Electron spin resonance measurements for the Bonn polarized target

Electron Spin Resonance (ESR) Measurements have been an important tool in investigating polarized target materials since the beginning of polarized targets research. The paramagnetic centres that are important for the Dynamic Nuclear Polarization (DNP) can be examined by ESR. The ESR-lineshape is influenced by interactions with surrounding nuclei. These interactions are responsible for DNP, too. Therefore ESR-studies can improve the knowledge of polarization mechanisms. ESR-studies may become important in future when radiation doping of new samples is to be tested. This work describes the basic theory of ESR and the effects that influence the ESR lineshape. Afterwards, a new 4He-1 Kelvin ESR-apparatus is described which has been tested with two different samples. In this apparatus, the ESR-lineshape can be detected by a Lock-In-Amplifier and a microwave detector in addition to the common detection method with bolometer. This new feature improves the resolution of ESR-measurements. (orig.)