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SEQUENCE:0
UID:UW-Physics-Event-4825
DTSTART:20180420T223000Z
DURATION:PT1H0M0S
DTSTAMP:20260414T234054Z
LAST-MODIFIED:20180416T191326Z
LOCATION:2241 Chamberlin Hall
SUMMARY:Downstream hydrogen plasma cleaning for mass metrology at NIST
 \, JIMFEST 2018\, Eric Benck\, National Institute of Standards and Tec
 hnology
DESCRIPTION:On International Metrology Day\, May 20\, 2019\, the redef
 inition of the International System of Units (SI) is scheduled to be i
 mplemented. When this occurs the kilogram\, the last remaining unit de
 fined by a physical artifact\, will be redefined to be based on a fund
 amental physical constant\, the Planck constant.   As a consequence\, 
 the NIST mise en pratique\, a series of steps for the realization and 
 dissemination of the revised definition of the kilogram\, must be sign
 ificantly modified.  In particular\, the mise en pratique will need to
  address for the first time the measurement and handling of masses in 
 a vacuum. At NIST this will includes 5 major components: NIST-4 Kibble
  Balance\, Magnetic Suspension Mass Comparator (MSMC)\, Mass-in-Vacuum
  Comparator\, storage chambers\, and mass transport vehicles (MTV).  I
 n addition to these components\, there also is a need to develop new p
 rocedures to maintain and clean masses in vacuum.  Over long periods o
 f time masses can become coated with a carbon containing contamination
  layer\, even while stored in a vacuum. A downstream hydrogen plasma s
 ource is being investigated as a means of gently removing these carbon
 aceous layers. Atomic hydrogen can react with carbon on the mass surfa
 ce and convert it to volatile hydrocarbons which can then be pumped ou
 t of the system.  Initial results demonstrating the etching of carbon 
 coatings off a quartz crystal microbalance (QCM) in our downstream hyd
 rogen plasma cleaner will be presented. 
URL:https://www.physics.wisc.edu/events/?id=4825
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