Vacuum Test Facility 1


Quick Facts:

  • 14-ft diameter by 22-ft long
  • Base Pressure: 10-7 Torr
  • Pumpdown Time (Atmospheric pressure to 10-6 Torr): 2 hours
  • Personnel entry door measuring 5-ft by 6-ft
  • Chamber penetrations for power, data acquisition, and high-pressure liquids and gases
  • 1-kW VWR Polyscience 1173-P Recirculating Chiller
  • Six 48-in diameter, Polycold-baffled, electrically heated, oil diffusion pumps (pumping speed – 600,000 l/s N2)
  • Chamber floor designed for a load of 2 tons
  • Large experiment assembly area
  • 30-ton capacity overhead crane
  • Cooling tower water to dissipate waste heat produced by Polycold compressors and vacuum pumps
  • Equipped to work with both flammable and toxic gases


The Vacuum Test Facility 1 is 7 meters long and 4 meters in diameter. This facility is designed to test high-power electric propulsion devices. It is the largest diffusion-pumped vacuum facility at any University in the nation. The chamber is evacuated by two 3800 CFM blowers and two 495 CFM rotary-vane pumps to moderate vacuum between 30mTorr and 100 mTorr. To reach high-vacuum (10-7 Torr), the chamber employs six NRC/Varian HS48-95,000 fractionating diffusion pumps, with a combined pumping speed of 600,000 l/s on air, 840,000 l/s on Hydrogen, and 155,000 l/s on Xenon. Two internal linear tables and one rotary table are robust enough to investigate plume and discharge chamber characteristics in devices of up to 100 kg. The thrust stand is a duplicate of the proven null-type inverted-pendulum thrust stand used to test high-power Hall thrusters (NASA-457M) at the NASA Glenn Research Center. The thrust stand is actively cooled by a VWR Polyscience 1173-P recirculating chiller. The facility can be configured to accommodate a wide variety of vacuum experiments.

There is great interest in operating high-power thrusters on hydrogen and other light gases. Diffusion pumps are the best candidate for pumping large mass flow rates of light gases. The VTF-1 has one the highest pumping speeds of any diffusion-pumped facility in the nation. Thus, the use of the VTF-1 is critical if the nation is going to evaluate high-power light-gas thruster operation in a high-capacity vacuum facility in the near future.

Turbo Pump:

The VTF-1 is also equipped with a turbo pump package to allow testing of more chemically active propellants that are incompatible with diffusion pump operation. The pump is an Edwards STP-XA3203 turbomolecular pump with a pumping speed of 3200 l/s (on N2). The XA3203 is backed by an Edwards GV80 dry scroll pump with a maximum pumping speed of 64.6 cfm.

Gas Feed System:

The gas supply storage area is located on the outside of the building, and is comprised of two ventilated bottle enclosures.  The flammable gas enclosure has a capacity of storing up to 1800 cubic feet of flammable gases; the toxic gas enclosure can store up to 300 cubic feet of both toxic and flammable gases.


The flammable and toxic gas feed lines, which can be heated for specific gas conditioning requirements, run into the lab and enter a stainless steel ATEX-rated purge enclosure.  The enclosure is designed to be continuously purged with a low-pressure nitrogen flow, which is ventilated through the facility exhaust.  Two MKS P9B multi-range/multi-gas mass flow controllers (MFCs) reside inside the purge enclosure, allowing for high precision control and/or mixing of the supply gases prior to feeding into the chamber.  The enclosure, measuring 30”x20”x8”, provides ample volume for any additional custom plumbing or gas conditioning needs.

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