Direct observation of bubble-assisted electroluminescence in liquid xenon

Understand

Bubble formation in liquid xenon underneath a Thick Gaseous Electron Multiplier (THGEM) electrode immersed in liquid xenon was observed with a CCD camera.

• With voltage across the THGEM, the appearance of bubbles was correlated with that of electroluminescence signals induced by ionization electrons from alpha-particle tracks.
• This confirms recent indirect evidence that the observed photons are due to electroluminescence within a xenon vapor layer trapped under the electrode.
• The bubbles seem to emerge spontaneously due to heat flow from 300K into the liquid, or in a controlled manner, by locally boiling the liquid with resistive wires.