# 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.

### 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.

## 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.

### 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:

### 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:

### HV scan at DAC = 70V

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

*Position scan:

*HV scan:

## 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)

• 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 %

### 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

### 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

### 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

-- AlessandroMapelli - 28 Feb 2007

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

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