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NASA NTRS1995

A quality monitor and monitoring technique employing optically stimulated electron emission

A light source directs ultraviolet light onto a test surface and a detector detects a current of photoelectrons generated by the light. The detector includes a collector which is positively biased with respect to the test surface. Quality is indicated based on the photoelectron current. The collector is then negatively biased to replace charges removed by the measurement of a nonconducting substrate to permit subsequent measurements. Also, the intensity of the ultraviolet light at a particular wavelength is monitored and the voltage of the light source varied to maintain the light a constant desired intensity. The light source is also cooled via a gas circulation system. If the test surface is an insulator, the surface is bombarded with ultraviolet light in the presence of an electron field to remove the majority of negative charges from the surface. The test surface is then exposed to an ion field until it possesses no net charge. The technique described above is then performed to assess quality.

Yost, William T.↗

NASA NTRS1990

A novel electron tunneling infrared detector

The pneumatic infrared detector, originally developed by Golay in the late 1940s, uses the thermal expansion of one cm(exp 3) of xenon at room temperature to detect the heat deposited by infrared radiation. This detector was limited by thermal fluctuations within a 10 Hz bandwidth, but suffered from long thermal time constants and a fragile structure. Nevertheless, it represents the most sensitive room temperature detector currently available in the long wavelength infrared (LWIR). Fabrication of this type of detector on smaller scales has been limited by the lack of a suitably sensitive transducer. Researchers designed a detector based on this principle, but which is constructed entirely from micromachined silicon, and uses a vacuum tunneling transducer to detect the expansion of the trapped gas. Because this detector is fabricated using micromachining techniques, miniaturization and integration into one and two-dimensional arrays is feasible. The extreme sensitivity of vacuum tunneling to changes in electrode separation will allow a prototype of this detector to operate in the limit of thermal fluctuations over a 10 kHz bandwidth. A calculation of the predicted response and noise of the prototype is presented with the general formalism of thermal detectors. At present, most of the components of the prototype have been fabricated and tested independently. In particular, a characterization of the micromachined electron tunneling transducer has been carried out. The measured noise in the tunnel current is within a decade of the limit imposed by shot noise, and well below the requirements for the operation of an infrared detector with the predicted sensitivity. Assembly and characterization of the prototype infrared detector will be carried out promptly.

Kenny, T. W.↗

NASA NTRS1987

Ionization Chamber Measures Extreme Ultraviolet

Ionization chamber operates in nearly total photon absorption as stable, self-calibrating detector of ionizing extreme ultraviolet radiation. Working gas of instrument is neon; photoionization properties well known and readily applicable to absolute measurements. Designed for measurements of solar ultraviolet flux aboard sounding rocket, instrument used on Earth to measure ultraviolet radiation in vacuum systems. Ionization chamber collects positive neon ions and electrons produced by irradiation of neon gas by ultraviolet photons. Approximately one ion produced by each photon; consequently, photoionization current nearly proportional to photon flux.

Carlson, Robert W.↗

NASA NTRS1993

Evolution of miniature detectors and focal plane arrays for infrared sensors

Sensors that are sensitive in the infrared spectral region have been under continuous development since the WW2 era. A quest for the military advantage of 'seeing in the dark' has pushed thermal imaging technology toward high spatial and temporal resolution for night vision equipment, fire control, search track, and seeker 'homing' guidance sensing devices. Similarly, scientific applications have pushed spectral resolution for chemical analysis, remote sensing of earth resources, and astronomical exploration applications. As a result of these developments, focal plane arrays (FPA) are now available with sufficient sensitivity for both high spatial and narrow bandwidth spectral resolution imaging over large fields of view. Such devices combined with emerging opto-electronic developments in integrated FPA data processing techniques can yield miniature sensors capable of imaging reflected sunlight in the near IR and emitted thermal energy in the Mid-wave (MWIR) and longwave (LWIR) IR spectral regions. Robotic space sensors equipped with advanced versions of these FPA's will provide high resolution 'pictures' of their surroundings, perform remote analysis of solid, liquid, and gas matter, or selectively look for 'signatures' of specific objects. Evolutionary trends and projections of future low power micro detector FPA developments for day/night operation or use in adverse viewing conditions are presented in the following test.

Watts, Louis A.↗

NASA NTRS1974

Television observations of artificial aurora and analyses of flight data from NASA payload 12.18 NE

An accelerator nominally capable of ejecting pulses of electrons up to 6 sec in length, current to 500 ma and energy to 20 keV was flown on a rocket at 1500 October 15, 1972. The Strypi rocket was launched from the Pacific Missile Range Facility at Kauai, Hawaii. The intent was to eject electron pulses of various characteristics upwards along the magnetic field so as to produce artificial auroras in the conjugate (Southern Hemisphere) atmosphere and possibly to produce weaker auroras in the nearby atmosphere as a consequence of backscattered electrons. The accelerator package included a gas jet actuated attitude control system controlled by gyros. Attitude sensing also was accomplished by a two-axis fluxgate magnetometer, and a large foil was deployed to collect ambient electrons to neutralize the accelerator when it ejected high-energy electrons. Scientific instrumentation contained on the flight package included retarding potential analyzers, energetic electron detectors, and detectors to sense very low frequency radio noise. Image orthicon television systems and other optical sensors were operated in the conjugate region aboard two NC-135 jet aircrafts based in Samoa. Similar devices were operated at Haleakala, Hawaii, to attempt detection of auroras caused by backscattered electrons.

Davis, T. N.↗

NASA NTRS1997

Space-Borne Infrared Astronomy

The objective of this grant is to develop the Far IR Photometer (FIRP), one of four focal plane instruments on the IR Telescope in Space (IRTS). The IRTS was successfully launched in March 18, 1995 aboard the Japanese SFU platform. It surveyed the IR sky for approximately 40 days, and was eventually retrieved by NASA's STS. The FIRP succeeded in surveying approximately 5% of the sky in four bands centered at 150, 250, 400 and 700 microns. Several new technologies were developed using the funds from this grant, including: (1) a high performance gas-gap heat-switch, (2) a He-3 sorption refrigerator that is, to date, the only refrigerator to achieve sub-Kelvin temperatures in orbit, (3) high-sensitivity bolometric detectors with NEP less than 10-16 W(Hz(exp l/2)exp 1/2) when operated from a 300 mK heat sink, (4) readout electronics capable of providing DC stability for the bolometric detectors. Excess noise of unknown origin significantly reduced the sensitivity of the FIRP on orbit. Nevertheless, scientifically significant observations of the spectrum and temperature of the interstellar dust were made, and have been reported.

Lange, Andrew E.↗

NASA NTRS2017

Investigation of Deuterium Loaded Materials Subject to X-Ray Exposure

Results are presented from an exploratory study involving x-ray irradiation of select deuterated materials. Titanium deuteride plus deuterated polyethylene, deuterated polyethylene alone, and for control, hydrogen-based polyethylene samples and nondeuterated titanium samples were exposed to x-ray irradiation. These samples were exposed to various energy levels from 65 to 280 kV with prescribed electron flux from 500 to 9000 μA impinging on a tungsten braking target, with total exposure times ranging from 55 to 280 min. Gamma activity was measured using a high-purity germanium (HPGe) detector, and for all samples no gamma activity above background was detected. Alpha and beta activities were measured using a gas proportional counter, and for select samples beta activity was measured with a liquid scintillator spectrometer. The majority of the deuterated materials subjected to the microfocus x-ray irradiation exhibited postexposure beta activity above background and several showed short-lived alpha activity. The HPE and nondeuterated titanium control samples exposed to the x-ray irradiation showed no postexposure alpha or beta activities above background. Several of the samples (SL10A, SL16, SL17A) showed beta activity above background with a greater than 4σ confidence level, months after exposure. Portions of SL10A, SL16, and SL17A samples were also scanned using a beta scintillator and found to have beta activity in the tritium energy band, continuing without noticeable decay for over 12 months. Beta scintillation investigation of as-received materials (before x-ray exposure) showed no beta activity in the tritium energy band, indicating the beta emitters were not in the starting materials.

x-ray irradiation↗

NASA NTRS2003

Review of the High Performance Antiproton Trap (HiPAT) Experiment at the Marshall Space Flight Center

The significant energy density of matter-antimatter annihilation is attractive to the designers of future space propulsion systems, with the potential to offer a highly compact source of power. Many propulsion concepts exist that could take advantage of matter-antimatter reactions, and current antiproton production rates are sufficient to support basic proof-of-principle evaluation of technology associated with antimatter- derived propulsion. One enabling technology for such experiments is portable storage of low energy antiprotons, allowing antiprotons to be trapped, stored, and transported for use at an experimental facility. To address this need, the Marshall Space Flight Center's Propulsion Research Center is developing a storage system referred to as the High Performance Antiproton Trap (HiPAT) with a design goal of containing 10(exp 12) particles for up to 18 days. The HiPAT makes use of an electromagnetic system (Penning- Malmberg design) consisting of a 4 Telsa superconductor, high voltage electrode structure, radio frequency (RF) network, and ultra high vacuum system. To evaluate the system normal matter sources (both electron guns and ion sources) are used to generate charged particles. The electron beams ionize gas within the trapping region producing ions in situ, whereas the ion sources produce the particles external to the trapping region and required dynamic capture. A wide range of experiments has been performed examining factors such as ion storage lifetimes, effect of RF energy on storage lifetime, and ability to routinely perform dynamic ion capture. Current efforts have been focused on improving the FW rotating wall system to permit longer storage times and non-destructive diagnostics of stored ions. Typical particle detection is performed by extracting trapped ions from HiPAT and destructively colliding them with a micro-channel plate detector (providing number and energy information). This improved RF system has been used to detect various plasma modes for both electron and ion plasmas in the two traps at MSFC, including axial, cyclotron, and diocotron modes. New diagnostics are also being added to HiPAT to measure the axial density distribution of the trapped cloud to match measured RF plasma modes to plasma conditions.

Pearson, J. B.↗

NASA NTRS1988

Laboratory studies of sticking coefficients and heterogeneous reactions important in the Antarctic stratosphere

Laboratory studies of sticking coefficients of H2O, HCl, Cl2, and HNO3 on ice and heterogeneous reactions of ClONO2 with ice or HCl/ice have been performed in a fast flow reactor. A quadrupole mass spectrometer with electron impact ionization was used as a detector. Measured sticking coefficients are: 0.3 (+0.7, -0.1) for H2O, 0.4 (+0.6, -0.2) for HCL, less than 0.0001 for Cl2, and 0.3 (+0.7, -0.1) for HNO3 at 200 K. The reaction probability of ClONO2 on ice was found to be 0.06 (+ or - 0.03) while HOCl was observed as a sole product in the gas phase. With HCl present in ice, the reaction probability of ClONO2 is greatly enhanced, approaching 0.27 (+0.73, -0.13) while molecular chlorine was found to be the major product in the gas phase. Another reaction product was nitric acid which remained in the solid phase. Since the polar stratospheric clouds contain ice particles or possibly HCl/ice particles on the surface, the present results should be a major factor in producing the observed springtime ozone depletion in the Antarctic stratosphere.

Leu, Ming-Taun↗

NASA NTRS2009

Zinc Alloys for the Fabrication of Semiconductor Devices

ZnBeO and ZnCdSeO alloys have been disclosed as materials for the improvement in performance, function, and capability of semiconductor devices. The alloys can be used alone or in combination to form active photonic layers that can emit over a range of wavelength values. Materials with both larger and smaller band gaps would allow for the fabrication of semiconductor heterostructures that have increased function in the ultraviolet (UV) region of the spectrum. ZnO is a wide band-gap material possessing good radiation-resistance properties. It is desirable to modify the energy band gap of ZnO to smaller values than that for ZnO and to larger values than that for ZnO for use in semiconductor devices. A material with band gap energy larger than that of ZnO would allow for the emission at shorter wavelengths for LED (light emitting diode) and LD (laser diode) devices, while a material with band gap energy smaller than that of ZnO would allow for emission at longer wavelengths for LED and LD devices. The amount of Be in the ZnBeO alloy system can be varied to increase the energy bandgap of ZnO to values larger than that of ZnO. The amount of Cd and Se in the ZnCdSeO alloy system can be varied to decrease the energy band gap of ZnO to values smaller than that of ZnO. Each alloy formed can be undoped or can be p-type doped using selected dopant elements, or can be n-type doped using selected dopant elements. The layers and structures formed with both the ZnBeO and ZnCdSeO semiconductor alloys - including undoped, p-type-doped, and n-type-doped types - can be used for fabricating photonic and electronic semiconductor devices for use in photonic and electronic applications. These devices can be used in LEDs, LDs, FETs (field effect transistors), PN junctions, PIN junctions, Schottky barrier diodes, UV detectors and transmitters, and transistors and transparent transistors. They also can be used in applications for lightemitting display, backlighting for displays, UV and visible transmitters and detectors, high-frequency radar, biomedical imaging, chemical compound identification, molecular identification and structure, gas sensors, imaging systems, and for the fundamental studies of atoms, molecules, gases, vapors, and solids.

Ryu, Yungryel↗

NASA NTRS2014

Design Improvements and X-Ray Performance of a Time Projection Chamber Polarimeter for Persistent Astronomical Sources

The design of the Time-Projection Chamber (TPC) Polarimeter for the Gravity and Extreme Magnetism Small Explorer (GEMS) was demonstrated to Technology Readiness Level 6 (TRL-6)3 and the flight detectors fabricated, assembled and performance tested. A single flight detector was characterized at the Brookhaven National Laboratory Synchrotron Light Source with polarized X-rays at 10 energies from 2.3-8.0 keV at five detector positions. The detector met all of the GEMS performance requirements. Lifetime measurements have shown that the existing flight design has 23 years of lifetime4, opening up the possibility of relaxing material requirements, in particular the consideration of the use of epoxy, to reduce risk elsewhere. We report on design improvements to the GEMS detector to enable a narrower transfer gap that, when operated with a lower transfer field, reduces asymmetries in the detector response. In addition, the new design reduces cost and risk by simplifying the assembly and reducing production time. Finally, we report on the performance of the narrow-gap detector in response to polarized and unpolarized X-rays.

GEMS↗

NASA NTRS2002

Ion Storage with the High Performance Antiproton Trap (HiPAT)

The matter antimatter reaction represents the densest form of energy storage/release known to modern physics: as such it offers one of the most compact sources of power for future deep space exploration. To take the first steps along this path, NASA-Marshall Space Flight Center is developing a storage system referred to as the High Performance Antiproton Trap (HiPAT) with a goal of maintaining 10(exp 12) particles for up to 18 days. Experiments have been performed with this hardware using normal matter (positive hydrogen ions) to assess the device's ability to hold charged particles. These ions are currently created using an electron gun method to ionize background gas; however, this technique is limited by the quantity that can be captured. To circumvent this issue, an ion source is currently being commissioned which will greatly increase the number of ions captured and more closely simulate actual operations expected at an antiproton production facility. Ions have been produced, stored for various time intervals, and then extracted against detectors to measure species, quantity and energy. Radio frequency stabilization has been tested as a method to prolong ion lifetime: results show an increase in the baseline 1/e lifetime of trapped particles from hours to days. Impurities in the residual background gas (typically carbon-containing species CH4, CO, CO2, etc.) present a continuing problem by reducing the trapped hydrogen population through the mechanism of ion charge exchange.

Martin, James↗

NASA NTRS1999

Detector Assembly and the Ultralow-Temperature Refrigerator for XRS

The X-ray spectrometer (XRS) on the Japanese Astro-E Spacecraft is the first ultra low temperature space borne instrument. The system utilizes a 900g Ferric Ammonium Alum (FAA) Adiabatic Demagnetization Refrigerator (ADR) with a helium-3 gas gap heat switch to cool the detector assembly to 0.060K. The system operates in a "single shot" configuration allowing the system to remain at its operating temperature for about 40 hours in the lab. The on-orbit performance is expected to be about 35 hours with a 97% duty cycle. The detector assembly for XRS consists of a 32 channel microcalorimeter array bias electronics, thermometry, and an anti-coincidence detector that are attached to the cold stage of the ADR. To thermally Isolate the detector system from the superfluid helium reservoir, the detector system is suspended by Kevlar cords and electrical connection in made by L30, 17-micron diameter, tensioned NbTi leads. The detectors are read out in a source-follower arrangement using FET amplifiers operating at 130K mounted in multiply-thermally-isolated assemblies that also use Kevlar and stainless steel wiring. The design and thermal performance of this system will be discussed and compared to the theoretical limits.

Porter, F. S.↗

NASA NTRS1994

A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

Judge, Darrell L.↗

NASA NTRS1994

A rare gas optics-free absolute photon flux and energy analyzer for solar and planetary observations

We have developed a prototype spectrometer for space applications requiring long term absolute EUV photon flux measurements. In this recently developed spectrometer, the energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

Judge, Darrell L.↗

NASA NTRS1992

A rare gas optics-free absolute EUV photon spectrometer for solar system studies

We have developed a prototype spectrometer for space applications which require long term absolute EUV photon flux measurements. In this recently developed spectrometer, the energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer operating at a few eV, and followed by an electron multiplying detector, pulses due to individual electrons are counted. The overall efficiency of this process is essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided.

Daybell, M. D.↗

NASA NTRS1985

Moisture content and gas sampling device

An apparatus is described for measuring minute quantities of moisture and other contaminants within sealed enclosures such as electronic assemblies which may be subject to large external atmospheric pressure variations. An array of vacuum quality valves is arranged to permit cleansing of the test apparatus of residual atmospheric components from a vacuum source. This purging operation evacuates a gas sample bottle, which is then connected by valve settings to provide the drive for withdrawing a gas sample from the sealed enclosure under test into the sample bottle through a colometric detector tube (Drager tube) which indicates moisture content. The sample bottle may be disconnected and its contents (drawn from the test enclosure) separately subjected to mass spectrograph analysis.

Krieg, H. C., Jr.↗

NASA NTRS2014

Performance Verification of the Gravity and Extreme Magnetism Small Explorer GEMS X-Ray Polarimeter

olarimetry is a powerful tool for astrophysical observations that has yet to be exploited in the X-ray band. For satellite-borne and sounding rocket experiments, we have developed a photoelectric gas polarimeter to measure X-ray polarization in the 2-10 keV range utilizing a time projection chamber (TPC) and advanced micro-pattern gas electron multiplier (GEM) techniques. We carried out performance verification of a flight equivalent unit (1/4 model) which was planned to be launched on the NASA Gravity and Extreme Magnetism Small Explorer (GEMS) satellite. The test was performed at Brookhaven National Laboratory, National Synchrotron Light Source (NSLS) facility in April 2013. The polarimeter was irradiated with linearly-polarized monochromatic X-rays between 2.3 and 10.0 keV and scanned with a collimated beam at 5 different detector positions. After a systematic investigation of the detector response, a modulation factor greater than or equal to 35% above 4 keV was obtained with the expected polarization angle. At energies below 4 keV where the photoelectron track becomes short, diffusion in the region between the GEM and readout strips leaves an asymmetric photoelectron image. A correction method retrieves an expected modulation angle, and the expected modulation factor, approximately 20% at 2.7 keV. Folding the measured values of modulation through an instrument model gives sensitivity, parameterized by minimum detectable polarization (MDP), nearly identical to that assumed at the preliminary design review (PDR).

Time Projection↗