The names for the ABS holding field correction coils are LSVIT1
(upstream) and LSVIT2 (downstream). There's already an EPICS screen for
them, made by Gino Foti.
I checked the remnant field in the upstream steering coil (because it
was easier to reach); around 30G horizontal where the poletip meets the
beam pipe. Looks like the coil is about 20cm long, so the field
integral is about 600G-cm. That would bend a 10MeV electron about 1
degree, I think, if I didn't slip a digit or two. If the electron is
already off the centerline, maybe 1 degree is enough to crash it into
the pipe and make a particle that gets to a TOF. Seems like a big IF,
though.
Just to cover all bases, I'm trying to null the remnant field in both
coils. Right now there's a problem controlling these coils (set current
and readback don't agree). Hopefully this can be done by the end of
today.
NOTE: A current of around 1A (hard to tell with the set/readback
problem). gave a poletip field in the neighborhood of 500G. But you
won't need much current to null the remnant field.
Karen
> I was not able to perform tests with the downstream magnet current turned
> partially on but with opposite sign of normal running mode. CCR did not
> know which magnet I was asking about. They wanted to know its LS number
> (i.e. lattice steering number), which I did not know; it was not
> sufficient to say the "steering correction magnet located about a meter
> downstream from the target."
>
> Aaron
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