Yasuhiro Kishimoto for KamLAND collaboration

RCNS, Tohoku Univ.

September 12, 2007TAUP 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)3He(, )7Be, 14N(p, )15O

Solar neutrino statusBorexino succeeded 7Be observation.KamLAND plans to measure 7Be and CNO to test the solar model (AGS05).

arXiv:0708.225lv2 [astro-ph]

KamLAND spectrum (Before purification)

7Be Main BG: 85Kr 210Bi, 210Po, 40K CNO

Main BG: 40K, 11C

Fiducial R<4m

2002~ 2006 Small and middle size test

benchSummer in 2006 ~

ConstructionAutumn and winter in 2006

Shake down

History of Purification studies

Reduction

Goal

40K 3.8 x 10-2 10-2~10-1

85Kr <1.3 x 10-5

(Nat. Kr)10-6~10-5

210Pb <7.6 x 10-5

(212Pb )10-5~10-4

222Rn 6.0 x 10-4 ~10-3

Purification SystemDistillation against metals and ionsN2 purge against Kr, Ar, and Rn.

Parameter

Pressure [kPa] Temperature [C]

PC tower 2.00 (Max-min: 0.08%)

62.4 (Max-min: 3.1%)

NP tower 2.00(Max-min: 0.17%)

96.9(Max-min: 0.85%)

PPO tower

0.60(Max-min: 0.48%)

174.8(Max-min: 0.69%)

Purge tower

40.0(Max-min: 0.00%)(F=30Nm3/h)

29.0+3.2-2.8 (Tower

A)29.5+2.9

-2.5 (Tower B)

Status during 1st PurificationLS purification rate: F=0.9t/hParameters were well controlled .

Status during 1st Purification222Rn measurement → OK (<10mBq/m3)

miniLANDElectro static collection method

See posters.

Nat.Kr measurement Cold trap + RGA

Light yield and attenuation length of LS 222Rn and 85Kr are counted with

KamLAND

1st Purification

Total 1699m3 of LS was purified through Aug. 1st, 2007.Purified Volume / KamLAND volume = 1.4Reactor and geo neutrino observation ware continuing .

Status during the 1st purification

Vertex distribution(0.45 MeV <E<0.70 MeV)

Preliminary

Status during the 1st purificationLighter LS was installed.

~0.03%Last 173m3

14.4% 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 purificationLower part

Preliminary

x2+y2 [m2]

z [m

]

Status after purificationUpper part

Preliminary

x2+y2 [m2]

z [m

]

Status after the 1st purification (cont.)

210Bi 210Po 85Kr 39Ar 40K 232Th

BeforemBq/m3

34.9(0.5)

39.5 (0.7)

421.3(2.2)

108.0(2.9)

18.4(0.5)

Bq/m3

AftermBq/m3

2.5 (0.1)7.1(0.1)

8.8(0.1)15.1(1.9)

4.5(0.3)111.3(0.2)

6.4(0.3)100.7(0.3)

< 3.7 90%CL

1.2(2.3)Bq/m3

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 7Be and CNO , but 210Po reduction helps reactor and geo measurement a lot because of lower (, n) background.

Toward 2nd purification

Prevent mixingT, F, …

NP+PPO is installed.

Toward 2nd purification (cont.)Much more careful

distillationSmall T, P, …

Real-time BG monitor for quick feedbackEnergy estimation

PPO is distilled.

PPO was extracted.

Tem

pera

ture

[C

]

Time [h]

Pre

ssu

re [

kP

a]

2nd purification campaignWe stopped our

purification activities .Blasting in Kamioka

mine by next springWe are going to

upgrade our apparatus .

And we start 2nd purification campaign after blasting.

For CNO neutrino measurement

11C rejection by neutron events

Triple coincidence eventsCosmic Neutron (Capture time ~210sec) 11C (Lifetime=29.4min.)

Neutron tagging is important.

Point like(NO track. → Smaller dead time)

12C + X → 11C + n + Y (Br~95%) X=, n, p, , e, , …

Requirement for dead time free electronics

Energy spectra after 11C rejection

Expected CNO + pep flux error ~ 6% (Stat. error)

Prototype was tested.Go poster session to see results.

Summary1st purification of KamLAND liquid scintillator has

been accomplished.Reduction in KamLAND activities are still being

determined. 2nd purification will start in Spring of next year.New electronics is being developed for CNO .

Backup 40K

Status during 1st PurificationLight yield measurement

Measure Compton edge of 60Co (1.1, 1.3keV)

No significant change was observed.

Status during 1st PurificationAttenuation length

measurementL~4.9m

LS density