M. Butterling

Gamma-induced positron lifetime and age-momentum correlation measurements of water at temperatures between 20 °C and 90 °C

Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Gamma-induced positron lifetime and age-momentum correlation measurements of water at temperatures between 20 °C and 90 °C

Content:  Gamma-induced Positron Spectroscopy – GiPS  Simulations using GEANT4

 Positron lifetime spectroscopy at GiPS  Time dependent S parameter – S(t)  Conclusions

2 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Gamma-induced Positron Spectroscopy – GiPS Detector setup

 ~ 300 cps  12 hours for 106 counts in AMOC spectrum of water

 up to 16 MeV, 0.7 mA  5 ps bunch width  38 ns between each bunch  pulsed beam of brems strahlung from superconducting electron LINAC ELBE  4 coincident setups for Age-MOmentum Correlation (AMOC )

3 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Gamma-induced Positron Spectroscopy (GiPS) Positron lifetime measurement

t = 5 ps

Start

Lifetime

Stop

 time structure of e- beam maintained for photon beam  accelerator pulse serves as start signal  gate on 511 keV at HPGe and BaF2

4 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Gamma-induced Positron Spectroscopy – GiPS Age-MOmentum Correlation – AMOC

projection on energy axis

projection on time axis

energy and timing information of the same annihilation event

5 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

GEANT4 simulations GEometry ANd Tracking – GEANT4

Distribution of positron generation by pair production and annihilation

Simulation of particle transport and interaction with matter using Monte Carlo methods

beam direction

→ smearing up to ~ 10 mm in z direction GEANT4: S. Agostinelli et al. Nucl. Instr. Meth. A 506 (2003), 250-303

6 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

GEANT 4.0 simulations “Source contribution“ and dose rate

Place

Generated positrons

Annihilated Positrons

Water

99.0 %

99.7 %

Kapton tube

1.00 %

0.30 %

Yield 6 MeV 16 MeV

0.06 % 0.26 %

0.05 % 0.15 %

 no influence of Al caps or temperature sensor; Kapton tube can be neglected  dose rate for water at GiPS: ~ 1 mGy / s  positron generation within 20 cm³ → effect of radiolysis can be neglected

7 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Positron lifetime spectroscopy at GiPS Fixing second lifetime component

 three components fit using PALSfit  analysis by fixing 1 and 2 , and looking for minimum of chi2 → 2 = 400 ps

8 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Positron lifetime spectroscopy at GiPS Results

 no source correction necessary for fit  good agreement to published data, just intensity of free annihilation is lower Duplâtre – Phys. Status Solidi A, Vol. 6, Issue 11, 2476-2481 (2009) Kotera et al. – Phys. Lett. A, Vol. 345, 184-190 (2005) 9 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Positron lifetime spectroscopy at GiPS Influence of oxygen on positron lifetimes  oxygen acts as scavenger for radicals and e-aq Effect on annihilation components: → Ie+ decreases → IPs increases This explains the lower intensity of the free e+ annihilation component

10 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Time dependent S parameter – S(t)

extracting Doppler curves

calculating S parameter for each curve

11 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Time dependent S parameter – S(t) Motivation – “quantum beats“ in water

T. Hirade (Chemical Physics Letters 480 (2009) 132–135):  spin conversion of ortho-positronium can possibly be detected using AMOC  periodic changes in S(t) parameter = quantum beats

Our motivation:  AMOC spectra are part of GiPS  measurements for T = 21 … 90 °C  Can we confirm quantum beats?

12 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Time dependent S parameter – S(t) Dependence on temperature

 no periodic behaviour of S parameter changes (increases) for temperatures between 50 and 90 °C

13 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Time dependent S parameter – S(t) Dependence on statistics differences in curves for different statistics of the S(t) curves

no reproducable results of periodic changes in S parameter

no quantum beats were found for T = 21… 90 °C using the GiPS setup.

14 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Conclusion 

GiPS is suitable for the investigation of liquids



radiolysis effects due to the use of bremsstrahlung can be neglected



temperature stabilized sample holder does not influence positron lifetime measurement → no source correction necessary



positron lifetime results fit well to published data



AMOC spectra can be measured within a fraction of usual time (days instead of weeks)



quantum beats could not be verified for temperatures between 20 … 90 °C

15 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Many thanks to my collaborators … Wolfgang Anwand, Thomas E. Cowan, Andreas Hartmann, Andreas Wagner and the ELBE crew for always stable beams Helmholtz-Zentrum Dresden-Rossendorf

Jörg Haeberle, Marco Jungmann, Reinhard Krause-Rehberg, Arnold Krille Martin-Luther-Universität Halle-Wittenberg

… and to you for your attention !

16 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

GiPS – Gamma-induced Positron Spectroscopy    

up to 16 MeV, 0.7 mA 5 ps bunch width 38 ns between each bunch temperature stability ± 0.5 °C

 bulky samples, liquids, disperspion, gases, powders, activated samples

 Lifetime & Doppler broadening Spectroscopy, Age-Momentum Correlation  user dedicated facility, application for beam time twice a year (14.11.2011)

17 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

18 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

19 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

GEANT 4.0 simulations Radiolysis of water

Is there any effect on the positron lifetime components?

20 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

GEANT 4.0 simulations Photon beam hitting the Kapton tube

beam direction

 bremsstrahlung up to 6 and 16 MeV  calculated with beam diameter = 41 mm

21 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

GEANT 4.0 simulations Distribution of positron generation by pair production and annihilation

beam direction

→ smearing up to ~ 10 mm in z direction

22 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Positron lifetime spectroscopy at GiPS Local variance minimum for 2 = 400 ps for all temperatures

23 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Time dependent S parameter – S(t) Peak differences 21 °C

50 °C

60 °C

70 °C

80 °C

90 °C

1

0.75 0.45,0.575

0.4 0.55

0.92

0.41 0.82

0.7 0.55

0.4 0.55

2

1.2 1.45, 1.64

0.75 1.15

1.34

0.8 1.25

1.25 1.65

0.95 0.75

24 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de

Time dependent S parameter – S(t) Comparison with recently published data

 comparable to recently reported data Hirade – Chem. Phys. Lett., Vol. 480, 132–135 (2009 )

25 / 17 Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de