1. Mark Vagins Kavli IPMU, University of Tokyo Open Meeting for the Hyper-Kamiokande Project Kashiwa August 23, 2012 Gadolinium Option for Hyper-K: World-class Water

2. Theorist John Beacom and I wrote the original GADZOOKS! (Gadolinium Antineutrino Detector Zealously Outperforming Old Kamiokande, Super!) paper. It proposed loading big WC detectors, specifically Super-K, with water soluble gadolinium, and evaluated the physics potential and backgrounds of a giant antineutrino detector. [Beacom and Vagins, Phys. Rev. Lett., 93:171101, 2004]

3. e can be identified by delayed coincidence. e e+e+ 2.2 MeV  -ray p n Possibility 1: 10% or less n+Gd → ~8MeV   T = ~30  sec Possibility 2: 90% or more   Positron and gamma ray vertices are within ~50cm. n+p →d +  p Gd Basically, we said, “Let’s add 0.2% of a water soluble gadolinium compound to Super-K!”

4. Gadolinium in Hyper-Kamiokande Originally conceived as a Super-K upgrade, the true power of gadolinium loading would be uniquely realized in Hyper-K: With Gd, proton decay backgrounds would be reduced between 50% and 80%, which will become important at the Mton*year exposure level, particularly for p  e + +  0. o(100) DSNB events/year (+ mini-bursts) would provide spectral information, yielding the average SN’s energetics, as well as the universe’s supernova history and dark SN rate. [S. Horiuchi] In addition to other benefits [Y. Koshio], in the case of a galactic supernova, neutron tagging would allow certain isolation of the early neutronization signal. Only HK with Gd can fully resolve this signal at the galactic center. A Gd-loaded HK provides a strong new WIMP channel. [C. Rott] GADZOOKS! is already on the Japan CRC roadmap. [N. Kanda]

5. Now, to make gadolinum loading work, we will have to: Dissolve the gadolinium sulfate in the water  Easy and fast (pH control) Remove the gadolinium efficiently and completely when desired  Also easy and fast (pH control) Keep pure water pure yet retain gadolinium in solution  The tricky part; need a selective Gd filtration system

6. The Essential Magic Trick → We must keep the water in any Gd-loaded detector perfectly clean… without removing the dissolved Gd. → I’ve developed a new technology: “Molecular Band-Pass Filtration” Staged nanofiltration selectively retains Gd while removing impurities. Amazingly, the darn thing works! This technology will support a variety of applications, such as: → Supernova neutrino and proton decay searches → Remote detection of clandestine fissile material production → Efficient generation of clean drinking water without electricity

7. Electrical Band-Pass Filter

8. Molecular Band-Pass Filter UltrafilterNanofilter Reverse Osmosis Larger and smaller impurities to drain (UF Flush + RO Reject) Pure water (RO product) plus Gd 2 (SO 4 ) 3 Pure water plus Gd 2 (SO 4 ) 3 Gd 2 (SO 4 ) 3 (NF Reject) Gd 2 (SO 4 ) 3 plus smaller impurities (UF Product) Impurities smaller than Gd 2 (SO 4 ) 3 (NF Product) Impurities larger than Gd 2 (SO 4 ) 3 (UF Reject flushed periodically )

9. NF Reject UF Product

10. Band-Pass Window

11. Over the last nine years there have been a large number of Gd-related R&D studies carried out in the US and Japan:

12. Now, ICRR and IPMU (with UCI and OkayamaU) have built a dedicated 200-ton Gd demonstrator project: EGADS – Evaluating Gadolinium’s Action on Detector Systems. EGADS (initial Japanese funding = $4,300,000) Super-K Water system EGADS Hall (2500 m^ 3) Super-Kamiokande EGADS Facility 12/2009 2/2010 6/2010 12/2010 By next year, EGADS will have shown conclusively whether or not gadolinium loading of Super-Kamiokande will be safe and effective. If so, this is the likely future of all water Cherenkov detectors.

13. ;. 11/2011 Hall E and EGADS 200-ton Water Cherenkov Detector (240 50-cm PMT’s) Selective Water+Gd Filtration System 15-ton Gadolinium Pre-treatment Mixing Tank

14. Cherenkov Light Remaining at 20 m (200-ton tank) Within a few months of turning on the system our pure “band-pass” water was as good as Super-K's ultrapure water after 15 years of tuning and adjustments! We then introduced gadolinium into the system…

15. Stable running ~66% light @ 1900 ppm with Amberjet4400, ~63% without Studies continue, but we have already achieved stable light levels of 66% at 20 meters with fully Gd-loaded water. This should be compared to a range of 71%  79% for “perfect” pure water in SK-IV.  No detected Gd loss after >100 complete turnovers. 

16. 16 Multi-messenger Supernova Astronomy: X-ray,  -ray, Optical, Infrared, GW, and Neutrino Approved - June 2012 ~$1.6M for EGADS/IPMU

17. Japan-based Organo has had a near monopoly on major Kamioka water systems for decades  Pluses: They are local and established, can respond quickly  Minuses: Monopoly can lead to high costs, no Gd experience US-based South Coast Water has developed and built many water systems for physics experiments in the US and Japan  Pluses: Lower cost, Gd experience, 35-year partnership  Minuses: Main factory is far from Japan, language issues

18. South Coast Water and its CEO Roy Hall got the contract for EGADS’ main (Gd filtering) water system. They previously built the pure water systems for: IMB, Milagro, E261a/b (the 1994 KEK beam test experiment), K2K’s 1KT detector, and LUX They also operate the fresh air system for SK/XMASS/EGADS. SCW’s ~1000 active accounts include the US Navy, hospitals, semiconductor fabrication plants, and even a few movie stars.

19. Has offered to build a permanent branch office in Japan to provide service and support to Hyper-K Will likely respond positively to serious price competition

20. SCW’s preliminary design for a Hyper-K water filling system Industrial water input RO Pre-treatment and RO To tank: 364 tons/hr = 190 ktons/month Uranium Removal, DI and UV Chiller and Degas

21. SCW’s preliminary design for a modular (one tank) Hyper-K- water recirculation system This design is intended to be easily upgradable for handling gadolinium From detector via RO Back to detector Uranium Removal and DI 0.1 mm and 1.0 mm filters 730 tons/hr = 526 ktons/month

22. We intend to put together a truly world-class water system for Hyper-Kamiokande.  Let’s work together to get it done! 