HP 5973 Hardware Manual page 184

Vacuum System
The vacuum system is essential to MSD operation
The vacuum system creates the high vacuum (low pressure) required for
the MSD to operate. Without the vacuum, the molecular mean free path
would be too short. Ions would collide with air molecules before they could
reach the detector. Operation at high pressures would damage analyzer
components.
The HP 5973 MSD has one of two kinds of vacuum system: diffusion pump
(HP G1098A) or turbomolecular (turbo) pump (HP G1099A). Many parts
of the vacuum system are common to both, but some parts are specific to
the one high vacuum pump or the other.
Many components make up the vacuum system
Many parts make up the vacuum system:
• Vacuum manifold
• Side plate, and front and rear end plates
• Vacuum seals
• Foreline (rough) pump
• High vacuum pump
• Calibration valve and vent valve
• Vacuum control electronics
• Vacuum gauges and gauge control electronics
Each of these is discussed in more detail in the following material.
Vacuum system control is mostly automated
Most vacuum system operation is automated. Operator interaction is
through the data system. Monitoring of the vacuum system is done through
the data system and through the optional gauge controller.
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