Venktesh Singh Academia Sinica, Taiwan Performance and Physics with the CsI(Tl) array at the Kuo-Sheng Reactor Neutrino Laboratory Venktesh Singh Academia Sinica, Taiwan Physics with CsI(Tl) Detector Period – 2 CsI(Tl) Detector Extension of Effective dynamic range of FADC Data Analysis Techniques Cut Summary Period – 2 Results (Prilim.) Background Understanding Status and Plans Summary

Physics with CsI(Tl) detcetor n physics full of surprises , need intense n-source Reactor : high flux of low (MeV range) energy electron anti-neutrinos ne + p e+ + n Reactor n-spectrum has been measured (~2% in the 3 - 7 MeV) and low energy part of spectrum is not accurately known For (ne-e), both NC & CC and their interference term contribute g

World status ! General conclusion is that a 1% measurement is well-worth pursuing ! “There is NOT YET any real measurement of reactor neutrino expt”. TEXONO Qw(Cs) NuTeV Czarnecki & Marciano (2000) E158 Run I+II (Preliminary) PDG2002 Measurements of sin2qw as a function of Q. The curve shows the Standard Model expectation

World status ! Experiments Savannah Kurtchatov Rovno NUMU TEXONO Target Fid. Mass Thr. (MeV) Signal Evt. / D S / B Accuracy of s(nee) Plastic scin. 15.9 kg 1.5 1.2 0.18 29%* Fluorocarbon 103 kg 3.1 0.78 0.1 53% Si(Li) 37.5 kg 0.6 5.2 0.008 49% CF4 gas 21 kg 0.9 1.77 0.2 50% CsI(Tl) cry. 100 kg 3.0 1.5 (expect) 0.25 (current) 37% (current) 20% (goal) Characteristics of the previous and current neutrino-e scattering experiments * Measurement – Standard Model = 2.0 +- 0.5 (3 – 4.5 MeV) Standard Model = 1.35+-0.4 (1.5 – 3 MeV) “Sin2qW was observed but there is NOT YET any real measurement for reactor neutrino”.

Attainable sensitivities in ne- e scattering The different symbols for the ranges R1 & R1correspond to the different values of the measurement error ddet.

Period II : Jan.28, 2003 – Jan.08 2004 ( 50 days OFF) KS Expt. : Period II Configuration Period II : Jan.28, 2003 – Jan.08 2004 ( 50 days OFF) Shielding & Veto [one side] CsI(Tl) Array (186 kg)

KS Expt: Period II CsI(Tl) Detector CsI(Tl) [ 186 kg ] Connecting Board Flash ADC Readout Multi-Disks Array [800 Gb] [16 ch, 20 MHz, 8 bit]

Reactor Neutrino Interaction Cross-Sections P2: SM (ne) > 3 MeV P3+: Coh. (nN) < 1 keV P1: MM (ne) 1-100 keV

CsI(Tl) crystal layout of P-II (93 cry. 186 kg) 95 88 91 79 70 72 77 85 86 54 57 76 75 74 73 51 87 42 96 58 62 61 65 26 101 25 24 59 55 53 67 93 220 13 21 27 45 94 32 63 19 23 11 05 43 50 80 49 64 16 35 10 83 92 66 33 46 40 41 34 17 81 78 68 31 89 08 39 99 15 48 47 44 69 20 38 14 90 60 56 71 82 97 22 98 06 04 02 37 12 03 52 100 Plastic 20+20 cm 40 cm 7 central cry. Anal. underway

CsI(Tl) Array : Highlights 40 cm length; 186 kg mass (longest commercial prod.) Energy+3D info:  10% FWHM @ 660 keV Z-position resolution is 2 cm @ 660 keV  s(z) <2 cm @ E>250 keV Detector Threshold 3 MeV Range of O (0.0407 cpd) [counts/kg/day] > 3 MeV background PSD for g/a : > 99% Data Volume : Total > 250 / 50 days ON/OFF Goals: Commission 500 kg target on-site DAQ with large dynamic range

Extension of Effective Dynamic Range of 8-bit FADC Motivations:- What is the dynamic range of an n-bit FADC, beyond the nominal 2n value ? That is, can the crucial information like the total area as well as the rise and fall times be reconstructed, even though part of the pulse is not recorded ?

Extension of Effective Dynamic Range of 8-bit FADC Method:- Make a reference pulse of unsaturated events. Used pulse analysis approach for charge summation. From a standard reference pulse shape, a relationship is obtained between the “saturated charge (Qsat)” defined by the integration of the saturated events and the “total charge (Qtot)” from that of the raw fully recorded pulse. Qtot = Sk=03 akQsatk The coefficients ak are obtained from minimum c2-fits.

Extension of Effective Dynamic Range of 8-bit FADC Results:-

Extension of Effective Dynamic Range of 8-bit FADC Results:- (a) The ratios of peak positions between the 662 and 32 keV g-lines before and after saturated pulse correction; (b) the rations of peak positions at different time-bin records, and (c) the energy resolution at 662 keV for the corrected spectra, as functions of the expected peak amplitudes. Charge reconstruction and event identification via pulse shape analysis are achieved. Effectively extending an 8-bit FADC by at least FOUR more bits. The algorithm is valid so long as the unsaturated interval is more than 2% of the FADC recording period. Published in Nucl. Instrum. & Methods in Phys. Res. A 511, 408 (2003)

Period-2 CsI(Tl) Array : 186 kg, 93 crystals Single Crystal QL Vs QR (Raw Data) Z = 0 cm Z =40 cm 208Tl 40K 137Cs Region of Interest for SM s(ne)

Data Analysis Techniques No Cut: Energy Spectrum Defining Cuts: 1] General Cuts – a) No Cut energy spectrum b) Single Event Hit & Single Crystal Hit c) Cosmic ray Cut d) Rough Z-pos. cut SEH, SCH SEH, & SCH SEH, SCH, & Cosmic SEH, SCH, Cosmic-ray, & Z-pos SEH, SCH SEH, SCH SEH, SCH

Data Analysis Techniques Normal Event Pulse Alpha Event Pulse Defining Cuts: 2] Special Cuts – a) Alpha Event Cut (having fast decay time) Check- Alphas are located around 2 MeV Select- event having Time average less than 40 A; .

Data Analysis Techniques Defining Cuts: 3] Special Cuts – a) Double Event Cut (Left side double pulse) b – a pulse !

Data Analysis Techniques Defining Cuts: 4] Special Cuts – a) Double Event Cut (Right side Double Pulse)

Data Analysis Techniques 40cm long crystal No cut Defining Cuts: 3] Z-position Cut – Select – Both side peak mean initially taken as 0 & 40 ! 0 cm 40 cm Narrow Pulse Normal Pulse Alpha Pulse

Cut Summary Cut Type All energy Above 3 MeV Efficiency (Suppression) (Suppression) [1] Raw data 1.00 1.00 1.00 [2] Cosmic ray 0.11 0.88 0.93 [3] anti-Compton 0.70 0.86 0.99 [4] Single Trigger 0.01 0.02 0.99 [5] Alpha 0.10 0.83 1.00 [6] Double Pulse 0.11 0.38 0.99 (Left side & Right side) * Z-position cut is not applied !!

Period-2 CsI(Tl) Array : Results (Prilim.) Energy Spectrum of recoil electron Above 3 MeV Counts/day/kg = 0.011 (SM) Counts/day/kg = 0.126 137Cs (661 keV) 40K (1461 keV) 208Tl (2615 keV) * Included TOP layer crystals ! * NO 2 cm zpos (both side) cut !! * 42 Crystals (40 cm.) * Mass 84 kg * Data set 17.95 days OFF period # O f Events = 190

Period-2 CsI(Tl) Array : Results (Prilim.) = (ds/s) = 37 % ~ 3 s measurement After (I) improved energy resolution, (II) analyzing 25000 days ON and 5000 days OFF and (III) ON -OFF, we are expecting D = (ds/s) < 20 % < 5 s measurement !! ~ 50 % Events

Period-2 CsI(Tl) Array : Results (Prilim.) 1228 kg - days Energy Spectrum of recoil electron Above 3 MeV Counts/day/kg = 0.011 (SM) Counts/day/kg = 0.041 137Cs (661 keV) 40K (1461 keV) 208Tl (2615 keV) * 38 Crystals (40 cm) * 2 cm Z-position cut from both side * Mass 68.4 kg * Data set 17.95 days OFF period 211 kg-days Energy Spectrum of recoil electron

Period-2 CsI(Tl) Array : Results (Prilim.) The Estimate of BKG Suppression >3 MeV * Cosmic ~ one order * From Veto to All Cuts > Two order * 100kg All Cuts to ON-OFF ~ One order * S/B ratio (integral > 3 MeV) = 1/3.9 * D = (ds/s) = 37 % ~ 3s measurement ! 25000 kg-days ON-period 5000 kg-days OFF-period Differential Event Count for CsI(Tl)

Background Understanding PURPOSE: To measure/understand the concentrations of contaminants and # of events produced by them in region of interest, background subtraction. IDEA: Timing and position related β-α events or α-α events can provide distinct signature to identify the decay process and the consistency of the isotopes involved. REALIZATION: By monitoring the timing features of α events and utilizing PSD technique.

Background Understanding Two Type 1: Environmental bkg 2: Radioactive Contaminants 1] Basically : Cosmic Ray muons, Products of cosmic ray muons, Spallation neutrons and muon-produced isotopes 2] Decays of radioactive contaminants produce bkg Mainly 232Th and 238U chain in the region of interest 137Cs, and 40K are in lower energy side but 208Tl can affect.

Background Understanding Prospects:- Estimate the abundance of 238U and 232Th Figure out the contribution of the two chains to the spectrum of the background

Background Understanding 232Th  six alphas (4 - 9 MeV) CsI(Tl) quenching factor ~ 2.5  Five Bita (0.46 – 5.0 MeV)

Non-single-α events:- Background Understanding Non-single-α events:- 238U series: 214Bi(β-,19.7min) → 214Po(α,164μs) → 210Pb 232Th series: 220Rn(α,55s) → 216Po(α,0.15s) → 212Pb 212Bi(β-, 60.6min, 64%) → 212Po(α, 304ns) → 208Pb Understanding is underway !!

Status and Plans Attempt measurement of Standard Model s(nee-)  sin2qw at MeV range with high accuracy Analysis: [1]  All 47 (40 cm) + 3 (20+20 cm) crystals analysis for THREE week gone well (One 40 cm was bad)  42 (20+20 cm) is in progress Future Upgrades and Modifications of the Expt.:  Goal of achieving a 500 kg system [Now 7 more crystals installed]  Improvements of Shielding [Installing more shielding on TOP and inside the CsI(Tl) box]  More Physics Data Taking [Preparing for next period OFF data taking]

Shielding inside the Target Volume Boron loaded polyethylene 5 cm. Cu 5 cm.

Expected Sensitivities !

Summary Present Results (1228 kg-days): # Bkg = 0.041 +- 0.006 kg -1day -1 > 3 MeV SM Expect: = 0.011 kg-1day-1 > 3 MeV # S/B ratio < 1 / 3.9 Data taken = 250 days ON & 50 days OFF # Present projected sensitivity of s (nee) ~ 37 % Goal  20 % (at S/B ~ 1) [ improved analysis/ U+Th determination ] Efforts are going in RIGHT direction ! Internal intrinsic radioactivity: Multi-structure in Alpha spectrum (study is underway) Concentration of 137Cs = 1/e * ( 2.14 x 10-18 ) g / g * e is ~ 0.4 Underway  the concentration of Th and U contaminants ! !! After analyzing all crystals and after ON – OFF Data, we will have better results ! Thanking you for your attention !