Temperature Variation of Light Transmission in Scintillating Liquid Solvents
This note reports an initial study of temperature variation of light transmission in
scintillating liquid solvents. The study compares baseline spectra at 20º C with low
temperature spectra at 2-3º C. Spectra span wavelengths from 350 nm to 850 nm.
Solvents tested include LAB (linear alkylbenzene), PXE (phenylxylylethane), PC
(pseudocumene), and DD (dodecane).
Test samples were prepared by gently bubbling dry nitrogen through them in a small
flask for about 15 minutes. After sparging they were decanted directly to 10-cm long
cylindrical quartz photometry cells (Starna 34-Q-100). Cells were cleaned with highgrade methanol and flushed with dry nitrogen prior to receiving samples.
Spectra were taken using a miniature fiber optic portable spectrophotometer (Ocean
Optics USB4000) illuminated with deuterium and halogen bulbs (Ocean Optics DTMINI-2-GS). Bulbs were reported to have a stability of ±0.3% after a 30 minute warm
up. Sample cells were secured in a cuvette holder (Ocean Optics CUV-UV-10) during
spectrum acquisition. The cuvette holder was connected to the spectrometer and light
source with 2-m long, 400 micron optical fibers (Ocean Optics QP-400-2-SR).
Sample temperature was controlled by placing the cuvette holder inside a 1.8 cu. ft.
laboratory refrigerator (Summit FFAR-2L). Optical fibers were fed through holes drilled
in the sides of the refrigerator with the space around the cables filled with putty.
Temperature readings were taken using a thermistor coupled to a digital multimeter
(Fluke 179). Refrigerator cycling introduced an estimated ±0.5º C uncertainty in
measured temperature. Small dishes of desiccant (Indicating Drierite) were placed inside
the refrigerator to reduce humidity.
Baseline spectra were taken at room temperature (~20º C). Relative transmission spectra
were taken continuously as the samples cooled inside the running refrigerator. Spectra
were recorded after the samples reached typical ocean bottom temperature (~2-3º C) after
about 3 hours of refrigeration.
The following figures present the relative transmission data for the sampled solvents.
These preliminary spectra suggest small temperature variation of light transmission.
Further studies are recommended that include filtering samples and simultaneous
pressurization to 450 atmospheres (typical ocean bottom temperature).
Figure 1. Relative transmission spectrum of LAB (linear alkylbenzene).
Figure 2. Relative transmission spectrum of PXE (phenylxylylethane).
Figure 3. Relative transmission spectrum of PC (pseudocumene).
Figure 4. Relative transmission spectrum of DD (dodecane).