... touching¹

Avoid rubbing which may result in charge separation of opposite sign (depending on the proofball metal and type of insulator: ``triboelectric series'', see exp #6 of Part II).

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... fact:²

The actual $B$ at the maximum electron orbit is only $\sim$ 0.5% less. See Price, ``Electron trajectory in an $e/m$ experiment'', Am. J. Phys. 55, 18, (1987)

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... brightness³

CAUTION: a stationary intense spot may damage the screen

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... silicon;⁴

As one might expect since silicon has valence 4, phosphorus valence 5, and aluminum valence 3

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