| 摘要 |
In order to effect fragmentation of ions through collisions with gas-phase molecules, it is necessary to have a high gas pressure in the collision region. At the same time the residual gas pressure in the detector region of a mass-spectrometer must be kept low. This is done by arranging collision cell and detector into separately pumped vacuum regions, each region having its own pumping port, the regions only being connected via flow restrictions in the vicinity of the ion optical axis. Achieving large pressure gradients and at the same time not reducing the sensitivity of the mass spectrometer can be done by using gas flow restrictions with large cross sections. A very efficient and space saving arrangment is to place a separate chamber with the collision cell between the chamber housing the reflector and the detector and the chamber housing the ion source of the mass spectrometer.
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