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453

Appendices

1. Some Physical Constants

Boltzmann constant

k = 1.38 x 10-16 erg/deg

= 8.6164 x 10-5 eV/deg

Avogadro’s number

6.028 x 1023

Loschmidt’s number

2.687 x 1019 cm2

Electron mass

m = 9.108 x 10-28 g

Proton mass

M = 1.672 x 10-24 g

Electron charge

e = 4.802 x 10-10 esu

1.6 x 10-19 C

Planck’s constant

h = 6.625 x l0-27 erg× sec

Radius of first Bohr orbit

ao = 0.529 x 10-8 cm

Electron volt

1 eV

= 1.6 x 10-12 erg

= 23.06 kcal/mole

= 8066 cm-1

Stefan-Boltzmann constant s

5.76 x 10-12 joule/(cm2× sec× deg4)

Wavelength of electron with energy E in eV

l = 12.264 x 10-8(E)-1/2

Average electron velocity with energy E in eV

ve@ cm/sec = 6.23 x 105 (Te,° K)1/2

= 5.93 x 107 (E, eV)1/2

Mean ion (Cs) velocity with energy E in eV

vi@. cm/sec = 1.25 x 103 (Ti,° K)1/2

= 1.19 x 105 (E)1/2

Debye length

LD cm = 6.87 (Te,° K/n, cm-3)1/2

Plasma (Langmuir) frequency

w p Hz = 5.66 x 104(n, cm-3)1/2

454

2. Correlation of Some Physical Quantities for a Cesium Plasma

Fig. Appendices 2

455

3. Some Emission Parameters*

Element

Work Function (f ), eV

Richardson’s Constant (A) amp/cm2× deg2

Remarks

3 Li

2.33

11 Na

2.35

19 K

2.22

28 Ni

4.5

20 ± 5

Polycrystal, value of f is apparently reduced by 0.3 - 0.5 eV

4.89 ± 0.03

900

Face [100]

5.22 ± 0.03

1800

Face [111]

29 Cu

4.4

60.2

Polycrystal

5.6

Face [100]

4.87

Face [111]

37 Rb

2.16

41 Nb

3.99

Polycrystal

3.95 ± 0.03

90 ± 20

Face [100]

4.80 ± 0.05

80 ± 30

Face [110]

3.88 ± 0.03

15 ± 20

Face [111]

42 Mo

4.3

Polycrystal

4.4 ± 0.03

Face [100]

5.05 ± 0.05

Face [110]

4.12 ± 0.03

Face [111]

47 Ag

4.3

Polycrystal

54 Cs

1.81

56 Ba

2.49

73 Ta

4.12

Polycrystal

4.15 ± 0.02

Face [100]

4.7

Face [110]

4.0

Face [111]

74 W

4.54

Polycrystal

4.65 ± 0.02

Face [100]

5.33 ± 0.04

Face [110]

4.3 ± 0.1

Face [111]

75 Re

5.0

Polycrystal

5.53 ± 0.03

790 - 120

Face [1000]

5.05 ± 0.04

140

Face [1010]

78 Pt

5.32

Polycrystal

79 Au

4.3

Polycrystal

Stainless Steel

4.76

*Data recommended by V.S. Fomenko and G.W. Samsonov in Handbook of Thermionic Properties, Plenum, New York (1966). (also see Solid State Surface Science, ed. by M. Green, Vol. 1, Dekker, New York (1969))

456

4. Temperature Dependence of Thermionic Emission At Different Emitter Work Functions.

Fig. Appendices 4

457

5. Temperature Dependence of Equilibrium Electron Density at Different Cesium Vapor Pressures.

Fig. Appendices 5

458

6. Temperature Dependence of Chemical Potential at Different Cesium Vapor Pressures.

Fig. Appendices 6