Faraday cups are not as sensitive as electron multiplier detectors, but are highly regarded for accuracy because of the direct relation between the measured current and number of ions . This device is considered a universal charge detector because of its independence from the energy, mass, chemistry, etc . of the analyte.
32.
Therefore the average velocity \ langle v _ i \ rangle of ions arriving into the Faraday cup and their average energy \ langle \ mathcal { E } _ i \ rangle can be calculated ( under the assumption that we operate with a single type of ion ) by the expressions
33.
Fig . 2 illustrates the I-V characteristic i _ i ( V ) and its first derivative i ^ \ prime _ i ( V ) of the Faraday cup with S _ F = 0.5 cm ^ 2 installed at output of the Inductively coupled plasma source powered with RF 13.56 MHz and operating at 6 mTorr of H2.
34.
The conventional Faraday cup is applied for measurements of ion ( or electron ) flows from plasma boundaries and comprises a metallic cylindrical receiver-cap 1 ( Fig . 1 ) closed with, and insulated from, a washer-type metallic electron-suppressor lid-2 provided with the round axial through enter-hollow of an aperture with a surface area S _ F = \ pi D ^ 2 _ F / 4.
