Radioastronomy Instrumentation for Herschel and APEX Projects

Doktorsavhandling, 2006

This thesis presents work done in developing instrumentation for sub-mm radio astronomy projects. The first part covers Gaussian beam measurements for the Heterodyne Instrument for Far- Infrared (HIFI) of the Herschel Space Observatory project by the European Space Agency. The beam measurement setup accommodates the probe source and the device under test entirely in vacuum. Advanced scalar measurement technique together with the developed computational routines allows characterization of the beam parameters with an accuracy of 250 µm in the beam waist coordinates and 0,1degree in beam axis tilt. The same method was employed to perform beam measurements for the First Light 345 GHz receiver of APEX telescope. Harmonic mixer placed on x, y, z scanner was used as a test source to measure the receiver beam parameters. As a result, an initial beam offset was corrected by a couple of iterative measurements and the mirrors inside the cryostat were shimmed to compensate the tilt of the beam. The second part of the thesis describes the unique triangulation system, which was developed to allow Gaussian beam measurements related to a mechanical reference integrated into the tested receiver of HIFI. This part also deals with the approach used to align the sub-millimeter optics of APEX first Light receiver using visible laser light and position sensitive detectors. The third part of the thesis covers the design, fabrication and measurement of a balanced Hot Electron Bolometer Mixer for the 1.25-1.39 THz band employing NbN bolometer device. Novel fabrication techniques were used for manufacturing of the mixer horn and the input waveguide hybrid.