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SLC positron source pulsed flux concentrator

Description: SLC positron beams produced by a high energy electron beam, impinging on a high Z target, have initially small transverse size but large divergence, a situation ill matched to the following S-band accelerator. The flux concentrator is an adiabatic matching device placed between the target and this accelerator, which trades divergence versus size. It produces a magnetic field with a sharp rise over less than 5 mm to its peak value, and then falling off adiabatically over 10 cm. It is a 12 turn, 10 cm long copper coil with a cylindrical outside radius of 4 cm and a conical inside radius growing from 3.5 mm to 2.6 cm. The 0.2 mm gaps between the individual windings were manufactured by electric discharge machining out of one copper block. Excitation current and water cooling is provided by a hollow rectangular copper conductor brazed to the outside of the coil (also 12 turns). The pulsed magnetic field has a maximum strength of 58 kG at 16 kA. At the terminals, the coil has an inductance of 0.8 {mu}H. Current shape is a half sinusoidal wave with a bottom width of 5 {mu}s, and the system operates at a repetition rate of 120 Hz. The coil has only one supporting ceramic insulator at the low voltage front end. The flux concentrator has improved the positron yield approximately 3 times and had no failure in operation during several years. 10 refs., 5 figs.
Date: June 1, 1991
Creator: Kulikov, A.V.; Ecklund, S.D. & Reuter, E.M.
Partner: UNT Libraries Government Documents Department

Isochronous 180 degree turns for the SLC positron system

Description: The design of the compact, achromatic, second order isochronous 180{degrees} turn for the SLC positron transport system will be described. Design criteria require an energy range of 200{plus minus}20 MeV, energy acceptance of {plus minus}5%, transverse admittance of 25{pi} mm-mr, and minimal lengthening of the 3 to 4 mm (rms) positron bunch. The devices had to fit within a maximum height or width of about 10 ft. Optics specifications and theoretical performance are presented and compared to experimental results based on streak camera measurements of bunch length immediately after the first isochronous turn (200 MeV) and positron beam energy spread after S-band acceleration to 1.15 GeV. 5 refs., 7 figs.
Date: May 1, 1991
Creator: Helm, R.H.; Clendenin, J.E.; Ecklund, S.D.; Kulikov, A.V. & Pitthan, R.
Partner: UNT Libraries Government Documents Department

The NLC positron source

Description: A baseline design for the NLC positron source based on the existing SLC positron system is described. The proposed NLC source consists of a dedicated S-band electron accelerator, a conventional positron production and capture system utilizing a high Z target and an adiabatic matching device, and an L-band positron linac. The invariant transverse acceptance of the capture system is 0.06 m{center_dot}rad, ensuring an adequate positron beam intensity for the NLC.
Date: May 1, 1995
Creator: Tang, H.; Kulikov, A.V.; Clendenin, J.E.; Ecklund, S.D. & Miller, R.A.
Partner: UNT Libraries Government Documents Department

Design, analysis and measurement of very fast kicker magnets at SLAC

Description: Recent experience with SLC has shown that very fast, ferrite-loaded, transmission-line, beam-kicker magnets can cause significant and undesirable distortion of a 1.5-2.5 kA, 20-4- kV pulse as it travels through the magnet. In general, there is a net lengthening of the pulse, with increases in its rise and fall times, a decrease in amplitude, and an unsymmetrical rounding of the flattop. In this partially tutorial treatise, a number of practical design considerations are discussed in terms of equivalent circuits, magnet circuit dispersion and dissipation, undesired circuit shunting and coupling, high-voltage breakdown problems and high-order-mode losses that lead to beam tube heating. These effects are linked to the properties of the materials, the presence of radiation and realizable magnet topologies. Measurements and calculations of some of these characteristics for several magnet designs are reviewed. The results presented come from a truly eclectic effort. 8 refs., 1 fig.
Date: March 1, 1989
Creator: Weaver, J.N.; Bowden, G.B.; Bulos, F.; Cassel, R.L.; Donaldson, A.R.; Harvey, A. et al.
Partner: UNT Libraries Government Documents Department

SLC positron source: Simulation and performance

Description: Performance of the source was found to be in good general agreement with computer simulations with S-band acceleration, and where not, the simulations lead to identification of problems, in particular the underestimated impact of linac misalignments due to the 1989 Loma Prieta Earthquake. 13 refs., 7 figs.
Date: June 1, 1991
Creator: Pitthan, R.; Braun, H.; Clendenin, J.E.; Ecklund, S.D.; Helm, R.H.; Kulikov, A.V. et al.
Partner: UNT Libraries Government Documents Department

PEP-II Status and Outlook

Description: PEP-II/BABAR are presently in their second physics run. With machine and detector performance and reliability at an all-time high, almost 51 fb{sup -1} have been integrated by BABAR up to mid-October 2001. PEP-II luminosity has reached 4.4 x 10{sup 33} cm{sup -2} s{sup -1} and our highest monthly delivered luminosity has been above 6 pb{sup -1}, exceeding the performance parameters given in the PEP-II CDR by almost 50%. The increase compared to the first run in 2000 has been achieved by a combination of beam-current increase and beam-size decrease. In this paper we will summarize the PEP-II performance and the present limitations as well as our plans to further increase machine performance.
Date: April 24, 2012
Creator: Wienands, H.U.; Biagini, M.E.; Decker, F.J.; Donald, M.H.; Ecklund, S.; Fisher, A. et al.
Partner: UNT Libraries Government Documents Department

The NLC Injector System

Description: The Next Linear Collider (NW) Injector System is designed to produce low emittance, 10 GeV electron and positron beams at 120 hertz for injection into the NLC main linacs. Each beam consists of a train of 9.5 bunches spaced by 2.8 ns; each bunch has a population of 1.15 x 10{sup 10} particles. At injection into the main linacs, the horizontal and vertical emittances are specified to be {gamma}{var_epsilon}{sub x} = 3 x 10{sup -6} m-rad and {gamma}{var_epsilon}{sub y} = 3 x 10{sup -8} m-rad and the bunch length is 100 {micro}m. Electron polarization of greater than 80% is required. Electron and positron beams are generated in separate accelerator complexes each of which contain the source, damping ring systems, L-band, S-band, and X-band linacs, bunch length compressors, and collimation regions. The need for low technical risk, reliable injector subsystems is a major consideration in the design effort. This paper presents an overview of the NLC injector systems.
Date: November 5, 1999
Creator: Bharadwaj, V.; Clendenin, J.E.; Emma, P.; Frisch, J.; Jobe, R.; Kotseroglou, T. et al.
Partner: UNT Libraries Government Documents Department