  The PTOLEMY experiment (Princeton Tritium Observatory for Light,
Early-Universe, Massive-Neutrino Yield) aims to achieve the sensitivity
required to detect the relic neutrino background through a combination of a
large area surface-deposition tritium target, MAC-E filter methods, cryogenic
calorimetry, and RF tracking and time-of-flight systems. A small-scale
prototype is in operation at the Princeton Plasma Physics Laboratory with the
goal of validating the technologies that would enable the design of a 100 gram
PTOLEMY. With precision calorimetry in the prototype setup, the limitations
from quantum mechanical and Doppler broadening of the tritium target for
different substrates will be measured, including graphene substrates. Beyond
relic neutrino physics, sterile neutrinos contributing to the dark matter in
the universe are allowed by current constraints on partial contributions to the
number of active neutrino species in thermal equilibrium in the early universe.
The current PTOLEMY prototype is expected to have unique sensitivity in the
search for sterile neutrinos with electron-flavor content for masses of
0.1--1keV, where less stringent, 10eV, energy resolution is required. The
search for sterile neutrinos with electron-flavor content with the 100g PTOLEMY
is expected to reach the level $|U_{e4}|^2$ of $10^{-4}$--$10^{-6}$, depending
on the sterile neutrino mass.
