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1. For typical parameters of the laboratory plasma (n_e = 10⁹  cm^-3, kT_e  = 1 eV, 0.5 mTorr Ar), calculate the Debye length, plasma frequency, electron-neutral collision frequency, mean free path, thermal velocity, degree of ionization, and the ion acoustic speed.
2. Why does the single Langmuir probe characteristic show no constant "saturation" currents.
3. What is the effect of the primary discharge electrons on the I-V probe characteristics?
4. What determines the plasma potential in a discharge?
5. What determines the floating potential in a discharge?
6. What is the effect of the probe geometry and size on the I-V characteristics?
7. What is the effect of a resistance in the cable between probe and sweeper on the I-V characteristics?
8. Where is the power applied to the Langmuir probe dissipated?
9. Why does a floating probe perturb the plasma density?
10. How do collisions effect the I-V characteristics? Can you measure the electron density in a flame with a Langmuir probe?
11. Is the electron emission from the filaments temperature or space charge limited? Why?
12. What determines the plasma density in a discharge?
13. How much energy (in eV per ion) is required to produce a dc plasma. How can the efficiency be increased?
14. What is the ratio of discharge power to heater power? How can the efficiency be increased?
15. How large is the ion saturation current to the walls compared with the discharge current?
16. Why are the ions colder than the electrons but hotter than the neutrals?
17. Why do we use expensive argon instead of cheap air for making a discharge plasma?
18. If the plasma density was proportional to the neutral density what density could we obtain at atmospheric pressures? How would the discharge look like?
19. If the plasma density was proportional to the discharge current at which current would one obtain full ionization? Is this feasible?
20. Which plasmas in nature are produced by impact ionization? List man-made applications.
21. In a double probe how does each probe potential vary with respect to ground when the bias voltage is changed?
22. Explain the difference in temperature obtained from a single probe and a double probe.
23. How does a single and double probe trace look like in the presence of primary electrons, without secondary electrons?
24. What is the effect of a large voltage drop across the current-measuring shunt on the observed I-V curve?
25. Suggest how to build a probe which produces a constant saturation current.
26. What is the effect of the filament voltage on the distribution of primary electrons?
27. Why is the Langmuir probe I-V characteristics nearly a straight line in the presence of primary electrons?
28. Some I-V curves of double probes do not go through the origin. Explain why.
29. From a Langmuir probe trace how can one separate two Maxwellians with large differences in temperature and density?
30. Suggest different ways to measure the slope of the double probe characteristic at the origin.
31. In the double probe measurements what is the effect of a leakage resistance to ground on the I-V characteristics?
32. In the double probe measurements what is the effect of two unequal probe areas or a density gradient on the I-V characteristics?
33. How large is a double probe current measured on a satellite in the auroral ionosphere with density 1/cc and temperature 1 eV?
34. How large is a double probe current measured in a laser-produced plasma with density 10exp18/cc and temperature 1 keV?
35. Describe the major features of an emissive probe: I-V characteristics, applications, limitations.
36. Is the electron emission of an emissive probe temperature-limited or space charge limited? Support your answer with data.
37. What determines how closely an emissive probe floats at the plasma potential?
38. What are the advantages of an emissive probe over a single Langmuir probe in determining the plasma potential?
39. Compare the differential resistance dV/dI at the floating potential for a cold probe and for an emissive probe. Discuss its significance.
40. How does the dc voltage drop along the heated filament of an emissive probe affect the I-V characteristics? How can one minimize or eliminate the measurement error?
41. What is the effect of a temperature gradient along the emissive filament of an emissive probe on its I-V characteristics?
42. Suggest a probe which can measure instantaneously the electric field in a plasmas.
43. Discuss the I-V characteristics of a "double" probe consisting of one cold and one emissive electrode.
44. The electric field in a plasma can be obtained from the gradient in the floating potential of an emissive probe. Discuss the errors caused by additional density or temperature gradients in the plasma.
45. Does a floating emissive probe have a sheath?
46. Can a coated cathode (like the one used in the beam studies) be used as an emissive probe?
47. How does a drift in the electrons, i.e., electron current affect the I-V characteristics of an emissive probe?
48. What determines the floating potential of an emissive probe in a cloud of primary electrons?
49. What limits the time resolution in measuring the plasma potential with an emissive probe?
50. What limits the spatial resolution in measuring the plasma potential with an emissive probe?
51. Discuss the limitations of an emissive probe in a hot, dense fusion plasma and a cold, dilute space plasma.

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