Max-Planck-Institut 800 GHz Instrument

RxE is a single-channel quasi-optical SIS receiver for operation in the 350 micron atmospheric window (E-band). Among the most important lines available in this window are the transitions of CO J=7-6 [807 GHz], [CI] 3P2-3P1 [809 GHz], HCO+ J=9-8 [802 GHz], and HCN J=9-8 [797 GHz].

The receiver has been designed and constructed at the MPIfR in Bonn. The SIS mixer employs a Nb-(Al-oxide)-Nb junction produced in collaboration with IRAM in 1994. The LO system consists of an InP Gunn-oscillator followed by a doubler and a tripler stage which covers the frequency range 795 - 880 GHz. The cooled IF section consists of a 3 stage 2.5 - 4 GHz HEMT amplifier.

The receiver was successfully tested in the winters 1997/1998 at the 10m HHT on Mt. Graham. A DSB receiver noise temperature of 680 K was measured at 809 GHz. Continuum scans across Mars yielded a FWHP main beam width of 9" which is well matched to the diffraction limit. No evidence for side lobes or broad pedestal structure was found at a level of 10 - 13 dB.

The heterodyne response was demonstrated using the CO J=7-6 transition measured toward IRC+10216. The resulting spectrum is shown on the web page. The integration time was 180 sec, the data was taken under poor and unstable atmospheric conditions.

The system is currently being upgraded in Bonn and is scheduled for installation and commissioning at the JCMT in April 2000. After successful commissioning the instrument will be on loan from Prof. Rolf Gusten and his group at MPIfR and available for use by the JCMT community on a collaborative basis.

Further details can be found at:

http://www.mpifr-bonn.mpg.de/div/mm/tech/rxe.html

The double sideband (DSB) receiver temperature over the E-band is expected to be in the range 700 - 800 K. Only DSB operation will be possible. The maximum available bandwidth for the DAS is currently 920 MHz. The single-sideband system temperatures are expected to be around 10,000 K or less under good submillimetre weather conditions (weather band 1 = CSO(tau) < 0.05). Observers are advised to use these numbers to estimate required observing times.

The performance at the JCMT will only be known after the commissioning, but before the TAGS meet. Therefore, the actual numbers can be retro-fitted in the proposals prior to the final allocation meeting at ITAC in early December.