Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “hydrogen pump”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Space-based laser-powered orbital transfer vehicle (Project SLICK)

The project SLICK (Space Laser Interorbital Cargo Kite) involves conceptual designs of reusable space-based laser-powered orbital transfer vehicle (LOTV) for ferrying 16,000 kg cargo primarily between low Earth orbit (LEO) and geosynchronous earth orbit (GEO). The power of LOTV is beamed by a single 32-MW solar-pumped iodide laser orbiting the Earth at an altitude of one Earth radius. The laser engine selected for the LOTV is based on a continuous-wave, steady-state propulsion scheme and uses an array of seven discrete plasmas in a flow of hydrogen propellant. Both all-propulsive and aerobraked LOTV configurations were analyzed and developed. The all-propulsive vehicle uses a rigid 11.5-m aperture primary mirror and its engine produces a thrust of 2000 N at a specific impulse of 1500 sec. For the LEO-to-GEO trip, the payload ratio, m(sub payload/m(sub propellant)+m(sub dry vehicle) = 1.19 and the trip time is about 6 days. The aerobraked version uses a lightweight, retractable wrapped-rib primary mirror which is folded for aerobraking and a 20-m-diameter inflatable-ballute aeroshield which is jettisoned after aeromaneuver. Lifecycle cost analysis shows that the aerobraked configuration may have an economic advantage over the all-propulsive configuration as long as the cost of launching the propellant to LEO is higher than about $500/kg in current dollars.

Source record↗
NASA NTRS2014

Current Ground Test Options for Nuclear Thermal Propulsion (NTP)

About 20 different NTP engines/ reactors were tested from 1959 to 1972 as part of the Rover and Nuclear Engine for Rocket Vehicle Application (NERVA) program. Most were tested in open air at test cell A or test cell C, at the Nevada Test Site (NTS). Even after serious engine breakdowns of the reactor (e.g., Phoebus 1A), the test cells were cleaned up for other engine tests. The engine test stand (ETS) was made for high altitude (approximately 1 psia) testing of an NTP engine with a flight configuration, but still had the exhaust released to open air. The Rover/NERVA program became aware of new environmental regulations which would prohibit the release of any significant quantity of radioactive particulates and noble gases into the open air. The nuclear furnace (NF-1) was the last reactor tested before the program was cancelled in 1973, but successfully demonstrated a scrubber concept on how to filter the NTP exhaust. The NF-1 was demonstrated in the summer of 1972. The NF-1 used a 44MW reactor and operated each run for approximately 90 minutes. The system cooled the hot hydrogen exhaust from the engine with a water spray before entering a particle filter. The exhaust then passed through a series of heat exchangers and water separators to help remove water from the exhaust and further reduce the exhaust temperatures. The exhaust was next prepared for the charcoal trap by passing through a dryer and effluent cooler to bring exhaust temperatures close to liquid nitrogen. At those low temperatures, most of the noble gases (e.g., Xe and Kr made from fission products) get captured in the charcoal trap. The filtered hydrogen is finally passed through a flare stack and released to the air. The concept was overall successful but did show a La plating on some surfaces and had multiple recommendations for improvement. The most recent detailed study on the NTP scrubber concept was performed by the ARES Corporation in 2006. The concept is based on a 50,000 lbf thrust engine (approximately 1 GW) with a maximum burn time of 1 hour. The concept utilized lessons learned from NF-1. The strategy breaks down the exhaust into parallel paths to allow flexibility with engine size and mass flow of exhaust. Similar to NF-1, the exhaust is slowed down, cooled, filtered of particulates, filtered of noble gases, and then the clean hydrogen is flared to open air. Another concept proposed by Steve Howe (currently Director of the Center for Space Nuclear Research) to simplify the NTP exhaust filtering is to run the hydrogen exhaust into boreholes underground to filter the exhaust. The two borehole site locations proposed are at the NTS and at the Idaho National Laboratory (INL). At NTS, the boreholes are 8' diameter and 1200' deep. The permeability of hydrogen through the soil and its buoyancy will allow it to rise up through the soil and allow the filtering of noble gases and radioactive particulates. The exhaust needs to be cooled to 600C before entering the borehole to avoid soil glazing. Preliminary analysis shows a small buildup of back pressure with time which depends on permeability. Noble gases entering the borehole walls deep can take a long time before reaching the surface. Other factors affecting permeability include borehole pressure, water saturation, and turbulence. Also, a possible need to pump out contaminated water collected at the bottom of the borehole. At INL, the borehole concept is slightly different. The underground borehole has openings to the soil at special depths which have impermeable interbeds above the water table and below the surface to allow the exhaust to travel horizontal between the impermeable layers. Preliminary results indicate better permeability than at NTS. The last option is total containment of the exhaust during the test run. The concept involves slowing down the flow to subsonic in a water cooled diffuser. The hydrogen is burned off in an oxygen rich afterburner with the only products being steam, oxygen, and some noble gases. A heat exchanger and water spray pulls heat from the steam and lowers the temperature for condensation. The optimum ratio between the two is being investigated, with a goal to minimize the total volume of the water hold tanks. A water tank farm collects the contaminated water. The amount of water produced from burning the hydrogen is approximately 100,000 gallons (not including cooling water) for a 25k lbf engine operating for 50 minutes. Residual gases (e.g., oxygen and some noble gases) can be captured at cryogenic levels with a liquid nitrogen cooled dewar. After a few weeks post-test, the radiation levels can drop to more favorable levels before slowly draining each capture tank and using existing filters. With today's environmental regulations, the NTP exhaust is filtered to meet 10 mrem/year exposure to the general public (at a DOE site) or 100 mrem/year (via NRC when tested elsewhere), when natural background radiation exposure to the general public is 300- 600 mrem per year. The current society feels more comfortable with filtering even lower to as low as reasonably achievable (ALARA).

Gerrish, Harold P., Jr.↗
NASA NTRS2010

Width-Increased Dual-Pump Enhanced Coherent Anti-Stokes Raman Spectroscopy (WIDECARS)

WIDECARS is a dual-pump coherent anti-Stokes Raman Spectroscopy technique that is capable of simultaneously measuring temperature and species mole fractions of N2, O2, H2, C2H4, CO, and CO2. WIDECARS is designed for measurements of all the major species (except water) in supersonic combustion flows fueled with hydrogen and hydrogen/ethylene mixtures. The two lowest rotational energy levels of hydrogen detectable by WIDECARS are H2 S(3) and H2 S(4). The detection of these lines gives the system the capability to measure temperature and species concentrations in regions of the flow containing pure hydrogen fuel at room temperature.

Tedder, Sarah A.↗
NASA NTRS2010

Width-Increased Dual-Pump Enhanced Coherent Anti-Stokes Raman Spectroscopy (WIDECARS)

WIDECARS is a dual-pump coherent anti-Stokes Raman Spectroscopy technique that is capable of simultaneously measuring temperature and species mole fractions of N2, O2, H2, C2H4, CO, and CO2. WIDECARS is designed for measurements of all the major species (except water) in supersonic combustion flows fueled with hydrogen and hydrogen/ethylene mixtures. The two lowest rotational energy levels of hydrogen detectable by WIDECARS are H2 S(3) and H2 S(4). The detection of these lines gives the system the capability to measure temperature and species concentrations in regions of the flow containing pure hydrogen fuel at room temperature.

Tedder, Sarah A.↗
DOE OSTI2022

Characterisation of divertor detachment onset in JET-ILW hydrogen, deuterium, tritium and deuterium–tritium low-confinement mode plasmas

Measurements of the ion currents to and plasma conditions at the low-field side (LFS) divertor target plate in low-confinement mode plasmas in the JET ITER-like wall materials configuration show that the core plasma density required to detach the LFS divertor plasma is independent of the hydrogenic species protium, deuterium and tritium, and a 40 %/60 % deuterium–tritium mixture. This observation applies to a divertor plasma configuration with the LFS strike line connected to the horizontal part of the LFS divertor chosen because of its superior diagnostic coverage. The finding is independent of the operational status of the JET cryogenic pump. The electron temperature (T e ) at the LFS strike line was markedly reduced from 25 eV to 5 eV over a narrow range of increasing core plasma density, and observed to be between 2 eV and 3 eV at the onset of detachment. The electron density (n e ) peaks across the LFS plasma when T e at the target plate is 1 eV, and spatially moves to the X-point for higher core densities. The density limit was found approximately 20 % higher in protium than in tritium and deuterium–tritium plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2004

Dual-Pump CARS Thermometry and Species Concentration Measurements in a Supersonic Combustor

The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) method was used to measure temperature and the absolute mole fractions of N2, O2 and H2 in a supersonic combustor. Experiments were conducted in NASA Langley Research Center's Direct Connect Supersonic Combustion Test Facility. In this facility, hydrogen and air bum to increase the enthalpy of the test gas; O2 is then added to simulate air. This gas is expanded through a Mach 2 nozzle and into a combustor model consisting of a short constant-area section followed by a small rearward facing step and another constant area section. At the end of this straight section H2 fuel is then injected at Mach 2 and at 30 deg. angle with respect to the freestream. One wall of the duct then expands at a 3 deg. angle for over 1 meter. The ensuing combustion is monitored optically through ports in the side of the combustor. CARS measurements were performed at the nozzle exit and at four different planes downstream fuel injection. Maps were obtained of the mean temperature, as well as quantitative N2 and O2 and qualitative H2 mean mole fraction fields. Correlations between fluctuations of the different measured parameters are presented for one of the planes of data.

OByrne, Sean↗
NASA NTRS2004

Improved Method of Purifying Carbon Nanotubes

An improved method of removing the residues of fabrication from carbon nanotubes has been invented. These residues comprise amorphous carbon and metal particles that are produced during the growth process. Prior methods of removing the residues include a variety of processes that involved the use of halogens, oxygen, or air in both thermal and plasma processes. Each of the prior methods entails one or more disadvantages, including non-selectivity (removal or damage of nanotubes in addition to removal of the residues), the need to dispose of toxic wastes, and/or processing times as long as 24 hours or more. In contrast, the process described here does not include the use of toxic chemicals, the generation of toxic wastes, causes little or no damage to the carbon nanotubes, and involves processing times of less than 1 hour. In the improved method, purification is accomplished by flowing water vapor through the reaction chamber at elevated temperatures and ambient pressures. The impurities are converted to gaseous waste products by the selective hydrogenation and hydroxylation by the water in a reaction chamber. This process could be performed either immediately after growth or in a post-growth purification process. The water used needs to be substantially free of oxygen and can be obtained by a repeated freeze-pump-thaw process. The presence of oxygen will non-selectively attach the carbon nanotubes in addition to the amorphous carbon.

Delzeit, Lance D.↗
NASA NTRS1990

Project LOCOST: Laser or Chemical Hybrid Orbital Space Transport

A potential mission in the late 1990s is the servicing of spacecraft assets located in GEO. The Geosynchronous Operations Support Center (GeoShack) will be supported by a space transfer vehicle based at the Space Station (SS). The vehicle will transport cargo between the SS and the GeoShack. A proposed unmanned, laser or chemical hybrid orbital space transfer vehicle (LOCOST) can be used to efficiently transfer cargo between the two orbits. A preliminary design shows that an unmanned, laser/chemical hybrid vehicle results in the fuel savings needed while still providing fast trip times. The LOCOST vehicle receives a 12 MW laser beam from one Earth orbiting, solar pumped, iodide Laser Power Station (LPS). Two Energy Relay Units (ERU) provide laser beam support during periods of line-of-sight blockage by the Earth. The baseline mission specifies a 13 day round trip transfer time. The ship's configuration consist of an optical train, one hydrogen laser engine, two chemical engines, a 18 m by 29 m box truss, a mission-flexible payload module, and propellant tanks. Overall vehicle dry mass is 8,000 kg. Outbound cargo mass is 20,000 kg, and inbound cargo mass is 6,000 kg. The baseline mission needs 93,000 kg of propellants to complete the scenario. Fully fueled, outbound mission mass is 121,000 kg. A regeneratively cooled, single plasma, laser engine design producing a maximum of 768 N of thrust is utilized along with two traditional chemical engines. The payload module is designed to hold 40,000 kg of cargo, though the baseline mission specifies less. A proposed design of a laser/chemical hybrid vehicle provides a trip time and propellant efficient means to transport cargo from the SS to a GeoShack. Its unique, hybrid propulsion system provides safety through redundancy, allows baseline missions to be efficiently executed, while still allowing for the possibility of larger cargo transfers.

Dixon, Alan↗
NASA NTRS1993

The Ca II emission lines of SN 1987A

We study the evolution of the forbidden Ca II 7300 A and Ca II 8600 A emission lines in the spectrum SN 1987A. We can explain the observations with a model in which (1) the lines come from about 1.7 x 10 exp -4 solar mass of calcium distributed with filling factor about 0.1 in a sphere expanding with velocity 2500 km/s; (2) the electron number density is given by 4 x 10 exp 9/cu cm/(t/100d)-cubed; (3) the gas temperature decreases from T roughly 6400 K at 200 days to T roughly 3900 K at 500 days; and (4) ultraviolet pumping in the Ca II 3934 A, 3969 A (K, H) lines is required to explain the line ratios for t greater than about 350 days. The mass of calcium in our model is consistent with the LMC abundance of calcium in about 5 solar mass of hydrogen in the inner envelope of SN 1987A. If more calcium is produced by supernova nucleosynthesis, it must be in dense clumps that are too cool to emit the forbidden Ca II 7300 A and Ca II 8600 A lines.

Li, Hongwei↗
NASA NTRS1993

Design of an oxygen turbopump for use in an Advanced Expander Test Bed engine

A liquid oxygen (LOX) turbopump with a gaseous hydrogen turbine drive was designed for the Advanced Expander Test Bed (AETB), which is a technology test bed to develop future space engines. This turbopump features a single stage, full admission, high reaction turbine: a three-bladed axial flow inducer, a high efficiency single stage centrifugal pump with an integrally shrouded impeller; an interpropellant seal package with an oxygen vaporizer; and a subcritical rotor with two ball bearings for axial loads and one roller bearing for turbine radial loads. Material selections were based on compatibility with operating fluids and temperatures. The pump was designed to operate over a 20:1 power range with a maximum performance point of 283.0 GPM of liquid oxygen at a pump discharge pressure of 2198 psia, and a shaft speed of 47,914 rpm. The split expander cycle engine and the performance it requires of the LOX turbopump is discussed as well as the design of the turbopump components.

Pattison, William W.↗
DOE OSTI2020

Structure of the respiratory MBS complex reveals iron-sulfur cluster catalyzed sulfane sulfur reduction in ancient life

Abstract Modern day aerobic respiration in mitochondria involving complex I converts redox energy into chemical energy and likely evolved from a simple anaerobic system now represented by hydrogen gas-evolving hydrogenase (MBH) where protons are the terminal electron acceptor. Here we present the cryo-EM structure of an early ancestor in the evolution of complex I, the elemental sulfur (S 0 )-reducing reductase MBS. Three highly conserved protein loops linking cytoplasmic and membrane domains enable scalable energy conversion in all three complexes. MBS contains two proton pumps compared to one in MBH and likely conserves twice the energy. The structure also reveals evolutionary adaptations of MBH that enabled S 0 reduction by MBS catalyzed by a site-differentiated iron-sulfur cluster without participation of protons or amino acid residues. This is the simplest mechanism proposed for reduction of inorganic or organic disulfides. It is of fundamental significance in the iron and sulfur-rich volcanic environments of early earth and possibly the origin of life. MBS provides a new perspective on the evolution of modern-day respiratory complexes and of catalysis by biological iron-sulfur clusters.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Hydrogen-Bonded Organic Framework Enables Phase-Pure Layered Tin Perovskite Nanowires for Room-Temperature Lasing

Room-temperature lasing is a key milestone in the development of miniaturized optoelectronic and photonic devices. We present a simple approach to synthesize phase-pure quasi-2D layered tin perovskite nanowires with varying quantum well thicknesses (n = 1 to 4). By incorporating a new organic spacer capable of forming a hydrogen-bonded organic framework, this method promoted anisotropic crystal growth and enhanced lattice rigidity. Furthermore, introducing molecular intercalants enabled controlled crystallization into well-defined nanowires that function as Fabry−Pérot cavities. Cavities made from n = 2 to 4 perovskites support efficient and robust nearinfrared, room-temperature optically pumped lasing with the threshold as low as 75.8 μJ/cm 2 , cavity quality factor over 3000, and negligible degradation over 106 pulses. A cleaved coupled nanolaser was fabricated as a proof-of-concept device for photonic applications.

Cavities↗
NASA NTRS1988

Space-based laser-powered orbital transfer vehicle (Project SLICK)

A conceptual design study of a laser-powered orbital transfer vehicle (LOTV) is presented. The LOTV, nicknamed SLICK (Space Laser Interorbital Cargo Kite), will be utilized for the transfer of 16000 kg of cargo between Low Earth Orbit (LEO) and either Geosynchronous Earth Orbit (GEO) or Low Lunar Orbit (LLO). This design concentrates primarily on the LEO/GEO scenario, which will have typical LEO-to-GEO trip time of 6 days and two return versions. One version uses an all propulsive return while the other utilizes a ballute aerobrake for the return trip. Furthermore, three return cargo options of 16000 kg, 5000 kg (standard option), and 1600 kg are considered for this scenario. The LEO/LLO scenario uses only a standard, aerobraked version. The basic concept behind the LOTV is that the power for the propulsion system is supplied by a source separate from the LOTV itself. For the LEO/GEO scenario the LOTV utilizes a direct solar-pumped iodide laser and possibly two relay stations, all orbiting at an altitude of one Earth radius and zero inclination. An additional nuclear-powered laser is placed on the Moon for the LEO/LLO scenario. The propulsion system of the LOTV consists of a single engine fueled with liquid hydrogen. The laser beam is captured and directed by a four mirror optical system through a window in the thrust chamber of the engine. There, seven plasmas are created to convert the laser beam energy into thermal energy at an efficiency of at least 50 percent. For the LEO/LLO scenario the laser propulsion is supplemented by LH2/LOX chemical thrusters.

Source record↗
DOE OSTI2021

Examining Thermolytic Production of Hydrogen from Lubrication Oil

Savannah River National Laboratory (SRNL) was requested by Savannah River Remediation (SRR) to conduct testing via Technical Task Request (HR) to determine the thermolytic HGR of Mobil SHC™ 630, a lubrication oil. Currently, 35 gallons of contaminated Mobil SHC 630 is proposed for release into the recycle stream from the Defense Waste Processing Facility (DWPF) to Tank 22 and then to the 242-16H (2H) Evaporator system. Inhibited recycle waste in the Recycle Collection Tank (RCT) is transferred to Recycle Pump Tank (RPT) in the Low Point Pump Pit (LPPP) and then to the Concentration, Storage and Transfer Facilities (CSTF) H-area. The lubrication oil would be added directly to the RPT, bypassing the RCT. The current DWPF waste compliance plan for liquid transfers from the RCT to the CSTF limits the concentration of Mobil SHC 630 to <1,100 ppm which is equal to <9.3 gallons of Mobil SHC 630 when considering a 7,500 gal RCT batch with an initial Mobil SHC 630 concentration of 42 mg/L. Mobil SHC 630 is expected to be largely immiscible in the caustic aqueous waste stream. It is a blend of base oils including polyalphaolefin (PAO) base oil and additives such as triphenylphosphate and cresyl diphenyl phosphate at various concentrations (<0.25 wt%). While the base oils are expected to be largely unreactive in CSTF waste, the triarylphosphates additives would be expected to hydrolyze in the caustic waste, forming diarylphosphates and phenol. The tests described herein were governed by a single Run Plan and will determine thermolytic HGR from the caustic aqueous solution, as well as from any organic phases present.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1985

A comparison of Doppler lidar wind sensors for Earth-orbit global measurement applications

Now, there are four Doppler lidar configurations which are being promoted for the measurement of tropospheric winds: (1) the coherent CO2 Lidar, operating in the 9 micrometer region using a pulsed, atmospheric pressure CO2 gas discharge laser transmitter, and heterodyne detection; (2) the coherent Neodymium doped YAG or Glass Lidar, operating at 1.06 micrometers, using flashlamp or diode laser optical pumping of the solid state laser medium, and heterodyne detection; (3) the Neodymium doped YAG/Glass Lidar, operating at the doubled frequency (at 530 nm wavelength), again using flashlamp or diode laser pumping of the laser transmitter, and using a high resolution tandem Fabry-Perot filter and direct detection; and (4) the Raman shifted Xenon Chloride Lidar, operating at 350 nm wavelength, using a pulsed, atmospheric pressure XeCl gas discharge laser transmitter at 308 nm, Raman shifted in a high pressure hydrogen cell to 350 nm in order to avoid strong stratospheric ozone absorption, also using a high resolution tandem Fabry-Perot filter and direct detection. Comparisons of these four systems can include many factors and tradeoffs. The major portion of this comparison is devoted to efficiency. Efficiency comparisons are made by estimating the number of transmitted photons required for a single pulse wind velocity estimate of + or - 1 m/s accuracy in the middle troposphere, from an altitude of 800 km, which is assured to be reasonable for a polar orbiting platform.

Menzies, Robert T.↗
NASA NTRS2016

Generalized Fluid System Simulation Program, Version 6.0

The Generalized Fluid System Simulation Program (GFSSP) is a general purpose computer program for analyzing steady state and time-dependent flow rates, pressures, temperatures, and concentrations in a complex flow network. The program is capable of modeling real fluids with phase changes, compressibility, mixture thermodynamics, conjugate heat transfer between solid and fluid, fluid transients, pumps, compressors, and external body forces such as gravity and centrifugal. The thermofluid system to be analyzed is discretized into nodes, branches, and conductors. The scalar properties such as pressure, temperature, and concentrations are calculated at nodes. Mass flow rates and heat transfer rates are computed in branches and conductors. The graphical user interface allows users to build their models using the 'point, drag, and click' method; the users can also run their models and post-process the results in the same environment. Two thermodynamic property programs (GASP/WASP and GASPAK) provide required thermodynamic and thermophysical properties for 36 fluids: helium, methane, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, fluorine, hydrogen, parahydrogen, water, kerosene (RP-1), isobutene, butane, deuterium, ethane, ethylene, hydrogen sulfide, krypton, propane, xenon, R-11, R-12, R-22, R-32, R-123, R-124, R-125, R-134A, R-152A, nitrogen trifluoride, ammonia, hydrogen peroxide, and air. The program also provides the options of using any incompressible fluid with constant density and viscosity or ideal gas. The users can also supply property tables for fluids that are not in the library. Twenty-four different resistance/source options are provided for modeling momentum sources or sinks in the branches. These options include pipe flow, flow through a restriction, noncircular duct, pipe flow with entrance and/or exit losses, thin sharp orifice, thick orifice, square edge reduction, square edge expansion, rotating annular duct, rotating radial duct, labyrinth seal, parallel plates, common fittings and valves, pump characteristics, pump power, valve with a given loss coefficient, Joule-Thompson device, control valve, heat exchanger core, parallel tube, and compressible orifice. The program has the provision of including additional resistance options through User Subroutines. GFSSP employs a finite volume formulation of mass, momentum, and energy conservation equations in conjunction with the thermodynamic equations of state for real fluids as well as energy conservation equations for the solid. The system of equations describing the fluid network is solved by a hybrid numerical method that is a combination of the Newton-Raphson and successive substitution methods. The application and verification of the code has been demonstrated through 30 example problems.

Majumdar, A. K.↗
NASA NTRS1973

Liquid hydrogen turbopump rapid start program

Effort was directed toward the completion of the coated feed system testing and data analysis of both the uncoated and coated system tests. A total of 11 tests were conducted with the coated feed system during three days of testing. Chill data was acquired for thermal conditioning of the system from ambient initial conditions, using a duct inlet propellent pressure of 72 psig. After three tests to determine steady state pump performance and nominal start transient operation, three coated system turbopump starts were attempted with various degrees of prechill.

Wong, G. S.↗
NASA NTRS1986

Linewidth characteristics of Raman-shifted dye laser output at 720 and 940 nm

Existing DIAL systems for water vapor measurements in the troposphere operate at wavelengths near 720 nm. The use of stronger water vapor absorption lines in the range 930 to 960 nm will significantly improve DIAL measurements in the upper troposphere and lower stratosphere where water vapor concentrations are low. The generation of light at 940 nm using a frequency doubled Nd:YAG pumped dye laser is inefficient due to the small absorption if infrared dyes at the pump wavelength. However, 940 nm generation utilizing stimulated Raman scattering of dye lasers is attractive because of a potentially high conversion efficiency plus the possibility of retaining the narrow linewidth available from some dye lasers. The Raman conversion efficiency and line broadening are presented for first Stokes operation at 720 and 940 nm using hydrogen and deuterium as the Raman media.

Grossmann, B. E.↗