LEGEND is one of the leading experiments in the search for neutrinoless double-beta (0νββ) decay. With its second phase, LEGEND-1000, the experiment uses one ton of germanium crystals enriched in ⁷⁶Ge to reach a discovery potential of half-lives greater than 10²⁸ years.
However, to reach this sensitivity, an extremely low background level of 10⁻⁵ cts/(keV kg yr) at Q_ββ is necessary. One step towards this goal is to minimize the radioactivity of all components and to classify them with material screening methods.
We report on our recent efforts in developing alpha spectrometry with improved sensitivity beyond commercial low background solutions. Using an Frisch-gridded ionization chamber offers a high resolution and allows an analysis on individual radionuclides of one decay chain. In addition, we are sensitive to surface contaminations of less than 0.5 mBq/m² for ²³⁸U and ²³²Th. This presentation will show the optimization of the energy resolution, efforts in background reduction and first screening measurements with test samples.
This work is supported by: U.S. DOE, NSF, LANL, ORNL and LBNL LDRD programs; European ERC and Horizon programs; German DFG, BMBF, and MPG; Italian INFN; Polish NCN and MNiSW; Czech MEYS; Slovak RDA; Swiss SNF; UK STFC; Canadian NSERC and CFI; LNGS and SURF facilities.