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RAP opportunity at National Institute of Standards and Technology     NIST

Fundamental Physics with Cold Neutrons


Physical Measurement Laboratory, Radiation Physics Division

opportunity location
50.68.21.B4084 Gaithersburg, MD

NIST only participates in the February and August reviews.


name email phone
Maynard S. Dewey 301.975.4843
Shannon Hoogerheide 301.975.8582
Hans Pieter Mumm 301.975.8355
Jeffrey Scott Nico 301.975.4663


Neutron beta-decay is an excellent “laboratory” for studying the weak interaction. Through measurements of its lifetime and beta-decay correlation coefficients, one can extract parameters that completely characterize the weak force. Measurement of the lifetime also provides information on the abundances of the light elements produced during the Big Bang. Neutrons are used in searches for time-reversal (T) violation through a non-zero electric dipole moment or through a non-zero T-violating asymmetry coefficient in the decay process. Parity violation in neutrons can also be used to probe nucleon-nucleon weak interactions.

We are currently working on a measurement of the neutron lifetime using an apparatus that traps and counts the protons from decays within a cold neutron beam.  Concurrently, we are preparing an experiment that will measure the parity nonconserving spin rotation of polarized neutrons as they pass through a liquid helium target. This experiment will also search for new physics – new possible long-range spin dependent interactions (so-called 5th forces) using the spin rotation of polarized neutrons through a solid target. In conjunction with these experiments, we are improving the accuracy with which cold neutron fluence and polarization can be measured; capabilities which support the experiments mentioned, but also allow precision measurement of key reference neutron cross-sections and a recalibration of the national neutron source artifact NBS-1.  These small -scale projects offer opportunities across all aspects of an experimental program from simulation to operations and data analysis.

key words
cold neutrons; cosmology; neutron physics; beta decay


Citizenship:  Open to U.S. citizens
Level:  Open to Postdoctoral applicants


Base Stipend Travel Allotment Supplementation
$82,764.00 $3,000.00
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