Survey and Orientation of Beam-Coordinate system near the Extraction Region of the SNS Ring
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
The fast beam extraction process of the SNS accumulator ring can be accomplished by two steps. In the first step the beam is kicked , by a set of 14 fast-kickers, vertically down to a direction making an angle –13 mrad with the horizontal. In the second step a septum magnet bends the beam to the left (and on the outside of the SNS accumulator ring) by 16.8°. In such a magnet geometry, where the bending plane of the septum magnet is not horizontal, (The beam-bending plane makes an angle of -13 mrad with the horizontal) the y-axis of the beam coordinate system, system at the exit of the septum magnet, may not coincide with the y-axis of the “fixed coordinate” system even when the direction of the beam (at the exit of the septum) is restored at the horizontal plane. Such a mismatch of the y-axes of the “beam coordinate” system with the “fixed coordinate” system may cause first-order beam coupling which will be introduced by the quadrupole magnets of the beam transfer line. In such a magnet geometry, it is common practice to roll the dipole magnets, whose bending plane is not along the horizontal, in order to bring into parallelism the y-axis of the “beam coordinate” systems with the y-axis of the “fixed” coordinate system at the exit of the dipoles. The roll of the dipole eliminates the mismatch of the y axis of the “beam coordinate” system with respect to the “fixed coordinate” system, and allows for the magnetic elements downstream of the septum to be surveyed with respect to the “fixed coordinate” system. Any linear beam-coupling which is introduced by the roll of the septum magnet can be corrected if necessary with skew quadrupole magnetic elements. In this technical note we study the orientation of the “beam” coordinate system with respect to the “fixed” coordinate system at the exit of the septum magnet, and provide the first order transfer matrices for four separate cases: a) No roll of the septum magnet. b) Roll of the septum magnet for “y-axes overlap”. c) Partial roll of the septum magnet for horizontal beam direction at the exit of the septum magnet. d) Partial roll of the septum magnet for determined beam direction at the exit of the septum magnet.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 1157271
- Report Number(s):
- BNL--105662-2014-IR
- Country of Publication:
- United States
- Language:
- English
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