I have already repeated Jeri Ellsworth DIY NMOS transistor experiment. A lot of the pictures and components listed in this project are from that experiment.
The next step is getting a working vacuum system. The relevant hardware I was able to salvage from the QSTAR XL tandem mass spectrometer is (1) a Varian DS 602 2-stage rotary vane pump (2) three Leybold turbomolecular pumps (3) two vacuum pressure gauges and their controller (4) anode, cathode, grind, etc. integrated power supply.
Currently, I'm trying to get the Varian DS 602 vacuum pump working. When I received it, it was running very hot and blowing a 20A breaker after a few seconds. I disassembled the actual pump portion and found nothing wrong at all. Then I tested the motor. There are no visible issues with the motor but it runs unreliably. It is a somewhat unusual and complicated design (dual-voltage capacitor-start capacitor-run squirrel cage induction motor with starter relay) and I have not been able to find the schematics. I drew out the schematic of the external wiring and recorded the resistances between the coil wires. From there, I inferred the connections inside the windings. Now I have disassembled the motor several times and tried various things (detailed in the spreadsheet attached) to identify the problem winding, but with little luck so far. I am also shopping around for potential replacement motors at surplus stores.
Once the vacuum pump is back online, the next step will be to check the turbomolecular pumps. I have already contacted some companies for help with that step, and I am in the process of designing an Arduino sketch to control the pump frequency converters.
Then I will build the main vacuum chamber with electrical feedthroughs, view ports, venting inlets, and vacuum gauges. After all of that works, I am ready to build the ion implanter!