The ALMA telescope will be an interferometer of 64 antennas, which will be situated in the Atacama desert in Chile. Each antenna will have receivers that cover the frequencies 30 GHz to 970 GHZ. This frequency range is divided into 10 frequency bands. All of these receiver bands are fitted on a cartridge and cooled, with bands 1 and 2 at 15K and the other 8 are SIS receivers at a temperature of 4K. Each band has a dual polarization receiver. The optics has been designed so that the maximum of the optics is cooled to minimize the noise temperature increase to the receivers.
The design of the optics will be shown for each frequency bands. Test results with the method of testing on a near field amplitude and phase measurement system will be given for the first 4 frequency bands to be used, which are bands 3 (84-116 GHz), 6 (211-275GHz), 7 (275-375 GHz and 9 (600-702 GHz). These measurements will be compared with physical optics calculations.
The Atacama Large Millimeter Array (ALMA), a joint project between Europe and the U.S. and at present in its design and development phase, is a major new ground based telescope facility for millimeter and submillimeter astronomy. Its huge collecting area (7000 m2), sensitive receivers and location at one of the driest sites on Earth will make it a unique instrument. We present preliminary design concepts for the overall receiver configuration. Optics and cryostat design concepts from OSO, OVRO, RAL, IRAM, NRAO and SRON and their main features are described.
Heterodyne Multibeam receivers will boost the mapping performances of millimeter and submillimeter telescopes. The IRAM 30 m telescope will be equipped with an 18 channel SIS receiver for frequencies between 210 to 270 GHz. In this paper we discus the receiver system design and give arguments for the specific technological choices and their impacts on various observing modes. The electrical and cryogenic design of the receiver is presented and we discuss the theoretical and experimental performance of the receiver optics.
The integration of many receiver units into a receiver array is a common method of improvement of imaging systems. This approach, well known in the mm band for Schottky mixer arrays, has not so far been developed for Superconductor-Insulator- Superconductor (SIS) junction mixers, which give the best sensitivity in the short mm wave range and in the submm range. We demonstrate for the first time a practical low noise multibeam receiver module using SIS mixer technology. The module comprises three identical SIS mixers integrated with a common local oscillator, coupled through a three branch waveguide directional coupler. The multibeam module has been developed for a focal plane array receiver of the 30 meter radio telescope of the Institut de Radioastronomie Millimetrique (IRAM). Three such modules will be used in a 3 X 3 array operating near 230 GHz frequency. We discuss the requirements on the performance of the multibeam receiver module and compare it with a single beam receiver arrangement. After the presentation of a single mixer receiver operation the performance of the three mixer module is described. The basis for the integration of several SIS mixers with a common local oscillator source is given by the saturation of the SIS receiver noise dependence upon local oscillator power. The 1.3 mm SIS mixer block is built with a reduced height waveguide. The individual SIS junction area is 2.2 micrometer2 with a Josephson critical current density of about 3.6 KA/cm2. The minimum SSB receiver noise temperature at 230 GHz in a single beam receiver is as low as 50 K. In the module a common local oscillator power source is connected to the three mixers through a common three branch directional coupler. The performance of the three mixers is nearly identical across the 200 - 250 GHz band. The minimum DSB receiver noise temperature of 37 K is obtained simultaneously in all three channels around 230 GHz.
The TRAM, Institut de Radio Astronomie Millimetrique, interferometer at the Plateau de Burehas been successfully working for a number of years in the 80-115GHz band with SIS receivers. Itwas decided to increase the frequency range on the four antennas and their efficiencies bysimultaneously covering the 1.3mm frequency band 200-270GHz and the 3mm band,80-115GHz.To do this a different construction of the receiver was required since the size and opticalarrangement of the receiver cabin did not allow a parallel cryostats to be mounted.
For many years TRAM has used PbBi/in-oxide/Pb SIS mixers in the heterodyne receivers for radioastronomy at the telescope installations of Pico Veleta and Plateau de Bure. The frequency coverage of these receivers are (75-115)GHz, (130-180)GHz, and (210-270)GHz. The waveguide mixers, which use Nb/Al-oxide/Nb junctions are subjected to progressive updating. This paper concentrates on the work at (210-270)GHz and (320-370)GHz.
The current systems for making phase and amplitude measurements proposed by the large manufactures in the millimeter range of frequencies are restrictive, in that they only reaches 110GHz, and they is very expensive. Using the H.P. 8510 20Ghz vector analyzer we have managed to make an extension which at present reaches frequencies upto 170GHz with 40 dB dynamic range.