ALFA OVERLAP DETECTOR STUDY (NOT UP TO DATE)

The Prototype Overlap Detector (OD) built for the test beam consists of 2 sets of 2 planes each composed of 30 fibres on the left side and 30 fibres on the right side. The upstream planes are referred as OD2 and the downstream planes as OD1.

RECONSTRUCTION OF THE DISTANCE BETWEEN OD2 & OD1

Reconstruction with 2 planes per OD

  • Runs used: 10394 - 10408
  • HV = 950V, DAC = 70V
  • Total number of events per run: 50k or 100k
  • Selected events must have one and only one hit in each of the 4 layers.
    OD_reco.jpg

Reconstruction with 1 plane per OD

  • Runs used: 10394 - 10408
  • HV = 950V, DAC = 70V
  • Total number of events per run: 50k or 100k
  • Selected events must have one and only one hit in each of the 2 layers.
  • The reconstruction with 1 layer / OD should give the same result as with 2 layers / OD. However we find different results. We think it comes from the high number of channels fired for a single event, it can reach as many as 60 channels (all the active channels) and it is greater than 10 channels for many events. The selection of tracks with 1 layer instead of 2 layers is therefore worsened by the fact that we have a higher probabitlity to randomly select unexisting tracks for a given event.
    Slide46.jpg

HIT MULTIPLICITY & SELECTION EFFICIENCY

Position scan at 950V

  • Runs used: 10394 - 10408
  • HV = 950V, DAC = 70V
  • Total number of events per run: 50k or 100k
  • Position scan between the runs
  • From run #10401, the number of hits in OD1 increases. It might be due to collective effects.
Typical distributions of hits before (left) and after (right) this increase are shown at the bottom.
950V_pos_scan.jpg

Threshold scan at 950V

  • Runs used: 10357 - 10368
  • HV = 950V, DAC = 40V to 70V
  • Total number of events per run: 50k
  • Relative position of 1 set of plane and the other is constant
  • multiplicity_950V_DAC_scan.jpg:
    950V_DAC_scan.jpg

Threshold scan at 1000V

  • Runs used: 10379 - 10384
  • HV = 950V, DAC = 20V to 30V
  • Total number of events per run: 50k
  • Relative position of 1 set of plane and the other differs by 1.6mm for the same DAC values
  • multiplicity_1000V.jpg:
    1000V_DAC_scan.jpg

HV scan at DAC = 70V

  • Runs used: 10379 - 10384
  • HV = 850 - 950V, DAC = 70V
  • Total number of events per run: 50k

Multiplicity in every layer & selection efficiency for each OD

Multiplicity_1Layer_HV_scan.jpg Efficiency_1OD__HV_scan.jpg

Multiplicity in both ODs & selection efficiency in the full detector (4 hits, single hit per layer)

Multiplicity_Both_ODs_HV_scan.jpg Efficiency_4hits_HV_scan.jpg

Probability of hitting an expected fibre in the next layer

CROSS TALK

Cross talk at level of the fibres...

Xtalk_fibres_HV_scan.jpg

Cross talk at level of the MAPMT...

*Position scan:
Xtalk_PMT_Pos_scan.jpg
*HV scan:
Xtalk_PMT_HV_scan.jpg

NOISE

A look at the unconnected channels

  • Runs used: 10367 - 10358
  • HV = 950V, DAC = 40 - 70V
  • Number of events: 50k

Number of hits per channel for layers 15 (in the beam) and layer 16 (out of the beam)

10368.jpg
  • A. # of hits on fibres in the beam ~1800 3.6 %
  • B. # of hits on channels unconnected in the beam ~200 0.4 %
  • C. # of hits on fibres out of the beam ~200 0.4 %
  • D. # of hits on channels unconnected out of the beam ~20 0.04 %

Number of hits per channel for the 4 complete PMTs

unmasked.jpg

Ratio of hits from channels not connected to fibres and channels connected to fibres

  • Runs used: 10357 - 10368
  • HV = 950V, DAC =40 - 70V
  • Number of events per run: 50k
    discon_con.jpg

Ratio of hits from channels connected to fibres and hits on the trigger

  • Runs used: 10357 - 10368
  • HV = 950V, DAC =40 - 70V
  • Number of events per run: 50k
    con_trig.jpg

Ratio of hits from channels not connected to fibres and hits on the trigger

  • Runs used: 10357 - 10368
  • HV = 950V, DAC =40 - 70V
  • Number of events per run: 50k
    discon_trig.jpg

-- AlessandroMapelli - 28 Feb 2007

Topic attachments
I Attachment History Action Size Date Who Comment
JPEGjpg 1000V_DAC_scan.jpg r1 manage 33.2 K 2007-02-27 - 19:53 AlessandroMapelli  
JPEGjpg 10368.jpg r1 manage 293.3 K 2007-02-26 - 21:56 AlessandroMapelli  
JPEGjpg 2hits_per_OD_950V_DAC_scan.jpg r1 manage 22.1 K 2007-02-27 - 16:24 AlessandroMapelli  
JPEGjpg 950V_DAC_scan.jpg r1 manage 24.9 K 2007-02-27 - 19:54 AlessandroMapelli  
JPEGjpg 950V_pos_scan.jpg r1 manage 29.9 K 2007-02-27 - 18:18 AlessandroMapelli  
JPEGjpg Efficiency_1OD__HV_scan.jpg r1 manage 18.3 K 2007-02-28 - 11:39 AlessandroMapelli  
JPEGjpg Efficiency_4hits_HV_scan.jpg r1 manage 15.9 K 2007-02-28 - 11:39 AlessandroMapelli  
JPEGjpg HV_scan.jpg r1 manage 23.3 K 2007-02-27 - 21:54 AlessandroMapelli  
JPEGjpg Multiplicity_1Layer_HV_scan.jpg r1 manage 18.8 K 2007-02-28 - 11:38 AlessandroMapelli  
JPEGjpg Multiplicity_Both_ODs_HV_scan.jpg r1 manage 12.5 K 2007-02-28 - 11:40 AlessandroMapelli  
JPEGjpg OD_reco.jpg r1 manage 59.3 K 2007-02-05 - 14:23 AlessandroMapelli  
JPEGjpg Proba_HV_scan.jpg r1 manage 24.7 K 2007-02-27 - 21:55 AlessandroMapelli  
JPEGjpg Slide46.jpg r1 manage 72.1 K 2007-02-11 - 22:47 AlessandroMapelli  
JPEGjpg Xtalk_PMT_HV_scan.jpg r1 manage 15.6 K 2007-02-28 - 12:12 AlessandroMapelli  
JPEGjpg Xtalk_PMT_Pos_scan.jpg r3 r2 r1 manage 43.6 K 2007-02-28 - 12:17 AlessandroMapelli  
JPEGjpg Xtalk_fibres_HV_scan.jpg r1 manage 18.9 K 2007-02-28 - 12:11 AlessandroMapelli  
JPEGjpg con_trig.jpg r1 manage 25.0 K 2007-02-27 - 16:44 AlessandroMapelli  
JPEGjpg discon_con.jpg r1 manage 20.7 K 2007-02-27 - 16:44 AlessandroMapelli  
JPEGjpg discon_trig.jpg r1 manage 25.0 K 2007-02-27 - 16:45 AlessandroMapelli  
JPEGjpg efficiency_950V.jpg r1 manage 34.3 K 2007-02-27 - 16:30 AlessandroMapelli  
JPEGjpg hits_950V_pos_scan.jpg r1 manage 41.3 K 2007-02-27 - 17:22 AlessandroMapelli  
JPEGjpg multiplicity_1000V.jpg r2 r1 manage 42.4 K 2007-02-06 - 11:03 AlessandroMapelli  
JPEGjpg multiplicity_950V.jpg r3 r2 r1 manage 38.9 K 2007-02-06 - 11:02 AlessandroMapelli  
JPEGjpg multiplicity_950V_DAC_scan.jpg r1 manage 19.7 K 2007-02-27 - 16:29 AlessandroMapelli  
JPEGjpg reco_2_layers.jpg r1 manage 43.6 K 2007-02-27 - 21:53 AlessandroMapelli  
JPEGjpg unmasked.jpg r2 r1 manage 618.5 K 2007-02-26 - 21:47 AlessandroMapelli  
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Topic revision: r12 - 2008-06-04 - AlessandroMapelli
 
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