Exploring vacuum phototriodes for photon calorimetry

• In this work properties of a vacuum phototriode (VPT) and preamplifier unit designed for the electromagneticcalorimeter of the PANDA experiment being built at FAIR are investigated. With the use of leadtungstate and lanthanum bromide scintillators the VPT properties are studied at low photon energies, fromtens of keV in the lanthanum bromide measurements and between 10 MeV and 60 MeV in the lead tungstatemeasurements. At these energies the noise of the VPT unit can be expected to influence its performancesignificantly. It is shown that the noise contribution to the measured energy resolution, under optimal conditions,is consistent with a fluctuation of (one standard deviation) approximately 200 electrons at the VPTanode. For a lead tungstate crystal this is equivalent to a noise of 1.2 MeV. For lanthanum bromide thismakes it possible to use VPTs for gamma ray spectroscopy above a few hundreds of keV without noticableeffects on the energy resolution compared to measurements with a standard photomultiplier. The gain sensitivityto rate is shown to be small. The gain changes by less than 1.5 % for a rate of 2105 s−1 comparedto low rates.

Ämnesord

NATURVETENSKAP  -- Fysik -- Acceleratorfysik och instrumentering (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Accelerator Physics and Instrumentation (hsv//eng)

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