An Optimized Superferric Wiggler Design for the International Linear Collider Damping Rings

Whole dissertation can be found here: An Optimized Superferric Wiggler Design for the International Linear Collider Damping Rings

Jeremy Urban, November 2006, excerpted from the Conclusions chapter of my dissertation:

The wiggler design proposed in this dissertation is based on the 2.1 T superferric wigglers that are operating with minimal degradation of the beam dynamics in the Cornell Electron Storage Ring [REF]. The performance of this magnet in the ILC was compared against a proposed permanent magnet wiggler designed by the TESLA damping ring collaboration [REF].

Replacing the TESLA wiggler with a modified version of the CESR-c wiggler significantly improved the dynamic performance of the TESLA damping ring [REF]. This wiggler performed so well because its nonlinearities are dominated by the inherent nonlinearity; the specific pole design of the CESR-c wiggler produces low levels of realistic wiggler nonlinearities. The superferric, modified CESR-c wiggler continued to perform at this high level in all candidate ILC damping ring lattices.

The modified CESR-c wiggler met the physics performance requirements [REF] of the ILC damping rings and some, but not all, of the technical engineering requirements. With 160 superconducting wigglers in the ILC damping ring, the technical requirements during construction, installation, and performance will be on an entirely different scale than the twelve wigglers operating in CESR. Therefore, optimizations were conducted on the peak field, unit length, period, pole width, and pole gap of the CESR-c wigglers in order to ease the technical requirements without compromising the physics performance of the ILC damping rings.

The optimizations achieved a superferric ILC-optimized CESR-c (SIOC) wiggler design that minimized the cost and technical engineering risks. Evaluating the physics performance of the SIOC wiggler in the baseline ILC damping ring showed that this wiggler continues to meet the targets for dynamic aperture, tune shift with amplitude, off-energy dynamics, and dynamics with multipole errors (find all simulations results here).

Comparison of wiggler magnet parameters.
Magnet Parameter Unit TESLA Wiggler CESR-c Wiggler Superferric ILC-Optimized CESR-c Wiggler
Peak Field T 1.67 2.10 1.95
Number of poles   18 8 12
Length m 3.6 1.3 1.68
Period m 0.40 0.40 0.32
Pole Width cm 6.0 23.8 23.8
Pole Gap cm 2.5 7.6 8.6
dB/B at x=10mm % 0.5700 0.0077 0.0600
Magnet Technology   Permanent magnet Superferric Superferric
Coil Current A NA 141 141
Beam Energy GeV 5 2 5

Performance of the Superferric ILC-Optimized CESR-c wiggler.
Lattice Parameter in OCS v2 Value
Damping time 26.4 ms
Radiation equilibrium horizontal emittance 0.56 nmrad
Radiation equilibirum energy spread 0.13 %
Dynamic aperture 8 x injected beam size
Off-energy dynamic aperture 7-8 x injected beam size
Dynamic aperture w/ multipole errors on D/Q/S magnets 5 x injected beam size


With the results of the above magnet optimizations, a range of beam and lattice parameters are available with only slight changes to the design of the modified CESR-c wiggler. Modifications to the design of the CESR-c wiggler have reduced the cost per wiggler by roughly 25%, saving approximately $20 million for the entire ILC project. Additionally, this conceptual design eases the technical risks and challenges associated with the mass-production of 160 ILC damping wigglers. Therefore, the superferric ILC-optimized CESR-c wiggler is recommended to be the baseline superferric ILC wiggler.

Using the SIOC Wiggler

ILCDR collaborators can access files here that describe the SIOC wiggler for their own use:

See Modified CESR-c Wiggler Design homepage for further background material and descriptions of the files.

Also see the simulations results here.

These results are also documented on the ILC@Cornell wiki-page

Created November 8, 2006
Modified November 14, 2006