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Venturini, M.

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TUPEC027 Microbunching and RF Compression 1776
 
  • M. Migliorati
    Rome University La Sapienza, Roma
  • M. Ferrario, C. Vaccarezza
    INFN/LNF, Frascati (Roma)
  • C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
  • M. Venturini
    LBNL, Berkeley, California
 
 

Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.

 
TUPEC028 Microbunching Instability Effect Studies and Laser Heater Optimization for the SPARX FEL Accelerator 1779
 
  • C. Vaccarezza, E. Chiadroni, M. Ferrario
    INFN/LNF, Frascati (Roma)
  • G. Dattoli, L. Giannessi, M. Quattromini, C. Ronsivalle
    ENEA C.R. Frascati, Frascati (Roma)
  • M. Migliorati
    Rome University La Sapienza, Roma
  • M. Venturini
    LBNL, Berkeley, California
 
 

The effects of microbunching instability for the SPARX accelerator have been analyzed by means of different numerical simulation codes and analytical approach. The laser heater counteracting action has been also addressed in order to optimize the parameters of the compression system, either hybrid RF plus magnetic chicane or only magnetic, and possibly enhance the FEL performance.

 
TUPD072 E-cloud Driven Single-bunch Instabilities in PS2 2087
 
  • M. Venturini, M.A. Furman, G. Penn, R. Secondo, J.-L. Vay
    LBNL, Berkeley, California
  • R. De Maria, Y. Papaphilippou, G. Rumolo
    CERN, Geneva
 
 

One of the options under consideration for a future upgrade of the LHC injector complex includes the replacement of PS with PS2 (a longer circumference and higher energy ring). Efforts are currently underway to design the new machine and characterize the beam dynamics. Electron cloud effects represent a potentially serious limitation to the achievement of the upgrade goals. We report on ongoing numerical studies aiming at estimating the e-cloud density threshold for the occurrence of single bunch instabilities or significant degradation of the beam emittance. We present selected results obtained in the more familiar quasi-static approximation and/or in the Lorentz-boosted frame.

 
WEOBRA02 Simulation of E-Cloud Driven Instability and its Attenuation using a Feedback System in the CERN SPS 2438
 
  • J.-L. Vay, J.M. Byrd, M.A. Furman, G. Penn, R. Secondo, M. Venturini
    LBNL, Berkeley, California
  • J.D. Fox, C.H. Rivetta
    SLAC, Menlo Park, California
 
 

Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch transverse coherent oscillations that may otherwise be amplified during the interaction of the beam with ambient electron clouds. We have used the simulation package WARP-POSINST to study the growth rate and frequency patterns in space-time of the electron cloud driven transverse instability in the CERN SPS accelerator with, or without, an idealized feedback model for damping the instability. We will present our latest simulation results, contrast them with actual measurements and discuss the implications for the design of the actual feedback system.

 

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TUYMH02 Electron Cloud at Low Emittance in CesrTA 1251
 
  • M.A. Palmer, J.P. Alexander, M.G. Billing, J.R. Calvey, C.J. Conolly, J.A. Crittenden, J. Dobbins, G. Dugan, N. Eggert, E. Fontes, M.J. Forster, R.E. Gallagher, S.W. Gray, S. Greenwald, D.L. Hartill, W.H. Hopkins, D.L. Kreinick, B. Kreis, Z. Leong, Y. Li, X. Liu, J.A. Livezey, A. Lyndaker, J. Makita, M.P. McDonald, V. Medjidzade, R.E. Meller, T.I. O'Connell, S.B. Peck, D.P. Peterson, G. Ramirez, M.C. Rendina, P. Revesz, D.H. Rice, N.T. Rider, D. L. Rubin, D. Sagan, J.J. Savino, R.M. Schwartz, R.D. Seeley, J.W. Sexton, J.P. Shanks, J.P. Sikora, E.N. Smith, C.R. Strohman, H.A. Williams
    CLASSE, Ithaca, New York
  • F. Antoniou, S. Calatroni, M. Gasior, O.R. Jones, Y. Papaphilippou, J. Pfingstner, G. Rumolo, H. Schmickler, M. Taborelli
    CERN, Geneva
  • D. Asner
    Carleton University, College of Natural Sciences, Ottawa, Ontario
  • L. Boon, A.F. Garfinkel
    Purdue University, West Lafayette, Indiana
  • J.M. Byrd, C.M. Celata, J.N. Corlett, S. De Santis, M.A. Furman, A. Jackson, R. Kraft, D.V. Munson, G. Penn, D.W. Plate, M. Venturini
    LBNL, Berkeley, California
  • B.T. Carlson
    Grove City College, Grove City, Pennsylvania
  • T. Demma
    INFN/LNF, Frascati (Roma)
  • R.T. Dowd
    ASCo, Clayton, Victoria
  • J.W. Flanagan, P. Jain, K. Kanazawa, K. Kubo, K. Ohmi, H. Sakai, K. Shibata, Y. Suetsugu, M. Tobiyama
    KEK, Ibaraki
  • D. Gonnella
    Clarkson University, Potsdam, New York
  • W. Guo
    BNL, Upton, Long Island, New York
  • K.C. Harkay
    ANL, Argonne
  • R. Holtzapple
    CalPoly, San Luis Obispo, CA
  • J.K. Jones, A. Wolski
    Cockcroft Institute, Warrington, Cheshire
  • D. Kharakh, J.S.T. Ng, M.T.F. Pivi, L. Wang
    SLAC, Menlo Park, California
  • M.C. Ross, C.-Y. Tan, R.M. Zwaska
    Fermilab, Batavia
  • L. Schächter
    Technion, Haifa
  • E.L. Wilkinson
    Loyola University, Chicago, Illinois
 
 

The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. Finally a range of EC mitigation methods have been deployed and tested. Measurements of cloud density and its impact on the beam under a range of conditions will be presented and compared with simulations. The effectiveness of a range of mitigation techniques will also be discussed.

 

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TUPD022 CesrTA Retarding Field Analyzer Modeling Results 1970
 
  • J.R. Calvey, J.A. Crittenden, G. Dugan, S. Greenwald, Z. Leong, J.A. Livezey, M.A. Palmer
    CLASSE, Ithaca, New York
  • C.M. Celata
    Cornell University, Ithaca, New York
  • M.A. Furman, M. Venturini
    LBNL, Berkeley, California
  • K.C. Harkay
    ANL, Argonne
 
 

Retarding field analyzers (RFAs) provide an effective measure of the local electron cloud density and energy distribution. Proper interpretation of RFA data can yield information about the behavior of the cloud, as well as the surface properties of the instrumented vacuum chamber. However, due to the complex interaction of the cloud with the RFA, particularly in regions of high magnetic field, understanding these measurements can be nontrivial. This paper will examine different methods for interpreting RFA data via cloud simulation programs. Possible techniques include postprocessing the output of a simulation code to predict the RFA response, and incorporating an RFA model into the program itself.

 
TUPD024 Progress in Studies of Electron-cloud-induced Optics Distortions at CesrTA 1976
 
  • J.A. Crittenden, J.R. Calvey, G. Dugan, D.L. Kreinick, Z. Leong, J.A. Livezey, M.A. Palmer, D. L. Rubin, D. Sagan
    CLASSE, Ithaca, New York
  • M.A. Furman, G. Penn, M. Venturini
    LBNL, Berkeley, California
  • K.C. Harkay
    ANL, Argonne
  • R. Holtzapple
    CalPoly, San Luis Obispo, CA
  • M.T.F. Pivi, L. Wang
    SLAC, Menlo Park, California
 
 

The Cornell Electron Storage Ring Test Accelerator (CesrTA) program has included extensive measurements of coherent tune shifts for a variety of electron and positron beam energies, bunch current levels, and bunch train configurations. The tune shifts have been shown to result primarily from the interaction of the beam with the space-charge field of the beam-induced low-energy electron cloud in the vacuum chamber. Comparison to several advanced electron cloud simulation program packages has allowed determination of the sensitivity of these measurements to physical parameters such as the synchrotron radiation flux, its interaction with the vacuum chamber wall, the beam emittance and lattice optics, as well as to those of the various contributions to the electron secondary yield model. We report on progress in understanding the cloud buildup and decay mechanisms in magnetic fields and in field-free regions, addressing quantitatively the precise determination of the physical parameters of the modelling. Validation of these models will serve as essential input in the design of damping rings for future high-energy linear colliders.

 
TUPE069 A Proof-of-principle Echo-enabled Harmonic Generation FEL Experiment at SLAC 2293
 
  • M.P. Dunning, E.R. Colby, Y.T. Ding, J.T. Frederico, A. Gilevich, C. Hast, R.K. Jobe, D.J. McCormick, J. Nelson, T.O. Raubenheimer, K. Soong, G.V. Stupakov, Z.M. Szalata, D.R. Walz, S.P. Weathersby, M. Woodley, D. Xiang
    SLAC, Menlo Park, California
  • J.N. Corlett, G. Penn, S. Prestemon, J. Qiang, D. Schlueter, M. Venturini, W. Wan
    LBNL, Berkeley, California
  • P.L. Pernet
    EPFL, Lausanne
 
 

In this paper we describe the technical design of an on-going proof-of-principle echo-enabled harmonic generation (EEHG) FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment was designed through late 2009 and built and installed between October 2009 and January 2010. We present the design considerations, the technical realization and the expected performances of the EEHG experiment.

 
TUPE072 Preliminary results of the echo-seeding experiment ECHO-7 at SLAC 2299
 
  • D. Xiang, E.R. Colby, Y.T. Ding, M.P. Dunning, J.T. Frederico, A. Gilevich, C. Hast, R.K. Jobe, D.J. McCormick, J. Nelson, T.O. Raubenheimer, K. Soong, G.V. Stupakov, Z.M. Szalata, D.R. Walz, S.P. Weathersby, M. Woodley
    SLAC, Menlo Park, California
  • J.N. Corlett, G. Penn, S. Prestemon, J. Qiang, D. Schlueter, M. Venturini, W. Wan
    LBNL, Berkeley, California
  • P.L. Pernet
    EPFL, Lausanne
 
 

ECHO-7 is a proof-of-principle echo-enabled harmonic generation* FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which is the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.


* G. Stupakov, PRL, 102, 074801 (2009); D. Xiang and G. Stupakov, PRST-AB, 12, 030702 (2009).

 
WEPEA067 Design Studies for a VUV-Soft X-ray FEL Facility at LBNL 2639
 
  • J.N. Corlett, K.M. Baptiste, J.M. Byrd, P. Denes, R.W. Falcone, J. Feng, J. Kirz, D. Li, H.A. Padmore, C. F. Papadopoulos, G. Penn, J. Qiang, D. Robin, R.D. Ryne, F. Sannibale, R.W. Schoenlein, J.W. Staples, C. Steier, T. Vecchione, M. Venturini, W. Wan, R.P. Wells, R.B. Wilcox, J.S. Wurtele, A. Zholents
    LBNL, Berkeley, California
  • A.E. Charman, E. Kur
    UCB, Berkeley, California
 
 

Recent reports have identified the scientific requirements for a future soft x-ray light source and a high-repetition-rate FEL facility responsive to them is being studied at LBNL. The facility is based on a CW superconducting linear accelerator with beam supplied by a high-brightness, high-repetition-rate photocathode electron gun, and on an array of FELs to which the beam is distributed, each operating at high repetition rate and with even pulse spacing. Dependent on the experimental requirements, the individual FELs may be configured for either SASE, HGHG, EEHG, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds. We are developing a design concept for a 10‐beamline, coherent, soft x‐ray FEL array powered by a 2.5 GeV superconducting accelerator operating with a 1 MHz bunch repetition rate. Electron bunches are fanned out through a spreader, distributing beams to an array of 10 independently configurable FEL beamlines with nominal bunch rates up to 100 kHz. Additionally, one beamline could be configured to operate at higher repetition rate.

 
WEPE097 Recommendation for the Feasibility of More Compact LC Damping Rings 3578
 
  • M.T.F. Pivi, L. Wang
    SLAC, Menlo Park, California
  • C.M. Celata, M.A. Furman, M. Venturini
    LBNL, Berkeley, California
  • J.A. Crittenden, G. Dugan, M.A. Palmer
    CLASSE, Ithaca, New York
  • T. Demma, S. Guiducci
    INFN/LNF, Frascati (Roma)
  • K.C. Harkay
    ANL, Argonne
  • O.B. Malyshev
    Cockcroft Institute, Warrington, Cheshire
  • K. Ohmi, K. Shibata, Y. Suetsugu
    KEK, Ibaraki
  • Y. Papaphilippou, G. Rumolo
    CERN, Geneva
 
 

As part of the International Linear Collider (ILC) collaboration, we have compared the electron cloud effect for different Damping Ring designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. These studies were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design and would allow to considerably reduce the number of components, wiggler magnets and costs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.