Atacama Pathfinder EXperiment APEX
MPIfR Bonn   ESO   Onsala Space Observatory

Home > Instrumentation > SHeFI receivers

The Swedish Heterodyne Facility Instrument

Instrument overall view Example of mixer assemly (APEX-2)
Instrument overall view
Example of mixer assembly (APEX-2)


The Swedish Heterodyne Facility Instrument (SHeFI) was built by the GARD group at the Chalmers University, Sweden, with the Onsala Space Observatory. A SHeFI webpage which may contain complementary information is maintained there. The SHeFI consists of four wideband heterodyne receiver channels for 230 GHz (APEX-1), 345 GHz (APEX2), 460 GHz (APEX-3), and 1300 GHz (APEX-T2). All the bands are located inside a single closed-cycle cryostat which maintains the coldest part at a temperature close to 4 K. The first three bands for 230, 345, and 460 GHz employ superconductor-insulator-superconductor (SIS) mixers and behave as single sideband receivers (SSB). The 1.3 THz band is built using hot electron bolometer (HEB) mixer technology and is a double sideband receiver (DSB).

The Cryostat/Cryogenics

The SHeFI receiver is located in the Nasmyth-A cabin of the telescope. The optical path is fairly complex and includes not less than 11 mirrors including the main dish and the subreflector. The SHeFI receiver support structure is firmly attached to the Nasmyth elevation tube flange and therefore temperature deformations of the A cabin have little effect on the receiver alignment.

The cryostat was built at the Chalmers University and uses a closed-cycled Sumitomo cooling machine providing temperatures at the coldest stage below 4 K, which is needed for the best operations of the superconduting mixers.

It is only possible to use one receiver band at a time. A rotating mirror selects the desired band. Therefore, there is only one intermediate frequency (IF) cable going to the backends (XFFTS and total power). The switching time from one band to another takes less than 5 minutes, temperature stabilization of LO chain and mixer block included. These heterodyne instruments all use for the local oscillator (LO) injection, direct multiplication chains. The reference signal comes from an HP signal generator providing a strong clean signal from 10-20 GHz.

Receiver bands

Instrument Type Mode Frequency [GHz] HPBW [arcsec] IF range [GHz] # of beams Location Status Comment
APEX-1 (SHeFI) Heterodyne SIS SSB 213 - 275 30 - 23 4 - 8 1 Nasmyth-A ok
APEX-2 (SHeFI) Heterodyne SIS SSB 267 - 378 23 - 17 4 - 8 1 Nasmyth-A ok
APEX-3 (SHeFI) Heterodyne SIS DSB 385 - 506 17 - 13 4 - 8 1 Nasmyth-A not ok
APEX-T2 (SHeFI) Heterodyne HEB DSB 1250 - 1390 5 2 - 4 1 Nasmyth-A not ok Science Verification pending

Observing modes and patterns

Switch modes

Observing patterns

Time estimator

To obtain an observing time estimate in ON/OFF observation mode for all bands use this calculator. More information concerning observing time calculations can be found here.
To obtain an observing time estimate in On The Fly observation mode for all bands use this calculator.


Currently, information about SHeFI Calibration is somewhat distributed in our web presentation. The following topics may be of interest: