Gadolinium Update and Roadmap

1. Gadolinium Update and Roadmap Mark Vagins IPMU, University of Tokyo Osawano November 10, 2008

2. The (still informal) GADZOOKS! working group aims to add gadolinium to Super-Kamiokande and gain the many physics benefits provided by efficient neutron tagging: • ICRR – Y. Koshio, M. Nakahata, H. Sekiya, • A. Takeda, Y. Takeuchi, H. Watanabe • IPMU – J. Schuemann, M. Vagins • Madrid – L. Labarga • Okayama – H. Ishino, A. Kibayashi, M. Sakuda • UCI – K. Bays, J. Griskevich, R. Hall, B. Kropp, • M. Smy, H. Sobel If your name is missing and you want to play a meaningful role in this effort, please let me know.

3. Mitsui has performed a new series of stainless steel corrosion tests for us on gadolinium sulfate (Gd2(SO4)3) and GdCl3+NaF. This was paid for with some of my IPMU startup funds. Here’s what I got… ガドリニウム水溶液中におけるSUS304腐食試験　結果報告書 (plus 45 more pages)

4. After another few hundred thousand yen in translation costs… “Report onType304 SS Corrosion Test in the Gadolinium Solution” (plus 45 more pages)

5. Heat Treatment of Stainless Steel Samples (to simulate welding damage) No heating 2 hours @ 650 C 8 hours @ 650 C “non-sensitized” “sensitized” “heavily sensitized” Without Heat Treatment (Non-sensitized material) ＜ Welded Test Piece ＜ 650℃ x 2h (Sensitized material) ＜ 650℃ x 8h (Heavily sensitized material) SK Condition [all samples shown at 100X magnification]

6. (TEST No.2-01) 0.2wt% Not Heat Treated Initiation of Crevice Corrosion No Yes (TEST No.2-03) 2wt% Not Heat Treated Test Completed Initiation of Crevice Corrosion Yes No (TEST No.2-02) 0.2wt% Heat Treated (TEST No.2-04) 2wt% Heat Treated Initiation of Crevice Corrosion Yes (TEST No.2-02) 0.2wt% Heat Treated No Test Completed Flowchart of Mitsui’s Gd2(SO4)3 plan For more details on the tests and methods used, please see Nakahata-san’s dedicated talks at previous SK meetings (e.g., June ’07)

7. Stress Corrosion Cracking Test Stressed samples One month soaking in Gd solution at 60 C

9. Water “Band-pass Filter” GdCl3 or Gd2(SO4)3 (NF Reject) GdCl3 or Gd2(SO4)3 plus smaller impurities (UF Product) Pure water plus GdCl3 or Gd2(SO4)3 from SK Ultrafilter Nanofilter Impurities larger than GdCl3 or Gd2(SO4)3 (UF Reject) Impurities smaller than GdCl3 or Gd2(SO4)3 (NF Product) DI/RO Pure water (RO/DI product) plus GdCl3 or Gd2(SO4)3 back to SK Impurities to drain (RO Reject) [Undergoing testing at UCI]

10. Selective Filtration Prototype Setup @ UCI Deionization Chiller 0.2  5 Micron Filters UV Sterilizer Reverse Osmosis Ultrafilter Nanofilter

11. Since the last SK Meeting we have performed a survey of various filter membranes

12. > 98.5% GdCl3 or Gd2(SO4)3 (single stage NF Reject) Water “Band-pass Filter” 100% of GdCl3 or Gd2(SO4)3 plus smaller impurities (UF Product) Pure water plus GdCl3 or Gd2(SO4)3 from SK Ultrafilter Nanofilter Impurities larger than GdCl3 or Gd2(SO4)3 (UF Reject) Impurities smaller than GdCl3 or Gd2(SO4)3 (NF Product) DI/RO Pure water (RO/DI product) plus GdCl3 or Gd2(SO4)3 back to SK Next we will add another NF stage and see if we can get even better separation Impurities to drain (RO Reject)

13. > 98.5% GdCl3 or Gd2(SO4)3 (NF Reject) 100% of GdCl3 or Gd2(SO4)3 plus smaller impurities (UF Product) Pure water plus GdCl3 or Gd2(SO4)3 from SK Ultrafilter Nanofilter (1) Impurities larger than GdCl3 or Gd2(SO4)3 (UF Reject) Nanofilter (2) Impurities smaller than GdCl3 or Gd2(SO4)3 (NF Product) (NF Reject) DI/RO Pure water (RO/DI product) plus GdCl3 or Gd2(SO4)3 back to SK Impurities to drain (RO Reject)

14. Sodium Sulfate – analogue compound Spectrophotometer data = 1 meter at 0.2% loading 22% 35% 25% 12% 5% 1% of total Cherenkov light in SK An absorption coefficient of 0.0015 means 99.7% of the light survives This plot corresponds to a sulfate attenuation length of >150 meters @ 0.2% Looks very promising so far, but must be confirmed with IDEAL…

15. Additional Upcoming Work @ UCI 1) Dissolve Gd2(SO4)3 2) Highly Purify Gd2(SO4)3 3) Send Very Pure Gd2(SO4)3 to IDEAL

16. What about the leak in SK? Fixing the leak before introducing gadolinium into Super-K is likely to be required for political and public-relations reasons. University of Tokyo policy requires “avoidance of public concern.”

17. What about the leak in SK? Over the next year or so Mitsui will be asked to evaluate the mechanical strength of different types of epoxy (with Gd) on a variety of holes and cracks. They will also consider polyethylene liner material and MineguardTM. At the same time, we will use IDEAL at UCI to evaluate the effects of epoxies on water transparency. We estimate 5.5 months would be required to: drain Super-K while apply epoxy from boats during drain (2 weeks), epoxy coat tank bottom while restoring outer wall tyvek (2 weeks), restore bottom tyvek (1 week), refill detector (2.3 months), and recirculate (2 months @ 60 tons/hr) for good water. This will have to be coordinated with T2K shutdown periods.

18. Alternative way I [Y. Suzuki – Nov. 2007 SK Collaboration Council] • Make <1kt (?) water tank equipped with sufficient numbers of PMT to test various things with 0.2% Gd concentration. • Almost all the purpose of the 0.0004% run can be achieved. • Can run a few years • Please answer if this approach is acceptable and feasible • Size? • Number of PMT?

19. With the support of ICRR and IPMU, we have decided to build a large, dedicated Gd test tank, complete with its own water filtration system, 50-cm PMT’s, and DAQ electronics. This (few) 100 ton-scale R&D project will be called EGADS – Evaluating Gadolinium’s Action on Detector Systems. It will be located underground at the Kamioka Observatory, in the XMASS hall.

20. What are the goals of EGADS? A test tank will allow us to conclusively address the following questions: • How fast can a Gd compound be added to the water?We will find out by dissolving the most promising Gd compound(s). • Will the dissolved Gd distribute itself uniformly in a large volume?Resistivity probes mounted throughout the volume will tell us. • How quickly/economically/completely can the Gd be removed?We will remove the compound(s) with different methods and assess the effectiveness via the in situ resistivity probes and water samples. • Are there any materials effects to worry about?Examination of the tank components and water system over time will augment sample soaking tests performed at Okayama University (by Ishino-san/Sakuda-san). Also, any variations in water transparency will be closely monitored. • Does selective filtering work, i.e., can we keep the water clear over extended periods of time?Water quality will be continuously checked. These are issues which must be conclusively studied before introducing Gd into Super-K.

21. At the IPMU 1st Anniversary Celebration (Oct. 3, 2008): Beer Jan Schuemann (New IPMU Postdoc) Formal Clothing Who’s this happy guy? Jan’s Wife (Not a random IPMU staff member)

22. IDEAL: Irvine Device Evaluating Attenuation Length Laser Pointers/ N2 Dye Laser IS/PD 6.5 m Normalized Light Intensity Water with Gd2(SO4)3 Depth This is an upgrade of a 1-meter long device successfully used for IMB IS/PD [UCI High Bay Building]

23. IDEAL works very well, but we would like to create an updated version in Japan for EGADS It would be nice to able to use all new equipment, too!

24. Water Attenuation Length at Kamioka Jan’s project for use with EGADS, WALK is to be an enlarged, even more accurate version of IDEAL. He will build it (with guidance from Michael Smy) in the XMASS room. Data taken with IDEAL at different wavelengths

25. New experimental halls at Kamioka [M. Nakahata] XMASS KamLAND 15m 15m 21m SK 170m EGADS WALK New Halls

26. Optimization studies are now underway for EGADS(see previous talk by A. Kibayashi) 6m x 6m 10m x 10m [A. Kibayashi] Smaller  faster and less expensive to build but only useful for R&D Larger  might go beyond simple R&D but more expensive and uses up more XMASS space

27. What’s the schedule for EGADS? The very rough schedule is as follows, contingent, of course, on funding availability: 2009: Construction of stainless steel test tank and PMT-supporting structure, WALK construction begins 2010: Assembly of main water filtration system, tube prep, fill of tank (without PMTs but with Gd) and test selective filtration, Gd removal, mounting of PMT’s begins, WALK main construction finished (refinements continue, but system is functional) 2011: PMT mounting and DAQ completed, refill tank with Gd, tests done in 2010 are repeated with phototubes in place At the same time, leak repair studies will be carried out in Japan by Mitsui and transparency and corrosion tests will be ongoing in Okayama.

28. A Gadolinium Timeline: 2008 2009 2010 2011 Filtration and Transparency Tests @ UCI WALK Construction @ Kamioka EGADS Test Tank Bids EGADS Test Tank Construction @ Kamioka EGADS Water System Construction Add Gadolinium Selective Filtration Tests w/o PMT’s/PMT prep Main EGADS Results Gd Removal Trials & Draining of EGADS Tank PMT Mounting in EGADS Tank/DAQ Assembly Add Gadolinium Data Taking and Selective Filtration Tests with PMT’s Mitsui Epoxy Evaluation Corrosion Tests @ Okayama

29. Our near-term goal is to conclusively settle all remaining issues regarding adding Gd to Super-K. Then we will be ready to act as soon as schedule and budget allows. So that’s the gadolinium roadmap… Let’s follow it to see new sights!