17/02/15

1515: Installed detector BB18 2977-7 with 3 modified kapton cables, one unmodified (in nnaida1) with 207Bi source.

           Bias voltage @ -100V with leakage current -11.6uA @ ambient temp of ~20oC.

           nnaida1,3,6,8 connected to detector, all with shaping time of 2us and hold time 8us.

           Slow comparator thresholds around 0x18 and fast comparators 0xf (see below images).

           Pulser at 50,000 with x5 attenuator @ 25Hz. Both polarities supplied via use of Ortec 433A dual sum and invert amp.

           nnaida1+6 p+n side, -ve bias. nnaida3+8 n+n side, ground.

           nnaida3 most well behaved, with low rate similar to that of pulser rate and no missing channels. Waveforms look good.

           Pulser peak has smallest FWHM @ ~150ch, compared to 1000s of ch for the other nnaida.

           For comparison, nnaida7 (not connected to detector) has peak width of ~18ch FWHM.

           nnaida1,6,8 have typical pulser peak widths of the order 1000-3000ch FWHM. Peak too broad in nnaida6 to be distinguishable from noise peak.

           Waveforms from nnaida3 stable and as expected. nnaida1+6 slightly more variable and noisy.

           Waveforms from nnaida8 see much greater noise and variability, including rail-to-rail transitions.

           Increasing the pre-amp reference from 0x30 to 0x60, removes rail-to-rail transitions, but waveforms remain just as noisy.

1650: Successfully started Merge and Tape servers, writing data to disk.

            Merge terminal window shows errors regarding Sync pulse timestamp sequence errors (see attachment #18). 

1900: Installed Caen N1419 floating HV bias supply.

            Connected to detector via nnaida3, positively biasing n-side through core with p-side as low V reference through braid. Saw no leakage current => open circuit.

            After some problem solving found reversing the bias and negatively biasing p-side worked. Possible broken bond wires delivering bias on n-side.

            Connected to nnaida8 (also positive bias to n-side) and found short circuit. Saw leakage current of 200uA (trip level) @ 5V.

            Changed to negative polarity bias and connected to nnaida6 and saw sensible leakage current of -11.5uA @ -100V bias.

            Spectra for each module showed FWHM for the pulser peaks to be: nnaida1 ~800ch, nnaida3 ~150ch, nnaida6 ~3000ch, nnaida8 ~1200ch.

            FWHM in nnaida1 reduced by ~1/3, nnaida6 shows little change, nnaida8 reduced by ~1/2. nnaida3 shows no change, but in line with what was seen at DL. (w.r.t peak widths seen last night using Selena bias supply)

            nnaida3 performing much better than other three cards connected to detector, but in line with what was seen at DL. Other 3 cards very noisy.