SWAMP Gain and Delay measurements

The delays and gains of the SWAMPs prior to the SWAMP upgrade has been measured in order to bring AMANDA up as it was before the changes started. The measurements has been done on strings 1-4, 11-13 and 14-19, and OMs which do not use SWAMP output were not measured. After the upgrade the gains was measured and set back to the old values. In case the swamp card was dead or missing before, we set the new values to 1.0 for prompt and 0.5 gain.

The delay measurements were conducted by feeding the swamps with a square pulse and measuring the response in the prompt and delayed outputs. The test signal for the delay measurements was a square pulses with a duration of 0.8 microseconds, period of 12 microseconds and an amplitude of 10 mV. The amplitude was achieved by using a 20dB attenuator to damp the signal. For the gain measurements the test signal was a 1 MHz sine function with peak-to-peak value 10 mV. Three delay measurements were done:

Delay prompt rise time: Time difference between incoming pulse and when the prompt output starts rising. Rise time from the rising start is approximately 70-80 ns (0-90%), (this was tested on three sample OMs on string 15)

Delay in delayed rise time:Time difference between the test pulse and the delayed output pulse. Due to oscillations on the base line output the starting point is difficult to estimate, uncertainty within 50 - 100 ns.

Delay in delayed max time: Time difference between incoming pulse and when the delayed output pulse reaches its maximum. To estimate the signal rise time we measured the maximum peak time of the delayed output signal.

To measure the gain we used a sinusoidal 1 MHz 10 mV (peak-to-peak) 50 Ohm pulse as input signal and measured the prompt and the delay output gain.