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WEPP049 |
Advances on ELIC Design Studies
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2632 |
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- S. A. Bogacz, P. Chevtsov, Y. S. Derbenev, P. Evtushenko, M. Hutton, G. A. Krafft, R. Li, L. Merminga, J. Musson, B. C. Yunn, Y. Zhang
Jefferson Lab, Newport News, Virginia
- J. Qiang
LBNL, Berkeley, California
- H. K. Sayed
Old Dominion University, Norfolk, Virginia
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An electron-ion collider of a center-of-mass energy up to 90 GeV at luminosity up to 1035 cm-2s-1 with both beams highly polarized is essential for exploring the new QCD frontier of strong color fields in nuclear and precisely imaging the sea-quarks and gluons in the nucleon. A conceptual design of a ring-ring collider based on CEBAF (ELIC) with energies up to 9 GeV for electrons/positrons and up to 225 GeV for protons and 100 GeV/u for ions has been proposed to fulfill the science desire and to serve as the next step for CEBAF after the planned 12 GeV energy upgrade of the fixed target program. Here, we summarize recent design progress for the ELIC complex with four interaction points (IP); including interaction region optics with chromatic aberration compensation scheme and complete lattices for the Figure-8 collider rings. Further optimization of crab crossing angles at the IPs, simulations of beam-beam interactions and electron polarization in the Figure-8 ring and its matching at the IPs are also discussed.
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WEPP087 |
Observation and Mitigation of Multipass BBU in CEBAF
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2722 |
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- R. Kazimi, A. Freyberger, C. Hovater, G. A. Krafft, F. Marhauser, T. E. Plawski, C. E. Reece, J. S. Sekutowicz, C. Tennant, M. G. Tiefenback, H. Wang
Jefferson Lab, Newport News, Virginia
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The CEBAF recirculating accelerator at Jefferson Lab consists of two linacs carrying beam for up to five passes of acceleration. The Beam Break-Up (BBU) phenomenon was anticipated during design of the accelerator. The threshold beam current to induce BBU was calculated to be approximately 20 milliamperes, far above operational current. No sign of BBU was ever seen in more than a decade of operation. A specially designed acceleration cavity in a recently installed cryomodule was found to cause a BBU instability under special conditions with as low as 40 uA of injected beam current. This presented an opportunity to study BBU in a five-pass accelerator. In this paper we will discuss multipass BBU, show observational data, and discuss the ways we have developed to maintain the instability threshold current to values above those required for operation.
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