CERN Courier July/August 2016 History COMSOL MULTIPHYSICS ® APPLICATION BUILDER DUMAND and the origins MULTIPHYSICS of large neutrino detectors APPLICATION FOR EVERYONE The evolution of computational tools for Forty years ago at a workshop in Hawaii, numerical simulation of physics-based systems has reached a major milestone. many of the concepts underlying today’s Custom applications are now being developed deep-underground and underwater neutrino by simulation specialists using the Application Builder in COMSOL Multiphysics®. detectors were formulated. John Learned With a local installation of COMSOL Server™, applications can be deployed within an entire organization and accessed worldwide. and Christian Spiering describe how the Make your organization truly benefit from the power of analysis. event laid the foundations for some of the great comsol.com/application-builder discoveries in neutrino physics. © Copyright 2016 COMSOL. COMSOL, COMSOL Multiphysics, Capture the Concept, COMSOL Desktop, COMSOL Server, LiveLink, and Simulation for Everyone are either registered trademarks or trademarks of COMSOL AB. All other trademarks are the property of their respective owners, and COMSOL AB and its subsidiaries and products are not affiliated with, endorsed by, sponsored by, or supported by those trademark owners. For a list of such trademark owners, see www.comsol.com/trademarks In 1976, neutrinos did not yet have the prominent role in particle physics that they play today. Postulated by Pauli in 1930, they had been said to be undetectable due to their tiny interaction probability, and were only fi rst observed in the mid-1950s by Fred Reines and Certified according ISO 9001 Clyde Cowan using a detector located close to a military nuclear reactor. In 1962, researchers at Brookhaven National Laboratory discovered a second type of neutrino, the muon neutrino, but Certified according the third (tau) neutrino would not be seen directly for a further PED 38 years. On the other hand, the theory of electroweak interac- tions mediated by the W and Z bosons was fi rming up, and meas- Certified according urements of neutrinos played a signifi cant role in this context. ATEX/IECEX The fi rst naturally generated neutrinos, originating from cosmic- ray collisions in the Earth’s atmosphere, were observed in 1965 in Cover art from the DUMAND conference proceedings, showing Please visit us deep gold mines located in South Africa and India. Also in the the basic undersea neutrino-detection principle. (Image credit: at our new website: late 1960s, Ray Davis was beginning his famous solar-neutrino Rene Donaldson, Fermilab.) www.weka-ag.ch observations. The time was right to start thinking seriously about neutrino astronomy. DUMAND took place at a cosmic-ray conference in Denver, Colorado, in 1973, which led to a preliminary workshop at Western Enter DUMAND Washington University in 1975. It was at this meeting that the detec- Oil & gas industry Liquefaction of gases Chemical industry Plans that ultimately would shape the present-day neutrino indus- tion of Cherenkov radiation in water was chosen as the most viable Petro industry Gas recirculation systems Pharma industry try blossomed in September 1976 at a meeting in Waikiki, Hawaii. method to “see” neutrino interactions in a transparent medium, with Shipbuilding industry Hydrogen infrastructure Hydrogen infrastructure It was here that some of the fi rst ideas for large detectors such as the some deep lakes and the ocean near Hawaii considered to be good Energy production Space infrastructure Space infrastructure WEKA AG · Schürlistrasse 8 gigaton DUMAND (Deep Underwater Muon and Neutrino Detec- locations. This detection principle goes back to Russian physicists Water management Plasma & fusion research Energy production CH-8344 Bäretswil · Switzerland tor) array, which eventually morphed into the present-day IceCube Moisey Markov and Igor Zheleznykh in 1960: water provides the Phone +41 43 833 43 43 experiment at the South Pole, were envisioned. The technology target for neutrinos, which create charged particles that generate a Level Measurement Cryogenic Components Valve Technology Fax +41 43 833 43 49 for smaller water-fi lled detectors such as IMB (Irvine–Michigan– fl ash of light in approximate proportion to the neutrino energy. The [email protected] · www.weka-ag.ch Brookhaven) and, later, Kamiokande in Japan, were also laid out water also shields the many downward-moving muons from cosmic- in detail for the fi rst time. Moreover, totally new concepts such as ray interactions in the atmosphere. With light detectors, such as a ARCA Flow Group worldwide: particle detection via sound waves or radio waves were explored. basketball-sized photomultiplier tube, one could register the light ▲ Competence in valves, pumps & cryogenics The first organised stirrings of what was to become fl ash over large distances. 25 CERNCOURIER www. V OLUME 5 6 N UMBER 6 J ULY /A UGUST 2 0 1 6 CERN Courier July/August 2016 CERN Courier July/August 2016 History History IceCube IceCube lab IceTop 50 m Anatoly Pethruhkin IceCube 1450 m Amanda DeepCore Eiffel Tower 324 m 2450 m 2820 m Attendees of the 1976 workshop, showing Fred Reines (back, second from left) and one of the present authors, JL (back, third from left). Other attendees included theorist Venyamin Berezinski; cosmic-ray experts Alexander Chudakov, Boris Dolgoshein and Anatolij Petrukhin from Moscow; Saburo Miyake (founder of ICRR in Tokyo, later home of Kamiokande); and astronomer G A Tamman. US particle-physicists Ted Bowen, Sidney Bludman, David Cline, Marshall Crouch, Howard Davis, Richard bedrock Davisson, Vernon Jones, Peter Kotzer, Ken Lande, Karnig Mikaeilian, M Lynn Stevenson, Larry Sulak and Dave Yount were joined by astronomers and astrophysicists David Schramm, Ivan Linscott, Rein Silberberg and Craig Wheeler. The original DUMAND project (left), which was cancelled in 1995, and the present-day IceCube experiment located at the South Pole (right). Although there are no formal links between the two experiments, their confi gurations bear strong similarities. The vision of building devices larger than any yet dreamed about, activity appeared practical for detecting neutrinos. For the bursting and placing them in the deep ocean to study the cosmos above, neutrino sources, galactic gravitational collapses clearly yielded tion dynamics were not well defi ned at the highest energies. design of the optical detectors became paramount. One group of attracted many adventurous souls from around the US and else- the most available total power for neutrinos. The others – namely By the end of the Hawaii workshop, which lasted for two weeks, attendees from the 1976 workshop aimed for the use of wavelength where, a number of whom dedicated years to realising this dream. type I supernovae, solar fl ares, gamma- and X-ray bursts and mini- everyone considered low-energy neutrino detection to be the most shifters that absorb blue light and re-emit green light, allowing One of us (JL) joined Reines, along with Howard Blood of the US black-hole evaporation – did not seem to have enough power and worthwhile cosmic-neutrino-detection goal. Aside from solar neu- the use of modest photodetectors, while another pushed for the navy and other ocean-engineering aficionados – in particular, proximity to be competitive. Even today, these sources have not trinos, it was also agreed that neutrinos from supernova collapses development of photomultipliers larger than the 25 cm-diameter George Wilkins, who was responsible for the fi rst undersea fi bre- been observed in terms of neutrinos. were the most likely to be seen (as they later were in 1987, when versions available at the time – as did in fact transpire. The one seri- optic cables. Inventor of the wetsuit and former bubble-chamber There was also great interest in targeting high-energy (TeV and a burst of neutrinos was observed by the IMB, Kamiokande and ous alternative to optical Cherenkov light detection, building on a developer Hugh Bradner became another driving force behind the above) neutrinos, but predictions of the strengths of the potential Baksan detectors). But it was also realised that this effort requires concept developed by Gurgen Askaryan in 1957, was to utilise the project. Theorists, cosmic-ray experts, particle physicists, astrono- sources were plagued by huge uncertainties. It was known that kiloton detectors with threshold sensitivities of about 10 MeV to pulse of sound made by neutrino progeny after neutrino collision mers and astrophysicists all played important roles (see photograph the number of cosmic rays impinging upon the Earth decreases as guarantee a few supernovae per century. Regarding the detection with a nucleus of water or another medium such as ice. above). The event captured a spirit of adventure and worldwide co- a function of energy up to values of around 1020eV, whereupon the of high-energy neutrinos in the TeV range, as expected from accel- Following the 1976 event, annual neutrino workshops were operation, particularly concerning interactions between US and spectrum was predicted to show a cut-off known as the Greisen– eration processes in galactic and extragalactic objects, everyone held for about a decade, eventually blending with DUMAND col- Soviet colleagues, and the special nature of our unusual international Zatsepin–Kuzmin (GZK) limit caused by high-energy protons understood the necessity of detectors in the megaton to gigaton laboration meetings. The 1978 workshop, held in La Jolla,