Nonproportional Response and Energy Resolution of Pure SrI$_{2}$ and SrI$_{2}$:5%Eu Scintillators

Abstract

Abstract-Nonproportional response of the scintillation yield of un-doped SrI and SrI :5%Eu was studied using highly monochromatic synchrotron irradiation ranging from 10.5 to 100 keV. Measurements were performed at 80 K and 295 K for SrI , and at 80 K, 295 K, 450 K, and 600 K for SrI :5%Eu. By making a dense data sampling around the iodine K-edge and using the recently developed K-dip spectroscopy method, the K-shell photoelectron response curves were reconstructed down to 500 eV. Proportionalities of X-ray response and K-shell photoelectron response of both crystals reveal temperature dependence. Energy resolution of the X-ray photopeak was analyzed as a function of temperature and deposited energy. Energy resolution improves with better proportionality.

Trends and Patterns of Scintillator Nonproportionality

“…Photon nonproportional response of halide scintillators as a function of X-ray or gamma photon energy. SrI 2 :Eu -black crosses [44]; LaBr 3 :Ceolive squares [39]; LaCl 3 :Ce -red open dots [39]; CaF 2 :Eu -blue stars [2]. Figure 11 shows the photon-nPRs of SrI 2 :Eu 2+ , LaBr 3 :Ce 3+ , LaCl 3 :Ce 3+ , and CaF 2 :Eu 2+ .…”

“…Figure 11 shows the photon-nPRs of SrI 2 :Eu 2+ , LaBr 3 :Ce 3+ , LaCl 3 :Ce 3+ , and CaF 2 :Eu 2+ . The concentration of Eu 2+ in SrI 2 :Eu was 5% [44], while for LaBr 3 :Ce and LaCl 3 :Ce the standard commercially available scintillators BrilLanCe 380 and BrilLanCe 350 containing 5% and 10% of Ce 3+ were used. The CaF 2 :Eu data were taken from the paper by Aitken et.…”

“…Photon nonproportional response of iodide scintillators as a function of X-ray or gamma photon energy. CsI:Na -black stars [2]; NaI:Tl -black dots [1]; CsI:Tl -red open dots; SrI 2 :Eu -black crosses [44]; LuI 3 :Ce -olive open squares [30,39]. Fig.…”

Nonproportionality of Scintillator Detectors. IV. Resolution Contribution from Delta-Rays

“…We are now in a position to calculate the light yield fluctuations of the generated delta-ray distribution, which we can accomplish by evaluating the standard deviation of the distribution using (7) and (8), while again appropriately weighting the individual deviations with (4) by and multiplying by 2.35 to convert the value of the summed standard deviations to the Gaussian-equivalent FWHM (full width at half maximum) of the light yield fluctuations: (10) where the integral is divided by , and then normalized by the average light yield of scattered electron pairs. Finally, to calculate the total contribution of these fluctuations for the primary electron initially at energy and proceeding along its trajectory generating delta-rays we use: (11) To summarize, we employ (6)- (11) to evaluate the resolution by: (a) calculating the probability distribution of the delta-rays, (b) following each probability-weighted delta-ray along its trajectory and determining its light yield, and (c) following the primary electron along its trajectory from the initial to final energy.…”

“…4 and the average value [ in (8), although this simple horizontal line which crosses through the curve is not indicated on the plot]. The above enunciated procedure yields the resolution arising from the delta-ray distributions [ in (10)]. The delta-ray light fluctuations along the entire primary electron trajectory can then be evaluated [ in (11)] for the initial electron energy of , included in Table I. For completeness in this section, we briefly summarize how we accounted for the Landau fluctuations of each delta-ray, by: (a) calculating the Landau resolutions of each delta-ray / scattered-primary-electron pair by adding their resolutions in quadrature with their respective weighting; (b) integrating the impact of these paired resolutions by employing the delta-ray distribution function of (4) by using (13) with the aid of (12); and (c) suitably summing the resolutions of these "electron pairs" along the trajectory of the primary electron, yielding the value of (14) as listed in Table I. )…”