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    User name Saha

    Log entry time 15:34:48 on December 10,1998

    Entry number 8040

    keyword=Beam Energy for Dec 8

    Hall A Beam Energy Determinations _________________________________

    To elaborate on the energy measurements performed on Dec8, there were
    several attempts made to determine the energy of the beam being delivered to
    Hall A, some of which were relative measurements and some absolute.

    Absolute Measurements

    1. Arc Energy measurements - dispersive tune:

    Absolute determinations of angle (with superahrps) and Bdl of arc magnets.

    (a) Magnets cycled for descending loop.

    E = 2581.5 MeV +/- 0.8 MeV (Syst.)

    (b) Magnets cycled for increasing loop.

    E = 2581.4 MeV +/- 0.8 MeV (Syst.)

    (c) After cycling magnets again on increasing loop

    E = 2581.1 MeV +/- 0.8 MeV (Syst.)

    2. An eP energy measurement (non-magnetic):

    E = 2587 MeV +/- 10 MeV (Syst.)

    Note: The large systematic error quoted is due to the fact that only
    one arm was working properly (the scintillator of the other arm was misplaced).
    The eP target held up nicely and did not break even after few hours of beam.

    Relative Measurements

    1. Arc Energy measurements based on BPMs

    Measurements of the relative changes of the arc orbit (with BPMs) with
    reference to a standard setting and Bdl of arc magnets.

    (a) Achromatic mode: E = 2580.52 +/- 0.6 MeV (relative)

    (b) Dispersive mode: E = 2581.52 +/- 0.2 MeV (relative)

    ______________________________________________________________________ Arun Saha (beamel70.dat)