[Vetroc_daq_sbs] VETROC pulser test status

[R. Evan McClellan]

Hi all,

Before the winter shutdown begins, I'd like to briefly describe the status of the VETROC pulser tests.


Test Setup:
-For these tests, I am using the VETROC as an externally-triggered TDC. That is, I am using an external signal to trigger the TI, bypassing the GTP.

-The VETROC channel 112 reference signal and the TI trigger signal are from the same pulser, with appropriate relative delay.

-I am also sending pulses to four VETROC signal channels. These pulses are generated independently of the trigger/reference pulses. However, I have gated the signal pulses with a copy of the trigger pulse, so that the four signal channels only receive pulses within the VETROC TDC window. (While somewhat unrealistic, this is required so that I can compare counts of sent vs recorded pulses.)


Results:
-Sending just one signal pulse per channel per trigger, I have ramped up the trigger rate. The VETROC TDC data is perfect until the trigger rate reaches ~500kHz. This is consistent with a ~2us deadtime.

-Setting the trigger rate to 10 kHz, I then ramped up the rate on the four signal channels. Everything looks great until ~10MHz.
-At and above 10MHz signal rate, the VETROC apparently begins dropping EVENTS in the TDC. This is concerning, because the signal channels should not be able to affect the triggering and readout. It is possible that unusual TDC data is simply confusing my decoder. I still need to closely investigate the raw coda files for these high-rate runs.


Conclusions: 
-The VETROC test setup can handle a trigger rate of up to ~500kHz (periodic, non-random), and a signal rate up to ~10MHz (periodic, non-random).


Pulser Test To-Do:
-Investigate data anomalies with >10MHz signal rate
-repeat tests using many more (all?) signal channels simultaneously
-repeat tests with non-periodic pulses (both for trigger/reference and signal)


Cheers!
Evan


R. Evan McClellan, PhD
Hall A Postdoctoral Fellow
Jefferson Lab