Lifetime measurement of o-Ps in NaI(Tl) scintillator Diana Seitova - PowerPoint PPT Presentation

Lifetime measurement of o-Ps in NaI(Tl) scintillator Diana Seitova Hayato Nishimiya Yasunori Sawada Yuta Sato Friday, December 25, 2015 Fourth-year students in the Department of Physics Osaka Univ.

Overview 1 . Introduction 2 . Experimental setup 3 . Results 4 . Analysis 5 . Conclusion 6 . Future 2

1.INTRODUCTION ①What is ortho-positronium? ②Theoretical Story ③Motivation 3

①What is ortho-Positronium? Bound state of e and e + - o-Ps → ３γ 4 ortho para Spin parallel state (S = 1) Spin antiparallel state (S = 0) p-Ps → 2γ

②Theoretical Story QED prediction : Definition of the lifetime τ: 5 N ( t ) = N (0) exp( − t/ τ )

②Theoretical Story ・Pick-off 2γ ・Spin-flip ・Chemical reaction Reactions of Positronium with materials ←Silica aerogels with hydroxyl surface are extremely hygroscopic by Y.S. by Y.S. 6 To reduce these reaction, We use SiO2 aerogel (low density of electron)

③Motivation of our research ・In order to test QED for the bound system. Purely leptonic, no contamination in low energy ! 7

2.EXPERIMENTAL SETUP ① Systematic diagram of apparatus ② HV Setup ③ TDC Calibration ④ ADC Calibration ⑤ Testing 8

①Systematic diagram of apparatus Experimental Apparatuses ・Positron Source 22Na ・Silica aerogel ・Plastic scintillator ・NaI(Tl) scintillator ・CAMAC modules (Density and grain size are unknown.) (thickness = 350μm) 9 �

Experimental Scheme by Y.S. Trigger (Start) TDC Stop ~50mm 10

Arrangement by Y.S. Silica aerogel sensitive volume PMT NaI(Tl) 11

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22Na Source 13

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②HV Setup 1400 Gain Adjustment of NaI(Tl) #0 SCA[012]/SCA[12] Voltage [V] 2600 2200 1800 1000 0.8 0.6 0.4 0.2 0 measuring the plateau curve. 15 • Determination of applied voltage for each PMT by

・The threshold voltage for discriminator is the 60 ※For trig plastic, chosen the level to remove noise. ※For trig plastic, chosen voltages signal being visible. seen from plateau curve. ・We determined the voltages to apply to PMTs, 30 NaI #2 30 NaI #1 30 NaI #0 Trig. Plastic minimum value of the specification. V_TH (mV) 1450 NaI #2 1600 NaI #1 1600 NaI #0 1200 Trig. Plastic HV (V) 16

③TDC Calibration Block diagram for TDC calibration 17

③TDC Calibration TDC value [ch] y = 3.7862x - 60.319 50 40 30 20 10 0 delay time [nsec] 140 120 100 80 60 40 20 0 18 Time [ nsec ] = TDC [ ch ] + 60 . 319 3 . 7862

④ADC Calibration Block diagram for ADC calibration. 19

ADC Calibration with energy ADC Counts NaI #0 20

④ADC Calibration Energy [keV] NaI #0 [ch] NaI #1 [ch] NaI #2 [ch] 1579±0.5 1302±0.4 1498±0.4 661.7 1221±0.3 1035±0.3 1167±0.3 511.0 109.5±0.0 106.8±0.0 53.82±0.01 0 21 E 0 [ keV ] = (0 . 477 ± 0 . 005) × ADC [ ch ] − 50 ± 6 E 1 [ keV ] = (0 . 528 ± 0 . 008) × ADC [ ch ] − 30 ± 7 E 2 [ keV ] = (0 . 453 ± 0 . 008) × ADC [ ch ] − 48 ± 9

⑤Testing First, ・We must check whether ortho-positronium is really formed in Silica aerogel. We collected 3 million events in 12/18 ~ 20 using Aerogel, And for comparison, collected 1 million events in 12/21 without aerogel. 22

Block diagram of the data-acquisition electronics 23

3.RESULTs 24 • TDC Histogram (Time distribution) • ADC Histogram (Energy spectrum) • Correlation plot

Time distribution with aerogel NaI #0 NaI #1 NaI #2 25 Time[ns] Counts

Energy spectrum NaI #0 NaI #1 NaI #2 26 with aerogel Energy[keV] Counts

Correlation plot NaI #0 NaI #1 NaI #2 27 with aerogel Energy[keV] Time[ns]

Time distribution without aerogel NaI #0 NaI #2 NaI #1 28 Time[ns] Counts

Energy spectrum without aerogel NaI #0 NaI #2 NaI #1 29 Energy[keV] Counts

Correlation plot without aerogel NaI #2 NaI #0 NaI #1 30 Energy[keV] Time[ns]

4.ANALYSIS 31 • Time Walk Correction • Lifetime • Effect of Aerogel

Time Walk Correction 32 h ∝ Energy A Time = Energy + B

Time Walk Correction NaI#0 NaI#1 NaI#2 Fitting range : 200~500keV 33 Energy[keV] Time[ns] • aerogel

Time Walk Correction NaI#0 NaI#1 NaI#2 34 Time[ns] Energy[keV] • aerogel

Time Walk Correction NaI#0 NaI#1 NaI#2 35 Time[ns] Energy[keV] • without aerogel

Lifetime Blue : aerogel Red : without aerogel NaI#0 NaI#1 NaI#2 36 Time[ns] Counts

Lifetime (30~200keV) Blue : aerogel Red : without aerogel NaI#0 NaI#1 NaI#2 37 Counts Time[ns]

Lifetime (200~450keV) Blue : aerogel Red : without aerogel NaI#0 NaI#1 NaI#2 38 Counts Time[ns] : Fitting range

Lifetime (200~450keV) ・NaI#0 (Fit : 130~210ns) ・NaI#1 (Fit : 140~220ns) ・NaI#2 (Fit : 130~210ns) aerogel : 141±16 [ns] without aerogel : 132±28 [ns] aerogel : 146±17 [ns] without aerogel : 118±26 [ns] aerogel : 140±15 [ns] without aerogel : 160±38 [ns] 39 � �

Lifetime (450~900keV) Blue : aerogel Red : without aerogel NaI#0 NaI#1 NaI#2 40 Counts Time[ns]

The Energy Sum ・Peak Energy aerogel : 919.5±6.0keV Blue : aerogel Red : without aerogel without aerogel: 917±17keV 41 cut:200～450keV for each channel

5.CONCLUSION between with aerogel and without aerogel. expected peak(around 1MeV) 42 • Peak of energy sum event is not so different • On the energy sum plot, We couldn’t get

6.FOR FUTURE “without aerogel. 43 • To reduce 2γ events. • To understand strange peak in TDC. • Difference between “with aerogel” and • To change the condition of aerogel. • Trying to set a vacuum condition.

2γ Events So many events around 500keV NaI#2 NaI#1 NaI#0 44 counts Energy(keV)

2γ Events There are many gap around scintillator →We will change the position of leads block

Strange peak strange peak around 350ns NaI#0 NaI#2 NaI#1 46 Time(ns) counts

Strange peak strange peak around 250ns NaI#0 NaI#1 NaI#2 Time walk version 47 Time(ns) counts

Time correlation NaI#0:NaI#1 NaI#0:NaI#1(time walk) There is no correlation between two NaI’s 48 NaI(1) Time(ns) NaI(0) Time(ns)

Strange peak The problem is caused by This part 49

Energy Sum Events Blue : aerogel Red : without aerogel 50 We have little time for analysis. To get certain difference between with aerogel and without aerogel, We will analyze more than now Energy[keV] counts

Any other for future a vacuum condition. • Aerogel is now wet, so we will dry it. • When we get good 3γ data, we will try to set

Thanks for your attention! 52

References [1]今坂俊博, 原口弘, 森哲平, “大気中でのオルソポジトロニウムの寿命測定” (2015) [2]宮崎康一, 山内洋子, 矢島和希, “大気中でのオルソポジトロニウムの寿命測定” (2014)

Positron Deposition Energy in plastic

Positron Deposition Energy in plastic

③Theoretical Story Disintegration of Positronium C-Parity of two spin-1/2 particles state: At ground state, n photons have odd C-parity ; Conservation of C-parity C = ( − 1) L + S L = 0 ⇢ 1 ( S = 0) C = − 1 ( S = 1) C γ = ( − 1) n para Ps ( S = 0) → 2 γ , 4 γ , 6 γ , ... ortho Ps ( S = 1) → 3 γ , 5 γ , 7 γ , ...