| CPC C01B 3/30 (2013.01) [B01J 23/755 (2013.01); C01B 3/56 (2013.01); C01B 32/162 (2017.08); H01J 49/067 (2013.01); H01J 49/105 (2013.01); H01J 49/24 (2013.01); C01B 2203/0277 (2013.01)] | 4 Claims |

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1. A method of operating a mass spectrometer vacuum interface:
wherein the vacuum interface comprises an evacuated expansion chamber situated downstream of a plasma ion source and upstream of a mass analyzer, the expansion chamber having a first aperture that interfaces with the plasma ion source to form an expanding plasma downstream of the first aperture and a second aperture, downstream of the first aperture from the plasma ion source and upstream of the mass analyzer, for skimming the expanding plasma to form a skimmed expanding plasma;
wherein the expansion chamber is pumped by an interface vacuum pump to provide an interface pressure in the expansion chamber, the interface vacuum pump is coupled to a controller, and the controller is coupled to a Visual Display Unit (VDU) upon which a graphical user interface (GUI), supporting a plurality of GUI modes, is displayed; and
the method comprises, by the controller:
receiving, via the GUI and a first input device, a selection of one or more operating conditions of the plasma ion source, wherein the selected one or more operating conditions of the plasma ion source comprise: electrical power supplied to the plasma ion source, a temperature of the plasma, or a plasma torch position;
dependent on the selected one or more operating conditions of the plasma ion source, automatically controlling a rotation speed of the interface vacuum pump to automatically maintain a predetermined value of the interface pressure between the first and second apertures of the expansion chamber;
initially displaying the automatically controlled rotation speed of the interface vacuum pump and/or the automatically maintained interface pressure on the GUI in a first GUI mode;
receiving input, via the GUI, to enter an override mode and set a particular rotation speed of the interface vacuum pump, provided via the GUI, and/or a particular interface pressure, provided via the GUI; and
in the override mode, displaying on the GUI the particular rotation speed of the interface vacuum pump as set and/or the particular interface pressure as set.
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