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Title: Solid deposition in the ITER cryogenic viscous compressor

Authors:
; ;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1335176
Grant/Contract Number:
FG02-05ER54821
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Cryogenics
Additional Journal Information:
Journal Volume: 78; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-03 21:09:18; Journal ID: ISSN 0011-2275
Publisher:
Elsevier
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Zhang, Dongsheng, Miller, Franklin K., and Pfotenhauer, John M. Solid deposition in the ITER cryogenic viscous compressor. United Kingdom: N. p., 2016. Web. doi:10.1016/j.cryogenics.2016.05.006.
Zhang, Dongsheng, Miller, Franklin K., & Pfotenhauer, John M. Solid deposition in the ITER cryogenic viscous compressor. United Kingdom. doi:10.1016/j.cryogenics.2016.05.006.
Zhang, Dongsheng, Miller, Franklin K., and Pfotenhauer, John M. 2016. "Solid deposition in the ITER cryogenic viscous compressor". United Kingdom. doi:10.1016/j.cryogenics.2016.05.006.
@article{osti_1335176,
title = {Solid deposition in the ITER cryogenic viscous compressor},
author = {Zhang, Dongsheng and Miller, Franklin K. and Pfotenhauer, John M.},
abstractNote = {},
doi = {10.1016/j.cryogenics.2016.05.006},
journal = {Cryogenics},
number = C,
volume = 78,
place = {United Kingdom},
year = 2016,
month = 9
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.cryogenics.2016.05.006

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  • As part of the U.S. ITER contribution to the vacuum systems for the ITER fusion project, a cryogenic viscous compressor (CVC) is being designed and fabricated to cryopump hydrogenic gases in the torus and neutral beam exhaust streams and to regenerate the collected gases to controlled pressures such that they can be mechanically pumped with controlled flows to the tritium reprocessing facility. One critical element of the CVC design that required additional investigation was the determination of flow rates of the low pressure (up to 1000 Pa) exhaust stream that would allow for complete pumping of hydrogenic gases while permittingmore » trace levels of helium to pass through the CVC to be pumped by conventional vacuum pumps. A sub-scale prototype test facility was utilized to determine the effectiveness of a static mixer pump tube concept, which consisted of a series of rotated twisted elements brazed into a 2-mm thick, 5-cm diameter stainless steel tube. Cold helium gas flow provided by a dewar and helium transfer line was used to cool the exterior of the static mixer pump tube. Deuterium gas was mixed with helium gas through flow controllers at different concentrations while the composition of the exhaust gas was monitored with a Penning gauge and optical spectrometer to determine the effectiveness of the static mixer. It was found that with tube wall temperatures between 6 K and 9 K, the deuterium gas was completely cryopumped and only helium passed through the tube. These results have been used to design the cooling geometry and the static mixer pump tubes in the full-scale CVC prototype.« less
  • As part of the vacuum system for the ITER fusion project, a cryogenic viscouscompressor (CVC) is being developed to collect hydrogenic exhaust gases from the toruscryopumps and compress them to a high enough pressure by regeneration for pumping tothe tritium reprocessing facility. Helium impurities that are a byproduct of the fusionreactions pass through the CVC and are pumped by conventional vacuum pumps andexhausted to the atmosphere. Before the development of a full-scale CVC, a representative,small-scale test prototype was designed, fabricated, and tested. With cooling provided bycold helium gas, hydrogen gas was introduced into the central column of the test prototypepumpmore » at flow rates between 0.001 g/s and 0.008 g/s. Based on the temperatures and flowrates of the cold helium gas, different percentages of hydrogen gas were frozen to the column surface wall as the hydrogen gas flow rate increased. Results from the measured temperatures and pressures will form a benchmark that will be used to judge future heattransfer enhancements to the prototype CVC and to develop a computational fluid dynamicmodel that will help develop design parameters for the full-scale CVC.« less
  • The ITER vacuum system requires a roughing pump system that can pump the exhaust gas from the torus cryopumps to the tritium exhaust processing plant. The gas will have a high tritium content and therefore conventional vacuum pumps are not suitable. A pump called a cryogenic viscous compressor (CVC) is being designed for the roughing system to pump from ~500 Pa to 10 Pa at flow rates of 200 Pa-m3/ s. A unique feature of this pump is that is allows any helium in the gas to flow through the pump where it is sent to the detritiation system beforemore » exhausting to atmosphere. A small scale prototype of the CVC is being tested for heat transfer characteristics and compared to modeling results to ensure reliable operation of the full scale CVC. Keywords- ITER; vacuum; fuel cycle« less
  • As part of the U.S. ITER contribution to the vacuum systems for the ITER fusion project, a cryogenic viscous compressor (CVC) is being designed and fabricated to cryopump hydrogenic gases in the torus and neutral beam exhaust streams and to regenerate the collected gases to controlled pressures such that they can be mechanically pumped with controlled flows to the tritium reprocessing facility. One critical element of the CVC design that required additional investigation was the determination of flow rates of the low pressure (50 to 1000 Pa) exhaust stream that would allow for complete pumping of hydrogenic gases while permittingmore » trace levels of helium to pass through the CVC to be pumped by conventional vacuum pumps. A sub-scale prototype test facility was utilized to determine the effectiveness of a static mixer pump tube concept, which consisted of a series of rotated twisted elements brazed into a 2-mm thick, 5-cm diameter stainless steel tube. Cold helium gas flow provided by a dewar and helium transfer line was used to cool the exterior of the static mixer pump tube. Deuterium gas was mixed with helium gas through flow controllers at different concentrations while the composition of the exhaust gas was monitored with a Penning gauge and optical spectrometer to determine the effectiveness of the static mixer. It was found that with tube wall temperatures between 6 K and 9 K, the deuterium gas was completely cryopumped and only helium passed through the tube. These results have been used to design the cooling geometry and the static mixer pump tubes in the full-scale CVC prototype« less
  • Matrix isolation spectra have been obtained for ionic species formed from a beam of mass-selected ions, with a coincident beam of externally generated counter-ions used to provide charge balance. Infrared spectra were obtained for copper carbonyl complexes formed following deposition of Cu{sup −} ions with rare-gas counter-cations into CO-doped argon matrices. Both anionic and neutral copper carbonyl complexes Cu(CO){sub n}{sup q} (n = 1–3; q = 0, −1) were observed in the spectra, with peak positions corresponding to previously reported assignments; new partially resolved bands appearing in the range 1830–1845 cm{sup −1} are assigned to larger [Cu(CO){sub 3}•(CO){sub n}]{sup −}more » aggregates, having additional CO ligands in the second solvation shell. The experimental geometry ensures that all Cu-centers initially arrive at the matrix as anions, so the relative abundance of anionic relative to neutral complexes is much higher than in previous studies employing alternative methods for ion deposition; this allows for monitoring of electron-transfer processes between anions and cations in the matrix. Comparison of time-dependent vs. temperature-dependent trends reveals that there are two distinct mechanisms by which the population of anionic complexes is converted into neutral complexes: short-range electron transfer between a cation-anion pair following diffusion, and long-range electron transfer involving photodetachment of an electron from the anion into the conduction band of solid argon, resulting in eventual recombination of the electron with a cation in a remote matrix site. The spectra also show a marked dependence on the deposition temperature and dopant concentration, in that 100-fold higher CO concentrations were required during deposition with the sample window at 10 K compared to that used at 20 K, in order to obtain a similar distribution of copper carbonyl complexes. Furthermore, although no carbonyl complexes are observed initially when low concentrations of CO are used at 10 K, upon warming the matrix to 15 K, the neutral di- and tricarbonyl peaks appear abruptly, which is attributed to fast diffusion of CO stimulated by the energy released upon short-range electron-transfer between Cu{sup −}:counter-cation pairs.« less