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2009 MAGNET DEVELOPMENT AND INSTRUMENTATIONNew rotating sample holder for broad-band quasi-optical HF-EPRspectroscopyDuring the last year, we have developed and used a newrotating sample holder for single crystal orientation studies.The system was constructed for our broad-band quasiopticalhigh field electron paramagnetic resonance (HF-EPR) spectrometer. For the design, a construction similarto the one of the Fabry-Pérot resonator was used, with themain structure made of Torlon. A simplified scheme of therotating holder attached to a corrugated waveguide is depictedin figure 180 and a photograph of a part of the holderwith a sample is shown in figure 181.The rotating holder relies on a rotating piezoelectricnanopositioner ANRv50 (Attocube systems AG) with a resistiveencoder allowing for an absolute measurement of theangle. The calibrated encoder enables the direct measurementof the position in the range 0 ◦ −337 ◦ . Due to the lackof space in the cryostat, it is not possible to use directly thepiezoelectric element to rotate the sample holder. Thus, agear mechanism had to be introduced, with one gear drivenby the rotating piezoelectric device. The driven gear in turndrives the Teflon holder for the sample. The mechanicalgear is responsible for the main uncertainty in the rotationposition, which is however less than 1 ◦ . A direct use ofthe rotating piezoelectric nanopositioner should decreasethis uncertainty by one order of magnitude (this configurationwill be soon possible with the installation of a newmagnet with a 50 mm bore in the VTI ). A flat gold platedmirror is placed below the sample for the reflection of theMW. A smooth guide having 6 mm inner diameter is usedto propagate the MW from the corrugated taper to the top ofthe gear mechanism, a few millimetres apart from the sample(Fig. 180). A necessary modulation coil for continuouswave EPR is wound directly onto the Torlon housing of therotating sample holder. It has a maximum field amplitudeof 25 G at the sample (with the actual power supply).Figure 180: Scheme of the rotating holder attached to the corrugatedwaveguide. The sample (black point) is placed on a Teflonholder. The gears are driven by the rotating piezoelectric nanopositionerANRv50 (Attocube systems AG) with a resistive encoderallowing an absolute measurement of the angle. The modulationcoils are represented by the crossed area. One part of the holder(dark-gray) is fixed to the corrugated waveguide; the other part(light-gray) with the sample can be dismounted. A photograph ofthis part of the holder is in Fig. 181.Manipulation and loading of the sample are very easy andcomfortable. The holder has two parts. Whereas one partwith the modulation coil is fixed to the corrugated waveguide,the second part with the sample can be easily removedfrom the previous one (Fig. 181). The sample located onthe Teflon holder is accessible as well from the top thanfrom the sides. This construction allows safe manipulationwith the sample under the microscope and eliminates errorswhich can be introduced during the manipulation with thesample.Detailed information for the rotating holder as well asFabry-Pérot resonator can be found in [Neugebauer andBarra, Appl. Magn. Reson. 37, 833 (2009)].Figure 181: Photograph of a part of the rotating holder used fororientation studies of single crystals.P. Neugebauer, J. Florentin and A.-L. Barra127