Development of a method for liquid xenon purification using a cryogenic centrifugal pump

doi:10.1016/j.cryogenics.2006.04.003

Cryogenics

Volume 46, Issue 9, September 2006, Pages 688-693

https://doi.org/10.1016/j.cryogenics.2006.04.003 Get rights and content

Abstract

We are developing a new type of photon detector for an experiment to search for muons decaying into a positron and a gamma ray. In this experiment, the photon detector will utilize liquid xenon (Xe) as the scintillation material. Good transparency of the liquid Xe is required in order to gain the highest performance out of the detector. Impurities like water and oxygen must be removed efficiently for this purpose. We have developed a new purification system, dedicated to removing water from liquid Xe, by employing a cryogenic centrifugal pump and molecular sieves. The performance of the system is described in this article.

Introduction

Our group is developing a gamma-ray detector outlining liquid Xe as a scintillation material. This detector is planned to be used in a muon rare decay search experiment (MEG).

We built a prototype with 100-l volume to execute various developments, and have performed basic studies necessary for the construction and operation of the actual detector with 800-l liquid Xe [1]. We have proved in these studies that there is no difficulty for performing long-term stable operation of the detector as large as the actual one.

One of the most important results in these studies is that it is indispensable to remove remaining water in the liquid for obtaining the highest performance out of the detector [1]. Recently, we have developed a new purification system using a cryogenic centrifugal pump with superior performance, and executed a test for evaluating its performance [2]. In this article we introduce this new purification system and report on its performance.

Section snippets

Purpose of the test

The experiment, MEG, is searching for muons decaying into a positron and a gamma ray (μ → eγ decay) at Paul Scherrer Institute in Switzerland, where the most intense muon beam in the world is available [3]. The μ → eγ decay is suggested to exist by various theoretical models that incorporate new physics beyond the standard model of the elementary particle physics, and there is a high possibility that decay will be observed in this experiment.

In the MEG experiment, a gamma-ray detector with 800-l

Liquid xenon purification system

It was figured out during our study of the gas-phase purification that the main component contributing to scintillation light absorption was water. This is because the light absorption cross section of water is largest around the wavelength region of the Xe scintillation light. In addition, because we cannot heat the detector while evacuating the cryostat due to photomultipliers placed inside, water can easily stay and exude into the liquid after liquefaction. For this reason, we designed the

Procedure

A purification test was performed in the following way. First the molecular sieves were regenerated in parallel with evacuation of the cryostat. The purifier cartridge was heated up to 250 °C and continuously evacuated for 4 h. Normal air (15 °C, 20% humidity) was fed in the cryostat afterward in order to artificially introduce water inside the detector, and then the cryostat was evacuated again. The liquid-nitrogen cooling pipe was cooled during the second and later evacuation for keeping water

Conclusion

We have developed a new purification method for liquid Xe using a cryogenic pump. We adopted a fluid pump with a flow rate of 100 l/h and molecular sieves as a water absorber, and successfully reduced the impurity concentration from 250 ppb to 40 ppb in 100 l of liquid Xe within 5 h. This is an adequate performance for the MEG photon detector as well as others using liquid-Xe scintillation light from the view points of the purification time and purity level.

Construction of the MEG liquid Xe photon

Acknowledgements

We wish to thank many people for their suggestions and support, especially Dr. Schinzel of CERN, who suggested that we use a cryogenic fluid pump at an early stage of our development. We appreciate valuable support of the cryogenic group in Paul Scherrer Institute. We thank collaborators of the MEG experiment and the cryogenics group in IPNS, KEK for indispensable support to perform our test. This work has been supported by a Grant-in aid for Scientific Research from the Ministry of Education,

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¹: Present address: Paul Scherrer Institute, Villigen, Switzerland.

²: Present address: University of California, Irvine, USA.

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Development of a method for liquid xenon purification using a cryogenic centrifugal pump

Abstract

Introduction

Section snippets

Purpose of the test

Liquid xenon purification system

Procedure

Conclusion

Acknowledgements

Development of a liquid xenon photon detector

TEION KOGAKU

Study on LXe system for particle detector (12) – Liquid xenon purification by using a liquid circulation pump for the MEG experiment

Abstracts of CSJ Conf

Development of a high-power coaxial pulse-tube refrigerator for a liquid xenon calorimeter

Adv Cryog Eng