P. Cardoni

The BOOMERANG North America Instrument: A Balloon-borne Bolometric Radiometer Optimized for Measurements of Cosmic Background Radiation Anisotropies from 0.°3 to 4°

We describe the BOOMERANG North America instrument, a balloon-borne bolometric radiometer designed to map the cosmic microwave background (CMB) radiation with 0.3degrees resolution over a significant portion of the sky. This receiver employs new technologies in bolometers, readout electronics, millimeter-wave optics and filters, cryogenics, scan, and attitude reconstruction. All these subsystems are described in detail in this paper. The system has been fully calibrated in flight using a variety of techniques, which are described and compared. Using this system, we have obtained a measurement of the first peak in the CMB angular power spectrum in a single, few hour long balloon flight. The instrument described here was a prototype of the BOOMERANG Long Duration Balloon experiment.

A long duration cryostat suitable for balloon borne photometry

Abstract We describe a 4 He cryostat suitable for cooling a large (about 50 l in volume) multiband bolometric photometer for mm-waves. The cryostat features two large optical windows and a hold time longer than 2 weeks. The long hold time has been obtained using a 20 K vapour cooled shield for the liquid helium tank and superinsulation for the nitrogen tank. The tanks are supported by kevlar cords. The cryostat has been optimized for operation on long duration stratospheric balloon flights, and has been tested successfully at ground level and on two short balloon flights.

Balloon-borne 3He cryostat for millimetre bolometric photometry

Abstract A cryostat including a 3 He refrigerator has been designed, built, coupled to a multiband far infrared (FIR) photometer and successfully operated on a balloon flight. Here the cryostat, which is able to cool three bolometers to 0.3 K and one to 1.5 K, is described. The total holding time of the cryostat exceeds 5 days, being limited by exhaustion of the main 4 He and N 2 baths. The autonomy of the 3 He cryostat is more than 50 h, and the recycling time is ≈3 h. The performance of the system in the ARGO 1993 flight is also reported.

DEVELOPMENT OF TWO-STAGE PELLET INJECTORS

Since 1985 a collaboration between the Frascati and Milano Groups has been operating and has been aimed to the realization of a solid D2 pellet injector based on a two-stage light gas gun. Speeds up to 2.9 km/s have been achieved in a reliable performance with unbroken pellets. In this paper a miniaturized version of the injector, to be operated on the Frascati Tokamak, FTU, will be described. Furthermore, developments aimed to obtain the injection of many pellets in rapid succession, still using a two-stage gun, have been initiated and will be described.

A two-stage 3He-4He fridge for bolometric photometry

Abstract We describe the design, construction and performance of a double stage 3 He– 4 He refrigerator, built to cool down a multiband bolometric photometer at the MITO telescope. The fridge was optimized to work without external pumps, with the main cryostat providing a 4.2 K thermostat at sea level and a 4.0 K one at high mountain pressure conditions. The measured ultimate temperature of the fridge is 290 mK, with a hold time of 81 h. The external heat input on the cold flange is ∼35 μW, with the main bath at 4.0 K. The recycle time is 8 h with a heat input on the thermostat during recycling of ∼6800 J. The cryostat can operate without any relevant changes to performance tilted down to 50° from the vertical position, as needed at the telescope focal plane.

HIGH-SPEED PELLET INJECTORS FOR THE FRASCATI TOKAMAK UPGRADE

A completely engineered high-speed single D2 pellet injector (SPIN) has been installed and operated on the Frascati Tokamak Upgrade (FTU). A description of SPIN performance and of the preliminary results obtained by injection of pellets in ohmic discharges is given. Preliminary tests of a multi-shot pellet injector prototype, equipped with eight barrels and eight independent miniaturized two-stage guns are also reported.

Superleak tight aluminium to stainless steel bond

Abstract The connection of an aluminium container to thin walled stainless steel tubes for use in a cryostat is described. The resulting joint showed superleak tightness.

Imaging the early universe with the BOOMERanG Experiment

The BOOMERanG experiment has recently detected temperature fluctuations the Cosmic Microwave Background (CMB), the otherwise isotropic radiation coming from the early Universe. These anisotropies have a low contrast (about 30 ppm) and feature a peculiar angular power spectrum at angles corresponding to sub-horizon scales at recombination. In the current cosmological model, these structures result from acoustic oscillations in the primeval plasma. In the framework of the Hot Big Bang theory with the inflationary hypothesis, the statistical properties of the image of the CMB allow us to measure most of the cosmological parameters.

The Boomerang/ldb Instrument

The BOOMERANG experiment provided the first high resolution map of the Cosmic Microwave Background (CMB) radiation. In this paper we summarize the main parts of the instrument, including bolometers, cryogenics, optics and pointing system. We show then how the instrument is designed to be robust to systematic effects.