GUBBINS

GUBBINS is a novel heterodyne interferometer currently under construction in Oxford that will both measure the spectrum of Sunyaev-Zel'dovich effect in the brightest galaxy clusters and provide a test-bed for future developments from our new-technology program. The project was fully designed and manufactured in the mechanical group and the use of a modular Newport motors and controllers makes a control system very easy to develop.

The project had a variety of design challenges. To make a good interferometer the mirrors must track across the sky together pointing to an accuracy of 1 arc minute so very rigid drives and careful finite element modelling of deflections were required. The temperature inside the cryostat is below 10K and so great care had to be taken with the insulation and to maintain accurate thermal budgets dominated by radiation which is difficult to model. Controlling the temperature of each component and ensuring good heat transfer within the cryostat was one of the major development challenges. The device was designed to be portable and to be used at very high altitude so it needed be robust (as it will be assembled and disassembled) but light. The system has a complicated optical pathway with 5 parabolic reflecting surfaces and 3 bolometers in each chain both entering and leaving a very low temperature space so a great deal of care was required designing for thermal effects and also providing the adjustment necessary so as not to overspecify the manufacturing tolerances.