The KATRIN experiment aims to measure the neutrino mass via precision spectroscopy of the kinetic energy spectrum of tritium beta-decay with a target sensitivity of 0.2 eV/c² at 90% C.L. A high intensity windowless gaseous tritium source is used in conjunction with a high-resolution spectrometer applying the magnetic adiabatic collimation (MAC-E filter) technique to scan the beta-decay spectrum close to its endpoint. The first two KATRIN measurement campaigns led to a mass limit of mν < 0.8 eV (90% C.L.) (Nature Physics 18 (2022) 160). One of the current main sensitivity limitations origins from the plasma systematic which is investigated by using a high-activity 83mKr source. To measure the energy loss function at the energies of the 83mKr N- and L-lines up to 32.17 keV, a new angular-selective monoenergetic photoelectron source which is designed to provide electrons with energies up to 33 keV was built. It was installed in the KATRIN beamline in February 2022. The poster will present commissioning results and characteristics of the new photoelectron source before and after its installation at the KATRIN rear section. We acknowledge the support of Helmholtz Association (HGF); Ministry for Education and Research BMBF (05A17PM3, 05A17PX3, 05A17VK2, 05A17PDA, 05A17WO3, 05A20VK3, 05A20PMA and 05A20PX3); Helmholtz Alliance for Astroparticle Physics (HAP); the doctoral school KSETA at KIT; Helmholtz Young Investigator Group (VH-NG-1055); Max Planck Research Group (MaxPlanck@TUM); Deutsche Forschungsgemeinschaft DFG (Research Training Group grant nos. GRK 1694 and GRK 2149); Graduate School grant no. GSC 1085-KSETA and SFB-1258 in Germany; Ministry of Education, Youth and Sport (CANAM-LM2015056, LTT19005) in the Czech Republic; the Department of Energy through grants DE-FG02-97ER41020, DE-FG02-94ER40818, DE-SC0004036, DE-FG02-97ER41033, DE-FG02-97ER41041, DE-SC0011091 and DE-SC0019304; and the Federal Prime Agreement DE-AC02-05CH11231 in the USA. This project has received funding from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation programme (grant agreement no. 852845). We thank the computing cluster support at the Institute for Astroparticle Physics at Karlsruhe Institute of Technology, Max Planck Computing and Data Facility (MPCDF), and National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.