Bunch Attenuation Help

This panel contains all the information needed for controlling and monitoring the Bunch Monitor Attenuation.

The readback (Rdbk) indicates the currently set attenuation values. The Sreq indicates the manually requested values, and the Hreq indicates the automatically generated request. The Auto/Manual selection button determines the mode. In Auto mode, the peak goal value determines the attenuation such that the peak ADC value is about 90% of full range. The attenuation is set when injection starts up.

The "Atten Threshold" is the per-bucket value (in microamperes) at which a non-zero automatic attenuation is desirable. The formula in use is:

Attenuation = 20* LOG10 (Max_single_bucket_current/Atten_threshold)

The "Cal at zero Atten" is the bunch current calibration at zero attenuation. The initial guess at a bunch current calibration for an empty ring (no valid measurement available) is:

Calibration = Calibration_at_zero * exp(0.1151*Attenuation)

Where the Attenuation is either the automatically calculated or manually set attenuation, depending on the mode selected.