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Gamma-induced positron lifetime and age-momentum correlation measurements of water at temperatures between 20 °C and 90 °C. Gamma-induced positron lifetime and age-momentum correlation measurements of water at temperatures between 20 °C and 90 °C. Content : - PowerPoint PPT Presentation
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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
2 / 17Maik 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
3 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Detector setup
pulsed beam of brems strahlung from superconducting electron LINAC ELBE 4 coincident setups for Age-MOmentum Correlation (AMOC )
Gamma-induced Positron Spectroscopy – GiPS
up to 16 MeV, 0.7 mA 5 ps bunch width 38 ns between each bunch
~ 300 cps 12 hours for 106 counts in AMOC spectrum of water
4 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Gamma-induced Positron Spectroscopy (GiPS)
Positron lifetime measurement
time structure of e- beam maintained for photon beam accelerator pulse serves as start signal gate on 511 keV at HPGe and BaF2
Start StopLifetime
t = 5 ps
5 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Gamma-induced Positron Spectroscopy – GiPS
projection ontime axis
projection on energy axis
energy and timing information of the same annihilation
event
Age-MOmentum Correlation – AMOC
6 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
GEANT4 simulations
beam direction
GEometry ANd Tracking – GEANT4
GEANT4: S. Agostinelli et al. Nucl. Instr. Meth. A 506 (2003), 250-303
Simulation of particle transport and interaction with matter using Monte Carlo methods
→ smearing up to ~ 10 mm in z direction
Distribution of positron generation by pair production and annihilation
7 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
GEANT 4.0 simulations
Place Generated positrons
AnnihilatedPositrons
Water 99.0 % 99.7 %
Kapton tube 1.00 % 0.30 %
Yield6 MeV
16 MeV0.06 % 0.26 %
0.05 %0.15 %
“Source contribution“ and dose rate
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
8 / 17Maik 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
9 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Positron lifetime spectroscopy at GiPS
Duplâtre – Phys. Status Solidi A, Vol. 6, Issue 11, 2476-2481 (2009)Kotera et al. – Phys. Lett. A, Vol. 345, 184-190 (2005)
Results
no source correction necessary for fit good agreement to published data, just intensity of free annihilation is lower
10 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Positron lifetime spectroscopy at GiPS
Effect on annihilation components:
→ Ie+ decreases→ IPs increases
Influence of oxygen on positron lifetimes
This explains the lower intensity of the free e+ annihilation component
oxygen acts as scavenger for radicals and e-
aq
11 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Time dependent S parameter – S(t)
calculating S parameter for each curve
extractingDoppler curves
12 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Time dependent S parameter – S(t)
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?
Motivation – “quantum beats“ in water
13 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Time dependent S parameter – S(t)
no periodic behaviour of S parameter changes (increases) for temperatures between 50 and 90 °C
Dependence on temperature
14 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Time dependent S parameter – S(t)
differences in curves for different statistics of the S(t) curves
no reproducable results of periodic changes in S parameter
no quantum beats werefound for T = 21… 90 °C using the GiPS setup.
Dependence on statistics
15 / 17Maik 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
16 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Many thanks to my collaborators …
Wolfgang Anwand, Thomas E. Cowan, Andreas Hartmann, Andreas Wagnerand 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 !
17 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
GiPS – Gamma-induced Positron Spectroscopy
Lifetime & Doppler broadening Spectroscopy, Age-Momentum Correlation user dedicated facility, application for beam time twice a year (14.11.2011)
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
18 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
19 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
20 / 17Maik 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?
21 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
GEANT 4.0 simulations
Photon beam hitting the Kapton tube
bremsstrahlung up to 6 and 16 MeV calculated with beam diameter = 41 mm
beam direction
22 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
GEANT 4.0 simulations
→ smearing up to ~ 10 mm in z direction
Distribution of positron generation by pair production and annihilation
beam direction
23 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Positron lifetime spectroscopy at GiPS
Local variance minimum for 2 = 400 ps for all temperatures
24 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Time dependent S parameter – S(t)
21 °C 50 °C 60 °C 70 °C 80 °C 90 °C
1 0.750.45,0.575
0.40.55
0.92 0.410.82
0.70.55
0.40.55
2 1.2 1.45, 1.64
0.751.15
1.34 0.81.25
1.251.65
0.950.75
Peak differences
25 / 17Maik Butterling | Institute of Radiation Physics | http://www.hzdr.de
Time dependent S parameter – S(t)
comparable to recently reported dataHirade – Chem. Phys. Lett., Vol. 480, 132–135 (2009 )
Comparison with recently published data
