Astroparticle Physics with a Trapped Electron
Lead Research Organisation:
Imperial College London
Department Name: Physics
Abstract
No one knows what 84% of the matter in the universe is, and the goal of APTE is to
find out. APTE will investigate two leading types of dark matter: axions and millicharged
particles. Axions not only resolve a longstanding puzzle in particle physics, but if their
mass is 0.001-1 meV they are an excellent dark matter candidate. Millicharged particles
arise in some theories beyond the Standard Model and have recently been suggested as a com-
ponent of dark matter that could explain the anomalous cooling of hydrogen in the early universe.
APTE will use an electron in a cryogenic Penning trap in an entirely new application: a
quantum sensor for astroparticle physics. The radial modes of the trapped electron will be
monitored for transitions caused by collisions with millicharged dark matter or the absorption
of single microwave photons from axion decays. Changes in radial quantum state will be
imprinted onto the trapped electron's axial frequency using a strong magnetic inhomogeneity,
the same principle as used to measure the electron magnetic moment. Drawing on my
experience in BASE, one of the world's most sensitive cryogenic Penning traps, I will pioneer
the use of advanced phase sensitive measurement protocols of my own invention. These will
be used to monitor the electron's axial frequency for phase jumps which occur when the radial
mode changes. With this electron single photon counter we will be able to overcome the Stan-
dard Quantum Limit which severely degrades our ability to investigate axion masses > 0.04 meV.
APTE will perform a first search for dark matter axions with masses around 0.128 meV
and millicharged dark matter particles with masses up to at least 1 GeV and charges 10^-1 to 10^-7 e. Both measurements probe important theories in a regime where there is currently no
data and few proposed experiments. This ground-breaking project will lay the foundations for
a future program of axion searches, as well as other applications in fundamental physics.
find out. APTE will investigate two leading types of dark matter: axions and millicharged
particles. Axions not only resolve a longstanding puzzle in particle physics, but if their
mass is 0.001-1 meV they are an excellent dark matter candidate. Millicharged particles
arise in some theories beyond the Standard Model and have recently been suggested as a com-
ponent of dark matter that could explain the anomalous cooling of hydrogen in the early universe.
APTE will use an electron in a cryogenic Penning trap in an entirely new application: a
quantum sensor for astroparticle physics. The radial modes of the trapped electron will be
monitored for transitions caused by collisions with millicharged dark matter or the absorption
of single microwave photons from axion decays. Changes in radial quantum state will be
imprinted onto the trapped electron's axial frequency using a strong magnetic inhomogeneity,
the same principle as used to measure the electron magnetic moment. Drawing on my
experience in BASE, one of the world's most sensitive cryogenic Penning traps, I will pioneer
the use of advanced phase sensitive measurement protocols of my own invention. These will
be used to monitor the electron's axial frequency for phase jumps which occur when the radial
mode changes. With this electron single photon counter we will be able to overcome the Stan-
dard Quantum Limit which severely degrades our ability to investigate axion masses > 0.04 meV.
APTE will perform a first search for dark matter axions with masses around 0.128 meV
and millicharged dark matter particles with masses up to at least 1 GeV and charges 10^-1 to 10^-7 e. Both measurements probe important theories in a regime where there is currently no
data and few proposed experiments. This ground-breaking project will lay the foundations for
a future program of axion searches, as well as other applications in fundamental physics.
