Start Counter Operations 2023

Start Counter Operations Winter 2023

looking at the dEdx data of the start counter one can come to several conclusions:

• there is a noticible slope indicating a diminishing gain over time
• there are two distinctive "lines" that with the second one at a somewhat lower gain. This can be readily identified with AMO radiator runs. Why this whould cause a different gain in the Start counter is unclear. It is true that the photon flux is somewhat lower than for the Diamond radiator runs since the electron beam current was the same.
• the changes in gain seem to not just change gradually but the seem to have some "step" function aspect to it. And rather than looking at a gradual change over time one can identify sections of times where the gain was rather constant.
• the overall gain reduction from the start of the run period to the end is of order 1.7%, so it is not as dramatic as the plot may suggest (y-scale).

Note:

• All runs with significant smaller values for dEdx around run 120496, 120582, 121037 are all related to high electron current tests! Supporting the notion that the gain of the Start Counter is luminosity/rate dependent!
• This is further "confirmed" by the line of points at intervals lying below the line of the majority of the runs. Those points can be correlated with AMO runs that seem to have a higher photon flux at the with the same e-beam current.

Examples of Paddle to Paddle variations

As an example of the paddle to paddle variation run 120988 was chosen to demonstrate the similar behavior of the start counter as in the run period of 2017 but at lower "gain":
RAW data:

Renormalized to mean gain:

Average means

The variation of the gain is rather small over the run period. The mean start counter signal amplitude is rather stable as demonstrated in the following plot, and certainly much more stable than the run period 2017 but is about 23% lower response than at the start of run period 2017.