The Wavelength-Shifting Optical Module
<p>A schematic drawing of the WOM. UV photons are absorbed in the WLS paint layer and are re-emitted as optical photons. If the emission angle of the photons is larger than the critical angle, they are trapped by total internal reflection and are guided along the tube to small, low-noise PMTs.</p> "> Figure 2
<p>Visualization of several photon paths propagating in the wall of the WOM tube simulated with a GPU-based ray-tracing algorithm [<a href="#B13-sensors-22-01385" class="html-bibr">13</a>]. The photons are generated inside the paint layer of the tube in response to the incident UV photons (blue). Their attenuation probability depends on the effective path length, which, in turn, depends on the emission angle. In the inset, a UV photon (blue) is shown, which is absorbed and re-emitted in the material (green) or lost (red). The critical angle for the re-emitted photon defines a <span class="html-italic">loss cone</span> (gray dashed lines).</p> "> Figure 3
<p>Illustration of the solid angle under which the photons are captured as a function of the relative fraction of the radius <math display="inline"><semantics> <mrow> <msub> <mi>x</mi> <mn>0</mn> </msub> <mo>=</mo> <mfenced separators="" open="|" close="|"> <mover accent="true"> <mi>r</mi> <mo stretchy="false">→</mo> </mover> </mfenced> <mo>/</mo> <mi>R</mi> </mrow> </semantics></math> at which the photons are emitted (indicated by the yellow dot). The orange (blue) line in the upper plot indicates photons that encounter the surface under the critical angle as a function of the azimuth angle <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math> (<math display="inline"><semantics> <msub> <mi>ϕ</mi> <mn>0</mn> </msub> </semantics></math>) relative to the emission point (center of the cylinder). In the upper and middle plots, the blue shaded areas indicate solid angle regions under which photon trajectories are captured by total internal reflection, while red shaded areas show those that are not captured. In the middle plot, yellow arrows indicate directions of incident photons, while green arrows depict surface normals. In this example, the critical angle is chosen as <math display="inline"><semantics> <mrow> <msub> <mi>θ</mi> <mi>c</mi> </msub> <mo>=</mo> <mi>π</mi> <mo>/</mo> <mn>4</mn> </mrow> </semantics></math>.</p> "> Figure 4
<p>Fraction <math display="inline"><semantics> <msub> <mi>ϵ</mi> <mi>TIR</mi> </msub> </semantics></math> of the solid angle under which emitted photons are captured by total internal reflection as a function of the offset radius <math display="inline"><semantics> <msub> <mi>x</mi> <mn>0</mn> </msub> </semantics></math> of the emission point. The two lines represent a module immersed in air (solid) or water (dashed). The green dots indicated the captured efficiency for the prototype module, which is coated on the inside of tube. Minimal values for the emission point in the center of the tube and maximal values for emission on the outside of the tube are indicated by triangles.</p> "> Figure 5
<p>The combined efficiency for WOM operation in ice (or water), air, and LAB derived by simulating the propagation of <math display="inline"><semantics> <mrow> <mn>5</mn> <mo>×</mo> <msup> <mn>10</mn> <mn>5</mn> </msup> </mrow> </semantics></math> photons that are incident isotropically. The maximum achievable efficiency is 38.3% in ice at <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>≈</mo> <mn>1.32</mn> </mrow> </semantics></math>, 70.3% in air at <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>≈</mo> <mn>1.18</mn> </mrow> </semantics></math>, and 24.5% in LAB at <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>≈</mo> <mn>1.32</mn> </mrow> </semantics></math> (refractive index for LAB taken from Ref. [<a href="#B9-sensors-22-01385" class="html-bibr">9</a>]). For the geometry, the prototype design is used, as specified in <a href="#sec1-sensors-22-01385" class="html-sec">Section 1</a>.</p> "> Figure 6
<p>Schematic of the WOM test stand with a photograph of the darkbox.</p> "> Figure 7
<p>Profilometer measurements of two different paths on a slide coated with the wavelength shifter are shown. In each row, the measured profile is shown on the left, and a three-dimensional profile is shown in the middle. The path in the bottom row comprises a scratch in order to measure the thickness of the coating. A photograph of this slide is shown on the far right, in which the approximate measurement points are indicated.</p> "> Figure 8
<p>Absorption efficiency for different coating velocities <math display="inline"><semantics> <msub> <mi>v</mi> <mi>coating</mi> </msub> </semantics></math> and concentrations <span class="html-italic">c</span> of Bis-MSB in a WLS paint mixture of <math display="inline"><semantics> <mrow> <mn>400</mn> <mspace width="0.166667em"/> <mi>mL</mi> </mrow> </semantics></math> of anisole and <math display="inline"><semantics> <mrow> <mn>85.1</mn> <mspace width="0.166667em"/> <mi mathvariant="normal">g</mi> </mrow> </semantics></math> of PEMA (the second WLS was not used here). The methodology of the experiment is described in Ref. [<a href="#B24-sensors-22-01385" class="html-bibr">24</a>]. Shown in purple are fits to the different absorption efficiencies using Equation (<a href="#FD7-sensors-22-01385" class="html-disp-formula">7</a>) multiplied by a normalization constant.</p> "> Figure 9
<p>One-sided efficiency at 375 nm versus the coating speed for quartz tubes and PMMA tubes. Efficiencies are read out by a PMT 150 mm away from the illumination point. The solid lines show a fit with the thickness and absorption model from Equations (<a href="#FD7-sensors-22-01385" class="html-disp-formula">7</a>) and (<a href="#FD10-sensors-22-01385" class="html-disp-formula">10</a>).</p> "> Figure 10
<p>A 2D scan of the relative efficiency of a quartz tube. For a given longitudinal position, the efficiency is relative to the corresponding value at <math display="inline"><semantics> <mn>0</mn> <mo>°</mo> </semantics></math> in order to correct for the longitudinal intensity dependence. The angular variation of the efficiency is less than ±5%.</p> "> Figure 11
<p>Absorption (green) and emission spectra (red) of a WLS-coated quartz slide. The light yield efficiency <math display="inline"><semantics> <msubsup> <mi>ϵ</mi> <mrow> <mi>LY</mi> </mrow> <mi>WLS</mi> </msubsup> </semantics></math> measured on the prototype tube is shown in blue and orange. The methodologies of the experiments are described in Refs. [<a href="#B24-sensors-22-01385" class="html-bibr">24</a>,<a href="#B32-sensors-22-01385" class="html-bibr">32</a>].</p> "> Figure 12
<p>Efficiency as a function of the distance from the ends of the tube for a quartz tube [<a href="#B10-sensors-22-01385" class="html-bibr">10</a>]. The flattened model efficiency is used as a fit function to extract attenuation lengths. The injected light has a wavelength of (<math display="inline"><semantics> <mrow> <mn>375.00</mn> <mo>±</mo> <mn>1.06</mn> </mrow> </semantics></math>) nm. Systematic errors are shown as shaded areas.</p> "> Figure 13
<p>The measured transit time spread of a WOM tube with one attached PMT is shown for different <span class="html-italic">z</span>-positions along the tube.</p> "> Figure 14
<p>Effective areas of the WOM in the prototype design and a single PMT of this ensemble in dependence on wavelength estimated with the MC simulation described in <a href="#sec2dot3-sensors-22-01385" class="html-sec">Section 2.3</a>, assuming both devices are deployed in ice.</p> "> Figure 15
<p>Scale of the effective area at low wavelengths in ice in dependence on the WOM tube length obtained by the MC simulation. Prototype specifications were used for all other properties of the WOM.</p> "> Figure 16
<p>A demonstrator device made in the prototype configuration and photographed under UV illumination (<b>left</b>). The electronics comprise a PMT pulse readout, environmental sensors, and communication. After deployment, a photograph was taken by a robot in the Ocean Network Canada. (<b>right</b>). Right picture: Courtesy of the ONC.</p> ">
Abstract
:1. Introduction
2. Performance Factors
2.1. Total Internal Reflection
2.2. Light Propagation
2.3. Light Transmission
3. Coating
3.1. Test Stand
3.2. Chemical Composition
- maximal overlap of the emission spectrum and the sensitivity of the readout PMT;
- large Stokes shift, i.e., minimal overlap of the absorption and emission spectra;
- maximal transparency of the WLS paint for re-emitted photons;
- similar refractive index of the coating and the WLS tube material;
- good adhesiveness and mechanical properties;
- optical thickness to enable reaching high concentration of WLS film to absorb 100% of the light for a broad spectrum.
3.3. Coating Process
- Coating on the inside shifts the light emission point towards the center, resulting in a reduced capture efficiency, as discussed in Section 2.1. The performance loss will increase with the thickness of the tube and the refractive index of the environment in which the coated tube is deployed.
- While quartz glass has high transmission down to wavelengths of 180 nm, PMMA is generally opaque to light below 300 nm [28], but in commercial products, it is often doped with additional UV absorbers to reduce aging in sunlight, thus limiting the UV light yield. Quartz glass can therefore be coated on either side, while PMMA performs best when coated outside.
- Coating a tube on the inside allows for easier handling. Impurities such as fat or dirt act as scattering centers for photons traveling inside the tube. Under UV light illumination, contaminated areas are clearly visible, presumably because photons couple out of the tube at these sites. The WLS paint is hydrophilic and therefore delaminates as a whole when immersed in water, rendering the tube opaque to light.
- In an assembly, an inside-coated tube will not interact chemically with the medium surrounding it, allowing for the surrounding medium to be chosen freely. While embedding the module in a housing can alleviate the problem in a similar way for outside-coated tubes, a filling material is generally required between the housing and the tube (see Figure 5), transferring the problem to chemical compatibility with the filling material.
3.4. Absorption and Emission
3.5. Deterioration
3.6. Optical Coupling
4. Characterization
4.1. Efficiency
- Overlap between absorption and emission spectra of the WLS paint leads to re-absorption of emitted photons with an estimated 0.39% relative efficiency loss.
- Interface losses are calculated using the difference in refractive indices between the tube () and glass of the PMT () together with the angular distribution on the end faces from the simulation. Averaging between s- and p-polarized transmission yields a relative loss of .
4.2. Transit Time Spread of Photons
- Time resolution of the PMT, which is measured to be a Gaussian profile with ns.
- Absorption and re-emission of the WLS paint measured to be an exponential decay with ns (in accordance with Ref. [23]). For the lower UV , where the light needs to be absorbed and shifted by p-Terphenyl first (as mentioned in Section 3), an additional exponential decay with a time constant of around 1 ns is expected.
- Photon trajectory path length distribution inside the tube depending on the absorption length of the material.
4.3. Noise
4.4. Effective Area
4.5. Signal-to-Noise Ratio
5. Conclusions, Applications, and Outlook
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Acknowledgments
Conflicts of Interest
References
- Aartsen, M.G.; Ackermann, M.; Adams, J.; Aguilar, J.A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; et al. The IceCube Neutrino Observatory: Instrumentation and Online Systems. JINST 2017, 12, P03012. [Google Scholar] [CrossRef]
- Fukuda, S.; Hayato, Y.; Iida, T.; Iyogi, K.; Kameda, J.; Kishimoto, Y.; Koshio, Y.; Marti, L.; Miura, M.; Moriyama, S.; et al. The Super-Kamiokande detector. Nucl. Instrum. Meth. A 2003, 501, 418–462. [Google Scholar] [CrossRef]
- Alimonti, G.; Arpesella, C.; Back, H.; Balata, M.; Bartolomei, D.; de Bellefon, A.; Bellini, G.; Benziger, J.; Bevilacqua, A.; Bondi, D.; et al. The Borexino detector at the Laboratori Nazionali del Gran Sasso. Nucl. Instrum. Meth. A 2009, 600, 568–593. [Google Scholar] [CrossRef] [Green Version]
- Boger, J.; Hahn, R.L.; Rowley, J.K.; Carter, A.L.; Hollebone, B.; Kessler, D.; Blevis, I.; Dalnoki-Veress, F.; DeKok, A.; Farine, J.; et al. The Sudbury neutrino observatory. Nucl. Instrum. Meth. A 2000, 449, 172–207. [Google Scholar] [CrossRef] [Green Version]
- An, F.; An, G.; An, Q.; Antonelli, V.; Baussan, E.; Beacom, J.; Bezrukov, L.; Blyth, S.; Brugnera, R.; Avanzini, M.B.; et al. Neutrino physics with JUNO. J. Phys. G Nucl. Part. Phys. 2016, 43, 030401. [Google Scholar] [CrossRef]
- Aprile, E.; Arisaka, K.; Arneodo, F.; Askin, A.; Baudis, L.; Behrens, A.; Brown, E.; Cardoso, J.M.R.; Choi, B.; Cline, D.; et al. The XENON100 dark matter experiment. Astropart. Phys. 2012, 35, 573–590. [Google Scholar] [CrossRef] [Green Version]
- Akerib, D.S.; Bai, X.; Bedikian, S.; Bernard, E.; Bernstein, A.; Bolozdynya, A.; Bradley, A.; Byram, D.; Cahn, S.B.; Camp, C.; et al. The Large Underground Xenon (LUX) experiment. Nucl. Instrum. Meth. A 2013, 704, 111–126. [Google Scholar] [CrossRef] [Green Version]
- Aalbers, J.; Agostini, F.; Alfonsi, M.; Amaro, F.D.; Amsler, C.; Aprile, E.; Arazi, L.; Arneodo, F.; Barrow, P.; Baudis, L.; et al. DARWIN: Towards the ultimate dark matter detector. J. Cosmol. Astropart. Phys. 2016, 2016, 017. [Google Scholar] [CrossRef]
- Tseung, H.W.C.; Tolich, N. Ellipsometric measurements of the refractive indices of linear alkylbenzene and EJ-301 scintillators from 210 to 1000 nm. Phys. Scr. 2011, 84, 035701. [Google Scholar] [CrossRef]
- Heraeus. HSQ 300. 2021. Available online: https://www.heraeus.com/media/media/hca/doc_hca/products_and_solutions_8/solids/Solids_HSQ300_330MF_EN.pdf (accessed on 26 January 2022).
- Hamamatsu. R14689. 2021. Available online: https://www.hamamatsu.com/eu/en/product/type/R14689/index.html (accessed on 26 January 2022).
- Eljen Technology. EJ-550. 2021. Available online: https://eljentechnology.com/products/accessories/ej-550-ej-552 (accessed on 26 January 2022).
- Thomas, F. Light Propagation Simulation for the Wavelength-Shifting Optical Module on CUDA GPUs. Master’s Thesis, Johannes Gutenberg University Mainz, Mainz, Germany, 2019. Available online: https://butler.physik.uni-mainz.de/icecube/thesis/master_Florian_Thomas.pdf (accessed on 26 January 2022).
- Heraeus. Transmission Calculator for Optical Applications. 2021. Available online: https://www.heraeus.com/en/hca/fused_silica_quartz_knowledge_base_1/t_calc_1/transmission_calc_opt/transmission_calculator_opt.html?chartIndex=2&selection=suprasil_311_312%2Csuprasil_1_2a%2Csuprasil_2b%2Cspectrosil_2000&thickness=10&rangeX=120%2C4500 (accessed on 26 January 2022).
- Quantum Design. Arc Light Sources 50–150 W Arc Light Source. 2022. Available online: https://qd-europe.com/fileadmin/Mediapool/products/lightsources/en/LQ_50_150_w_arc_light_source_en.pdf (accessed on 26 January 2022).
- Quantum Design. Monochromators Monochromator MSH-300 with Variable Slit. 2022. Available online: https://qd-europe.com/fileadmin/Mediapool/products/Bentham/_pdf/MSH_300_with_variable_slit.pdf (accessed on 26 January 2022).
- Zurich Instruments. zi MFLI Lock in Amplifier. 2021. Available online: https://www.zhinst.com/sites/default/files/documents/2021-12/zi_mfli_leaflet_v2.pdf (accessed on 26 January 2022).
- Hamamatsu Photonics. Si Photodiodes with BNC Connector. 2022. Available online: https://www.hamamatsu.com/resources/pdf/ssd/s2281_series_kspd1044e.pdf (accessed on 26 January 2022).
- Thorlabs. Thorlabs Liquid Light Guide. 2021. Available online: https://www.thorlabs.com/drawings/fe93bd8d318e7307-7BA1AD90-E649-0882-7162D968CDA653D9/LLG5-4T-SpecSheet.pdf (accessed on 26 January 2022).
- Rack-Helleis, J. Efficiency Determination of the Wavelength-Shifting Optical Module (WOM). Master’s Thesis, Johannes Gutenberg University Mainz, Mainz, Germany, 2019. Available online: https://butler.physik.uni-mainz.de/icecube/thesis/master_John_Rack-Helleis.pdf (accessed on 26 January 2022).
- Rongen, M.; Schaufel, M. Design and evaluation of a versatile picosecond light pulser. JINST 2018, 13, P06002. [Google Scholar] [CrossRef] [Green Version]
- Teledyne. SP Devices ADQ 14. 2021. Available online: https://www.spdevices.com/documents/datasheets/19-adq14-datasheet/file (accessed on 26 January 2022).
- Kuzniak, M.; Szelc, A.M. Wavelength Shifters for Applications in Liquid Argon Detectors. Instruments 2020, 5, 4. [Google Scholar] [CrossRef]
- Hebecker, D. Developement of a Single Photon Detector with Wavelength Shifting and Light Guiding Technology. Master’s Thesis, University of Bonn, Bonn, Germany, 2014. Available online: https://www-zeuthen.desy.de/~hebecked/Publications_etc./Master_Thesis/Dustin_hebecker_master_thesis.pdf (accessed on 26 January 2022).
- Preservation Equipment. Paraloid B72. 2021. Available online: https://www.preservationequipment.com/files//4ba8f3dc-85c1-44e4-9237-a3db00db1ef4/Paraloid%20B72%20Use.pdf (accessed on 26 January 2022).
- Beise, J. Transport Losses in Light Guides for the WOM Application. Bachelor’s Thesis, Humboldt-University Berlin, Berlin, Germany, 2019. [Google Scholar]
- Carl Roth GmbH + Co. KG. Mucasol Universalreiniger. 2021. Available online: https://www.carlroth.com/de/de/reinigungsmittel-fuer-ultraschallgeraete/universalreiniger-mucasol/p/1a3l.1 (accessed on 26 January 2022).
- Abdel-Mottaleb, M.S.; Ahmed, R.M. Optical Study on Polymethyl methacrylate/Polyvinyl acetate Blends. Int. J. Photoenergy 2009, 2009, 150389. [Google Scholar] [CrossRef]
- Brinker, C.J. Dip Coating. In Chemical Solution Deposition of Functional Oxide Thin Films; Springer: Berlin/Heidelberg, Germany, 2013; pp. 233–261. [Google Scholar] [CrossRef]
- Rio, E.; Boulogne, F. Withdrawing a solid from a bath: How much liquid is coated? Adv. Colloid Interface Sci. 2017, 247, 100–114. [Google Scholar] [CrossRef] [PubMed] [Green Version]
- Derjaguin, B. On the thickness of the liquid film adhering to the walls of a vessel after emptying. Prog. Surf. Sci. 1993, 43, 134–137. [Google Scholar] [CrossRef]
- Binn, L.S. Charakterisierung von dünnen Wellenlängenschiebenden Schichten. Bachelor’s Thesis, University of Mainz, Mainz, Germany, 2018. Available online: https://butler.physik.uni-mainz.de/icecube/thesis/bachelor_Lucas_Binn.pdf (accessed on 26 January 2022).
- Norland. NOA 148H. 2021. Available online: https://www.norlandprod.com/adhesives/NOA148.html (accessed on 26 January 2022).
- Falke, P. Entwicklung Eines Lichtkonzentrators Basierend Auf Einer Hohlzylinder Geometrie. Bachelor’s Thesis, Universität Bonn, Bonn, Germany, 2014. [Google Scholar]
- Schnur, R. Optimierung des Adiabatischen Lichtleiters für das Wavelength-Shifting Optical Module. Bachelor’s Thesis, Johannes Gutenberg-Universität Mainz, Mainz, Germany, 2020. Available online: https://butler.physik.uni-mainz.de/icecube/thesis/bachelor_Ronja_Schnur.pdf (accessed on 26 January 2022).
- Hebecker, D. Development of a Single Photon Detector Using Wavelength-Shifting and Light-Guiding Technology. Ph.D. Thesis, Humbold-Universität Berlin, Berlin, Germany, 2021. Available online: https://edoc.hu-berlin.de/handle/18452/23885?locale-attribute=de (accessed on 26 January 2022).
- Schlickmann, L. Zeitantwort des Wellenlängenschiebenden Optischen Moduls (WOM). Master’s Thesis, Johannes Gutenberg University Mainz, Mainz, Germany, 2021. Available online: https://butler.physik.uni-mainz.de/icecube/thesis/bachelor_SchlickmannLea.pdf (accessed on 26 January 2022). (In German).
- Bubeck, M. Developement of a Wavelength-Shifting Optical Module. Master’s Thesis, Johannes Gutenberg University Mainz, Mainz, Germany, 2020; p. 19. Available online: https://butler.physik.uni-mainz.de/icecube/thesis/master_Maximilian_Bubeck.pdf (accessed on 26 January 2022).
- Rea, I.C.; Holzapfel, K.; Baron, A.; Bailly, N.; Bedard, J.; Bohmer, M.; Bosma, J.; Brussow, D.; Cheng, J.; Clark, K.; et al. P-ONE second pathfinder mission: STRAW-b. PoS 2021, ICRC2021, 1092. [Google Scholar] [CrossRef]
- Ehlert, M.; Hollnagel, A.; Korol, I.; Korzenev, A.; Lacker, H.; Mermod, P.; Schliwinski, J.; Shihora, L.; Venkova, P.; Wurm, M. Proof-of-principle measurements with a liquid-scintillator detector using wavelength-shifting optical modules. JINST 2019, 14, P03021. [Google Scholar] [CrossRef] [Green Version]
- SHiP Collaboration. The SHiP experiment at the proposed CERN SPS Beam Dump Facility. arXiv 2021, arXiv:2112.01487. [Google Scholar]
- Rack-Helleis, J.; Pollmann, A.; Rongen, M. The Wavelength-shifting Optical Module (WOM) for the IceCube Upgrade. PoS 2021, ICRC2021, 1038. [Google Scholar]
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Bastian-Querner, B.; Binn, L.S.; Böser, S.; Brostean-Kaiser, J.; Hebecker, D.; Helbing, K.; Karg, T.; Köpke, L.; Kowalski, M.; Peiffer, P.; et al. The Wavelength-Shifting Optical Module. Sensors 2022, 22, 1385. https://doi.org/10.3390/s22041385
Bastian-Querner B, Binn LS, Böser S, Brostean-Kaiser J, Hebecker D, Helbing K, Karg T, Köpke L, Kowalski M, Peiffer P, et al. The Wavelength-Shifting Optical Module. Sensors. 2022; 22(4):1385. https://doi.org/10.3390/s22041385
Chicago/Turabian StyleBastian-Querner, Benjamin, Lucas S. Binn, Sebastian Böser, Jannes Brostean-Kaiser, Dustin Hebecker, Klaus Helbing, Timo Karg, Lutz Köpke, Marek Kowalski, Peter Peiffer, and et al. 2022. "The Wavelength-Shifting Optical Module" Sensors 22, no. 4: 1385. https://doi.org/10.3390/s22041385