J.-P. Porst

NASA, Вашингтон, West Virginia, United States

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Publications (26)23.19 Total impact

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    ABSTRACT: We have developed prototype arrays of metallic magnetic calorimeters for applications in X-ray astronomy. Each pixel consists of an all-gold X-ray absorber in good thermal contact to a gold-erbium paramagnetic thin film thermometer that is operated in the temperature range of 30–100 mK. The para-magnetic response is coupled to a SQUID amplifier. We have characterized pixels in an array and observed the expected temperature dependence of the magnetization and heat capacity. We have demonstrated a full width at half maximum energy resolution of 1.7 \(\pm \) 0.1 eV at 6 keV and have also read out these devices using time-division multiplexing.
    Journal of Low Temperature Physics 09/2014; 176(5-6). DOI:10.1007/s10909-013-1019-y · 1.04 Impact Factor
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    ABSTRACT: Mo/Au transition-edge sensors exhibit weak-link behavior in the measured temperature, and field, dependence of the critical current . This is a consequence of the longitudinal proximitization between the Nb electrical bias contacts and the bilayer. Understanding how weak-link superconductivity impacts the resistive transition and the detector energy resolution is of great interest. In this contribution we present studies of for three devices that have different geometries of metallic depositions on top of the sensor used for noise mitigation and X-ray absorption. Results show that these features change the measured compared to the previously seen measurements on devices without additional deposition layers. Measurements of the small signal transition parameters and also reveal differences between designs that impact the measured response to X-rays and energy resolution.
    Journal of Low Temperature Physics 08/2014; 176(3-4). DOI:10.1007/s10909-013-1031-2 · 1.04 Impact Factor
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    ABSTRACT: We are developing kilo-pixel arrays of small-pitch transition-edge sensors for high spectral-resolving, high count-rate applications in astrophysics and solar physics measurements. We have fabricated and tested pixels that are 65 \upmu m in size on a silicon substrate with an X-ray flux of {̃ }100 counts per second (cps) per pixel. The X-ray pulses were recorded and analyzed in various ways to obtain high throughput with good energy resolution. We have demonstrated 2.3 eV FWHM resolution with 99.6 % throughput for a 6-keV X-ray flux of 100 cps.
    Journal of Low Temperature Physics 12/2013; 176(3-4). DOI:10.1007/s10909-013-1071-7 · 1.04 Impact Factor
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    ABSTRACT: Magnetically coupled calorimeters (MCC) have extremely high potential for X-ray applications. Although very high energy-resolution has been demonstrated, until now there has been no multiplexed read-out of MCCs. We report on the first realization of a time domain multiplexed read-out of MCCs. Although this has many similarities with time domain multiplexing of transition-edge sensors, for MCCs the energy resolution is limited by the SQUID read-out noise, and requires the well established scheme to be altered in order to minimize degradation due to noise aliasing effects. In our approach, each pixel is read out by a single first-stage SQUID that is operated in open loop. The outputs of the SQ1s are low-pass filtered with an array of low cross-talk inductors, then fed into a single-stage SQUID multiplexer. The multiplexer is addressed from room temperature and read out through a single amplifier channel. We present the noise performance and compare to expectations. We have demonstrated multiplexed X-ray spectroscopy at 5.9 keV and for improved readout noise achieved an energy resolution ΔEFWHM <; 6 eV for emulated multiplexing. We show that in an optimized setup, it is possible to multiplex 32 detectors without significantly degrading the intrinsic detector resolution.
    IEEE Transactions on Applied Superconductivity 06/2013; 23(3):2500905-2500905. DOI:10.1109/TASC.2013.2243792 · 1.32 Impact Factor
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    ABSTRACT: The Micro-X sounding rocket program will fly a 128-pixel array of transition-edge-sensor microcalorimeters to enable high-resolution X-ray imaging spectroscopy of supernova remnants. To match the angular resolution of the optics while maximizing the field-of-view and retaining a high energy resolution (2-4 eV at 1 keV), we have designed the pixels using 590 × 590 μm2 Au/Bi absorbers, which overhang 140 × 140 μm2 Mo/Au sensors. Here we report experimental results from flight-candidate arrays, including measurements of energy resolution, uniformity, and absorber thermalization. We describe the reduction in pixel-to-pixel crosstalk afforded by an angle-evaporated Cu backside heatsinking layer, which provides Cu coverage on the four sidewalls of the silicon wells beneath each pixel. In addition, we present measurements of devices that have an identical pixel architecture but were fabricated with thin (sub-micron) all-Au absorbers.
    IEEE Transactions on Applied Superconductivity 06/2013; 23(3):2101705-2101705. DOI:10.1109/TASC.2013.2244631 · 1.32 Impact Factor
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    ABSTRACT: We have made high-resolution X-ray microcalorimeters using superconducting MoAu bilayers and Nb meander coils. The temperature sensor is a magnetic penetration thermometer. Operation is similar to metallic magnetic calorimeters, but instead of the magnetic susceptibility of a paramagnetic alloy, we use the diamagnetic response of the superconducting MoAu to sense temperature changes in an X-ray absorber. Flux-temperature responsivity can be large for small sensor heat capacity, with enough dynamic range for applications. We find that models of observed flux-temperature curves require several effects to explain flux penetration or expulsion in the microscopic devices. The superconductor is nonlocal, with large coherence length and weak pinning of flux. At the lowest temperatures, behavior is dominated by screening currents that vary as a result of the temperature dependence of the magnetic penetration depth, modified by the effect of the nonuniformity of the applied field occurring on a scale comparable to the coherence length. In the temperature regime where responsivity is greatest, spatial variations in the order parameter become important: both local variations as flux enters/leaves the film and an intermediate state is formed, and globally as changing stability of the electrical circuit creates a Meissner transition and flux is expelled/penetrates to minimize free energy.
    IEEE Transactions on Applied Superconductivity 06/2013; 23(3):2300605-2300605. DOI:10.1109/TASC.2013.2239695 · 1.32 Impact Factor
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    ABSTRACT: We are developing small-pixel transition-edge sensor microcalorimeters for solar physics and astrophysics applications. These large format close-packed arrays are fabricated on solid silicon substrates and are designed to have high energy resolution, and also accommodate count-rates of up to a few hundred counts per second per pixel for X-ray photon energies up to ~ 8 keV. We have fabricated kilo-pixel versions that utilize narrow-line planar and stripline wiring. These arrays have a low superconducting transition temperature, which results in a low heat capacity and low thermal conductance to the heat sink. We present measurements of the performance of pixels with single 65-μm absorbers on a 75-μm pitch. With individual single pixels of this type, we have achieved a full-width at half-maximum energy resolution of 0.9 eV with 1.5 keV Al K X-rays, to our knowledge the first X-ray microcalorimeter with sub-eV energy resolution. We will discuss the properties of these arrays and their application to new solar and astrophysics mission concepts.
    IEEE Transactions on Applied Superconductivity 06/2013; 23(3). DOI:10.1109/TASC.2013.2238752 · 1.32 Impact Factor
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    ABSTRACT: For the first time we have investigated the behavior of fully micro-fabricated low temperature metallic magnetic calorimeters (MMCs) after undergoing an ion-implantation process. This experiment had the aim to show the possibility to perform a high precision calorimetric measurement of the energy spectrum following the electron capture of $^{163}$Ho using MMCs having the radioactive $^{163}$Ho ions implanted in the absorber. The implantation of $^{163}$Ho ions was performed at ISOLDE-CERN. The performance of a detector that underwent an ion-implantation process is compared to the one of a detector without implanted ions. The results show that the implantation dose of ions used in this experiment does not compromise the properties of the detector. In addition an optimized detector design for future $^{163}$Ho experiments is presented.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2013; 711:150. DOI:10.1016/j.nima.2013.01.027 · 1.32 Impact Factor
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    ABSTRACT: When energy is deposited in a thin-film cryogenic detector, such as from the absorption of an x-ray, an important feature that determines the energy resolution is the amount of athermal energy that can be lost to the heat bath prior to the elementary excitation systems coming into thermal equilibrium. This form of energy loss will be position dependent and therefore can limit the detector energy resolution. An understanding of the physical processes that occur when elementary excitations are generated in metal films on dielectric substrates is important for the design and optimization of a number of different types of low-temperature detectors. We have measured the total energy loss in one relatively simple geometry that allows us to study these processes and compare measurements with calculation based upon a model for the various different processes. We have modeled the athermal phonon energy loss in this device by finding an evolving phonon distribution function that solves the system of kinetic equations for the interacting system of electrons and phonons. Using measurements of device parameters such as the Debye energy and the thermal diffusivity we have calculated the expected energy loss from this detector geometry, and also the position-dependent variation of this loss. We have also calculated the predicted impact on measured spectral lineshapes and have shown that they agree well with measurements. In addition, we have tested this model by using it to predict the performance of a number of other types of detector with different geometries, where good agreement is also found.
    Physical Review B 03/2013; 87(10). DOI:10.1103/PhysRevB.87.104504 · 3.74 Impact Factor
  • Nuclear Physics B - Proceedings Supplements 08/2012; s 229–232:446. DOI:10.1016/j.nuclphysbps.2012.09.083 · 0.88 Impact Factor
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    ABSTRACT: We are developing kilopixel arrays of TES microcalorimeters to enable high-resolution x-ray imaging spectrometers for future x-ray observatories and laboratory astrophysics experiments. Our current array design was targeted as a prototype for the X-ray Microcalorimeter Spectrometer proposed for the International X-ray Observatory, which calls for a 40x40-pixel core array of 300 mu m devices with 2.5 eV energy resolution (at 6 keV). Here we present device characterization of our 32x32 arrays, including x-ray spectral performance of individual pixels within the array. We present our results in light of the understanding that our Mo/Au TESs act as weak superconducting links, causing the TES critical current (I (c) ) and transition shape to oscillate with applied magnetic field (B). We show I (c) (B) measurements and discuss the uniformity of these measurements across the array, as well as implications regarding the uniformity of device noise and response. In addition, we are working to reduce pixel-to-pixel electrical and thermal crosstalk; we present recent test results from an array that has microstrip wiring and an angle-evaporated copper backside heatsinking layer, which provides copper coverage on the four sidewalls of the silicon wells beneath each pixel.
    Journal of Low Temperature Physics 06/2012; 167(5-6):732-740. DOI:10.1007/s10909-012-0514-x · 1.04 Impact Factor
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    ABSTRACT: The measurement of calorimetric spectra following atomic weak decays, beta (β) and electron capture (EC), of nuclides having a very low Q-value, can provide an impressively high sensitivity to a non-vanishing neutrino mass. The achievable sensitivity in this kind of experiments is directly connected to the performance of the used detectors. In particular an energy resolution of a few eV and a pulse formation time well below 1 μs are required. Low temperature Metallic Magnetic Calorimeters (MMCs) for soft X-rays have already shown an energy resolution of 2.0 eV FWHM and a pulse rise-time of about 90 ns for fully micro-fabricated detectors. We present the use of MMCs for high precision measurements of calorimetric spectra following the β-decay of 187Re and the EC of 163Ho. We show results obtained with detectors optimized for 187Re and for 163Ho experiments respectively. While the detectors equipped with superconducting Re absorbers have not yet reached the aimed performance, a first detector prototype with a Au absorber having implanted 163Ho ions already shows excellent results. An energy resolution of 12 eV FWHM and a rise time of 90 ns were measured.
    Journal of Low Temperature Physics 06/2012; 167(5-6). DOI:10.1007/s10909-012-0556-0 · 1.04 Impact Factor
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    ABSTRACT: Highly-charged heavy ions like U91+ provide unique conditions for the investigation of relativistic and quantum electrodynamical effects in strong electromagnetic fields. We present two X-ray detectors developed for high-resolution spectroscopy on highly-charged heavy ions. Both detectors consist of metallic magnetic calorimeters (MMCs) forming linear eight-pixel arrays. The first detector, maXs-20, is developed for the detection of X-rays up to 20 keV with an energy resolution below 3 eV. The second device, maXs-200, is designed for X-ray energies up to 200 keV with an energy resolution of 40 eV. The results of characterization measurements of single detectors of both arrays will be shown and discussed. In both cases, the performance of the detectors agrees well with their design values. Furthermore, we present a prototype MMC for soft X-rays with improved magnetic flux coupling. In first characterization measurements the energy resolution of this device was 2.0 eV (FWHM) for X-rays up to 6 keV.
    Journal of Low Temperature Physics 05/2012; 167(3-4). DOI:10.1007/s10909-012-0557-z · 1.04 Impact Factor
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    ABSTRACT: The ideal X-ray camera for astrophysics would have more than a million pixels and provide an energy resolution of better than 1 eV FWHM for energies up to 10 keV. We have microfabricated and characterized thin-film magnetic penetration thermometers (MPTs) that show great promise towards meeting these capabilities. MPTs operate in similar fashion to metallic magnetic calorimeters (MMCs), except that a superconducting sensor takes the place of a paramagnetic sensor and it is the temperature dependence of the superconductor's diamagnetic response that provides the temperature sensitivity. We present a description of the design and performance of our prototype thin-film MPTs with MoAu bilayer sensors, which have demonstrated an energy resolution of similar to 2 eV FWHM at 1.5 keV and 4.3 eV FWHM at 5.9 keV.
    Journal of Low Temperature Physics 05/2012; 167:455-460. DOI:10.1007/s10909-012-0516-8 · 1.04 Impact Factor
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    ABSTRACT: Magnetic calorimeters have been under development for over 20 years targeting a wide variety of different applications that require very high resolution spectroscopy. They have a number of properties that distinguish them from other low temperature detectors. In this paper we review these properties and emphasize the types of application to which they are most suited. We will describe what has been learned about the best materials, geometries, and read-out amplifiers and our understanding of the measured performance and theoretical limits. While most magnetic calorimeter research has concentrated on the use of paramagnets to provide the temperature sensitivity, recently magnetically coupled microcalorimeters have been in development that utilize the diamagnetic response of superconductors. We will contrast some of the properties of the two different magnetic sensor types.
    Journal of Low Temperature Physics 05/2012; 167(3-4):254-268. DOI:10.1007/s10909-012-0544-4 · 1.04 Impact Factor
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    ABSTRACT: Cryogenic particle detectors have recently been adopted in radiation detection and measurement because of their high energy resolution. Many of these detectors have demonstrated energy resolutions better than the theoretical limit of semiconductor detectors. We report the development of a micro-fabricated magnetic calorimeter coupled to a large-area particle absorber. It is based on a planar, 1mm2 large paramagnetic temperature sensor made of sputtered Au:Er, which covers a superconducting meander-shaped pickup coil coupled to a low-noise dc-SQUID to monitor the magnetization of the sensor. A piece of gold foil of 2.5×2.5×0.07mm3 was glued to the Au:Er film to serve as an absorber for incident alpha particles. The detector performance was investigated with an 241Am source. The signal size comparison for alpha and gamma peaks with a large difference in energy demonstrated that the detector had good linear behavior. An energy resolution of 2.83±0.05keV in FWHM was obtained for 5.5MeV alpha particles.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 10/2011; 652(1):299-301. DOI:10.1016/j.nima.2010.11.066 · 1.32 Impact Factor
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    ABSTRACT: In the last years the mixing of the three neutrino flavor eigenstates through a unitary matrix has been experimentally proved. Presently one of the greatest challenges in neutrino physics is to establish the absolute value of the masses of the three neutrino mass eigenstates. The kinematic determination of electron neutrino and antineutrino mass by means of the analysis of calorimetric spectra of isotopes which undergo a beta or electron‐capture decay, with especially low energy available for the decay itself, represents an interesting method. In fact this method is less affected by theoretical models defining branching ratio among different decay modes. For the beta decay the isotope with the lowest Q‐value present in nature is the 187Re (Q about 2.5 keV) while for the electron capture decay the best candidate known is the 163Ho (Q about 2.5 keV). Since those experiments need to be extremely precise, they might suffer from unexpected systematic errors. It is therefore important to investigate in detail the performance of the detectors and the calorimetric spectrum. We present our results obtained with low temperature magnetic calorimeters designed for measuring low energy beta and electron capture spectra. We also discuss problematic and the possibly present systematic uncertainties using this kind of detectors.
    12/2009; 1185(1):607-611. DOI:10.1063/1.3292415
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    ABSTRACT: Metallic magnetic calorimeter (MMC) is one of the most promising x-ray detector technologies for providing the very high energy resolution needed for future astronomical x-ray imaging spectroscopy. For this purpose, we have developed micro-fabricated 5x5 arrays of MMC of which each individual pixel has excellent energy resolution as good as 3.4 eV at 6 keV x-ray. Here we report on the fabrication techniques developed to achieve good resolution and high efficiency. These include: processing of a thin insulation layer for strong magnetic coupling between the AuEr sensor film and the niobium pick-up coil; production of overhanging absorbers for enhanced efficiency of x-ray absorption; fabrication on SiN membranes to minimize the effects on energy resolution from athermal phonon loss. We have also improved the deposition of the magnetic sensor film such that the film magnetization is nearly completely that is expected from the AuEr sputter target bulk material. In addition, we have included a study of a positional sensitive design, the Hydra design, which allows thermal coupling of four absorbers to a common MMC sensor and circuit.
    AIP Conference Proceedings 12/2009; 1185(1). DOI:10.1063/1.3292411
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    ABSTRACT: Metallic magnetic calorimeters (MMC) are calorimetric particle detectors, typically operated at temperatures below 100 mK, that make use of a paramagnetic temperature sensor to transform the temperature rise upon the absorption of a particle in the detector into a measurable magnetic flux change in a dc‐SQUID. During the last years a growing number of groups has started to develop MMC for a wide variety of applications, ranging from alpha‐, beta‐ and gamma‐spectrometry over the spatially resolved detection of accelerated molecule fragments to arrays of high resolution x‐ray detectors. For x‐rays with energies up to 6 keV an energy resolution of 2.7 eV (FWHM) has been demonstrated and we expect that this can be pushed below 1 eV with the next generation of devices. We give an introduction to the physics of MMCs and summarize the presently used readout schemes as well as the typically observed noise contributions and their impact on the energy resolution. We discuss general design considerations, the micro‐fabrication of MMCs and the performance of micro‐fabricated devices. In this field large progress has been achieved in the last years and the thermodynamic properties of most materials approach bulk values allowing for optimal and predictable performance.
    12/2009; 1185(1):571-578. DOI:10.1063/1.3292407
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    ABSTRACT: We are developing micro‐fabricated x‐ray microcalorimeter arrays that show great promise for use in future x‐ray spectroscopy missions. In each pixel we sense the magnetization change due to the heat input of an absorbed x‐ray using a meander‐shaped superconducting pickup trace that is on a substrate that is separate from the low noise 2‐stage SQUID read‐out. We report on the results from our prototype arrays that have achieved an energy resolution of 3.3 eV at 6 keV, and are progressing future arrays towards the goal of demonstrating sub‐eV energy resolution. The results from studies of the thermalization of gold and gold‐bismuth absorbers on sub‐microsecond timescales will be presented. We will also present the results of comparisons of the magnetization and heat capacity of micro‐fabricated devices to those of larger hand‐constructed devices.
    12/2009; 1185(1):579-582. DOI:10.1063/1.3292408