[Alex, Boris, Andrew] 

I have been working with Boris and Andrew Muller to do testing on the GQuEST SNSPD using 3 different options we have for voltage sources in the lab. The following plots will further detail the results of using each of these sources which include an old battery powered SRS voltage supply, and the new DAC VME that was developed by Lautaro. We also compare two different channels on the DAC VME where one of the two includes a low pass filter on the output voltage. tests of biasing the SNSPD with positive and negative voltages were also done to find any likely voltage offsets between the two. 

In our testing we have found that the filtered output on the DAC VME has a voltage shift, such that the output voltage is slightly less than what is being set with our code. Thus the PCR and DCR curves are shifted to the right on the plot bellow.

The channel without the LP filter seems to have a very similar PCR response to that of the SRS which is what we hoped to see for both. 

This issue will be addressed with Luataro and we will also run callibrations next week to determine the exact voltage outputs of each system relative to what is being set via SCPI commands. 

As mentioned all tests have been done using the GQuEST SNSPD, and thus we are seeing dark count rates that apear to be in the range where the SNSPD rails due to overstimulation of current. Thus, it is expected that in our lower bias ranges (where efficiency should be highest) we will see dark counts well within our 10^-4 regieme (outlined in pink shaded region). This will require the dark box being reinstalled and tests ranging from 1-3+ hours per data point to achieve this resolution. 

In the meantime, we will be diagnosing the voltage supply variations and attempting to get each of the PCR curves to overlap.