Target density variation check

PREX CREX Target Studies

Note: Silviu pointed out that word 'density' is not quite right here, it's thickness change unless the target is compressed somehow. I don't know how to change the title of the page, so I am leaving this note.
This thickness change would happen when the diamond get damaged. It would be interesting to check once the target chamber is open.

Pictures of damaged targets: https://prex.jlab.org/DocDB/0004/000428/001/TargetDamage.pdf

Run summary

• First measurement 09/02/2019
  • Summary plots
  • HALOG summary
  • Target #7 and #10 were checked for current range 5-70uA
  • Septum mistuned on purpose in order to reduce rates, T2 trigger is used
  • Sieve in
  • Clear non-uniformity observed from degraded target (#10) compared to good (still in use) target (#7).
  • More visible at higher current, but hint of similar signature of thickness rearrangement seen at low current.
  • Consistent results from both LHRS and RHRS spot data

• Second measurement 09/03/2019
  • Summary plots
  • HALOG summary
  • Took high statistics run at very low current (30nA requested), Target #10
  • Septum at nominal setting, no Sieve
  • Similar result shown in RHRS data as previous high current test
  • Different distribution in LHRS is puzzling, might be related to DAQ problem

• Qsq runs 09/03/2019
  • Summary plots from Qsq runs
  • HALOG run summary
  • 400-500k events for LHRS and RHRS runs during Qsq measurements with various targets (Pb7, 8, 9, 10)
  • Consistency between LHRS and RHRS recovered for target #10
  • Similar signature shown from Target 9 and 10. Target 9 and 10 were used with similar position wrt to collimator center. Later we moved the target ladder horizontally and vertically during repairs while we were running with Target 8. -> This is wrong, target repair happens around July 31 which was even before we started using target #9.
    • Actually the target ladder realignment was done during Target #9 period. (Aug. 7).

useful information

• Target re-alignment done during PREX2

- July 18 (3mm to left)
- Augusg 7 (2mm to right): while using target #9

Weibn's simulation study

HALOG entry
Simulation check shows that increased thickness in some area of the target resulting increased power to the collimator (and higher effect on radiation). Assuming a donut like shape and factor 2 increase in the thickness in the outer area compared to the center, this brings the collimator power by factor ~3 (compared 1st and 4th row).

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How to make plots

• full replay macro can be found from:

/adaqfs/home/a-onl/sanghwa/stupid_spot/get_rastersize.C

• To run:

> analyzer -b -q 'get_rastersize.C(run#, first evt, last evt, "outputpath/outputname")'

Example:

> analyzer -b -q 'get_rastersize.C(2293, 1, -1, "rootfiles/L2293.root")'

• To draw raster current xy distribution:
  • /adaqfs/home/a-onl/sanghwa/stupid_spot/make_2D.C

> root -b
> .L make_2D.C
> plot_all("dyn_therm.list")
This will create dyn_dens.pdf. To open:
> evince dyn_dens.pdf &

• Input file format:

<LHRS run#> <LHRS file path> <RHRS run#> <RHRS file path> <current> <target#>

• or, draw directly from tree (adjust bin low/upper limit as needed):

> T->Draw("Rrb.Raster2.rawcur.y:Rrb.Raster2.rawcur.x >> h(100, 0, 1.e5, 100, 0, 1.e5)", "", "colz")
> T->Draw("Lrb.Raster2.rawcur.x:Lrb.Raster2.rawcur.y >> h(100, 0, 1.e5, 100, 0, 1.e5)", "", "colz")