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Title: Radial distribution of charged particles in a magnetic field

The radial spread of charged particles emitted from a point source in a magnetic field is a potential source of systematic error for any experiment where magnetic fields guide charged particles to detectors with finite size. Assuming uniform probability as a function of the phase along the particle’s helical trajectory, an analytic solution for the radial probability distribution function follows which applies to experiments in which particles are generated throughout a volume that spans a sufficient length along the axis of a homogeneous magnetic field. This approach leads to the same result as a different derivation given by Dubbers et al., Nucl. Instrum. Methods Phys. Res., Sect. A 763, 112–119 (2014). But the constant phase approximation does not strictly apply to finite source volumes or fixed positions, which lead to local maxima in the radial distribution of emitted particles at the plane of the detector. A simple method is given to calculate such distributions, then the effect is demonstrated with data from a {sup 207}Bi electron-conversion source in the superconducting solenoid magnet spectrometer of the Ultracold Neutron facility at the Los Alamos Neutron Science Center. Implications for neutron beta decay spectroscopy are discussed.
Authors:
; ; ;  [1] ;  [2] ;  [1] ;  [3]
  1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  2. North Carolina State University, Raleigh, North Carolina 27695 (United States)
  3. (United States)
Publication Date:
OSTI Identifier:
22392345
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 86; Journal Issue: 2; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; BETA DECAY; BISMUTH 207; CHARGED PARTICLES; DISTRIBUTION FUNCTIONS; LEAD; MAGNETIC FIELDS; MAGNETIC SPECTROMETERS; SOLENOIDS; SPATIAL DISTRIBUTION; SUPERCONDUCTING MAGNETS; ULTRACOLD NEUTRONS