NASA TECHNICAL MEMORANDUM NASA TM X-2589

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. SEPTEMBER 1972

1. Report No.

NASA TM X-2589

2. Government Accession No.

3. Recipient’s Catalog No.

4. Title and Subtitle

CESIUM-DIODE PERFORMANCES FROM THE 1963-TO-1971 THERMIONIC CONVERSION SPECIALIST CONFERENCES

5. Report Date September 1972

6. Performing Organization Code

7. Author(s)

James F. Morris

8. Performing Organization Report No.

E-6989

9. Performing Organization Name and Address

Lewis Research Center
National Aeronautics and Space Administration
Cleveland, Ohio 44135

10. Work Unit No.

503-25

11. Contract or Grant No.

12. Sponsoring Agency Name and Address National Aeronautics and Space Administration Washington, D.C. 20546

13. Type of Report and Period Covered Technical Memorandum

14. Sponsoring Agency Code

15. Supplementary Notes

16. Abstract

This report indexes and summarizes papers containing cesium-diode results from the proceedings of the 1963-to-1971 Thermionic Conversion Specialist Conferences. Lists of converter materials, geometries, conditions, outputs, and lifetimes accompany the references. Simple chemical designations for emitters, collectors, and additives direct the reader to appropriate selections.

17. Key Words (Suggested by Author(s))

Cesium diode performance
Survey
Nuclear engineering
Nuclear thermionics

18. Distribution Statement Unclassified - unlimited

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

52

22. Price

$3.00

*For sale by the National Technical Information Service, Springfield, Virginia 22151

This report indexes and summarizes papers containing cesium-diode results from the proceedings of the 1963-to-1971 Thermionic Conversion Specialist Conferences. Lists of converter materials, geometries, conditions, outputs, and lifetimes accompany the references. Simple chemical designations for emitters, collectors, and additives direct the reader to appropriate selections.

Most cesium-diode performance studies reach the Thermionic Conversion Specialist Conferences eventually. If the work fails to appear in the proceedings originally, it often enters in subsequent comparisons. And the accompanying references generally include expansive current, voltage data in agency, contractor, or company publications. So the Thermionic Conversion Specialist Conferences provide extensive cesium-diode output information. To increase the accessibility of this technology the present report indexes and summarizes such contributions for the past decade.

Beginning with the 1963 conference an annotated, chronological tabulation indicates 129 papers containing thermionic-converter results. Lists of diode materials, geometries, conditions, outputs, and lifetimes, if they were found, accompany the references. A simple chemical index for emitters, collectors, and additives directs the reader to appropriate selections. Because these chemical labels are guides not analyses, they lack the complexity of additive product permutations; they are easily recognized elemental or molecular forms. But they adequately identify the materials involved.

With a set of the proceedings for the Thermionic Conversion Specialist Conferences and the present report, comprehensive literature surveys on cesium-diode performances are readily available.

Cavity 53

Iridium (Ir) 10, 17, 18

Molybdenum (Mo) 5, 6, 7, 9, 10, 12, 14, 20, 21, 34, 38, 39, 47, 82, 84, 89, 92, 98, 100 (single-crystal 110 (1-xtal 110)), 120, 127,

Molybdenum-based alloy 98

Rhenium (Re) 3, 4, 12, 14, 15, 16, 19, 21, 22, 23, 27, 31 (electroetched), 40, 41, 42, 44, 56 (etched), 57 (etched), 58 (electro-etched), 59, 64, 65, 66, 67, 68, 69, 73, 74, 76, 79 (1-xtal 0001), 82, 87, 91, 95, 101, 103, 107 (etched), 114 (etched or 1-xtal 0001), 115 (chemically vapor-deposited (CVD)), 122 (etched), 125 (etched), 126

Ruthenium (Ru) 11, 45

Tantalum (Ta) 4, 5, 42, 46, 53, 66, 82

Tungsten (W) 2, 4, 8, 13, 14, 21, 22, 24, 25, 26, 28, 29, 30 (Cl¯CVD,110), 33, 37, 43 (Cl¯CVD), 48 (F¯CVD (100) etched to 110), 49 (Cl¯CVD), 50 (Cl¯CVD, F¯CVD), 55 (VD), 60, 61, 62 (1-xtal 110), 63, 70 (Cl¯CVD, F¯CVD), 71 (Cl¯CVD), 72 (F¯CVD, four surface preparations), 80 (F¯CVD etched to 110), 81 (1-xtal 110), 82 (several orientations and surface preparations), 83 (1-xtal 110), 84 (F¯CVD), 85 (F¯CVD), 86 (Cl¯CVD), 88 (F¯CVD), 90 (F¯CVD), 90 (F¯CVD, four surface preparations), 93 (SIMCON), 94 (Cl¯CVD), 96 (CVD), 97 (physically vapor-deposited (PVD)), 102 (1-xtal 110, Cl¯CVD, F¯CVD), 104 (1-xtal 110, Cl¯CVD, F¯CVD), 105 (1-xtal 110, Cl¯CVD, F¯CVD), 106 (F¯CVD etched to 110, Cl¯CVD, F¯CVD), 108 (Cl¯CVD), 109 (Cl¯CVD, F¯CVD), 110, 111, 112, 113 (F¯CVD), 116 (CVD), 117 (Cl¯CVD), 118 (F¯CVD), 121 (Cl¯ vapor deposited by thermal decomposition (TVD)), 122 (PVD, Cl¯CVD), 123 (Cl¯CVD), 124 (PVD, Cl¯CVD, F¯CVD), 126, 128 (CVD), 129 (Cl¯CVD, SIMCON)

Tungsten-based mixture 98 ("tungsten-based alloy," "tungsten, rhenium"), 32 (W, 20 percent Re), 78 (W, 25 percent Re), 82 (W, 25 percent Re), 1 (with a small amount of Th), 119 (W, 2 percent ThO₂)

Grooved 36

Inconel 8

Molybdenum (Mo) 3, 4, 5, 11, 12, 13, 15, 19, 22, 24, 27, 30, 31, 33, 34, 36 (with and without grooves), 38, 39, 40, 41, 42, 44, 45, 49, 50, 51, 53, 56, 57 (VD), 59, 62, 63, 64, 69, 71, 74, 76, 82, 84, 89, 91, 92, 93 (SIMCON), 94, 95, 96, 99, 100 (1-xtal 110), 104, 105 (polycrystal (polyxtal) or PVD (110)), 108 (PVD), 110, 113, 114, 116, 118, 120, 122, 123 (PVD), 124 (PVD), 125 (PVD), 128

Nickel (Ni) 2, 7, 9, 10, 14, 16, 20, 21, 25, 28, 29, 33, 37, 43, 46, 51, 60, 82, 121

Niobium (Nb) 6, 21, 29, 45, 47, 48, 50, 56, 58, 66, 67, 68, 69, 70, 72, 79, 80, 81, 82, 85, 86, 90, 97, 98, 99, 101, 102, 103, 104, 105, 106, 107, 109, 112, 117, 121, 122, 123, 126, 129

Niobium-based mixtures 45(Nb, 0), 55 (Nb, 1 percent Zr), 84 (Nb, 1 percent Zr), 88 (Nb, 1 percent Zr), 115 (Nb, 1 percent Zr), 127 (Nb, 1 percent Zr)

Palladium (Pd) 58

Rhenium (Re) 40, 45, 58, 65, 82, 87 (Cl¯CVD), 91

Ruthenium (Ru) 11, 45

Silver (Ag) 23

Stainless steel 1, 17, 18 (304)

Tantalum (Ta) 4, 5, 26, 111

Tungsten (W) 25 (from emitter on Ni collector), 61, 83 (1-xtal 110), 121, 123 (1-xtal 110, polycrystalline)

Tungsten-based mixtures 78 (W, 25 percent Re), 82 (W + WO₂ on Nb collector)

Argon (Ar) 35, 46, 75

Barium (Ba) 13, 111, 120

Carbon (C) (possible diffusion into diode from UC) 3, 6, 117

Cesium fluoride (CsF) 12, 24, 34

Cesium oxide (Cs₂O) 44, 52

Fluorine (F or F₂) 12, 24, 34

Hydrogen (H or H₂) 2, 14

Iodine (I or I₂) 46

Krypton (Kr) 46, 54

Nitrogen (N or N₂) (possible diffusion into diode from UN) 126

Oxygen (O or O₂) 7 (possible diffusion into diode from UO₂), 8 (UO₂), 9 (UO₂), 23, 28 (UO₂), 44, 45 (in Nb), 47 (UO₂), 52, 55 (UO₂), 88 (UO₂), 8 (UO₂), 104, 105, 112 (UO₂), 114, 117 (UO₂), 119 (from ThO₂ in emitter), 124, 125 (UO₂)

Thorium (Th) (from the emitter composition) 1 (in W), 119 (W, 2 percent ThO₂)

Uranium (U) (possible diffusion into diodes from fuel) 3, 6, 7, 8, 9, 28, 47, 55, 88, 89, 112, 117, 125, 126

Xenon (Xe) 17, 18, 46, 54, 75

Emitter (E), Collector (C), Combination Reference

Iridium (E)

Stainless steel (C) 17, 18

Molybdenum (E)

Molybdenum (C) 5, 12, 34, 38, 39, 82, 89, 92, 100, 120

Niobium, 1 percent Zirconium (C) 127

Niobium (C) 6, 47, 98

Nickel (C) 7, 9, 10, 14, 20

Emitter (E), Collector (C), Reference Combination

Molybdenum-based alloy (E)

Niobium (C) 98

Rhenium (E)

Molybdenum (C) 3, 4, 12, 15, 19, 22, 27, 31, 40, 41, 42, 44, 56, 57, 59, 64, 69, 74, 76, 82, 91, 95, 114, 122, 125

Nickel (C) 14, 16, 82

Niobium (C) 21, 56, 58, 66, 67, 68, 69, 79, 82, 101, 103, 107, 122, 126

Niobium, 1 percent Zirconium 115

Palladium (C) 58

Rhenium (C) 40, 58, 65, 82, 87, 91

Silver (C) 23

Tantalum (C) 4

Ruthenium (E)

Molybdenum (C) 11, 45

Niobium (C) 45

Niobium with oxygen (C) 45

Rhenium (C) 45

Ruthenium (C) 11, 45

Tantalum (E)

Molybdenum (C) 4, 5, 42

Nickel (C) 46

Niobium (C) 66, 82

Tantalum (C) 4, 5

Tungsten (E)

Inconel (C) 8

Molybdenum (C) 13, 22, 24, 30, 33, 49, 50, 62, 63, 71, 82, 84, 93, 94, 96, 104, 105, 108, 110, 113, 116, 118, 123, 124, 128

Nickel (C) 2, 14, 21, 25, 28, 29, 33, 37, 43, 60, 82, 121

Niobium (C) 21, 29, 48, 50, 70, 72, 80, 81, 82, 85, 86, 90, 97, 102, 104, 105, 106, 109, 112, 117, 121, 122, 123, 126, 129

Niobium, 1 percent Zirconium 55, 84, 88

Tantalum (C) 4, 26, 111

Emitter (E), Collector (C), Reference Combination

Tungsten (C) 25, 61, 83, 121, 123

Tungsten and tungsten oxide on a niobium collector (C) 82

"Tungsten-based alloy" (E)

Niobium (C) 98

Tungsten, rhenium alloys (E)

Nickel (C) 82

Niobium (C) 98

Tungsten, 25 percent 78 Rhenium (C)

Tungsten with a small amount of thorium (E)

Stainless steel (C) 1

1. Houston, John M.: Measurements of Emitter Heat Balance in a Cesium Thermionic Converter, pp. 214-223.
Emitter W with a small amount of Th; T_E = 1900 to 2200 K
Collector stainless steel; T_C = 583 to 783 K and optimum
Cesium gap 1 mm; T_R = 424 to 573 K
Additive Th
Geometry cylindrical, 1.52-cm diameter, 13.3 cm²

Output 0.4 to 0.8 W/cm² with 1.2 to 2.4 percent efficiency at 1900 K; 6 to 9 W/cm² with 8.8 to 12 percent efficiency at 2200 K

2. Rump, B. S.; Bryant, J. F.; and Gehman, B. L.: Study of the Influence of Additives on Work Function and Power Output of Thermionic Cells, pp. 236-239.
Emitter W; T_E = 1000 to 2300 K
Collector Ni; T_C = 400 to 1000 K and optimum
Cesium gap T_R = 100º and 200º C
Additive H₂
Geometry filamentary
Output power for Cs alone above that for Cs + H₂ with T_R = 100º C; for T_R = 200º C power for Cs + H₂ above that for Cs alone at T_E < 1900 K; for T_R = 200º C power for Cs + H₂ at 1500 K equal to that for Cs alone at 2100 K; power range 10^-6 to 10^-1 W/cm²

3. Howard, Robert C.; Keller, D. L.; and Smith, C. K.: Converter Performance Test of a Rhenium Emitter in Contact with a Carbide Fuel, pp. 287-294.
Emitter Re (UC backed); T_E = 1550º C (129 hr), 1600º C (72 hr)
Collector Mo; T_C = 603º to 617º C
Additive U and C possible
Geometry plane
Output 5 W/cm² (0.5 V, 1550º C), more than 8 W/cm2 (0.5 V, 1600º C), no degradation of performance

Lifetime 201 hr; thermal bond separation in fuel, emitter sandwich

4. Merra, S. G.; and Weinstein, J. H.: Recent Progress in the Development of Solar Thermionic Converters, pp. 295-304.
Emitter Re, Ta, or W; T_E = 1980 to 2050 K
Collector Mo or Ta; radiation cooled
Cesium gap 0.051 to 0.064 mm; TR optimized
Geometry plane solar diodes
Output as shown in the following table (from ref. 4):

Lifetime over 2000 hr

5. Rouklove, P.: Results of Laboratory Tests of Set Thermionic Converters and Generators, pp. 305-313.
Emitter Mo (C), Ta (A, B, D); T_E = 1677º C (D) and 1700º C (A, B, C)
Collector Mo (B, C, D), Ta (A); radiation cooled
Cesium gap 0.051 mm (A), 0.025 to 0.203 mm (B), 0.127 mm (B); T_R optimized
Geometry plane solar diodes
Output 11 to 18 W/cm² to 0.6 V with 8.5 to 9 percent efficiency (A), 5 to 8.5 W/cm² maximums for 0.076 to 0.025 mm at 0.6 V with 5.4 percent efficiency (B), 9.3 W/cm² maximum with 7.4 percent efficiency (B), 7.0 to 8.5 W/cm² (C), 10 to 13 W/cm² (D)

Lifetime some in excess of 2000 hr

6. Busse, C. A.; Caron, R.; and Salmi, Ernest W.: In-Pile Test of a Thermionic Converter, pp. 314-322.
Emitter Mo ((UZr)C backed)
Collector Nb
Cesium gap 0.5 mm
Additive U and C (through the emitter and through a hole in the emitter)
Geometry cylindric with emitter cavity, diode gap, and Cs reservoir interconnected
Output 0.22 W/cm² at 1 MW reactor power (T_R = 1770 C)
Lifetime cesium heater failed in initial checkouts and allowed no high-power runs in the reactor

7. Block, Fred G.; Eastman, G. Y.; and Harbaugh, Willis E.: The Design, Development, and In-Pile Testing of a Nuclear-Fueled Thermionic Energy Converter, pp. 323-331.
Emitter Mo (UO₂ backed); T_E = 1200º to 1700º C with 1350º C design optimum
Collector Ni; T_C optimums 525º to 825º C (for 1200º to 1700º C); 570º C for T_E = 1350º C
Cesium gap 0.838 to 0.076 mm optimums (for 1200º to 1700º C), 0.279 mm for T_E = 1350º C; T_R optimums 270º to 380º C (for 1200º to 1700º C), 310º C for T_E = 1350º C
Additive U and O possible
Geometry cylindric; 60 cm²
Output 1.3 to 15 W/cm² (for 1200º to 1700º C), 3.2 W/cm² at T_E = 1350 C; 11 percent "typical efficiency"; in-pile 2.25 W/cm² at 9 percent efficiency (see ref. 9)
Lifetime 2600 hr for one and 1400 hr at 3 W/cm² for another out of pile, both continuing; in-pile performance plummeted after 300 hr

8. Beckjord, Eric S.: Test Results on an In-Pile Nuclear Thermionic Converter, pp. 332-340.
Emitter W (UO₂ backed); T_E = 1700º, 1720º, 1800º C
Collector Inconel; T_C = 650º to 700º C
Cesium gap 0.254 mm; T_R = 335º to 345º C for power maximums
Additive U and O possible
Geometry cylindric; 1.17-cm diameter, 8.6 cm²

Output 4 W/cm² at 0.6 V and 1700º C, 5 W/cm² at 0.64 V and 1720º C, 6 W/cm² at 0.78 V and 1800º C; 10.5 percent efficiency at peak 6.2 W/cm² and 1800º C
Lifetime 224 hr in testing reactor before Cu pinchoff failed

9. Eastman, G. Y.; Basiulis, A.; and Harbaugh, W. E.: Thermionic Converter Operation in Multiple Connection, pp. 348-355.
Emitter Mo (UO₂ back); T_E = 1300º to 1500º C
Collector Ni; T_C optimized
Cesium gap optimized widths and T_R’s
Geometry cylindric, 60 cm²

Output 1 to 4 W/cm² at 8 to 12 percent efficiencies (see ref. 7); complete performance map

10. Martini, W. R.: Internal Flame-Heated Thermionic Converters, pp. 356-361.
Emitter Ir at 1430º C, Mo at 1400º C
Collector Ni
Cesium gap 0.762 mm with T_R = 252º C for Ir, 0.208 mm with T_R = 315º C for Mo
Geometry plane; 2.54-cm diameter
Output projected from RCA tube 1195A data, 5.5 W/cm² for Ir, 4.25 W/cm² for Mo

11. Kennedy, A. J.; and Trimmer, D. S.: The Performance of Ruthenium as an Electrode in a Thermionic Converter, pp. 63-70.
Emitter two of hot-pressed Ru, one of plasma-sprayed Ru; T_E = 1500 to 1900 K
Collector one of arc-cast Mo, two of plasma-sprayed Ru; T_C = 698 to 1031 K
Cesium gap 0.102 to 0.762 mm; T_R = 535 to 589 K
Geometry plane
Output 8 W/cm₂ for 0.254 mm and T_E = 1800 K; Ru gives higher power densities than Re and Ir produce for gaps wider than 0.254 mm

12. Jester, Alfred A.: The Influence of a Cesium Fluoride Additive on the Power Output of Cesium Diodes with Molybdenum and Rhenium Emitters, pp. 93-99.
Emitter (1) Mo or (2) Re; T_E = 1800 K (A), 1900 K (B), 2000 K (C)
Collector Mo; T_C = 750 or 800 K or optimum
Cesium gap 0.05 to 0.4 mm; T_R = 531 to 609 K or optimum
Additive CsF at T_CsF = 800 K
Geometry plane
Output for Cs with CsF: emitter (lA) 12 W/cm²at 0.35 V; (1B) 20 W/cm² at 0.5 V; (1C) 24 W/cm² at 0.6 V; (2A) 16 W/cm²at 0.4 V; (2B) 20 W/cm² at 0.65 V; (2C) 28 W/cm² at 0.7 V; at identical voltages Cs with CsF gave more power, allowed lower Cs pressure, or permitted greater gap widths; good performance maps

13. Psarouthakis, John: Thermionic Energy Converter with Barium and Cesium Vapors, pp. 100-109.
Emitter W; T_E = 1700, 1800, 1900, or 2000 K
Collector Mo; T_C's within 250 C above T_Ba’s
Cesium gap 0.025 to 1.016 mm; T_R = 425 to 647 K
Additive Ba; T_Ba = 1000 to 1200 K
Geometry plane
Output 8.5 W/cm₂ at T_E = 2000 K, T_C = 1100 K, T_Ba = 1080 K, T_Cs = 470 K with a "fundamental conversion efficiency" of 27 percent; output dropped from 8.5 to 8.2 W/cm²as the gap widened from 0.051 to 1.016 mm

14. Hall, W. B.; and Shoemaker, R. E.: Control of Gas Impurities in a Thermionic Converter, pp. 110-114.
Emitter Mo, Re, or "special" W; T_E = 1250º to 1550º C
Collector Ni; optimum T_C’s
Cesium gap optimum width; optimum T_R’s
Additive H₂
Geometry plane; 11.7 cm²
Output at 1550º C, 9.5 W/cm² (Mo), 12 W/cm² (Re), 17 W/cm²(W); H₂ from 10^-6 to 10^-3 torr did not affect W or Re; it dropped Mo performance 15 percent and lowered the output of a contaminated W emitter over 40 percent.

15. Shavit, Arthur; and Hatsopoulos, George N.: Operation of a Thermionic Converter for the Ion-Rich Unignited Mode, pp. 206-213.
Emitter Re; T_E = 1520 to 1900 K
Collector Mo
Cesium map 0.008 to 0.254 mm; T_R = 480 to 539 K
Geometry plane, guarded
Output very low (unignited mode)

Report on the Thermionic Conversion Specialist Conference. IEEE, 1965.

21. Wilson, V. C.: Rapporteur Paper on "Converter Performance" from The International Conference on Thermionic Electrical Power Generation, London, England, pp. 258-265.
Emitter (1) W, (2) Mo, (3) W, (4) Re, (5) W; T_E = (1) 2263 K, (2) 1973 K, (3) 1900 and 2000 K, (4) 1900 K, (5) 2100 K
Collector (1) Ni, (2) unknown, (3) Nb, (4) Nb, (5) Nb; T_C = 898 to 1053 K for (1) Cesium gap (1) 0.051, (2) 0.3, (3) 0.16, (4) 0.25, (5) 0.25 mm; T_R = 593 to 693 K for (1)
Geometry (1) plane, the rest cylindric
Output (1) over 75 W/cm², (2) 4.2 W/cm², (3) 5 to 8.4 W/cm², (4) 3.75 W/cm², (5) 10 W/cm²; efficiency of (2) 8 percent, (3) 11 percent; performance map for (1)

22. van Someren, L.; Lieb, D.; and Kitrilakis, S. S.: Evaluation of Thermionic Emitter Surfaces, pp. 266-275.
Emitter Re (four surface preparations), W; T_E = 1605 to 1975 K for Re, 1630 to 1950 for W
Collector Mo; T_C = optimum
Cesium gap optimum; T_R = optimum
Geometry plane; 3-cm² emitter, 2-cm² collector, guard
Output 22 W/cm²for Re and 14 for W at T_E = 1850 K; 40 W/cm²for Re at 1975 K; fully optimized performance plots

23. Levine, J. D.; Harbaugh, W. E.; and Shoemaker, R. E.: Oxygen as a Controllable, Reversible, and Beneficial Additive in the Cesium Converter, pp. 276-280.
Emitter Re; T_E = 1350º C
Collector Ag; T_C = 350º to 550º C
Cesium gap 0.356 mm; T_R = 285º and 290º C
Additive O₂ introduced through Ag membrane on collector
Geometry plane
Output 4.6 W/cm² with 11.6 percent efficiency at 0.2 V, T_C = 400º C, and T_R = 285º C; performance plots

24. Lieb, D.: Performance of Tungsten-Emitter Thermionic Converter in the Presence of Cesium Fluoride Additive, pp. 281-288.
Emitter W; T_E = 1630 to 1950 K
Collector Mo; T_C = 813 to 943 K
Cesium gap 0.025 to 0.762 mm; T_R = 480 to 645 K
Additive CsF; T_CsF = 378 to 770 K
Geometry plane, guarded
Output 40W/cm² at 0.58 V for Cs + CsF, T_E = 1870 K, T_C =893 to 943 K, T_CsF = 623 K, T_R = 538 to 609 K, d = 0.127 mm; 9W/cm2 at 0.58 V for Cs alone, T_E = 1850 K, T_C = 862 K, T_R = 562 to 635 K, d = 0.153 mm; good performance plots

25. Lawrence, J.; and Perdew, J. P.: Effect on Thermionic Converter Performance of Emitter Material Evaporated on a Low Work Function Collector, pp. 289-296.
Emitter W; T_E = 1633 to 2183 K
Collector Ni or W (from emitter) on Ni; T_C = 863 to 973 K
Cesium gap 0.051 mm; T_R = 553 to 663 K
Geometry plane, guarded
Output at 100 A/cm², 78 W/cm² (2183 K), 65 W/cm² (2074 K), 47 W/cm² (1963 K), and 35 W/cm2 (1855 K) for Ni and 20 W/cm² (1855 K) for W on Ni; subsequent contamination nearly regenerated the initial performance; good I, V curves

26. Blue, E.; and Ingold, J. H.: The Effect of High Collector Temperature on the Power Output and Efficiency of a Thermionic Converter: Experimental, pp. 297-305.
Emitter W; T_E = 2150 or 2225 K
Collector Ta; T_C = 1355 to 1675 K
Cesium gap 0.051 to 0.432 mm; T_R = 633 to 693 K and optimum
Geometry plane, guarded
Output at T_E = 2225 K, T_C = 1500 K, T_Cs = 673 K, d = 0.135 mm, 27.5 W/cm2 maximum for 0.45 V and 9 percent efficiency and 10.5 percent maximum efficiency; extensive performance plots show effects of high collector temperatures

27. Kitrilakis, S.; and Brosens, P.: Experimental Correlation of Electron Emission Cooling and Optimum Collector Temperature, pp. 316-324.
Emitter Re; T_E = 1680 to 2000 K
Collector Mo; T_C = 873 to 1073 K
Cesium gap 0.013 to 0.508 mm; T_R = 543 to 630 K
Geometry plane, guarded
Output 5.3 W/cm² at 0.38 V, T_E = 1740 K, T_C = 1053 K, T_R = 588 K, d = 0.102 mm; I, V plots; an attempt to correlate optimum collector temperatures

Conference Record of the Thermionic Conversion Specialist Conference. IEEE, 1966.

28. Gilliland, D. L.: Performance and Life Test of a Cylindrical Thermionic Converter, pp. 1-5.
Emitter W (UO₂ backed); T_E = 1500º to 1830º C
Collector Ni; T_C = 700º C
Cesium gap 0.127 mm; T_R = 330º to 370º C
Additive U and O possible
Geometry cylindric; 1-cm diameter, 8.6 cm²
Output 18.8 W/cm2 maximum measured for T_E = 1830º C; 10.2 W/cm2 and 15.8 percent efficiency during life test at T_E = 1730º C, T_C = 700º C, and T_R = 345º C
Lifetime 9227 hr before shorting out

29. Lawrence, J.; and Wilson, V. C.: A Comparison of Niobium and Nickel as Thermionic Converter Collector Materials, pp. 6-11.
Emitter W; T_E = 1673 to 2153 K
Collector Nb or Ni; T_C = 873 to 1173 K
Cesium gap 0.025 to 0.508 mm; T_R = 583 to 683 K
Geometry plane
Output voltage is 0.1 to 0.16 V higher with Ni rather than Nb; good performance curves

30. Hobbs, R. L.; and Psarouthakis, J.: A Converter with Vapor Deposited Tungsten Emitter, pp. 12-18.
Emitter Cl¯CVD (~110) W; T_E = 1900 to 2000 K
Collector Mo; T_C = 833 to 1033 K
Cesium gap 0.203 mm; T_R = 563 to 588 K
Geometry plane
Output 11 W/cm2 with 0.5 V at T_E = 2000 K; 9 W/cm2 with 0.45 V at T_E = 1900 K

31. Kitrilakis, S. S.; and Rufeh, F.: The Output Characteristics of an Electroetched Rhenium Surface, pp. 19-26.
Emitter Electroetched Re; T_E = 1555 to 1960 K
Collector Mo; T_C = 843 to 943 K and optimum
Cesium gap 0.013 to 1.016 mm and optimum; T_R = 514 and 616 K and optimum
Geometry plane, guarded
Output fully optimized, 3 W/cm² with 0.2 V at T_E = 1560 K, 7.5 W/cm² with 0.3V at T_E = 1650 K, 13 W/cm² with 0.5V at T_E = 1740K, 18 W/cm² with 0.7 V at T_E = 1860 K, and 40 W/cm² with 0.8 V at T_E = 1960 K; electroetched Re is considerably more effective than electropolished Re

32. Case, J. M.: An Investigation of Thermionic Converter Dynamic Operation, pp. 47-56.
Emitter W, 20 percent Re; T_E = 1500º to 1800º C
Geometry cylindric
Output little information to define performance given in this dynamics study; influences of T_C and T_R considered negligible

33. Sutherland, C. D.; and Ranken, W. A.: Optimization of a Thermionic Diode, pp. 57-65.
Emitter W; T_E = 2100 K maximum
Collector Mo or Ni; T_C = 1000 K
Cesium gap 0.127 or 0.178 mm; T_R = 598 or 643 K
Geometry cylindric; 1.2-cm diameter, variable length (for the analysis)
Output previous data used as bases for numerical optimizations with respect to emitter length and support and output voltage

34. Cahen, O.; and Defranould, P.: Resultats Experimentaux Obtenus Sur des Convertisseurs du Type Nucléaire à. Cesium et Fluorure de Césium, pp. 66-69.
Emitter Mo; T_E = 1450º and 1700º C
Collector Mo; T_C optimum
Cesium gap 0.25 mm; T_R optimum
Additive CsF; T_CsF = 325º to 550º C
Output at 2W/cm² 6.7 percent efficiency for Cs and 8 percent for Cs + CsF; at 4 W/cm² 9.7 percent efficiency for Cs and 10 percent for Cs + CsF; at 6 W/cm² 11.7 percent efficiency for Cs and 10.9 percent for Cs + CsF

35. Rufeh, F.; and Kitrilakis, S. S.: Thermionic Converter Performance in Presence of Inert Gases, pp. 91-98.
Emitter T_E = 1863, 1740, 1645 K
Collector T_C = 873 K
Cesium gap 0.051, 0.254, 0.508, T_R = 558 to 638 K
Additive 0 to 100 torr
Geometry plane, guarded
Output increasing Ar pressure decreases diode output; 10 torr of Ar attenuates electron current 5 to 15 percent

36. Rufeh, F.: The Volt-Ampere Characteristics of a Grooved-Collector Thermionic Diode, pp. 99-105.
Emitter T_E = 1625, 1645 K
Collector Mo with and without grooves; T_C = 773, 873 K
Cesium gap 0.025 to 0.635 mm; T_R = 553 K, 593 K, and variable
Geometry plane, guarded
Output small increase in output for grooved collector over flat one even without optimization

37. Lazaridis, L. J.; and Pantazelos, P. G.: Design of a 5-Kilowatt Flame-Heated Thermionic Power Supply, pp. 126-132.
Emitter W; T_E = 1400º C
Collector Ni
Cesium gap 0.254 mm
Geometry 20 cm²
Output 5 W/cm2 at 0.55 V and 10 percent efficiency

38. Harbaugh, W. E.; and Longsderff, R. W.: The Development of an Insulated Thermionic Converter/Heat-Pipe Assembly, pp. 139-143.
Emitter Mo; T_E = 1300º to 1500º C
Collector Mo; T_C = 625º to 675º C
Cesium gap T_R = 265º to 325º C
Geometry cylindric, 40 cm²
Output 2.05 W/cm² (0.25 V), 2.8W/cm² (0.28 V), 4.0 W/cm²(0.32 V), 5.0 W/cm² (0.38 V), 6.9 W/cm2 (0.45 V)

39. Shefsiek, P. K.: Thermal Measurements of a Thermionic-Converter/Heat-Pipe System, pp. 169-174.
Emitter Mo; T_E = 1450º to 1530º C
Collector Mo; T_C = 475º to 710º C
Cesium gap T_R = 95º to 321º C
Geometry cylindric; 50 cm²
Output 3.2 W/cm² at 0.6 V, T_E = 1510º C, T_C = 710º C, T_R = 318º C

40. Campbell, A. E.; and Jensen, A. O.: Performance of Prototype Thermionic Converters, pp. 175-184.
Emitter Re; T_E = 1735º C
Collector Re or Mo; T_C = 507º to 790º C
Cesium gap 0.089 mm (Re, Re), 0.0051 mm (Re, Re), 0.089 mm (Re, Mo)
Geometry plane; 2.0 cm²faces, 0.4 cm²sidewalls
Output 20 W/cm²at 0.8 V for Re, Re diode with 0.051-mm gap; 15.2 W/cm² at 0.8 V, 21.0 W/cm² at 0.7 V, 26.4 W/cm² at 0.6 V for Re, Re diode with 0.089-mm gap; Re collector gave average of 0.08 V more than its Mo counterpart

41. Rouklove, P.: Thermionic Converter and Generator Tests, pp. 185-191.
Emitter Re; T_E = 1600º, 1700º, 1800º C
Collector Mo; radiation cooled (T_C near optimum)
Cesium gap 0.038 mm; T_R optimum
Geometry plane SET diodes; 2.5 cm²
Output 25 W/cm² (0.6 V), 21 W/cm² (0.7 V), 15.7 W/cm² (0.8 V) with efficiencies near 12.5 percent

42. Brosens, P. J.: The Influence of Design and Materials on the Performance of an Advanced Solar Converter, pp. 192-196.
Emitter Re or Ta; T_E = 2000 K
Collector Mo; radiation cooled (T_C near optimum)
Cesium gap T_R optimum
Geometry solar energy thermionics (SET) (plane); as described in the following table (from ref. 42)

DESCRIPTION OF PROTOTYPE DIFFERENCE

43. Bohdansky, J.; and van Andel, E.: Heat-Pipe Thermionic Converter with a Graphite Absorption Cesium Reservoir Working at Collector Temperature, pp. 239-242.
Emitter Cl¯CVD W (110); T_E = 1755, 1825, 2000 K
Collector Ni; T_C = 843 to 1183 K
Cesium gap 0.10 mm; Cs, graphite reservoir at collector temperatures
Geometry plane, ceramic guarded
Output 4.2 W/cm² at 0.5 V, T_E = 2000 K, T_C = 1183 K

44. Lieb, D.; and Kitrilakis, S. S.: Oxygen as a Steady-State Electronegative Additive in a Cesium Thermionic Converter, pp. 348-354.
Emitter Re; T_E = 1650 to 1850 K
Collector Mo; T_C = 573 to 773 K
Cesium gap 0.127, 0.254, 0.508 mm; T_R = 481 to 538 K
Additive Cs₂O, O₂; collector acted as Cs₂O reservoir
Geometry plane, guarded
Output 6.8 W/cm² for Cs + Cs₂O, 4.4 W/cm²for Cs only at 0.4 V, T_E = 1750 K with 0.254-mm gap; for Cs + Cs₂O I, V curves for 0.127 and 0.508 mm are nearly identical at T_E = 1750 K

45. Long, J. D.; and Psarouthakis, J.: Collector Work Function Investigations in Cesium and Barium-Cesium Vapors, pp. 355-364.
Emitter Ru; T_E = 14250 to 1627 C
Collector Mo; Nb; Nb (O) (oxygenated Nb); Re; Ru; T_C = 390º to 570º C
Cesium gap 0.127, 0. 152 mm; T_R = 175º to 345º C
Additive Ba (Cs diode containing Ba shorted internally without yielding data)
Geometry plane, unguarded; 1.18 cm²
Output as shown in the following table for T_E = 1627 C, T_R optimum, d = 0.152 mm:

46. Backus, C. E.; and Davis, M. V.: The Effect of Iodine and the Inert Gases as Additives in a Cesium Arc Diode, pp. 376-381.
Emitter Ta; T_E = 1850 K
Collector Ni; T_C = 725 K
Cesium gap 0.762 mm; T_R optimum
Additive Ar, Kr, Xe, I
Geometry plane; 2.38-cm diameter
Output for Cs alone, 1.4 W/cm² maximum; output dropped steadily with increasing inert-gas pressure and produced at 30 torr and 0.6 V decreases of 46 percent for Ar, 76 percent for Kr, 83 percent for Xe; with I output at 0.6 V increased by 110 percent at 36 torr, then diminished to the initial (Cs only) value at 120 torr

47. Jester, A.; Gross, F.; Holick, H.; and Busse, C. A.: A Nuclear Heated Thermionic Converter, pp. 419-425.
Emitter Mo; T_E = 1460 to 2010 K
Collector Nb; T_C = 923 to 953 K
Cesium gap 0.204 mm; T_R optimum
Geometry cylindric; 1.6-cm diameter, 20 cm²
Output 9 W/cm² with 11 percent efficiency at T_E = 2000 K, T_R = 360º C (optimum); in-core performance plots

48. Wilson, V. C.; and Lawrence, Jackson: Characteristics of a Thermionic Converter with a Fluoride Vapor Deposited Tungsten Emitter Etched to Preferentially Expose the 110 Crystal Planes, pp. 1-9.
Emitter F¯CVD W (100) etched to expose 110 W faces and 40 percent more area; T_E = 1650 to 2150 K
Collector Nb; T_C optimum
Cesium gap 0.025 to 0.508 mm; T_R optimum
Geometry plane, guarded
Output 42 W/cm² with 50 A/cm², 20 percent efficiency and 30 W/cm² with 30 A/cm², 23 percent efficiency for d = 0.051 mm, T_E = 2155 K, T_C = 973 K; unusually high outputs at low Cs pressures and large spacings; greatest outputs came with gaps of 0.254 mm or more; good performance maps
Lifetime performance decayed because of thermal reforming at 2155 K

49. Howard, R. C.; von Someren, L.; and Yang, L.: Preliminary Results on the Thermionic Performance of a Vapor-Deposited Tungsten Emitter having (110) Preferred Orientation, pp. 10-12.
Emitter Cl¯CVD W (110); T_E = 1700, 1735, 1850 K
Collector Mo; T_C = 470º to 660º C
Cesium gap 0.127 mm
Geometry plane, unguarded
Output 16 W/cm² at 0.5V, T_E = 1850 K; 9.8 W/cm² at 0.39 V, T_E = 1700 K

50. Holland, J. W.; and Kay, J.: Performance of a Cylindrical Geometry Thermionic Converter with an Improved Work Function Tungsten Emitter, pp. 13-17.
Emitter F¯CVD W (100); Cl¯CVD W (110); T_E = 1600º to 1800º C
Collector Mo; Nb; T_C optimum
Cesium gap 0.229 mm; T_R optimum
Geometry cylindric thermionic fuel (nuclear) elements (TFE’ s)
Output Cl¯CVD W emitter gave 25 percent more power than F¯CVD W; Mo collector, 40 percent more than Nb at optimum current densities
Lifetime over 3600 hr for F¯CVD-W, Nb diode; over 6000 hr for Cl¯CVD-W, Nb diode

51. Koskinen, M. F.; and Gammel, G.: A Direct Comparison of Molybdenum and Nickel as Collector Materials, pp. 18-24.
Emitter None
Collector Comparison of Ni and Mo; T_C = 400º to 730º C
Cesium gap 0.210 mm cold, 0.15 mm at 700º C; T_R < 485 K
Geometry plane double-collector isothermal diode; 4 cm²
Output Mo collector was superior to Ni, giving 0.05 to 0.14 V lower cesiated surface potentials

52. Rufeh, F.; Lieb, D.; and Fraim, F.: Recent Experimental Results on Electronegative Additives, pp. 25-28.
Emitter T_E = 1500 to 1900 K
Cesium gap T_R = 433 to 638 K
Additive CsO₂
Geometry plane, fixed-gap
Output CsO₂increased Cs diode performance considerably; diode was run with Cs only, then with Cs + CsO₂, and finally with Cs alone; Cs₂O improved performance, reduced Cs pressure, decreased electron scattering in gap, and allowed operation with higher diode-component temperatures; performance curves

53. Shimada, Katsunori: Apparent Work Function of Cavity Emitters, pp. 29-32.
Emitter Ta with cavities; T_E = 1200 to 2100 K
Collector Mo; T_C = 400º C
Cesium gap 0.051 mm; 0.324 to cavity bottoms
Geometry plane, unguarded; 2 cm²
Output work functions from saturation currents and J, V curve knees were 0.4 eV lower than predicted by Rasor, Warner theory

54. Rufeh, F.; and Lieb, D.: Volt-Ampere Characteristics in the Presence of Inert Gases, pp. 33-37.
Emitter T_E = 1800 K
Collector T_C optimum
Cesium gap 0.254, 1.016 mm; T_R optimum
Additive Xe, Kr, 0 to 213 torr
Output both Kr and Xe decreased diode performance with increasing pressure; at T_E = 1800 K, d = 0.254 mm a 20 percent current drop resulted for 60 torr Xe or for 100 torr Kr; previous reports of output gains with inert gas additions probably resulted from oxygen contamination

55. Bliaux, J.; and Clémot, M.: In Pile Thermionic Life Test Sirene 302, pp. 38-46.
Emitter CVD W; T_E = 1350º to 1700º C
Collector Nb, 1 percent Zr; T_C = 741º to 814º C
Cesium gap 0.16 mm; T_R = 693º to over 860º C
Additive emitter backed by 20 percent enriched UO₂
Geometry cylindric; 4 cm long, 20 cm²
Output 4.25 W/cm2 with 10.6 percent efficiency at 0.78 V, T_E = 1695º C, T_C = 763º C, T_R = 810º C
Lifetime 1650 hr without degradation

56. Speidel, T.: Performance Comparison of Nine RD-502 Cylindrical Diodes with Etched Rhenium Emitters, pp. 47-50.
Emitter etched Re
Collector Nb; PVD Mo
Geometry cylindric; 3.81 cm long, 15 cm²
Output as shown in the following table (from ref. 56):

RD-502 DIODES WITH ETCHED RHENIUM EMITTERS

57. Paquin, M. L.: Testing of a Calorimeter-Equipped Planar Thermionic Converter, pp. 51-55.
Emitter etched Re; T_E = 1860 K
Collector VD Mo; T_C = 973 K
Cesium gap 0.114 mm; T_R = 289º to 373º C
Geometry plane; 1.77 cm²
Output as shown in the following table (from ref. 57):

DATA SUMMARY

58. Brosens, Pierre J.: Advanced Converter Development, pp. 68-73.
Emitter etched Re; T_E = 1800, 1900, 2000 K
Collector Nb; Pd; Re
Cesium gap 0.051 mm; T_R optimum
Geometry plane; 2.5 cm²
Output diode voltages decreased by averages of 0.037 V for Pd and 0.074 V for Nb relative to those for Re collector

59. Rouklove, Peter: Thermionic Converter and Generator Tests, pp. 75-85.
Emitter Re; T_E = 1600º to 1800º C
Collector Mo; T_C optimum
Cesium gap T_R optimum
Geometry plane SET diodes
Output as shown in the following tables (from ref. 59):

Table 1. - Performance of SET-type converters

Table 2. - Converter characteristics

60. Lazaridis, L.; Shai, I.; and Shefsiek, P.: Development of a 300-Watt Flame-Heated Thermionic Power Supply, pp. 86-92.
Emitter W; T_E = 1380º, 1425º, 1450º C
Collector Ni; T_C = 580º C
Cesium gap 0.254 mm
Geometry 29 cm²
Output 2.9 W/cm² at 8.6 percent efficiency, T_E = 1380º C

61. Bohdansky, J.; Salamon, K.; and van Andel, E.: Integrate Cs-Graphite Reservoir System in a Heat Pipe Thermionic Converter, pp. 93-96.
Emitter W; T_E = 1640 to 1930 K
Collector W; T_C optimum
Cesium gap 0.5 mm; T_R ≈ T_C for Cs, C compound reservoir
Geometry plane
Output 1.8 W/cm² (T_E = 1640 K) to 4.1 W/cm² (1930 K)

62. Koskinen, M. F.; Gammel, G.; Gross, F.; DeTroyer, A.; Ne’ve de Mévergnies, E.; and Dejonghe, P. A. J.: An Actinium-227 Fueled Thermionic Generator, pp. 102-109.
Emitter single crystal 110 W; T_E = 1800 K
Collector Mo; T_C = 981 K
Cesium gap 0.2 mm; T_R = 603 K
Geometry plane; 4 cm²
Output 5.3 W/cm² at 0.53 V

63. Gronroos, Henrik G.; Davis, Jerry P.; Weaver, Lynn E.; and Guppy, James G.: A Control System Study for an In-Core Thermionic Reactor, pp. 130-137.
Emitter W; T_E = 1500 to 2000 K
Collector Mo; T_C optimum
Cesium gap 0.254 mm; T_R optimum
Output SIMCON performance plots; as shown in the following table:

64. Shefsiek, P. K.: Reproducibility of Thermionic Performance, pp. 99-102.
Emitter Re; T_E = 1975, 2000 K
Collector Mo; T_C = 773 to 1093 K
Cesium gap 0.051 mm; T_R = 583 to 633 K
Geometry plane; 2 cm²
Output average of 12 diodes 18.8 W/cm²(17.5 to 20.3) at 0.7 V, T_E = 2000 K, T_C,ave = 1045 K, T_R,ave = 630 K

65. Merrill. O. S.: Correlation of Fixed-Spacing Thermionic Converter Performance with Variable-Spacing Test Vehicle Data, pp. 103-112.
Emitter Re (polycrystal or vapor-deposited); T_E = 1600 to 2100 K
Collector Re (polycrystal or vapor-deposited); T_C = 983 to 993 K and optimum
Cesium gap 0.080 to 0.305 mm; T_R = 562 to 604 and optimum
Geometry seven plane diodes, 2 cm²one cylindric 2 cm²
Output for 0.127 mm, maximums are 24 W/cm²(0.69 V, T_E = 2100 K), 20 W/cm² (0.60 V, T_E = 2000 K), 17 W/cm²(0.52 V, T_E = 1900 K), 11.4 W/cm²with 8.9 percent efficiency (0.41 V, T_E = 1800 K), 7 W/cm² (0.28 V, T_E = 1700 K); good performance curves

Lifetime 11600 hr for one diode at 27 W/cm², 0.77 V, 2000 K

66. Speidel, T. O.; and Williams, R. M.: Fixed-Space Planar Thermionic Diode with Collector Guard Ring, pp. 113-117.
Emitter Re; Ta; T_E = 1505º to 1680º C
Collector Nb
Cesium gap 0.254 mm; T_R optimum
Geometry plane, guarded; 1.82 cm²
Output not maximums but highest tested for each: 14.4 W/cm² (Re, 1660º C, 0.4 V), 4.2 W/cm² (Ta, 1680º C, 0.3 V)

67. Williams, R. M.; and Kascak, T. J.: A Comparison of the Performance of Two Rhenium, Niobium Cylindrical Thermionic Converters, pp. 118-122.
Emitter F¯CVD Re mechanically polished or etched; T_E = 1875 to 2075 K
Collector Nb; T_C = 973 K for T_E = 1900 K and optimum
Cesium gap 0.254 mm; T_R optimum
Geometry cylindric; 1.28-cm diameter, 15.2 cm²
Output for maximum electrode efficiencies from 1875 to 2075 K, 6.8 to 9.2 W/cm² with 12.6 to 14.6 percent efficiency for mechanically polished Re, 5.5 to 8.3 W/cm with 11.4 to 13.6 percent efficiency for electroetched Re

68. Kascak, T. J.; and Williams, R. M.: The Performance of a Rhenium, Niobium Cylindrical Thermionic Converter, pp. 123-127.
Emitter vapor-deposited, electroetched. Re; T_E = 1600 to 2050 K
Collector Nb; T_C = 873 to 1173 K
Cesium gap 0.254 mm; T_R optimum
Geometry cylindric; 1.27-cm diameter, 15.2 cm²
Output for maximum efficiency, 1.2 to 8.1 W/cm² with 5.2 to 13.4 percent efficiency; for maximum power, 1.4 to 8.8 W/cm² with 4.9 to 12.8 percent efficiency

69. Peelgren, M.; and Speidel, T.: Large Cylindrical Thermionic Diode with Rhenium Emitter for Diode Kinetic Experiments, pp. 128-133.
Emitter etched Re; T_E = 1600º and 1770º C
Collector Mo (Mo, Nb data in comparison); T_C optimum
Cesium gap 0.254 mm; T_R optimum
Geometry cylindric; 1.905-cm diameter, 30 cm²
Output maximum power 3.8 to 9.8 W/cm², maximum efficiency 9.4 to 13.2 percent; results comparable with averages for six Re, Mo and three Re, Nb diodes having 0.178-mm gaps and 15-cm² emitters

70. Wang, C. -C.; and Ward, J. J.: Performance of Chloride and Fluoride Vapor-Deposited Tungsten Emitters in Thermionic Converters, pp. 134-140.
Emitter Cl¯CVD W (110); F¯CVD W (100); etched F¯CVD W (110); T_E = 1600 to 2000 K
Collector Nb; T_C optimum
Cesium gap 0.203 mm; T_R optimum
Geometry six plane diodes
Output as shown in the following table for polycrystalline 110 types at 10 A/cm²:

71. Rufeh, F.; and Lieb, D.: Emission Characteristics of a Duplex Vapor-Deposited Tungsten Emitter, pp. 141 to 150.
Emitter Duplex W (Cl¯CVD on F¯CVD); T_E = 1600 to 1915 K
Collector Mo; T_C= 900 and 950 K
Cesium gap 0.013 to 1.016 mm; T_R’s giving 0.5 to 11 torr
Geometry plane, guarded
Output excellent performance maps; for optimum spacings and cesium pressures at 10 A/cm² output was as follows:

72. Ernst, D. M.: Performance Comparison of Four Cylindrical Diodes with Various Types of Tungsten Emitters, pp. 151-154.
Emitter F¯CVD W (100): (1) as-deposited, (2) etched as-deposited, (3) as-ground, (4) etched as-ground; T_E = 1800º C or less
Collector Nb; T_C optimum
Cesium gap 0.254 mm; TR optimum
Geometry 1.27-cm diameter, 15 cm²
Output as shown in the following table:

73. Shimada, K.: Side-Wall Currents in Unignited Hardware-Type Thermionic Energy Converters, pp. 155-158.
Emitter Re; T_E = 1700 to 2016 K
Geometry SET plane diode
Output side-wall-current theory agrees with test results

74. Stapfer, G.; and Shimada, K.: Electrical Testing of a Six-Converter Generator, pp. 159-163.
Emitter Re; T_E = 1600º and 1700º C
Collector Mo; T_C near optimum (radiation cooling
Cesium gap T_R optimum
Geometry six SET plane diodes in a generator, 2 cm² each
Output for the generator, 140 W at 3.0 V (4.0 V without lead losses), 4.5 percent efficiency, T_E = 1700º C; 96 W at 3.0 V (3.75 V without lead losses), 4.5 percent efficiency (at 3.5 V), T_E = 1600º C; averages for the diodes, 11.7 W/cm²at 0.67 V, T_E = 1700º C; 8 W/cm²at 0.62V, T_E = 1600º C

75. Hansen, L. K.: Thermionic Research at Stresa (A Review), pp. 178-187.
Emitter T_E = 1800 K
Collector T_C optimum
Cesium gap 0.254 mm; T_R optimum
Additive Ar, Xe
Output additions of inert gases only degrade diode performance; at 10 A/cm² 40 torr of Ar caused a drop from 3.4 W/cm² to 2.4 W/cm²

76.Dagbjartsson, S.; Groll, M.; Schförb, O.; and Pruschek, R.: An Improved Out-of-Core Thermionic Reactor for Low Power, pp. 299-304.
Emitter Re; T_E = 1850 K
Collector Mo probably
Output 8 W/cm²

77. Lieb, D.; and Rufeh, F.: Thermal Stability as a Function of Converter Performance, pp. 318-322.
Emitter T_E = 1600 to 2000 K
Cesium gap 0.127 to 0.305 mm; T_R = 548 to 635 K
Output I, V curves for high- and low-performance diodes used to show that above-optimum TR’s insure against in-core thermal runaway

78. Jacobson, Dean L.; and Campbell, A. E.: The Characterization of Bare and Cesiated CVD 75 Percent Tungsten/25 Percent Rhenium Electrodes, pp. 26-33.
Emitter 75 percent W, 25 percent Re; T_E = 1800, 2000 K
Collector 75 percent W, 25 percent Re; T_C = 927 to 1000 K
Cesium gap 0.003 to 0.762 mm; 0.254-mm fixed gap; T_R = 588 to 650 K
Geometry variable-parameter, plane, guarded diode; fixed-gap plane diode; cylindric diode; each 2 cm²
Output 16 W/cm² at 0.5 to 0.6 V, T_E = 2000 K for fixed-gap plane diode; 18 W/cm² at 0.4 to 0.5 V, T_E = 2000 K for cylindric diode

79. Pigford, Thomas H.; and Thinger, Byron E.: Performance Characteristics of a 0001 Rhenium Thermionic Converter, pp. 34-38.
Emitter 1-xtal 0001 Re; T_E = 1600 to 2000 K
Collector Nb; T_C = 933 K
Cesium gap 0.254 mm; T_R = 507 to 611 K
Geometry plane, guarded; 0.621 cm²
Output maximum electrode power densities, 5.1 W/cm² at T_E = 1600 K to 15.4 W/cm² at T_E = 2000 K; at 10 A/cm², T_C = 933 K, T_R = optimum, power density was as follows:

80. Wilson, V. C.; and Danko, J. C.: Development of a Stable Faceted Tungsten Emitter Surface, pp. 46-52.
Emitter F¯CVD W (100) etched to 110 faces (compared with polycrystalline W, 100 W, and 112 to 114 W); T_E = 1650 to 2150 K
Collector Nb; T_C optimum
Cesium gap spacing optimum; T_R optimum
Geometry plane, guarded
Output 4.2 W/cm²at 10 A/cm²and T_E = 1650 K to 13.9 W/cm²at 10 A/cm² and T_E = 2150 K

Lifetime 150 hr with no effect at 1980 K; surface changed after 22 hr at 2130 K

81. Lieb, D.; Donaker, A.; and Rufeh, F.: Performance of a Thermionic Converter with a Nominal Single-Crystal (110) Tungsten Emitter and a Niobium Collector, pp. 66-75.
Emitter 110 W (several crystals with 110 faces within 4º of emitter surface); T_E = 1600 to 2000 K
Collector Nb; T_C = 700 to 1025 K
Cesium gap 0.013 to 1.016 mm; T_R = 528 to 653 K
Geometry plane, guarded
Output performance is better than that for a high-output Cl¯CVD W diode below 0.47 V at T_E = 1700 K and below 0.8 V at T_E = 1900 K; excellent performance maps; fully optimized at 10 A/cm²power as shown in the following table:

82. Wilson, V. C.: A Review of Thermionic Converter Tests, pp. 82-89.
Emitter several orientations and surface preparations for W and for Re; W, 25 percent Re; Mo; Ta; T_E = 1650 to 2150 K
Collector W + WO₂on Nb; Mo; Nb; Ni; Re; T_C optimum
Cesium gap 0.051 to 0.508 mm and optimum; T_R = 513 to 633 K and optimum
Geometry plane
Output excellent condensation and comparison of output results mostly for high-performance diodes

83. Breitwieser, Roland; Manista, Eugene J.; and Smith, Arthur L.: Computerized Performance Mapping of a Thermionic Converter with Oriented Tungsten Electrodes, pp. 90-99.
Emitter single-crystal 110 W; T_E = 1550 to 1950 K
Collector single-crystal 110 W; T_C = four temperatures around peak-power point
Cesium gap 0.025 to 0.305 mm; T_R = 520 to 600 K
Geometry plane, guarded; 1.02-cm diameter
Output for 0.203 mm and T_R = 600 K maximums were 3 W/cm² at 0.4 V, T_E = 1750 K; 3.8 W/cm² at 0.4 V, T_E = 1850 K

84. Clemot, M.; Gayte, B.; Lebourg, R.; and Tripet, J.: Life Testing and Performance Stability of Cylindrical Thermionic Converters, pp. 100-108.
Emitter F¯CVD W (100); T_E = 1300º to 1650º C
Collector Mo or Nb, 1 percent Zr; T_C optimum
Cesium gap 0.20 to 0.25 mm; T_R optimum
Geometry cylindric, 20 cm²
Output as shown in the following table (from ref. 84):

85. Gunther, B.: Converter Performance Comparison, pp. 109-114.
Emitter F¯CVD W (100); T_E = 1600 to 2000 K
Collector Nb; T_C optimum
Cesium gap 0.254 mm; T_R = 330º to 400º C
Geometry 12 cylindric diodes, each 20 cm²
Output as shown in the following table (with a 3.7 percent standard deviation):

86. Samstad, G. I.; Case, J. M.; and Danko, J. C.: Design, Operation and Post-Test Analysis of a High Performance Cylindrical Converter, pp. 115-121.
Emitter Cl¯CVD W (110); T_E ≈ 1700º C
Collector Nb; T_C ≈ 700º C
Cesium gap 0.254 mm; T_R = 340º to 372º C
Geometry cylindric; 1.42-cm diameter, 11.0 cm²
Output 7.4 W/cm² maximum at T_E = 1700º C, T_C = 700º C, T_R = 360º C; 9.5 W/cm² maximum at T_E = 1710º C, T_C = 710º C, T_R = 354º C after 5000 hr

Lifetime removed after 5000 hr for examination

87. Hamerdinger, Randolph W.; and Jacobson, Dean L.: Design and Performance of Low Temperature Cylindrical Thermionic Converters, pp. 122-129.
Emitter Cl¯CVD Re; T_E = 1573, 1673, 1800 K
Collector Cl¯CVD Re; T_C = 875 to 976 K and optimum
Cesium gap 0.152 mm (2 cm²), 0.203 mm (4 cm²); T_R = 582 to 612 K and optimum
Geometry cylindric; two with 2-cm²emitters, three with 4-cm² emitter
Output 10.3 W/cm² at T_E = l800 K for 2 cm², 4.25 W/cm² at l673 K for 4 cm²

88. Bliaux, J.; Marquer, P.; Dumas, P.; Leclere, A.; Desmarest, C.; and Ducrocq, D.: In Pile Life Testing of Thermionic Converter Sirene 311, pp. 130-140.
Emitter F¯CVD W (100) on Mo (backed by enriched UO₂); T_E = 1560º C (out of core), 1601º C (in core)
Collector Nb, 1 percent Zr; T_C=632º C (out of core)
Cesium gap 0.2 mm; T_R optimum for Cs, C compound reservoir
Geometry cylindric; 20 cm²
Output out of core, 5 W/cm² at 10 percent efficiency; in core, 4.6 W/cm² at 8.5 percent efficiency
Lifetime 4740 hr in 6-MW reactor (2x10¹² N/cm²), 3800 hr with no degradation; test terminated by emitter shortout

89. Jester, A.; Holick, H.; Krapf, R.; and Zöller, R.: Thermionic Converter Development for ITR, pp. 141-144.
Emitter Mo (with and without UO₂ backing); T_E = 1400º to 1700º C
Collector T_C =600º to 700º C
Cesium gap T_R = 350º to 370º C and optimum
Output and in-core test: UO₂ fueled emitter at 1400º to 1500º C, collector at lifetime 600º to 700º C, and reservoir at 350º C gave 3.5 to 5 W/cm² at 0.5 to 0.6 V for 3750 hr; out-of-core tests: as shown in the following table (from ref. 89):

OUT-OF-CORE TEST^a