4. Technical Reports

4.2 Other IERS Related Technical Development Activities

Milli-meter Wave Receiver Development (Junichi Nakajima)

The new 43GHz receiver have been completed. We employ an SIS device and wideband IF system for high sensitivity observation. The receiver had been installed in the feed system of the Kashima 34m antenna. The cryogenic system test is in progress.

Project status
There are strong requirements to move to higher frequency to achieve high-sensitivity observations and avoid artificial interference. Extension of VLBI technology to mm-wavelength is a very important objective itself. Furthurmore, mm-VLBI capability will enable us to observe new kinds of astronomical sources. The development of mm-wave receiver started in 1993.
The receiver is planned for use in KNIFE (Kashima Nobeyama Intere FErometer) VLBI cooporative observations. We have developed a new compact GM-cryogenic and a cold head offset dewar with Sumitomo Heavy Industries. Without beam transmission waveguide, the 4K cooled receiver is installed in the secondary focus of 34m telescope (Fig.5). The cooling capacity of the cryogenics is 0.4W and is still improving the performance. We have succeed to retain superconductive temperatures in any elevation angle of the telescope.
The recever employs the SIS device produced in Nobeyama receiver group (Fig.6). The received signal is down converted to 5-7GHz wideband IF. This enables high sensitivity observations, accompanied by an ultra high speed acquisition terminal which is being developed. Sensitive observations of QSO relativistic jets, cores and the Galactic center become possible. SiO observation also throw light on the circum stellar radio source nature and sources of extragalactic origin.
Currently, we have carried out the receiver cooling test. Local signal and downconversion system will be equipped successively. After completion of the the electronics, we need to obtain sub-refrector position parameters. Then the KNIFE operation with normal IF band width (0.1-0.6GHz) will be started from April 1995. In 1996 full range GUN-local souce and wideband IF transmission are planned.
This is a joint project of Nobeyama Radio Observatory, Ibaragi University and CRL. The project is partially supported by Nobeyama Radio Observatory.

Figure 5. Photo of the receiver installed in the feed system

Figure 6. Receiver temperature data


Q: Performance of cryogenics is affected by change of the mount angle. How about your system?
A: So far, we get good stability of perfomance with angle change.

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