The system and method of controlling the speed of a variable gain system

A micro-channel plate (MCP) detector system (30) comprising a MCP detector, a data acquisition unit (20), wherein the detector comprises a first and a second MCP electron multiplier (12, 14), one or more anodes (16) connected to the data acquisition unit (20) and a gate electrode (32) disposed between the first and the second MCP electron multiplier (12, 14), wherein the detector system further comprises a data storage unit (36) and a gain control unit (34) which is connected to the gate electrode (32) and to the data storage unit (36), wherein a pilot spectrum is stored in the data storage unit (36), and wherein the gain control unit (34) is arranged to read the pilot spectrum from the data storage unit (36), and to control the potential on the gate electrode (32) as a function of m/z or time in response to said pilot spectrum, such that the transmission of electrons to the second MCP electron multiplier (14) is lowered when abundant protein ions appear, whereby a high sensitivity is maintained during the remainder of the measurement cycle such that neighboring peaks from rare protein ions become detectable.