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Although the first experiment appears rather observational and qualitative, it contains a lot of interesting basic physics. You should question all aspects of the observations and try to find explanations. In order to stimulate some thoughts, consider to answer these questions:

1. What is the distribution of the electric field which accelerates the beam electrons?
2. What is the beam electron density?
3. What is the neutral gas density in the "vacuum" chamber?
4. How large would be the space charge electric field of the
5. Why is the beam diverging?
6. What is the typical mean free path of the beam electrons?
7. What is the electron transit time through the device?
8. How is the beam current closed?
9. Estimate the plasma density required for current closure?
10. Is the cathode current equal to the beam current?
11. How much power is applied to generate the beam?
12. Account for the energy of the beam.
13. How much magnetic field does the beam produce?
14. How much voltage is required to reflect a beam which is aimed obliquely against a biased grid?
15. How does the beam density vary when the beam is reflected by a negatively biased grid?
16. Can the beam electrons be trapped by multiple reflections between two negatively biased grids?
17. Why does the beam color vary with beam energy?
18. Why is the background plasma not visible?
19. Estimate the electric field in the dark layer in front of the grid when the beam is reflected.
20. If the sheath is 10 Debye lengths thick what is the typical electron density?
21. How much current flows to the grid when the beam is reflected (measure and explain)?
22. Determine the magnetic field direction and magnitude from the cyclotron orbit.
23. Can the magnetic field be uniquely determined from the cyclotron orbit?
24. What is the cyclotron radius of the beam in the Earth's magnetic field?
25. Calculate the cyclotron frequency and period.
26. Compare the electromagnetic forces to the centripetal forces on the beam electrons.
27. Find the number of turns of the external coils from the field, current, and geometry.
28. What is the magnetic moment of a circular electron beam in an external magnetic field?
29. What is the direction of the beam-produced magnetic field?
30. For which beam current does the beam-produced magnetic field equal the external field?
31. How does the electron energy vary along a closed cyclotron orbit?
32. How does the electron energy vary along the orbit when the electrons perform an E×B drift?
33. Find direction and magnitude of the electric field from the cycloidal beam trajectory.
34. If an "unmagnetized" plasma shields electric fields, how can we produce an electric field in a magnetized plasma?
35. Does, on the average, an electron gain energy in an E×B drift? Where does come from?
36. What is the axial magnetic field profile of the coil system in the laboratory?
37. For a spiralling beam, how does the cyclotron radius vary with magnetic field strength?
38. How much magnetic flux is enclosed by an electron cyclotron orbit? Show that it is conserved in a nonuniform magnetic field.
39. How does the mirror point vary with beam injection angle?
40. Estimate the electron bounce time/frequency between two mirror points.
41. How can one distinguish an E×B drift from a gradient/curvature drift?
42. Estimate the gradient and curvature drift velocity from the observed beam trajectory.
43. When the electron beam is mirror-reflected what force does it exert and on what?
44. What happens to the electron energy when the mirror points are moved toward one another?
45. What happens to the electron energy when the magnetic field oscillates at the cyclotron frequency?
46. In the laboratory setup what limits the frequency at which the magnetic field can be varied?
47. At which beam energy do relativistic effects become important? What are they?
48. At which speed does the contracting magnetic force on an electron beam equal the diverging electric force due to its space charge?
49. What determines the penetration distance of an electron beam into air, vacuum, and matter?
50. Where in nature do electron beams occur? What are man-made electron beams used for?
51. Is the beam current limited by space charge or temperature?

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