TWR Calibration Runs 2003




       

Calibration Team: Wolfgang Wagner, Kurt Woschnagg, Jiwoo Nam, Steve Barwick, and special thanks to Matthias and Robert for running the muon-DAQ during calibrations, and special thanks to Azriel for setting up the LED flashers.

Introduction: We use the in situ Nitrogen Laser on String 5 (between OM 35 and 36) to generate bright bursts of light in the ice. We will compare this data to MC data to determine

  1. integrated dynamic range of OM
  2. maximum instanteneous dynamic range (V_max)
  3. corrections to MC simulation of ice properties

We only have 3 in situ N2 lasers in the AMANDA-II array, and the other two lasers are not very useful. The one on the top of the string points up, and so not many OMs see the light. The other one is also at the bottom, approximately the same location as string 5 N2 laser, and known to be not nearly as bright.

The string 5 N2 laser is very bright, so we run it at 8 levels of intensity, starting with no attenuation (ND00) and then attenuating by 3.5 orders of magnitude (Neutral Density Filter ND3.5).

To overcome problems associated with a point source at a given location, we also used the LED flashers on string 18. One important feature of the flashers is that Lisa Gerhardt and Azriel performed absolute calibrations of the light output (see transparencies from Lisa UCB and Stockholm meetings in 2002). We selected 4 locations in depth, nearly uniformly spaced. One disadvantage of the flashers is that the brightness cannot change by very much, typically a factor of 2, sometimes 3. The flashers were run at two different intensities.

Triggering:

  • Flashers: We turned down the HV of the local PMT to ~700V, and discriminated the PMT pulse from the Flasher at 30mV. We ran at 64 Hz, but for the brighter LED run (that that hit >250 OMs), the TWR crashed.
  • N2 laser: The TWR daq had problems with many large events in a single readout of 128 events. It kept crashing. We developed a workaround based on inserting ordinary muon triggers. We adjusted the trigger so that 1/4 were from N2 laser and 3/4 were from muons. We took about 40,000 events in a typical run. Heating the N2 laser generates a lot of noise on string 5 (it is electrical cross-talk so not even turning down the HV on string 5 solved the problem). We took string 5 out of the trigger, but the rates were still in excess of 300 Hz, and we removed string triggers. Finally, we put the M=24 trigger into a gate and adjusted the width (10's ms) so that the trigger rate was reduced to 40-60 Hz.

    • Data: The Flasher runs from last night were put in the same directory as the N2 calibration runs (N2_calib). The data from the TWR daq should be in the usual place on the TWR disk.

    mu-DAQ: calib_data/mudaq_flasher_data
             calib_data/mudaq_laser_data

    twr DAQ:

    File Names (approximate):

    where ndXX corresponds to the neutral density attenuation. Eg., nd15 is neutral density 1.5, of 10^(-1.5).

    The run numbers are

    N2 laser
    ND twr_runnum muonDAQrun
    00 4910 6881
    05 4911 6882
    10 4912 6883
    15 4913 6884
    20 4914 6885
    25 4915 6886
    30 4916 6887
    35 4917 6888
    null 4918 6889

    And the flasher runs

    Flasher run filenames. The first number is the OM on string 18. The second number begins with an "a" which determines the flasher amplitude (or brightness). The number following the f indicates the flasher rate. I did not record that number in my notes (it is either 0 or 1, I think). I denote that number with an X.
    filename_begins twr_runnum muonDAQrun
    flasher_13_a20fX 4921 6892
    flasher_13_a10fX 4922 6894
    flasher_21_a25fX 4925 6896
    flasher_21_a12fX 4926 6897
    flasher_21_a25fX 4927 6898 good run, no VLF
    flasher_29_a20fX 4928 6899
    flasher_29_a12fX 4929 6900 really a10, but file error
    flasher_37_a20fX 4931 6902 (twr-only files .le.0005)
    flasher_37_a10fX 4931 6903 (twr- only files >0005)
    flasher_15_a20fX 4933 6905 double peeak

    Data download: The raw TWR, raw Muon and Merged are availble. Please click here to browse it.


    Steve Barwick 
    Last modified: Feb 13 2003