PAC07 - List of Authors (Qiang, J.)

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Qiang, J.

Paper	Title	Page
TUPMN116	Numerical Study of Coulomb Scattering Effects on Electron Beam from a Nano-tip	1185
	J. Qiang A. Adelmann PSI, Villigen J. N. Corlett, S. M. Lidia, H. A. Padmore, W. Wan, A. Zholents, M. S. Zolotorev LBNL, Berkeley, California
	Funding: This work was supported by the U. S. Department of Energy under Contract no. DE-AC02-05CH11231. Nano-tips with high acceleration gradient around the emission surface have been proposed to generate high brightness beams. However, due to the small size of the tip, the charge density near the tip is very high even for a small number of electrons. The Coulomb scattering near the tip can significantly degrade the beam quality and cause extra emittance growth and energy spread. In the paper, we present a numerical study of these effects using a direct relativistic N-body model. We found that emittance growth and energy spread, due to Coulomb scattering, can be significantly enhanced with respect to mean-field space-charge calculations in different parameter regimes.
FRPMS025	Streak Camera Temporal Resolution Improvement Using a Time-Dependent Field	3973
	J. Qiang J. M. Byrd, J. Feng, G. Huang LBNL, Berkeley, California
	Funding: This work was supported by the U. S. Department of Energy under Contract no. DE-AC02-05CH11231. Streak camera is an important diagnostic device in the studies of laser plasma interaction, the detailed structure of photo reaction from material science to biochemistry, and in the measurement of the longitudinal distribution of a beam in accelerators. In this paper, we report on a new method which can potentially improve the temporal resolution of a streak camera down to femtoseconds. This method uses a time-dependent acceleration field to defocus the photo electrons longitudinally. This not only reduces the time dispersion distortion caused by initial energy spread but also mitigates the effects from the space-charge forces. An illustration of the method shows significant improvement of the modulation transfer function (MFT) compared with the conventional design.
FRPMS026	Strong-Strong Simulation of Long-Range Beam-Beam Effects at RHIC	3979
	J. Qiang W. Fischer BNL, Upton, Long Island, New York T. Sen Fermilab, Batavia, Illinois
	Funding: This work was supported by the U. S. Department of Energy under Contract no. DE-AC02-05CH11231. Long-range beam-beam interactions can cause significant degrade of beam quality and lifetime in high energy ring colliders. At RHIC, a series of experiments were carried out to study these effects. In this paper, we report on numerical simulation of the long-range beam-beam interactions at RHIC using a parallel strong-strong particle-in-cell code, BeamBeam3D. The simulation includes nonlinearities from both the beam-beam interactions and the arc sextupoles. We observed significant emittance growth for beam separation below 4 σs under nominal tunes. A scan study in tune space shows strong emittance growth around 7th order resonance. Including the tune modulation due to chromaticity and synchrotron motion shows larger emittance growth than the case without the tune modulation.
TUOBAB01	Beam Dynamics of the 250 MeV Injector Test Facility	785
	A. Adelmann R. J. Bakker, C. Kraus, K. L. Li, B. S.C. Oswald, M. Pedrozzi, J.-Y. Raguin, T. Schietinger, F. Stulle, A. F. Wrulich PSI, Villigen J. Qiang LBNL, Berkeley, California
	The PSI-FEL/LEG project aims for the development of a pulsed high-brightness, high-current electron source which is one of the cornerstones for a cost-efficient high-power laser-like X-ray light-source. Creating an ultra low emittance beam is a great challenge, transporting i.e. accelerating and compressing is equally difficult. We present a 3D start-to-end simulation of our planned 250 MeV injector test facility. The injector consists of a 2 cell standing wave l-band cavity followed by a ballistic bunching section. The following L-band and S-band structures accelerate the electron beam up to the final energy of 250 MeV. An X-band RF structure prepares the beam for the following bunch compressor in which the target current of 350 ampere is reached. The target value of the slice emittance is 0.10 [mm mrad] therefore precise beam dynamics simulations are needed. For the 3D simulations we use IMPACT-T, a time domain parallel particle tracking code in which the self fields are treated using electrostatic approximation . We discuss various issues such as projected and slice emittance preservation and shade light on some of the differences between an envelope and the 3D model.
	Slides
TUZBC02	SciDAC Frameworks and Solvers for Multi-physics Beam Dynamics Simulations	894
	J. F. Amundson D. R. Dechow Tech-X, Boulder, Colorado J. Qiang, R. D. Ryne LBNL, Berkeley, California P. Spentzouris Fermilab, Batavia, Illinois
	The need for realistic accelerator simulations is greater than ever before due to the needs of design projects such as the ILC and optimization for existing machines. Sophisticated codes utilizing large-scale parallel computing have been developed to study collective beam effects such as space charge, electron cloud, beam-beam, etc. We will describe recent advances in the solvers for these effects and plans for enhancing them in the future. To date the codes have typically applied to a single collective effect and included just enough of the single-particle dynamics to support the collective effect at hand. We describe how we are developing a framework for realistic multi-physics simulations, i.e., simulations including the state-of-the-art calculations of all relevant physical processes.
	Slides
TUODC02	Development of 3D Beam-Beam Simulation for the Tevatron	905
	E. G. Stern J. F. Amundson, P. Spentzouris, A. Valishev Fermilab, Batavia, Illinois J. Qiang, R. D. Ryne LBNL, Berkeley, California
	We present status of development of a 3D Beam-Beam simulation code. The essential features of the code are 3D particle-in-cell Poisson solver, multi-bunch beam transport and interaction, chromaticity and machine impedance. The simulations match synchro-betatron oscillations measured at the VEPP-2M collider. The impedance model is compared to analytic expressions for instability growth.
	Slides
TUPMN109	A High Repetition Rate VUV-Soft X-Ray FEL Concept	1167
	J. N. Corlett J. M. Byrd, W. M. Fawley, M. Gullans, D. Li, S. M. Lidia, H. A. Padmore, G. Penn, I. V. Pogorelov, J. Qiang, D. Robin, F. Sannibale, J. W. Staples, C. Steier, M. Venturini, S. P. Virostek, W. Wan, R. P. Wells, R. B. Wilcox, J. S. Wurtele, A. Zholents LBNL, Berkeley, California
	Funding: This work was supported by the Director, Office of Science, High Energy Physics, U. S. Department of Energy under Contract No. DE-AC02-05CH11231. The FEL process increases radiation flux by several orders of magnitude above existing incoherent sources, and offers the additional enhancements attainable by optical manipulations of the electron beam: control of the temporal duration and bandwidth of the coherent output, and wavelength; utilization of harmonics to attain shorter wavelengths; and precise synchronization of the x-ray pulse with laser systems. We describe an FEL facility concept based on a high repetition rate RF photocathode gun, that would allow simultaneous operation of multiple independent FELs, each producing high average brightness, tunable over the soft x-ray-VUV range, and each with individual performance characteristics determined by the configuration of the FEL SASE, enhanced-SASE (ESASE), seeded, self-seeded, harmonic generation, and other configurations making use of optical manipulations of the electron beam may be employed, providing a wide range of photon beam properties to meet varied user demands. FELs would be tailored to specific experimental needs, including production of ultrafast pulses even into the attosecond domain, and high temporal coherence (i.e. high resolving power) beams.
TUPMN114	Simulation of the Microbunching Instability in Beam Delivery Systems for Free Electron Lasers	1179
	I. V. Pogorelov J. Qiang, R. D. Ryne, M. Venturini, A. Zholents LBNL, Berkeley, California R. L. Warnock SLAC, Menlo Park, California
	In this paper, we examine the growth of the microbunching instability in the chain of linac sections and bunch compressor chicanes used in the electron beam delivery system of a free electron laser. We compare the results of two sets of simulations, one conducted using a direct Vlasov solver, the other using a particle-in-cell code Impact-Z with the number of simulation macroparticles ranging up to 100 million. The comparison is focused on the values of uncorrelated (slice) energy spread at different points in the lattice. In particular, we discuss the interplay between physical and numerical noise in particle-based simulations, and assess the agreement between the simulation results and theoretical predictions.
TUPAS095	Experiments with a DC Wire in RHIC	1859
	W. Fischer N. P. Abreu, R. Calaga, G. Robert-Demolaize BNL, Upton, Long Island, New York U. Dorda, J.-P. Koutchouk, F. Zimmermann CERN, Geneva A. C. Kabel SLAC, Menlo Park, California H. J. Kim, T. Sen Fermilab, Batavia, Illinois J. Qiang LBNL, Berkeley, California
	Funding: Work supported by U. S. DOE under contract No DE-AC02-98CH1-886. A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanying simulations.
THPMN117	Design of a VHF-band RF Photoinjector with MegaHertz Beam Repetition Rate	2990
	J. W. Staples K. M. Baptiste, J. N. Corlett, S. Kwiatkowski, S. M. Lidia, J. Qiang, F. Sannibale, K. G. Sonnad, S. P. Virostek, R. P. Wells LBNL, Berkeley, California
	Funding: This work is supported by the Director, Office of Science, High Energy Physics, U. S. Dept. of Energy under Contract no. DE-AC02-05CH1121 New generation accelerator-based X-ray light sources require high quality beams with high average brightness. Normal conducting L- and S-band photoinjectors are limited in repetition rate and D-C (photo)injectors are limited in field strength at the cathode. We propose a low frequency normal-conducting cavity, operating at 50 to 100 MHz CW, to provide beam bunches at a rate of one MegaHertz or more. The photoinjector uses a re-entrant cavity structure, requiring less than 100 kW CW, with a peak wall power density less than 10 W/cm². The cavity will support a vacuum down to 10 picoTorr, with a load-lock mechanism for easy replacement of photocathodes. The photocathode can be embedded in a magnetic field to provide correlations useful for flat beam generation. Beam dynamics simulations indicate that normalized emittances on the order of 1 mm-mrad are possible with gap voltage of 750 kV, with fields up to 20 MV/m at the photocathode, for 1 nanocoulomb charge per bunch after acceleration and emittance compensation. Long-bunch operation (10's of picosecond) is made possible by the low cavity frequency, permitting low bunch current at the 750 kV gap voltage.
THPAS007	Parallel Beam Dynamics Simulation Tools for Future Light Source Linac Modeling	3522
	R. D. Ryne I. V. Pogorelov, J. Qiang LBNL, Berkeley, California
	Large-scale modeling on parallel computers is playing an increasingly important role in the design of future light sources. Such modeling provides a means to accurately and efficiently explore issues such as limits to beam brightness, emittance preservation, the growth of instabilities, etc. Recently the IMPACT codes suite was enhanced to be applicable to future light source design. Early simulations with IMPACT-Z were performed using up to 100M simulation particles for the main linac of a future light source. Combined with the time domain code IMPACT-T, it is now possible to perform large-scale start-to-end linac simulations for future sources, including the injector, main linac, chicanes, and transfer lines. In this paper we provide an overview of the IMPACT code suite, its key capabilities, and recent enhancements pertinent to accelerator modeling for future linac-based light sources.
THPAS015	Three-Dimensional Integrated Green Functions for the Poisson Equation	3546
	D. T. Abell P. J. Mullowney, K. Paul, V. H. Ranjbar Tech-X, Boulder, Colorado J. Qiang, R. D. Ryne LBNL, Berkeley, California
	Funding: Supported by US DOE Office of Science: Offices of Nuclear Physics, grant DE-FG02-03ER83796; High Energy Physics; and Advanced Scientific Computing Research, SciDAC Accelerator Science and Technology. The standard implementation of using FFTs to solve the Poisson equation with open boundary conditions on a Cartesian grid loses accuracy when the change in G rho (the product of the Green function and the charge density) over a mesh cell becomes nonlinear; this is commonly encountered in high aspect ratio situations and results in poor efficiency due to the need for a very large number of grid points. A modification which solves this problem, the integrated Green function (IGF), has been implemented in two dimensions using linear basis functions and in three dimensions using constant basis functions. But, until recently, it has proved to be very difficult to implement IGF in three dimensions using linear basis functions. Recently significant progress has been made. We present both the implementation and test results for the three-dimensional extension.
THPAS051	The RIAPMTQ/IMPACT Beam-Dynamics Simulation Package	3606
	T. P. Wangler V. N. Aseev, B. Mustapha, P. N. Ostroumov ANL, Argonne, Illinois J. H. Billen, R. W. Garnett LANL, Los Alamos, New Mexico K. R. Crandall TechSource, Santa Fe, New Mexico M. Doleans, D. Gorelov, X. Wu, R. C. York, Q. Zhao NSCL, East Lansing, Michigan J. Qiang, R. D. Ryne LBNL, Berkeley, California
	Funding: This work is supported by the U. S. Department of Energy, DOE contract number:W-7405-ENG-36 RIAPMTQ/IMPACT is a pair of linked beam-dynamics simulation codes that have been developed for end-to-end computer simulations of multiple-charge state heavy-ion linacs for future exotic-beam facilities. The simulations can extend from the low-energy beam transport after the ECR source to the end of the linac. The work has been performed by a collaboration including LANL, LBNL, ANL, MSU, and TechSource. The code RIAPMTQ simulates the linac front end including the LEBT, RFQ, and MEBT, and the code IMPACT simulates the main superconducting linac. The codes have been benchmarked for rms beam properties against previously existing codes at ANL and MSU. The codes allow high-statistics runs on parallel supercomputing platforms, such as NERSC at LBNL, as well as runs on desktop PC computers for low-statistics design work. We will show results from 10-million-particle simulations of RIA designs by ANL and MSU, carried out at the NERSC facility. These simulation codes will allow evaluations of candidate designs with respect to beam-dynamics performance including beam losses.
THPAS060	LCLS Beam Dynamics Studies with the 3-D Parallel Impact-T Code	3624
	Y. T. Ding Z. Huang, C. Limborg-Deprey SLAC, Menlo Park, California J. Qiang LBNL, Berkeley, California
	In 2007, the Linac Coherent Light Source (LCLS) will start to commission the photoinjector, the linacs (up to 250 MeV) and the first bunch compressor (BC1). In this paper, we report on the beam dynamics studies in this low-energy part of the machine with the parallel Impact-T code, taking into account three-dimensional (3-D) space charge forces, linac wakefields, and coherent synchrotron radiation. We compare the IMPACT-T simulation results with PARMELA and discuss possible space charge effects in the linac and BC1 regions. We also plan to compare with experimental measurements when they become available. J. Qiang et al, Phys. Rev. ST Accel. Beams 9,044204 (2006).
FRPMS022	Progress on Modeling of Ultrafast X-Ray Streak Cameras	3961
	G. Huang J. M. Byrd, J. Feng, J. Qiang, W. Wan LBNL, Berkeley, California
	Streak cameras continue to be useful tools for studying ultra phenomena on the sub-picosecond time scale and beyond. We have employed accelerator modeling tools to understand the key parts of the streak camera in order to improve the time resolution. This effort has resulted in an start-to-end model of the camera including a dedicated 3D modeling of time-dependent fields. This model has contributed to the recent achievement of 230 fsec (FWHM) resolution measured using 266 nm laserat the Advanced Light Source Streak Camera Laboratory. We will report on our model and its comparison with experiments. We also extrapolate the performance of this camera including several possible improvements.
FRPMS032	High-Order Modeling of an ERL for Electron Cooling in the RHIC Luminosity Upgrade using MaryLie/IMPACT	4000
	V. H. Ranjbar D. T. Abell, K. Paul Tech-X, Boulder, Colorado I. Ben-Zvi, J. Kewisch BNL, Upton, Long Island, New York J. Qiang, R. D. Ryne LBNL, Berkeley, California
	Funding: Work supported by the U. S. DOE Office of Science, Office of Nuclear Physics under grant DE-FG02-03ER83796. Plans for the RHIC luminosity upgrade call for an electron cooling system that will place substantial demands on the energy, current, brightness, and beam quality of the electron beam. In particular, the requirements demand a new level of fidelity in beam dynamics simulations. New developments in MaryLie/IMPACT have improved the space-charge computations for beams with large aspect ratios and the beam dynamic computations for rf cavities. We present the results of beam dynamics simulations that include the effects of space charge and nonlinearities, and aim to assess the tolerance for errors and nonlinearities on current designs for a super-conducting ERL.