Merminga, L.

Paper	Title	Page
MOYCH02	Physics Challenges for ERL Light Sources	16
	L. Merminga Jefferson Lab, Newport News, Virginia
	We present an overview of the physics challenges encountered in the design and operation of Energy Recovering Linac (ERL) based light sources. These challenges include the generation and preservation of low emittance, high-average current beams, manipulating and preserving the transverse and longitudinal phase space, control of the multipass beam breakup instability, efficient extraction of higher order mode power and RF control and stability of the superconducting cavities. These key R&D issues drive the design and technology choices for proposed ERL light sources. Simulations and calculations of these processes will be presented and compared with experimental data obtained at the Jefferson Lab FEL Upgrade, a 10 mA ERL light source presently in commissioning, and during a 1 GeV demonstration of energy recovery at CEBAF.
	Video of talk
	Transparencies
MOPKF087	The Cebaf Energy Recovery Experiment: Update and Future Plans	524
	A. Freyberger, K. Beard, S.A. Bogacz, Y.-C. Chao, S. Chattopadhyay, D. Douglas, A. Hutton, L. Merminga, C. Tennant, M. Tiefenback Jefferson Lab, Newport News, Virginia
	A successful GeV scale energy recovery demonstration with a high ratio of peak-to-injection energies (50:1) was carried out on the CEBAF (Continuous Electron Beam Accelerator Facility) recirculating superconducting linear accelerator in the spring 2003. To gain a quantitative understanding of the beam behavior through the machine, data was taken to characterize the 6D phase space during the CEBAF-ER (CEBAF with Energy Recovery) experimental run. The transverse emittance and energy spread of the accelerating and energy recovered beams were measured in several locations to ascertain the beam quality preservation during energy recovery. Measurements also included the RF system's response to the energy recovery process and transverse beam profile of the energy recovered beam. One of the salient conclusions from the experiment is that the energy recovery process does not contribute significantly to the emittance degradation. The current status of the data analysis will be presented as well as plans for a GeV scale energy recovery experimental run with current doubling.
MOPLT153	Electron-Ion Collider at CEBAF: New Insights and Conceptual Progress	893
	Y.S. Derbenev, A. Afanasev, K. Beard, S.A. Bogacz, P. Degtiarenko, J.R. Delayen, A. Hutton, G.A. Krafft, R. Li, L. Merminga, M. Poelker, B.C. Yunn, Y. Zhang Jefferson Lab, Newport News, Virginia P.N. Ostroumov ANL/Phys, Argonne, Illinois
	We report on progress in conceptual development of the proposed high luminosity (up to 1035/cm2s) and efficient spin manipulation (using figure 8 boosters and collider rings) Electron-Ion Collider at CEBAF based on use of polarized 5-7 GeV electrons in superconduction energy recovering linac (ERL with circulator ring, kicker-operated) and 30-150 GeV ion storage ring (polarized p, d. He3, Li and unpolarized nuclei up to Ar, all totally stripped). Ultra-high luminosity is envisioned to be achievable with short ion bunches and crab-crossing at 1.5 GHz bunch collision rate interaction points. Our recent studies concentrated on simulation of beam-beam interaction, preventing the electron cloud instability, calculating luminosity lifetime due to Touschek effect in ion beam and background scattering of ions, experiments on energy recovery at CEBAF, and other. These studies have been incorporated in the development of the luminosity calculator and in formulating minimum requirements to the polarized electron and ion sources
TUPKF068	JLAB Hurricane Recovery	1102
	A. Hutton, D. Arenius, F.J. Benesch, S. Chattopadhyay, E. Daly, V. Ganni, O. Garza, R. Kazimi, R. Lauze, L. Merminga, W. Merz, R. Nelson, W. Oren, M. Poelker, T. Powers, J.P. Preble, C. Reece, R.A. Rimmer, M. Spata, S. Suhring Jefferson Lab, Newport News, Virginia
	Hurricane Isabel, originally a Category 5 storm, arrived at Jefferson Lab on September 18 with winds of only 75 mph creating little direct damage to the infrastructure. However, electric power was lost for four days allowing the superconducting cryomodules to warm up and causing a total loss of the liquid helium. The subsequent recovery of the cryomodules and the impact of the considerable amount of opportunistic preventive maintenance provides important lessons for all accelerators complexes, not only those with superconducting elements. The details of how the recovery process was structured and the resulting improvement in accelerator availability will be discussed in detail.
TUPLT164	CEBAF Injector Achieved World's Best Beam Quality for Three Simultaneous Beams with a Wide Range of Bunch Charges	1512
	R. Kazimi, K. Beard, F.J. Benesch, A. Freyberger, J.M. Grames, T. Hiatt, A. Hutton, G.A. Krafft, L. Merminga, M. Poelker, M. Spata, M. Tiefenback, B.C. Yunn, Y. Zhang Jefferson Lab, Newport News, Virginia
	The CEBAF accelerator simultaneously provides three 499 MHz interleaved continuous electron beams spanning 5 decades in beam intensity (a few nA to 200 uA) to three experimental halls. The typical three-user physics program became more challenging when a new experiment, G0, was approved for more than six times higher bunch charge than is routine. The G0 experiment requires up to 8 million electrons per bunch (at a reduced repetition rate of 31 MHz) while the lowest current hall operates at 100 electrons per bunch simultaneously. This means a bunch destined to one hall may experience significant space charge forces while the next bunch, for another hall, is well below the space charge limit. This disparity in beam intensity is to be attained while maintaining best ever values in the beam quality, including final relative energy spread (<2.5x 10-5 rms) and transverse emittance (<1 mm-mrad norm. rms). The difficulties related to space charge emerge in the 10m long, 100 keV section of the CEBAF injector during initial beam production and acceleration. A series of changes were introduced in the CEBAF injector to meet the new requirements, including changes in the injector setup, adding new magnets, replacing lasers used for the photocathode and modifying typical laser parameters, stabilizing RF systems, and changes to standard operating procedures. In this paper, we will discuss all these modifications in some detail including the excellent agreement between the experimental results and detailed simulations. We will also present some of our operational results.
TUPLT165	A PARMELA Model of the CEBAF Injector valid over a Wide Range of Parameters	1515
	Y. Zhang, K. Beard, F.J. Benesch, Y.-C. Chao, A. Freyberger, J.M. Grames, R. Kazimi, G.A. Krafft, R. Li, L. Merminga, M. Poelker, M. Tiefenback, B.C. Yunn Jefferson Lab, Newport News, Virginia
	A pre-existing PARMELA model of the CEBAF injector has been recently verified using machine survey data and also extended to 60 MeV region. The initial distribution and temperature of an electron bunch are determined by the photocathode laser spot size and emittance measurements. The improved injector model has been used for extensive computer simulations of the simultaneous delivery of the Hall A beam required for a hypernuclear experiment, and the Hall C beam, required for a parity experiment. The Hall C beam requires a factor of 6 higher bunch charge than the Hall A beam, with significantly increased space charge effects, while the Hall A beam has an exceedingly stringent energy spread requirement of 2.5x 10-5 rms. Measurements of the beam properties of both beams at several energies (100 keV, 500 keV, 5 MeV, 60 MeV) and several values of the bunch charge were performed using the standard quad-wire scanner technique. Comparisons of simulated particle transmission rate, longitudinal beam size, transverse emittance and twiss parameters, and energy spread against experimental data yield reasonably good agreement. The model is being used for searching for optimal setting of the CEBAF injector.
TUPLT163	Achieving Beam Quality Requirements for Parity Experiments at Jefferson Lab	1509
	Y.-C. Chao, H. Areti, F.J. Benesch, B. Bevins, S.A. Bogacz, S. Chattopadhyay, J.M. Grames, J. Hansknecht, A. Hutton, R. Kazimi, L. Merminga, M. Poelker, Y. Roblin, M. Tiefenback Jefferson Lab, Newport News, Virginia D. Armstrong The College of William and Mary, Williamsburg D. Beck, K. Nakahara University of Illinois, Urbana K. Paschke University of Massachusetts, Amherst M. Pitt Virginia Polytechnic Institute and State University, Blacksburg
	Measurement of asymmetry between alternating opposite electron polarization in electron-nucleon scattering experiments can answer important questions about nucleon structures. Such experiments impose stringent condition on the electron beam quality, and thus the accelerator used for beam creation and delivery. Of particular concern to such ?parity? experiments is the level of correlation between beam characteristics (orbit, intensity) and electron polarization that can obscure the real asymmetry. This can be introduced at the beam forming stage, created due to scraping, or not damped to desired level due to defective transport. Suppression of such correlation thus demands tight control of the beam line from cathode to target, and requires multi-disciplined approach with collaboration among nuclear physicists and accelerator physicists/engineers. The approach adopted at Jefferson Lab includes reduction of correlation source, improving low energy beam handling, and monitoring and correcting global transport. This paper will discuss methods adopted to meet the performance criteria imposed by parity experiments, and ongoing research aimed at going beyond current performance.