Herschel flight models sorption coolers

The Herschel and Planck satellites will be jointly launched on an ARIANE 5 in 2008. The Herschel payload consists of three instruments built by international scientific consortia, heterodyne instrument for first (HIFI), photo-conductor array camera and spectrometer (PACS) and spectral and photometric imaging receiver (SPIRE). The spacecraft provides the environment for astronomical observations in the infrared and sub-millimeter wavelength range requiring cryogenic temperatures for the cold focal plane units. The spectral and photometric imaging receiver (SPIRE) will cover the 200–670 μm spectral range using bolometric detectors, as the photo-conductor array camera and spectrometer (PACS) will cover the 60–210 μm spectral range. Both instruments SPIRE and PACS feature detectors operating at 300 mK. This cooling will be effected by two helium sorption coolers developed at the Service des Basses Températures of the Commissariat à l’Energie Atomique (CEA-SBT). These coolers based on an evaporative cooling cycle features no moving parts and can be recycled indefinitely pending the availability of a cold heat sink at temperature below 3 K. Several models were developed in the course of the Herschel program and this paper deals with the design, manufacturing and qualification of the flight model coolers.     

Measurement of Low Temperature Specific Heat of Crystalline TeO2 for the Optimization of Bolometric Detectors

The optimization of bolometric detectors, like those that will be developed for the rare event experiment CUORE, requires a complete knowledge of the detector's thermal parameters. Since the CUORE detecting elements will consist of TeO₂ crystals, we have measured the specific heat of this material down to 60 mK with the thermal relaxation method. Previous available data were taken at temperatures higher than 0.6 K. Our results are clearly consistent with a lattice dominated specific heat. The Debye temperature, evaluated to be (232±7) K, is in excellent agreement with the elastic constant values measured by other authors. The knowledge of the Debye temperature allows a simple prediction of the pulse amplitude of presently working bolometers.     

Multi-chroic Feed-Horn Coupled TES Polarimeters

Multi-chroic polarization sensitive detectors offer an avenue to increase both the spectral coverage and sensitivity of instruments optimized for observations of the cosmic-microwave background (CMB) or sub-mm sky. We report on an effort to adapt the Truce Collaboration horn coupled bolometric polarimeters for operation over octave bandwidth. Development is focused on detectors operating in both the 90 and 150?GHz bands which offer the highest CMB polarization to foreground ratio. We plan to deploy an array of 256 multi-chroic 90/150 GHz polarimeters with 1024 TES detectors on ACTPol in 2013, and there are proposals to use this technology for balloon-borne instruments. The combination of excellent control of beam systematics and sensitivity make this technology ideal for future ground, ballon, and space missions.     

Characterization and Physical Explanation of Energetic Particles on Planck HFI Instrument

The Planck High Frequency Instrument (HFI) has been surveying the sky continuously from the second Lagrangian point (L2) between August 2009 and January 2012. It operates with 52 high impedance bolometers cooled at 100 mK in a range of frequency between 100 GHz and 1 THz with unprecedented sensitivity, but strong coupling with cosmic radiation. At L2, the particle flux is about 5 \(\hbox {cm}^{-2}\,\hbox {s}^{-1}\) and is dominated by protons incident on the spacecraft. Protons with an energy above 40 MeV can penetrate the focal plane unit box causing two different effects: glitches in the raw data from direct interaction of cosmic rays with detectors (producing a data loss of about 15 % at the end of the mission) and thermal drifts in the bolometer plate at 100 mK adding non-Gaussian noise at frequencies below 0.1 Hz. The HFI consortium has made strong efforts in order to correct for this effect on the time ordered data and final Planck maps. This work intends to give a view of the physical explanation of the glitches observed in the HFI instrument in-flight. To reach this goal, we performed several ground-based experiments using protons and \(\alpha \) particles to test the impact of particles on the HFI spare bolometers with a better control of the environmental conditions with respect to the in-flight data. We have shown that the dominant part of glitches observed in the data comes from the impact of cosmic rays in the silicon die frame supporting the micro-machined bolometric detectors propagating energy mainly by ballistic phonons and by thermal diffusion. The implications of these results for future satellite missions will be discussed.     

FPN Sources in Bolometric Infrared Detectors

Low manufacturing cost and ease of use favor spreading of 2-D bolometric infrared detector arrays over various application domains such as predictive maintenance, medical imaging, automotive industry, and security. The infrared detector's main figure of merit has long been the noise equivalent temperature difference (NETD), which sets the minimum temperature difference distinguishable from background noise at sensor output. However, while nowadays uncooled detectors have achieved sufficient NETD, fixed pattern noise (FPN) is indeed becoming a crucial figure of merit especially when the focal plane array (FPA) is not regulated by a thermoelectric cooler (TEC). In this paper, we study the various sources of dispersion of infrared bolometric detectors and their respective impact on FPN in the resulting image. We propose an analytical model to identify main sources of nonuniformity, and the confrontation of results with actual measurements leads to the ability of a highly accurate on-chip thermal drift compensation.      

Spin-Orbital Dynamics in the B-Phase of Superfluid Helium-3

We report numerical calculations on the spin–orbital dynamics of ³He-B within the formalism of Poisson brackets with the two-fluid model by Leggett and Takagi. We incorporate an additional orbital term in the equations for the spin–orbit dynamics which plays an important role at very low temperatures, when the damping of orbit dynamics is small. We also find that, under the relevant experimental conditions, the Brinkman–Smith mode is strongly modified by the orbital dynamics. The orbital momentum does not relax completely to the direction of magnetic field, but remains significantly deflected, particularly at very low temperatures, and precesses at the dipole–dipole frequency and nutate at the NMR frequency. We report numerical calculations of the spin–orbit dynamics in the spatially inhomogeneous case. We solved for the mode of precession near the walls of the experimental cell, which significantly deviates from that, obtained in theoretical calculations in previous publications. We also identified the mechanism of instability of homogeneous precession at very low temperatures, the exponential growth of textural-spin waves of the longitudinal mode of NMR.     

Structural analysis of a cryogen-free refrigerator for space

Future X-ray observatories in space, such as European Space Agency's (ESA) X-ray evolving universe spectroscopy (XEUS) mission, will require cooling to the region 10–100 mK to enable the utilisation of advanced cryogenic photon detectors in cryogenic spectrometer instruments. Such missions are envisaged to be completely cryogen-free, replacing the traditional superfluid liquid helium cryostat with a space worthy mechanically cooled system. As part of the Mullard Space Science Laboratory's (MSSL) adiabatic demagnetisation refrigerator (ADR) development programme, we have investigated the construction of a flight cryostat containing a 10 mK ADR (the MSSL double ADR (dADR)) that can be cooled by a single Astrium (formally Matra Marconi Space (MMS)) 4 K mechanical cooler. A proto-type dADR has been constructed and will be flight proven as part of a sounding rocket payload, where the dADR system will be used to cool an array of superconducting tunnel junction (STJ) detectors at the focus of an X-ray telescope.     

ULTIMA: Magnetic Field Dependence of the Calibration Factor

ULTIMA is a project which proposes to use superfluid ³He as a sensitive medium for direct dark matter search. In this paper we report on new, detailed calibrations of our bolometric cells as a function of the magnetic field. An influence on the order of 20% on the peak height after an energy deposition is observed for magnetic fields up to 330 mT. Simultaneous measurements of neutron capture and heater events, releasing both a well defined energy, show that the effect is similar for both, and that it is possible to maintain a good calibration by an appropriate correction.      

Thermodynamics of hydrogen-bonding mixtures 2.G E,H E,andS E of 1-propanol +n-heptane

A metal ebulliometcr was used to measure total vapor-pressure (PTx) data on 18 mixtures of 1-propanol +n-heptane (and the pure components) between 380 and 445 K. Bubble-point data were measured at seven pressures between 200 kPa and I MPa. These data cover an intermediate region between previous data reported near atmospheric pressure and below and high-temperature data extending to the critical region. A Redlich--Kister G' model fit isotherms between 373.15 and 463.15 K via Barker's method with an average standard error of 0.2 to 0.5% in pressure. The system exhibits large positive deviations from ideality (derived =2.7–10.5) which decrease with temperature. EquimolarG ^E/T values thus derived also decrease with increasing temperature, which predicts a positiveH ^E An azeotrope exists under all conditions studied: the azeotropic composition increases in alcohol content with increasing temperature. These mixture thermodynamic data show that, above 345 K, the system 1-propanol +n-heptane belongs to the class of mixtures whereG ^E > 0,H ^E >0. andTS ^E > 0. This probably occurs because the 1-I orientational effect (in this case, hydrogen-bonding of the alcohol molecules) is more readily disrupted in the inert solvent than it would be a( lower temperatures, where the effect of hydrogen-bonding is stronger.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Multi-layer boron thin-film detectors for neutrons

Intrinsic efficiencies of multi-layer boron-10 thin-film detectors were studied theoretically and experimentally. For multi-layer schemes based on an optimized single-layer film thickness, the practical efficiency is limited to about 42% for thermal neutrons. This is about half the efficiency of a moderated ³He detectors in commercial use for portal monitoring. The efficiency limitation is due to charged particle loss in the boron layers and substrates. The same loss mechanism will prevent all substrate-based boron detectors from ever reaching the intrinsic efficiencies of high-pressure ³He tubes, independent of substrate geometry and material composition. Experimental data also indicate that the multi-layer detector configuration can have an efficiency approaching the theoretical limit. Excellent n/γ discrimination has also been achieved using an ionization chamber.     

He and BF3 neutron detector pressure effect and model comparison

Radiation detection systems for homeland security applications must possess the capability of detecting both gamma rays and neutrons. The radiation portal monitor systems that are currently deployed use a plastic scintillator for detecting gamma rays and ³He gas-filled proportional counters for detecting neutrons. Proportional counters filled with ³He are the preferred neutron detectors for use in radiation portal monitor systems because ³He has a large neutron cross-section, is relatively insensitive to gamma-rays, is neither toxic nor corrosive, can withstand extreme environments, and can be operated at a lower voltage than some of the alternative proportional counters. The amount of ³He required for homeland security and science applications has depleted the world supply and there is no longer enough available to fill the demand. Thus, alternative neutron detectors are being explored.Two possible temporary solutions that could be utilized while a more permanent solution is being identified are reducing the ³He pressure in the proportional counters and using boron trifluoride gas-filled proportional counters. Reducing the amount of ³He required in each of the proportional counters would decrease the rate at which ³He is being used; not enough to solve the shortage, but perhaps enough to increase the amount of time available to find a working replacement. Boron trifluoride is not appropriate for all situations as these detectors are less sensitive than ³He, boron trifluoride gas is corrosive, and a much higher voltage is required than what is used with ³He detectors. Measurements of the neutron detection efficiency of ³He and boron trifluoride as a function of tube pressure were made. The experimental results were also used to validate models of the radiation portal monitor systems.     

Pulse-Tube Dilution Refrigeration below 10 mK for Astrophysics

Astroparticle bolometric detectors often rely on the use of dilution refrigerators providing a large cooling power at millikelvin temperatures. Conventional machines, however, need a systematic supply of cryogenic fluids, complicating and making more expensive their operation, particularly in underground laboratories. We describe here novel cryogen-free dilution units, able to cool down large detectors to millikelvin temperatures, and where cooling and warming times have been optimised.      

Planck cryogenic testing in CSL premises, helium partial pressure management

Both satellite Planck and Herschel are cryogenic ones [1] and [2], the first one having a cold point around 0.1 K, the second one around 0.3 K. Not only are the detectors cooled, but also major subsystems and systems of the spacecrafts.The Centre Spatial de Liège (CSL) is involved in testing several parts of these spacecrafts [3], starting form optical tests on the mirrors or on the telescope, via cryogenic vibration testing of scientific focal plane instruments, ending with the full Planck spacecraft testing. Each test requires temperature lower than 20 K, in volumes ranging from 1 m³ to 60 m³, cooling several kilograms to more than one ton, and withstanding heat load up to 150 W in stabilisation.The overall Planck spacecraft test challenge is very high, as it is the only way to measure the end-to-end cooling chain of the spacecraft. The space conditions reproduction must be as perfect as possible to avoid the test set-up influence on the spacecraft performances, especially linked to radiative cooling, mechanical perturbations and Helium residual pressure.Different challenges are presented, and the related CSL solutions are described, highlighting the Helium partial pressure problem, the related computations and trapping system by large sorption panel.     

The MARE Project

The international project “Microcalorimeter Arrays for a Rhenium Experiment” (MARE) aims at a direct and calorimetric measurement of the electron antineutrino mass with sub-electronvolt sensitivity. MARE is divided in two phases. The first phase consists of two independent experiments using the presently available detector technology to reach a sensitivity of the order of 1 eV and to improve the understanding of the systematic uncertainties peculiar of this technique. In parallel to these experiments, a wide R&D program will single out the appropriate detector configuration, the read-out scheme and the large array technology for the second phase of MARE. In the second phase, the selected techniques will be applied to the realization of large arrays with as many as 10000 detectors each. At least five arrays will be then deployed to collect the statistics required to probe the antineutrino mass with a sensitivity of at least 0.2 eV, comparable to the one expected for the Katrin experiment (KATRIN Design Report, [2004]). On behalf of the MARE collaboration.     

Parametric oscillation with squeezed vacuum reservoirs

Employing the quantum Hamiltonian describing the interaction of a two-mode light (signal–idler modes) generated by a non-degenerate parametric oscillator (NDPO) with two uncorrelated squeezed vacuum reservoirs (USVR), we derive the master and the Fokker–Planck equations. The corresponding Fokker–Planck equation for the Q-function is then solved employing a propagator method developed by K. Fesseha [J. Math. Phys. 33 2179 (1992)]. Making use of this Q-function, we calculate the quadrature fluctuations of the optical system. From these results we infer that the signal–idler modes are in squeezed states. When the NDPO operates below threshold we show that, for a large squeezing parameter, a squeezing amounting to a noise suppression approaching 100% below the vacuum level in one of the quadratures can be achieved.     

High Pressure Phase Equilibria in the Systems Ammonia+Potassium Iodide, +Sodium Iodide, +Sodium Bromide, and +Sodium Thiocyanate: Solid–Liquid–Vapor and Liquid–Liquid–Vapor Equilibria

Solid salt–liquid–vapor equilibria and liquid–liquid–vapor equilibria were determined experimentally for the binary system NH₃+KI in the temperature range 333 to 673 K and at pressures up to 80 MPa. It is found that the system NH₃+KI belongs to Type V of fluid phase behavior according to the classification of van Konynenburg and Scott. The pressure of the three-phase curve solid salt–liquid–vapor is monotonically increasing in the temperature range investigated and reaches a value of 76 MPa at 670 K. The three-phase liquid–liquid–vapor curve starts in a lower critical end point at 407.3 K and 11.59 MPa and ends in an upper critical end point at 408.8 K and 11.92 MPa. For the systems NH₃+NaI, NH₃+NaBr, and NH₃+NaSCN, Type V fluid phase behavior is also found. In the system NH₃+NaI, the lower critical end point is found at 406.8 K and 11.52 MPa and the upper critical end point at 408.5 K and 11.86 MPa. For the system NH₃+NaBr, these coordinates are 404.6 K, 11.03 MPa and 408.8 K, 11.90 MPa, respectively, and, for the system NH₃+NaSCN, 409.2 K, 11.99 MPa and 409.6 K, 12.06 MPa.     

Thermal model for the bolometric response of high Tc superconducting films to optical pulses

The voltage response of thin-film high T_c superconductors to electromagnetic radiation is the basis for highly promising optical detectors. Experiments with laser pulses have created a controversy over whether the observed responses are due to a thermal mechanism or caused by a non-equilibrium process. In part, this controversy was caused by inadequate thermal modelling of the bolometric response. The present study applies a rigorous thermal radiation and heat conduction analysis to a high T_c film irradiated by an optical pulse and compares the predicted bolometric voltage response to experimental data. Based on the assumption of thermal boundary resistance between film and substrate as predicted by acoustic mismatch theory, the calculated temperature increase for 200 ns pulses is not sufficient to account for the observed voltage response when the initial film temperature is well below the transition temperature.