Measures of solid hydrogen contamination problem in the liquid helium 6th International Workshop on Cryogenics Operations on 10-12 November 2014 Measures of solid hydrogen contamination problem in the liquid helium Hiroshi Ikedaa,*, Yutaka. Kondo a Research Facility Center for Science and Technology Cryogenics Division, University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan

CONTENT Introduction History of L280 in University of Tsukuba The trouble with solid hydrogen Purity measurement and state understanding of internal purifier (New method !) Improving method the purity of the regeneration gas Gas chromatograph mass spectrometer impurity analysis of helium liquefaction machine Consideration of decreased purity (Changes in Linde helium Liqufier） Conclusions

Introduction ・In recent years, several universities that renewed their helium liquefier system have reported that solid hydrogen was mixed within the liquid helium produced by a helium liquefier. ・The University of Tsukuba has also installed a Linde L280 helium liquefier system in October 2010. Similar to other universities, cases where the helium flow of cryogenic equipment with flow impedance was blocked began to be reported around March 2012. ・In this work we focused on the internal purifier of the helium liquefier for the problem where solid hydrogen is mixed in the liquid helium produced by a helium liquefier.

History of L280 in University of Tsukuba

Decreased purity of helium recovery gas bag About 1 year passed Decreased purity of helium recovery gas bag

helium liquefier flow ( L280）

Internal purifier Flow Gasbag PV3415 CV3401 　V3410 CV3430 CV3420 Flow Meter Cold Gas Line Impurer Helium Gas Atmospheric release PV3435 TI3475 TI3465 Heater PI3401 PI3445 HP Line LP Line Liqide Air CV3410

Decreased purity of helium recovery gas bag ⇒　95％　（Nomalｙ＝99％） Differential pressure occurs when introduced into the internal purifier gas was decreased purity

Trend graph of the differential pressure occurs ΔP＝0.15MPa Cool down Mode Regeneration Mode Purify Mode Buffer tank

The trouble with solid hydrogen

The trouble with solid hydrogen Flow impedance blocked by solid hydrogen Quantum Design MPMS PPMS (equipment to control temperature while limiting the flow of helium by a filter and capillary)

Trouble Instrument Worldwide！ Japan Korea China India Spain France Germany Worldwide！

Purity measurement and state understanding of internal purifier New method！

Gas bag purity is reduced to 95% by the regeneration gas, introduction into the internal purifier, differential pressure occurs. ‣ For gas purity measurement discharged from the internal purifier was installed simple helium purity monitor immediately after the flow meter.

Simple purity monitor installation flow diagram Gas Bag CV3415 CV3401 V3410 CV3430 CV3420 Flow Meter Cold Gas Flow Impurer Helium Gas CV3435 TI3475 TI3465 Heater PI3401 PI3445 HP Line LP Line Liqid Air １００％ Purity Monter CV3410 Atmospheric release

Simple helium gas purity monitor New Method！ Ulvac WP-01 Pirany type　SKD-20

A result of the purity measurement The purity of the regeneration gas was reduced to 33% at maximum Initial setting valu ・Purification operation state Cold end temperature TI3475　　 　=　32.5 K Internal pressure PI3445　　　 =　2.5 MPa ・ Regeneration during operation　 　　 Exit flow meter flow rate 　 =　120 L/min 　　 Regeneration completion temperature TI3465 =　140 K 　　 Heater control temperature TI3475 =　95 K 　　 Warming heater output R3470 = 18 ％

Improving method the purity 　of the regeneration gas

Comparison with the liquefier Internal purifier Cold end temperature Internal purifier Exit flow rate TCF50 L280 ２７．５ K ２００ L/min ３２．５ K １２０ L/min High temperature!　　　　　　　　 Low flow rate!

Setting changes 120L/min⇒190L/min CV3415 CV3401 V3410 CV3430 CV3420 Down fromD32.5K Gas Bag CV3415 CV3401 V3410 CV3430 CV3420 Flow Meter Cold Gas Flow Impurer Helium Gas CV3435 TI3475 TI3465 Heater PI3401 PI3445 HP Line LP Line Liqid Air １００％ Purity Monter CV3410 Atmospheric release

Internal purifier regeneration gas purity measurement results 32.5K 120L/min

Internal purifier regeneration gas purity measurement results 29.0K 190L/min 26.0K 190L/min 32.5K 120L/min

Trend graph of the regeneration gas purity after improvement 26.0K 190L/min ΔP＝0.039MPa

Befer　　　　　　　　　　　　　After ΔP＝0.15MPa ΔP＝0.039MPa 32.5K、120L/min 26.0K、190L/min

Gas chromatograph mass spectrometer impurity analysis　of helium liquefaction machine

Gas chromatograph mass spectrometer SHIMADZU GC-2014 O

Gas chromatograph mass spectrometer impurity analysis　of helium liquefaction machine

Improvement result The purity of the regeneration gas, 33% ⇒ 99% Cold end temperature change, the regeneration gas flow rate increase　　　　　　　　　　 　The purity of the regeneration gas, 33% ⇒ 99% Pressure difference is reduced. Purification operation has stabilized

Consideration of decreased purity (Changes in Linde helium Liqufier）

1996 TCF50 Flow diagrams Adosorber 3 point ! 80K 20K LHe GHe LN2 Gas Bag InPur GHe Adosorber 3 point !

2010 L280 Flow diagrams Adsober Only One 20K LN2 LHe GHe Gas Bag InPur GHe Gas Bag

2014 L140 New Flow diagrams Adosober Revival ! 20K LN2 LHe GHe Gas Bag InPur GHe

Conclusions Regeneration gas purity was improved from 33% to　99% by the setting change of internal purifier. Purification operation has stabilized generation of the differential pressure is reduced. By monitoring established the purity helium simple monitor, it can insight into the operating state of the internal purifier at a low cost. As the cause of differential pressure and decreased purity of the regeneration gas occurred, in addition to the incorrect setting, it is considered as the cause did not have the adsorber inside purifier.

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