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Title: The FFAG return loop for the CBETA Energy Recovery Linac

Abstract

The CBETA energy recovery linac uses a single xed eld alternating gradient (FFAG) beam line to return the beam for electron beams with four energies, ranging from 42 MeV to 150 MeV. To keep the beam line compact, the ends of the return line have a small radius of curvature, but the central part of the return line is straight. These are connected by transition lines that adiabatically change from one to the other. We rst describe the design or the arc cell. We then describe how a straight cell is created to be a good match to this arc cell. We then describe the design of the transition line between them. The design process makes use of eld maps for the desired magnets. Because we switch magnet types as we move from the arc, through the transition, and into the straight, there are discrete jumps in the elds that degrade the adiabaticity of the transition, and we describe corrections to manage that.

Authors:
 [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1412722
Report Number(s):
BNL-114546-2017-IR
DOE Contract Number:
SC0012704
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Berg, J. S. The FFAG return loop for the CBETA Energy Recovery Linac. United States: N. p., 2017. Web. doi:10.2172/1412722.
Berg, J. S. The FFAG return loop for the CBETA Energy Recovery Linac. United States. doi:10.2172/1412722.
Berg, J. S. Fri . "The FFAG return loop for the CBETA Energy Recovery Linac". United States. doi:10.2172/1412722. https://www.osti.gov/servlets/purl/1412722.
@article{osti_1412722,
title = {The FFAG return loop for the CBETA Energy Recovery Linac},
author = {Berg, J. S.},
abstractNote = {The CBETA energy recovery linac uses a single xed eld alternating gradient (FFAG) beam line to return the beam for electron beams with four energies, ranging from 42 MeV to 150 MeV. To keep the beam line compact, the ends of the return line have a small radius of curvature, but the central part of the return line is straight. These are connected by transition lines that adiabatically change from one to the other. We rst describe the design or the arc cell. We then describe how a straight cell is created to be a good match to this arc cell. We then describe the design of the transition line between them. The design process makes use of eld maps for the desired magnets. Because we switch magnet types as we move from the arc, through the transition, and into the straight, there are discrete jumps in the elds that degrade the adiabaticity of the transition, and we describe corrections to manage that.},
doi = {10.2172/1412722},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Apr 28 00:00:00 EDT 2017},
month = {Fri Apr 28 00:00:00 EDT 2017}
}

Technical Report:

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  • The Cornell-Brookhaven Energy-Recovery-Linac Test Accelerator (CBETA) will provide a 150-MeV electron beam using four acceleration and four deceleration passes through the Cornell Main Linac Cryomodule housing six 1.3-GHz superconducting RF cavities. The return path of this 76-m-circumference accelerator will be provided by 106 fixed-field alternating-gradient (FFAG) cells which carry the four beams of 42, 78, 114 and 150 MeV. Here we describe magnet designs for the splitter and combiner regions which serve to match the on-axis linac beam to the off-axis beams in the FFAG cells, providing the path-length adjustment necessary to energy recovery for each of the four beams.more » The path lengths of the four beamlines in each of the splitter and combiner regions are designed to be adapted to 1-, 2-, 3-, and 4-pass staged operations. Design specifi- cations and modeling for the 24 dipole and 32 quadrupole electromagnets in each region are presented. The CBETA project will serve as the first demonstration of multi-pass energy recovery using superconducting RF cavities with FFAG cell optics for the return loop.« less
  • The Cornell-BNL Electron Test Accelerator (CBETA), a 150 MeV energy recovery linac (ERL) now in construction at Cornell, employs a fixed-field alternating gradient optics return loop: a single beam line comprised of FFAG cells, which accepts four recirculated energies. CBETA FFAG cell uses Halbach permanent magnet technology, its design studies have covered an extended period of time supported by extensive particle dynamics simulations using computed 3-D field map models. As a result, this approach is discussed, and illustrated here, based on the final stage in these beam dynamics studies, namely the validation of a ultimate, optimized design of the Halbachmore » cell.« less
  • Workshop on Photo-injectors for Energy Recovery Linac was held at National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory (BNL) on January 22 and 23, 2001. Fifty people attended the workshop; they came from three countries, representing universities, industries and national laboratories. This is the first workshop ever held on photo-injectors for CW operation, and for the first time, both DC and RF photo-injectors were discussed at the workshop. Workshop covered almost all major issues of photo-injectors, photocathode, laser system, vacuum, DC, 433 MHz/B-factory cavities based RF gun, 1.3 GHz RF gun and beam instrumentation. High quantum efficiency and longmore » live time photocathode is the issue discussed during the workshop. Four working group leaders have done great jobs summarizing the workshop discussion, and identifying the major issues for future R and D.« less
  • Understanding the prevalence and structure of higher-order modes (HOMs) in accelerator cavities is critical because their excitation can result in problematic single bunch and multi-bunch effects. Particularly hazardous are dipole modes, which are more easily excited due to their linear field nature near the beam center. During a recent superconducting test on the energy recovery linac (ERL) cavity at Brookhaven National Laboratory (BNL), 8 of the highest-Q HOMs were measured for the first time. In conjunction with analysis of CST Microwave Studio simulation results for the ERL model, one of these modes was further studied in the copper prototype ERLmore » cavity. A method of identifying HOMs utilizing existing holes drilled in copper cavity cells was developed and used to conclude that the observed high-Q mode was a quadrupole.« less