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HIGH POWER TEST OF RF SEPARATOR FOR 12 GEV UPGRADE OF CEBAF AT JLAB

Description: CEBAF at JLab is in the process of an energy upgrade from 6 GeV to 12 GeV. The existing setup of the RF separator cavities in the 5th pass will not be adequate to extract the highest energy (11 GeV) beam to any two existing halls (A, B or C) while simultaneously delivering to the new hall D in the case of the proposed 12 GeV upgrade of the machine. To restore this capability, we are exploring the possibility of extension of existing normal conducting 499 MHz TEM-type rf separator cavities. Detailed numerical studies suggest that six 2-cell normal conducting structures meet the requirements; each 2-cell structure will require up to 4 kW RF input power in contrast with the current nominal operating power of 1.0 to 2.0 kW. A high power test of 4 kW confirms that the cavity meet the requirement.
Date: July 1, 2012
Creator: Ahmed, S.; Wissmann, M.; Mammosser, J.; Hovater, C.; Spata, M.; Krafft, G. et al.
Partner: UNT Libraries Government Documents Department

The N* Program at CEBAF

Description: The N* program at CEBAF is reviewed, and some preliminary experimental results are presented to illustrate the quality and capabilities of the CLAS detector.
Date: December 1, 1998
Creator: Minehart, Ralph
Partner: UNT Libraries Government Documents Department

Device control at CEBAF

Description: CEBAF has undergone a major conversion of its accelerator control system from TACL to EPICS, affecting device control for the RF system, magnets, the machine protection system, the vacuum and valves, and the diagnostic systems including beam position monitors, harps, and the camera and solenoid devices (beam viewers, faraday cups, optical transition radiation viewers, synchrotron radiation monitor, etc.). Altogether these devices require approximately 125,000 EPICS database records. The majority of these devices are controlled through CAMAC; some use embedded microprocessors (RF and magnets), and newer interfaces are in VME. The standard EPICS toolkit was extended to include a driver for CAMAC which supports dual processors on one serial highway, custom database records for magnets and BPMs, and custom data acquisition tasks for the BPMs. 2 refs., 1 tab.
Date: August 1, 1996
Creator: Schaffner, S.; Barker, D. & Bookwalter, V.
Partner: UNT Libraries Government Documents Department

Looking Back at International Synchrotron Radiation Instrumentation

Description: With the 11th International Synchrotron Radiation Instrumentation coming up in July 2012 in Lyons, France, we thought it might be of interest to our readers to review all the past meetings in this series. We thank Denny Mills of the APS, Argonne for putting the list together. Prior to these larger meetings, and in the early days, facilities held their own meetings similar to the user meetings of today. However, the meeting held at ACO in Orsay, France in 1977 was the first such meeting with an international flavor and so it is on the list. However it is not counted as number 1 since it was agreed way back to start the numbering with the 1982 DESY meeting. The 2005 USA National Meeting scheduled at CAMD in Baton Rouge had to be canceled due to Hurricane Katrina. It was ultimately held in 2007, with the CLS hosted meeting the following year. And a personal note from the magazine - Synchrotron Radiation News was born at the 1987 meeting in Madison, Wisconsin with a proposal that was put to a special session of the meeting organized by Susan Lord. Initial proposals were to model it after the CERN Courier, but it soon adopted its own distinct flavor.
Date: March 1, 2012
Creator: Williams, Gwyn
Partner: UNT Libraries Government Documents Department

12 GeV Upgrade Project - Cryomodule Production

Description: The Thomas Jefferson National Accelerator Facility (Jefferson Lab) is producing ten 100+MV SRF cryomodules (C100) as part of the CEBAF 12 GeV Upgrade Project. Once installed, these cryomodules will become part of an integrated accelerator system upgrade that will result in doubling the energy of the CEBAF machine from 6 to 12 GeV. This paper will present a complete overview of the C100 cryomodule production process. The C100 cryomodule was designed to have the major components procured from private industry and assembled together at Jefferson Lab. In addition to measuring the integrated component performance, the performance of the individual components is verified prior to being released for production and assembly into a cryomodule. Following a comprehensive cold acceptance test of all subsystems, the completed C100 cryomodules are installed and commissioned in the CEBAF machine in preparation of accelerator operations. This overview of the cryomodule production process will include all principal performance measurements, acceptance criterion and up to date status of current activities.
Date: July 1, 2012
Creator: J. Hogan, A. Burrill, G.K. Davis, M.A. Drury, M. Wiseman
Partner: UNT Libraries Government Documents Department

HIGH AVERAGE POWER UV FREE ELECTRON LASER EXPERIMENTS AT JLAB

Description: Having produced 14 kW of average power at {approx}2 microns, JLAB has shifted its focus to the ultraviolet portion of the spectrum. This presentation will describe the JLab UV Demo FEL, present specifics of its driver ERL, and discuss the latest experimental results from FEL experiments and machine operations.
Date: July 1, 2012
Creator: Douglas, David; Evtushenko, Pavel; Gubeli, Joseph; Hernandez-Garcia, Carlos; Legg, Robert; Neil, George et al.
Partner: UNT Libraries Government Documents Department

Chromatic Correction in the CEBAF Beam Transport System

Description: The CEBAF accelerator beam transport system contains 104 sextupoles to correct chromatic aberrations. We describe the layout of these elements and discuss schemes for suppressing chromatic errors. Analytic results for the required sextupole strengths are given and computations of chromatic aberrations are documented. Numerical results using two correction methods are provided.
Date: May 1, 1991
Creator: Douglas, David
Partner: UNT Libraries Government Documents Department

CEBAF Control System

Description: A logic-based computer control system is in development at CEBAF. This Unix/C language software package, running on a distributed, hierarchical system of workstation and supervisory minicomputers, interfaces to hardware via CAMAC. Software aspects to be covered are ladder logic, interactive database generation, networking, and graphic user interfaces.
Date: October 1, 1988
Creator: Bork, Rolf; Lahti, George; Navarro, Edwin; Grubb, Caroline; Sage, Joan & Moore, T.
Partner: UNT Libraries Government Documents Department

Two Dimensional Simulations of Multipass Beam Breakup

Description: A vectorized two dimensional beam breakup code, TDBBU, is used to simulate bunch dynamics in recirculating accelerators. First, the code is briefly described, including effects needed to accurately model the CEBAF accelerator. Next, various code test are sketched. Finally, the multipass beam breakup threshold current is determined to be from 10-20 mA for the CEBAF accelerator, a result in agreement with other calculations of the threshold current.
Date: March 1, 1987
Creator: Krafft, Geoffrey & Bisognano, Joseph
Partner: UNT Libraries Government Documents Department

LEP and CEBAF Polarimeters

Description: This paper gives an overview on high energy electron (positron) polarimeters by describing in more detail the plans for the LEP polarimeter and the CEBAF polarimeters. Both LEP and CEBAF will have laser polarimeters. In addition CEBAF will be equipped with a Moller polarimeter (for currents below 1 micro-amp).
Date: September 1, 1988
Creator: Rossmanith, Robert; Burkert, Volker & Placidi, Massimo
Partner: UNT Libraries Government Documents Department

Industrial Development of Cornell Superconducting Cavities for CEBAF

Description: Properties of the Cornell five-cell superconducting accelerating cavity and the suitability of this cavity for the CEBAF linac are discussed.The advanced technology required to produce these cavities was already known to some companies and is being transferred to others.The status of development of these cavities by industry, including test results on three of these cavities is discussed.
Date: January 1, 1986
Creator: Palussek, A.; Heidt, Albert; Chargin, Anthony; Matheissen, Axel; Moss, Barry; Reece, Charles et al.
Partner: UNT Libraries Government Documents Department

DIMAD Based Interactive Simulation of the CEBAF Accelerator

Description: An X-Windows^(TM) based interactive interface to the DIMAD beam optics program enables users to simulate the adjustment of magnets in tuning various segments of the CEBAF beamline.In addition, users can track the effects of random errors on the path of individual particles as magnets are adjusted.The interface sits on top of the standard DIMAD model, retaining the detailed modeling available with that code.Because X-Windows software was used, the code is portable to any system that has X-Windows and the X-Windows Toolkit available.We give results from the studies simulating the extraction portion of the CEBAF beamline.
Date: May 1, 1991
Creator: Douglas, David & Bickley, Matthew
Partner: UNT Libraries Government Documents Department

Orbit Correction Techniques for a Multipass Linac

Description: The CEBAF accelerator includes a linac section which accelerates multiple beams with different energies. Problems arise when performing orbit correction, due to the fact that correction of higher energy passes disturb lower energy trajectories. Therefore, a perfect orbit correction cannot be obtained for all energy beams at the same time.\nWe present methods and performance (using simulation results) for performing orbit corrections in such a system. Limitations to the correction methods are also addressed.\n
Date: September 1, 1990
Creator: Barry, Andrea; Bowling, Bruce & Kewisch, Jorg
Partner: UNT Libraries Government Documents Department

Quasi two-body decays of nonstrange baryons.

Description: We examine the decays of nonstrange baryons to the final states Delta Pi, NRho, NEta, NEta', Nw, N.5 (1440)Pi, and Delta 3/2+(1600)Pi, in a relativized pair-creation (^3Po) model which has been developed in a previous study of the NPi decays of the same baryon states.As it is our goal to provide a guide for the possible discovery of new baryon states at CEBAF and elsewhere, we examine the decays of resonances which have already been seen in the partial-wave analyses, along with those of states which are predicted by the quark model but which remain undiscovered.The level of agreement between our calculation and the available widths from the partial-wave analyses in encouraging.
Date: August 1, 1993
Creator: Roberts, Winston & Capstick, Simon
Partner: UNT Libraries Government Documents Department

CEBAF: The Continuous Electron Beam Accelerator Facility and its Physics Program

Description: With the 4 GeV Continuous Electron Beam Accelerator Facility presently under construction in Newport News, Virginia, a new domain of nuclear and subnuclear phenomena can be investigated, mainly through coincidence experiments. An overview of the characteristic features of the accelerator and associated experimental equipment is given. Some examples of the physics programs are briefly described.
Date: January 1, 1992
Creator: Mougey, Jean
Partner: UNT Libraries Government Documents Department

The polarized SRF gun experiment

Description: An experiment is under way to prove the feasibility of a super-conducting RF gun for the production of polarized electrons. We report on the progress of the experiment and on simulations predicting the possibility of success.
Date: October 1, 2008
Creator: Kewisch,J.; Ben-Zvi, I.; Rao, T.; Burrill, A.; Pate, D.; Todd, R. et al.
Partner: UNT Libraries Government Documents Department

Performance experience with the CEBAF SRF cavities

Description: The full complement of 169 pairs of niobium superconducting cavities has been installed in the CEBAF accelerator. This paper surveys the performance characteristics of these cavities in vertical tests, commissioning in the tunnel, and operational experience to date. Although installed performance exceeds specifications, and 3.2 GeV beam has been delivered on target, present systems do not consistently preserve the high performance obtained in vertical dewar tests as operational capability. Principal sources of these limitations are discussed.
Date: December 31, 1995
Creator: Reece, C.; Benesch, J.; Drury, M.; Hovater, C.; Mammosser, J. & Preble, J.
Partner: UNT Libraries Government Documents Department

Measurement of G

Description: The ratio of the electric and magnetic form factors of the proton, G{sub E{sub p}}/G{sub M{sub p}}, was measured at the Thomas Jefferson National Accelerator Facility (JLab) using the recoil polarization technique. The ratio of the form factors is directly proportional to the ratio of the transverse to longitudinal components of the polarization of the recoil proton in the elastic {rvec e}p {yields} e{rvec p} reaction. The new data presented in this article span the range 3.5 < Q{sup 2} < 5.6 GeV{sup 2} and are well described by a linear Q{sup 2} fit. Also, the ratio QF{sub 2p}/F{sub 1p} reaches a constant value above Q{sup 2}=2 GeV{sup 2}.
Date: March 1, 2002
Creator: Gayou, Olivier; Brash, Ed J.; Jones, Mark K.; Perdrisat, Charles F.; Punjabi, Vina; Pentchev, L. et al.
Partner: UNT Libraries Government Documents Department

Light meson radial Regge trajectories

Description: A new physical mechanism is suggested to explain the universal depletion of high meson excitations. It takes into account the appearance of holes inside the string world sheet due to q{bar q} pair creation when the length of the string exceeds the critical value R{sub 1} {approx_equal} 1.4 fm. It is argued that a delicate balance between large N{sub c} loop suppression and a favorable gain in the action, produced by holes, creates a new metastable (predecay) stage with a renormalized string tension which now depends on the separation r. This results in smaller values of the slope of the radial Regge trajectories, in good agreement with the analysis of experimental data in references.
Date: August 1, 2002
Creator: Badalian, A.M.; Bakke, B.L.G. & Simonov, Yu.A.
Partner: UNT Libraries Government Documents Department