[Rgc] RGC weekly meetings back on Tuesdays (this time focused on FTon extension)

[Sebastian Kuhn]

Hi Silvia,

just for clarification:

On Aug 22, 2022, at 4:48 AM, silvia at jlab.org<mailto:silvia at jlab.org> wrote:

- if the target polarization (or its knowledge) doesn't improve, as you
fear, this would affect in the same way the FTon or FToff data.

The point is that with an underrasted target (which  we have even for NH3), we never quite know when to do another anneal and hence end up with suboptimal average target polarization. I believe Harut’s newest plots show this point nicely. For FTout, we can hopefully raster over the entire 2 cm diameter (or close to it) for both NH3 and ND3, and the NMR will be more reliable for sure.

- the factor 2.5 of increase of luminosity you mention is new to me: I
thought FToff would allow a factor of 2 more luminosity, at most. Aside
from DC occupancies (which must be verified experimentally with ELMO +
raster) I understand that the target can work with twice the present
current by doubling the rastered area (as will happen moving from 1.5 to
2cm diameter). But if the current increases further we'll have to anneal
more often, thus increasing the loss of beam time.

Right now, we are running with 4 nA which roughly translates to 4x10^34 luminosity. For FTOut, we are planning to run with 10 nA - which SHOULD be o.k. according to simulations, but we won’t know for sure until we switch.
Right now, we raster over a 6 mm radius at best (it could be even less). If  we can go to 9 mm radius for FTOut (again, we won’t know for sure until we switch), the raster area will increase by a factor 2.25 which means that even with 2.5x the current we likely won’t  have to anneal (much) more often. But we will KNOW when to anneal, meaning we will neither wast time annealing when it wasn’t necessary nor running with low “true” polarization.

- Sebastian

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