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    User name perdrisat

    Log entry time 22:38:28 on April14,2000

    Entry number 39209

    keyword=log for 16-24 shift

    16:20 beam back, target still cooling down (LH2)
    17:00 Jo Mitchell starts ep measurement; problem with microstrip bias volt.
    17:45 access to hall to check strip bias; Mark Jones goes to fix sector in FPP
    18:30 abort ep measurement. Can not do harp, does not work.
    19:11 start data taking with C; e-sieve slit in, h-coll. open; beam 38 uA
    19:34 start C, open/open run 1492
    note that beam position is off, and MCC is not very successfull at getting it to desired -0.43+1.31 (this run started at +2+2)
    20:10 beam centered. MCC had problems with their screens which weren't reading
    position properly
    20:11 start C open/open again with centered spot
    20:30 start dummy 10 cm runs, runs 1494... 30 uA
    21:30 end dummy run
    move target to 15 cm LH2
    move h-arm to 54.81 deg
    Scheme of increasing beam intensity and prescale factor together, so as to raise data
    rate:
    with 15 uA, prescale 1, event rate is 1750 hz with 26% dt
    30 uA, prescale 2, event rate is 2300 hz with 13% dt
    45 uA, prescale 3, event rate 2000 hz, with 8 % dt
    45 uA, prescale 2, event rate 2600 hz, with 23% dt
    we settle for that, although one could fine tune it further;we have gained factor of 1.5
    on data rate, with increase of beam intensity by factor of 3, with somewhat smaller dt.
    The scheme does work, but it may cost in the long run, as the source crystal efficiency may decrease faster (and the polarization too?). The inventors of this scheme may want to think about the consequences!