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A Fabry-Perot Cavity for Compton Polarimetry
Botao Jia, Sirish Nanda, and Diana Parno
on behalf of the Compton Polarimetry Group
Optical setup
Mirror
We use lenses, mirrors and
other optical devices to
steer the laser beam into
the Fabry-Perot cavity,
where it is trapped
between two mirrors.
Green Laser
Photodetector
Faraday Isolator
Fabry-Perot Cavity
Photodetector
Electro-optical
Modulator
Compton Polarimetry
Electron detector
detects scattered
electrons
Fabry-Perot cavity
amplifies laser power
by bouncing light
between two mirrors
Lens
Beamsplitter
Half-wave
Plate
Mirror
The Fabry-Perot cavity
By measuring how electron spins are lined up in the electron
beam, we can study the structure of protons, neutrons and nuclei.
Compton polarimetry lets us make this measurement by
scattering the electron beam on laser photons trapped in a
Fabry-Perot cavity.
Unscattered electrons
continue on original path
Electron beam
Magnetic dipoles
bend the electron
beam
Lens
Wavelength
532 nm (green)
Power
3000 Watts
Gain
15,000
Length
0.85 m
Laser light bounces between two special mirrors that reflect 99.9937% of the light
that hits them. This increases the photon intensity by a factor of 15,000 and allows
us to take accurate polarimetry measurements. The mirror position must be stable at
a subatomic level.
Photon detector
detects scattered
photons
Light waves inside a Fabry-Perot cavity