Few things may help;

1. 5N purity source - need additional care during handling

2. wiping out the surface after every evaporation cycle

3. adding tantalum wire at smaller quantities

Spitting may due to sudden ramp in applying power and/or cooling channels. I don't think carbon causes spitting. When i was trying to deposit nickel using E-Beam, i was facing spitting for few runs. later i did evaporation without spitting and i am doing it now a days .

Try this, apply power very slowly and make Au melt pool, then steadily increase the power to achieve your desired evaporation rate. once Au melt pool forms don't switch the beam location. that may cause spitting.

i hope this helps.