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