A Novel Scintillator Detector: Rare Earth Doped Lithium Tetraborate

Katherine Shene Author

07/26/2021 Added

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A perspective on the use of rare earth doped lithium tetraborate as a scintillator detector.

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[00:00:01.700]Hello, my name is Katherine Shene
[00:00:03.500]and the following will be a presentation based
[00:00:05.640]of a research done through RU
[00:00:07.510]at the University of Nebraska at Lincoln.
[00:00:10.350]Thank you to Dr. Peter Dowben
[00:00:12.130]for the use of his lab and his guidance
[00:00:14.090]as this would not have been possible without.
[00:00:16.720]This is a perspective on the concept of using
[00:00:19.140]rare earth doped lithium tetraborate
[00:00:21.010]as a scintillator detector.
[00:00:23.220]Listed here are the collaborators would their affiliations
[00:00:27.080]and I'd like to thank all of them as well.
[00:00:32.660]The motivation for a project like this comes from the large
[00:00:35.580]and increasing need for detection technologies,
[00:00:38.000]particularly for radiation detection,
[00:00:40.416]which can be used in a myriad of fields.
[00:00:42.650]As you can see, some are shown here.
[00:00:45.810]Detection technology has also been called for
[00:00:47.683]to be more sensitive and accurate with the aim of capturing
[00:00:50.500]and wider range of neutron energies
[00:00:52.530]so that they may be seen.
[00:00:54.500]Lithium Tetraborate a transparent
[00:00:56.470]inorganic crystalline material, has a lot of potential
[00:00:59.310]in regards to helping solve these problems.
[00:01:01.720]It has the capability to capture nutrients very well
[00:01:04.280]due to the nuclear isotopes boron-10 and lithium-6.
[00:01:09.480]So some background on scintillators is
[00:01:12.310]that the materials used,
[00:01:13.540]should ideally be both transparent enough to capture
[00:01:16.290]the light produced from scintillation as well as in
[00:01:19.140]possession of large neutron capture cross sections.
[00:01:22.220]This can be a potential issue
[00:01:23.670]as many materials do not
[00:01:25.110]fit those qualifications in one way or another.
[00:01:28.100]Lithium tetraborate, however,
[00:01:29.780]has the capabilities to meet the specifications
[00:01:32.900]mostly due to the large neutron capture cross section
[00:01:35.640]characteristic of its nuclear isotopes.
[00:01:39.740]Materials that share these previously stated qualities
[00:01:42.650]are able to produce visible neutron
[00:01:44.880]luminescence or scintillation.
[00:01:47.190]In our case with lithium tetraborate,
[00:01:49.040]this luminescence is produced through boron and lithium
[00:01:51.570]induced electron-hole pair formation and annihilation.
[00:01:55.850]And here we have the equation showing this,
[00:01:58.920]the two on the top are showing the instance
[00:02:01.430]of that boron-10 isotope put with the neutron,
[00:02:04.010]and the one on the bottom,
[00:02:05.680]is the lithium-6 isotope in the same situation.
[00:02:09.290]Over here, there's a picture of a
[00:02:11.431]single lithium tetraboric crystal
[00:02:13.930]showing that coveted transparency,
[00:02:16.567]and moving on to lithium tetraborate
[00:02:18.940]wide electronic bandgap of around 9.8 electron volts,
[00:02:24.210]which allows for light transmission
[00:02:26.060]in both the visible and infrared light ranges.
[00:02:29.370]Lithium Tetraborate also happens to be
[00:02:31.380]quite cost-effective as a scintillator,
[00:02:33.300]which is really a very important aspect.
[00:02:37.430]Some interesting things about lithium tetraborate
[00:02:39.920]include that it is a negative uniaxial crystal,
[00:02:42.685]meaning that out of its three axes,
[00:02:44.576]the refractive index of one, is going to be different than
[00:02:47.610]the other two axes refractive indices.
[00:02:50.430]Lithium Tetraborate can be synthesized
[00:02:52.420]with the Czochralski method,
[00:02:54.080]which mostly yields larger crystals,
[00:02:56.340]which is again good for this case
[00:02:58.540]as both size and cost are important.
[00:03:01.320]Being a piezoelectric material,
[00:03:03.370]lithium Tetraborate can convert mechanical energy
[00:03:05.900]into electrical energy and vice versa.
[00:03:08.840]As stated previously, it is a very useful material
[00:03:11.540]for neutron detection because of the isotopes.
[00:03:14.910]Over on the side here, is a helpful visual
[00:03:17.790]showing the internal structure of lithium tetraborate
[00:03:20.720]with a key showing which atoms are which,
[00:03:23.930]they're composed of oxygen boron and lithium.
[00:03:30.300]Doping lithium tetraborate with rare earth materials
[00:03:33.110]can further improve its function
[00:03:34.930]as a scintillator detector
[00:03:36.850]though, there is work to be done in order to find out which
[00:03:39.130]dopant will achieve the optimum quantum efficiency.
[00:03:42.340]Over here, is a
[00:03:44.950]structural model of dope lithium tetraborate,
[00:03:48.400]a bit different appearance-wise from the model of the
[00:03:50.840]undoped structure on the previous slide.
[00:03:53.240]Oxygen is shown in red, boron in light pink and the rare
[00:03:56.740]earth element in green.
[00:04:01.630]This figure here, shows the neutron pulse height spectra
[00:04:05.350]from a plutonium-beryllium source
[00:04:07.360]in comparison to gamma radiation
[00:04:09.500]from a cobalt source and background
[00:04:11.280]from various doped and undoped lithium tetraborates.
[00:04:14.810]It's a little hard to tell, my apologies,
[00:04:17.140]but in all cases, the scintillation appears
[00:04:19.950]blind to the gamma radiation.
[00:04:22.150]But as you may be able to tell, copper can work very nicely,
[00:04:25.300]especially with additional rare earths,
[00:04:27.240]can do very well as a scintillator.
[00:04:32.760]In conclusion, it is not yet known
[00:04:35.860]what will make the most efficient and accurate scintillator.
[00:04:38.880]However, determining that mix is a
[00:04:40.480]very important step of the process.
[00:04:42.880]We are on our way to finding that perfect blend of dopants,
[00:04:45.810]as there many promising theories in the works,
[00:04:48.300]that will hopefully be available in the near future?
[00:04:52.070]Thank you again to Dr. Dowben, Dr. Ilie
[00:04:56.130]and the university of Nebraska, Lincoln.
[00:05:00.230]Here are the references that were used for this presentation
[00:05:03.290]and here's the presentation in poster form.
[00:05:07.240]Thank you for listening.

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A Novel Scintillator Detector: Rare Earth Doped Lithium Tetraborate

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