In the last decades, a very large effort has been made to measure, with high sensitivity, the intensity and spectral contents of millimetric (mm) and submillimetric (submm) light from the Universe. Today this picture is in the way to be routinely completed by polarization measurements that give access to previously hidden processes, for example the traces of primordial gravitational waves in the case of CMB (mainly mm), or the effect of magnetic field for star formation mechanisms (submm and mm optical ranges).
The classical way to measure the light polarization is to split the two components by a polarizer grid and record intensities with two conjugated detection setups. This approach implies the deployment of a complex instrument system, very sensitive to external constraints (vibrations, alinement, thermal expansion…), or internal ones: determine low degrees of polarization implies a large increase in sensitivity when compared with intensity measurements.
The need of detector arrays, with in pixel polarization measurement capabilities, has been well understood for years: all the complexity being reported at the focal plane level. Subsequently, the instrument integration, verification and tests procedure is considerately alleviated, specially for space applications.
All silicon bolometer arrays using the same micromachining techniques than the Herschel PACS modules are well suited for this type of development. New thermometers doped for 50 mK operations permit to achieve, with a new design, sensitivities close to the aW/√Hz. It is based on all-legs bolometers (ALB), where the absorbing, insulating and thermometric functions are made by the same suspended silicon structure. This ALB structure, with in this case a spiral design, permits to separate the absorption of the two electromagnetic components of the light polarization. Each pixel consists of four bolometer divided in two pairs, each sensitive to one direction of polarization. This permits to combine the bolometer bridges in a fully differential global structure with a Wheatstone bridge arrangement. Total intensity and polarization unbalance are available directly at the detector level, thanks to a cold readout circuit integrated in the detector structure. This combination of functions is achieved by above IC manufacture techniques (IC for Integrated Circuit).
All these developments take place in the prospect of the joint JAXA-ESA SPICA project, to equip a 1344 pixels polarimetric and imaging camera covering three spectral bands (100, 200 and 350 µm).
Since the development of the instrument PACS on the HERSCHEL space observatory, the silicon bolometers technology is well understood and handled at CEA. Our pixels are based on a well-known concept of electromagnetism: the absorber closes a quarter-wave cavity which allows to get maximal absorption at the corresponding wavelength. In the frame of the SPICA mission and more precisely for the SAFARI-pol instrument, we have designed and manufactured new absorbers with a different pattern that enables detectors to be sensitive to the polarization. In this way, the measurement of the polarized (sub)millimeter radiation is directly performed within the pixel. Similarly, we want to introduce a spectroscopic capacity inside the chip. In this talk, we will present the interferometric system that has been designed to fulfill the spectroscopic requirements of a space mission. The physics on which rely the interferences of multiple waves inside the detector will be largely developed. In the last part, we will describe the inverse process that follows the data acquisition, and will be carried out from the spectrometer chip characterization. The final aim of this research is to pave the way to bolometer focal planes with polarimetry and spectroscopy capabilities inside the detectors.
CEA has a long history of customizing optoelectronic components for space and astronomy applications. Based on this expertise, we are undertaking the development of cooled silicon bolometers for millimetre-wave (mm-wave) polarization detection in the next generation of space astronomy missions such as SPICA. Silicon bolometer technology has been demonstrated successfully in space conditions through the Herschel mission. There are many benefits of this technology such as the use of a simple and low-power read-out circuit that can be integrated below the detector array in an above-IC (Integrated Circuit) integration scheme. The advanced integration in a large array and the fabrication process based on microelectronics techniques are key challenges for these developments. This work presents the early results on the design, the fabrication and the first characterization of an innovative pixel for mm-wave polarization detection. The aim is to have an adapted absorption around λ=1.5 mm. These bolometers are composed of an absorbing layer and a thermometer, which are thermally insulated from the substrate. To increase the sensitivity, these detectors are working at very low temperature typically between 50 and 100 mK. The suspended thermometer is made of silicon implanted with Phosphorus and Boron species, and we optimized the design to have a high sensitivity with a 3D Variable Range Hopping conduction (Efros law) and a low 1/f noise at low temperature. The heat capacity of the bolometer is optimized by using a meander shape of the thermometer together with superconducting Ti/TiN thin films for the electromagnetic wave absorption. This sensor is implemented on a standard SOI substrate. Measurements of test structures at room temperature, and first results at very low temperature have been performed to evaluate the electrical performances of the fabricated detectors. The mechanical behaviour of released structures, including pixels with a pitch of 1200μm and 600μm, is presented and discussed.
We present the latest results obtained with the wide-field submillimeter camera ArTeMiS that is operating on APEX since July 2013. This camera is presently equipped with 1870 pixels at 350 μm and 800 pixels at 450 μm simultaneously. ArTéMiS is a PI-camera open to the ESO and Swedish community. It has already taken a part in the 2016-2017 scientific results of APEX. So far, it offers the best performance in terms of mapping speed at 350 and 450 μm in the southern hemisphere. <p> </p>Major improvements of the APEX telescope have been achieved at the end of 2017, requiring a complete removal of the instruments in the C-Cabin. In the meantime, the ArTeMiS camera has been kept safe at the ALMA Operations Support Facility (OSF) building. We took advantage of this re-installation to improve a bit more the optical coupling of detectors. We present here the present status of the camera. <p> </p>Since APEX operation is now guaranteed until the end of 2022, our prospects are to install in time new detectors presently developed at CEA/Léti in the frame of R&D developments made for the future SPICA space mission. Those detectors, which have new polarization capabilities, are also presented.
TALC, Thin Aperture Light Collector is a 20 m space observatory project exploring some unconventional optical solutions (between the single dish and the interferometer) allowing the resolving power of a classical 27 m telescope. With TALC, the principle is to remove the central part of the prime mirror dish, cut the remaining ring into 24 sectors and store them on top of one-another. The aim of this far infrared telescope is to explore the 600 μm to 100 μm region. With this approach we have shown that we can store a ring-telescope of outer diameter 20m and ring thickness of 3m inside the fairing of Ariane 5 or Ariane 6. The general structure is the one of a bicycle wheel, whereas the inner sides of the segments are in compression to each other and play the rule of a rim. The segments are linked to each other using a pantograph scissor system that let the segments extend from a pile of dishes to a parabolic ring keeping high stiffness at all time during the deployment. The inner corners of the segments are linked to a central axis using spokes as in a bicycle wheel. The secondary mirror and the instrument box are built as a solid unit fixed at the extremity of the main axis. The tensegrity analysis of this structure shows a very high stiffness to mass ratio, resulting into 3 Hz Eigen frequency. The segments will consist of two composite skins and honeycomb CFRP structure build by replica process. Solid segments will be compared to deformable segments using the controlled shear of the rear surface. The adjustment of the length of the spikes and the relative position of the side of neighbor segments let control the phasing of the entire primary mirror. The telescope is cooled by natural radiation. It is protected from sun radiation by a large inflatable solar screen, loosely linked to the telescope. The orientation is performed by inertia-wheels. This telescope carries a wide field bolometer camera using cryocooler at 0.3K as one of the main instruments. This telescope may be launched with an Ariane 6 rocket up to 800 km altitude, and use a plasma stage to reach the Lagrange 2 point within 18 month. The plasma propulsion stage is a serial unit also used in commercial telecommunication satellites. When the plasma launch is completed, the solar panels will be used to provide the power for communication, orientation and power the cryo-coolers for the instruments. The guide-line for development of this telescope is to use similar techniques and serial subsystems developed for the satellite industry. This is the only way to design and manufacture a large telescope at a reasonable cost.
ArTeMiS is a wide-field submillimeter camera operating at three wavelengths simultaneously (200, 350 and 450 μm). A preliminary version of the instrument equipped with the 350 μm focal plane, has been successfully installed and tested on APEX telescope in Chile during the 2013 and 2014 austral winters. This instrument is developed by CEA (Saclay and Grenoble, France), IAS (France) and University of Manchester (UK) in collaboration with ESO. We introduce the mechanical and optical design, as well as the cryogenics and electronics of the ArTéMiS camera. ArTeMiS detectors consist in Si:P:B bolometers arranged in 16×18 sub-arrays operating at 300 mK. These detectors are similar to the ones developed for the Herschel PACS photometer but they are adapted to the high optical load encountered at APEX site. Ultimately, ArTeMiS will contain 4 sub-arrays at 200 μm and 2×8 sub-arrays at 350 and 450 μm. We show preliminary lab measurements like the responsivity of the instrument to hot and cold loads illumination and NEP calculation. Details on the on-sky commissioning runs made in 2013 and 2014 at APEX are shown. We used planets (Mars, Saturn, Uranus) to determine the flat-field and to get the flux calibration. A pointing model was established in the first days of the runs. The average relative pointing accuracy is 3 arcsec. The beam at 350 μm has been estimated to be 8.5 arcsec, which is in good agreement with the beam of the 12 m APEX dish. Several observing modes have been tested, like “On- The-Fly” for beam-maps or large maps, spirals or raster of spirals for compact sources. With this preliminary version of ArTeMiS, we concluded that the mapping speed is already more than 5 times better than the previous 350 μm instrument at APEX. The median NEFD at 350 μm is 600 mJy.s1/2, with best values at 300 mJy.s<sup>1/2</sup>. The complete instrument with 5760 pixels and optimized settings will be installed during the first half of 2015.
ArTeMiS is a submillimeter camera planned to work simultaneously at 450 μm, 350 μm and 200 μm by use of 3 focal planes of, respectively, 8, 8 and 4 bolometric arrays, each one made of 16 x18 pixels. In July 2013, with a preliminary setting reduced to 4 modules and to the 350 μm band, ArTeMiS was installed successfully at the Cassegrain focus of APEX, a 12 m antenna located on the Chajnantor plateau, Chile. After the summary of the scientific requirements, we describe the main lines of the ArTeMiS nominal optical design with its rationale and performances. This optical design is highly constrained by the room allocation available in the Cassegrain cabin. It is an all-reflective design including a retractable pick off mirror, a warm Fore Optics to image the focal plane of the telescope inside the cryostat, and the cold optics. The large size of the field of view at the focal plane of the telescope, 72 mm x 134 mm for the 350 μm and 450 μm beams, leads to the use of biconical toroidal mirrors. In this way, the nominal image quality obtained on the bolometric arrays is only just diffraction limited at some corners of the field of view. To keep a final PSF as much uniform as possible across the field of view, we have used the technic of manufacturing by diamond turning to machine the mirrors. This approach, while providing high accuracy on the shape of the mirrors, made easier the control of the two sub units, the Fore Optics and the cold optics, in the visible domain and at room temperature. Moreover, the use of the similar material (Aluminium alloy 6061) for the optical bench and the mirrors with their mount ensures a homothetic shrinking during the cooling down. The alignment protocol, drew up at the early step of the study, is also presented. It required the implementation of two additional mechanisms inside the cryostat to check the optical axis of the cold optics, in the real conditions of operation of ArTeMiS. In this way, it was possible to pre-align the Fore Optics sub unit with respect to the cold optics. Finally, despite the high constraints of the operating conditions of APEX, this protocol allowed to align ArTeMiS with respect to the telescope in a single adjustment. The first images obtained on the sky, Saturn with its rings, are given.
The New IRAM KID Array (NIKA) is a dual-band camera operating with frequency multiplexed arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) cooled to 100 mK. NIKA is designed to observe the intensity and polarisation of the sky at 1.25 and 2.14 mm from the IRAM 30 m telescope. We present the improvements on the control of systematic effects and astrophysical results made during the last observation campaigns between 2012 and 2014.
APEX, the Atacama Pathfinder EXperiment, is being operated successfully, now for five years, on Llano de Chajnantor
at 5107m altitude in the Chilean High Andes. This location is considered one of the worlds outstanding
sites for submillimeter astronomy, which the results described in this contribution are underlining. The primary
reflector with 12 m diameter is cautiously being maintained at about 15 μm by means of holography. This
allows to access all atmospheric submillimeter windows accessible from the ground, up to 200 μm. Telescope and
instrument performance, operational experiences and a selection of scientific results are given in this publication.
The 6 K cooled primary mirror of the SPICA observatory, to be launched in 2018, allows a photometry gain in
sensitivity in the far infrared of more than two orders of magnitude when compared with current instrumentation in
space. All the proposed detector solutions will have to deploy radically different solutions from previous developments
to cope with the extremely low background and very low power budgets available at all the temperature stages. We
present the current design of very large "all Silicon" filled Bolometer Arrays cooled below 100 mK, and the solutions we
develop for the BASIC (Bolometer Arrays for the All Silicon SAFARI Imaging Camera) focal planes of SAFARI. They
will cover simultaneously three wavelength bands between 30 and 210 μm.
The ArTeMiS submillimetric camera will observe simultaneously the sky at 450, 350 and 200 μm using 3 different focal
planes made of 2304, 2304 and 1152 bolometric pixels respectively. This camera will be mounted in the Cassegrain
cabin of APEX, a 12 m antenna located on the Chajnantor plateau, Chile.
To realize the bolometric arrays, we have adapted the Silicon processing technology used for the Herschel-PACS
photometer to account for higher incident fluxes and longer wavelengths from the ground. In addition, an autonomous
cryogenic system has been designed to cool the 3 focal planes down to 300 mK. Preliminary performances obtained in
laboratory with the first of 3 focal planes are presented.
Latest results obtained in 2009 with the P-ArTeMiS prototype camera are also discussed, including massive protostellar
cores and several star forming regions that have been clearly identified and mapped.
ArTeMiS is a camera designed to operate on large ground based submillimetric telescopes in the 3 atmospheric windows
200, 350 and 450 µm. The focal plane of this camera will be equipped with 5760 bolometric pixels cooled down at 300
mK with an autonomous cryogenic system. The pixels have been manufactured, based on the same technology processes
as used for the Herschel-PACS space photometer. We review in this paper the present status and the future plans of this
A prototype camera, named P-ArTeMiS, has been developed and successfully tested on the KOSMA telescope in 2006 at
Gornergrat 3100m, Switzerland. Preliminary results were presented at the previous SPIE conference in Orlando (Talvard
et al, 2006). Since then, the prototype camera has been proposed and successfully installed on APEX, a 12 m antenna
operated by the Max Planck Institute für Radioastronomie, the European Southern Observatory and the Onsala Space
Observatory on the Chajnantor site at 5100 m altitude in Chile. Two runs have been achieved in 2007, first in March and
the latter in November. We present in the second part of this paper the first processed images obtained on star forming
regions and on circumstellar and debris disks. Calculated sensitivities are compared with expectations. These illustrate
the improvements achieved on P-ArTeMiS during the 3 experimental campaigns.
A new kind of bolometric architecture has been successfully developed for the PACS photometer onboard the Herschel submillimeter observatory. These new generation CCD-like arrays are buttable and enable the conception of large fully sampled focal planes. We present a feasibility study of the adaptation of these bolometer arrays to ground-based submillimeter telescopes. We have developed an electro-thermal numerical model to simulate the performances of the bolometers under specific ground-based conditions (different wavelengths and background powers for example). This simulation permits to determine the optimal parameters for each condition and shows that the bolometers can be background limited in each transmission window between 200 and 450 microns. We also present a new optical system that enables to have a maximum absorption of the bolometer in each atmospheric windows. The description of this system and measurements are shown.
Astronomical observations at sub-millimetre wavelengths are limited either by the angular resolution of the telescope or
by the sensitivity and field of view of the detector array. New generation of radio telescopes, such as the ALMA-type
antennas on Chajnantor plateau in Chile, can overcome these limitations if they are equipped with large detector arrays
made of thousands of sensitive bolometer pixels.
Instrumentation developments undertaken at CEA and based on the all silicon technology of CEA/Leti are able to
provide such large detector arrays. The ArTeMiS project consists in developing a camera for ground-based telescopes
that operates in two sets of atmospheric windows at 200-450 μm (channel 1) and 800-1200 μm (channel 2).
ArTeMiS-1 consists in grid bolometer arrays similar to those developed by CEA for the <i>Herschel</i> Space Observatory. A
prototype camera operating in this first atmospheric window was installed and successfully tested in March 2006 on the
KOSMA telescope at Gornergrat (Switzerland) in collaboration with the University of Cologne. ArTeMiS-2 will consist
either in antenna-coupled bolometer arrays or specific mesh bolometer arrays.
By the end of 2008, ArTeMiS cameras could be operated on 10m-class telescopes on the Chajnantor ALMA site, e.g.,
APEX, opening new scientific prospects in the study of the early phases of star formation and in cosmology, in the study
of the formation of large structures in the universe. At longer term, installation of such instrumentation at Dome-C in
Antarctica is also under investigation. The present status of the ArTeMiS project is detailed in this paper.
APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the world's outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 μm makes APEX suitable for observations up to 200 μm, through all atmospheric submm windows accessible from the ground.
The development program of the flight model imaging camera for the PACS instrument on-board the Herschel
spacecraft is nearing completion. This camera has two channels covering the 60 to 210 microns wavelength
range. The focal plane of the short wavelength channel is made of a mosaic of 2×4 3-sides buttable bolometer
arrays (16×16 pixels each) for a total of 2048 pixels, while the long wavelength channel has a mosaic of 2 of the
same bolometer arrays for a total of 512 pixels. The 10 arrays have been fabricated, individually tested and
integrated in the photometer. They represent the first filled arrays of fully collectively built bolometers with
a cold multiplexed readout, allowing for a properly sampled coverage of the full instrument field of view. The
camera has been fully characterized and the ground calibration campaign will take place after its delivery to
the PACS consortium in mid 2006. The bolometers, working at a temperature of 300 mK, have a NEP close
to the BLIP limit and an optical bandwidth of 4 to 5 Hz that will permit the mapping of large sky areas.
This paper briefly presents the concept and technology of the detectors as well as the cryocooler and the warm
electronics. Then we focus on the performances of the integrated focal planes (responsivity, NEP, low frequency
Since 1997, CEA/SAP and CEA/LETI/SLIR have been developing monolithic Si bolometer arrays sensitive in the far infrared and submillimiter range for space observations. Two focal planes, 32x64 and 16x32 pixel arrays, are designed and manufactured for the PACS (Photodetector Array Camera and Spectrometer) instrument of the Herschel observatory, to be launched in 2007. The two arrays cover respectively the 60-130 μm and 130-210 μm ranges. The goal of these large bolometer arrays is to achieve observations in a Background limited NEP around 10<sup>-16 </sup>W.Hz<sup>-1/2</sup>. The detector physics and manufacture techniques of the different stages of these arrays are first presented. Then we describe the read-out and multiplexing cold electronics (300mK) that make possible several functional modes (temporal and fixed pattern noise reduction,...). The latest experimental measurements carried out with the complete detector system at the nominal temperature are presented and performances are discussed.
Since 1997, CEA/DSM/DAPNIA/ Service d?Astrophysique in Saclay and CEA/DTA/LETI in Grenoble are developing filled Bolometer arrays sensitive in far infrared and submillimeter. These arrays are based on an all Silicon technology development, and are optimized for imaging in high photon background conditions. A 32 × 64 and a 16 × 32 pixels arrays are under development for the far infrared photometer in the PACS instrument, which is part of the Herschel payload. We present details of the design of these arrays. We describe the performance measurements obtained so far, and give some prospects for future application