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: Gamma-induced Positron Spectroscopy – GiPS Simulations using GEANT4 Positron lifetime spectroscopy at GiPS Time dependent S parameter – S(t) Conclusions

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 )

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 t = 5 ps Start Lifetime Stop

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

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

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

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

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)

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

Time dependent S parameter – S(t) extracting Doppler curves calculating S parameter for each curve

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?

Time dependent S parameter – S(t) Dependence on temperature no periodic behaviour of S parameter changes (increases) for temperatures between 50 and 90 °C

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.

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

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 !

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)

Is there any effect on the positron lifetime components? GEANT 4.0 simulations Radiolysis of water Is there any effect on the positron lifetime components?

GEANT 4.0 simulations Photon beam hitting the Kapton tube direction bremsstrahlung up to 6 and 16 MeV calculated with beam diameter = 41 mm

GEANT 4.0 simulations Distribution of positron generation by pair production and annihilation beam direction → smearing up to ~ 10 mm in z direction

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

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 2 1.2 1.45, 1.64 1.15 1.34 0.8 1.25 1.65 0.95

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 )