UCLA, Los Angeles, USA
SLAC, Menlo Park, California, USA
UCLA, Los Angeles, California, USA
Acceleration of electrons in wakefields set up by a series of drive bunches in a dielectric structure has been proposed as a possible component of next-generation accelerators. Here, we discuss future experimental work with a slab sub-millimeter dielectric loaded accelerator structure that in contrast to conventional dielectric tubes should diminish the effects of transverse wakes and will permit higher total charge to be accelerated. The proposed experiment will allow the generation of unprecedented peak power at THz frequencies. In addition, it can generate ~50-150 MV/m drive fields and thus will allow the testing of acceleration using witness and drive beams. We examine details of the geometry and composition of the structures to be used in the experiment.
SLAC, Menlo Park, California, USA
FACET at SLAC provides high charge, high peak current, low emittance electron beam that is bunched at THz wavelength scale during its normal operation. A THz light source based coherent transition radiation (CTR) from this beam would potentially be the brightest short-pulse THz source ever constructed. Efforts have been put into building this photon source together with a user area, to provide a platform to utilize this unique THz radiation for novel nonlinear and ultrafast phenomena researches and experiments.
JLAB, Newport News, Virginia, USA
UMD, College Park, Maryland, USA
High average current and high brightness electron beams are needed for many applications. At the Jefferson Lab FEL facility, the search for dark matter with the FEL laser beam has produced interesting results*, and a second very promising method for dark matter search using JLab Energy-recovery-linac (ERL) machine has been put forward**. Although the required beam current has been achieved on this machine, one key challenge is the management of beam halo. UMD has demonstrated a high dynamic range halo measurement method using a digital micro-mirror array device. A similar system has been established at JLab FEL facility as a joint effort by UMD and JLab to measure the beam halo on the high current ERL machine***. The experiment and characterization are being performed while the new UV FEL is running for optimization. In this paper, the limitations of the current system will be analyzed and study of other approaches (such as an optimized coronagraph) for further extending measuring dynamic range will be presented. In particular, we will discuss in detail the possibility of performing both longitudinal and transverse (3D) halo measurement altogether on one single system.
* A. Afanasev, et al., PRL. 101 120401 (2008).
** J. Thale, Searching for a New Gauge Boson at JLab, Newport News, VA, September 20-21, 2010
*** H. Zhang, et al., this conference.
UCLA, Los Angeles, California, USA
Preparations for a high energy gain inverse free electron laser (IFEL) experiment using an undulator and Brookhaven National Lab’s (BNL) Accelerator Test Facility’s (ATF) terawatt CO2 laser are underway. 3D simulations suggest that the experiment will likely accelerate a 50 MeV beam to 117 MeV in 54 cm while maintaining a low energy spread. The helical undulator is currently under construction at UCLA’s Particle Beam Physics Laboratory.
Fermilab, Batavia, USA
SLAC, Menlo Park, California, USA
Photonic band gap (PBG) fibers with hollow core defects are being designed and fabricated for use as laser driven accelerators because they appear capable of providing gradients of several GeV/m at picosecond pulse lengths. While we expect to have fiber down to 1.5-2.0 micron wavelengths we still lack a viable means for efficient coupling of laser power into these structures. The reasons for this include the very different character of these TM-like modes from those familiar in the telecom field and the fact that the defect must function as both a longitudinal waveguide for the accelerating field and a transport channel for the particles. We discuss the status of our coupling work in terms of what has been done and the options we are pursuing for both end and side coupling. In both basic coupler types, the symmetry of the PBG crystal leads to significant differences between this and the telecom field. We show that side coupling provides more possibilities and is preferred. Our motivation is to test new fiber for gradient, mode content and throughput on the NLCTA at SLAC.
LBNL, Berkeley, California, USA
Tech-X, Boulder, Colorado, USA
Ionization injection into a laser wakefield accelerator is studied by multi-dimensional particle-in-cell (PIC) simulations. To obtain low energy spread beams we use a short region of gas mixture (H+N) near the start of the stage to trap electrons, while the remainder of the stage uses pure H and is injection-free. Effects of gas mix parameters, including concentration and length of the mixture region, on the final electron injection number and beam quality are studied. Two dimensional PIC simulations show the injected electron beam has filament structures in the plane perpendicular to the laser polarization direction in early time and this structure disappears later due to the betatron oscillation of the electrons in the wakefield. Synchrotron radiation from the accelerated electrons is calculated by a post processing code - Virtual Detector for Synchrotron Radiation (VDSR).
USC, Los Angeles, California, USA
UCLA, Los Angeles, California, USA
In the non-linear or blow-out regime of a plasma wakefield, the electrons of the accelerated bunch oscillate in a pure ion column. It was demonstrated that a single bunch can emit betatron radiation in the keV to MeV range*. In a drive/witness bunch system, the witness bunch can be injected into the ion column with a transverse momentum or initial radial offset, so that the whole bunch oscillates about the column axis as one marcro-electron. This results in a larger emitted power and higher photon energy. The energy loss due to radiation can be compensated for by the energy gain from the wakefield so that the emission process can be sustained over long distance. Detailed results will be presented about the characteristics of the witness bunch oscillations and radiation through numerical simulations** and calculations.
* S.Q. Wang, et al., Phys. Rev.Let., 88(13), 135004,(2002), D. K. Johnson et al., Phys. Rev. Lett. 97(17), 175003, (2006)
** C.H. Huang, et al., J. Comp. Phys., 217(2), 658, (2006)
POSTECH, Pohang, Kyungbuk, Republic of Korea
PAL, Pohang, Kyungbuk, Republic of Korea
The X-ray is focused by two zone plates in 1B2 beamline to image electron beam in PLS. From numerical study, we can determine the optical limit of resolution with the same specifications of Fresnel zone plates in 1B2 beamline. The width of Airy pattern and the outmost width of zone plates are turned out to be not good parameters to determine the resolution of the imaging system with a zone plate. The resolution of the entire imaging system 1B2 beamline will be revealed as 682 nm.
Cockcroft Institute, Warrington, Cheshire, United Kingdom
The University of Liverpool, Liverpool, United Kingdom
The exact determination of the time structure of ever shorter bunches in accelerators and light sources such as for example the X-FEL, the ILC or CLIC is of high importance for the successful operation of these next-generation machines. It is also a key to the optimization of existing scientific infrastructures. The exact measurement of the time structure poses a number of challenges to the beam diagnostics system: The monitors should be non-destructive, easy to maintain and provide time resolutions down to the femtosecond regime. Several DITANET partners are active in this field. This contribution gives examples of the network’s research activities in this area with a focus on the LHC longitudinal density monitor, beam profile monitoring using electro-optics techniques and the exploitation of diffraction radiation for non-invasive diagnostics.
ANL, Argonne, USA
Recently, a grazing-incidence insertion device x-ray beam position monitor (GRID-XBPM) was proposed for the intense x-ray beam from the future APS undulators [*]. By combining the function of limiting aperture with the XBPM, it increases the power-bearing capacity of the XBPM and, at the same time, eliminates the problem of relative alignment of the two critical components in the beamline. Furthermore, by imaging the hard x-ray fluorescence footprint on the collimator, the XBPM is immune to the soft x-ray background, and its accuracy is improved at larger gap settings. In addition to these advantages, the GRID-XBPM can also be implemented to measure center-of-mass of the x-ray fluorescence footprint when pinhole-camera-like optics are used for position readout*. This offers a solution for long-standing XBPM design issues for elliptical undulators, which have a donut-shaped power distribution. In this work, we report design progress for the GRID-XBPM for the high-power elliptically polarized undulator planned for the APS intermediate energy x-ray (IEX) beamline. Computer simulation of its performance and experimental tests from a scale model system will also be presented.
* B.X. Yang, G. Decker, S. H. Lee, and P. Den Hartog, Beam Instrumentation Workshop, Santa Fe, 2010, to be published.
BNL, Upton, Long Island, New York, USA
Rogue mode RF shielding has been successfully designed and implemented into the production multipole vacuum chambers. In order to avoid systematic errors in the NSLS-II BPM system we introduced frequency shift of HOM's by using RF metal shielding located in the antechamber slot of each multipole vacuum chamber. To satisfy the pumping requirement the face of the shielding has been perforated with roughly 50 percent transparency. It stays clear of synchrotron radiation in each chamber.
BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
The use of fluorescent screens for beam profile monitors provides a simple and widely used way to obtain detailed two dimensional intensity maps. For high precision measurements many possible error contributions need to be considered that have to do with properties of the fluorescent screens and of the CCDs. Saturation effects, reflections within and outside the screen, non-linearities, radiation damage, etc are often mentioned. Here we concentrate on an error source less commonly described, namely erroneous baseline subtraction, which is particularly important when fitting projected images. We show computer simulations as well as measurement results having remarkable sensitivity of the fitted profile widths to even partial suppression of the profile baseline data, which often arises from large pixel-to-pixel variations at low intensity levels. Such inadvertent baseline data suppression is very easy to miss as it is usually not obvious when inspecting projected profiles. In this report we illustrate this effect and discuss possible algorithms to automate the detection of this problem as well as some possible corrective measures.
Fermilab, Batavia, USA
Beam-profile diagnostics are being developed for a superconducting (SC) radiofrequency (RF) Test Accelerator that is currently under construction at the New Muon Lab (NML) at Fermilab. The facility’s design goals include the replication of the pulse train proscribed for the International Linear Collider (ILC). An RF photoelectric gun based on the DESY design will generate the beam. In test-beam mode a low-power beam will be characterized with intercepting radiation converter screens: either a 100-micron thick YAG:Ce single crystal scintillator or a 1-micron thin Al optical transition radiation (OTR) foil. This prototype station was constructed by RadiaBeam Technologies under a contract with Fermilab. In both cases the screen surface was normal to the beam direction followed by a downstream 45-degree mirror that directed the radiation into the optical system. The optical system has better than 20 (10) micron rms spatial resolution when covering a vertical field of view of 18(5) mm. These initial tests were performed at the A0 Photoinjector at a beam energy of ~15 MeV and with micropulse charges from 25 to 500 pC for beam sizes of 45 to 250 microns. Example results will be presented.
Fermilab, Batavia, USA
SLAC, Menlo Park, California, USA
USC, Los Angeles, California, USA
ANL, Argonne, USA
Extension of near-field optical diffraction radiation (ODR) imaging to the 23 GeV beams at the proposed FACET facility at SLAC has been evaluated. The beam- size sensitivity at the 10- to 20- μm σ level based on a simple model will be reported. Polarization effects are also seen to be important and will be discussed. The comparisons to previous experimental results and the modeling results indicate sufficient feasibility for planning of the experiments in the coming year.
SLAC, Menlo Park, California, USA
FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration beginning in summer 2011. The nominal FACET parameters are 23 GeV, 3 nC electron bunches compressed to ~20 μm long and focussed to ~10 μm wide. Characterization of the beam- plasma interaction requires complete knowledge of the incoming beam parameters on a pulse-to- pulse basis. FACET diagnostics include Beam Position Monitors, Toroidal current monitors, X-ray and Cerenkov based energy spectrometers, optical transition radiation (OTR) profile monitors and coherent transition radiation (CTR) bunch length measurement systems. The compliment of beam diagnostics and their expected performance are reviewed.
SINAP, Shanghai, People's Republic of China
ANL, Argonne, USA
SLAC, Menlo Park, California, USA
Electrons scattered by alumina ceramic transverse beam profile monitors inserted in the Advanced Photon Source (APS) booster-to-storage ring (BTS) transfer line are used to generate C ̆erenkov light for calibration of beam loss monitors (BLMs) installed in the Linac Coherent Light Source (LCLS) undulator beamline. In addition, gas bremsstrahlung (GB) photons generated by 7-GeV electrons in the APS sector 35 storage ring straight section are used to create pair-production electrons for measurement and calibration purposes. Both cases are modeled with the particle-matter interaction program MARS. The realized tuning fork geometry of the BLM exhibits regions of greater sensitivity in the radiator. Transverse GB beam scans have provided uniformity and sensitivity data throughout the volume of the radiator. Comparisons between predicted and measured signal strengths and thermoluminescent dosimeter readings are given and shown to be in reasonable agreement.
BNL, Upton, Long Island, New York, USA
The shielding for the NSLS-II storage ring will provide adequate protection for the full injected beam losses in two periods of the ring around the injection point, but the remainder of the ring is shielded for lower losses of <10% top-off injection beam current. This will require a system to insure that beam losses do not exceed these levels for a period of time that could cause excessive radiation exposure outside the shield walls. This beam Loss Control and Monitoring system will have beam loss monitors that will measure where the beam charge is lost around the ring, to warn operators if losses approach the design limits. In order to measure the charge loss quantitatively, we propose measuring the electron component of the shower as beam electrons hit the vacuum chamber wall. This will be done using the Cerenkov light as charged particles transit an ultra-pure fused silica rod placed close to the inner edge of the VC. The length of rod will collect the light from many charged particles of the spread out shower resulting from the small glancing angle of the lost beam particles to the VC wall. The design and measurements results of the prototype Cerenkov BLM will be presented.
RadiaBeam, Santa Monica, USA
Penn State University, University Park, Pennsylvania, USA
ANL, Argonne, USA
Accelerator-based light sources are some of the largest and most successful scientific user facilities in existence, serving tens of thousands of users each year. These important facilities enable research in diverse fields, including biology, pharmaceuticals, energy conservation and production, data storage, and archaeology. In this tutorial, we briefly review the history of accelerator-based light sources. We present an overview of the different types of accelerator-based light sources, including a description of their various operating principles, as well as a discussion of measures of performance. Technical challenges of current and future light sources are also reviewed.
BNL, Upton, Long Island, New York, USA
ANL, Argonne, USA
The Advanced Photon Source (APS) is a third-generation storage-ring-based x-ray source that has been operating for more than 13 years and is enjoying a long period of stable, reliable operation. While APS is presently providing state-of-the-art performance to its large user community, we must plan for improvements and upgrades to stay at the forefront scientifically. Significant improvements should be possible through upgrades of beamline optics, detectors, and end-station equipment. In this paper, we discuss the evolutionary changes that are envisioned for the storage ring itself. These include short-pulse x-rays, long straight sections, superconducting undulators, improved beam stability, and higher current. With these and other changes, we anticipate significant improvements in capacity, flux, and brightness, along with the ability to perform unique time-resolved experiments.
SLAC, Menlo Park, California, USA
We discuss the properties of the coherent electromagnetic fields of a very short, ultra-relativistic bunch in a rectangular vacuum chamber inside a bending magnet. The analysis is based on the results of a direct numerical solution of Maxwell’s equations together with Newton’s equations. We use a new dispersion-free time-domain algorithm which employs a more efficient use of finite element mesh techniques and hence produces self-consistent and stable solutions for very short bunches. We investigate the fine structure of the CSR fields including coherent edge radiation. This approach should be useful in the study of existing and future concepts of particle accelerators and ultrafast coherent light sources.
BNL, Upton, Long Island, New York, USA
There is a need for an Optics-Free FEL Oscillators (OFFELO) to further the advantages of free-electron lasers and turning them in fully coherent light sources. While SASE (Self-Amplified Spontaneous Emission) FELs demonstrated the capability of providing very high gain and short pulses of radiation and scalability to the Xray range, the spectra of SASE FELs remains rather wide (~0.5%-1%) compared with typical short wavelengths FEL-oscillators (0.01% - 0.0003% in OK-4 FEL). Absence of good optics in VUV and X-ray ranges makes traditional oscillator schemes with very high average and peak spectral brightness either very complex or, strictly speaking, impossible. In this paper, we discuss lattice of the X-ray optics-free FEL oscillator and present results of initial computer simulations of the feedback process and the evolution of FEL spectrum in X-ray OFFELO. We also discuss main limiting factors and feasibility of X-ray OFFELO.
RRCAT, Indore (M.P.), India
Fermilab, Batavia, USA
Homi Bhbha National Institute (HBNI), DAE, Mumbai, India
BNL, Upton, Long Island, New York, USA
FRIB, East Lansing, Michigan, USA
The coils of the first quadrupole in the fragment separator region of the Facility for Rare Isotope Beams (FRIB) must withstand an intense level of radiation and accommodate a very high heat load. Magnets produced with High Temperature Superconductors (HTS) are especially suitable in such an environment. The proposed design employs second generation (2G) HTS, permitting operation at ~50K. The engineering considerations this design are summarized. The goal has been to engineer a compact, readily producible magnet with a warm bore and yoke, made from radiation-resistant materials, capable of operating within the heat load limit, whose four double-layered coils will be adequately restrained under high radial Lorentz forces. Results of ANSYS finite element thermal and structural analyses of the coil clamping system are presented. Coil winding, lead routing and splicing, magnet assembly as well as remote tunnel installation/removal considerations are factored into this design and will also be discussed.
BNL, Upton, Long Island, New York, USA
This paper will describe design, construction and test results of a cryo-mechanical structure to study coils made with the second generation High Temperature Superconductor (HTS) for the Facility for Rare Isotope Beams (FRIB). A magnet comprised of HTS coils mounted in a vacuum vessel and conduction-cooled with Gifford-McMahon cycle cryocoolers is used to develop and refine design and construction techniques. The study of these techniques and their effect on operations provides a better understanding of the use of cryogen free magnets in future accelerator projects. A cryogen-free, superconducting HTS magnet possesses certain operational advantages over cryogenically cooled, low temperature superconducting magnets.
BNL, Upton, Long Island, New York, USA
In the Facility for Rare Isotope Beams (FRIB), superconducting magnets will be exposed to high levels of ionizing radiation. Quadruples in the fragment separator will be exposed to radiation doses as high as ~20 MGy/yr and heat loads as high as ~10 kW/m. High temperature superconducting (HTS) tapes are good candidates for this magnet because they can be operated in the temperature range ~30-50 K to tolerate higher temperatures than low temperature superconductors. Thus, radiation damage studies of HTS tapes are crucial to ensure that they will perform satisfactorily in such a high radiation environment. Therefore, the effects of proton irradiation on second generation HTS tapes from two vendors were studied. Each sample of HTS tape from SuperPower and American Superconductor was irradiated by a 42μA, 142 MeV proton beam at the Brookhaven Linac Isotope Producer. Two of each were irradiated at 5 dose levels: 2.5, 25, 50, 75 and 100μA•hr. The angular dependence of the critical current was measured in a magnetic field at 77K. Based on these measurements, conductors from both vendors appear to satisfy the FRIB radiation-tolerance requirement of 10 years of operation.
LBNL, Berkeley, California, USA
The Muon Ionization Cooling Experiment (MICE) is an international effort sited at Rutherford Appleton Laboratory (RAL) in the UK that will demonstrate ionization cooling in a section of realistic cooling channel using a muon beam. The spectrometer solenoids are an identical pair of five-coil superconducting magnets that will provide a 4-tesla uniform field region at each end of the cooling channel. Scintillating fiber trackers within each of the 400-mm diameter magnet bore tubes will measure the emittance of the beam as it enters and exits the cooling channel. Each of the 3-meter long magnets incorporates a three-coil spectrometer magnet section and a two-coil section that matches the solenoid uniform field into the MICE cooling channel. The cold mass, radiation shield and leads are kept cold by means of a series of two-stage cryocoolers and one single-stage cryocooler. Various thermal, electrical and magnetic analyses are being carried out in order to develop design improvements related to magnet cooling and reliability. The key features of the spectrometer solenoid magnets are presented along with some of the details of the analyses.
Particle Beam Lasers, Inc., Northridge, California, USA
BNL, Upton, Long Island, New York, USA
UCLA, Los Angeles, California, USA
For a muon collider with copious decay particles in the plane of the storage ring, open-midplane dipoles (OMD) may be preferable to tungsten-shielded cosine-theta dipoles of large aperture. The OMD should have its midplane completely free of material, so as to dodge the radiation from decaying muons. Analysis funded by a Phase I SBIR suggests that a field of 10-20 T should be feasible, with homogeneity of 1x10-4 and energy deposition low enough for conduction cooling to 4.2 K helium. If funded, a Phase II SBIR would refine the analysis and build and test a proof-of-principle magnet.
NSRRC, Hsinchu, Taiwan
BNL, Upton, Long Island, New York, USA
A vertical facility has been constructed to test SRF cavities and can be utilized for other use. The liquid helium volume for the large vertical dewar is approximate 84 inches tall by 40 inches diameter with a working clear inner diameter of 38 inch with the inner cold magnetic shield system installed. For radiation enclosure, the test dewar is situated inside a concrete block structure. The structure is above ground and is accessible from the top, and has a retractable concrete roof. A second radiation concrete facility, with ground level access via a labyrinth is also available for testing of smaller cavities in 2 smaller dewars.
BNL, Upton, Long Island, New York, USA
National Synchrotron Light Source II (NSLS-II), being constructed at Brookhaven National Laboratory, is a 3- GeV, high-flux and high-brightness synchrotron radiation facility with a nominal current of 500 mA. The storage ring vacuum system has extruded aluminium chambers, with ante-chamber for photon fans and distributed NEG strip pumping. Discrete photon absorbers are used to intercept the un-used bending magnet radiation. In-situ bakeout is implemented to achieve fast conditioning during initial commissioning and after interventions.
CLASSE, Ithaca, New York, USA
Carleton University, College of Natural Sciences, Ottawa, Ontario, Canada
Measuring the secondary electron yield (SEY) on technical surfaces in accelerator vacuum systems provides essential information for the study of electron cloud growth and suppression, with application to many accelerator R&D projects. As a part of the CesrTA research program, we developed and deployed an in-situ SEY measurement system. A two-sample SEY system was installed in the CesrTA vacuum system with one sample exposed to direct synchrotron radiation (SR) and the other sample exposed to scattered SR. The SEYs of both samples were measured as a function of the SR dosages. In this paper, we describe the in-situ SEY measurement systems and the initial results on bare aluminum (6061-T6), TiN-coated aluminum, amorphous carbon-coated aluminum, and amorphous carbon-coated copper samples.
Advanced Design Consulting, Inc, Lansing, New York, USA
MAX-lab, Lund, Sweden
ANL, Argonne, USA
HSRC, Higashi-Hiroshima, Japan
A new electromagnetic insertion device optimized for producing intense soft x-rays of variable polarization is under construction at the Advanced Photon Source. Most of the coil packs are powered by a main power supply; a few are powered separately so that magnetic fields at certain pole positions can be different. The undulator radiation depends sensitively on the chosen magnetic field pattern, and higher spectral harmonics may be shifted in energy. For some beamline experiments, it is important to reduce the so-called higher-order contamination to increase the signal-to-noise ratio. We present spectra and power densities calculated directly from realistic magnetic fields and discuss coil energizing patterns.
Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
ANL, Argonne, USA
This paper compares calculated on-axis fields for short- period superconducting undulators (SCUs) using Nb3Sn superconductor with two different insulation thicknesses, 0.02 mm and 0.05 mm. When the insulated conductor diameter remained the same, the on-axis fields using the thinner insulation were higher by about 8 – 15% for a period range of 15 – 10 mm. When the conductor diameters with the thicker insulation were made larger than the conductors with the thinner insulation, the differences were reduced to be about 6 – 12%.
CLASSE, Ithaca, New York, USA
We describe the design of optimized undulator with SC windings able to generate the magnetic field of opposite helicities, including an elliptic and a linear ones oriented as desired. For the undulator period 25mm and aperture 8mm, K factor could be changed from zero up to 1.5 by changing the feeding current. Polarization changed by changing the currents in additional helical windings.
BNL, Upton, Long Island, New York, USA
UMD, College Park, Maryland, USA
JLAB, Newport News, Virginia, USA
Beam halo is a challenging issue for intense beams since it can cause beam loss, emittance growth, nuclear activation and secondary electron emission. Because of the potentially low number of particles in the halo compared with beam core, traditional imaging methods may not have sufficient contrast to detect faint halos. We have developed a high dynamic range, adaptive masking method to measure halo using a digital micro-mirror array device and demonstrated its effectiveness experimentally on the University of Maryland Electron Ring (UMER). We also report on similar experiments currently in progress at the Jefferson Lab Free Electron Laser (FEL) using this method.
Uni HH, Hamburg, Germany
DESY, Hamburg, Germany
PSI, Villigen, Switzerland
LBNL, Berkeley, California, USA
Fermilab, Batavia, USA
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
BNL, Upton, Long Island, New York, USA
CUNY, Bayside, New York, USA
UMD, College Park, Maryland, USA
CLASSE, Ithaca, New York, USA
LBNL, Berkeley, California, USA
CalPoly, San Luis Obispo, California, USA
Measurements of coherent tune shifts at the Cornell Electron Storage Ring Test Accelerator (CesrTA) have been made for electron and positron beams under a wide variety of beam energies, bunch charge, and bunch train configurations. Comparing the observed tunes with the predictions of several electron cloud simulation programs allows the evaluation of important parameters in these models. These simulations will be used to predict the behavior of the electron cloud in damping rings for future linear colliders. We outline recent improvements to the analysis techniques that should improve the fidelity of the modeling.
SLAC, Menlo Park, California, USA
CLS, Saskatoon, Saskatchewan, Canada
Theory predicts that CSR in storage rings should appear in whispering gallery modes *, which are resonances of the entire vacuum chamber and are characterized by their high frequencies and concentration of the field near the outer wall of the chamber. The theory assumes that the chamber is a smooth circular torus. We observe that a power spectrum from the NSLS-VUV ring **, which has a vacuum chamber in bends like that of the model, shows a series of sharp peaks with frequencies close to those of the theory. Sharp peaks are also seen in highly resolved spectra at the Canadian Light Source***, and those are invariant in position under large changes in the machine setup (energy, fill pattern, bunch length, CSR bursting or steady, optical beam line, etc.). Invariance of the spectrum suggests that it is due to resonances like whispering gallery modes, but they must be strongly perturbed from the circular case because of large outer wall excursions at the two IR ports.
* R. L. Warnock and P. Morton, Part. Accel. 25, 113 (1990).
** G. L. Carr et al., Proc. PAC 2001, Chicago.
*** T. May et al., IEEE 33rd Intl. Conf. IR Millimeter and THz Waves, 2008.
USC, Los Angeles, California, USA
BNL, Upton, Long Island, New York, USA
LANL, Los Alamos, New Mexico, USA
IPFN, Lisbon, Portugal
UCLA, Los Angeles, California, USA
Current Filamentation Instability, CFI, is of central importance for the propagation of relativistic electron beams in plasmas. CFI could play an important role in the generation of magnetic fields and radiation in the after-glow of gamma ray bursts and also in energy transport for the fast-igniter inertial confinement fusion concept. Simulations were conducted with the particle-in-cell code QuickPIC* for e- beam and plasma parameters at the Brookhaven National Laboratory – Accelerator Test Facility, BNL-ATF. Results show that for a 2cm plasma the instability reaches near saturation. An experimental program was proposed and accepted at the BNL-ATF and an experiment is currently underway. There are three components to the experimental program: 1) imaging of the beam density/filaments at the exit from the plasma, 2) measurement and imaging of the transverse plasma density gradient and measurement of the magnetic field and 3) identifying the radiation spectrum of the instability. Preliminary results from phase one will be presented along with the progress and diagnostic design for the following phases of the experiment.
* C. Huang et. al. Journal of Computational Physics 217, 2(2006)
BNL, Upton, Long Island, New York, USA
A number of recent machine designs, including ‘‘nano-beams'', sub-millimeter ‘‘low-beta'' IRs, etc., require high accuracy on beam orbit and beam size, reliable evaluation of machine parameters, dynamic apertures, etc. This can only be achieved using high precision simulation tools. Stepwise ray-tracing methods are in this category of tools, stochastic synchrotron radiation and its effects on an electron beam in a storage ring are simulated here in that manner. Benchmarking of the method against analytical model expectations, using a Chasman-Green cell, is presented.
Tomsk State University, Tomsk, Russia
Institute of High Current Electronics, Tomsk, Russia
CLASSE, Ithaca, New York, USA
LPI, Moscow, Russia
We calculate the coherent radiation in an undulator/wiggler with a vacuum chamber of arbitrary cross section. The backward radiation is a coherent and it has wavelengths about twice the period of the undulator/wiggler. Mostly of coherent radiation is going with the wavelengths approximately the bunch length at small angles however.
LLNL, Livermore, California, USA
NPS, Monterey, California, USA
The Naval Postgraduate School (NPS), Niowave, Inc., and Boeing have recently demonstrated operation of the first superconducting RF electron gun based on a quarter wave resonator structure. In preliminary tests, this gun has produced 10 ps-long bunches with charge in excess of 78 pC, and with beam energy up to 396 keV. Initial testing occurred at Niowave's Lansing, MI, facility, but the gun and its diagnostic beamline are planned for installation at NPS in the near future. The design of the diagnostic beamline is conducive to the addition of a Cerenkov radiator without interfering with other beamline operations. Design and simulations of a Cerenkov radiator, consisting of a dielectric lined waveguide will be presented. The dispersion relation for the structure is determined and the beam interaction is studied using numerical simulations. The characteristics of the microwave radiation produced in both the long and short bunch regimes will be examined.
UCLA, Los Angeles, California, USA
Injection of electron beams into laser driven picosecond scale accelerating structures demand highly synchronized electron beams with bunch lengths approaching the femtosecond scale. One-dimensional numerical studies of undulator interactions of 3.5 MeV sub-picosecond electron beams and THz pulse trains produced by optical rectification have shown substantial compression and a reduction in time of arrival jitter with respect to the accelerator drive laser from the scale of hundreds of fs to that of tens of fs. In this paper a THz undulator based compression and synchronization scheme is investigated.
Siemens AG, Healthcare Technology and Concepts, Erlangen, Germany
Siemens AG, Erlangen, Germany
* Heid O., Hughes T. THPD002, IPAC10, Kyoto, Japan
** Hergt M et al, 2010 IEEE International Power Modulator and High Voltage Conf., Atlanta GA, USA
*** Heid O., Hughes T. THP068, LINAC10, Tsukuba, Japan
RadiaBeam, Santa Monica, USA
PSI, Villigen, Switzerland
University of Pune, Pune, India
SAMEER, Mumbai, India
BNL, Upton, Long Island, New York, USA
We are presenting the layout and the optics of a beam line to be used as a medical gantry in radiation therapy. The optical properties of the gantry’s beam line are such as to make the beam line achromatic and uncoupled. These two properties make the beam spot size, which is delivered and focused by the gantry, on the tumor of the patient, independent of the angular orientation of the gantry. In this paper we present the layout of the magnetic elements of the gantry, and also present the theoretical basis for the optics design of such a gantry.
* N. Tsoupas et. al. “Uncoupled achromatic tilted S-bend” Presented at the 11th Biennial European Particle Accelerator Conference, Genoa, Italy, June 23-27,2008
University of Pune, Pune, India
Shivaji University, Nanomaterials Reasearch Laboratory, Kolhapur, India
USTC/NSRL, Hefei, Anhui, People's Republic of China
LANL, Los Alamos, New Mexico, USA
Fermilab, Batavia, USA
Fermilab, Batavia, USA
Requirements and operating conditions for a Muon Collider Ring (MCR) pose significant challenges to superconducting magnets. The dipole magnets should provide a high magnetic field to reduce the ring circumference and thus maximize the number of muon collisions during their lifetime. One third of the beam energy is continuously deposited along the lattice by the decay electrons at the rate of 0.5 kW/m for a 1.5-TeV c.o.m. MCR. Unlike dipoles in proton machines, the MCR dipoles should allow this dynamic heat load to escape the magnet helium volume in horizontal plane predominantly towards the ring center. Two alternative designs, one based on the open mid-plane approach with block type coils and absorber outside the coils, and another based on the traditional large-aperture cos-theta approach with a shifted beam pipe and absorber inside the coil aperture were developed for the MCR designed for a luminosity of 1034 cm-2s−1. This paper presents the analysis and comparison of radiation effects in MCR based on the two dipole magnets. Tungsten masks in the interconnect regions are used in both cases to mitigate the unprecedented dynamic heat deposition and radiation in the magnet coils.
BNL, Upton, Long Island, New York, USA
It has been speculated that the beam may cause instability of the RHIC Beam Abort Kickers. In this study, we explore the available data of past beam operations, the device history of key modulator components, and the radiation patterns to examine the correlations.
ANL, Argonne, USA
The Advanced Photon Source is planning [*] to produce a short-pulse x-ray beam by way of rf deflecting cavities that locally impose a y'-t correlation on the stored beam at an insertion device. SPring-8 recently proposed [**] a variation on this scheme whereby the deflecting cavities impose a local y-t correlation on the stored beam. In one case the chirp is in the angle coordinate and in the other case the position coordinate. They both use slits to pass through a "short" portion of the photon beam. The practical limitations for the two schemes are discussed and compared, such as photon source size and angular divergence, storage ring apertures, and slit transmission.
* A. Nassiri et al., these proceedings
** T. Fujita et al., Proc. of IPAC10, p. 39
ANL, Argonne, USA
The laser slicing technique* has been successfully applied at several low- to medium-energy storage ring light sources to create sub-picosecond pulses of x-rays. Application to high-energy storage rings has been considered problematic because of the required average laser power. However, because of on going advances in laser technology, this technique is now within reach at light sources like the Advanced Photon Source (APS), which operates at 7 GeV. In this paper, we analyze the potential performance of laser slicing at the APS, and compare it to alternatives such as deflecting cavities.
* R. W. Schoenlien et al., Science, 287, 2237(2000).
SLAC, Menlo Park, California, USA
INFN/LNF, Frascati (Roma), Italy
HZB, Berlin, Germany
CLASSE, Ithaca, New York, USA
Hard x-ray Energy Recovery Linacs (ERLs) operate with high-brightness electron beams, matching the requirements for X-ray FELs in terms of emittance and energy spread. We have analyzed in how far it is feasible to include X-ray FELs in ERL facilities. X-ray FEL Oscillators require comparatively low peak currents and are therefore good candidates for FEL sources in ERLs. However, also high-gain FELs do not seem out of reach when bunch-compression schemes for higher peak currents are utilized. Using the proposed Cornell ERL as an example, different FEL concepts are discussed and their suitability as X-ray sources are analyzed.
USTC/NSRL, Hefei, Anhui, People's Republic of China
SLAC, Menlo Park, California, USA
BNL, Upton, Long Island, New York, USA
* T. Watanabe et al, Phys. Rev. Lett. 98, 034802 (2007).
** X.J. Wang et al, Phys. Rev. Lett. 103, 154801 (2009).
BNL, Upton, Long Island, New York, USA
We show that the paraxial field equation for a free electron laser (FEL) in an infinitely wide electron beam with a kappa-2 energy distribution can be reduced to a fourth ordinary differential equation (ODE). Its solution for arbitrary initial phase space density modulation has been derived in the wave-vector domain. For initial current modulation with Gaussian profile, close form solutions are obtained in space-time domain.
PKU/IHIP, Beijing, People's Republic of China
FEL/Duke University, Durham, North Carolina, USA
A well-calibrated spectrometer is critical for measuring the real spectra of spontaneous radiation of an electron beam in undulators (i.e. undulator radiation), which is important for FEL research. A calibration method of spectrometers based upon the known undulator radiation spectrum has been developed at Duke FEL Laboratory (DFELL). It has been used to provide a precise calibration for spectrometers from infrared (IR) to ultraviolet (UV). This calibration method is expected to be useful for the calibration of spectrometers working in the extreme ultraviolet (EUV) and X-ray region. In this work, we present the details of the calibration method and illustrate the usefulness of the method using a portable spectrometer in the visible region as an example.
FEL/Duke University, Durham, North Carolina, USA
The Duke FEL and High Intensity Gamma-ray Source (HIγS) are operated in the range of electron beam energies of 0.24 - 1.2 GeV and photon beam wavelengths of 190-1060 nm. The range of gamma-beam energies currently produced by HIγS facility is from 1MeV to about 100 MeV, with the maximum total gamma-flux of up to 3*1010 gammas per second around 10 MeV. Production of this high level gamma-ray flux requires an average FEL photon beam power inside the FEL resonator at one kilowatt or more. The high power FEL operation causes degradation of the FEL mirrors, especially when operating the FEL in the UV and VUV region at a high electron beam energy. To ensure reliable HIγS operation, we developed a comprehensive program to continuously monitor the performance of the FEL mirrors. This program enabled us to use a particular set of FEL mirrors for a few hundreds hours of high gamma-flux operation with predictable performance. In this work, we discuss sources and consequences of the mirror degradation for a variety of wavelengths. We also present estimates of the mirror life time as a function of the FEL wavelength, photon and gamma-ray polarization, and total gamma-flux.
SLAC, Menlo Park, California, USA
* D. Xiang et al., "Demonstration of the Echo-Enabled Harmonic Generation Technique for Short-Wavelength Seeded Free Electron Lasers", PRL 105, 114801, 2010.
UCB, Berkeley, California, USA
UESTC, Chengdu, Sichuan, People's Republic of China
LBNL, Berkeley, California, USA
The possibility of implementing echo-enabled harmonic generation* (EEHG) within a single optical resonance cavity is explored both analytically and with numerical simulations. Two modulators of the same frequency are used so that the cavity radiation replaces the two seed lasers of conventional EEHG. Such a scheme has potential** to produce tunable radiation as in EEHG, but with the high repetition rate, longitudinal coherence, and narrow spectral bandwidth of an oscillator. These benefits, however, come with the complication that the beam must generate the radiation that modulates it. Analysis and GINGER simulations are presented for a specific example that takes advantage of robust multilayer mirror performance at 13.4 nm to produce radiation near or possibly even below 1 nm.
* G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009).
** J. Wurtele et al., Proc. of the 2010 FEL Conference, TUOC12.
LLNL, Livermore, California, USA
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.