DEUTERIUM FLUORIDE CW CHEMICAL Leroy Wilson

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Leroy Wilson. DEUTERIUM FLUORIDE CW CHEMICAL LASERS. Journal de Physique Colloques, 1980, 41 (C9), pp.C9-1-C9-8. ￿10.1051/jphyscol:1980901￿. ￿jpa-00220555￿

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DEUTERIUM FLUORIDE CW CHEMICAL LASERS

Leroy E. Wilson

Air Force Weapons Laboratory, KirtZand Air Force Base, New Mexico 120).

Abstract.- This article summarizes the current performance and understanding of deuterium fluoride (DF) cw chemical lasers. The fundamental principles of the are explained. The advantages and disadvantages of the laser system are discussed. The characteristics of the DF laser beam, the perfor- mance parameters and operating characteristics are enumerated.

Introduction 1. Other products, HF, CFq, N2, etc., are also produced depending upon other chemical processes, Laser emission from a hydrogen chloride the heat loss and the combustor gas temperature and chemical laser, the first chemical laser, was pressure. Although the use of NF3 reduces laser experimentally observed in 1965 (1). Since that power by %IS%,most DF laser applications will time many vibrational transition and a few elec- require its use for safety reasons. Since NF3 is tronic transition chemical lasers have been dis- relatively expensive at this time, most laboratory covered and developed. Several recent and general experiments have used elemental F2 plus a low reviews of these em'c lase s are available in molecular weight hydrocarbon to produce the F-atoms. the literature. (Sf(3ftH (5) (8 me deuterium Laser perfonnance data withNF3 used in the combustor fluoride (DF) laser has been extensively developed will be described in this paper. The reaction in for atmospheric pressure recovery and is nearing equation 1 is hypergolic and very fast. The D2 is its optimum lasing perfonnance in this application. added to the supersonic stream of F atoms at the This article summarizes the state of the art of exit plane of the nozzle bank in a mixing-limited cw DF lasers. process to produce vibrationally excited DF*. This is shown schematically in Figure 2A which shaws the A chemical laser operates on a population top view of the nozzle bank and the zones of excited inversion produced - directly or indirectly - in DF*. The "trip" holes produce small jets of He which the course of an exothermic . In create vortex mising increasing the net mixing this case the excited molecules are produced in rate and producing laser power 1.8 times over non- five vibrational states by the exothermic reaction perturbed nozzle banks. The mixing of the oxidiz'er and fuel streams produces a translationally cold temperature flame (nominally 3000K) of products in which the DF is vibrational excited to an equivalent which takes place at the exit plane of the nozzle vibrational temperature of greater than 10,000oK. bank shown in Figure 1. The vibrational population is prodced in a tri: angula+ peaked distribution with the maximum population in v = 3 and 4. It is important to note again that this nonequilibrium population is rate limited by the mixlng rate of the D2 and F reactants. The excited DF* species are collisionally deacti- vated in the lasing zone by other species. The OPTICS principal deactivators, in both concentration and fast rate coefficients, are DF itself, HF products fmm the combustor, excess D2 and F-atoms . The reaction rates for these interactions and over 100 other possible reactions are given in reference (7). It is not the purpose of this paper to explain the complicated interactions in the lasing cavity between the fluid mechanics, chemistry and the optical , although what happens can be easily explained in a global sense. All the parti- \ \ LOX '- -- cles pass by the optical aperture (lasing zone length) in 20 to 50 microseconds degiing upon their history. In that period of time there is Figure 1. Schematic of DF Laser sufficient reactant mixing and DF* production to allow the resonator to extract a specific power of 90 kj for each kg that passes the aperature. During this residence tine the created DF* is de- activated twoards ground state by lasing and colli- The fluorine atoms, F, are produced in a com- sional processes. In addition, the heat release bustor from the reaction of excess NF3 or F2 and increases the gas translational temperature from C2H4 or; other hydrocarbon fuels with helium (He) aperture entrance to exit which decreases the diluent to produce typically 90 percent F-atoms available inversion. with respect to the available fluorine for equation

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980901 JOURNAL DE PHYSIQUE

supersonic flow field to passively recover to 200 "Trip" Holes to 300 torr, depending upon the configuration, which then needs to be pmped at: high volume flow rates to atmospheric pressure. Although axial flow pumps are a possibility for very long run times, only jet pumps (ejectors - see Figure 1) and mechanical pumps have been used. Although the 1-120 reactants are easily bottled and handled (including NQ), the products contain DF which is a mild acid "2 which can easily be scrubbed from the effluent condensibles by several methods.

Current laser operating fuel costs are $2/h kw for each second of run time with NF3 as the fluorine source. At industrial usage rates that cost should decrease to $l.oO/kw per second. DF Beam Characteristics and Optics The CW DF laser beam has a multiline spectrum of P branch transitions between different vibra- CAVITY FUEL/DILUENT tional and rotational levels as shm in Figure 3. AND COOLANT Single lines have been extracted by using a diffraction grating as an outcoupling mirror. Single-line output powers are 10 and 20 percent of total multiline power. (8) Zero power measure- ments have been made for several of the transitions P2 (4). . . P2 (8) shown in Figure 3. Peak gain is

LUORINE NOZZLE

CAVITY FUEL/ Dl LUENT NOZZLE FLUORINE NOZZLE B WAVELENGTH (MICRONS)

Figure 2. Schematics of DF Laser Nozzle Banks Figure 3. Representative Simultaneous DF Laser (A) Top View Showing F, D2 and DF* Transitions Showing Relative Power of Supersonic Streams with Nozzle Lines Dimensions in Inches an an (B) Regeneratively Cooled Nozzle typically 10 percent per at 1 to 2 downstream of the nozzle exit plane. (9) The gain falls off rapidly downstream of the peak value due to all of cw the competing processes deactivating the lasing The obvious fundamental advantage of a species, giving rise to asynnnetric gain distribu- chemical laser compared to electrical powered tions. The lasing zone length in the flow lasers is that it obtains its laser power from direction is typically 5 an. Although the peak combustion. But it is then limited by finite and zero power gain is high, parasitic oscillations practicable reactant tankage for long device run have not been a problem because the times. Irreversible chemical processes demand are designed to saturate all of the gain medium. the removal of expended gases from the laser making continuous recirculated flow impossible. CW chemical lasers are phenomenologically complex Confocal unstable resonators similar to Figure interactions between the chemical kinetics, fluid 4 extract the DF laser beam. Rectangular scrapers dynamics, optics and laser physics. The devices are used to match the rectangular gain medium with are simple but highly engineered, and are still the laser mode volume. The outcoupling generally relatively expensive to manufacture. The nominal optimizes for near-f ield power' between 60 and 75 3.8 micron DF wavelength can be focused to higher percent. The mirrors are molybdenum substrate, far field intensities than the CX)2 laser and triple pass water cooled, with silver or gold propagates well through the atmosphere. (8) . coated reflective surfaces with ThF4 coatings for pro- tection from the environment. Also high reflective The greatest disadvantage of a cw DF laser is multilayer dielectric coatings of Zn Se and ThF4 its inability to recover pressure to one atmosphere with reflectivities of 0.999 have been used at peak without pwrps. The average lasing zone pressure intracavity fluxes as high as 60 kw/an2. The non- is 20 torr with sufficient momentum in the gain volumes in the resonator are purged with He gas to prevent absorbing ground state DF species from circulating in those cavity spaces.

CONVEX MIRROR

c,,,, c,,,, /;p; INJECTOR

Figure 4. Typical Chemical Laser Enstable Resonator for Power Extraction The near-field laser output from the scraper is similar to the multiline intensity profile shown in Figure 5A. The near-field intensity dis- tribution has a rectangular hole in the center which is a projection of the scraper hole as shown in Figure 4. The near-field peak intensities are several times the average intensity. When the beam is propagated to the far-field and squared up with cylindrical optics, the intensity profile is similar to Figure 5B. A multiline diffraction limited DF beam has been observed on a 2 kw laser. (10) Figures 5A and 5B are computer code predictions (11) which have been qualitatively verified by burn patterns in plexiglass blocks. Chemical lasers have good lasing media quality because of the lower density and small density gradients of the lasing gases. Nozzle banks like-those in Figure 2 have media quality less than A(DF)/50 over an 8 inch path length. (12) DF Laser Operating Characteristics Deuterium fluoride lasers can be characterized by several performance parameters as shown in Figure 5. (A) Calculated Near-Field Intensity Figure 6. The specific power, o, expressed in Profile from Scraper kilowatts of nearfield laser power out of the (B) Calculated Far-Field Intensity Profile device divided by the total. mass flow into the D2 IN TRIP laser (excluding the ejector) varies from 45- to 90 kj/kg. For a given amount of device run time and total power leve1,this specifies the total mass of reactants required and the size of the reactant fluid supply tanks. The nozzle bank power flux, 100 - 6, in kilowatts per square inch of nozzle exit area 2 varies from 125 to 225 w/m . Hence for a specified SPECIFIC power level, 6 gives the required nozzle bank area. POWER 80- Current fabrication techniques produce structurally sound nozzles from 1to 10 inches in height. With a chosen height, the length of the nozzle bank and 60 - hence the laser size and the fabrication costs are specified. Current nozzle banks cost several hundred dollars per square inch. The third para- meter is the passive recovered pressure which I I I I varies from 100 to 300 torr. This specifies the 100 150 200 250 necessary mass flow rate of the ejector to recover POWER FLUX 6 WATTSICM~ to one atmosphere. Experimentally, 80 percent of Figure 6. DF Chenical Laser Perfoimance normal shock total pressure measured at the C9-4 JOURNAL DE PHYSIQUE

entrance to the diffuser throat is recovered to Using these parameters,conditions for the per- static pressure. All of the parameters a, 6, and formance curve of figure 6 are: P (recovered) are dependent on the mass flow which is independently varied in a given device. The mass flow is increased by raising the combustor pressure which results in increased lasing cavity pressure. This increases the deactivation of the lasing species DF and causes the efficiency, a, of the device to decrease as shown in Figure 6. In other words, the energy extracted from the laser decreases for the mount of F-atoms that are pro- vided by the combustor. In order to achieve high The combustor products with a specific heat efficiency and good beam quality in a chemical ratio of typically 1.62 are expanded in frozen flow laser it is necessary to use low lasing cavity through the fluorine nozzles which have an exit pressure and supersonic flow to remove the vibra- area to throat area ratio of 23.- This expansion tionally deactivated DF from the lasing zone at a produces 16S°K products which have a mean flow high rate and to start the chemical reaction of velocity of 1900 meterslsec at 9 torr. This flow Equation 1 at a low translational temperature. is presented to a parallel supersonic flow of D2 and He (see Figure 2) which is expanded in a nozzle The combustor's purpose is to produce fluorine of area ratio 20 to 8.2 torr resulting in an exit atoms. This is accomplished by burning a fluorine mean velocity of 2245 meterslsec and a temperature source and a light molemar weight hydrocarbon of 91oK. These two streams, having an oxidizer to such as the reactants F2 and C2H4 with He diluent. fuel ratio of 1.67, are then mixed, primarily by diffusion and vortex action from the T1triptljets, The operating conditions can be expressed in producing excited state DFX (see Equation I). a general fashion by defining several key molar flow ratios. These ratios provide a set of Simplified mixing models for the prediction of standard operating conditions for which the mass chemical laser behavior have been independently flows can be determined by simple thermochemical developed by road well (13) (14) at TRW and by Mirels calculations for numerous possible reactant (15) at Aerospace Corporation. As originally ex- combinations. These are: pressed the Broadwell formulation was in the form:

$, = Total molar combustor dibent ratio

Moles diluent + Moles combustor - products where K = proportionality constant Moles excess fluorine as F2 a = mixing spread angle U = average stream velocity p = concentration of F atoms - - = deactivation rate of excited 'Gn: states - L = nozzle exit width fi = Total laser molar diluent ratio M (J,er/T) = functional parameter depen- dent on rotational quantum Combustor diluent + cavity diluent number, rotational and trans- - + moles combustor products lational temperature ratio moles excess fluorine as F2 (see Reference 16) P = laser output power m F = atomic fluorine flow rate In this simplified fomlation, the cavity mixing is idealized and is characterized by a single, average stream velocity and the spread angle a. Deactivation of the excited state species DF* is assumed to be dominated by a single collision process involving, in this case, other DF molemles. The "trip" jets are not modeled. % = Laser cavity mixture ratio Numerous correlations of experimental data CD21 have been examined based upon the above mixing - Moles cavity fuel = model. The correlation which has provided the (4) best fit to existing data and is in current use Moles fluorine as F2 [F2 + 4 @')I is based on the following modifications of the original formulation: TI = Adiabatic combustor operating temperature 1) The mixing is represented by the entrain- Subscripts : c = combustor ment of D2 into the fluorine stream with a characteristic transverse velocity a UD L = laser cavity and a mixing length characterized by 2 the fluorine nozzle width L. 2) A new deactivation parameter, A, is Combustor Fuels C2H2 8 C2H4 added to allow for products from the Combus tor Oxidizer 'F2 6 NF3 combustor process which effectively de- activate the excited state DF. Combustor Adiabatic 17000F to 22000K Temperature, TI 3) The atomic fluorine molar flowrate is Combus tor Diluent 9 to 21 substituted for fluorine concentration ,in Ratio $, Equation 1 using the identity Total Laser Diluent 28 to 50 Ratio Laser Cavity Mixture 3 to 6 where h = fluorine nozzle height Ratio RL n = total number of fluorine nozzles Variations in the cavity injector configu- rations included : and the remaining symbols have been defined. Nozzle spacing .I21 inch to .295 inch 4) A final revision to the original formu- Nozzle area ratio A/@, lation allows for the incorporation of a F nozzle 15 to 25 rotational temperature term (q)B to D2 nozzle 10 to 20 account for the effects of v&i&ions in cavity flow static temperature on the partial inversion lasing process. Incorporating the above modifications and substitution of identities, the equation takes the following form:

where K1 = proportionality constant - n = number of fluorine nozzles h = nozzle height fluorine stream velocity UF = vD2 = deuterium stream velocity NF = fluorine molar flow rate A = experimentally determined constant T = average mixed stream temperature prior to heat release in cavity B = experimentally determined constant Values of the constants have been determined to be A = B = .5, K1 = 4.49 x 10-l1 joule/sec/an3 (gm mol/wt) . The constant C1, experimentally determined to be 314.9 wattjgmlsec, is introduced in order that a straight line fit of the data over the expected operating range may be utilized. Equation 7 suggests that chemical laser cavity injectors should be designed with extremely fine scale nozzles (n per unit length should be maxi- mized), the stream velocities UF and UD~should be Figure 7. Chemical Lasing Correlation Analysis maximized, the concentration of combustor produced HF should be minimized and the cavity static temp- erature should be decreased but not below the point Variations in pertinent parameters of the where chemical reaction can be sustained. correlation equation were: Number of F nozzles/inch 6.41 to 8.26 Figure 7 shows the results of a regression of array length analysis of approximately 80 chemical laser experi- ments. These data were acquired from three chemi- Fluorine Nozzle 1.77 x 10' to 2.58 cal las.er cavity injector configurations, all Velocity UF x 105 cm/sec basically of the type shown in figure 2. The Deuterium Nozzle 1.71 x 10' to 2.47' correlation data were acquired derthe following x 105 dsec limits of operating conditions: Velocity. U92 Ratio Nw/NF .10 to 1.15 JOURNAL DE PHYSIQUE

tially constant performance with the increased jet Average stream tempera- 106 OK to 172 OK ture before reaction, T penetration and mixing countering the "nl' effect in equation 7. Increased understanding of trip These cavity injectors were tested over a wide jets will allow increased nozzle size. range of flow conditions and the data used for the generation of the performance curves shown Ultimately chemical laser cavity injectors will by Figure 6. All data shown in Figure 6 were be regeneratively cooled as shown by figure 2B. The acquired with a D2 plenum stagnation temperature figure 2B cavity injector converts waste heat energy of 600°~. The validity of the UD~term in into increased D2 plenum stagnation temperature by equation 7 was checked by operating the cavity utilizing the cavity Hen2 mixture to cool the injector at two values of the D2 plenum stagnation cavity injector nozzles. In this configuration, ,the temperature. This allows for a change of UD~and nozzle walls will operate at %1000oK as opposed to T only, all other parameters remaining essentially the 500~~normally found in nozzles such as those unchanged. The fluorine and deuterium nozzles of Figure 2.4. This effect has been tested by sub- were run at matched and unmatched pressure con- stitution of N2 coolant for H20 in the conventional ditions with no apparent effect on performance. nozzles. Figure 9 shows the effect of hot wall The resultant values of UD and T are given below. nozzle operation. The increased boundary layer 2 temperature and viscous effects appear to reduce power by anamountsmall in relation to the improve- ToDly OK T, OK UD9, meters/sec ments in performance attendant to the UD~effect of Figure 8.

Figure 8 illustrates the resulting laser power measurements for the two test cases. The per- formance difference measured is 17%. The perfor- mance improvement calculated by equation 7 is 36%. The simplified model does properly predict the trend but with limited accuracy. Insufficient data currently exist to upgrade the experimental correlation to more accurately model the UD effect. 2

8 I I I J 4 5 6 LASING ZONE UNGIH (Of)

Figure 9. Effect of Elevated Nozzle Wall Temperature on Laser Performance Chemical laser cavity designs must be compati- ble with the rapid heat release in the supersonic flow stream. The top and bottom surfaces of the lasing cavity are gas dynamically contoured to con- fine the flow to prevent recirculation of ground state DF and to turn the flow into the supersonic converging section of a diffuser as shown in Figure 1. Configuration 2 was the contoured cavity used 6 I I I I 4 5 6 to collect the data presented in Figure 6. Since ZCNE the flow and heat is being released by chemical pro- LASING mm ((XI cesses, the static pressure rises from 13 to 24 torr from 0.5 to 5 cm downstream respectively. The Mach Figure 8. Effect of Increased D2 Nozzle Plenum number decreases from 4.5 to near 2. The mean Temperature velocity is 2000 meters/sec at the exit of the lasing cavity. The temperature increase3 from a Using equation 7 to predict the effect of mixture temperature of near 250°K to 530 K at cavity nozzle size or herof nozzles per unit length exit due to the heat release From the chemistry. from the largest nozzle tested (.295 inch) to the The average mlecular weight of the gas leaving the smallest nozzle tested C.121) yields an estimated cavity is 6.4 and specific heat ratio is 1.58. performance change of 10%. Experimental data over the range of nozzle spacing reveals little The Mach number 2 flow enters the supersonic measurable difference in performance . diffuser as sham in Figure 1. The converging section decreases the Mach number to 1.4 near the The theory is not accounting for the "trip" throat where a system of oblique and normal shocks jet effect which is a dominate effect. Increasing produce subsonic flow. The subsonic flow diffuses nozzle spacing to 0.295 in has resulted in essen- to the local static pressure at the diffuser exit. VARIABLE CGNTOUR LASER CAVITY efficient laser hence the velocity is relatively HFCLT ICL-XI) TEST GEOMETRIES fixed. Pressure recovery can be varied from 100 to 300 torr primarily by increasing the Ih/A which 1 2 increases the pressure correspondingly everywhere + I in the laser from combustor to diffuser exit. This higher lasing cavity pressure results in decreased laser efficiency as shown in Figure 6. The pressure CL-XI recovery in chemical lasers can be predicted by NOZZL Figure 11 which has been correlated to at leas* 10 BANK different lasers and many expyj--, some of which are shown in Figure 11.

The 100 to 300 torr gas at diffuser exit is then pumped to atmospheric pressure by adding momentum to the laser flow with a jet pwsuch as in The momentum in CL - XI shown schematically Figure 1. the ejector jet is generated by expanding high hN - 1.375 in. temperature hydrazine products from a gas generator WN - 4.000 in. through a high Mach number nozzle. Figure 12 shows AN - 6.500 la2 data from several ejectors. Assuming a diffuser

Figure 10. Cantoured Lasing Cavities and qersonic Diffusen that have been used on Chemical Lasers

Typical chemical laser supersonic diffusers have length to Yw (height) ratios of 12. The width of the diffuser is expanding to account for thick bound- ary layers & boundary layer enerizers are required. 0 REF 17 The pressure recovery of a chemical laser is a function of the momentum per unit area at the nozzle a REF 18 bank exit plane. For a given laser configuration, 0 REF 19 the mean velocity of the flow field is a function of the specific heat ratio, the mean total tempera- 0 REF 19 ture, Tte, and molecular weight, W, at the cavity - entrance. The mass rate of flow per unit area of nozzle bank, fi/A, is increased by raising the com- bustor pressure. The static temperature in the lasing cavity and the total temperature in the com- MASS RATIO bustor can only be varied over small ranges for an

ANALYTICAL Figure 12. Ejector Performance

recovered pres.sure of 230 torr the required fjector pressure ratio to recover to an atmosphere is 3.3. 0 GLAD CALCULATION Figure 12 gives a required ejector mass ratio of 3.2 for reference 18 data. Hence the ejector requires 3.2 times the mass rate of flow of the laser effluent. For this example the laser specific paver from Figure 6 is 49 kw/lb/sec but the total system specific power including the ejector mass flow rate is 11.7 kw/lb/sec. Concluding Remarks EXPERIMENTS A CLVLll(0.8P )1IN.x8IN. DF lasers are emerging as a strong contender t2 for applications requiring high energy radiation CL XI (WITH 1-318 IN. X 4 IN. DIFFUSER) with good focusing and propagation characteristics. The device offers highperformance, goo6 beam quality and s-licity when cqared to electri- cally powered devices. Currently, predictive capabilities for performance, pressure recovery, propagation, beam quality, and scaling are reasonably well developed. (20)

Figure 11. Chemical Laser Pressure kcawry Metion Gmpared with Matand Data JOURNAL DE PHYSIQUE

11. Bullock, D.L., and Lipkis, R., 'Unstable References Resonators for Chemical Lasers", Air Force ;Yeapons Laboratory, TR 74-201, July 1975. 1. Kasper, J.V.V. and Pimentel, C.G. , "HC1 Chemical Laser", Phys, Rev. Letters, 14, 352 (1965) . 12. Hook, D.L., Behrens, H.W., et al, "DF Laser Technology Studies" Final Report, AFWL, to 2. Dzhidzhoev, M.S.; Platonenko, V.T.; be published. Khokhlov, R.V., Sov. Phys. Uspekhi, 2, 247 (1970). 13. fqProposalfor Aerodynamic Reactive Flow 3. Basov, N.G., Igoshin, V. I., Markin, J. I., Studies of H /F2 Laser-II", J.E. Broadwell, TKV Oraevskii, A.N., Kvantovaja Electronika, 2, 3. Report ~~209~7.001,22 May 1972. 4. Dawson, P.H. , and Kinball, G.H. , Chemical 14. "Effect of Mixing Rate on HP Chemical Laser Performance", H. Mirels, R. Hofland, and W. S. King, AIAA Journal 2 (2) 156, February 1973.

5. Kompa, K.L., Chemical Lasers, Topics in 15. "Simplified Model of CW Diffusion Type Current Chemistry, 37,- Chemical Laser", K. Mirels, R. Hofland, and W.S. King, AIAA Journal 2 (2) 156, February 1973. 6. Warren, W. R. , 7'Chemical Lasers ," Astronautics and Aeronautics, Vol. 13, No. 4, 36 16. "Closed Form Solution to Rate Equations (1975). for an F + H2 Laser Oscillator", G. Emanuel and J.S. ~Vhigtier,Applied Optics 11, 2047, 7. Cohen, N., "A Review of Rate Coefficients September, 1972. for Reactions in the D -F Chemical Laser System," Aerospace Cop. ~~0074f4550)-5, 1974. 17. Knowles, P.J., Reiner, R.J., Heckert, 8. Spencer, D.J., Denault, G.D., and B.J., .and Dailey, C.L., "Feasibility Study of High Takimoto, B.H. , TtAtmosphericGas Absorption at Energ)lr Ejector Systems", Aerospace Research Labo- DF Laser Irlavelengths," Aerospace Corp. TR-0073 ratories, ARL-TR-75-0015, May 1975. (3240-10)-9, 1973. 18. Teper, R. I., "Chemical Laser Diffuser/ 9. Chodzko, R.A., Spencer, D.J. and Mirels, Ejector Technology", Rocketdyne, to be published. H., 7tZero-Power Gain Measurements in a CW-IiF Laser Ushg a Pulsed-Probe Laser," Aerospace Corp. 19. Kepler, C.E., Zumpano, F.R., Landerman, TRO074(4534)-2, 1973. DF gain measurements by A.M., Biancard, F.R., Brooks, C.S., and Russel, S., private communication. "Pressure Recovery/Scrubber Systems for Chemical Lasers", United Aircraft Research Laboratories, 10. (a) Chodzko, R.A., and Chester, A.N., TR-R75-911976-8-2, Vol. 11, March 1975. "Optical Aspects of Chemical Lasers", Aerospace - 20. This paper is current technology and is to be published. an updated version of Wilson, L.E.; Hook, D.L., "Deuterium Fluoride CllT Chemical Lasers", AIAA Paper (b) Wisner, G.R., Palma, G. , and Foster, M., "Laser Beam Quality Study Report", United No, 76-344 MAA 9th Fluid & Plasma Dynamics Con- Aircraft Research Laboratories, UARL M911239-23, ference. Reprinted in part by permission of AIAA. Sept. 1973.