Overview
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detector, creating a current. This current is then sent to the preamplifier for ampli-
fication and then to the data system for display.
When an electron multiplier is used, the ions are attracted to the multiplier be-
cause of its negative charge. As the ions strike the multiplier, secondary electrons
are emitted. This creates a cascading effect as each secondary electron generates
more secondary electrons as they move down the multiplier wall, amplifying the
signal by approximately one thousand.
The Dycor system uses a microchannel plate (MCP) electron multiplier. It con-
sists of an array of millions of small glass capillaries fused together in the shape
of a disk. The inside wall of each channel has a resistive, electrically semi-con-
ductive layer, forming independent electron multipliers. As the ions are approach-
ing the MCP, a positive electrical gradient pulls the electrons into the MCP.
As they cascade down and strike the channel walls, they generate secondary
electrons. The Dycor MCP has the advantage in that it is stable and is especially
beneficial for detection of low-level species.
Data System
Overall control of the system, acquisition of data, and access to collected data
is accomplished through the Dycor Process 2000 software. Adjustment of all
instrument parameters that affect sampling, ionization, separation and detection
are software controlled. All data acquisition parameters are also set using the
software.
