ALBERT

Description: 〈p〉Publication date: Available online 28 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms〈/p〉 〈p〉Author(s): Benedict Seiferle, Lars von der Wense, Ines Amersdorffer, Nicolas Arlt, Benjamin Kotulski, Peter G. Thirolf〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉〈sup〉229〈/sup〉Th is the only known nucleus with an excited state that offers the possibility for a direct laser excitation using existing laser technology. Its excitation energy has been measured indirectly to be 7.8(5) eV (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.gif" overflow="scroll"〉〈mrow〉〈mo〉≈〈/mo〉〈/mrow〉〈/math〉160 nm). The energy and lifetime of the isomeric state make it the presently only suitable candidate for a nuclear optical clock, the uncertainty of the excitation energy is, however, still too large to allow for a direct laser excitation in a Paul trap. Therefore, a major goal during the past years has been an improved energy determination. One possible approach is to measure the kinetic energy of electrons which are emitted in the internal conversion decay of the first isomeric state in 〈sup〉229〈/sup〉Th. For this reason an electron spectrometer based on a magnetic bottle combined with electrical retarding fields has been built. Its design, as well as first test measurements are presented, which reveal a relative energy resolution of 3 % and thus enable to measure the electrons’ expected kinetic energy to better than 0.1 eV. This is sufficiently precise to specify a laser system able to drive the nuclear clock transition in 〈sup〉229〈/sup〉Th.〈/p〉〈/div〉 〈/div〉