1. Path Length Chicane Options
V. Morozov, A. Hutton, P. Nadel-Turonski, M. Sullivan
MEIC R&D Meeting, JLab, June 5, 2014
F. Lin

2. Outline
Path length chicanes in arcs
Path length chicane in straight 2

3. Concept of “Arc” Chicane
Reserve space for two extra dipoles in each arc, otherwise regular arc lattice
3 m long dipoles separated by 1.68 m distances with 0.5 m long quadrupoles in between
Arc bending angle is fixed (i.e. incoming and outgoing angles are fixed) and cord length is fixed (i.e. the coordinates of the arc ends are fixed)
Two extremes of a 10 dipole arc
Longest orbit: two dipoles at arc ends are off
Shortest orbit: two dipoles in the middle of the arc are off
Intermediate cases: the end and middle dipoles are partly powered 3

4. Geometry & Optics of “Arc” Chicane
Long configuration
59 cm between dipoles and quads, example optics matched to regular FODO
Short configuration
57.9 cm between dipoles and quads, example optics matched to regular FODO
Path length difference of mm
Need two chicanes, one per arc, helps with simultaneous synchronization of two IPs
Maximum total transverse movement of “only” 97 cm
May fit in the regular tunnel 4

5. Full “Straight” Chicane
Assume each dipole is 3 m long and bends by 50 mrad and require 40 cm path length increase
4 dipoles
8 dipoles
12 dipoles
16 dipoles 5

6. Half of “Straight” Chicane
Consider solving half the problem, 20 cm path length increase
4 dipoles
8 dipoles
12 dipoles 6

7. Conclusions Arc chicane Straight chicane
44.7 m long but most of it is occupied by existing arc bending dipoles
Each chicane provides 20 cm path length increase, need one in each arc but helps with simultaneous synchronization at two IPs
Spacing between dipoles and quadrupoles changes from 57.9 to 59 cm
Maximum total transverse movement of 97 cm, may fit in regular tunnel
Requires movement of 8 dipoles and 9 quadrupoles per chicane
Requires two extra dipoles and two extra quadrupoles per arc, total extra length < 20 m
Straight chicane
66 m long, perhaps with some usable space but takes up straight space
Maximum total transverse movement of 3.25 m
Single 40 cm chicane is more economical in terms of space
Considered making bending regions achromatic but requires strong quadrupoles and/or significant additional space
Did not seem worth pursuing much further because because of the arc chicane option
A chicane may not be an elegant solution but it does solve a lot of problems
No orbit shifts in either collider ring
No change of SRF frequency in either ring
No CEBAF synchronization problem
Conceptually simple, no additional R&D  easier to convince reviewers that it will work?
Easier to cost? 7