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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Silicon Hot-Electron Bolometers

We discuss a new type of direct detector, a silicon hot-electron bolometer, for measurements in the far-infrared and submillimeter spectral ranges. High performance bolometers can be made using the electron-phonon conductance in heavily doped silicon to provide thermal isolation from the cryogenic bath. Noise performance is expected to be near thermodynamic limits, allowing background limited performance for many far infrared and submillimeter photometric and spectroscopic applications.

Stevenson, Thomas R.↗
NASA NTRS1989

An ac bridge readout for bolometric detectors

The authors have developed a bolometer readout circuit which greatly improves the low-frequency stability of bolometric detectors. The circuit uses an ac bias voltage and two matched bolometers and allows stable dc bolometer operation for integration times greater than 10 s. In astronomical applications the readout allows for qualitatively different observation modes (e.g. staring or slow-drift scanning) which are particularly well suited for space observations and for the use of arrays. In many applications the readout can increase sensitivity. The authors present noise spectra for 4He temperature bolometers with no excess noise at frequencies greater than 0.1 Hz. The measured optical responsivity of a bolometer operated with the present readout is the same as that of a bolometer operated with a conventional readout.

Rieke, F. M.↗
NASA NTRS2005

Integrated Electron-tunneling Refrigerator and TES Bolometer for Millimeter Wave Astronomy

We describe progress in the development of a close-packed array of bolometers intended for use in photometric applications at millimeter wavelengths from ground- based telescopes. Each bolometer in the may uses a proximity-effect Transition Edge Sensor (TES) sensing element and each will have integrated Normal-Insulator-Superconductor (NIS) refrigerators to cool the bolometer below the ambient bath temperature. The NIS refrigerators and acoustic-phonon-mode-isolated bolometers are fabricated on silicon. The radiation-absorbing element is mechanically suspended by four legs, whose dimensions are used to control and optimize the thermal conductance of the bolometer. Using the technology developed at NIST, we fabricate NIS refrigerators at the base of each of the suspension legs. The NIS refrigerators remove hot electrons by quantum-mechanical tunneling and are expected to cool the biased (approx.10 pW) bolometers to <170 mK while the bolometers are inside a pumped 3He-cooled cryostat operating at approx.280 mK. This significantly lower temperature at the bolometer allows the detectors to approach background-limited performance despite the simple cryogenic system.

Silverberg, R. F.↗
NASA NTRS2003

The Design and Performance of the 384: Element Submillimeter Detector Array for SHARC II

We report on the performance of the SHARC II detector, a 12 x 32 array of ion implanted Si pop-up bolometers. This 384 element detector array was built as a prototype for the High Angular Resolution Widefield Camera (HAWC) for the Stratospheric Observatory for Infrared Astronomy (SOFIA). We will discuss the design process, the characterization of the detectors, and the performance of the array in the SHARC II instrument. SHARC II is now a facility instrument on the Caltech Submillimeter Observatory, providing background-limited imaging at 350 and 450 microns.

Moseley, Samuel H.↗
DOE OSTI2023

The background model of the CUPID-Mo $0\nu\beta\beta$ experiment

CUPID-Mo, located in the Laboratoire Souterrain de Modane (France), was a demonstrator for the next generation 0vββ decay experiment, CUPID. It consisted of an array of 20 enriched Li 2 100 MoO 4 bolometers and 20 Ge light detectors and has demonstrated that the technology of scintillating bolometers with particle identification capabilities is mature. Furthermore, CUPID-Mo can inform and validate the background prediction for CUPID. In this paper, we present a detailed model of the CUPID-Mo backgrounds. This model is able to describe well the features of the experimental data and enables studies of the 2vββ decay and other processes with high precision. We also measure the radio-purity of the Li 2 100 MoO 4 crystals which are found to be sufficient for the CUPID goals. Finally, we also obtain a background index in the region of interest of 3.7 $^{+0.9}_{-0.8}$ (stat) $^{+1.5}_{-0.7}$ (syst) x 10 -3 counts/ ΔE FWHM / mol iso / year the lowest in a bolometric Ovββ decay experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS2001

Focal Plane Arrays of Voltage-Biased Superconducting Bolometers

The 200-micrometer to 3-mm wavelength range has great astronomical and cosmological significance. Science goals include characterization of the cosmic microwave background, measurement of the Sunyaev-Zel'dovich effect in galaxy clusters, and observations of forming galaxies. Cryogenic bolometers are the most sensitive broadband detectors in this frequency range. Because single bolometer pixels are reaching the photon noise limit for many observations, the development of large arrays will be critical for future science progress. Voltage-biased superconducting bolometers (VSBs) have several advantages compared to other cryogenic bolometers. Their strong negative electrothermal feedback enhances their linearity, speed, and stability. The large noise margin of the SQUID readout enables multiplexed readout schemes, which are necessary for developing large arrays. In this paper, we discuss the development of a large absorber-coupled array, a frequency-domain SQUID readout multiplexer, and an antenna-coupled VSB design.

Myers, Michael J.↗
NASA NTRS2009

Superconducting Hot-Electron Submillimeter-Wave Detector

A superconducting hot-electron bolometer has been built and tested as a prototype of high-sensitivity, rapid-response detectors of submillimeter-wavelength radiation. There are diverse potential applications for such detectors, a few examples being submillimeter spectroscopy for scientific research; detection of leaking gases; detection of explosive, chemical, and biological weapons; and medical imaging. This detector is a superconducting-transition- edge device. Like other such devices, it includes a superconducting bridge that has a low heat capacity and is maintained at a critical temperature (T(sub c)) at the lower end of its superconducting-transition temperature range. Incident photons cause transient increases in electron temperature through the superconducting-transition range, thereby yielding measurable increases in electrical resistance. In this case, T(sub c) = 6 K, which is approximately the upper limit of the operating-temperature range of silicon-based bolometers heretofore used routinely in many laboratories. However, whereas the response speed of a typical silicon- based laboratory bolometer is characterized by a frequency of the order of a kilohertz, the response speed of the present device is much higher characterized by a frequency of the order of 100 MHz. For this or any bolometer, a useful figure of merit that one seeks to minimize is (NEP)(tau exp 1/2), where NEP denotes the noise-equivalent power (NEP) and the response time. This figure of merit depends primarily on the heat capacity and, for a given heat capacity, is approximately invariant. As a consequence of this approximate invariance, in designing a device having a given heat capacity to be more sensitive (to have lower NEP), one must accept longer response time (slower response) or, conversely, in designing it to respond faster, one must accept lower sensitivity. Hence, further, in order to increase both the speed of response and the sensitivity, one must make the device very small in order to make its heat capacity very small; this is the approach followed in developing the present device.

Karasik, Boris↗
NASA NTRS1986

A progress report on bolometers operating at 0.1 K using adiabatic demagnetization refrigeration

Bolometers are still the detectors of choice for low background infrared observations at wavelengths longer than 200 microns. In the low background limit, bolometers become more sensitive as their operating temperature decreases, due to fundamental thermodynamic laws. The adiabatic demagnetization technique was evaluated by building a bolometer detection system operating at a wavelength of 1 millimeter for use at a ground based telescope. The system was fit checked at the telescope and is expected to take its first data in November, 1985.

Roellig, T.↗
NASA NTRS1989

A progress report on using bolometers cooled by adiabatic demagnetization refrigeration

For sensitive detection of astronomical continuum radiation in the 200 micron to 3 mm wavelength range, bolometers are presently the detectors of choice. In order to approach the limits imposed by photon noise in a cryogenically cooled telescope in space, bolometers must be operated at temperatures near 0.1 K. Researchers report progress in building and using bolometers that operate at these temperatures. The most sensitive bolometer had an estimated noise equivalent power (NEP) of 7 x 10(exp 017) W Hz(exp -1/2). Researchers also briefly discuss the durability of paramagnetic salts used to cool the bolometers.

Lesyna, L.↗
NASA NTRS1999

Fabrication of Pop-up Detector Arrays on Si Wafers

High sensitivity is a basic requirement for a new generation of thermal detectors. To meet the requirement, close-packed, two-dimensional silicon detector arrays have been developed in NASA Goddard Space Flight Center. The goal of the task is to fabricate detector arrays configured with thermal detectors such as infrared bolometers and x-ray calorimeters to use in space fliGht missions. This paper focuses on the fabrication and the mechanical testing of detector arrays in a 0.2 mm pixel size, the smallest pop-up detectors being developed so far. These array structures, nicknamed "PUDS" for "Pop-Up Detectors", are fabricated on I pm thick, single-crystal, silicon membranes. Their designs have been refined so we can utilize the flexibility of thin silicon films by actually folding the silicon membranes to 90 degrees in order to obtain close-packed two-dimensional arrays. The PUD elements consist of a detector platform and two legs for mechanical support while also serving as electrical and thermal paths. Torsion bars and cantilevers connecting the detector platform to the legs provide additional flexures for strain relief. Using micro-electromechanical structure (MEMS) fabrication techniques, including photolithography, anisotropic chemical etching, reactive-ion etching, and laser dicing, we have fabricated PLTD detector arrays of fourteen designs with a variation of four parameters including cantilever length, torsion bar length and width, and leg length. Folding tests were conducted to test mechanical stress distribution for the array structures. We obtained folding yields and selected optimum design parameters to reach minimal stress levels. Computer simulation was also employed to verify mechanical behaviors of PUDs in the folding process. In addition, scanning electron microscopy was utilized to examine the flatness of detectors and the alignment of detector pixels in arrays. The fabrication of thermistors and heaters on the pop-up detectors is under way, preparing us for the next step of the experiment, the thermal test.

Li, Mary J.↗
NASA NTRS2001

Development of Low-Noise High Value Chromium Silicide Resistors for Cryogenic Detector Applications

Extremely high sensitivity detectors, such as silicon bolometers are required in many NASA missions for detection of photons from the x-ray to the far infrared regions. Typically, these detectors are cooled to well below the liquid helium (LHe) temperature (4.2 K) to achieve the maximum detection performance. As photoconductors, they are generally operated with a load resistor and a pre-set bias voltage, which is then coupled to the input gate of a source-follower Field Effect Transistor (FET) circuit. It is imperative that the detector system signal to noise performance be limited by the noise of the detector and not by the noise of the external components. The load resistor value is selected to optimize the detector performance. These two criteria tend to be contradictory in that these detectors require load resistors in the hundreds of megaohms, which leads to a higher Johnson noise. Additionally, the physical size of the resistor must be small for device integration as required by such missions as the NASA High Resolution Airborne Wide-Band Camera (HAWC) instrument and the Submillimeter High Angular Resolution Camera (SHARC) for the Caltech Submillimeter Observatory (CSO). We have designed, fabricated and characterized thin film resistors using a CrSi/TiW/Al metal system on optical quality quartz substrates. The resistor values range from 100 megaohms to over 650 megaohms and are Johnson noise limited at LHe temperatures. The resistor film is sputtered with a sheet resistance ranging from 300 ohms to 1600 ohms and the processing sequence developed for these devices allows for chemically fine tuning the sheet resistance in-situ. The wafer fabrication process was of sufficiently high yield (>80%) providing clusters of good resistors for integrated multiple detector channels, a very important feature in the assembly of these two instruments.

Jhabvala, Murzy↗
NASA NTRS2002

Submillimeter Laboratory Investigations: Spectroscopy and Collisions

Currently, millimeter-wave and submillimeter-wave spectroscopy is conducted in our laboratory on several different types of spectrometers. Our standard spectrometer utilizes the output of a phase-locked klystron operating in the 40-60 GHz region, which is sent into a crossed-waveguide harmonic generator, or "multiplier". The high frequency millimeter-and submillimeter-wave radiation is transmitted via quasi-optical techniques through an absorption cell and then onto a detector, which is either an InSb hot electron bolometer cooled to 1.4 K or a Si bolometer cooled to 0.3 K. The detector response is sent to a computer for measurement and analysis. The frequency range produced and detected in this manner goes from 80 GHz to upwards of 1 THz. Spectra are normally taken with source modulation, with line frequencies typically measured to an accuracy of 50-100 kHz. Higher accuracy is available when needed. Recently, we developed a new, broad-band spectrometer in our laboratory based on a free-running backward wave oscillator (BWO) of Russian manufacture as the primary source of radiation. The so-called FASSST (fast-scan submillimeter spectroscopic technique) system uses fast-scan and optical calibration methods rather than the traditional locking techniques. The output power from the BWO is split such that 90% goes into the absorption cell while 10% is coupled to a 40-meter Fabry-Perot cavity, which yields fringe? for frequency measurement. Results from this spectrometer on the spectrum of nitric acid (HNO3) show that 100 GHz of spectral data can be obtained in 5 seconds with a measurement accuracy of 50 kHz. Currently, the frequency range of the FASSST system in our laboratory is roughly 100-700 GHz.

Herbst, Eric↗
NASA NTRS1998

Spectral Characterizations of the Clouds and the Earth's Radiant Energy System (CERES) Thermistor Bolometers using Fourier Transform Spectrometer (FTS) Techniques

Fourier Transform Spectrometer (FTS) techniques are being used to characterize the relative spectral response, or sensitivity, of scanning thermistor bolometers in the infrared (IR) region (2 - >= 100-micrometers). The bolometers are being used in the Clouds and the Earth's Radiant Energy System (CERES) program. The CERES measurements are designed to provide precise, long term monitoring of the Earth's atmospheric radiation energy budget. The CERES instrument houses three bolometric radiometers, a total wavelength (0.3- >= 150-micrometers) sensor, a shortwave (0.3-5-micrometers) sensor, and an atmospheric window (8-12-micrometers) sensor. Accurate spectral characterization is necessary for determining filtered radiances for longwave radiometric calibrations. The CERES bolometers spectral response's are measured in the TRW FTS Vacuum Chamber Facility (FTS - VCF), which uses a FTS as the source and a cavity pyroelectric trap detector as the reference. The CERES bolometers and the cavity detector are contained in a vacuum chamber, while the FTS source is housed in a GN2 purged chamber. Due to the thermal time constant of the CERES bolometers, the FTS must be operated in a step mode. Data are acquired in 6 IR spectral bands covering the entire longwave IR region. In this paper, the TRW spectral calibration facility design and data measurement techniques are described. Two approaches are presented which convert the total channel FTS data into the final CERES spectral characterizations, producing the same calibration coefficients (within 0.1 percent). The resulting spectral response curves are shown, along with error sources in the two procedures. Finally, the impact of each spectral response curve on CERES data validation will be examined through analysis of filtered radiance values from various typical scene types.

Thornhill, K. Lee↗
NASA NTRS1996

Bolometric detector systems for IR and mm-wave space astronomy

Recent developments in bolometric detector systems for millimeter and submillimeter wave space astronomy are described. Current technologies meet all the requirements for the high frequency instrument onboard the cosmic background radiation anisotropy satellite/satellite for the measurement of background anisotropies (COBRAS/SAMBA) platform. It is considered that the technologies that are currently being developed will significantly reduce the effective time constant and/or the cooling requirements of bolometric detectors. These technologies lend themselves to the fabrication of the large format arrays required for the Far Infrared and Submillimeter Space Telescope (FIRST). The scientific goals and detector requirements of the COBRAS/SAMBA platform that will use infrared bolometers are reviewed and the baseline detector system is described, including the feed optics, the infrared filters, the cold amplifiers and the warm readout electronics.

Church, S. E.↗
NASA NTRS2006

Semiconductor Bolometers Give Background-Limited Performance

Semiconductor bolometers that are capable of detecting electromagnetic radiation over most or all of the infrared spectrum and that give background-limited performance at operating temperatures from 20 to 300 K have been invented. The term background-limited performance as applied to a bolometer, thermopile, or other infrared detector signifies that the ability to detect infrared signals that originate outside the detector is limited primarily by thermal noise attributable to the background radiation generated external to the bolometer. The signal-to-noise ratios and detectivities of the bolometers and thermopiles available prior to this invention have been lower than those needed for background-limited performance by factors of about 100 and 10, respectively. Like other electrically resistive bolometers, a device according to the invention exhibits an increase in electrical resistance when heated by infrared radiation. Depending on whether the device is operated under the customary constant- current or constant-voltage bias, the increase in electrical resistance can be measured in terms of an increase in voltage across the device or a decrease in current through the device, respectively. In the case of a semiconductor bolometer, it is necessary to filter out visible and shorter-wavelength light that could induce photoconductivity and thereby counteract all or part of the desired infrared- induced increase in resistance. The basic semiconductor material of a bolometer according to the invention is preferably silicon doped with one or more of a number of elements, each of which confers a different variable temperature coefficient of resistance. Suitable dopants include In, Ga, S, Se, Te, B, Al, As, P, and Sb. The concentration of dopant preferably lies in the range between 0.1 and 1,000 parts per billion.

Goebel, John↗