A new microcalorimeter concept for photon counting x-ray spectroscopy
01 May 1989-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment (North-Holland)-Vol. 277, pp 657-663
TL;DR: In this article, an innovative approach for performing photon counting X-ray spectroscopy with cryogenic microcalorimeters is presented, which takes advantage of the temperature dependence of the dielectric constant in ferroelectric materials.
Abstract: We present an innovative approach for performing photon counting X-ray spectroscopy with cryogenic microcalorimeters. The detector concept takes advantage of the temperature dependence of the dielectric constant in ferroelectric materials. A dielectric calorimeter has many potential advantages over traditional resistive devices, particularly in the reduction of Johnson noise. This makes the energy resolution for photon counting spectroscopy limited only to the noise produced by the intrinsic temperature fluctuations of the device. The detector concept is presented and its predicted performance is compared with resistive calorimeters. Calculations have shown that practical instruments operating with an energy resolution less than 20 eV may be possible at 300 mK.
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01 Mar 1993-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the authors used semiconductor thermistors as the thermometer to achieve an energy resolution of 0.1% or better for 6 keV X-ray photons.
Abstract: Thermal detection of individual X-ray photons by small (0.5×0.5 mm) calorimeters has been used to achieve an energy resolution as good as 7.5 eV FWHM for 6 keV X-rays. Such detectors should have interesting applications in X-ray astronomy as well as laboratory spectroscopy, and they promise a high tolerance for embedded sources. Ideally, it should be possible to improve the resolution greatly by making smaller detectors or operating them at lower temperatures than the 50–100 mK currently used. However, there appear to be fairly fundamental limitations when semiconductor thermistors are used as the thermometer. When trying to achieve energy resolution of 0.1% or better, fluctuations in the thermalization efficiency of the detector must also be considered, and this places additional restrictions on suitable detector materials.
56 citations
11 Jan 1996-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the authors developed voltage and charge sensitive FET preamplifiers which feature ultra low noise, convenience and flexibility for phonon and ionization detectors operated at 20 mK.
Abstract: We have developed voltage and charge sensitive FET preamplifiers which feature ultra low noise, convenience and flexibility for phonon and ionization detectors operated at 20 mK. With an NJ132L J-FET, the white noise of the voltage amplifier is 1.1 nV/√Hz at room temperature and 0.9 nV/√Hz when the FET is cooled to ≈120 K; the 1 f knee is below 100 Hz. The power dissipation of the FET, about 7 mW in our application, allows it to be used in a 4 K environment. With the same cooled FET, the charge amplifier has shown a noise of 120 e− rms with a total input capacitance of 45 pF.
21 citations
TL;DR: In this paper, the authors present numerical methods for the optimization of bolometric infrared detectors which use current-biased semiconducting thermistors, and they extend the analysis of Griffin and Holland to explicitly include both the electric field dependence of the thermistor resistance and amplifier noise.
Abstract: We present numerical methods for the optimization of bolometric infrared detectors which use current-biased semiconducting thermistors. We extend the analysis of Griffin and Holland to explicitly include both the electric field dependence of the thermistor resistance and amplifier noise. These methods allow the user to design and evaluate an optimized bolometer once such parameters as the optical loading, the heat sink temperature, and the materials for the thermal link and the thermistor have been chosen. Measured parameters which describe the electrical nonlinearities in neutron transmutation doped germanium are presented. The consequences for bolometer optimization of including these effects are illustrated. This program will be made available at the web site http://physics7.berkeley.edu/bolometer.html.
10 citations
27 Nov 1989
TL;DR: In this paper, the use of kinetic inductance thermometers for X-ray micro-calorimeters is investigated, which exploits the strong temperature dependence of magnetic penetration depth of thin superconducting films.
Abstract: Conventional X-ray microcalorimeters have so far used ionimplanted resistors for thermometers. Recently, however, several new methods for sensing small temperature changes have been suggested that are nondissipative. Such devices may have intrinsically better energy resolution by eliminating the Johnson noise present in resistive devices. The use of kinetic inductance thermometers for X-ray microcalorimeters is being investigated. This technique exploits the strong temperature dependence of magnetic penetration depth of thin superconducting films. The prototype system, designed for operation at 1.5 K, uses films of aluminum and tin. Once the expected temperature sensitivity and alpha particle detection have been demonstrated, aluminum will be replaced with titanium or another material with a suitable critical temperature and the device will be operated at 0.3 K. At this temperature, the energy resolution from thermal noise should be sufficiently good to allow X-ray detection.
4 citations
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08 Oct 1992
TL;DR: In this article, a thermal X-ray detector with a measured resolution of 7 eV (FWHM) for 6 keV X-rays was presented, and the detailed behavior of the detector thermistor and thermal links imposed limits on performance.
Abstract: We have been developing thermal detectors for X-ray astronomy. These detectors have the advantages of both high energy resolution and high quantum efficiency. A practical detector operating at a temperature of 0.1 K could ideally have a resolution as good as 1 eV (FWHM). We have produced a detector with a measured resolution of 7 eV (FWHM) for 6 keV X-rays. The detailed behavior of the detector thermistor and thermal links impose limits on performance. Techniques for improving detector behavior will be discussed. We are currently constructing an instrument for launch on a sounding rocket to observe the soft X-ray emission from the interstellar medium.
4 citations
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TL;DR: Analysis of the relative noise performance of many types of pulse-shaping systems is discussed in terms of recent work on noise analysis, and applications of the technique to time-variant as well as time-invariant systems are illustrated.
160 citations
TL;DR: The state-of-the-art in photoconductors and bolometers is reviewed in this paper, centering on the materials development and concepts of extrinsic Si and Ge devices, and it is suggested that in the field of 2D detector arrays the hybrid circuits containing a photoconductor or a photodiode array, bonded with In solder to a switched MOS readout device with up to 60 x 60 elements, will produce superior performance.
106 citations
TL;DR: In this paper, a microcalorimeter was proposed to measure the energy released in the absorption of a single photon by sensing the rise in temperature of a small absorbing structure, which can in principle be made as low as 1 eV.
Abstract: Thermal detectors for X-ray spectroscopy combining high spectral resolution and quantum efficiency have been developed. These microcalorimeters measure the energy released in the absorption of a single photon by sensing the rise in temperature of a small absorbing structure. The ultimate energy resolution of such a device is limited by the thermodynamic power fluctuations in the thermal link between the calorimeter and isothermal bath and can in principle be made as low as 1 eV. The performance of a real device is degraded due to noise contributions such as excess 1/f noise in the thermistor and incomplete conversion of energy into phonons. The authors report some recent advances in thermometry, X-ray absorption and thermalization, fabrication techniques, and detector optimization in the presence of noise. These improvements have resulted in a device with a spectral resolution of 17 eV FWHM, measured at 6 keV. >
59 citations
TL;DR: In this paper, a dielectric bolometer is proposed for the infrared, which can achieve noise figures below 3 decibels even at chopper frequencies well above the 1/tau value of the detector.
Abstract: Thermal detectors for the infrared, such as thermocouples and bolometers, are limited in their ultimate sensitivity predominantly by Johnson noise rather than temperature noise. Low noise figures are hard to achieve since Johnson noise preponderates temperature noise, which is the only essential noise for thermal detectors. The dielectric constants of some materials are sufficiently temperature dependent to make a new type of bolometer feasible. The basic theory of a dielectric bolometer, as shown here, promises noise figures below 3 decibels even at chopper frequencies well above the 1/tau value of the detector. Ferroelectrics such as barium-strontium titanate and others seem to be well suited for radiation-cooled dielectric bolometers.
56 citations
TL;DR: In this article, the authors evaluate the properties of thermal detectors and find that their measurements agree well with the general theory of thermodynamics, and that the magnitude of the equilibrium temperature fluctuations agrees well with that predicted by thermodynamics for the detectors tested.
Abstract: Thermal detectors operating at cryogenic temperatures can be used as sensitive microcalorimeters for measuring small pulses of energy such as produced by the absorption of individual X-ray photons. This scheme has two major advantages for photon detection. First, in principle, all the X-ray energy can be degraded into phonons to which we are sensitive, thus avoiding the statistical noise associated with the partition of the energy into several channels. Second, the limiting noise of the energy measurement is set by thermodynamic fluctuations. At low temperatures, these fluctuations in practical devices will allow energy resolution on the order of a few electron volts (eV) FWHM. We present results of experiments performed to evaluate the characteristics of thermal detectors. We find that our measurements agree well with the the general theory of thermal detectors. Specifically, the magnitude of the equilibrium temperature fluctuations agrees well with that predicted by thermodynamics for the detectors tested. The completeness of energy thermalization, however, varies among the devices tested. We will discuss this as it affects detector energy resolution.
20 citations