DETECTION OF NEUTRONS BY LYMAN-ALPHA RADIATION

Patrick P. Hughes¹, Alan K. Thompson¹ , Michael A. Coplan², John W. Cooper², Robert E. Vest³ and Charles Clark³

¹Ionizing Radiation Division, NIST Gaithersburg, MD 20899

²Institue for Physical Sciences and Technology, University of Maryland College Park, MD 20742

³Electron and Optical Physics Division, NIST Gaithersburg, MD 20899

Lyman-alpha radiation has been detected as a result of the n(³He, t)p reaction occurring in a ³He gas cell.  We have found that under our experimental conditions, multiple photons are produced for each neutron absorbed in the gas cell volume [1].  The photon production appears to be the result of charge exchange and excitation collisions between the triton and ambient gas atoms.  Decay from the 2p to the ground state of the triton produces 121.6 nm light that is collected in a solar-blind photomultiplier tube connected to the gas cell.  This result suggests the possibility of utilizing these photons to detect cold and thermal neutrons with a compact device without the need for high voltages found in traditional proportional counters.  Recent results of measurements performed on pure ³He gas, at pressures between 7 and 100 kPa, show between 6 and 13 photons produced per absorbed neutron.  Additional measurements show enhanced photon production when ³He is mixed with different concentrations of ⁴He or Ar gases.

[1] A. K. Thompson, et al., J. Res. Natl. Inst. Stan. Technol., 113, 69, (2008)

CATEGORY: Physics

Author’s Name: Patrick P. Hughes

Mentor’s Name: Alan K. Thompson

Ionizing Radiation Division (846)

Physics Laboratory

Room B187, Building 235, Mail Stop: 8461

Tel: 301-975-5143

Fax: 301-926-1604

Email: patrick.hughes@nist.gov

Sigma Xi Membership:  No

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