Yasuhiro Kishimoto for KamLAND collaboration RCNS, Tohoku Univ. September 12, 2007 TAUP 2007 in Sendai

KamLAND 1.36g/l

Physics target of KamLAND Next target

Prediction of solar flux Heavy elements abundance Strong disagreement with helioseismological measurement Nuclear reaction cross sections (LUNA) 3 He( ,  ) 7 Be, 14 N(p,  ) 15 O

Solar neutrino status Borexino succeeded 7 Be observation. KamLAND plans to measure 7 Be and CNO to test the solar model (AGS05). arXiv: lv2 [astro-ph]

KamLAND spectrum (Before purification) 7 Be  Main BG: 85 Kr 210 Bi, 210 Po, 40 K CNO Main BG: 40 K, 11 C Fiducial R<4m

2002~ 2006 Small and middle size test bench Summer in 2006 ~ Construction Autumn and winter in 2006 Shake down History of Purification studies

Reduction efficiency (test bench results) Reduction Goal 40 K3.8 x ~ Kr<1.3 x ( Nat. Kr) ~ Pb<7.6 x ( 212 Pb ) ~ Rn 6.0 x ~10 -3

Purification System Distillation against metals and ions N 2 purge against Kr, Ar, and Rn.

ParameterPressure [kPa]Temperature [C] PC tower2.00 (Max-min: 0.08%) 62.4 (Max-min: 3.1%) NP tower2.00 (Max-min: 0.17%) 96.9 (Max-min: 0.85%) PPO tower0.60 (Max-min: 0.48%) (Max-min: 0.69%) Purge tower 40.0 (Max-min: 0.00%) (F=30Nm 3 /h) (Tower A) (Tower B) Status during 1 st Purification LS purification rate: F=0.9t/h Parameters were well controlled.

Status during 1 st Purification 222 Rn measurement → OK (<10mBq/m 3 ) miniLAND Electro static collection method See posters. Nat. Kr measurement Cold trap + RGA Light yield and attenuation length of LS 222 Rn and 85 Kr are counted with KamLAND

1 st Purification Total 1699m 3 of LS was purified through Aug. 1 st, Purified Volume / KamLAND volume = 1.4 Reactor and geo neutrino observation ware continuing.

Status during the 1 st purification Vertex distribution (0.45 MeV <E<0.70 MeV) Preliminary

Status during the 1 st purification Lighter LS was installed.  ~0.03% Last 173m % of KamLAND (Z>3.4m) Succeeded to keep LS boundary. Preliminary Vertex distribution (Aug. 1-17) (0.45 MeV <E<0.70 MeV)

Status after purification Lower part Preliminary x 2 +y 2 [m 2 ] z [m]

Status after purification Upper part Preliminary x 2 +y 2 [m 2 ] z [m]

Status after the 1 st purification (cont.) 210 Bi 210 Po 85 Kr 39 Ar 40 K 232 Th Before mBq/m (0.5) 39.5 (0.7) (2.2) (2.9) 18.4 (0.5)    Bq/m 3 After mBq/m (0.1) 7.1 (0.1) 8.8(0.1) 15.1 (1.9) 4.5 (0.3) (0.2) 6.4 (0.3) (0.3) < %CL 1.2 (2.3)  Bq/m 3 Ratio [%] After/Before 7.2 (0.3) 20.3 (0.4) 20.3 (0.5) 38.2 (4.9) 1.07 (0.08) 26.4 (0.2) 5.9 (0.4) 93.2 (2.5) <20% Need more statistics. Red figure: Upper region (Z>4m) Blue figure: Lower region (Z<3m) The activity are still high for 7 Be and CNO, but 210 Po reduction helps reactor and geo measurement a lot because of lower ( , n) background.

Toward 2 nd purification Prevent mixing T,  F, …

NP+PPO is installed. Toward 2 nd purification (cont.) Much more careful distillation Small  T,  P, … Real-time BG monitor for quick feedback Energy estimation PPO is distilled. PPO was extracted. Temperature [C] Time [h] Pressure [kPa]

2 nd purification campaign We stopped our purification activities. Blasting in Kamioka mine by next spring We are going to upgrade our apparatus. And we start 2 nd purification campaign after blasting.

For CNO neutrino measurement

11 C rejection by neutron events Triple coincidence events Cosmic  Neutron (Capture time ~210  sec) 11 C (Lifetime=29.4min.) Neutron tagging is important. Point like (NO track. → Smaller dead time) 12 C + X → 11 C + n + Y (Br~95%) X= , n, p, , e, , … Requirement for dead time free electronics

Energy spectra after 11 C rejection Expected CNO + pep flux error ~ 6% (Stat. error) Prototype was tested. Go poster session to see results.

Summary 1 st purification of KamLAND liquid scintillator has been accomplished. Reduction in KamLAND activities are still being determined. 2 nd purification will start in Spring of next year. New electronics is being developed for CNO.

Backup 40 K

Status during 1 st Purification Light yield measurement Measure Compton edge of 60 Co (1.1, 1.3keV) No significant change was observed.

Status during 1 st Purification Attenuation length measurement L~4.9m

LS density