1. LSc experiment set-up and research results LAGUNA 2014 Hanasaari, August 25, 2014 Wladyslaw H. Trzaska

2. Key requirements for LENA* (as defined at the start of LAGUNA-LBNO) To fulfill the scientific program (White Paper) – Very broad research scope: astroparticle physics, proton decay, geo-neutrinos, LBNO (MH & CPV) To reach/cross the discovery threshold To make a significant improvement over the ongoing large (≤ 1 kton) LSc experiments – BOREXINO, KamLAND, SNO+ LAGUNA 2014W.H.Trzaska2

3.  Design baseline* (as defined at the start of LAGUNA-LBNO) LAGUNA 2014W.H.Trzaska3 Size ~50 kton x 10 years = 0.5 Mton years – Size limit for a single tank LSc detector? Transparency issues? Shape optimization? ~4000 m.w.e. overburden  site selection – Cavern size limit at that depth? BOREXINO-grade radio-purity (Solar neutrinos) Low reactor anti-neutrino background (geo-neutrinos)

4. * Important footnotes Due to the limited time and resources allocated to the LAGUNA-LBNO Design Study, the Design Baseline for LSc had to be frozen already in the beginning of 2012 At the same time spectacular success of the running experiments and approval of the new large-sized LSc-based neutrino detectors have generated a steady stream of technological advancements opening new research opportunities for such detectors LAGUNA 2014W.H.Trzaska4

5. LSc detectors in operation under construction KamLAND (1 kton) since 2002 Borexino (0.3 kton) since 2007 Double Chooz since 2011 Daya Bay since 2011 RENO since 2011 SNO+ (1 kton) expected 2014 JUNO (20 kton) expected ~2020 RENO 50 (5  18 kton) expected ~2020 LAGUNA 2014W.H.Trzaska5

6. LAGUNA 2014W.H.Trzaska6 sin 2 2θ 13 with LSc Daya Bay should improve sin 2 2θ 13 precision from 14%  3% in 3-5 years!

7. LAGUNA 2014W.H.Trzaska7 20 kton LSc @ 60 km from ~36 GW (thermal) MH (4σ in 6 years if Δm 2 xx ≈ 1%) Precision measurement of mixing parameters – Δm 2 12 3%  0.6% – Δm 2 23 5%  0.6% – sin 2 θ 12 5%  0.7% SN Geo-neutrinos Sterile neutrinos

8. LAGUNA 2014W.H.Trzaska8 Why Liquid Scintillator? The lowest energy threshold High cross section & BGD-free IBD ~50 time more light than water Cherenkov – Performance / total cost ratio Robust construction Low running costs Significant advancements in signal processing and electronics Developments in photo sensor technologies Well suited for DAEδALUS approach (δCP with small accelerators)

9. Key elements of LSc detector Overburden Liquid scintillator (LAB + additives) Transparent buffer separating light sensors (PMTs) from LSc Enclosure (tank) Active water pool Muon tracker/veto detector LAGUNA 2014W.H.Trzaska9

10. Schematic drawing of the inner part of a small-size LSc detector LAGUNA 2014W.H.Trzaska10 Daya Bay

11. LAGUNA 2014W.H.Trzaska11 One of the experimental halls at Daya Bay: 4 LSc modules in a water pool

12. LAGUNA 2014W.H.Trzaska12 Photo of RENO LSc module and the surrounding water vessel

13. LAGUNA 2014W.H.Trzaska13 Photo of Double Chooz inner detector before placement of lid on buffer tank

14. LAGUNA 2014W.H.Trzaska14

15. LAGUNA 2014W.H.Trzaska15 Optical Module Prototype for LENA (no need for inner vessel) The size would be comparable to PMTs with light concentrators used at Borexino As inner vessels for LENA were considered potential show stoppers, we have proposed OM approach

16. JUNO LAGUNA 2014W.H.Trzaska16

17. LAGUNA 2014W.H.Trzaska17 Primary option proposed for the 20 kton LSc (JUNO): A 35 m diameter acrylic sphere supported by a SS truss that will also hold PMTs

18. LENA Design Studies Pre-feasibility Study TUM (till 26/05/2008) Feasibility Study TUM (till 12/04/2010) LAGUNA Design Study EU (2008 – 2011) LAGUNA–LBNO Design Study EU (2011 – 2014) LAGUNA 2014W.H.Trzaska18  Evolution of the Classic Design of LENA In-depth report on the D3.1 LSc detector instrumentation design & costing was presented during the June 2013 LAGUNA-LBNO General Meeting at CERN: https://laguna.ethz.ch/indico/conferenceOtherViews.py?view=standard&confId=11

19. LAGUNA 2014W.H.Trzaska19 Reevaluation* of the concept of the 50 kton LENA Excellent physics & sound design, but too expensive to be realized without a broad support (only astro-particle physics is not enough) Demonstrated sensitivity for MH with CN2PY beam, but too small to compete in that field Suitable for δCP with DAEδALUS, but too small for a decisive measurement Start of the JUNO (20 kton) made the plans for a 50 kton LENA less attractive and harder to justify Solution: a larger LENA!

20. LAGUNA 2014W.H.Trzaska20 What is the size limit for Liquid Scintillator detector? Limiting factors – Cavern size at the required depth (in Pyhäsalmi D max at 1400m is ~102 m by ~64 m) – Transparency of LSc (att. length of purified LAB λ = ~20 m) – Cost LSc @ 2 M€ per kton (possible to resell)* PMT @ 2 k€ per encapsulated unit*

21. LAGUNA 2014W.H.Trzaska21 Shape optimization to maximize the size of a Liquid Scintillator detector Sphere (R = λ = 20 m) – 33,500 m 3  29/21 kton Compact cylinder (H = 2R = 40 m) – 50,300 m 3  43/31 kton Tall cylinder (H > 2R; H = 100 m) – 125,700 m 3  108/84 kton Flat cylinder (2R > H = 40m; 2R=102/64 m) – 205,000 m 3  177/143 kton JUNO LENA SuperK HELENA

22. LAGUNA 2014W.H.Trzaska22 Horizontal stress in Scandinavian rock: 200 000 m 3 cavern is needed for a 50 000 m 3 cylindrical tank

23. LAGUNA 2014W.H.Trzaska23 Dimensions of the largest proposed cavern (in Pyhäsalmi at 1400 m) Protvino axis 102 m CERN axis 64 m Height 38 m Dome 12.5 m Cavern volume (w/o dome) = 195 000 m 3 π⁄4 × 64m × 102m x 38m

24. Since it is not possible to excavate a cavern to suit the detector, let’s suit the detector to the cavern! LAGUNA 2014W.H.Trzaska24

25. LAGUNA 2014W.H.Trzaska25 All caverns in Pyhäsalmi have to be elliptical

26. LAGUNA 2014W.H.Trzaska26 Steel lining may be fixed directly to the cavern wall and the entire volume filled with LSc! Cavern volume (w/o dome) = 195 000 m 3 π⁄4 × 64m × 102m x 38m Fiducial volume (with 2 m perimeter) = 157 000 m 3 π⁄4 × 60m × 98m x 34m @ 0.863 kg/l ~ 135 kton LAB (fiducial mass) without a tank 50 kton LENA  135 kton SuperLENA (HELENA): High Energy neutrinos Low Energy neutrinos Neutrino Astronomy Do we really need a free-standing, cylindrical tank?

27. LAGUNA 2014W.H.Trzaska27 Liquid distribution within HELENA cavern HELENA LSc 169 kton total 135 kton fiducial(2 m perimeter) HELENA would have no water pool as this function would be covered by the external layer of the scintillator. The external and the central volume would be optically separated LENA HELENA

28. LAGUNA 2014W.H.Trzaska28 HELENA would reuse LENA solutions Mirror surface Bottom PMTs On the inside LENA has OMs on a 0.55 m grid:  3.3 PMT / m 2 On the outside a 2.25 m grid:  0.2 PMT / m 2 LENA-type Optical Modules with build-in passive buffer Exception: no OM on the inner wall! Replaced by a reflective surface

29. LAGUNA 2014W.H.Trzaska29 Optical Modules only on the TOP and BOTTOM 50 kton LENA 31 646 PMTs for the inner volume 2 024 PMTs for the outer volume 33 670 PMTs TOTAL 135 kton HELENA 30 480 PMTs for the inner volume (top & bottom) 3 582 PMTs for the outer volume 33 062 PMTs total

30. LAGUNA 2014W.H.Trzaska30 Steel lining solution from LENA would be applied directly to the cavern wall of HELENA In LENA this is the concrete tank In HELENA this would be the cavern wall

31. LAGUNA 2014W.H.Trzaska31 Proposed wall treatment for HELENA The cavern will be shotcreted and fixed with 400 mm spaced steel fixtures for welding of 12mm thick steel sheets – the solution proposed for inner surface of the concrete tank for LENA In addition, the cavern walls behind the steel sheets will be sprayed with rubber compound sealer as an additional precaution against leaks

32. Conclusions Because of the very rapid developments in the field of LSc detectors (JUNO, RENO 50) the LAGUNA-LBNO Design Baseline for LSc option (frozen in early 2012) needs to be updated To make it attractive and to capitalize on the work done by the Industrial Partners, the current LSc evaluation would have to be extended to the 135 kton option (HELENA) In particular, cost & construction time of HELENA would have to be evaluated A rough estimate indicates that nearly 3 fold increase in the fiducial mass would increase the total cost of the project by about 50% As one of the most time consuming elements of the design would be eliminated (concrete tank) the construction time for HELENA is expected to be comparable to LENA or even shorter LAGUNA 2014W.H.Trzaska32

33. LAGUNA 2014W.H.Trzaska33 Thank you for your attention! Any questions?

34. To put things in the right perspective: LAGUNA 2014W.H.Trzaska34

35. Current choice for LENA: R11780 12” PMT LAGUNA 2014W.H.Trzaska35 In addition to Hamamatsu, ADIT Electron Tubes from UK/USA, and a Chinese manufacturer involved in Daya Bay II experiment are expected to enter the competition. Needed: 34,000 PMTs Current cost: 1.4 k€ / PMT

36. Latest developments I: APD-based PMT LAGUNA 2014W.H.Trzaska36 Courtesy: Hyper-K

37. Latest development II: MCP-based PMT LAGUNA 2014W.H.Trzaska37 SBA photocatode New type of PMT: MCP-PMT Courtesy: DayaBay II

38. Optical Module Prototype LAGUNA 2014W.H.Trzaska38 Current cost estimate(12” Hamamatsu): ~1400€ PMT + 500€ encapsulation/PMT