Matthew Rose - Emission Spectra of Bicron Scintillators Objectives Measurements of Scintillator emission spectra using Laser and spectrometer, potentially for use in Super-NEMO calorimeter Repeat using X-ray Comparison - can Laser be used to approximate ionizing radiation of b decay? Comparison to spectra given by the manufacturers Effect on Energy Resolution Reasons for differences? I have been studying the emission spectra of three scintillators potentially for use in Super-NEMO Used a 337nm laser to produce scintillations Comparing these spectra with those produced using x-ray Comparison with manufacturer’s spectra Effect on energy resolution Reasons??? 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators

Matthew Rose - Emission Spectra of Bicron Scintillators Acquiring Spectra BC-404, BC-408 and BC-412 studied Laser! Scintillator! Spectrometer ! Laptop USB2000 miniature spectrometer used, with OOIBase32 spectrometer software Spectra processed using ROOT Three bicron scintillators used, chosen due to high light output Set up like so, laptop displays real-time spectra and saves data For analysis using root 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators

Matthew Rose - Emission Spectra of Bicron Scintillators Laser Spectra Uneven spectra observed Unexpected peaks Could be due to Laser effect Otherwise results very consistent Repeat using X-ray to check similarity Spiky spectra observed Unexpected peaks, especially in 412 Not attributed to background (see 412 pink line) Due to laser? Results otherwise very consistent - 5 spectra are plotted on each one, only tiny differences Perhaps using an X-ray set to produce scintillations would remove these problems… 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators

Matthew Rose - Emission Spectra of Bicron Scintillators X-ray vs. Laser Upon comparison however, the two spectra are very similar - the peaks are in the same place and the spikiness remains The ‘tail’ observed here only occurs when using the laser, however it would not be picked up by a PMT, as shown later Can therefore use the laser to approximate ionizing radiation, i.e. B decays Laser and X-ray spectra look similar Tail above 550 nm is removed by Q.E. of PMT Can use Laser to approximate ionizing radiation 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators

Comparison with Bicron Spectra Can now compare measured spectra with those provided by Bicron Clearly different, extra peaks are observed Direct Comparison necessary Having chosen to use laser spectra, can now compare these with provided Bicron spectra When measured spectra were rebinned to 10nm, the same as the bicron spectra, the spiky shape disappeared. The spectra clearly do not match, need to examine them more directly 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators

Matthew Rose - Emission Spectra of Bicron Scintillators Closer Inspection Peak wavelength is close to that expected Extra peaks observed Spectra seem to be stretched towards higher wavelengths Much light is lost when Q.E. of PMT is taken into account Upon closer inspection, the peaks can be seen to be within a few nanometres of those expected however there are other, unexpected peaks in the spectra, especially with BC-412 Some of these seem to corespond to minor peaks in the bicron spectra, but amplified and shifted to longer wavelengths This would cause much more of the light produced to be lost when the quantum efficiency of the PMT is taken into account, reducing the number of photoelectrons produced 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators

Q.E. and Energy Resolution Extra peaks mean that less light is being converted within the PMT, worsening the obtainable energy resolution Integral / Npe And as the energy resolution is proportional to the inverse square root of the number of photoelectrons, this would also worsen the energy resolution This figure shows the emission spectrum of BC-412 before and after multiplying by the QE, where the integral is proportional to the number of photoelectrons produced in the PMT 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators

Matthew Rose - Emission Spectra of Bicron Scintillators Analysis Bicron data using thin samples of Scintillator 5x5x2 cm3 blocks used, possibly light is absorbed and reemitted at longer wavelengths as it passes through the scintillator Extra peaks due to this, as well as spread of the spectra Only used Hamamatsu, Q.E. > 25% between 300 and 500 nm Could minimise effect on energy resolution using green-extended PMTs (peak Q.E. between 400 and 600 nm) These differences in spectra could be due to the thickness of the scintillators for which the bicron data is provided The measured spectra were taken for 5x5x2 blocks, comparable to the geometry planned for use in Super-NEMO Within the scintillator short, UV wavelength light is absorbed and reemitted at longer, visible wavelengths. Within a thicker piece of scintillator this wavelength shifting could occur multiple times, stretching the spectra towards longer wavelengths and reducing the relative height of the peaks at shorter wavelengths Have only taken energy resolutions using Hamamatsu high QE PMT, with a peak QE between 300&500nm As seen before, very little light is emitted below 400nm, so using a PMT which has the peak QE between 400 and 600 nm would hopefully minimise the effects of the geometry, and thus improve the achievaable energy resolution. 7/28/2019 Matthew Rose - Emission Spectra of Bicron Scintillators