PoS(ICRC2019)890 http://pos.sissa.it/ † . For collaboration list see PoS(ICRC2019)1177 , I.C. Rea, for the STRAW Collaboration ∗ [email protected], [email protected] Speaker. http://inspirehep.net/record/1701337 astronomy uses large volumepoint detectors their to origin. search Detectors such for asDetector astrophysical IceCube (GVD) at in and Lake the Baikal Geographic pin- and South KM3NeTkilometer Pole, in of the the Gigaton water Mediterranean Volume or sea, ice instrument uptions. for to measuring Especially a Cherenkov cubic the radiation utilization created ofpast, in the has neutrino-matter clear been interac- water facing of severe difficulties theOcean in deep deploying Networks sea and Canada as maintaining (ONC), Cherenkov the medium, an offshoredeep in infrastructure. initiative sea the of infrastructure the for University scientific ofnetwork purposes, Victoria, nodes, off has located the on been Canadian the operating Pacific coastBasin abyssal since - plain, could years. off be the an One ideal coast site of of forWater Vancouver their (STRAW) a Island were future - neutrino developed Cascadia telescope. at The the Strings Technicalwith for University ONC Absorption of and Length the in Munich University (TUM) of in Alberta.Cascadia collaboration Two Basin strings with in optical order modules to have measure been thea deployed optical larger at properties installation. of We the will water give andon a study the the brief absorption feasibility length overview of of and optical the background STRAW setup at Cascadia and Basin. present first results † ∗ Copyright owned by the author(s) under the terms of the Creative Commons c Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). Physics Dept., Technical University Munich, Germany E-mail: 36th International Cosmic Ray Conference -ICRC2019- July 24th - August 1st, 2019 Madison, WI, U.S.A. C. Fruck STRAW: STRings for Absorption length in Water PoS(ICRC2019)890 ], 3 ). Each C. Fruck 1 . ] in Siberia. A new ]. More recently two 8 5 , 4 ]. The first attempt towards such a 12 1 Pacific Ocean Neutrino Explorer (P-ONE) 2600 m b.s.l. due to its favorable ocean floor topology, ∼ ], in the Mediterranean Sea and Baikal-GVD [ ]. The project was cancelled after facing numerous challenges with deep 6 7 46’ W), at a depth of ◦ 46’ N, 127 ◦ STRAW has been designed with all aspects of being a pathfinder mission for a large neutrino Using high energy cosmic neutrinos as messengers in astronomy has some unique advantages ], initially designed for the IceCube upgrade. Those are then received by the STRAW Digital 13 detector in mind. Oneoptical of properties the of main the goals waterminescence. is as well to Another as characterize goal backgrounds the is caused Cascadia totomultipliers by (PMTs) Basin face ambient in the site radioactivity an challenges regarding and array that the biolu- of2 come kilometers strings with below equipped deploying the with and optical water modules operating surface.by at emitting pho- Therefore light a flashes it depth with of was an more decided early[ than version to of measure the the Precise Optical attenuation Calibration length Module (POCAM) 2. Design Optical Modules (sDOMs) that were newly developed, basedThe on three the light-emitter design modules of the (POCAMs) POCAM and housing. form the baselines five sensor of modules different (sDOMs), lengths in thatgree combination range of from redundancy 20 for m safety to against 90 m module and malfunction also and implement cross-checking a (see certain Fig. de- comparably slow currents and low sedimentation rate.for In Absorption late length 2017 in the Water” pathfinder (STRAW) was missionnich designed “STrings (TUM) and built in at collaboration the Technical with2018 University by Mu- the an ONC ONC and vessel. theand A will University third be of mooring deployed Alberta in line, Spring and namedBasin 2020. has STRAW-b, deployed is also The in presently began design under June under of the construction a project large name volume neutrino telescope at Cascadia now operating smoothly since 10discoveries years. lead to The the data detection collectednew of by projects the have IceCube, first been among non-stellar launched other neutrinoor towards mile-stone source the lake [ final water: goal of KM3NeTopportunity [ instrumenting presents a itself cubic in kilometer form of ofobservatory sea the by vast Ocean area Networks of Canada (ONC). instrumentedsub-sea NEPTUNE sea cables consists floor for power of called and hundreds the data of NEPTUNE communicationver kilometers in the of Island. northeast Pacific Of Ocean particular in interest frontBasin of for (47 Vancou- is the deep-sea infrastructure at Cascadia water deployments and operation. The first andcubic until kilometer now was only made successful attempt in to ice instrument with one the completion of the IceCube detector at the south pole [ but at the same time presents majorthe challenges to fact the that antiparticle neutrinos community, both only closely participatehadronic related in to interactions, the even weak if interaction. lookingthey Therefore into are they dense are notoriously astrophysical ideal hard environments probes to but for detect.(cubic-kilometers) at of The the transparent only same material known time with strategy light so sensors far [ is to instrument huge volumes STRAW 1. Introduction detector was actually supposed toand be Neutrino constructed Detection in (DUMAND) the project deep aimedthe ocean. for Big Island a The of depth Deep Hawaii of [ Underwater 4800 Muon m in the Pacific Ocean off PoS(ICRC2019)890 C. Fruck #2 #3 kN kN kN kN

#5 #4 1x19 m 1x37 coating 36 m m m 62 109 190 .66 .10 .51 .96 .1mm .1mm PG5 8 +2mm SWL: MBL: POCAM 49 SDOM 29 POCAM 107 SDOM 69 PG20 14 SWL: MBL: mm 400 String Yellow spacing m m m m m m m m m m .5 .5 .5 .0 .0 .0 .0 .0 .0 .0 2 5 1 0

70 50 30

115 110 146 145 Junction-Box horizontal VECTORWORKS EDUCATIONAL VERSION VECTORWORKS EDUCATIONAL VERSION m 37 String Blue m m m m lift kg kN kN #1 #2 #3 #1 .40 .98 .79 .79 mount Buoy kg 50 625 Anode

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250 Padeye 69 49 29 Anchor 109 Spacers 435 Spacers Spacers Spacers Spacers alignment SDOM SDOM SDOM 4 8 4 4 Mini-JB WLL: MBL: POCAM Top-Spacers for Sacrificial Bottom-Spacer + Deployment adjustable Mini-Junction-Box + Detailed technical sketch of the two STRAW mooring lines showing the exact (measured) geom- Figure 1: etry of all modules. string consists of twospaces parallel and steel stretched lines between a of bottomdata about anchor and connections 115 m a are deep-sea length, realized buoyancy at separated throughattached the to by sub-sea, top. the 30 multi-wire spacers All cm in electric copper wide a and cables wayare metal that to mounted minimizes on each load one on, module and side that shadowing ofules by are the along the one strings cables. string. to The ensure modules Additionally a the37 m free two are strings light equipped that path have with between been rotatable two(ROV) installed to neighbouring platforms at adjust mod- on a the the relative relative anchors distance orientation of from that of allow the the a strings modules remotely until are the operated connected modules vehicle face to each the other. Mini-Junction-Boxes All (MJBs) cables in a star like configuration. STRAW PoS(ICRC2019)890 C. Fruck 40 ns but ad- > ODROID (single board computer, DAQ) Medusa (timing synchronisation) TRB3sc (FPGA TDC, ToT measurement) . 2 ] on a Linux operating system. A schematic Polyphem (Power interconnection, supply, sensors) 1 3 PADIWA (shaping, amplification, discrimination) photons, while the FPGA-driven pulses are ]) with a PaDiWa as frontend card, both developed by GSI in 9 2 ] and the other design directly uses the FPGA that forms the 1/2 1/4 1/8 1/2 1/4 1/8 1/16 1/16 11 nlgDgtlEthernet Digital Analog Resistive Splitter Resistive Splitter 10 ns and emit 10 < PMT 0 PMT 1 sDOM Schematic diagram of the sDOM electronics. The colors code parts the were produced in house . 1 Each SDOM uses two R12199 PMTs, one glued inside the top and one inside the bottom The main functional element of the POCAM is an LED flasher with 12 channels (6 per hemi- Darmstadt. The PaDiWa takes care of shaping,is amplification and operated discrimination, as while the TDC TRB3sc photoelectrons unit with for the least measuring attenuated arrival channel,detect while times the after-pulses and channels and with ToT. stronger pulses The attenuationOdroid with system only C2 higher is single photon sensitive board multiplicity. to computerview single running of The the DABC readout sDOM [ signal is chain controlled can be via viewed an in Fig. The MJBs in turn areobservatory daisy using chained wet-matable and ODI connected cables.Fig. to The a details main of Junction the Box mechanical of structure the are ONC shown Neptune in hemisphere, with optical gel. Each PMT is1/4, connected 1/8 to and a 1/16 resistive that splitter connects witha the output Trigger ratios attenuated Read-out of pulses board 1/2, into (TRB3sc, the [ readout system. The DAQ is based on (blue), provided by GSI (green), and bought off the shelf (red). sphere) using two different methods ofby producing short the (ns one timescale) of light pulses.central J.S. element One Kapustinsky of is [ the inspired POCAM electronicsthe by FPGA driving the output LED signals. with anand Five amplified 605 different version nm LED of have one types been of used. withfixed The central FWHM light wavelengths of pulses 365, generated 400, using 465, thejustable faster in 525 Kapustinsky length design and have therefore a allowfeature for of emitting the even more POCAM intense is flashes. theLED Another light isotropy main using of design a the semi emitted transparent lighters PTFE pulse. that integrating This simultaneous sphere is and emit achieved by lightwith by using deviations into diffusing two only the two synchronized on flash- hemispheres the order that of sum 5%. up to an overall isotropic profile Figure 2: STRAW PoS(ICRC2019)890 can be C. Fruck T L 4 Illustration of the light attenuation measurement over different baselines with STRAW. The blue s after the direct peak. µ The two main quantities STRAW was built for measuring are the light background at the bot- The sDOM units are operated as standalone instruments, each with it’s own local DAQ, con- Figure 3: dots represent the POCAMsthe that sDOMs act that as allow preciselyphasogram to calibrated (histogram measure of pulsed the the light photon precise arrivalphotons sources times arrival emitted and folded by time with the the of the POCAM yellow exact as photonsin frequency dots a on the of pileup are phasogram the of at flasher) hits shows the at reveals that the two aaway the certain from PMT PMTs phase the facing (left (upper flasher the right). side). flasher only Alengths receives measures zoom-in mostly (lower A scattered onto direct right). the photons light, peak that while The arriveand the phasogram at 4 PMT the also facing detector shows taking the detours after-pulsing of distribution varying of the PMTs, between 0.5 tom of Cascadia Basin and theour measurement attenuation techniques length and for show Cherenkov some light. preliminary results. In this The attenuation section length we describe trolled via ssh connection over ethernet,The CTS but is synchronized located through inside a one centrallocal of timing clocks the inside MJBs system at the (CTS). the sDOM bottom TRBs. of each string and can be used to reset3. the First measurements STRAW PoS(ICRC2019)890 . det A (3.1) C. Fruck between r (left). The 3 . . det A ) T r L − ( 5 exp is the number of initially emitted photons and ]. First preliminary results for the four Kapustinsky 0 2 r 0 N 10 [ π N 4 ) = r emcee ( N . The second main purpose of STRAW is the measurement of the 5 for example). Uncertainties on the other parameters can be treated as nuisance 4 Measurement (black data points) compared to model prediction (colored dots) for the 465 nm , right). The fraction of POCAM flashes resulting into a hit recorded with an sDOM can be 3 parameters in a fit, a parametereter scan space or, using as the it python has package been done here, a MCMC sampling of the param- is the detector area. POCAMs are neither included intrigger the for timing the system readout. of They simply thewhile emit sDOMs the at nor a sDOMs do fixed are they predefined constantly frequency emitfrom recording on an bioluminescence. the the electronic order In arrival of order times a to of fewbackground separate kHz all events, hits a photons, that phasogram including is can background generated beand by associated folding filling with all POCAM them time flashes stamps into from intoexactly a a correct single histogram. timing flasher phase over This a(Fig. technique flat background reveals from a dark pileup noise,compared of radioactivity to a photons and model bioluminescence arriving calculation that with takesprofiles the into and account photon the geometry, detection angular efficiencies, emission/acceptance eter where the (see attenuation Fig. length is treated as a free param- light background from bioluminescence and radioactive decays.with STRAW This by background constantly can monitoring be the measured rates in all 10 sDOM PMTs. The single photo-electron Figure 4: POCAM LED at 12 V Kapustinsky bias. determined through the following relation if The geometry of STRAWthe allows light that sources quantity (POCAMs) to and be the measured detectors at (sDOMs), different as distances it is illustrated in Fig. driven LEDs are shown in Fig. STRAW PoS(ICRC2019)890 6 C. Fruck ] are given for reference. 9 6 ] and for the ANTARES site [ 14 First preliminary result of the attenuation length measurements for the four LEDs that are con- We have presented the design and first measurement results of the STRings for Absorption length in Water (STRAW) experiment,Ocean in the front of first Vancouver Island, of Canada for aof evaluating the a series Cascadia large Basin of scale as possible pathfinder neutrino future telescope.by site missions Ocean This Networks in Canada, site the providing benefits power and Pacific form datalong already connection strings, ready existing to infrastructure each hook installed up. equipped The withless two 120 five than m optical one modules year. haveof been the All designed, system, data built less and shown then deployedpreliminary in in version one this of year article the after have analysis thethe been software, planning deployment. of recorded encourage the All further after first data, exploration phase full of of despite commissioning a the only future site, evaluated neutrino using including telescope. a 4. Summary as an example shows theThese hourly data average can of be the used ratesthus for in for predicting all designing the PMTs a accidental multiplicity for triggertaining trigger the a rate that whole reasonably in helps month low a keeping energy of future this threshold. March. time neutrino rate Apart resolution telescope low from and an enough, this long main while up-time, technical stillthe they purpose, main- Cascadia could given Basin also the site. be high used in a study of bioluminescent animals at Figure 5: nected to Kapustinsky flashers.Measurements The in error the bars cleanest sea show waters statistical [ and estimated systematic errors separately. rate for all PMTs ismeasurement logged setup every in 30 terms ms of with PMT close HVs to and 100% discriminator up-time thresholds and since without early changes 2019. to the Fig. STRAW PoS(ICRC2019)890 ,

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r P , 43(8):084001, August 2016. Hourly rates in all 5 sDOM for the whole month of March: (blue) down phasing PMT, (red) up IceCube-170922A alert. 12(03):P03012, 2017. neutrino icecube-170922a. Physics The authors are grateful and appreciative of the support provided by Ocean Networks Canada, [1] The Data Acquistion Backbone Core (DABC)[2] framework. http://dabc.gsi.de/.The Accessed: TRB 09.10.2018. family of FPGA based[3] readout boards.M. http://trb.gsi.de/. G. Accessed: Aartsen 09.10.2018. et al. The IceCube Neutrino Observatory: Instrumentation and[4] Online Systems. M. G. Aartsen et al. Multimessenger observations of a flaring blazar coincident with high-energy [5] M. G. Aartsen et al. Neutrino emission from the direction of[6] the blazarS. TXS Adrián-Martínez 0506+056 et prior al. to the Letter of intent for KM3net 2.0. an initiative of the University ofIn Victoria addition funded in to part their by wholeassisting the team, us Canada in special Foundation integrating for thanks STRAW into Innovation. go thethe to ONC German network Jeannette infrastructure. Research Bedard This Foundation and work through is Rossand supported grant Particle Timmerman by SFB Physics” for 1258 and “Neutrinos the cluster and of Dark excellence Matter “Origin in and Structure Astro- of theReferences Universe”. Figure 6: phasing PMT. The nearly daily modulation observedstudy is is most probably on-going. due to the Ocean’s tides. A correlation Acknowledgments STRAW PoS(ICRC2019)890 , C. Fruck Nucl. Phys. Proceedings of 35th Nuclear Instruments and , D42:3613–3620, 1990. Phys. Rev. , page 934, Bexco, Busan, Korea, August 8 , 23(1):131–155, February 2005. arXiv: astro-ph/0412126. , 7:263–282, 1997. , 20(2):177–184, January 1981. , 241(2):612 – 613, 1985. Astroparticle Physics Astropart. Phys. Applied Optics telescope. 2017. Sissa Medialab. nm). results. 125:306, March 2013. Methods in Physics Research Section A:Equipment Accelerators, Spectrometers, Detectors and Associated 27:385–394, 1961. Precision Optical CAlibration Module for IceCube-Gen2:International First Cosmic Prototype. Ray Conference In - PoS(ICRC2017) [9] ANTARES collaboration. Transmission of light in deep sea water at the site of the Antares neutrino [8] I. A. Belolaptikov et al. The Baikal underwater neutrino telescope: Design, performance and first [7] J. Babson et al. Cosmic Ray Muons in the Deep Ocean. [14] Raymond C. Smith and Karen S. Baker. Optical properties of the clearest natural waters (200-800 [10] D. Foreman-Mackey, D. W. Hogg, D. Lang, and J. Goodman. emcee:[11] The MCMCJ.S. Hammer. Kapustinsky , et al. A fast timing light pulser for scintillation detectors. [12] M. A. Markov and I. M. Zheleznykh. On high energy neutrino physics in cosmic rays. [13] Elisa Resconi, Kai Krings Martin Rongen, Kai Krings, and IceCube-Gen2 collaboration. The STRAW