Dongsheng Zhang

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Dongsheng Zhang Ph.D. Graduate Student Mechanical
Engineering Room 1327 ERB dzhang25_at_wisc.edu HOME
TOWN Hualin, China

• Thesis Model and test features of the cryopump
  being designed for use in ITER

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Background

• The project is to model and test features of
  the cryopump being designed for use in ITER.
  After the fusion reaction in ITER, a mixture of
  hydrogen isotopes and helium flow through the
  cryopump. The gas mixture enters the pump at 80
  K, while the walls of the cryopump are maintained
  at 4 K. At such low temperatures, hydrogen
  isotopes can be adsorbed on the pump surface,
  while helium atoms just flow through the pump. As
  a result, a separation of the hydrogen isotopes
  and helium is achieved.

Figure 1 ITER in South of France
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Objectives

• The research goal is to understand the energy
  load, mass transfer rate, and pumping capacity,
  etc. The project is interdisciplinary, and
  touches areas such as surface chemistry, physics,
  and cryogenics, in addition to mechanical
  engineering.

H2 (D2) molecules are adsorbed on pump surface
H2 (D2) density decreases because of
chemisorption and physisorption effect
Figure 2 mixture of H2 (D2) and He flowing
through a cryopump
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Molecule-surface interaction

• The figure below shows molecule surface
  interaction and energy transferred.
• E1 S (Ek Eint e - kTs) S
  is sticking coefficient
• E2 Esub Esub is sublimation
  energy
• E3 a (Ek 2kTs Eint) a
  (T - Tf) / (T - Ts)
• E4 a (Ek 2kTs Eint)He

Figure 3 H2 (D2) and He impinge on pump surface
and energy is transferred