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Colloque R&D INSU – Grenoble (9-12 mai 2011) Colloque R&D INSU – Grenoble (9-12 mai 2011) CAGIRE : Development of an Infra-red camera CAGIRE : Development of an Infra-red camera CAGIRE SCOPE AND OBJECTIVES : The SVOM mission, with a synergy of space and ground instruments, will enable the detection and study of Gamma Ray Bursts (GRBs). The aim is to understand physical processes involved in the GRBs, and the use of these GRBs to study distant galaxies. As a ground section of the SVOM mission, a French telescope specialized in GRBs following will accurately localize and characterize the GRBs detected by the space instruments of the mission. It will be equipped with a near infrared cammera covering z, H and J bands. This poster is focused on the development of the near infrared camera CAGIRE (Catching the GRBs InfraRed Emission), a camera with original characteristics : compactness, long autonomy, no nitrogen cooling, detector control by ASIC). The current step is the design and realization of a test instrument for engineering. This test model will be validated during the second semester of 2011, allowing the characterization of engineering and scientific detector during 2012 & 2013 years. The science model based on the test model design and experience will integrate the constraints from operations (environment and telescope interface). The design will begin in 2012, the delivery of the science model is scheduled for mid 2014. ARCHITECTURE OF THE TEST CAMERA : The test camera will enable the use of different types of IR detectors (Teledyne H2RG and H1RG). The detector is directly linked by a flex circuit to a cryogenic card, both integrated to the test cryostat, this is the detection module The detection module is electrically linked by a flex circuit to an external card (JADE 2), USB2 interface. The detection module is thermally linked to a cold interface. The thermal load is compensated by a Stirling cryocooler with a cooling capacity of 15W @ 120K. To reduce the thermal load, the detection module is covered by a thermal shield To perform measures of dark current, a removable cold mask is installed in the cryostat DETECTION MODULE : The detector is integrated on a TZM (molybdenum) mount to match the CTE (Coefficient of Thermal Expansion) of the detector. Depending on the type of detector integrated, two types of mount can be used, either with 3 or 4 mounting pads (the four mounting pads version of the detector increases the thermal conduction between the mount and the detector, one of the pads is bolted on a flexible fixture). The detector mount is locally flat to a precision of ±5 microns to avoid overstress of the detector. The detector mount is located and held in position by three sleeved feet made of epoxy fiberglass (G11). The choice of the material optimizes both thermal insulation and mechanical resistance (the robotic telescope will generate high accelerations of the camera, typically 10g), with a low out gassing rate. This mounting ensures a constant shrinkage of the assembly, because of the thermal gradient. A cryogenic card is linked to the detector, and shielded. The cryogenic card mount is supported by two feet also made of epoxy fiberglass (G11) to optimize thermal and mechanical aspects. TEST CAMERA DEVELOPMENT TEST CAMERA DEVELOPMENT THERMAL ASPECTS : The cold source is a twin piston integral Stirling cryocooler. The cold finger of the machine will be regulated to a temperature of 120 K. The detector temperature will be regulated to a temperature of 140 K @ ±0.001K during the exposure time. The regulation is done with a separate thermal control loop (one sensor, one heater) for the cryogenic card and for the detector. The system is fitted of 6 temperature sensors (Lakeshore DT-670-CU). The regulations and temperature monitoring are carried out by a Lakeshore model 340 cryogenic temperature controller. In operation, and in case of failure of any components, the system ensures a maximum thermal gradient of 1K/min thanks to a massive copper cold interface (0.6 kg). Because of the high velocity of the robotic telescope and because of the need of autonomy of the cryostat, the cryocooler is mechanically linked to the cryostat. This implies to minimize the vibrations of the cryocooler to preserve the performances of the camera. The detector assembly and cryogenic card assembly are linked to the cold interface by flexible copper braids in order to isolate the detection module from cryocooler vibrations. The flexibility of the braids will also compensate the dilatations due to the thermal gradient. To reduce the thermal load, the detection module is covered by a thermal floating shield. Including the cold mask of the system, the thermal load is 4W (detector @140 K ,cryostat @293 K). It is expected that the margin between the consumed power and the capacity of the cryocooler (15W) will increase the life of the machine and decrease the level of the vibrations Collaborations : Phillippe Ambert3, Jean-Luc Atteia1, Francis Beigbeder1, Marc Bouyé2, Remi Cabanac1, Patrick Couderc1, Bruno Dubois2, Michel Dupieux1, Carole Gaiti1, Thierry Gharsa1, Alain Klotz1 , Driss Kouach2, Jean-François Leborgne1, Romain Mathon2, Xavier Régal 4 , Hervé Valentin1 1 : Institut de Recherche en Astrophysique et Planétologie (www.irap.omp.eu) 2 : Observatoire Midi-Pyrénées, Groupe d’Instrumentation Scientifique (www.obs-mip.fr) 3 : Télescope Bernard Lyot 4 : Observatoire de Haute-Provence VACUUM ASPECTS : The detection module is mounted inside of a vacuum vessel made of INOX 304. To ensure correct operation of the camera, the pressure in the vessel has to be lower than 10-3 mbar during 6 months (maintenance frequency). According to the number of flanges of the system, such a performance could not be reach, even with UHV technologies. Most of the leaks is created by an hermetical electrical feedthrough transmitting the signal from vacuum to atmosphere. The system leak (theoretically predicted to 2.4.10-8 mbar.L/s) will be compensated by a miniature ion pump mounted on the cryostat. Primary pumping is obtained by a dry scroll pump, secondary pumping by a turbo pump. This pumping group fitted with a full range pressure gauge is disconnected from the vessel after vacuum generation. During operations, the pressure is monitored by a Bayard-Alpert pressure gauge. THE INSTRUMENT THE INSTRUMENT Sleeve Sleeved epoxy fiberglass foot H2RG 2k x 2k Detector Epoxy fiberglass foot Cryogenic card Thermal shield Thermal and optical shield TZM detector mount JADE 2 Conversion board Conversion board Flex cryogenic board – JADE2 JADE 2 feedthrough Temperature sensors feedthrough Cryocooler Miniature ion pump (2L/s for N2) CHARACTERISTICS SUM-UP : Mass : ………………………………… 55 kg (cryocooler 10 kg) Volume of the vessel :……………….. 6L (vessel Ø 304, height 200 mm) Thermal load :………………………… 4W (detector @140 K, cold finger @ 120K) Leaks : ………………………………... 2.4.10-8 mbar.L/s (theoretical prediction) Viewport : …………………………….. Fused silica (thickness 10 mm, window aperture 80 mm) Detector : …………………………….. Teledyne H2RG 2K x 2K @ 18 µm/px Cryocooler : ………………………….. Ricor K535 (MTTF > 25000 hrs) Cryocooler Cold mask Viewport Thermal shield Electrical interface Cold interface DN 250 CF viewport mount Detection module Cold mask manual actuator Detector assembly Cryogenic card assembly CAGIRE frame for installation on the test bench DETECTOR CONTROL: The detector mounted in this camera will be a HAWAII2-RG one from Teledyne Imaging Sensor. It is a SWIR detector with a cutoff of 1.7 µm (z, J, H bands allowed). The controller is an ASIC named SIDECAR, also from TIS. It will be installed inside the dewar and mounted on a little cryogenic board near the detector. Then, we have outside the dewar a board linked by a large flex to the ASIC cryoboard. This named JADE2 board adapts LVDS parallel signals coming from the ASIC to an USB2 standard link to the host computer. We aim to read the detector by 32 outputs, 100 kHz readout rate by channels. The assembler code of the ASIC microcontroller enables reading in follower sampling mode or up-the-ramp group mode. The both mode are programmable with several parameters. In principle we will use the URG mode, this mode insures a continuing readout of the detector, better for thermal stability. We aim to date the formats at 1 ms to locate low altitude satellites as a secondary task of the F-GFT. ACQUISITION SYSTEM: In the host computer we aim to use the testing software provided by TIS. This software enables communicating across a socket server from our application. On the other hand we have chosen Linux as operating system to have a stable and familiar open source environment. To keep the possibilities of the TIS software, delivered only under Windows, we have virtualized this OS with the “VirtualBox” open source tool. This software has very good facilities for USB I/O and network also for shared files, all this functionalities are very useful for our development. So we can easily develop a data acquisition application with scripting language like Tcl, reusing “AudeLA” software libraries, a familiar astroimaging software, and TIS testing software functions. Furthermore a remote desktop toll, VNC, enables from now on remote operation. This possibility will be totally necessary for the final settlement of the camera on a remote robotic telescope at San Pedro Mártir Observatory in Baja California. PROJECT STATUS (may 2011) A test dewar was designed by the GIS of OMP, the integration is in progress. The validation of the detector thermal regulation and dewar autonomy will be the next step. Characterization measurements with adapted test bench to the near infrared band will be done in 2012 on the aim to validate tools and methods, a HAWAII-1RG engineering detector will be mounted in the dewar for that purpose. Next developments are suspended on the Chinese commitment on the SVOM project. Particularly The purchase of the robotic telescope and the purchase of the scientific detector depend on that. Then we will make the definitive dewar which will benefit on the return of test dewar experiment and will include the constraint brought by the telescope. LINUX PC Virtual Windows PC Acquisition Application TIS Testing Software USB 2.0 Interface FO Up The Ramp Group Mode References : GL scientific Technical Report GSAOI H2RG 4Kx4K Detector Mosaic Module Design Description (G. Luppino) Figure 1 : CAGIRE architecture Figure 2 : Exploded view of the detection module Figure 3 : Electrical interface of the camera Figure 4 : The test instrument on its frame Figure 5 : H2RG 2kx2k detector Figure 6 : CAGIRE detection chain Figure 8 : CAGIRE block diagram Figure 9 : Up The Ramp Group Mode Figure 7 : SIDECAR ASIC & FPA block diagram
