ALPSII: Using Long Baseline Cavities to Probe the Hidden Sector
ORAL · Invited
Abstract
The Any Light Particle Search II (ALPS II) is an experiment taking place at DESY in Hamburg, Germany, that will attempt to measure ‘axion-like’ particles for the first time. These particles share similar characteristics with the axion and up to now remain unobserved in the hidden sector as they are very weakly interacting. Some of their other characteristics include having a low mass (< 1eV) and coupling to photons in the presence of magnetic fields.
ALPS II is what is known as a light-shining-through-a-wall (LSW) experiment. LSW experiments try to measure the coupling constant (gaγ) between photons and axion-like particles by shining a high power laser through a magnetic field at an optical barrier. This generates a beam of axion-like particles that pass through the barrier while the light is blocked. On the other side of the barrier, a second string of magnets convert some of the axion-like particles back to photons.
To boost the probability of axion-like particles reconverting to photons, ALPS II will be the first LSW experiment to employ optical cavities both before and after the wall. The use of two ~100 m cavities requires a sophisticated optical system to maintain their resonance condition and colinearity with respect to each other. 5.3 T superconducting dipole magnets repurposed from the HERA accelerator will provide the magnetic fields. The experiment will also have two independent detection methods, a transition edge sensor as well as a heterodyne detection scheme, to confirm the results. With this, ALPS II will achieve a sensitivity in the coupling between photons and axion-like particles of gaγ > 2×10-11 GeV-1 for m < 0.1 meV, roughly a factor of 1000 better than previous LSW experiments. I will give an overview of the experiment and discuss progress as well as challenges related to the optical system, magnets, detectors, and site preparation.
ALPS II is what is known as a light-shining-through-a-wall (LSW) experiment. LSW experiments try to measure the coupling constant (gaγ) between photons and axion-like particles by shining a high power laser through a magnetic field at an optical barrier. This generates a beam of axion-like particles that pass through the barrier while the light is blocked. On the other side of the barrier, a second string of magnets convert some of the axion-like particles back to photons.
To boost the probability of axion-like particles reconverting to photons, ALPS II will be the first LSW experiment to employ optical cavities both before and after the wall. The use of two ~100 m cavities requires a sophisticated optical system to maintain their resonance condition and colinearity with respect to each other. 5.3 T superconducting dipole magnets repurposed from the HERA accelerator will provide the magnetic fields. The experiment will also have two independent detection methods, a transition edge sensor as well as a heterodyne detection scheme, to confirm the results. With this, ALPS II will achieve a sensitivity in the coupling between photons and axion-like particles of gaγ > 2×10-11 GeV-1 for m < 0.1 meV, roughly a factor of 1000 better than previous LSW experiments. I will give an overview of the experiment and discuss progress as well as challenges related to the optical system, magnets, detectors, and site preparation.
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Presenters
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Aaron D Spector
DESY (Hamburg)
Authors
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Aaron D Spector
DESY (Hamburg)