IV. OPERATION RECORDS

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Present status of liquid-helium supply and recovery system
T. Dantsuka,∗1 H. Okuno,∗1 M. Nakamura,∗1 S. Tsuruma,∗1 M. Takahashi,∗1 M. Kuroiwa,∗1 M. Ohshima,∗2H. Miura,∗2 H. Shiraki,∗2 H. Hirai,∗2 K. Kimura,∗2 M. Haneda,∗2 A. Mikami,∗2 M. Nagano,∗2 and H. Hazama∗2The liquid-helium supply and recovery system,1)
which can produce liquid helium at a liquefaction rateof 200 L/h from pure helium gas, has been under stable
operation since the beginning of April 2001. However,as operation failure due to deterioration over time hasincreased in recent years, duplication of the liqueﬁer
was conducted in 2017. The new liqueﬁer can produce
liquid helium at a liquefaction rate of 220 L/h frompure helium gas. Although the older helium liqueﬁer
has been failing since the summer of 2018, with thenew helium liqueﬁer, a constant supply of liquid helium can be enabled. The older helium liqueﬁer wasrepaired in February 2020.
The volumes of liquid helium supplied each year
from 2001 to 2019 are illustrated in Fig. 1. From 2001
to 2013, there was a gradual increase in the supplied
volume, with two declines observed in 2009 and 2011.
In 2014, the supplied volume decreased owing to a system malfunction. However, in 2015, the supplied volume returned to its original value. In 2016, the supplied volume decreased but slightly increased in 2017.
In 2018, the supply volume increased signiﬁcantly. In
2019, we supplied approximately 140,000 L of liquid
200000180000160000Liquid Helium (L)140000120000100000helium despite the high price of helium gas.
However, the purity of helium gas recovered fromthe laboratories gradually deteriorated. At present,
the impurity concentration in the recovered gas is approximately 1000 ppm. The impurity concentration
does not aﬀect the liquefaction operation, but is necessary to observe the progress.
Furthermore, the volume of helium gas recoveredfrom each building in the Wako campus as well as thevolume transported to the liquid helium supply and recovery system were measured. The recovery eﬃciency,
which is deﬁned as the ratio of the amount of recovered
helium gas to the amount of supplied liquid helium,
was calculated. The recovery eﬃciency for the buildings on the south side of the Wako campus, namely theCooperation Center building of the Advanced DeviceLaboratory, Chemistry and Material Physics building,and Nanoscience Joint Laboratory building, increased
to approximately 95%.
Reference

1) K. Ikegami et al., RIKEN Accel. Prog. Rep. 34, 349(2001).

Magne�c Materials Laboratory
Low Temperature Physics Laboratory
Advanced Device Laboratory
Condensed Molecular Materials Laboratory
Molecular Characteriza�on Team
Surface and Interface Science Laboratory
Surface Chemistry Laboratory
Radioac�ve IsotopePhysics Laboratory
Exploratory Materials Team
Quantum Func�onal System Research Group
Emergent Phenomena Measurement Research Team
Other laboratories

80000
60000
40000
20000
0

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

Fiscal Year
Fig. 1.
∗1∗2

Volumes of liquid helium supplied to the various laboratories for each fiscal year from 2001 to 2019.

RIKEN Nishina Center
Nippon Air Conditioning Service K.K- 186 -1