25 years of successful R&D experiences on cryogenics and purification ICARUS 25 years of successful R&D experiences on cryogenics and purification Claudio Montanari INFN-Pavia, Italy Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

The ICARUS Collaboration M. Antonello1, B. Baibussinov2, V. Bellini4,5, H. Bilokon6, F. Boffelli7, M. Bonesini9, E. Calligarich8, S. Centro2,3, K. Cieslik10, D. B. Cline11, A. G. Cocco12, A. Curioni9, A. Dermenev13, R. Dolfini7,8, A. Falcone7,8, C. Farnese2, A. Fava3, A. Ferrari14, D. Gibin2,3, S. Gninenko13, F. Guber13, A. Guglielmi2, M. Haranczyk10, J. Holeczek15, A. Ivashkin13, M. Kirsanov13, J. Kisiel15, I. Kochanek15, A. Kurepin13, J. Łagoda16, F. Mammoliti4, S. Mania15, G. Mannocchi6, V. Matveev13, A. Menegolli7,8, G. Meng2, G. B. Mills17, C. Montanari8, F. Noto4, S. Otwinowski11, T. J. Palczewski16, P. Picchi6, F. Pietropaolo2, P. Płoński18, R. Potenza4,5, A. Rappoldi8, G. L. Raselli8, M. Rossella8, C. Rubbia19,14,a, P. Sala20, A. Scaramelli20, E. Segreto1, D. Stefan1, J. Stepaniak16, R. Sulej16, C. M. Sutera4, D. Tlisov13, M. Torti7,8, R. G. Van de Water17, F. Varanini3, S. Ventura2, C. Vignoli1, H. G. Wang11, X. Yang11, A. Zani7,8, K. Zaremba18 INFN, LNGS, Assergi (AQ), Italy 1), INFN, Sezione di Padova, 35131 Padova, Italy 2), Dipartimento di Fisica, Università di Padova, 35131 Padova, Italy 3), INFN, Sezione di Catania, Catania, Italy 5), INFN, Laboratori Nazionali di Frascati (LNF), 00044 Frascati (Roma), Italy 6), Dipartimento di Fisica, Università di Pavia, 27100 Pavia, Italy 7), INFN, Sezione di Pavia, 27100 Pavia, Italy 8), INFN, Sezione di Milano Bicocca, Dipartimento di Fisica G. Occhialini, 20126 Milano, Italy 9), The H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Science, Kraków, Poland 10), Department of Physics and Astronomy, University of California, Los Angeles, USA 11), INFN, Sezione di Napoli, Dipartimento di Scienze Fisiche, Università Federico II, 80126 Napoli, Italy 12), INR-RAS, Moscow, Russia 13), CERN, Geneva , Switzerland 14), Institute of Physics, University of Silesia, Katowice, Poland 15), National Center for Nuclear Research, Warszawa, Poland 16), Los Alamos National Laboratory, New Mexico, USA 17), Institute for Radioelectronics, Warsaw University of Technology, Warsaw, Poland 18), GSSI, L’Aquila (AQ), Italy 19) , INFN, Sezione di Milano, 20133 Milano, Italy 20) Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Foreword The practical implementation of the LAr TPC technology on increasingly larger scales required an intense R&D on several, non trivial, subjects: Argon purification; Uniformity of temperature and purity; Mechanical reliability of the wire chambers; Very high reliability of the design and of the equipment for safety and long term operation. All these subjects had to be developed in a coherent and, most important, cross-compatible way. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

The path to larger LAr detectors CERN 1 2 CERN Laboratory work 3 CERN Icarus T600 experiment 4 2010-2013: Data taking with C-rays and CNGS beam Pavia T600 detector Cooperation with industry: AirLiquide, Breme, Cinel, CAEN 20 m 2001: First T600 module 6 5 LNGS Hall-B

Argon purification: choice of filters At the very beginning of our development on LAr purity, in 1987, we have identified the most effective filters for Argon purification as a combination of Oxysorb (Chromium) and Hydrosorb (Molecular sieves 4A/13X). Oxysorb has the largest attachment energy for Oxygen among the most commonly used adsorbants; Hydrosorb, placed before Oxysorb, efficiently removes water, preserving the Oxysorb adsorption efficiency for Oxygen and other electronegative impurities. After more than 25 years of R&D we still consider the above solution as the best choice both for liquid and for gas Argon purification. Oxysorb Argon Flow Hydrosorb Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: Argon containment Vacuum tightness is a mandatory requirement to attain high LAr purities. We employ ConFlat flanges or welds for all connections. For the new main LAr containers we have chosen a double walled structure made of Aluminum extruded profiles. Aluminum couples lightweight with good thermal conductivity and electrical shielding. The double wall structure ensures a safe LAr containment and an effective leak tightness (both walls are tight). We require: a global Helium leak tightness a factor 10 lower than the expected outgassing rate (< 10-6 mbar•liters/s); a localized Helium leak tightness below the detection limit (< 10-8 mbar•liters/s). Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: materials selection All the materials used for the construction of our detectors were carefully selected considering their mechanical properties at LAr temperature and outgassing composition and rates. Whenever possible we used materials selected for application in space. We performed specific outgassing measurements of plastic components. All materials are cleaned using Ultra High Vacuum standard procedures: pickling and passivation for metals; washing with ultrasounds in demineralized water; drying in vacuum hoven; packaging in dry Nitrogen atmosphere. Prior to their acceptance for use in the T600 detector construction, prototypes of all the components and mechanical assemblies were tested in LAr to verify their compatibility with our purity requirements. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: air removal and materials outgassing Up to the T600 construction we have always considered High Vacuum (molecular regime) as the method to remove air from the volumes to be filled by Argon and to clean the internal surfaces by outgassing. With this method we have been able to ensure High Vacuum tightness and to reach a free electron lifetime in the range of 1 ms just after the detector filling. Pressure evolution in the T600 during the vacuum phase Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: designing for Ultra High Vacuum All T600 detector components were designed using Ultra High Vacuum prescriptions: avoid tapped holes or volumes, minimize contact surfaces, etc.. Already from the T1200 design (2002) we started to consider the idea to replace vacuum with pure argon gas purging. The T1200 detector, and later the one of ModuLAr, was specifically designed to avoid trapped volumes (“open geometry”). Dedicated fluid- dynamic simulations were performed to verify the solutions. Example of a T600 mechanical component Through holes for pins and bolts Lowered surfaces to minimize contact Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: purification in the liquid phase A major step towards the deployment of large volume LAr TPCs has been the demonstration of Argon purification in the liquid phase (1993). During the first test a free electron lifetime > 3-4 ms was reached. Special filter cartridges were subsequently developed, with an LN2 cooling jacket to avoid gas formation and maximize the argon flow. Liquid phase purification test setup Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: gas and liquid recirculation To achieve and maintain the purity levels required for long drift distances (meters) continuous Argon recirculation and purification is required both in the gas and in the liquid phase. Gas recirculation was first implemented in the 3 ton prototype that operated at CERN between 1991 and 1995 with lifetimes consistently above 2 ms. In subsequent versions, the filter of the gas recirculation system was moved after the re-condenser (operating in the liquid phase) to decrease the impedance and therefore the main operating pressure. Liquid recirculation was first developed in the 10 m3 prototype (the T600 prototype) in 1998 allowing to reach, at the first attempt, a lifetime ≈ 3 ms. Subsequent improvements in the argon distribution and in the pumps allowed, in the T600, to improve the lifetime by about a factor 5! Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: achievements in the lab. Future requirements: ele>12 ms with Edrift = 0.5kV/cm for 15% attenuation at 3.0 m, Extremely high ele have been already obtained at lab scale in the ICARINO R&D program where the short path length used (30 cm) is compensated by the accuracy in the observation of the specific ionization of cosmic muons. The result repeatedly reached is  ele > 20 ms corresponding to ≈15 ppt, namely a ≈10-11 molecular Oxygen eq. impurities. These activities were initiated in view of “Modular” Project. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Argon purification: purity in the T600 In the three years of T600 underground operation at the LNGS, electron lifetimes constantly exceeding several ms were obtained. During the last part of this data taking, a free electron lifetime exceeding 15 ms has been achieved. New recirculation pump Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Uniformity of temperature and purity: cooling circuit To fully exploit the performances of the LAr TPC, a high degree of uniformity in the liquid volume is required. Temperature uniformity ensures that the drift velocity is constant over the sensitive volume. Some convection is necessary for an adequate mixing of the liquid and therefore a uniform LAr purity. Our requirements for the T600 were a temperature uniformity of 1 °C all over the LAr volume. This implies de-stratification of the liquid and therefore a significant internal convection. In the T600 we have implemented a cooling shield completely surrounding the two Aluminum containers. The shield is used both during the initial cool down and during steady state operation. In steady state Nitrogen is circulated through the shield in two phases at pressure of ≈ 2.3 bara. The shield intercepts all the thermal losses through the insulation. The heat coming from the cables on the top powers the gas recirculation system that is also used to stabilize the Ar pressure. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

T600 P&I (Nitrogen scheme) LN2 for main LAr volume cooling (thermal shields) – Bi-phase (1/5 - gas to liquid - mass) – 87 K LN2 for LAr reciculation – Single phase – 84 K LN2 Gravity driven cooling (emergenecy only – for the moment) – 87 K – double phase Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Uniformity of temperature and purity Thanks to the highly performing cooling system, the internal temperature was kept uniform to less than 0.25 K for more than three years. Temperatures in several positions inside the T600 During the whole run at LNGS we never measured significant differences in free electrons lifetime across the sensitive volume of each aluminum container. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Pressure stability Also the absolute pressure inside each LAr container remained exceptionally stable Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

New Thermal Insulation Slide 18 Purely passive insulation chosen for the new T600 installation, coupled to our standard cooling shield with boiling Nitrogen. Technique developed for 50 years and widely used for large industrial storage vessels and ships for liquefied natural gas. Expected heat loss through the insulation: T600 ≈ 6.6 kW ; T150 ≈ 3.5 kW Preliminary design appointed to GTT in Jan 2013 No internal membrane is required for our case ICFA Meeting = January 2014

New T600 layout Warm vessel + External skin Insulation + T600 modules Insulation top Top flanges (final layout) ICFA Meeting = January 2014

Mechanical reliability of the wire chambers One of the main issues of the LAr TPC technology is to ensure that none of the tens of thousands of wires will brake during cool down, filling with LAr or during operation. In the T600 we achieved this goal by: implementing the variable geometry concept on wire chambers design; using a high degree of modularity in the mechanics; adopting high precision mechanics and rigid quality standards; defining a careful and highly controlled cool down procedure. The whole process was finally validated in a test run with the 10 m3 prototype. In the T600 the cool down was performed in such a way to keep the thermal gradients on the wire chamber within 50 K. It took about 8 days to cool the T600 from room temperature to 90 K. The movement on the wire frames was < 30 µm. No broken or loosen wire out of about 55000. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Mechanical reliability of the wire chambers: detector cooling Temperatures on the wire chambers during the cool down Start gas recirculation LAr filling LAr filling Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

High reliability of the cryogenic plant Both for safety reasons and for long term operation of the detector the cryogenic and purification plants have to provide an extremely high reliability. In the T600 we achieved this goal by: careful design; implementing a high level of installed and ready to start redundancy of all the critical equipment; acquiring spare components of most of the non critical parts. During all the T600 run at LNGS we never had to stop the detector operation even in presence of severe power cuts and some equipment failure. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Conclusions Several years of R&D, design, prototyping and tests were required to bring the LAr TPC technology from gedanken to experiment. A significant fraction of the R&D was dedicated to cryogenics and to LAr purification. The ICARUS has accumulated an enormous amount of know how in these areas and will continue to do so in the future. The performance of the T600 at LNGS was more than satisfactory and do not consider necessary any significant variation for the future T600 implementation, with the exception of thermal insulation and of the main LAr containers. The importance of the INFN contribution during all these years of activity cannot be overstated. Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014

Thank you ! LNGS_May2011 Slide 24 Neutrino Cryogenic Requirements Meeting – CERN - September 24, 2014