Usually I run it around 10 ^-4 torr on heads, you need to work off the volitiles with seporate pump. Once you can pull your shortpath down to around .75 torr you can start backing and heating your diffusion pump, once your diff pump is running you can slowly valve the low side vaccum off and throttle on to the diffusion pump/backing pump.
Once your distillation is complete you valve off the high vaccum side and back on to the rough pump.
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