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    User name Breuer

    Log entry time 00:27:02 on January 11,2003

    Entry number 55574

    This entry is a followup to: 55252

    keyword=beam-line shielding analysis/result

    Effects of beam-line shielding
    ========================

    The data taken at 4500 A on the 12C target with 10 uA of beam before and
    after beam-line-shielding installation during the Christmas 2002/03 break
    (runs 15290,15291 before, 15351,15353 after shielding)
    have been analysed in more detail than the on-line analysis reported in
    G0log entry # 55252.
    The results found now are much better than initially thought!!
    The new more elaborate analysis separates the "background" from the
    "good data", i.e., from pions+protons (defined as all events with
    all 4 signals above threshold) and removes data taken at periods
    when the beam was off.

    The results are given below in tables as the shielding factors
    for all NA detectors. A few data points are bad due to low statistics
    in one of the pre-shielding runs.

    We find for the anode current:
    - for detectors 12 to 16 the backgrounds have the highest reduction factors
    -- between 2.5 and above 3.6 -- consistent with their large area and volume;
    these results are also consistent with Pavel's simulations;
    - the back detectors have higher shielding factors, consistent with background
    coming from downstream and containing charged particles, of
    which a significant fraction is stopped/degraded in the first detector
    encountered; neutrals would show only a small difference between back
    and front detector;
    - surprisingly, detectors 1 shows much higher shielding factors than
    detectors 2 to 8; again the back detectors have higher shielding factors;
    it would be interesting to identify the path of the background from
    downstream to detectors #1, while #2 - 8 were already better shielded;
    - octant 5, detectors 1-6 or 1-8 appear to violate the front-back rule; the
    individual good/background ratios indicate correct signal wiring;
    octant 5 is at the bottom of the ferris wheel and would be most affected by
    any re-scattering from the Hall-C floor.
    - for detectors 1-12 the less than 50 % of the anode currents are from
    background events after the beam line shielding has been installed
    (not shown in tables; results for the LH2 target will be provided later)

    tables:

    oct det FL FR BL BR
    1 1 1.48 1.52 1.57 1.65
    1 2 1.13 1.16 1.19 1.29
    1 3 1.13 1.19 1.11 1.30
    1 4 1.11 1.11 1.17 1.16
    1 5 1.06 1.08 1.11 1.11
    1 6 1.08(-3.37) 1.11 1.12 FR data problem
    1 7 1.23 1.34 1.36 1.39
    1 8 1.50 1.26 1.50 1.39
    1 9 1.38 (0.86) 1.66 1.64 FR data problem
    1 10 1.55 1.57 1.90 1.88
    1 11 2.00 1.98 2.43 2.32
    1 12 2.40 2.47 2.96 2.88
    1 13 2.89 2.94 3.52 3.56
    1 14 3.18 3.28 3.85 3.85
    1 15 3.15 3.09 3.69 3.71
    1 16 3.05 3.09 3.62 3.54

    3 1 1.37 1.39 1.49 1.48
    3 2 1.07 1.10 1.12 1.14
    3 3 1.06 1.08 1.08 1.16
    3 4 1.06 1.06 1.28 1.26
    3 5 1.05 1.06 1.02 1.05
    3 6 1.10 1.05 1.16 1.12
    3 7 1.10 1.08 1.23 1.25
    3 8 1.20 1.19 1.40 1.30
    3 9 1.34 1.38 1.55 1.59
    3 10 1.57 1.58 1.92 1.30
    3 11 2.03 2.03 2.53 2.47
    3 12 2.42 2.47 3.07 2.98
    3 13 2.74 2.64 3.28 3.21
    3 14 2.98 3.00 3.64 3.54
    3 15 3.23 2.95 3.54 3.50
    3 16 2.86 3.02 3.42 3.51

    5 1 1.64 1.46 1.51 1.30
    5 2 1.27 1.28 1.23 1.19
    5 3 1.33 1.34 1.21 1.24
    5 4 1.13 1.19 1.00 1.09
    5 5 1.18 1.19 1.13 1.12
    5 6 1.23 1.26 1.19 1.20
    5 7 1.37 1.38 1.36 1.37
    5 8 1.45 1.42 1.44 1.48
    5 9 1.53 1.49 1.58 1.61
    5 10 1.73 1.60 2.21 1.92
    5 11 2.15 2.16 2.48 2.32
    5 12 2.51 2.45 2.86 2.83
    5 13 2.76 2.86 3.24 3.27
    5 14 3.09 2.79 3.57 3.51
    5 15 3.08 3.09 3.47 3.50
    5 16 2.93 2.95 3.36 3.37

    7 1 1.35 1.42 1.46 1.65
    7 2 1.01 1.03 1.11 1.14
    7 3 1.09 1.03 1.09 1.08
    7 4 1.12 1.09 1.17 1.17
    7 5 1.12 1.07 1.13 1.05
    7 6 1.06 1.04 1.12 1.10
    7 7 1.11 1.12 1.25 1.23
    7 8 1.17 1.18 1.25 1.30
    7 9 1.33 1.33 1.54 1.52
    7 10 1.49 1.51 1.90 1.81
    7 11 1.98 1.97 2.36 2.34
    7 12 2.40 2.40 3.03 2.96
    7 13 2.75 2.72 3.28 3.35
    7 14 3.13 3.17 3.79 3.78
    7 15 3.14 3.16 3.65 3.68
    7 16 3.09 3.10 3.66 3.59