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Title: Optimization of the RF cavity heat load and trip rates for CEBAF at 12 GeV

Abstract

The Continuous Electron Beam Accelerator Facility at JLab has 200 RF cavities in the north linac and the south linac respectively after the 12 GeV upgrade. The purpose of this work is to simultaneously optimize the heat load and the trip rate for the cavities and to reconstruct the pareto-optimal front in a timely manner when some of the cavities are turned down. By choosing an efficient optimizer and strategically creating the initial gradients, the pareto-optimal front for no more than 15 cavities down can be re-established within 20 seconds.

Authors:
 [1];  [1];  [1];  [1];  [2]
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  2. Old Dominion Univ., Norfolk, VA (United States)
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1375770
Report Number(s):
JLAB-ACP-17-2473; DOE/OR/23177-4145
DOE Contract Number:
AC05-06OR23177
Resource Type:
Conference
Resource Relation:
Conference: IPAC 2017, Copenhagen, Denmark, May 14-19, 2017
Country of Publication:
United States
Language:
English

Citation Formats

Zhang, He, Roblin, Yves R., Freyberger, Arne P., Krafft, Geoffrey A., and Terzic, Balsa P. Optimization of the RF cavity heat load and trip rates for CEBAF at 12 GeV. United States: N. p., 2017. Web. doi:10.18429/JACoW-IPAC2017-MOPVA133.
Zhang, He, Roblin, Yves R., Freyberger, Arne P., Krafft, Geoffrey A., & Terzic, Balsa P. Optimization of the RF cavity heat load and trip rates for CEBAF at 12 GeV. United States. doi:10.18429/JACoW-IPAC2017-MOPVA133.
Zhang, He, Roblin, Yves R., Freyberger, Arne P., Krafft, Geoffrey A., and Terzic, Balsa P. Mon . "Optimization of the RF cavity heat load and trip rates for CEBAF at 12 GeV". United States. doi:10.18429/JACoW-IPAC2017-MOPVA133. https://www.osti.gov/servlets/purl/1375770.
@article{osti_1375770,
title = {Optimization of the RF cavity heat load and trip rates for CEBAF at 12 GeV},
author = {Zhang, He and Roblin, Yves R. and Freyberger, Arne P. and Krafft, Geoffrey A. and Terzic, Balsa P.},
abstractNote = {The Continuous Electron Beam Accelerator Facility at JLab has 200 RF cavities in the north linac and the south linac respectively after the 12 GeV upgrade. The purpose of this work is to simultaneously optimize the heat load and the trip rate for the cavities and to reconstruct the pareto-optimal front in a timely manner when some of the cavities are turned down. By choosing an efficient optimizer and strategically creating the initial gradients, the pareto-optimal front for no more than 15 cavities down can be re-established within 20 seconds.},
doi = {10.18429/JACoW-IPAC2017-MOPVA133},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon May 01 00:00:00 EDT 2017},
month = {Mon May 01 00:00:00 EDT 2017}
}

Conference:
Other availability
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  • In this paper, a genetic algorithm-based optimization is used to simultaneously minimize two competing objectives guiding the operation of the Jefferson Lab's Continuous Electron Beam Accelerator Facility linacs: cavity heat load and radio frequency cavity trip rates. The results represent a significant improvement to the standard linac energy management tool and thereby could lead to a more efficient Continuous Electron Beam Accelerator Facility configuration. This study also serves as a proof of principle of how a genetic algorithm can be used for optimizing other linac-based machines.
  • In this paper, a genetic algorithm-based optimization is used to simultaneously minimize two competing objectives guiding the operation of the Jefferson Lab's Continuous Electron Beam Accelerator Facility linacs: cavity heat load and radio frequency cavity trip rates. The results represent a significant improvement to the standard linac energy management tool and thereby could lead to a more efficient Continuous Electron Beam Accelerator Facility configuration. This study also serves as a proof of principle of how a genetic algorithm can be used for optimizing other linac-based machines.
  • Based on initial testing of the “HG” and “LL” 7-cell cavities in the prototype cryomodule Renascence, several opportunities for improved optimization were identified. The HOM damping configuration was refined so as to meet the requirements for damping key dipole modes while simultaneously dramatically reducing risk of HOM pickup probe heating and also creating beamline clearance for mounting the tuner to stainless steel helium vessel endplates (rather than NbTi/Ti transitions to a titanium helium vessel). Code modeling and bench measurements were performed. The new design maintains the 7-cell LL cells and incorporates a brazed transition between Nb and the SS heliummore » vessel. The resulting configuration is now called the “C100” design. Cavity design details as well as vertical dewar and horizontal test bed performance are presented.« less
  • The CEBAF Accelerator at Jefferson Lab presently consists of 50 MeV injector, two anti-parallel superconducting linacs and two arcs for transporting beam between the linacs. By the mid-1990s, the accelerator was providing electrons up to 5.75 GeV. The 12 GeV Upgrade is a major accelerator project aimed at doubling the energy by adding 10 (five per linac) new high gradient cryomodules, each providing 100 MV of field. The new cryomodule will consist of eight 7-cell superconducting cavities operating at an average accelerating gradient of 19.5 MV/m and with an external Q=3.2 x 10^7. The high gradient, very high quality factormore » and large Lorentz detuning coefficient (KL up to 4) pose significant challenges beyond what the present analog low level RF (LLRF) control systems can handle reliably; therefore, a new digital LLRF control system has been developed. The main highlights of the new RF Control system include: a RF front-end with low temperature drift and good linearity, a large FPGA« less
  • 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 conductingmore » 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.« less