ELOG AIDA

AIDA GELINA BRIKEN nToF CRIB ISOLDE CIRCE nTOFCapture DESPEC DTAS EDI_PSA 179Ta CARME StellarModelling DCF K40

AIDA

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Entry time:

Fri Nov 25 15:56:36 2016

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00.55 Bias and leakage currents ok (attachments 1+2).
      Temps ok (attachment 3).

01.40 DAQ starts (RIBF03R1 - Run R1)

Pulser walkthrough

BNC PB_4 amplituides 90,000 - 10,000 @ 10,000 step
      x5 attenuator IN
      frequency 250Hz range
      t_r 50ns tau_d 50us
      polarity -, tail pulse, delay MIN

01.55 Ambient temperature +24.8 deg C, d.p. -2.2 deg C, RH 16.6%

02.05 DAQ starts (RIBF03R1 - Run R2)
 
      Pulser walkthrough - same settings as above.

BNC PB_4 amplitudes 14,000 - 2,000 @ 2,000 step

02.48 Run R3 started.
      Pulser off. Background run.

15cm Pb wall removed

6mm Pb degrader installed between MUSIC 1 & 2
      variable degrader 1mm, 0.5mm & 0.3mm W + 1mm Al attached to each W sheet.

04.14 Noticed R3 stopped

05.40 Difficulty starting DAQ
        'want first SYNC' from merger
        lost contact with nnaida19 - restarting merger
        TclHttpd server on nnrpi1 crashed - restarted remotely
        unable to power cycle - need to check fuses when next obtain access
        whilst waiting boot aidas1

F11 rate c. 450Hz
        AIDA veto plastic c. 3200Hz

07.30 R7 started with beam.

07.38 Beam stopped.
     R7 continues.

08.12 Beam returned to F11.
      File R7_9

08.50 Beam stopped.
      Start of R7_17.
      Using implantdecay.f saw no HEC events in any DSSD. Removed 2mm of Pb degrader.
      We re-insert all the variable Al degraders (for now) for safety.  We can remove them again when the beam
comes back, as necessary.
      Secondary beam current expected to remain at ~50cps.
      Now no beam for ~1hr.

10.15 Beam comes back
      There was a minor delay to get the beam back from some accelerator issue (SRQ issue I am told)
      F11 plastic rate is about 10 cps, still I can see nothing in AIDA low gain
      Main exp. team confirms several 40Mg events within minutes, and makes jokes about old Nature paper with 10 days of
data to do that.

10.25 Trying to find AIDA's implants, using MIDAS Sort in online mode
      Removed the variable degraders, one-by-one.  Still nothing? (this is now circa file R7_36)
      Is there a possibility that the "low gain" setting of the ASIC is too high energy for something like 40Mg?
      We try to check the implant rate with the AIDA veto plastic
      During this time, we moved degraders in and out, several times, watching the oscilloscope and visual scalers by
video link in F11

10.39  We check some scalers of the dE before AIDA (including F11 x plastic behind AIDA)
      We can see a reasonable effect as expected for these detector count rates
      The count rate never exceeds about 50 to 60 cps at maximum for dE
      I don't trust MIDAS Sort in online mode
          it is known to show factor 10 or less of the real rate, previously)
      Check the data file R7_37 -> may show 1 to 2 Hz
      We should decrease the low gain (heavy ion) threshold or dynamic range for the ASICs?
          But DK is not an expert of that, and doesn't want to cause AIDA to cease functionality...

11.03  Checking runs later than R7_37 (i.e. _38 to _42)
      Never see anything.  R7_37 must have been taken with some amount of degraders in
      We surmise that the ions are mostly punching through AIDA, owing to low Z.
 
11.05  We put in the 0.5 W + 1 mm Al degrader back, to see if we can get back the condition of _37...
      R7_44 after a short delay should have this condition.
      There can be 1 cps or something, though with small statistics it is hard to say...
         It seems to be definitely non-zero though, compared to some runs like _38 to _42

11.10  Add the 1.0 W + 1mm Al (with the 0.5 W and 1 mm Al) degrader
      R7_45 begins ~400 MB before this time.
      We can see some kinds of definite hit events **with low stats** (1 to 2 Hz in several detectors in some data blocks)

It seems to be, if all degraders are out, that the beam punches through AIDA, and dE is below the thresholds
      Of course, the count rate at F11 is only 10 cps, so we cannot conclude much with strong confidence...

11.17 Remove all variable degraders again (near halfway point of R7_46)
      We need a decent LISE++ file to get a clue of where these ions are stopping...!

11.42 Beam is stopped because one of the cyclotron RF systems is down.
      This occurs around the middle of file R7_50

12.40 Still waiting for beam.  I try a more definitive analysis of R7_45

Partial disk analysis of file R7_45:

First part of data look like this:
 *** DSSSD # 1 count:         4 old count:         2 dt:      1.06 s  HEC rate:      1.89 Hz
 *** DSSSD # 2 count:         1 old count:         0 dt:      1.06 s  HEC rate:      0.94 Hz
 *** DSSSD # 3 count:         0 old count:         0 dt:      1.06 s  HEC rate:      0.00 Hz
 *** DSSSD # 4 count:         0 old count:         0 dt:      1.06 s  HEC rate:      0.00 Hz
 *** DSSSD # 5 count:         0 old count:         0 dt:      1.06 s  HEC rate:      0.00 Hz
 *** DSSSD # 6 count:        10 old count:        10 dt:      1.06 s  HEC rate:      0.00 Hz

Notice that we get 10 total counts in DSSD#6, and practically 0 in any other layer (2 in DSSD#1)

Now, as the analysis progresses, we do not increase the counts in DSSD#6, but we start to see events in other layers
 *** DSSSD # 1 count:       128 old count:       128 dt:    343.81 s  HEC rate:      0.37 Hz
 *** DSSSD # 2 count:       115 old count:       115 dt:    343.81 s  HEC rate:      0.33 Hz
 *** DSSSD # 3 count:        91 old count:        90 dt:    343.81 s  HEC rate:      0.26 Hz
 *** DSSSD # 4 count:        41 old count:        40 dt:    343.81 s  HEC rate:      0.12 Hz
 *** DSSSD # 5 count:        13 old count:        13 dt:    343.81 s  HEC rate:      0.04 Hz
 *** DSSSD # 6 count:        12 old count:        12 dt:    343.81 s  HEC rate:      0.03 Hz

*** ENTRY finish ends

Notice how only 12 counts in DSSD#6 (two new counts) but 128 counts in DSSD#1 (126 new counts).

We can conclude that with 3 mm Pb (fixed), and 0.5 mm W and 1.0 mm Al, some of the beam is stopping in DSSD #6, and mostly
punches through.
Then, when 1.0 mm W and 1.0 mm Al are added, we shift the implantation to the beginning of AIDA (or some in the air
before AIDA).
So, we should try the 1 mm W (+1 mm Al) and 0.3 mm W (+1 mm Al) once the beam returns.

13.34  Stop run 7.  
     Change the medium/low energy selection on ASIC control from 0x0 to 0x1 (from low to medium energy mode)
     (Already, the high energy setting is 0x2 and we cannot decrease it)
     Start run 8.  It looks okay, though of course now data rate becomes much smaller.

13.36 Beam is now on again.  F11 rate has decreased 1 order of magnitude (now it is 0 to 2 Hz)

14.00 As expected, data rate becomes quite low, as the low energy mode has typically many events (10kHz or so)
     But now we don't see anything in the high energy mode as before
     3 mm Pb remains in, and variable degraders are all out (mistake...we meant for some to be in)
     Strange!  But the beam at F11 does not seem to be the same rate as before the cyclotron issues...
     Realized that someone was checking the beam at an earlier focal plane and that F11 has no beam...
     (Post-dated note: forgot to hit "Start ASIC Readout" ---  duh oops.
     RUN 8 IS JUNK, AS NO ASIC READOUT BY USER ERROR (DK)

14.12 Stop run 8.  Change the medium energy mode back to low energy mode of all ASICs.  Restart as run 9.
     But the merger data links don't alternate colors when I reload the merger screen.  Is it bad?
     Data rate is still very low, but that doesn't make much sense.
     Okay, now I start ASIC Readout!  Woohoo!
     But it seems some magnetic dipole of BigRIPS must have an improper setting, explaining the 1 cps rate at F11...

15.33 Bias and leakage currents OK (attachments 9 & 10).
      FEE64 temperatures OK (attachment 11).

15.40 SRIM 2013

145MeV/u (5800MeV) 40Mg + 3mm Pb 
      sigma 0.55 deg
      ang X (str) 0.90 deg
      assume Pb - DSSSD distance c. 2m => 2000 x tan(0.55 deg) ~ 17mm rms
      consider reducing Pb - DSSSD distance

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