Spin coating of TPB film on acrylic substrate and measurement of its wavelength shifting efficiency

Abstract

Scintillation light from liquid noble gas in a neutrino or dark matter experiment lies typically within the vacuum ultraviolet (VUV) region and might be strongly absorbed by surrounding materials such as light guides or photomultipliers. Tetraphenyl butadiene (TPB) is a fluorescent material and acts as a wavelength shifter (WLS) which can turn the UV light to the visible light around a peak wavelength of 425 nm, enabling the light signals to be detected easily for physics study. Compared with a traditional TPB coating method using vapor deposition, we propose an alternative technique with a spin coating procedure in order to facilitate the development of neutrino and dark matter detectors. This article introduces how to fabricate the TPB film on acrylics using the spin coating method, reports measurement of sample film thickness and roughness, shows the reemission spectrum, and quantifies the wavelength shifting efficiency (WLSE).

Wavelength Shifters for Applications in Liquid Argon Detectors

“…A demonstration of the spin-coating technique with toluene used as the solvent [88] resulted in approximately 200 nm-thick TPB coating (uniform, although with pinholes visible with SEM) showing 0.25 efficiency relative to evaporated TPB coating.…”

Measurement of the relative Quantum Efficiency of Hamamatsu model R5912-20MOD photomultiplier tubes at liquid argon temperature

“…Since the LED box is place about 30cm away from the top flange of the test dewar, the temperature shows nearly no change during the whole test. A model LXD-66MQ linear optical photosensor [18,19] is placed on the side of the hole in the LED box to monitor the change of LED light intensity. The signal of optical photosensor is converted by the I-V conversion amplifier and recorded by the oscilloscope.…”

Wavelength shifters for applications in liquid argon detectors

“…A demonstration of the spin-coating technique with toluene used as the solvent [86], resulted in approximately 200 nm thick TPB coating (uniform, although with pinholes visible with SEM) showing 0.25 efficiency relative to evaporated TPB coating.…”