[Rgc] [EXTERNAL] FTCal and target irradiation

[Raffaella De Vita]

Dear All,

I checked the radiation dose on the FTCal we estimated a few months ago when we studied the running conditions for this portion of RG-C.

The attached slide shows the estimated dose rate in Rad/h for a luminosity of 10^35 and a raster of 6 mm radius. Based on that results and comparison with previous runs, the luminosity for the FTOn configuration was then chosen to be 5x10^34, so that the radiation dose would be similar to the one we had in RG-B production running. In that condition, we had observed an overall loss of about 5% in signal intensity in 20 days of running. 

If I understood correctly, the planned target irradiation would result in a dose rate of 30 rad/h (maybe 50 if the raster is more than 6 mm radius or is not centered on the Moller cone) for 8 h. If the effect will scale linearly with what we had in RG-B, that would lead to a loss of signal intensity of 1% or less, which would not be a problem. However, we never applied such a dose rate on the FTcal before and we would therefore be entering unknown territory.

One possible way to proceed could be to do a test first, running at that dose rate but for a shorter time (2 hours), doing FTCal calibrations before and after to determine the signal loss. To facilitate the calibration and have a quick turnaround we could restore temporarily the 2-cluster FT trigger that is ideal to get the energy calibration with pi0s.

Best regards,
	Raffaella

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