| CPC H01J 37/32128 (2013.01) [H01L 21/67069 (2013.01); H01J 2237/327 (2013.01)] | 14 Claims |

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1. An apparatus to produce a waveform, the apparatus comprising:
a first node;
a switched path that couples a second node to the first node, and responsive to the switched path being closed, a pulse is initiated at the first node; and
a power supply coupled to the first node, the power supply configured to produce, after the switched path is open, a ramped voltage at the first node;
control circuitry to:
repeatedly close and open the switched path to produce pulses; and
adjust current to the first node by varying a non-zero repetition rate of the closing and opening of the switched path.
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