Solar Neutrino at KamLAND

1. Solar Neutrino at KamLAND Sei Yoshida Reserch Center for Neutrino Science, Tohoku Univ. for the KamLAND Collaboration LAUNCH Workshop @ MPI, Heiderberg

2. Reactor Neutrino Solar Neutrino KamLAND Geo-neutrino KamLAND Experiment • Confirmed oscillation of reactor anti-neutrino, firstly detected anti-neutrino from the earth. • Next step,  7Be solar neutrino detection LAUNCH Workshop @ MPI, Heiderberg

3. 1 kt Liquid Scintillator PMTs KamLAND Detector KamLAND Detector • Kamiokamine overburden : 2700m.w.e. Muon rate : 0.34Hz • 1000 tons of Liquid Scintillator • Mineral Oil : Buffer against external BG • 1979 PMTs(17” 1325 + 20” 554) • Photocathod caverage : 34% • Outer water Cherenkov detector for muon veto LAUNCH Workshop @ MPI, Heiderberg

4. Solar Neutrino Detection • Anti-neutrino detection Neutrino detection Delayed coincidence signature Single unspecific signature Small Background High level of Background LAUNCH Workshop @ MPI, Heiderberg

5. Internal Background of KamLAND At present • Single energy spectrum observed in KamLAND • 4 m fiducial volume cut to suppress 40K and 208Tl external BG • What is remeined background in single energy spectrum? LAUNCH Workshop @ MPI, Heiderberg

6. Internal Background of KamLAND • Main sources of background in the range of 7Be neutrino • 210Pb( 210Bi  210Po )  by distillation • 85Kr  by N2 purging LAUNCH Workshop @ MPI, Heiderberg

7. Required Reduction by Purification 222Rn 3.8 d < 1mBq/m3 LAUNCH Workshop @ MPI, Heiderberg

8. R&D Study for Distillation • Achievement Impurity Reduction • 210Pb ~7×10-5 • 40K > 4×10-2 • 85Kr ~1×10-6 • 39Ar ~1×10-6 Almost acheived required level Test Apparatus @ Tohoku Univ. LAUNCH Workshop @ MPI, Heiderberg

9. Expected Spectrum after Purification 210Pb :7.7×10-5 40K :3.8×10-285Kr :1.0×10-6 39Ar :1.0×10-6 11C LAUNCH Workshop @ MPI, Heiderberg

10. New Purification System • Construction finished • Test operation to tune up parameters LAUNCH Workshop @ MPI, Heiderberg

11. Concept of New Purification System Distillation System N2 Purge Towers N2 Generator LAUNCH Workshop @ MPI, Heiderberg

12. Distillation System • Liquid scintillator(LS) is fed into small buffer tank (2m3)from KamLAND. • Different boiling point LAUNCH Workshop @ MPI, Heiderberg

13. Distillation System (PC tower) • Pseudocumene(PC) is distilled firstly • Operating pressure 2kPa. • Boiling point ~ 60℃ • Rest at the bottom of PC tower  Dodecane + PPO •  send to next tower LAUNCH Workshop @ MPI, Heiderberg

14. Distillation System (NP tower) • Dodecane(NP) is distilled secondly. • Operating pressure ~2kPa. • Boiling point ~ 100℃ • Rest at the bottom of NP tower  Dodecane + PPO(little concentrated) •  send to PPO concentrator (~140℃ under 2kPa), NP is evaporated back to NP tower. LAUNCH Workshop @ MPI, Heiderberg

15. Distillation System (PPO tower) • PPO is distilled finally. • Operating pressure ~0.6 kPa. • Boiling point ~ 190℃ • Rest at the bottom of PPO tower  Exhaust LAUNCH Workshop @ MPI, Heiderberg

16. Distillation System (Mixture tank) • LS is mixed(blended) withdistilled PC,NP, and PPO. • Temperature senser and Density meter • PC and NP mixture is adjusted by pre-small tank. • PPO is mixed with PC ~ 10 wt%, then fed into mixture tank. LAUNCH Workshop @ MPI, Heiderberg

17. Distillation System (Purge towers) • Purging by pure N2 gas • Operating pressure ~ 40 kPa • N2 flow rate 30 ~ 35 Nm3/h • Series of “Gas – Liq. Mixer”, and “Gas-Liq. Separator” LAUNCH Workshop @ MPI, Heiderberg

18. N2 Generator • Newly developed/constructed N2 generator • Supply air : Rn less air from outside of mine • N2 supply capacity : 40 Nm3/h Emergency 5 Nm3/h • Purity • Ar 0.02 ~ 0.03ppm (measured) • Kr ~10-15 (not measured yet) • 222Rn ~ 5mBq/m3 (measured at purif. Area) LAUNCH Workshop @ MPI, Heiderberg

19. Monitoring Quality Background Reduction • Reduction factors for 210Pb and 40K will be monitored by KamLAND • The data will be continuously taken during purification. • Rn concentration in purified LS • Delayed coincidence of Bi-Po  miniLAND • Electrostatic collection method after trapping • Reduction factor of 85Kr • The system is now tuning. Optical property • Attenuation length after distillation • Light output LAUNCH Workshop @ MPI, Heiderberg

20. Monitoring Rn Concentration –miniLAND-- • miniLAND ; miniture version of KamLAND • 0.4m3 of acrylic container ( 4×4 cells) • NaI solution as light guide to shield radiation from PMTs • Pb shield of 15 cm in thickness • Borated PE of 5 cm in thickness • Measuring Rn concentration by Bi-Po delayed coincidence • Sensitivity < 1 mBq/m3 • It can also monitor, • Light output • Attenuation length • System is now ready LAUNCH Workshop @ MPI, Heiderberg

21. Rn Measurement System LAUNCH Workshop @ MPI, Heiderberg

22. KamLAND Purification Area Rn Concentration in N2 Gas • Piping line between purification area and N2 generator, ~100m • Rn emanation  consistent with designed value ~ 5mBq/m3 LAUNCH Workshop @ MPI, Heiderberg

23. Monitoring Attenuation Length • Light beam is collimated onto different wavelength filters. • For each of 21 different liquid heights along the 1 m long Stainless Steel tube (which is coated to minimize scattering) we take the following measurements: • PMT Dark current, measured by using a plug in the filter wheel • Beam intensity using photo-diode • PMT current for each wavelength filter (10 filters from 313 -550 nm) • Height is measured by differential pressure gauge and is calibrated for different liquid densities. LAUNCH Workshop @ MPI, Heiderberg

24. Results for Purified LS (MO/PC/PPO) • We can already make LS by distilled PC/NP/PPO. • No significant deterioration for attenuation length • Compareing att. length before and after distillation LAUNCH Workshop @ MPI, Heiderberg

25. Present Status of Purification • Pseudocumene and Dodecane are successfully and stably distillated for a period longer than a month. • PPO tower operates as expected, however, stable/continuous operation has not been achieved yet. • Complete operation of full system will be tested soon, probably within a month. • Quality of purified(distilled and purged) scintillator were measured, no detectable impurities/deterioration has been measured/observed. LAUNCH Workshop @ MPI, Heiderberg

26. Purification Schedule • Recirculation test (soon, within a month) • Recirculate small amount of LS into KamLAND to test this process without any purification process. • After stable PPO tower operation ( probably within one or two months), recirculation distillated LS into KamLAND using the online distillation system • To test recirculation process comletely • To check the quality of distilled LS further, recirculate ~50m3 of distilled LS into KamLAND • Regular distillation process, but ….. • Full volume replacement will require ~ two months. • Unfortunately, there is a time constraint because of scheduled blaster in the mine to install new XMASS facility.(very clese to new purification site). • Previously, we requested a delay to the end of March 2007. • We are now negotiating further delay in blasting activity. LAUNCH Workshop @ MPI, Heiderberg

27. Summary • LS purification system was constructed. • Part of operation is successfully running. • Monitoring system of LS Quality after purification is almost ready. • There is a time constraint. LAUNCH Workshop @ MPI, Heiderberg