Sergei Seletskiy made a presentation on the optics design of the extraction lines for the RTML. There are 3 such extraction lines: one after the DR extraction point (which is needed for DR commissioning and running the DRs when the linac is in access), one after BC1 and one after BC2. There are many constraints on the system design; Sergei presented a solution which meets them in a reasonable system length and with relatively few optics components. The talk can be viewed
here.
A few questions came up as part of the discussion:
- Does the BC2 extraction system need collimation to manage the nonlinear halo? No, the halo is much smaller in BC2, in particular the 2nd order dispersion in x is weaker because of the weaker dispersion, which in turn is because the bend angle is smaller at 15 GeV than at 5 GeV.
- At the moment the DRX system is a copy of the BC1 system; since the DRX system does not need to manage as large an energy spread as the BC1 system, it could in principle be shorter and simpler.
- Does the kicker system correspond to the Mattison configuration, which fills the available beamline length with kickers in a way which minimizes the input power required, and which also uses a "D" quad after the kickers to help the beam get out of the straight-ahead channel and into the extraction channel? Not sure, this would be good to check. Given the relatively low beam energy it may not be necessary to optimize the kicker power.
- Is there kicker redundancy? Do we need it? In the BC1 system, at least, the kickers are running much weaker than their maximum field, and so we could probably run with just 2 out of 4 kickers if there was enough input power. This should be checked for all 3 systems.
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