Fig. 4. Sketch of the vacuum system (upper) and its corresponding
position in a schematic of API-MRTOF-MS (lower); the dotted and dashed
rectangular frames with different colors indicate the four main chambers
of the instrument: (1) MIR
chamber, (2) RFQs and FLT chambers, (3) ST and DT chambers, (4) MRTOF
analyzer chamber. Differential pumping stages and pressure in each
compartment are present. The aperture diameters are presented in mm.
The API-MRTOF-MS apparatus is in the
shape of the letter āLā with a length of 2230 mm, coupled with ESI
ionization on the left. Each chamber contains electrical feedthroughs,
most of which are multi-feedthroughs, except those for the ultrahigh
voltage supplies. Heating plaster
containing the silicone heating sheet inside is utilized to cover both
sides of the MRTOF analyzer chamber, which can maintain a maximum
chamber temperature of 80 ā to obtain a better vacuum. Table 1 lists the
pressure of each chamber marked in Fig. 4, along with the pumping speed
of the used pump. All turbo pumps are backed up by a 6 L/s roots pump
(NeoDry 30E, Kashiyama).
Table 1 Chamber pressure with and without load