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 @
Universität Dortmund, 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: ※ Fermilab
※ AMS on Space Shuttle & ISS
※ LHC
※ TEXONO program [this talk]
NTU: ※ KEK
※ LHC
NCU: ※ LEP
※ 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

4. TEXONO Overview Goals : Program : 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 n Lab:
28 m from
core#1

7. Kuo-Sheng Neutrino Laboratory
High flux of ne (also ….. ne )
Modular Design
 independent detector, 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. ULB-HPGe + Anti-Comptons
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: Experimental Probe:
 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: HPGe Performance: Analysis:
 Expected total 200/60 days ON/OFF
[ reported here : 62/46 ON/OFF ]
HPGe Performance:
 kg mass
 0.4 keV 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
Residual Plot
Fit OFF spectra to fOFF
E/keV fOFF c2/dof
a1e-a2E+a3+a4E 39/46
Fit ON spectra to
fOFF + fSM + mn2 fMM [10-10 mB]
Best Fit :
mn2 = -1.7  @ c2/dof = 55/49
[Comparable sensitivities to direct-search world limits]
Improvements Expected :
 more data [ 3+ ON]
 complete & improved analysis
 treatment of threshold region [e.g. timing]
[Aim : ~ 5 keV]

17. Reactor mn(ne) Sensitivities
Gn Sensitivities

18. KS/P1 Analysis HPGe : exploit the low threshold data
Established Problem:
mn and Gn for ne via
ne + e  nx + e
Speculative Analysis:
※ study ne flux from reactor
 due to neutron excitation producing
e.g. 51Cr, 55Fe [distinct energy & timing …..]
 study mn & 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) : Technical Run
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] ~ 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 < g/g (equil.)
 40K < 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 Upgrading FADCs Trace Radio-purity with AMS
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 Korea
 JHFBeijing LBL n IHEP
 Ultra HE (1015 eV) n 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
N KIMS Expt. (apprd.) :
 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 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
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 < g/g
 measure 40K~10-10 g/g in CsI (powder)
Sensitivity goal : 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