EXO – 200 : ²⁴¹AmBe calibration source

Enriched Xenon Observatory (EXO - 200) is ~175 kg of liquid Xenon experiment for studies on neutrinoless double beta decay. The present gamma calibration is accomplished by ⁶⁰ Co, ¹³⁷ Cs, ²²⁸ Th and ²²⁶ Ra radioactive sources. These sources help to give gamma calibration scale up to 2.6 MeV.

We proposed to deploy a composite neutron source (²⁴¹AmBe) to accomplish several goals. Firstly, it will allow to extend the calibration of gamma energy scale above the existing limit, thanks to mono-energetic 4.43 MeV gamma ray. Secondly, the source will provide better beta energy scale calibration with the help of double escape peak of 4.43 MeV gamma ray. Finally, beta decay of ¹³⁷Xe is one of the primary background contribution in neutrinoless double beta decay search in ¹³⁶Xe. The ²⁴¹AmBe will allow to produce a clean set of ¹³⁷Xe events to validate the energy spectrum and production efficiency used in simulation.

The source was deployed in November 2018. The talk will present first analysis of acquired data. We will particularly discuss the procedure to optimize selection of ¹³⁷Xe decay event sample. Comparison between simulation of neutron activation in the EXO-200 detector and the observed data will also be presented.