Magnetically-coupled piston pump for high-purity gas applications

E Brown,H.-W Ortjohann,A Fieguth,C Huhmann,D Tosi,D Schulte,A Schubert,M Murra,G Gratta,S Rosendahl,A Buss,C Weinheimer

doi:10.1140/epjc/s10052-018-6062-z

E Brown, H.-W Ortjohann + Show 10 more

Open Access

https://doi.org/10.1140/epjc/s10052-018-6062-z

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Abstract

Experiments based on noble elements such as gaseous or liquid argon or xenon utilize the ionization and scintillation properties of the target materials to detect radiation-induced recoils. A requirement for high light and charge yields is to reduce electronegative impurities well below the ppb (parts per billion, 1 ppb =1times 10^{-9} mol/mol) level. To achieve this, the target material is continuously circulated in the gas phase through a purifier and returned to the detector. Additionally, the low backgrounds necessary dictate low-Rn-emanation rates from all components that contact the gas. Since commercial pumps often introduce electronegative impurities from lubricants on internal components or through small air leaks, and are not designed to meet the radiopurity requirements, custom-built pumps are an advantageous alternative. A new pump has been developed in Muenster in cooperation with the nEXO group at Stanford University and the nEXO/XENON group at Rensselaer Polytechnic Institute based on a magnetically-coupled piston in a hermetically sealed low-Rn-emanating vessel. This pump delivers high performance for noble gases, reaching more than 210 standard liters per minute (slpm) with argon and more than 170 slpm with xenon while maintaining a compression of up to 1.9 bar, demonstrating its capability for noble gas detectors and other applications requiring high standards of gas purity.

Highlights

Detectors based on noble elements have become widespread in many applications such as Compton telescopes [1,2,3], ionization calorimeters [4,5,6], neutrinoless double-beta-decay searches [7,8,9,10], and direct dark matter detection experiments [11,12,13,14,15]
By scaling the EXO-200 pump to support flow rates above 100 slpm and pressure differentials greater than 1 bar, a new, high performance pump has been developed as R&D for the XENON dark matter project and the nEXO neutrinoless double-beta-decay experiment
The magnetically-coupled piston pump was constructed of a monolithic type 316 L stainless-steel (SS) body with a length of 520 mm, an inner diameter of 127 mm, and an outer diameter of 133 mm, giving a total volume of 4.5 l

Summary

Introduction

Detectors based on noble elements have become widespread in many applications such as Compton telescopes [1,2,3], ionization calorimeters [4,5,6], neutrinoless double-beta-decay searches [7,8,9,10], and direct dark matter detection experiments [11,12,13,14,15]. Larger detectors need a higher purity to reach the same level of charge attenuation This is coupled with the fact that there is more material to clean, which necessitates a pump with significantly improved performance to allow high throughput at a pressure differential greater than 1 bar. By scaling the EXO-200 pump to support flow rates above 100 slpm and pressure differentials greater than 1 bar, a new, high performance pump has been developed as R&D for the XENON dark matter project and the nEXO neutrinoless double-beta-decay experiment This new pump features a larger effective volume with a length of 520 mm and an inner diameter of 127 mm in combination with an enhanced magnetic gradient based on alternating polarity to allow O(kN) coupling forces between internal and exterior magnets.

Magnet design

Mechanical design

Performance and longterm stability