I am so confused between the unit of nA, pnA, enA, and pps.


pps = particle per second.

pnA  = particle nanoampere.
The electrical current in nanoamperes (10^{-9}A) that would be measured if all beam ions were singly charged. i.e. neglecting the actual charge state. 1 \textrm{pnA} =  6.25 \times 10^{9} \textrm{ions/second}

enA = pnA × Charge state.

In this sense, enA = nA, the actual current carried by the beam.

In General

\textrm{pnA} = \textrm{pps} \times e \times 10^9

\textrm{enA}  = \textrm{nA} = Z \times \textrm{pps} \times e \times 10^9

where e is electron charge.


For example, 12C with charge state of 6+ at 4 \times 10^{10} pps.

= 4 \times 10^{10} \times e \times 10^{9} = 6.41 \textrm{pnA}

or

= 6 \times 4 \times 10^{10} \times e \times 10^{9} = 38.5 \textrm{nA} = 38.5 \textrm{enA}


An ion beam of 5+ charge state at 1 pnA.

= 1 / e  10^{-9} = 6.24 \textrm{pps}

or

= 5 \textrm{enA}  = 5 \textrm{nA}

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