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    User name X. Zheng

    Log entry time 18:08:29 on June18,2001

    Entry number 63699

    keyword=Laser Work during Maintaince

    From 2pm to 5pm today, Jian-Ping, Kevin and I did a few laser tests:

    (1) Adjust set diode temperature to optimize wavelength profile with new 50um fiber:

    Coherent #, original T, I, adjusted T
    1, 16.0C/17.0C, 38A, 13.0C/14.0C
    2, 22.7C/29.6C, 37A, 20.5C/21.3C
    3, 26.0C/26.8C, 40A, 26.0C/26.8C
    4, 15.0C, 40A, same 15.0C
    5, 18.1C, 36.5A, 16.6C
    6, 13.5C, 40A, 12.9C/12.5C
    7, 18.5C/18.5C, 36A, 19.5C/19.4C -> 19.3C **

    * Temperature is listed as set/readout.
    ** Temperature of #7 has been adjusted twice.

    (2) Measure set temperature vs. power for Coherent #5.
    If we need to add the 4th longitudianl laser, then might need half power. This measurement is aimed to find the best temperature setting for low power:

    Coherent #5
    power, I(A), T
    30W, 36.5A, 16.6C
    25W, 31.6A, 20.0C/19.7C
    20W, 26.4A, 23.5C/23.1C
    15W, 21.2A, 26.5C/26.0C
    10W, 16.4A, 29.0C/28.5C
    30W, 36.5A, 17.5C/17.4C

    around 5pm the second adjustment set T=17.0C @ 30W, 36.5A

    (3) Check half waveplates:
    During the last 2 days' data taking it has been found that target polarization dropped from 37% @ 0 degree to 35% @ 180 degrees. It is possible that the orientation of half waveplates is not correct. Since we do not have any instrument to test waveplate axis, we used spectral analyzer, optimized orientation by minimizing the height of wavelength spectrum.

    Original:
    slot#-left# - angle reading
    7-28 - 50 degree
    6-32 - 40 degree
    5-26 - 48 degree
    4-25 - 33 degree

    right# - angle reading
    7-27 - 50 degree
    6-31 - 60 degree
    5-30 - 38 degree
    4-29 - 45 degree

    Original:
    slot#-left# - angle reading
    7-28 - 64 degree
    6-32 - 54 degree
    5-25 - 46 degree
    4-26 - 58 degree

    slot#-right# - angle reading
    7-29 - 60 degree
    6-31 - 78 degree
    5-30 - 49 degree
    4-27 - 54 degree

    The angle setting is in average 12 degrees off from the test result in EEL lab. It is possible that EEL lab test was not done properly. Let's wait for the polarization measurement.