Figure: 1 Experimental setup for electron temperature measurements If the distance (A) from the plasma to the relay lens (focal length 55 mm) is 91 mm and the distance (B) from the relay lens to the pinhole is 139 mm, the magnification is ~1.5X. If the relay lens with the focal length of 30 mm is used and the distances (A) and (B) are 230 mm and 34.5 mm respectively, the magnification is ~0.15X

Figure 2: The light intensity ratio distribution

Figure 3: The Boltzmann plot with a straight-line slope of approximately -1.12

Figure 4: Electron temperature distributions

Figure 5: Electron temperature vs. pressure

Figure 6: Actual interference fringes

Figure 7: The extrapolation example of its frequency

Figure 8: Electron density vs. gas pressure

Species

Wavelength [nm]

Lower Energy Level Ej [eV]

Upper Energy Level Ei [eV]

Transition Probability
Aij [106 s-1]

Upper Statistical Weight gi

Ar I

415.859

11.55

14.53

1.4

5

Ar I

420.068

11.55

14.50

0.967

7

Ar I

696.543

11.55

13.33

6.4

3

Ar I

706.722

11.55

13.30

3.80

5

Ar I

738.398

11.62

13.30

8.46

5

Table 1: Spectral lines of Ar I