Sept. 18 Colloquia: Major JLab Cryogenics Advancements Being Used by NASA

Tuesday, Sept. 18, 2012
1:30 p.m. (Please note special time)
CEBAF Center auditorium

JLab Liquid Nitrogen Thermo-siphon Design for NASA's Space Environment Simulation Lab
Immediately followed by:
20 K Helium Refrigerator for NASA's Space Environment Simulation Lab

Combined Abstract
In 2006, NASA's Johnson Space Center requested technical assistance from the JLab Cryogenics Group for the process design, development of specifications and construction of a new 20 K helium refrigerator necessary for ground testing the James Webb Space Telescope (JWST) in Chamber A of NASA's Space Environment Simulation Lab (SESL). SESL simulates a deep-space environment necessary for ground testing critical spacecraft including the JWST.

Venkatarao "Rao" Ganni, Principal Staff Engineer, JLab Cryogenics Group, will present the first colloquium, which will cover JLab's work on SESL's Chamber A 80 K liquid nitrogen (LN) system needed to shield the 20 K helium cryopanels that provide a simulated deep-space environment necessary to perform ground testing of the JWST. The original system was a forced flow LN system that was not reliable due to heavy use of pumps and components. After determining that refurbishment was cost prohibitive, NASA asked JLab for options. JLab proposed a thermo-siphon, or natural flow, system that eliminated the need for pumps and used a factor of 10 fewer valves. Recent commissioning results indicate that the new thermo-siphon system exceeded the (predicted) design goals and far surpassed the performance of the original force flow system. This talk will outline the thermodynamic-process comparison between the two designs, as well as the commissioning results of the thermo-siphon system.

In the second colloquium, Pete Knudsen, Cryo Process Engineer, JLab Cryogenics Group, will outline the JLab process design work and commissioning results of SESL's 20 K Helium Refrigerator. JWST testing requirements demanded that the refrigerator be capable of 12.5 kW at 20 K, 100 kW at 100 K and a temperature stability of ±0.25 K during steady state operating conditions. Recent commissioning results indicate an unprecedented load temperature range, load turn-down capability and temperature stability. All of these exceed the design goals, including the cool-down and transition time between load temperatures and will contribute to important and significant project cost savings for NASA. These colloquia will present critical Jefferson Lab cyrogenics advancements that are being integrated with industry to help support U.S. scientific needs.

Posted Sept. 11, 2012

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