Using Luminescent Materials As the Active Component for Multipurpose Sensors
Authors: Hollerman William A , Fontenot Ross , DeVera Armin B , Williams Stephen 
Published: February 2020

Environmental severity poses a significant challenge for Earth-based defense applications as well as human and/or robotic space missions. Past research has shown that luminescent materials can be used to measure exposure to ionizing radiation, temperature, and impact/pressure differential in adverse environments. In 1951, Birks and Black showed experimentally that the luminescent efficiency of anthracene bombarded by alphas varies with total fluence (N) as (I/I0) = 1/(1 + AN), where I is the luminescence yield, I0 is the initial yield, and A is a constant [ref. 1-2]. The half brightness (N1/2) is defined as the fluence that reduce the emission light yield to half and is equal to is the inverse of A[ref. 3]. Broser and Kallmann developed a similar relationship to the Birks and Black equation for inorganic phosphors irradiated using alpha particles [ref. 4]. From 1990 to the present, I found that the Birks and Black relation describes the reduction in light emission yield for every tested luminescent material except lead phosphate glass due to proton irradiation [ref. 5]. These results indicate that radiation produced quenching centers compete with emission for absorbed energy. For the last forty years, Allison et al. has shown that phosphor thermometry can be used to measure the temperature of moving or rotating surfaces under adverse conditions [ref. 6]. For the last decade, Fontenot and Hollerman et al. have concentrated on measuring the relative triboluminescent emission yields from inorganic zinc sulfide/similar compounds and new organic materials like europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA). Triboluminescence is produced when crystals of certain luminescent materials are stressed or broken. It was found that the ZnS compounds doped with Mn, Cu, and Pb had the largest measured triboluminescent emission yield of inorganic compounds [ref. 6]. The red emission luminescence from EuD4TEA can be seen in bright daylight with the naked eye [ref. 5]. Over the past few years, Fontenot et al. has optimized the synthesis process by making it more efficient and cheaper, discovered that it is possible to combine EuD4TEA with polymers such as poly(methyl methacrylate) (PMMA), and investigated the effects of various dopants such as dimethyl methylphosphonate (DMMP), dibutyl phosphate (DBP), dysprosium, samarium, and uranium [ref. 5]. To date, DBP is the best dopant creating nearly a six-fold increase in triboluminescent yield when compared to the original method [ref. 6]. The purpose of this presentation is to give an overview of my research in this area that show it is possible to use the same luminescent materials as the active element in multipurpose sensors. Particular emphasis will be placed on recent measurements made on some of these materials.
References:
1. J.B. Birks and F.A. Black, “Deterioration of Anthracene Under  Particle Bombardment”, Proc. of the Phys. Soc. (Lond.), A64, 874-875 (1951).
2. J.B. Birks, "Scintillations from Organic Crystals: Specific Fluorescence and Relative Response to Different Radiations", Proc. Phys. Soc. Sect. A. 64, 874 (1951).
3. W.A. Hollerman, “Investigation of Proton Induced Fluorescence From Yttrium and Gadolinium Compounds”, Ph.D. Dissertation, Alabama A&M University, 1996, Unpublished.
4. I. Broser and H. Kallmann, “On the Elementary Process of Light Excitation in Phosphors by  Particles, Fast Electrons, and Gamma Quanta”, Z. Naturforsch, 2A, 439 (1950).
5. W.A. Hollerman, R.S. Fontenot, S. Williams, and J. Miller, “Using luminescent materials as the active element for radiation sensors”, Proceedings of the SPIE Defense + Commercial Sensing Conference, Baltimore, Maryland, 9838-35 (2016).
6. S. W. Allison and G. T. Gillies, "Remote thermometry with thermographic phosphors: instrumentation and applications", Review of Scientific Instruments 68(7), 2615–2650 (1997).