ID:
27

Name:
LightFlux_100percent

Instrument ID:
Apogee PS-200 Spectroradiometer with hemispherical cosine corrector (#483)

Chamber:
Tran's big bag of air

Date of characterization experiment:
2018-09-18

Months since calibration:

Measurement technique:
Instrument measures the radiation in W/m2 with a CCD camera and cosine corrector

Photolysis frequency of NO₂ with max lighting [Hz]:

Photolysis frequency of H₂O₂ with max lighting [Hz]:

Photolysis frequency of O₃ with max lighting [Hz]:

Total number of lights:
72

Light percentage on:
100

Light intensity:

Light source type:
350nm black lights

Position and pattern of lights:
2 banks of 36 lights each are positioned on the left and right side of the chamber

Data collection description:
For each bank of 36 lights (right bank and left bank), one spectrum was taken for the left, middle, and right horizontal sections. For each horizontal section, data were additionally taken for each top, middle, and bottom vertical sections. The absorbing effect of the 3mil Teflon film of the chamber were measured by quantifying light flux without Teflon over the cosine corrector, with a piece of 3 mil Teflon that is clean, and with a piece of 3mil Teflon that is dirtied by a semi-opague film of organics (oils from hand). The "dirty" Teflon film was impregnated with fingerprints until it was saturated (until there were no more significant changes in opacity as seen by eye).

Data analysis description:
All data were averaged and converted to flux via the equation F (ph/cm2/nm/s) = 4*Irradiance/(Ephoton), where the factor of 4 is the ratio of the flux impinging on a sphere over the circular cross section of the cosine corrector. The transmission through dirty Teflon was corrected for during the data processing. The scalability of the light flux was tested by measuring 100% lights vs. 33% lights (mid section) in three horizontal areas (right, mid, left) and then taking an average. The 33% light midsection was approximately 36% of the total light flux. The top and bottom sections are thereby assigned a value of 32% each, as supported by their relative intensity measurements. The raw Flux data were then scaled by an Isoprene + H2O2 + hv experiment, where isoprene decay with the H2O2 concentration injected (and observed in CIMS) were modeled using a Matlab kinetic box model. The flux was adjusted with the observational data.

Link to supplemental information:

Additional notes:
The top, bottom, and middle vertical sections were 10-20% different from each other, with the middle section having the highest light flux. The right, middle, and left horizontal sections were 8-20% different from each other. These discrepancies could be due to user error in positioning the probe, as well as differences in light flux due to inhomogeneous reflectance throughout the chamber. The difference in transmission between no Teflon and dirty Teflon was approximately 5%. The difference in transmission between no Teflon and dirty Teflon was approximately 8%.

Characterization data file:
TBN_flux_alllights_adj-by-isop-exp-2021Aug.csv