JCMT Newsletter No. 13 (MPI 800 GHz)
 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 October/November 1999. 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
Observers interested in using it should contact Dr. Ronald Stark
(stark@mpifr-bonn.mpg.de) to
arrange collaborative efforts.
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.
Modification Author: Graeme Watt (gdw)
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