T-452 Tower PMT Response

The picture below shows accumulated digital oscilloscope traces for several SLAC pulses. The electron beam energy for these events is 20 GeV. The beam intensity is adjusted so that on average approximately three 20 GeV electrons arrive in the 1 ps wide pulse. The time scale on the oscilloscope is 50 ns/division. The vertical scale on the oscilloscope is 200 mV/division. The traces show the output from the ETL 9107 PMT, when operated at 780 V delivered by a Cockcroft-Walton base, after 160 ns of RG-58 cable.

The picture below shows accumulated digital oscilloscope traces for another set of SLAC pulses.  The oscilloscope time scale is set to 20 ns/division for this picture.  Otherwise, the setup is identical to the picture above.

The encoding of the ETL 9107 current pulse was accomplished using LeCroy 4300B ADC (FERA). The current pulse was split after a 160-ns RG-58 delay line by a 50 Ohm impedance matched T, and half of the pulse was sent to the Lecroy 4300B gated by a 200 ns wide pulse. The resulting ADC spectra for 5, 10 and 20 GeV electron energies incident on tower 6 of the calorimeter is shown in the figure below.

The distributions are not corrected for a small pedestal drift that was present for the three different runs. When the pedestal correction is made, the calorimeter response if found to be linear. The energy resolution is found to be 18%/sqrt(E).

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L.C. Bland (IUCF), for the T-438 collaboration

Last revised: 31 October 1999