High Vacuum Facility

Faculty: Profs. Alina Alexeenko and Steve Heister

Laboratory Manager: Dr. Anthony Cofer Graduate Students: Andrew Strongrich, Kate Fowee and Gayathri Shivkumar

Chamber A

The centerpiece of the high vacuum facility is the large vacuum chamber, constructed of cast aluminum. The chamber is 5 feet in diameter by 7 feet long (4.2 m³).

Chamber A is evacuated by two mechanical pumps

a two-stage positive displacement pump with a max pump speed of 150 ft³/min and blower 400 ft³/min for medium vacuum to ~1 milliTorr
a high-throughput Varian HS-20 diffusion pump with a pump speed of 17000 ft³/min for high vacuum down to 1 microTorr.

Chamber A at ASL was designed and built in academic year 2007-2008 by Prof. Ivana Hrbud and her students.

The new mechanical pump Oerlikon DK200/WAU 2001 was installed in 2013.

Chamber A is evacuated to a pressure of 1 Pa (0.001% of atm) in less than 20 mins and to an ultimate pressure of about 1 mPa (100,000,000 times less than 1 atm) in about 1 hour.

(top) Chamber A with VarianHS-20 diffusion pump to the left; (bottom) OerlikonDK200 roughing pump with blower

Pumping speed (left) and pumpdown curve (right) for chamber A

Chamber A MicroNewton Thrust Stand

The microNewton thrust stand system is a torsional pendulum type incorporating an electrostatic fin assembly for calibration, top and bottom pivot bearings for motion control, and linear variable differential transformer for deflection measurement. The thrust stand is mounted in the large vacuum chamberas shown in Figure 2. It has been used for thrust measurements of small cold gas microthrusters and force measurements of the Knudsen force effect. The electrostatic fin assembly produces forces, with repeatable within 3.6% at 9 microNewtons and less than 0.5% at 764 microNewtons.

Micronewton Thrust Stand was built in 2011 by Tony Cofer based on a design by Dr. Andrew Ketsdever and his colleagues at UCCS.

MicroNewton thrust stand in HVF Chamber A

Chamber B

The acrylic chamber is 1 foot diameter by 1 foot tall and evacuated by an Alcatel 2008A two-stage rotary vane pump (150 ft³/min) which has reached a minimum pressure of 5 milliTorr. It has been used in radiometer experiments and for medium vacuum testing of components prior to use in the large chamber.

Feedthroughs provide access for power, gas, and thermocouples within the chamber.

The chamber was designed and build by Di Huang and Dr. Anthony Cofer as part of an undergraduate research project.

Acrylic Chamber B in HVL.

Chamber C

The stainless steel benchtop vacuum chamber has an internal volume of 8.3 in³, providing in-situ micrometrology in vacuum for MEMS devices. The system is driven by an Inest-Iwata dry scroll pump, supporting ultimate pressures in an ultra-clean environment of ~10 mTorr. Equipped with pressure and temperature sensors and various electrical and gas feedthroughs. The chamber lid has a central viewport that supports windows needed for optical, infrared, and confocal microscopy under controlled vacuum environment.

The chamber was designed and built in 2014 by Alix Crandell and Drew Strongrich as part of an undergraduate research project supported by NSF.

(top) Portable benchtop Chamber C in Bay J of Birck Nanotechnology Center; (bottom) Chamber C installed under Professor Marconnet's (Purdue ME) QFI infrared microscope.

List of Available Equipment at the High Vacuum Laboratory:

Chambers A, B, and C with supporting pumps (see above)
Micronewton torsional balance (see above)
Soldering and electronics fabrication station
Various multimeters, oscilloscopes, power supplies, and waveform generators
Bottled ultra-pure Ar, N₂, He, and O₂ gases
Full range of pressure transducers
- Capacitance diaphragm gauges (0.1 Torr to 1000 Torr full scale)
- Piezo gauge
- Convection gauges
- Ion gauges
National Instruments data acquisition hardware
- PCI-6229 and PCI-6110
- USB-9162
- USB-6008
Residual gas analyzer (mass spectrometer)
Positive pressure clean box for sample storage

Former Undergraduate Interns: Di Huang, Kaizad Raimalwala, Bill O'Neill, Sagar Unadkat, Mike King, Andrew Cox, Drew Strongrich, Alix Crandell, Hani Kim, Dongju Lee, Kate Fowee, Nolan John, Lev Zemlyanov

Publications and Presentations from High Vacuum Facility:

A. Cofer, W. O'Neill, S. Heister, A. Alexeenko, and E. Cardiff, "Film-evaporation microthruster for cubesats." 2016 IEEE 29th International Conference on Micro Electro Mechanical Systems (MEMS), pp. 1248-1251, 2016.
A. Cofer, W. O'Neill, S. Heister, A. Alexeenko, and E. Cardiff, "Film-Evaporation MEMS Tunable Array for Low-Mass SmallSat Propulsion: Design Improvements and Thrust Characterization.", AIAA Paper 2015-3993, 51st AIAA/SAE/ASEE Joint Propulsion Conference, p. 3993. 2015.
Strongrich, A., Alexeenko, A., “Convective Cooling in the Transitional Rarefied Flow Regime,” International Mechanical Engineering Congress & Exposition, Montreal, Canada, 2014.
Strongrich, A., Alexeenko, A., “Knudsen Thermal Force Generation at the Microscale,” International Mechanical Engineering Congress & Exposition, Montreal, Canada, 2014.
Strongrich, A., Alexeenko, A.*, “Experimental Measurements and Modeling of Convective Cooling in the Transitional Rarefied Regime,” 29th International Symposium on Rarefied Gas Dynamics, Xi’an, China, 2014.
O’Neill W., Wada, M., Strongrich, A., Cofer, A., Alexeenko, A.*, “Amplification and Reversal of Knudsen Force by Thermoelectric Heating,” 29th International Symposium on Rarefied Gas Dynamics, Xi’an, China, 2014.
Strongrich, A., Cofer, A., O’Neill, W., Alexeenko, A., “Experimental Measurements and Numerical Simulations of Knudsen Force on a Non-Uniformly Heated Beam,” Vacuum, Special Issue, 2014.
A. Cofer, W. O'Neill, S. Heister, A. Alexeenko, and E. Cardiff, “Film-Evaporation MEMS Tunable Array: Theory of Operation and Proof of Concept", AIAA Paper 2014-3855, 50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference (2014)
A. Cofer, S. Heister, and A. Alexeenko, “Improved Design and Characterization of MicroNew-ton Torsional Balance Thrust Stand”, AIAA Paper 2013-3856, 49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, San Jose, CA, 14-17 July 2013.
A. Cofer, A. Venkattraman, and A. Alexeenko, “Micro-Spike based Hybrid Chemical/Electric Thruster Concept for Versatile Nanosat Propulsion”, AIAA Paper 2011-5921, 47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, San Diego, CA, July 31 – August 03, 2011.

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