A measurement of the holographic minimum-observable beam branching ratio in the fermilab 15-foot bubble chamber

Holography has been used successfully in combination with conventional optics for the first time in a large cryogenic bubble chamber, the 15-Foot Bubble Chamber at Fermilab, during a physics run. The innovative system combined the reference beam with the object beam, illuminating a conical volume of $\sim 1.4$~m$^3$. Bubble tracks from neutrino interactions with a width of $\sim 120\;\mu$m have been recorded with good contrast. The ratio of intensities of the object light to the reference light striking the film is called the Beam Branching Ratio. We obtained in our experiment an exceedingly small minimum-observable ratio of $(0.54 \pm 0.21) \times 10^{-7}$. The technology has the potential for a wide range of applications.