Current Status of RENO Soo-Bong Kim Seoul National Univ. Feb. 27, 2008 at YongPyong

Neutrino oscillation parameters (A new field of particle physics has begun!) reactor and accelerator 13 = ? ? CP = ? SNO, solar SK, KamLAND 12 ≈sol ≈ 32° 0 atmospheric SK, K2K 23≈atm ≈ 45° Large and maximal mixing! Ue3

13 from Reactor and Accelerator Experiments - Clean measurement of 13 - No matter effects mass hierarchy CP violation accelerator matter - sin2213 is missing key parameter for any measurement of CP

Reduction of reactor neutrinos due to oscillations Disappearance Reactor neutrino disappearance Prob. due to 13 with the allowed 2 range in m232 sin22q13 > 0.01 with 10 t •14GW •3yr ~ 400 t•GW•yr (400 t•GW•yr: a 10(40) ton far detector and a 14(3.5) GW reactor in 3 years)

Reactor neutrino q13 experiment Search for energy dependent ne disappearance using two (or more) detectors Need to be located underground in order to reduce backgrounds from cosmic rays and cosmic ray induced spallation The detectors need to be designed identically in order to reduce systematic errors to 1% or less

Detection of Reactor Neutrinos data from CHOOZ hep-ex/0301017v1 (1) 0.7<Eprompot <9MeV (2) 5<Edelayed <11MeV (3) 1μs<ΔT <200μs e+ energy n capture energy

RENO Collaboration Chonnam National University Dongshin University Gyeongsang National University Kyungpook National University Pusan National University Sejong University Seoul National University Sungkyunkwan University Institute of Nuclear Research RAS (Russia) Institute of Physical Chemistry and Electrochemistry RAS (Russia) +++ http://neutrino.snu.ac.kr/RENO

Schematic Setup of RENO at YongGwang

Google Satellite View of YeongGwang Site

Schematic View of Underground Facility

Schedule 사업내용 검출장비 설계 및 사양 결정 암반 지질조사 및 터널 설계 검출장비 제작 터널굴착 및 지하시설 구축 검출장비 시험가동 2006 2007 2008 2009 3 6 9 12

Comparison of Reactor Neutrino Experiments Location Thermal Power (GW) Distances Near/Far (m) Depth (mwe) Target Mass (tons) Double-CHOOZ France 8.7 280/1050 60/300 10/10 RENO Korea 17.3 290/1380 120/450 15/15 Daya Bay China 11.6 360(500)/1985(1613) 260/910 402/80

Efforts for Underground Facility 03~08, 2006 : Project description to local government, residents, and NGO’s (endorsed by local government) 03, 2007 : Agreement between KHNP and SNU 03~10, 2007 : Geological survey and tunnel design are completed. 12, 2007 : Public hearing for YG residents 01, 2008 : Safety regulation established and accepted by the atomic energy department of MOST 04~11, 2008 : Tunnel construction

Rock sampling (DaeWoo Engineering Co.) Rock samples from boring

Rock quality map Near detector site: tunnel length : 110m overburden height : 46.1m Far detector site: tunnel length : 272m overburden height : 168.1m

Stress analysis for tunnel design

Tunnel Excavation Schedule

Components of RENO Detector Gamma catcher : - LS Target : - Gd + LS RENO실험은 원자력 발전소에서 발생하는 중성미자를 액체섬광 검출기를 사용하여 Inverse beta decay를 통해서 neutrino disappearance를 관측하는 실험이다. RENO detector는 크게 inverse beta decay를 생성하는 target부분과 광생성이 일어나는 gamma catcher부분이 핵심적이고 Accidental Background 영향을 줄이는 Buffer부분과 muon과 같은 correlated background를 줄이는 veto부분이 있다. Target 부분에는 neutron x-section이 큰 Gd을 첨가하여 검출효율을 높이는 동시에 background를 줄일 수 있다. Liquid scintillator는 높은 광생성과 투명도, 그리고 장기적으로 안정해야 되고 radiopurity가 좋아야 한다. Buffer : - Non scintillating oil Veto : - Water

Detector Design with MC Simulation RENO-specific MC simulation based on GLG4sim/Geant4 Detailed detector design and drawings are completed Detector performance study & Detector optimization with MC: - Gamma catcher size - Buffer size - photo-sensor coverage (no. of PMTs) - neutron tagging efficiency as a function of Gd concentration Reconstruction(vertex position & energy) program written Systematic uncertainty & sensitivity study Background estimation

RENO Detector Veto Buffer Target g-catcher total ~450 tons Inner Diameter (cm) Inner Height (cm) Filled with Mass (tons) Target Vessel 280 320 Gd(0.1%) + LS 15.4 Gamma catcher 400 440 LS 27.5 Buffer tank 540 580 Mineral oil 59.2 Veto tank 840 880 water 354.7 total ~450 tons

RENO Detector

RENO Detector

Electronics

Detector Calibration & Monitoring

Reconstruction of Cosmic Muons A B C D Veto (OD) Buffer (ID) pulse height time OD PMTs ID PMTs target buffer g-catcher

Prototype Detector

Prototype Detector Assembly Filling with liquid scintillator Acrylic vessels Inner acrylic vessel Mounting PMTs Nitrogen flushing of LS assembled prototype Filling with liquid scintillator

Energy Calibration Using 60Co and 137Cs DAQ & Trigger Logic Radioactive sources 0.1

Mockup Detector

Mockup Detector

MC of Mockup Detector 60Co 137Cs

Gd+Liquid Scintillator R&D General Elements of Liquid Scintillator : Aromatic Oil Flour WLS Gd-compound PC(Pseudocumene), PXE, LAB Mineral oil, Dodecane, Tetrdecane, LAB PPO, BPO Bis-MSB, POPOP 0.1% Gd compounds with CBX or BDK PC(20%) + Dodecane(80%) + PPO with bis-MSB or BPO 0.1% Gd compounds with CBX or BDK R&D with the Russian INR/IPCE group (Gd powder supply) Recipe with various mixture: performance (light yield, transmission & attenuation lengths), availability, cost, etc. Design of purification system & flow meter Long-term stability test Reaction with acrylic? R&D on LAB

R&D with LAB instead of PC/PXE + Dodecane CnH2n+1-C6H5 (n=10~14) Light yield measurement High Light Yield : not likely Mineral oil(MO) replace MO and even Pseudocume(PC) probably Good transparency (better than PC) High Flash point : 147oC (PC : 48oC) Environmentally friendly (PC : toxic) Components well known (MO : not well known) Domestically available: Isu Chemical Ltd. (이수화학) PC100% LAB100% PC40% PC20% LAB100% PC20% N2 LAB60% LAB80% MO80%

Measurement of LAB Components with GC-MS C16H26 C17H28 C18H30 C19H32 7.17% 27.63% 34.97% 30.23% LAB : (C6H5)CNH2N+1 # of H [m-3] = 0.631 x 1029 H/C = 1.66

Systematic Errors Systematic Source CHOOZ (%) RENO (%) Reactor related absolute normalization Reactor antineutrino flux and cross section 1.9 < 0.1 Reactor power 0.7 Energy released per fission 0.6 Number of protons in target H/C ratio 0.8 0.2 Target mass 0.3 Detector Efficiency Positron energy Positron geode distance 0.1 0.0 Neutron capture (H/Gd ratio) 1.0 Capture energy containment 0.4 Neutron geode distance Neutron delay Positron-neutron distance Neutron multiplicity 0.5 0.05 combined 2.7 < 0.6

RENO Expected Sensitivity New!! (full analysis) 10x better sensitivity than current limit

GLoBES group workshop@Heidelberg – Mention’s talk SK Dm2

Status Report of RENO RENO is suitable for measuring q13 (sin2(2q13) > 0.02) Geological survey and design of access tunnels & detector cavities are completed → Excavation will start in April 2008. RENO is under construction phase. Data –taking is expected to start in early 2010. TDR will be ready in April of 2008. International collaborators are being invited.

Back-up slides

Study on -catcher size Gamma catcher thickness = 20cm Gamma catcher thickness = 90cm MeV Gd capture H capture RENO 70cm: (94.28+/-0.54)% 60cm: (92.98+/-0.56)% Daya Bay 45cm: 92% Chooz 70cm: (94.6+/-0.4)%

Reconstruction : vertex & energy Reconstructed vertex:  ~8cm at the center of the detector y 4 MeV (KE) e+ |y| sy (mm) Evis (MeV) Energy response and resolution: visible energy PMT coverage, resolution ~210 photoelectrons per MeV 1 MeV (KE) e+

Study on buffer thickness Generate almost all energy lines from 232Th and 238U decay chains Using activities of three nuclides (238U = 0.70, 232Th = 0.41, 40K = 1.63 [Bq/PMT] (Hamamastu)) Sources of gamma are extended to be Target, Gamma Catcher and PMT (PMT) Single Rates with 1 MeV Cut Rsingle = Npmt×Ract×Navg×ε [Hz] Gap [mm] 40K 232Th 238U Total 500 3.4 8.0 11.2 22.6 600 2.0 5.3 7.1 14.4 700 1.4 3.9 5.1 10.4 800 0.8 2.7 3.6 900 0.5 1.6 1.9 4.0 1000 0.3 1.1 2.8

Calculation of Muon Rate at the RENO Underground Jμ [cm-2s-1] <Eμ> [GeV] Far 250 m 2.9×10-5 91.7 200 m 8.5×10-5 65.2 Near 70 m 5.5×10-4 34.3 Muon intensity at the sea level using modified Gaisser parametrization + MUSIC or Geant4 (the code for propagating muon through rock)

Calculation of g Background at the RENO Underground g rate from rock [Hz] Double CHOOZ Daya Bay RENO Rock composition (K) 1.6 ppm (U) 2.00 ppm (Th) 5.0 ppm (K) 5 ppm (U) 10 ppm (Th) 30 ppm (K) 4.0 ppm (U) 4.8+/-1.8 ppm (Th) 6.0+/-2.2 ppm * Sample from Chongpyung. Detector DxH Size [cm] 230x246 (10.3 m3) 320x320 280x320 Shelding 17 cm Steel 2.5 m Water + 0.45 m Oil Rates (K) [Hz] (U) (Th) 0.86 ~0.89 0.98 0.26 0.65 2.6 (E>1 MeV) 0.21 0.53 1.74 (E>0.5 MeV) Total rate ~2.73 Hz 3.5 Hz 2.5 Hz

PMT Test

Comparison of PMT performance