Starting Points (Collaboration ; Laboratories ; Scientific Program)

1. Towards kg-scale Ultra-Low-Energy Ultra-Low-Background Ge Detector • Starting Points (Collaboration ; Laboratories ; Scientific Program) • Potential Physics with ULE-ULB-Ge • Lessons and Experience from ULE-ULB-Ge Prototypes • Status & Plans & Discussions @ Henry T. Wong Academia Sinica , Taiwan. Canberra-Eurisys, Lingolsheim, Sept 2006

2. Objectives for this Visit : • Establish stronger collaborating relationships. • US : learn the technologies and future evolution in details • Canberra : understand/comment on our special needs and plans &how we use the detectors • Learn status of segmented 20 g and discuss how to use it optimally for our goals. • Discuss various aspects of possible scale-up to O(1 kg) : how realistic, how much, how long, how to fund …. Etc. • Personal scientific curiosity …..

3. Leading government-funded basic research organization in Taiwan • physical & biological sciences, humanities in ~30 institutes • Like Max Planck Institutes in a centralized campus. • One of the biggest institutes in AS ; ~ 300+ staff with ~40 research faculties • Work on nano-science, biophysics, complexities & nuclear+particle physics

4. TEXONO Collaboration Taiwan EXperiment On NeutrinO Collaboration : Taiwan (AS, INER, KSNPS, NTU) ; China (IHEP, CIAE, THU, NJU) ; Turkey (METU) ; India (BHU) ; USA (UMD) Program: Low Energy Neutrino & Astroparticle Physics • Kuo-Sheng (KS) Reactor Neutrino Laboratory (Taiwan) Neutrino properties & interactions ; Axion Searches • Yang-Yang Underground Laboratory (S. Korea)[with KIMS Coll.] Dark Matter Searches • DiversifiedR&D Projects • Trace Radiopurity Techniques with AMS • Sonoluminescence ………

5. Part of the group at AS • Extended collaboration ~30 people

6. Poineering Efforts : “Zero-Background Experiment” ! • KS Expt:1st large-scale particle physics experiment in Taiwan • TEXONO Coll. : 1st big research Coll. % Taiwan & China 

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

8. Kuo Sheng Reactor Neutrino Laboratory Front Gate Front View (cosmic vetos, shieldings, control room …..) Configuration: Modest yet Unique Flexible Design: Allows different detectors conf. for different physics Inner Target Volume

9. Shielding Structures : Schematics

10. quality Detector requirements mass On-Going Data Taking & Analysis • SM s(ne) • T > 2 MeV • R&D : • Coh. (nN) • T < 1 keV Results : • mn(ne) • T ~ 1-100 keV Reactor Neutrino Interaction Cross-Sections 1 counts / kg-keV-day

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

12. Achieved: A 10-keV threshold kg-scale experiment at reactor site with “cpd”-background comparable to underground lab. • Evidence of cosmic-ray activation through various Ga-decays

13. Magnetic Moment Searches : Highlights • simple compact all-solid design : HPGe (mass 1 kg) enclosed by activeNaI/CsI anti-Compton, further by passive shieldings&cosmic veto • TEXONO data (571/128 days) ON/OFF)[PRL 90, 2003 ; hep-ex/0605006] • background comparable to underground CDM experiment : ~ 1 day-1keV-1kg-1 (cpd) • DAQ threshold 5 keV analysis threshold 12 keV • mn(ne) <7.2 X 10-11mB (90% CL) [preliminary]

14. Next Goals: • Develop 1) kg-scale experiment at 2) 100-eV threshold at the 3) same cpd-background level • Scientific subjects: 1) first obseravtion of nN coherent scattering ; 2) Dark Matter searches at low-mass range ; 3) improve on magnetic moments • First choice of Detector Technology : Ge  1) built on existing experience ; 2) LN2 instead of He temperature ; 3) more matured (??) at industry for scale-up.

15. e.g. at QF=0.25 & 100 eV threshold • Rate ~ 11 kg-1 day-1 • c.f. • nN @ accelerator ~ 1000 ton-1 yr-1 • ne-p (water) @ KS ~ 1 kg-1 day-1 Neutrino-Nucleus Coherent Scattering : Expected Interaction Rates at KS@different Quenching Factors forGe  nN sensitive region : T < 500 eV by-product : T>500 eV gives mn(ne)  ~ 10-11mBat ~ 1 cpd background

16. TEXONO  KIMS @ Y2L Expected sensitivity • Yangyang Lab (Y2L) [700 m of rock overburden] in S. Korea • Install 5 g ULB-ULEGe at Y2L • Study background and feasibility for CDM searches • may evolve into a full-scale (1 kg) CDM experiment Y2L

17. Quenching Factor Measurement for Ge at CIAE’s 13 MV Tandem Facility: • Goals for Oct 06 Run : • Get to sub-keV • Improve on present sensitivities

18. “Ultra-Low-Energy” HPGe Prototype • ULEGe – developed for soft X-rays detection ; easy & inexpensive & robust operation • Prototypes built [Canberra-Meriden] and studied : (I) 5 g at Y2L ; (II) 4 X 5 g at KS ; (III) 10 g at AS • Prototype being built [Canberra-Lingolsheim]: segmented 20 g • Scale-up options to O(1 kg) in multi-array orintegrated form (??) • threshold <100 eV after modest PSD ULEGe@KS ULEGe@Y2L

19. 5 g 10 g N=1 single element (5 g & 10 g) : Schematics

20. 4 X 5 g N=4 array : Schematics

21. Segmented 20g : Schematics • ♥ Under construction at Canberra-Eurisys

23. Auto LN2 Refill system for N=4 array Segmented 20 g : larger dewar , single reservoir ; prefer AMI-186 Series

24. System Schematic Diagram Typical signals: HPGe High gain (0~9keV) HPGe Low gain (0~100keV) CsI(Tl) channel (current signal)

25. CAEN VME: 4 Channel 12 bit 40 MHz ADC

26. System configuration

27. ULEGe Calibration Peaks: Ta, Ca, Cs, Ti, Mn, Fe, Cu X-ray random trigger for zero ♥ Would hope to have sub-keV calibration point (HOW ??)

28. sh=6us, high gain PSD I : Correlate two gains & shaping time sh=12us, super gain

29. Events near threshold sh=6us, high gain y-axis sh=12us, super gain x-axis energy=114.7283eV noise energy=137.8089eV signal

30. sh=6us, super gain sh=12us, high gain PSD II : Correlate with pre-trigger pulse shapes

31. KS events: signal sh=12us, high gain x-axis sh=6us, super gain y-axis energy=217eV energy=373eV

32. KS events: noise sh=12us, high gain x-axis sh=6us, super gain y-axis energy=151eV energy=177eV

33. ULE-HPGe Prototype Results PSD Cut Threshold ~ 100 eV • Calibrations by keV lines & “0” from random trigger • Single channel readout : PSD by two shaping times & gain • Achieved threshold < 100 eV : lowest for bulk radiation detectors ! – at regular background • Background measurements under way at KS & Y2L

34. Intensive studieson sub-keV background Background Measurements & Comparisons • Similar background at KS & Y2L • Apparent difference between 5 g & 1 kg due to scaling with surface area instead, reproduced in simulations • i.e. background can be ~ O(1 cpd) at > 1 keV range for 1 kg ULEGe in compact array form • Intensive studies of sub-keV background under way

35. Background comparison

36. Improved PSD ; dual-readout coincidence Scale up to compact 1 kg ; understand background source (g/n) ; improved shielding design AS better electronics noise levels Threshold Vs Background Plots

37. R&D Program towards Realistic O(1 kg) Size Experiments (both nN & CDM) : • measure & study background at sub-keV range at KS & Y2L ; design of active & passive shielding based on this. • compare performance of various prototypes • devise calibration scheme at sub-keV range • measure quenching factor of Ge with neutron beam • develop advanced PSD techniques to further suppress noise-edge reduce threshold • studying scale-up options ULEGe-detector • Discrete elements Vs segmented Ge • dual readout channels to suppress electronic noise • keep other detector options open

38. A Possible Design : • 3X3X5 elements @ 20 g each (i.e. 900 g) • Dual readout per element • veto ring  lids 2D Projection 1X1 + ring , dual readout prototype available Oct 06.

39. Time Scale & Plans : • To Demonstrate with segmented 20 g : give 100 eV treshold (after all analysis work), project background ~cpd level at 100-500 eV (with Ge-active-veto) • Can submit proposal for 1-kg ULEGe by then (summer 2007 ??) • Construction can start as soon as end 2007 depending on a) prototype results; b) AS funding approval ; and c) any flexibilities in staging of construction & payment (to be discussed). • Scientific Goals  R&D plans/results were known and viewed with anticipation in the field of neutrino physics • presentations in numerous international conferences [WIN05-Delphi ; TAUP05-Zaragoza ; n06-Santa Fe ; ICHEP06-Moscow ; NDM06-Paris ……]

40. Summary & Outlook • Kuo-Sheng Neutrino Lab.: • Established & OperationalModular & Flexible Design ※Unique HPGe Low Energy Data (@10 keV threshold) ※Bkg Level ~ Underground CDM Expt. • Results on mn(Gn)Other Program under way • Future goal :anO(1 kg)+100 eV thresholdexpt. observeneutrino-nucleus coherent scatteringperformLE-CDM experiment  improve on magnetic moment sensitivity • R&D program pursued : • optimization of prototype ULEGe’s @ ~100 eV threshold • first background measurement in the 100 eV – 1 keV region • investigate scale-up options  Open up a New Detection Channel & New Detector Window

41. Some Output from 2006/9/1 Discussions : • Optimization of detector volume constrained by a) perimeter and b) thickness • Constraints : diameter < 85 mm ; thickness < 10 mm • Keen to see how to dual-channel-correlation studies work out • Try studying pulse shapes of raw pre-amp pulse AFTER AC-coupling • Can HV side be a single channel ? i.e. what’re its roles : for PSD or PSD+energy • Minimize length to bring out contacts : i.e. prefer no “inland” channels • Expect new product in 2007 on electrical-cryo-system that can go below liquid nitrogen temperature.