The BGO calorimeter was loaned for the 2015 run from Aarhus university as part of the NA63 equipment. It is a Scionix type 76B200 / 3M-E2-BGO-X with a $\oslash 76\,\mathrm{mm} \times 200\,\mathrm{mm}$ BGO crystal (see: for drawing and for model number). It is encased in an $0.5\,\mathrm{mm}$ Aluminium housing with a reflector surrounding the crystal. 3M refers to a 3 inch diameter PMT with external mu-metal shield. E2 indicates a built in Voltage divider / pre-amplifier. X indicates some customisation.


The BGO used in 2015 can take up to +1140V. In practice, its gain at ~480V is more appropriate. Note positive polarity!


The PMT has an on-board pre-amplifier that requires 12V in a two pole LEMO cable. The output is fed into a nearby amplifier. Since the BGO produces long pulses ($\sim70\,\mathrm{\mu s}$), the readout digitises the pulse height. The CAEN v785 peak sensing ADC was used in 2015.


The Zero point was taken using the v785 pedestal with the BGO HV on. Muons can be observed ~100MeV - a dedicated run to test this was taken by triggering from the BGO. Electrons can be directly sent into the BGO to measure the response at the beam energy.

The Aarhus team calibrated at low energy using an AmBe source, looking at 4.439 MeV photons.


-- TimBrooks - 2015-09-07

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Topic revision: r2 - 2015-11-20 - TimBrooks
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