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Reactor Neutrino Physics at the Kuo-Sheng Power Plant in Taiwan

This article provides an overview of the TEXONO Collaboration's research at the Kuo-Sheng Power Plant, exploring reactor neutrino physics. It discusses the goals, R&D projects, and future possibilities of studying neutrinos and astroparticles.

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Reactor Neutrino Physics at the Kuo-Sheng Power Plant in Taiwan

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  1. Reactor Neutrino Physics at the Kuo-Sheng Power Plant in Taiwan • TEXONO Collaboration : Overview • Kuo-Sheng(國聖) Reactor Neutrino Lab. ※Physics with Reactor Neutrinos ※First Results with ULB-HPGe ※Future Possibilities • R&D Projects • Status and Plans Henry T. Wong Academia Sinica @ UniversitätDortmund, Germany May, 2002

  2. Experimental High Energy Physics in Taiwan • Start : 1990’s • Three main groups: ※Academia Sinica (AS) ※Nat. Taiwan U.(NTU) ※Nat. Central U. (NCU) • AS:※CDF @ Fermilab ※AMS on Space Shuttle & ISS ※ATLAS @ LHC ※TEXONO program [this talk] • NTU:※Bella @ KEK ※ CMS @ LHC • NCU:※L3 @ LEP ※ AMS on Space Shuttle & ISS ※ PHOBOS @ RHIC ※ CMS • small but dynamic/resourceful community

  3. TEXONO* Collaboration • W.C. Chang¶, C.P. Chen, K.C. Cheng, H.C. Hsu, F.S. Lee, S.C. Lee, S.T. Lin, • D.S. Su, P.K. Teng, W.S. Tse¶, H.T.K. Wong†, C.S. Wu, S.C. Wu • Academia Sinica, Taipei, Taiwan • W.P. Lai • Chung Kuo Institute of Technology, Taipei, Taiwan • C.H. Hu, J.M. Huang, W.S. Kuo, T.R. Yeh • Institute of Nuclear Energy Research, Lungtan, Taiwan • H.B. Li, C.H. Tang, M.Z. Wang¶ • National Taiwan University, Taipei, Taiwan • J.H. Chao, J.H. Liang • National Tsing Hua University, Hsinchu, Taiwan • Z.M. Fang, R.F. Su • Nuclear Power Station II, Kuosheng, Taiwan • M. He, S. Jiang, L. Hou, H.Q. Tang, B. Xin, Z.Y. Zhou¶ • Institute of Atomic Energy, Beijing, China • J. Li†, Y. Liu, Z.P. Mao, J. Nie, J.F. Qiu, H.Y. Sheng, P.L. Wang, X.W. Wang, • Q. Yue, D.X. Zhao, J.W. Zhao, P.P. Zhao, S.Q. Zhao, B.A. Zhuang • Institute of High Energy Physics, Beijing, China • Z.S. Liu, Z.Y. Zhang • Institute of Radiation Protection, Taiyuan, China • T.Y. Chen • Nanjing University, Nanjing, China • J.P. Cheng, D.Z. Liu • Tsing Hua University, Beijing, China • C.Y. Chang, G.C.C. Chang† • University of Maryland, Maryland, U.S.A. • † Co-Prinicipal Investigators • ¶ Project Leaders • Ph.D. Students • HISTORY • Initiate : Chang Chung-Yung 1996 • First ICollaboration Meeting/Official Start : October 1997 • First Paper : October 1998 • KS Reactor Experiment Installation : June 2000 • First Ph.D. : Liu Yan , July 2000 • First Physics Data Taking : June 2001. • *Taiwan EXperiement On NeutrinO • Home Page @http://hepmail.phys.sinica.edu.tw/~texono/

  4. TEXONO Overview • Goals : • Neutrino and Astroparticle Physics •  Starting phase: 1st particle physics expt in Taiwan • Build up a Qualified Group •  1st big research Coll. % Taiwan & China • Program : • Kuo-Sheng Reactor Neutrino Lab. • ※mn0  anomalous n properties & interactions • ※ n’s strange & full of surprises • study new regime wherever possible experimentally • R&D Projects •  diversified program • ※reactor program as base • ※ explore various future scenarios0

  5. Physics with Reactor Neutrino [Location close to Cores] • mn0  anomalous n properties & interactions [be prepared for surprises…] • n oscillations source-detector distance other n studies flux & its control • Reactor an intense & free source of n’s typical ~1013 cm-2 s-1[c/f n1010 cm-2 s-1 ] • 1st family : probe anomalous matter effect • Reactor ON/OFF background subtraction • Both ne& ne with distinct spectra+timing • Other Exotica ……. e.g. axions ?? • Typical experiment:  sensitive to few events/day  probe anomalies < 10-18 • Experimental Challenges:  surface location, harsh ambient radiation

  6. Kuo-Sheng Nuclear Power Plant KS NPS-II : 2 cores X 2.9 GW KS nLab: 28 m from core#1

  7. Kuo-Sheng Neutrino Laboratory • High flux of ne(also ….. ne) • Modular Design  independentdetector, electronics, shielding • high-Z target, large re • Improved detector performance:  good energy & spatial resolution, low threshold, a/g separation • Elaborate electronics+DAQ+control sys.  complete record of pulse shape + timing info. • Elaborate Shieldings  radon purge & 4p cosmic veto Configuration: Modest yet Unique Flexible Design: Allows different detectors conf. for different physics

  8. Kuo Sheng Reactor Neutrino Laboratory Front Gate Front View (cosmic vetos, shieldings, control room …..) Inner Target Volume

  9. KS Expt. : Period I Configuration Period I : June 01 – April 02 (60 days OFF) Shielding & Veto [one side] ULB-HPGe + Anti-Comptons CsI(Tl) Array

  10. KS Expt: Period I Detectors ULB-HPGe [1 kg] CsI(Tl) [46 kg] FADC Readout [16 ch., 20 MHz, 8 bit] Multi-Disks Array [600 Gb]

  11. mn with Reactor ne • mn:  parametrize possible niLnjR + g vertices   both i = j “diagonal” & i  j “transition” moments • Experimental Probe:  Study ne + e- nX + e-  Focus on low recoil energy ※ sm  T–1 ※ decouples SM “background” [ ……… LE reactor f(ne) not accurately known]  Look for Excess in Reactor ON/OFF • Neutrino Radiative Decay (Gn):  sm & Gn related:  same vertices – real g for Gn Electron Recoil Spectra

  12. Low Energy Reactor Neutrino Spectrum • Existing models checked with expt. only for En>3 MeV • Known unaccounted effects in En<3 MeV P(ne) fission modelling e.g. long t non-equil. effects • Known unaccounted production channels of ne for En < 3 MeV besides fission e.g. b(ne) from 239U [n+238U]  fission(ne) • Limit sensitivities in some measurements e.g mn , s(ne-e) • mn & s Vs LE uncertainties @ diff. E range R15-100 keV R20.5-2 MeV  Optimal Energy Range : ※mn : low energy window ※ s(ne-e) : E>2 MeV

  13. KS/P1/Ge/mn Data • Data Volume:  Expected total 200/60 days ON/OFF [ reported here : 62/46 ON/OFF ] • HPGe Performance:  1.06 kg mass  0.4 keV RMS @ 10 keV  5 keV threshold [Unique Data]  Range of O(1 cpd) [counts kg-1 day-1 keV-1] background c/f Dark Matter expt. • Analysis:  Cosmic Veto (5 ms gate)  Anti-Compton (Well+Base detectors)  Pulse Shape Disc. (veto elect. noise)  Timing Analysis (veto clusters) [not yet implemented here] • Efficiencies Normalization:  DAQ book-keeping  Monitor random triggers  Monitor residual 40K peaks  Monitor 10 keV Ga X-rays peak

  14. Cosmic Veto : Timing Plot • evidence of delayed induced neutron activities • choose Dt=5 ms HPGe Vs NaI(Tl) : 2D Plot Necessary Cross Checks observed : ※ full capture peaks, Compton edges, coincidences …. etc

  15. KS/P1/Ge : Spectra & Residual Based on 62/46 days of Reactor ON/OFF data

  16. KS/P1/Ge : First Results • Fit OFF spectra to fOFF E/keV fOFFc2/dof 12-61 a1e-a2E+a3+a4E 39/46 • Fit ON spectra to fOFF +fSM + mn2fMM [10-10mB] Best Fit : mn2= -1.7  2.5 @c2/dof =55/49 [Comparable sensitivities to direct-search world limits] • Improvements Expected :  more data [ 3+ ON]  complete & improved analysis  treatment ofthreshold region [e.g. timing] [Aim : ~ 5 keV] Residual Plot

  17. Reactor mn(ne) Sensitivities Gn Sensitivities

  18. KS/P1 Analysis HPGe :exploit the low threshold data • Established Problem: mn and Gn for nevia ne + e nx + e • Speculative Analysis: ※study ne flux from reactor  due to neutron excitation producing e.g. 51Cr, 55Fe [distinct energy & timing …..]  studymn & Gn for ne ※anomalous Neutrino Interactions in Matter e.g.anomalous energy deposition X (>eV) ne + N  nx + N + X [similar analysis as accelerator nm] ※study possible nuclear transitions e.g.73Ge* decays by 2g’s separated by t1/2=4.6 ms CsI(Tl) :TechnicalRun • Event Reconstruction • Background Studies • Optimize for P2

  19. Tagging of 73Ge ½- 2g transitions: • Event-by-Event background-free tag with PSD • To do : Reactor ON/OFF analysis on the system ~1 s before the transition

  20. Search for Anomalous dE/dx • Measure “DC” leakage current in HPGe • Energy Quanta: 5 keV > X > 2 eV • Expect sensensitivities: dE/dx[n+matter] ~ 10-15 dE/dx[m.i.p]

  21. CsI(Tl) Array : Highlights • 40 cm length (longest commercial prod.) • Energy+3D info: 10% FWHM at 660 keV s(z) <2 cm @ E>250 keV • Detector Threshold ~ 20 keV • PSD for g/a : > 99% • Intrinsic Purity : 238U/232Th < 10-12 g/g (equil.) 40K < 10-10 g/g cosmic muon events on-site @ 46 kg target • Goals: • Commission 150+ kg target on-site for Period-II • DAQ with large dynamic range

  22. KS Expt.: Future Thoughts • Existing configurations: push mn/Gn sensitivities s(ne–e) scatterings  analysis opened up by low threshold • Push threshold lower ( X 1/10 ) coherent nN scattering [ observe SM + test exotic processes….] • Insert passive targets for s(nucl.) e.g. 6Li, 7Li, 10B, 11B, 2H …..  s(NC) related to axial isoscalar & strange quark structure in nucleon • Possibilities on Axion Physics ??? [ Topical subject, hopefully more brainstorming here ] • As base to launch other projects  explored by R&D program

  23. R&D Projects • Explore New Detectors Scenarios • loaded crystal scintillator • ultra low energy HPGe • CsI(Tl) for Dark Matter Searches • Upgrading FADCs • Trace Radio-purity with AMS ( Accelerator Mass Spectrometry) • Close Contact with : •  CsI(Tl) CDM search @ Korea • JHFBeijing LBL n project @ IHEP •  Ultra HE (1015 eV) n Telescope @ NTU

  24. CsI(Tl) for CDM Searches • Potential Merits: • Better PSD for g/a separation than NaI(Tl) • Minimal passive materials • Large target mass possible (c/f em-calorimeters 40 tons) • Highlights of R&D Program: • Quenching Factor measurements with neutron beam  lowest threshold data • 1st direct measurement of diff. cross section in heavy nuclei • PSD studies with Neural Net.  improve conventional methods NKIMS Expt. (apprd.) :  200 kg CsI(Tl) for CDM in S. Korea

  25. Upgrade FADC • 40 MHz ; 12 bit ; 32 ch/module @ 9 U VME [ c/f KS FADC : 20 MHz ; 8 bit ; 16 ch/module ] • On-board processing with FPGA • 1000 channels to be used in TPC in LEPS Expt. @ SPring8 by Fall 2002. Mixed signal FADC Adapter Board TPC for LEPS @ SPring8 • 40 MHz sampling rate. • 10 bits resolution with 2Vp-p dynamic range. • Clock distribution with Phase Lock Loop circuit. • On Board digital signal delay and • Real-Time ZERO-Suppression. • High capacity First In First Out Memory. • Easy to use with high density connector. Prototype Measurements :

  26. Trace Radio-purity with AMS • Based at AMS facilities @CIAE • with 13 MV Tandem • Potential Merits: •  small samples, quick •  versatile on sample choice •  sensitive to a/b emitters •  sensitive to stable isotope & extrapolate (e.g. 39K) •  >103 improvements over ICP-MS • [ …….. once prescriptions are known. ] • Status :  demonstrate 129I/127I < 10-12 g/g  measure 40K~10-10 g/g in CsI (powder) Sensitivity goal : 10-14 g/g • Future :  different bases e.g. liquid scintillator 87Rb …… [238U / 232Th series after Tandem upgrade]

  27. Summary • TEXONO Collaboration:  Built-Up and Growing • Kuo-Sheng Neutrino Lab.: Established & Operational ※Modular & Flexible Design Physics Data Taking since June 01 ※Unique HPGe Low Energy Data ※ Bkg Level ~ Udrgd. CDM Expt. • Expect Results on mn (Gn) soon ※ Other Exotic/Speculative analysis under way • Preparation of Period-II DAQ Improved HPGe Conf. Commissioning 150+ kg CsI(Tl) [Welcome Ideas/Suggestions on Possibilities Beyond] • Diversified R&D Program in parallel

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