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All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Investigation of a Helicopter Individual Blade Control (IBC) System in Two Full-Scale Wind Tunnel Tests: Volume I

This report presents the data acquired during the testing of an individual blade control (IBC) system on a full-scale helicopter rotor in two test entries in the NASA Ames 40- by 80-Foot Wind Tunnel. The objective of these investigations was to evaluate the potential benefits of using IBC to improve rotor performance, reduce blade vortex interaction (BVI) noise, and alleviate helicopter vibrations. The wind tunnel tests were an international, collaborative effort between NASA, the U.S. Army Aeroflightdynamics Directorate, ZF Luftfahrttechnik GmbH, Eurocopter Deutschland GmbH, and the German Aerospace Laboratory (DLR). They were conducted as a task of the U.S./German Memorandum of Understanding (MOU) on Helicopter Aeromechanics. The IBC tests were performed using a full-scale BO-105 helicopter rotor mounted to the NASA/U.S. Army Rotor Test Apparatus (RTA). The first test, performed in 1993, was the first full-scale wind tunnel test to explore the effects of an IBC system on rotor vibration, noise, and performance. In this test, the pitch links of the rotor were replaced by servo-actuators. The servo-actuators and IBC control system were designed and manufactured by ZF Luftfahrttechnik GmbH. This control system allowed the pitch of each rotor blade to be changed independently of the other blades. The IBC inputs had large effects on the hub vibrations and BVI noise. However, the rotor hub moments were not retrimmed with each new IBC input. This resulted in an out-of-trim rotor configuration. The same IBC system was used in the second IBC test performed in 1994. This test more carefully investigated the potential of IBC to simultaneously reduce noise and vibration and also investigated the effect of IBC on rotor performance in high-speed-cruise flight. In the 1994 test, the hub moment and rotor thrust were readjusted to maintain rotor trim as the IBC inputs were applied. For this reason, the data taken from the second test are considered to be more accurate, except for some unique IBC input combinations not repeated in the second test. IBC controls that were evaluated were single-frequency inputs from 2/rev to 6/rev and multi-harmonic combinations of these frequencies to form pulses, wavelets, and doublets. Extensive data were acquired for each IBC data point. These data included rotor performance, average and time-varying hub loads, rotor blade bending loads, control system loads, inboard and outboard blade pitch motions, and BVI noise data. The rotor balance hub force and moment data included the mean values, half-peak-to-peak values, and sine/cosine harmonics up to the 20th rotor harmonic. The time history and averaged Fourier spectrum for each measurement are available electronically from NASA Ames Research Center. The data indicate that significant reduction in both BVI noise and hub vibration can be obtained using IBC. The 2/rev input produced the best single-frequency results. At a typical descent flight condition, 2/rev IBC combined with other IBC harmonics reduced the BVI noise up to 12 dB (85 percent) at some microphone locations. At the same time, this input could also reduce the dominant 4/rev vibratory hub loads by up to 75 percent. The data also show that performance improvements of up to 7 percent were obtained using 2/rev IBC at high-speed forward flight conditions. An analysis of the hydraulic power requirements for BVI noise suppression, vibration reduction, and rotor performance improvement is included in this report. This analysis shows that the power required by the IBC system is negligible at low-speed flight conditions, and that a net gain of 3 percent of rotor horsepower can be achieved at high-speed flight conditions.

Investigation↗
DOE OSTI2020

Rapid Patterning and Advanced Device Structures for Low Cost Manufacturable Crystalline Si IBC Cells

Recent record efficiency Si cells have had an interdigitated back contact (IBC) design where both positive and negative contacts are fabricated on the back side of the Si wafer. Many industry groups have investigated IBC cells but used photolithography to pattern the rear contacts although it is considered impractical for low cost, high volume manufacturing. Alternative patterning methods using lasers and mechanical masking have been utilized in fabrication of patterned regions in IBC Si solar cells to replace photolithography. Another exciting advance in Si solar cell technology has been replacing the high temperature diffusion of doped regions inside the crystalline Si wafer with low temperature deposition of very thin layers of doped amorphous hydrogenated Si (a-Si:H) on the Si wafer. This is called a Si heterojunction (HJ) device. The a-Si:H provides excellent passivation of surface defects and has produced the highest open circuit voltages (VOC) of any Si solar cell device structure. The Institute of Energy Conversion (IEC) demonstrated the first IBC-HJ solar cell combining these two strategies in 2007 and has fabricated IBC-HJ cells with 20% efficiency using three photolithography steps. Despite the demonstrated efficiency potential of this device by industry groups (>26%) there is no commercial production because of the challenges of patterning and processing the structure in an industrial environment. Our work sought to address that challenge. The objective of this 3 year project was to develop the processing for the IBC-HJ Si solar cell using lasers for patterning and contact formation instead of photolithography. Laser patterning enables rapid, contactless manufacturing of patterned regions. We intensively studied laser fired contacts, laser patterning of the a-Si multi-layer stacks and metal layers and the use of plasma shadow masks. After an exhaustive focus in the first year on the laser fired emitter (LFE) and contact (LFC), we were unable to achieve VOC greater than 660 mV, compared to the 720 mV required to meet our milestones. We discovered that an additional issue with our original IBC structure was the presence of an inversion layer at the back surface connecting the p and n regions which reduced the VOC and fill factor (FF). We developed innovative methods for characterizing the inversion layer. These two limitations in the original design lead to development of a new IBC-HJ process sequence and device structure which we called Plasma Masked Laser Processed (PMLP). It retained the original high efficiency features including manufacturability. The LFC was replaced with a standard n-type a-Si HJ contact. The inversion layer was eliminated by replacing the previous p-type stack in the gap with an n-type or SiN stack. The PMLP used laser ablation of a multi-layer a-Si stack followed by chemical etching to open the n-contact. It required deposition of a patterned stack through a mask in the plasma deposition chamber. This turned out to be a source of significant problems due to inevitable unwanted deposition ‘leakage’ under the mask. This formed a blocking contact on the emitter which significantly reduced Voc and FF. Several iterations in PMLP device structure and chemical etching steps resulted in a large improvements, e.g. the efficiency increasing from 3 to 15% and Voc from 450 to 660 mV but they were unable to completely eliminate it. The best IBC-HJ device we fabricated had only 15% efficiency. For perspective, our standard FHJ devices had 20% efficiency.

14 SOLAR ENERGY↗
NASA NTRS2020

Investigation of a Helicopter Individual Blade Control (IBC) System in Two Full-Scale Wind Tunnel Tests: Volume II—Tabulated Data

This volume presents the tabulated data acquired during the testing of an individual blade control (IBC) system for a full-scale BO-105 helicopter rotor in the NASA Ames 40- by 80-Foot Wind Tunnel. The data are divided into appendices according to the data type. Table 6 in Volume I presents a summary of the data acquired during the 1993 and 1994 IBC wind tunnel tests. The data have been tabulated according to test year, run number, and point number (e.g., 1993 IBC Test, Run 20, pt. 3). The 1993 and 1994 IBC tests were each started with a run number of 1. A new run number was assigned each time the wind tunnel and rotor were restarted, even if no data were acquired during the previous run. For this reason, some run numbers appear to be missing, yet all of the IBC data is included in the tabulated data, with one notable exception. The Fourier series data presented in Appendices H, L, and N are provided only for the data points identified with the ”•“ symbol in the last column of Table 6 in Volume I. This was done to keep the physical size of the data tables reasonable. The table below shows which data were included in these appendices; the data encompass the majority of the IBC inputs tested in the wind tunnel. Data for the points not included in Appendices H, L, and N have been retained in the BO-105 IBC database and are electronically available from NASA Ames Research Center.

Investigation↗
DOE OSTI2022

Results of the Extraction-Scrub-Strip (ESS) Tests With Solvent Using IBC BOBCalix

Two Extraction, Scrub, and Strip (ESS) tests were performed on two BOBCalix solvent samples prepared using BOBCalix from IBC Advanced Technologies (“IBC”). The purpose of testing this sample is to confirm if the newly sourced BOBCalix displays the correct extraction and stripping behavior with cesium. The first batch of BOBCalix solvent was prepared using IBC lot#220310KC-1. The second batch was prepared using IBC lot#220615KC-3A. The ESS tests showed acceptable performance of the solvent for extraction, scrub, and strip operations. The extraction D (Cs) values for the tests were 12.9 and 13.6. This value is consistent with results from previous ESS tests using similar solvent formulations. Similarly, the strip cesium distribution ratios (0.0588/0.0342/0.0258 and 0.0575/0.0335/0.0262) fell within acceptable ranges.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2024

Extraction, Scrub, and Strip Test Results for the IBC BOBCalix Solvent Samples

A second vendor for solvent extraction components has been chosen for use at the Salt Waste Processing Facility (SWPF). IBC Advanced Technologies (IBC) has provided samples of their BOBCalix, as well as complete solvent. These samples were tested for quality assurance purposes to ensure their use at SWPF is acceptable. Two Extraction, Scrub, and Strip (ESS) tests were performed on solvent samples from IBC. The purpose of testing these samples was to determine if the solvents are displaying the correct extraction and stripping behavior with cesium.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2002

Large Format Si:As IBC Array Performance for NGST and Future IR Space Telescope Applications

A mid-IR (5-30micrometer) instrument aboard a cryogenic space telescope can have an enormous impact in resolving key questions in astronomy and cosmology. A space platform's greatly reduced thermal backgrounds (compared to airborne or ground-based platforms), allow for more sensitive observations of dusty young galaxies at high redshifts, star formation of solar-type stars in the local universe, and formation and evolution of planetary disks and systems. The previous generation's largest, in sensitive IR detectors at these wavelengths are 256x256 pixel Si:As Impurity Band Conduction (IBC) devices built by Raytheon Infrared Operations (RIO) for the Space Infrared Telescope Facility/Infrared Array Camera (SIRTF)/(IRAC) instrument. RIO has successfully enhanced these devices, increasing the pixel count by a factor of 16 while matching or exceeding SIRTF/IRAC device performance. NASA-ARC in collaboration with RIO has tested the first high performance large format (1024x 1024) Si:As IBC arrays for low background applications, such as for the middle instrument on Next Generation Space Telescope (NGST) and future IR Explorer missions. These hybrid devices consist of radiation hard SIRTF/IRAC-type Si:As IBC material mated to a readout multiplexer that has been specially processed for operation at low cryogenic temperatures (below 10K), yielding high device sensitivity over a wavelength range of 5-28 micrometers. We present laboratory testing results from these benchmark, devices. Continued development in this technology is essential for conducting large-area surveys of the local and early universe through observation and for complementing future missions such as NGST, Terrestrial Planet Finder (TPF), and Focal Plane Instruments and Requirement Science Team (FIRST).

Ennico, Kimberly↗
DOE OSTI2023

The brighter-fatter effect in the JWST MIRI Si:As IBC detectors: I. Observations, impact on science, and modeling

Context.The Mid-Infrared Instrument (MIRI) on board theJames WebbSpace Telescope (JWST) uses three Si:As impurity band conduction (IBC) detector arrays. The output voltage level of each MIRI detector pixel is digitally recorded by sampling up the ramp. For uniform or low-contrast illumination, the pixel ramps become nonlinear in a predictable way, but in areas of high contrast, the nonlinearity curve becomes much more complex. The origin of the effect is poorly understood and currently not calibrated out of the data. Aims.We provide observational evidence of the brighter-fatter effect (BFE) in MIRI conventional and high-contrast coronagraphic imaging, low-resolution spectroscopy, and medium-resolution spectroscopy data, and we investigate the physical mechanism that gives rise to the effect on the MIRI detector pixel raw voltage integration ramps. Methods.We used public data from the JWST/MIRI commissioning and Cycle 1 phase. We also developed a numerical electrostatic model of the MIRI detectors using a modified version of the publicPoisson_CCDcode. Results.We find that the physical mechanism behind the BFE manifesting in MIRI data is fundamentally different to that of charge-coupled devices and photodiode arrays such as the Hawaii-XRG near-infrared detectors used by the NIRISS, NIRCam, and NIRSpec instruments on board JWST. Observationally, the BFE makes the JWST MIRI data yield 10–25% larger point sources and spectral line profiles as a function of the relative level of de-biasing of neighboring detector pixels. This broadening impacts the MIRI absolute flux calibration, time-series observations of faint companions, and point spread function modeling and subtraction. We also find that the intra-pixel 2D profile of the shrinking Si:As IBC detector depletion region directly impacts the accuracy of the pixel ramp nonlinearity calibration model.

Astronomy & Astrophysics↗
DOE OSTI2020

Understanding and Mitigating the Contamination of Intrinsic poly-Si Gaps in Passivated IBC Solar Cells

We investigate factors that are critical for the performance of interdigitated back contact (IBC) solar cells based on polycrystalline silicon (poly-Si) passivated contacts. During patterning of doped lines using direct plasma deposition through a shadow mask, we show that the intrinsic poly-Si gap becomes contaminated with dopants, leading to shunting. Possible contamination mechanisms during masked deposition and high- temperature annealing are tested. Strategies developed to mitigate the contamination, such as reactive ion etching after deposition and amorphous to poly-Si crystallization in oxygen, will lead to improved IBC fabrication methods.

14 SOLAR ENERGY↗
DOE OSTI2021

Effect of Dopant Compensation on the Conductivity of the Intrinsic poly-Si Isolation Region in Passivated IBC Silicon Solar Cells

The performance of IBC solar cells depends on the ability of this region to electrically isolate the doped fingers so that shunting does not occur and reduce the cell fill factor. We report on simulations which model the region between the p- and n-type poly-Si fingers of interdigitated back contact (IBC) solar cells as a series of resistors extending from one doped finger to the other. We demonstrate that the existence of a well compensated region between the doped fingers is enough to prevent shunting and loss of cell performance, despite contamination of dopants from the opposing dopant fingers. We show through these simulations that a net doping concentration below ~1018 cm-3 will enable a high resistivity and identify the conditions under which this highly resistive region forms despite imperfect finger edges. Additionally, we apply this analysis to tails measured by time-of-flight secondary ion mass spectrometry and confirm this hypothesis for our experimentally measured tails.

41 EE - Solar Energy Technologies Office (EE-4S)↗
NASA NTRS2002

Current Status of High Performance Large Format Si:As IBC Detectors for SOFIA-like Applications

Airborne and space telescope astronomical observations in the 5-25 micrometer wavelength region, are critical for understanding the physical conditions, composition, chemistry, and excitation of many environments in the interstellar medium, external galaxies, solar system objects, extra-solar systems, and stars. The scientific impact is particularly unique in the 5-8 micrometer and 14-25 micrometer regions which are inaccessible or poorly observed from ground-based observatories. Large-format area mid-infrared (MIR) detectors sensitive over these wavelengths and operable under moderate backgrounds (greater than 10(circumflex)6 e-/s at R=2000, 10(micrometers)) are essential for efficient large-area survey imaging and for taking moderate resolution spectra over a large spectral range. Both SOFIA and passively cooled Explorer observatories could benefit from this technology. Current first-light SOFIA instruments use small-format MIR FPA's of sizes 128x128 and 256x256, With the collaboration of Raytheon Infrared Operations (RIO), NASA-ARC has been testing the first device of this kind, a combination of 1) the ALADDIN III readout multiplexer, cryo-processed for 6K operation, with 2) SIRTF IRAC-like Sides IBC detector material. designed for higher QE and low dark current. Here we report requirements. design, and initial fabrication and testing of the first 1024x1024 Si:As IBC mid-IR detector array for these conditions. This device has exhibited low dark current, moderate noise levels, and greater than 200,000 electron linear well size at 6K operation. We conclude with suggestions for future device development for optimal performance under moderate background, SOFIA- and low Earth orbit observing conditions.

Ennico, Kimberly↗
NASA NTRSDate not supplied

Improved Breathing Cartridge (IBC)

The Fire Cartridge (FC) is designed to work with the Emergency Mask (EM) to protect the crew by cleaning the inhaled air in a post fire environment. The Improved Breathing Cartridge (IBC) is designed as a next generation FC with the lessons learned from years of building and testing the FC design, as well as novel catalyst materials to improve the performance and robustness of the cartridge. The FC was designed with minimal margin to save on mass, while the IBC was sized to have over 100% excess catalyst to achieve the required conversion, and still reduce the production cost. Kinetic data taken from another project was used to size the catalyst bed from the standard plug flow reactor conversion equation. The cartridge has been 3D printed and will soon be filled with the required levels of media. Testing has not yet been performed to determine final performance.

Fire Response↗
DOE OSTI2022

Dopant Compensation within the Intrinsic Poly-Si Isolation Region in Poly-Si/SiOx Passivated IBC Si Solar Cells

We report on the effect of dopant compensation within intrinsic poly-Si regions between p- and n-type fingers of poly-Si/SiOx passivated interdigitated back contact (IBC) solar cells using intrinsic poly-Si as the isolation region between the doped poly-Si fingers. First, we show that dopants from the doped fingers contaminate the intrinsic gap, resulting in doping of the entire intrinsic gap and overlap of the dopant tails from each finger. Next, we show that despite this doping across the gap, shunting between the doped fingers does not occur. We show that this is a result of trap-assisted compensation creating a highly resistive intrinsic region, preventing shunt. We simulate shunt resistance across the gap based on local carrier concentration and deep trap density. We show that trap defects within the poly-Si enhance compensation between the dopant tails. We experimentally confirm these predictions by scanning spreading resistance microscopy of the gap showing ~20 um domain with resistivity ~10^7 ..omega.. cm. Additionally, Kelvin probe force microscopy are compared to finite element simulations which result in the same approximate shape for potential profile, indicating diode behavior across the isolation region. These results demonstrate the powerful effect that trap defects have within the poly-Si isolation region and suggest that precision patterning is not as essential as once thought.

dopant compensation↗
NASA NTRS1994

Evaluation of a 256 x 256 Si:As IBC detector array for astronomy

256 x 256-element IBC Si:As arrays have been evaluated for applications in IR astronomy from space-borne platforms. Basic figures of merit were measured at IR flux levels simulating those expected in space-based astronomical observations. Results include dark current less than 20 e(-)/s, G-eta as high as 3.8, eta/beta of 20%, and read noise below 100 rms(e(-)).

Mckelvey, M. E.↗
NASA NTRS1994

IBC arrays: Present and future prospects

The development of arrays which operate at wavelengths longer than 8 micrometers has opened up new possibilities for imaging and spectroscopy but offers challenges not present at shorter wavelengths. Impurity Band Conduction (IBC) or Blocked-Impurity-Band (BIB) detectors can meet these challenges and offer numerous advantages over standard photoconductors. We review some of the general operating principles of these devices and discuss the current state of technology. We then discuss the requirements placed on mid-infrared arrays by groundbased, airborne and spacebased astronomy.

Herter, Terry↗
NASA NTRS1994

SN 1994I in M51 and the nature of type Ibc supernovae

Early spectra of SN 1994I in M51 (NGC 5194) are presented along with arguments that is a member of the class of helium-poor Type Ic supernovae. The issue of H and He in the spectra of Type Ib and Ic events is reexamined with the conclusion that Type Ib eject substantially less H than even transition events like SN 1993J and that Type Ic eject substantially less He than Type Ib and their optical spectra are consistent with no H or He. Type Ic show and absorption of the Si II lambda 6355 blend that characterizes Type Ia. This feature requires only a solar abundance of Si. Some Type Ic show an absorption that is probably C II lambda 6580. IR spectra are presented of SN 1990W which show the line of He I lambda 10830. The strength of this feature and the rather slow decay of the late time light curve suggest that this event could be better classified as a Type Ib. Even if trace abundances of H are present in Type Ib and of He in Type Ic the spectral differences still imply a distinctly different evolution for the progenitors of Type Ib from Type Ic and events like SN 1993J.

Wheeler, J. C.↗
NASA NTRS1990

Synthesis of individual rotor blade control system for gust alleviation

The utilization of rotor flapping in synthesizing an Individual Blade Control (IBC) system for gust alleviation is demonstrated. The objective is to illustrate and seek to improve Ham's IBC method. A sensor arrangement with two accelerometers mounted on the root and tip of a blade is proposed for estimating of flapping states for feedback control. Equivalent swash plate implementation of IBC is also deliberated. The study concludes by addressing the concept of general rotor states feedback, of which the IBC method is a special case. The blade flapping equation of motion is derived. Ham's original IBC method and a modified IBC scheme called Model Reference (MRIBC) are examined, followed by simulation study with ideal measurements and relative performances of the two methods. The practical aspects of IBC implementation are presented. Different configuration of sensors and their merits are considered. The realization of IBC using equivalent swash plate instead of direct actuator motion is discussed. It is shown that IBC is a particular case of rotor states feedback. The idea of general rotor states feedback is further elaborated. Finally, major conclusions are given.

Wang, Ji C.↗