Northern Illinois University, DeKalb, Illinois
Funding: Work supported by the Department of Defense under contract N00014-06-1-0587 with Northern Illinois University.
Numerical simulations of charged particle beams require an approximation to the particle distribution being simulated. Depending on the flavor of the N-body code, these approximations suffer from different computational difficulties. We briefly outline these difficulties, and present approximations to particle distributions using orthogonal functions. We discuss two different types of orthogonal functions, new in the context of beam simulations: wavelets and scaled Gauss-Hermite basis. On the wavelet side, we present the wavelet-based Poisson equation solver we recently devised for use in particle-in-cell beam simulations, and report on some important enhancements being implemented as a part of an ongoing project. On scaled Gauss-Hermite basis side, we report preliminary results in efficiently approximating discrete particle distributions in an orthogonal basis in which the corresponding potential and forces are directly and easily found from the expansion coefficients of the distribution. Finally, we discuss application of these particle distribution representations in simulation of coherent synchrotron radiation.
CLASSE, Ithaca, New York
BNL, Upton, Long Island, New York
CERN, Geneva
Evolution of short intense electron bunches passing through bunch-compressing beamlines is simulated using the UAL (Unified Accelerator Libraries) string space charge formulation. Excellent agreement is obtained with results obtained experimentally at CTF-II, the CERN "Compact Linear Collider'' test facility. The 40 MeV energy of these data is low enough for Coulomb and Biot-Savart forces to be important and high enough for coherent synchrotron radiation and centrifugal space charge forces to be important. UAL results are also compared with CSRtrack results for emittance growth in a 40 MeV 'standard' chicane. Vertical space charge forces are found to be important in this (low energy) case.
Osaka Prefecture University, Sakai
The coherent synchrotron and transition radiation from electron bunches of a linear accelerator (linac) has continuous spectra in a submillimeter to millimeter wavelength range at relatively high peak-intensities. This light source has been applied to absorption spectroscopy by the authors for various kinds of matters with relatively strong light absorbance such as water and aqueous solutions. The other important characteristics of the coherent radiation are picosecond pulsed light and the high peak intensity of the electric field which can be introduced into matters. In our new project the light source using the pulsed coherent synchrotron and transition radiation will be developed by using the electron beams of a 18 MeV S-band electron linac at Osaka Prefecture University (OPU). The pulse shape of the radiation has been evaluated from the shape of the electron bunch. The system of the light source has been optimized and is under construction. The light source will be applied to the pulsed excitation of matters and to the pump-probe experiment using the electron beam and the coherent radiation.
SLAC, Menlo Park, California
Static magnetic field undulators are capable of producing quasi-monochromatic synchrotron radiation of very high brightness. However, it is not possible to quickly change the properties such as polarization of the radiation in a static undulator. It is possible to construct an undulator using microwaves instead of static magnets where the electron beam is undulated by both electric and magnetic fields of an rf wave. A major advantage with a microwave undulator is that the radiation properties can be changed very quickly. The biggest challenge in developing a microwave undulator is in keeping the rf losses low. We are designing a microwave undulator with the aim of achieving at least a tenth of the flux obtained by the BL13 static magnetic field Elliptical Polarized Undulator in the SPEAR ring. We have considered circular waveguide modes and hybrid HE11 mode in a corrugated waveguide as possible candidates for the microwave undulator. It is found that a corrugated waveguide has the lowest rf losses with a very desirable field profile. It is also possible to use this device for a linac driven FEL. Our analysis of the corrugated waveguide cavity for the rf undulator will be presented.
KEK, Ibaraki
A new type of rotating anticathode X-ray generator has been developed, in which the electron beam irradiates the inner surface of a U-shaped anticathode. A high-flux electron beam is focused on the inner surface by optimizing the shape of the bending magnet. In order to minimize the sizes of the X-ray source, the electron beam is focused strongly in a short distance by the bending magnet which is small and is close to the rotating anticathode. The power of the electron beam can be increased to the point at which the irradiated part of the inner surface is melted, because a strong centrifugal force fixes the melted part on the inner surface. We have achieved emission of X-rays 10 times more brilliant than can be attained by a conventional rotating anticathode. The development is still in progress. New results will be reported in detail.
Northern Illinois University, DeKalb, Illinois
Fermilab, Batavia
LBNL, Berkeley, California
Funding: Work supported by Fermi Research Alliance LLC. Under DE-AC02- 07CH11359 with the U.S. DOE and by the Department of Education under contract P116Z010035 with Northern Illinois University
Fermilab is currently constructing a GeV-scale electron accelerator test facility. The accelerator will serve as a backbone for several Fermilab R&D programs, e.g., to test subsystem associated to project-X, ILC and the muon collider program. It is also anticipated that this facility will support beam physics and accelerator R&D programs such as testing of novel acceleration techniques, beam diagnostics and radiation sources concepts. In this paper we describe a possible option for the electron injector based on a photoemission rf gun. Optimization and performance studies of this ~50 MeV photoinjector are performed with various tracking programs (Astra, GPT, Impact-T, Impact-Z). We explore the performances of the magnetic bunch compressor which is extremely challenging at 50 MeV due to strong phase space dilution via collective effects (space charge and coherent synchrotron radiation). We also investigate the generation of flat beams with very high transverse emittance ratio using a round-to-flat beam transformer.
DESY, Hamburg
The local thermal breakdown (quench) behavior of one- and nine-cell SCRF Nb accelerator cavities is investigated systematically. For more than 50 cavities, temperature mapping data have been analyzed with respect to surface preparation, Nb material etc. Results on quench location and characteristic correlations are presented.
ESRF, Grenoble
Synchrotron X-rays and neutrons provide unique microscopic information on the structures and dynamics of condensed matter. These probes are essential tools for biologists, chemists, physicists and materials scientists and have become increasingly important in a remarkably wide range of disciplines, from palaeontology to medicine. The electron storage rings producing synchrotron radiation, and fission reactor or spallation neutron sources, are usually situated at major national or international laboratories. Such central research facilities are exemplified by the two international laboratories in Grenoble, the European Synchrotron Radiation Facility and the Institut Laue-Langevin. After a discussion of the sources used to produce synchrotron radiation and neutron beams, some of the instrumentation and methods used in the investigation of materials will be described, with illustrative examples of recent research. Finally, some major X-ray and neutron sources under construction or at the planning stage will be described, including several where linac technology plays an important role (e.g. the XFEL at DESY and the SNS at ORNL).