromise between size, phase stability requirements and beam loading. It is proposed to use a HE11 mode travelling wave structure as the CLIC crab cavity in order to minimise beam loading and mode separation. The position of the crab cavity close to the final focus enhances the effect of transverse wake-fields so effective wake-field damping is required. A damped detuned structure is proposed to suppress and de-cohere the wake-field hence reducing their effect. Design considerations for the CLIC crab cavity will be discussed as well as the proposed high power testing of these structures at SLAC.
        Speaker: Graeme Burt (Cockcroft Institute)
    • 15:20 15:40
      Coffee Break
    • 15:40 17:45
      Joint WG1 Linear Colliders/Light Sources & WG 4 Industrial/Medical
      • 15:40
        X-band Components 30m
        Speaker: Igor SYRATCHEV (CERN)
        Slides
      • 16:10
        ILC LLRF System 30m
        Speaker: Mr Uros Mavric (Instrumentation Technologies)
        Slides
    • 15:40 17:45
      Joint WG2 RF Structures & WG3 Beam Dynamics
      • 15:40
        Dependence of the breakdown rate on the pulse shape 20m
        Speaker: Alexej Grudiev (CERN)
        Slides
      • 16:00
        Cavity design using globalised scattering matrix approach 25m
        Speaker: Dr Ian Shinton
        Slides
      • 16:25
        An alternate design for CLIC main linac wakefield suppression 20m
        Speaker: Mr Vasim Khan (University of Manchester/Cockcroft Institute)
        Slides
      • 16:45
        Introduction to beam dynamics simulation with Placet 20m
        Speaker: Erik Adli (European Organization for Nuclear Research (CERN))
        Slides
      • 17:05
        Beam dynamics simulations with Placet and Lucretia 25m
        Speaker: Mr Christopher Glasman
        Slides
    • 16:00 17:30
      Tour of ALICE Facility
    • 08:30 09:40
      Plenary Session (Chair D. Schulte): Closing Session
    • 09:40 12:00
      Plenary Session (Chair T. Higo)
      • 09:40
        Working Group 1 (Linear Collider and Light Sources) Summary 20m
        Speakers: Dr Chris Christou (Diamond Light Source) , Dr Micha Dehler (PSI)
        Slides
      • 10:00
        Working Group 2 (Structures) Summary 20m
        Speakers: Dr Juwen Wang (SLAC) , Toshiyasu Higo (KEK) , Dr Walter WUENSCH (CERN)
        Slides
      • 10:20
        Coffee Break 20m
      • 10:40
        Working Group 3 (Beam Dynamics) Summary 20m
        Speakers: Daniel Schulte (CERN) , Dr Roger Jones (University of Manchester)
        Slides
      • 11:00
        Working Group 4 (RF Sources/Medical/Industrial) Summary 20m
        Speakers: Peter McIntosh (STFC) , Richard Carter (Cockcroft Institute) , Tony Johns
        Slides
      • 11:20
        Closing Remarks 10m
        Speaker: Dr Roger Jones (University of Manchester)
        Slides
    • 12:00 13:00
      Lunch