Fig. 4.

Mass spectrum of ¹⁸⁴W⁺ collected with and without stripping gas by scanning the SSAMS EPS across the slits (3 mm wide) between the magnet and ESA. A small leak of gas through the mass flow controller diaphragm causes a minor scattering tail at low energy for each peak. The peak shape without gas is flat-topped, even at low MRP. With gas, the peak is not perfectly flat topped, but the shape is stable for a specific gas flow rate, so this does not affect our precision or accuracy.