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<b></b><big><big><b>JLab Liquid Nitrogen Thermo-siphon Design <br>
for NASA's Space Environment Simulation Lab</b></big></big><br>
<br>
Immediately followed by:<br>
<big><big><b>20 K Helium Refrigerator for NASA's <br>
Space Environment Simulation Lab</b></big></big><br>
<br>
<font color="#3333ff"><b>Tuesday, Sept. 18, 2012<br>
1:30 p.m. <font color="#cc0000">(Please note special time)</font><br>
CEBAF Center auditorium</b></font><br>
<br>
<big><b>Combined Abstract</b></big><br>
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. <br>
<br>
<b>Venkatarao "Rao" Ganni, Principal Staff Engineer, JLab Cryogenics
Group</b>, 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.<br>
<br>
<b>In the second colloquium, Pete Knudsen, Cryo Process Engineer,
JLab Cryogenics Group</b>, 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.<br>
---<br>
Complete abstracts are posted on the Jefferson Lab At A Glance
calendar at: <br>
<a class="moz-txt-link-freetext"
href="https://misportal.jlab.org/ul/calendar/calendar_date.cfm?date=18&month=9&year=2012">https://misportal.jlab.org/ul/calendar/calendar_date.cfm?date=18&month=9&year=2012</a><br>
---<br>
Regards,<br>
Deb Magaldi<br>
Jefferson Lab<br>
12000 Jefferson Ave.<br>
Newport News, VA 23606<br>
757-269-5102<br>
<br>
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