Using the Pfeifffer Vacuum Calculator, I am evaluating what pump can handle the entire 0.5 m GQuEST Vacuum Setup.
Parameters:
Calculated volume: 0.145 m³
Calculated surface: 2.6 m²
Desorption rate: 1e-9 mbar*l/(s*cm²)
Leak rate: 3e-9 mbar*l/s
Using a 6 m3/s scroll through a 1 m, 50 mm diameter tube, it should only take ~7 minutes to reach 1 Torr.
Using a 300 L/s turbo through a DN 100 connected directly to the source, it will take around 30 hours to reach 10-8 Torr.
Using a 80 L/s turbo through a DN 63 connected directly to the source, it will take 4 days to reach 10-8 Torr.
Unless the 300 L/s turbo were prohibitively expensive, I would therefore advocate for a 6 m3/s scroll and a 300 L/s turbo.