25/01/16

On start up, received error when trying to access spectrum browser (attachment 1)   => required restart of 'Http for AIDA'

At 2us shaping time, and all other setting as last week, the situation remains the same

    - nnaida11 has width ~50ch, nnaida12 has width ~300ch, nnaida13 is quad peaked and nnaida14 is not quite Gaussian but has width of ~80ch (possibly two peaks very close together)

Change shaping time to 8us.

Swap cables to see if the cable is the source. Currently have two LH coupler + shielded ribbon cables connected to nnaida11/13 (11 good performance, 13 quad peaked)

     - swapped the ribbon cables over but left the couplers where they were to see if the good performance is a consequence of something intrinsic to a particular ribbon or coupler.

     - nnaida11 now has width ~40ch                  (attachment 2)

     - nnaida13 now back to double peaked       (attachment 3)

     - inconclusive.

Could old style kapton laid next to nnaida11 be shielding it due to the built in screen? (the kapton is laid against the ribbon cable)

     - removing the kapton makes no difference to widths, other than nnaida12 which comes down to ~15ch (as expected)

Clipping cable ends together makes no difference, and no combination of jumpers could improve the widths.

Bending cables through 90 degrees makes no difference either (if they were acting as aerials).

Swapped complete PCBs with cables still in place over. Test first thing tomorrow.

26/01/16

Swapping PCBs produced no difference

     - nnaida11 has widths of ~50-60ch, although some structure visible in some peaks

     - nnaida14 sees double peaks.

Clipping ribbon ends together now makes things worse.

Swapped PSU cables to nnaida11/14

     - nnaida11 now marginally worse @ ~70ch width

     - nnaida14 sees no obvious change

Connected PSU chasis to NIM crate - no change.

Added two more ribbon + HL/RH couplers to system. Now:

      - nnaida11 = LH + ribbon

      - nnaida12 = LH + ribbon + RH

      - nnaida13 = LH + ribbon + RH

      - nnaida14 = LH + ribon

Clipped drain wire to LEMO connectors on PCB instead of pulser BNC cable.

See marked improvement in performance. All nnaida now have single Gaussian peaks with widths now:   (attachments 4-6)

       - nnaiada11 at ~35ch

       - nnaida12 at ~70ch

       - nnaida13 at ~80-120ch

       - nnaida14 at ~45-55ch (3 at ~80-150ch)

Added RH coupler to nnaida11/14, with thin braid taped over joint in shielding to reduced resistance

       - nnaida11 widths increase slightly to ~40-60ch

       - nnaida14 widths increase slightly to ~60-80ch, few round ~100-120

This is consistent with the RH coupler increasing widths by ~25ch, as seen in previous tests.

See occasional ripple through waveforms in nnaida11/14    (attachments 7-11).

      - expanded view shows period of 34 samples  ==> 680ns   ==> frequency ~1.5MHz

Variation with shaping time (avg peak width over a several channels):

* = some non-Gaussian peaks

Connected detector, biased to +200V (+ve core to nnaida12, -ve braid to nnaida14) with leakage current = 9uA.

At 8us shaping time, and with Lk1 fitted on nnaida13/14 RevC adapter, peaks across all nnaida have widths ~70ch and are all single Gaussian peaks.   (attachments 12-15)