J. Popp

Solenoid Magnet System for the Fermilab Mu2e Experiment

The Fermilab Mu2e experiment seeks to measure the rare process of direct muon to electron conversion in the field of a nucleus. Key to the design of the experiment is a system of three superconducting solenoids; a muon 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; an “S shaped” transport solenoid (TS) which selects and transports the subsequent muons towards a stopping target; a detector solenoid (DS) which is an axially graded solenoid at the upstream end to focus transported muons to a stopping target, and a spectrometer solenoid at the downstream end to accurately measure the momentum of the outgoing conversion electrons. The magnetic field requirements, the significant magnetic coupling between the solenoids, the curved muon transport geometry and the large beam induced energy deposition into the superconducting coils pose significant challenges to the magnetic, mechanical, and thermal design of this system. In this paper a conceptual design for the magnetic system which meets the Mu2e experiment requirements is presented.

The MECO experiment: a search for lepton flavor violation in muonic atoms

Abstract MECO will search for direct evidence of muon and electron flavor violation in the decay of muons in Coulomb bound states via coherent recoil of the nucleus and decay electron. The expected sensitivity to the μ − N→e − +N branching fraction relative to muon capture μ − N (A, Z)→ ν μ + N (A, Z−1) is R μe −17 at 90% confidence level, roughly 3–4 orders of magnitude lower than current limits. This article provides an overview of the experiment.

Tolerance Studies of the Mu2e Solenoid System

The muon-to-electron conversion experiment at Fermilab is designed to explore charged lepton flavor violation. It is composed of three large superconducting solenoids, namely, the production solenoid, the transport solenoid, and the detector solenoid. Each subsystem has a set of field requirements. Tolerance sensitivity studies of the magnet system were performed with the objective of demonstrating that the present magnet design meets all the field requirements. Systematic and random errors were considered on the position and alignment of the coils. The study helps to identify the critical sources of errors and which are translated to coil manufacturing and mechanical support tolerances.

Transport coefficients of relativistic plasmas

Abstract We summarize here calculations of transport coefficients for plasmas interacting through strong, electromagnetic, and weak interactions to leading order in the interaction strength, including rates of momentum and thermal relaxation, electrical conductivity, and viscosities of quark-gluon and electrodynamic plasmas. We discuss consequences for ultrarelativistics heavy ion collisions and neutron stars.

Requirements for the Mu2e Production Solenoid Heat and Radiation Shield

This paper describes the Heat and Radiation Shield (HRS). It serves to protect the superconducting coils of the Mu2e Production Solenoid (PS) from the intense radiation generated by the 8 GeV kinetic energy primary proton beam striking the production target within the warm bore of the PS. This shield also protects the coils in the far upstream end of the Transport Solenoid (TS), a straight section of coils called TS1, at the exit from the PS. The HRS aperture should allow the maximum stopping rate of negative muons in the Detector Solenoid stopping target. Requirements to the Heat and Radiation Shield are discussed in the paper. Work supported by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy. § Corresponding author. Email: vspron@fnal.gov

MECO Production Target Development

Production target design for the Muon‐Electron Conversion Experiment has undergone significant evolution recently. Limited progress in producing a suitable radiation‐cooled target has spurred interest in a water‐cooling system with drastically lower operating temperatures. This system results in less than about five percent reduction in stopped muon yield compared to a similar radiation cooled unit. The theoretical and experimental research surrounding target design is discussed.

Initial investigation OF 222Rn in the Tbilisi urban environment.

Georgia has geological formations with high uranium content, and several buildings are built with local materials. This can create potentially high radon exposures. Consequently, studies to mitigate these exposures have been started. This study presents a preliminary investigation of radon in Tbilisi, the capital of Georgia. An independent radiological monitoring program in Georgia has been initiated by the Radiocarbon and Low-Level Counting Section of I. Javakhishvili Tbilisi State University with the cooperation of the Environmental Monitoring Laboratory of the Physics/Health Physics Department at Idaho State University. At this initial stage the E-PERM systems and GammaTRACER were used for the measurement of gamma exposure and radon concentrations in air and water. Measurements in Sololaki, a densely populated historic district of Tbilisi, revealed indoor radon (222Rn) concentrations of 1.5–2.5 times more than the U.S. Environmental Protection Agency action level of 148 Bq m−3 (4 pCi L−1). Moreover, radon-in-air concentrations of 440 Bq m−3 and 3,500 Bq m−3 were observed at surface borehole openings within the residential district. Measurements of water from various tap water supplies displayed radon concentrations of 3–5 Bq L−1 while radon concentrations in water from the hydrogeological and thermal water boreholes were 5–19 Bq L−1. In addition, the background gamma absorbed dose rate in air ranged of 70–115 nGy h−1 at the radon test locations throughout the Tbilisi urban environment.

The quantum mechanics of particle-correlation measurements in high-energy heavy-ion collisions

Abstract The Hanbury Brown–Twiss (HBT) effect in two-particle correlations is a fundamental wave phenomenon that occurs at the sensitive elements of detectors; it is one of the few processes in elementary particle detection that depends on the wave mechanics of the produced particles. We analyze here, within a quantum mechanical framework for computing correlations among high-energy particles, how particle detectors produce the HBT effect. We focus on the role played by the wave functions of particles created in collisions and the sensitivity of the HBT effect to the arrival times of pairs at the detectors, and show that the two detector elements give an enhanced signal when the single-particle wave functions of the detected particles overlap at both elements within the characteristic atomic transition time of the elements. The measured pair correlation function is reduced when the delay in arrival times between pairs at the detectors is of order of or larger than the transition time.