Watching wakefields
to keep particles on track
(Page 4 of 4)
T3P, Omega3P, TEM3P and the other so-called finite element codes developed under SciDAC are readily generalized for use on many accelerator designs, Lee says. “That’s one reason we could quickly model the ILC when it was chosen to be the future linear collider in 2005.”
That flexibility came in handy for another aspect of the team’s project: Modeling wakefields in part of the Compact Linear Collider (CLIC), a proposed alternative positron-electron collider under design at CERN, the European particle physics research center. CLIC aims at accelerating particles to energies as high as 3 trillion electron volts. It would have two accelerators, with one supplying radio frequency power to the main beam via special power extraction and transfer structures (PETS).
Using T3P, the researchers modeled the PETS to look at deleterious wakefields and how dielectric materials might dampen them. The simulation showed damping materials cut wakefield amplitudes by an order of magnitude. It also showed the quality of the accelerating RF waves could be maximized while their frequency is constrained across cells of the PETS cavity.
The SLAC team will continue modeling the ILC heat load on cavity interconnects in greater detail while also considering how deformed and misaligned cavities affect wakefields.
The added processor hours will be a big help, Lee says: “With cryomodule deformation our meshes have to be finer,” and thus, more hungry for computer power. “To identify those misalignments we have to resolve these kinds of small differences.”
The researchers also will continue modeling a full cryomodule to study “crosstalk” effects that occur when wakefields generated in one cavity bleed over into others.
At some point, “We also want to push the (simulated) beam size closer to the realistic beam size,” Lee says. “In the ILC the beam length is about 300 microns. If we needed to resolve it, the mesh would be humongous – on the order of 1014, which is (computationally) out of reach at this moment.”
Nonetheless, that degree of resolution is necessary to show how the full wakefield spectrum influences beam heating.
Says Lee, “We still have work to do.”
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