One of the main goals of the canceled Space Infrared Telescope for Cosmology and Astrophysics (SPICA), was to reveal the evidence of the influence of magnetic field in the structuration of different astrophysical objects, as for example the filamentary structure of star-forming regions. For this purpose, “instrument-in-pixel” detector arrays were developed under ESA, CNES and FOCUS contracts, to propose sensitive, compact and easy to integrate detection solutions for a Space Observatory. Magnetic field influences the light emission or absorption of small grains and molecules imprinting its characteristics in the received electromagnetic message in terms of polarization, degree, angle and intensity. Each pixel of the developed detectors absorb the radiation through two orthogonal dipole networks. The detector array is organized like a chessboard with every other pixel having absorbers rotated by 45° in order to unveil simultaneously the linear Stokes parameters without any optical loss. A very large absorption efficiency is obtained, as usual since PACS detectors, by a backshort-under-grid scheme. To obtain the goal sensitivity of 1 attoW/√Hz, detectors are cooled to 50 mK and linked to an Above IC CMOS readout circuit. For each pixel, four interleaved spiral silicon sensors gather the absorber power. They are organized in a Wheatstone bridge configuration that allows fully differential outputs: total power and polarization unbalanced intensity.
The B-BOP instrument for the SPICA mission will use a brand new generation of submillimeter bolometers.
An ultra-low background testbed for these bolometers has been developed for phase A of ESA. Inside the test cryostat lies a submillimeter light source designed to emit different flux, each of them with the same spectrum, at high temperature. To make sure the light arriving on the bolometers is faint, we use an inversed telescope to dilute the light.
This allowed us to perform the first measurements on bolometer arrays produced by CEA-Leti.
We present the B-BOP instrument, a polarimetric camera on board the future ESA-JAXA SPICA far-infrared space observatory. B-BOP will allow the study of the magnetic field in various astrophysical environments thanks to its unprecedented ability to measure the linear polarization of the submillimeter light. The maps produced by B-BOP will contain not only information on total power, but also on the degree and the angle of polarization, simultaneously in three spectral bands (70, 200 and 350 microns). The B-BOP detectors are ultra-sensitive silicon bolometers that are intrinsically sensitive to polarization. Their NEP is close to 10E-18 W/sqrt(Hz). We will present the optical and thermal architectures of the instrument, we will detail the bolometer design and we will show the expected performances of the instrument based on preliminary lab work.
Several successful development programs have been conducted on Infra-Red bolometer arrays at the French
Atomic Energy Commission (CEA-LETI Grenoble), in collaboration with the CEA-Sap (Saclay); taking
advantage of this background, we are now developing an X-ray spectro-imaging camera for next generation
space astronomy missions, using silicon technology. We have developed monolithic silicon micro-calorimeters
based on implanted thermistors. These micro-calorimeter arrays will be used for future space missions. A 8×8
array prototype consisting of a grid of 64 suspended pixels on SOI (Silicon On Insulator) has been created. Each
pixel of this array detector is made of a tantalum (Ta) absorber and is bonded, by means of an indium bump
hybridization process, to a silicon thermistor. The absorber array is bound to the thermistor array in a collective
process step. The fabrication process of our detector involves a combination of standard silicon technologies
such as Si bulk micromachining techniques, based on deposition, photolithography and plasma etching steps.
Finally, we present the results of measurements performed on the different building elements and processes that
are required to create a detector array up to 32*32 pixels in size.