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Title: TM 4: Beam through the Main Linac Cryomodule

Abstract

On May 15th 2017, the CBETA project reached the major funding milestone, “Beam through the MLC.” For this test, the team had to successfully accelerate the electron beam to 6 MeV in the Injector Cryomodule (ICM), and then to a final energy of 12 MeV in the Main Linac Cryomodule (MLC). The MLC contains six superconducting accelerating cavities; for this initial test only a single cavity was powered.

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:
1412726
Report Number(s):
BNL-114550-2017-IR
DOE Contract Number:
SC0012704
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Bartnik, A. TM 4: Beam through the Main Linac Cryomodule. United States: N. p., 2017. Web. doi:10.2172/1412726.
Bartnik, A. TM 4: Beam through the Main Linac Cryomodule. United States. doi:10.2172/1412726.
Bartnik, A. Wed . "TM 4: Beam through the Main Linac Cryomodule". United States. doi:10.2172/1412726. https://www.osti.gov/servlets/purl/1412726.
@article{osti_1412726,
title = {TM 4: Beam through the Main Linac Cryomodule},
author = {Bartnik, A.},
abstractNote = {On May 15th 2017, the CBETA project reached the major funding milestone, “Beam through the MLC.” For this test, the team had to successfully accelerate the electron beam to 6 MeV in the Injector Cryomodule (ICM), and then to a final energy of 12 MeV in the Main Linac Cryomodule (MLC). The MLC contains six superconducting accelerating cavities; for this initial test only a single cavity was powered.},
doi = {10.2172/1412726},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jun 14 00:00:00 EDT 2017},
month = {Wed Jun 14 00:00:00 EDT 2017}
}

Technical Report:

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  • Scattering of primary beam electrons off of residual gas molecules or blackbody radiation photons in the NLC main linac has been identified as a potential source of beam haloes which must be collimated in the beam delivery system. We consider the contributions from four scattering mechanisms: inelastic thermal-photon scattering, elastic beam-gas (Coulomb) scattering inelastic beam-gas (Bremsstrahlung) scattering, and atomic-electron scattering. In each case we develop the formalism necessary to estimate the backgrounds generated in the main linac, and determine the expected number of off-energy or large-amplitude particles from each process, assuming a main linac injection energy of 8 GeV andmore » extraction energy of 500 GeV.« less
  • The Next Linear Collider main linacs are 13 km linear accelerators which each contain approximately 750 hybrid iron/permanent-magnet quadrupoles in a FODO array. The small amount of vertical emittance dilution permitted in the main linacs implies a tight tolerance on the RMS distance between the beam and the centers of the quads. We describe two methods for measuring the offsets between the quads and their integrated beam position monitors, and three algorithms for steering the main linac to minimize the emittance dilution. Simulation studies of the alignment and steering algorithms are presented.
  • One of the factors that limited the performance of the Stanford Linear Collider (SLC) was the number of particles per bunch with large betatron or energy amplitudes. We consider the equivalent problem for the Next Linear Collider (NLC) main X-band linacs. We evaluate the number of large-amplitude particles which can be expected due to scattering processes, wakefields, and magnet nonlinearities. We conclude that the number of particles in the beam halo from these sources can easily be accommodated by the planned post-linac collimation system.
  • This is a preliminary study of the effect of using microwave quads (MQ's) instead of rf phase shifting to induce BNS damping in the main linac of the NLC collider. We consider MQ's running at X-band, and find that the total length of MQ's needed for the NLC is 6% of the total length of the accelerating structures. We show through simulations that, by using MQ's instead of phase shifting for BNS damping, the quad alignment tolerances can be relaxed but at the expense of shifting the tight tolerances to the MQ's; this can be advantageous if the MQ's canmore » be better aligned than the quads. For the design final energy spread in the NLC of .3%, the quad tolerances are loosened by a factor of 2-3 when using MQ's. These tolerances can be loosened by an additional factor of 1.5, but at the cost of 1.7% in energy overhead.« less
  • The main obstacle to emittance preservation in the main linac of a linear collider is the alignment of the quadrupoles and accelerating cavities with respect to the beam. The misalignment tolerances in the case of the TESLA superconducting main linac are reviewed. Simulations of possible beam-based alignment algorithms to meet these tolerances are presented.