1. 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

2. 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 MeV) and low energy part of spectrum is not accurately known For (ne-e), both NC & CC and their interference term contribute g

3. 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

4. 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
= (3 – 4.5 MeV)
Standard Model = (1.5 – 3 MeV)
“Sin2qW was observed but there is NOT YET any real measurement for reactor neutrino”.

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

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

7. 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]

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

9. 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

10. CsI(Tl) Array : Highlights
40 cm length; 186 kg mass
(longest commercial prod.)
Energy+3D info:
 10% 660 keV
Z-position resolution is keV
 s(z) <2 cm @ E>250 keV
Detector Threshold 3 MeV
Range of O ( 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

11. 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 ?

12. 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.

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

14. 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)

15. 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)

16. 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

17. 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; .

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

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

20. 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 cm
Narrow Pulse
Normal Pulse
Alpha Pulse

21. Cut Summary
Cut Type All energy Above 3 MeV Efficiency (Suppression) (Suppression) [1] Raw data [2] Cosmic ray [3] anti-Compton [4] Single Trigger [5] Alpha [6] Double Pulse (Left side & Right side)
* Z-position cut is not applied !!

22. Period-2 CsI(Tl) Array : Results (Prilim.)
Energy Spectrum of recoil electron
Above 3 MeV
Counts/day/kg = (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 days OFF period
# O f Events = 190

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

24. Period-2 CsI(Tl) Array : Results (Prilim.)
1228 kg - days Energy Spectrum of recoil electron
Above 3 MeV
Counts/day/kg = (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 days OFF period
211 kg-days Energy Spectrum of recoil electron

25. 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)

26. 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.

27. 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.

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

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

30. 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 !!

31. 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 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]

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

33. Expected Sensitivities !

34. Summary
Present Results (1228 kg-days): # Bkg = kg -1day -1 > 3 MeV SM Expect: = 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 ) 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 !