Cooled Schottky

The advantage of using a cooled Schottky system is that it could be housed in a separate Dewar with the band 1 receiver (if that is the outcome of other discussions) where it could be cooled to 15 -20 K. The interactions with the more critical part of the receiver system would then be reduced. It would however probably be necessary to undertake a new development to obtain suitable mixers and we are not clear what performance could be obtained. The IF amplifiers would probably play a major role here and it may again be best to use the ALMA 4 to 12 GHz ones. If we decide to use a Dicke switch (see below) then we would probably need to develop a suitable coolable switch. This option should be considered further if detailed planning for a band 1 Dewar is undertaken. Finally in this section, we should note that very compact and relatively cheap refrigerators are now available which could cool a simple radiometer to say 70K. Although reliability might be an issue, it may turn out that this is the most cost-effective way of getting the necessary sensitivity if it cannot be obtained with an uncooled system.