Design and fabrication of the Mu2e cryogenic distribution system

Mike White,Don Arnold,Valeri Poloubotko,Erik Voirin,Yuenian Huang,Mike Lamm,Andy Hocker,James Kilmer,Charles Hess,Karie Badgley,Grzegorz Tatkowski,Terry Tope,Nandhini Dhanaraj,Ian Young,Sandor Feher,Luciano Elementi,Jeff Brandt

doi:10.1088/1757-899x/755/1/012060

Mike White, Don Arnold + Show 15 more

Open Access

https://doi.org/10.1088/1757-899x/755/1/012060

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Abstract

The muon-to-electron conversion (Mu2e) experiment at Fermilab will be used to search for the charged lepton flavor-violating conversion of muons to electrons in the field of an atomic nucleus. The Mu2e experiment is currently in the design and construction stage and is expected to begin operations in 2022. The Mu2e experiment uses four large superconducting solenoid magnets including a Production Solenoid (PS), an Upstream and Downstream Transport Solenoid (TSu and TSd) and a Detector Solenoid (DS).This paper will focus on the cryogenic distribution system for these four solenoid magnets. Liquid helium will be supplied from two re-purposed Tevatron satellite refrigerators. A large cryogenic distribution box (DB) is located in the Mu2e building to distribute the required cryogens to each of the four solenoid magnets. Each solenoid magnet will have a dedicated transfer line and cryogenic feed box (FB). The solenoid magnets each require two liquid helium circuits and two liquid nitrogen circuits.The most unique feature about this cryogenic system is that the assemblies for the start of the superconducting portion of the power leads are mounted in feed boxes that are in the range of 23 m to 31 m away from the solenoid magnets. The cryogenic feed boxes are located remotely to provide protection from radiation damage and high magnetic fields. The power leads are NbTi superconducting cable stabilized with high conductivity aluminum. The 6061-T6 aluminum grade was selected for the transfer line piping so that the piping would thermally contract at the same rate as the power lead. A major concern for this transfer line is that a small helium leak could create an electric discharge arc due to the Paschen effect. This paper includes a description of the design features and testing done to ensure that the power leads are protected from the Paschen effect while still being adequately cooled to liquid helium temperatures.

Highlights

The muon-to-electron conversion (Mu2e) experiment at Fermilab will search for the charged lepton flavor-violating conversion of muons to electrons in the field of an atomic nucleus [1,2,3]
In the beam direction the first solenoid is the Production Solenoid (PS), which is a 1.8 m aperture axially graded solenoid with a peak field of 5 T used to focus secondary pions and muons from a production target located in the solenoid aperture [4,5]
The beam enters the Detector Solenoid, which is an axially graded solenoid where the electrons from the decays of muons that were transported to the aluminum stopping target, located at the DS entrance, are measured in a spectrometer located within the DS volume [9,10]

Summary

Introduction

The muon-to-electron conversion (Mu2e) experiment at Fermilab will search for the charged lepton flavor-violating conversion of muons to electrons in the field of an atomic nucleus [1,2,3]. The 6061-T6 aluminum grade was selected for the transfer line piping so that the piping would thermally contract at the same rate as the power lead. This paper includes a description of the design features and testing done to ensure that the power leads are protected from the Paschen effect while still being adequately cooled to liquid helium temperatures.

Results

Conclusion