Response time of an Indium ion-doped zinc oxide scintillator is measured to be ~3 ps, an improved... more Response time of an Indium ion-doped zinc oxide scintillator is measured to be ~3 ps, an improved of almost 50 times compared to the previously reported Iron ion-doped counterpart. Intentional impurityion doping introduces additional fluorescence quenching channels that facilitate shortening of the response time. This improved response time allows timing control between x-ray free electron laser pulses and a femtosecond laser to within a few picosecond accuracy.
Proceedings of the Samahang Pisika ng Pilipinas, 2013
We studied lanthanide-doped 20Al(PO3)3-80LiF, or simply APLF, as scintillator for neutron detecti... more We studied lanthanide-doped 20Al(PO3)3-80LiF, or simply APLF, as scintillator for neutron detection. Lanthanide-doped APLFs had faster fluorescence decay times by about 10 ns compared to a standard scintillator, GS2. Nd-doped APLF exhibited the fastest decay time of 6.6 ns. The fluorescence of the Pr-doped and GS2 using different radiation sources were also compared. The Pr-doped APLF had faster decay time compared to GS2 regardless of the radioactive excitation source. We demonstrated the potential of the Pr-doped APLF as a scintillator by neutron diagnostics. Lanthanide- doped APLFs can be better alternatives to conventional scintillators. We envision further developments of lanthanide-doped APLF-based neutronscintillators.
The energy coupling efficiency (CE) in Fast Ignition (FI) laser fusion was studied at GEKKO XII a... more The energy coupling efficiency (CE) in Fast Ignition (FI) laser fusion was studied at GEKKO XII and LFEx laser facility by using newly developed targets and plasma diagnostic instruments. The gated-liquid scintillator neutron detectors had been upgraded by using neutron collimators for intense background fluxes of γ-rays and neutrons in the FI experiment. Clear fusion neutron signal was successfully recorded in the sub-kJ heating FI experiment. Up to 5 times neutron yield enhancement was observed, and the CE of the heating laser to core plasma was estimated to be 1.6% for cone-in-shell target implosion by 9 beams and core heating by LFEX pulse 115 ps before bang time. The laser-to-electron energy conversion efficiency was separately diagnosed using a newly developed target and resulted to be 45%. The fast electron energy spectrum was estimated to be 2.3 MeV slope temperature by hard x-ray spectroscopy. Monte Carlo simulations demonstrate the consistency of the data set.
We report on the room-temperature optical emissions of hydrothermal-grown zinc oxide (ZnO) nanost... more We report on the room-temperature optical emissions of hydrothermal-grown zinc oxide (ZnO) nanostructures. The nanostructures were fabricated on seeded silicon (Si) substrates by hydrothermal growth method using different zinc acetate dihydrate [Zn(CH3COO)·2H2O, ZnAc] concentrations. Regardless of the ZnAc concentration, all nanostructures exhibit well-defined hexagonal facets and intense near-band-edge ultraviolet (UV) emissions. However, increasing the ZnAc concentration leads ZnO nanostructures which exhibit longer emission lifetimes and a secondary red-shifted UV emission around 392 nm. These changes in the nanostructures' UV emission properties are attributed to the multiple excitation/absorption and emission processes of coalescent structures and/or structures sharing common sides or boundaries. Our results suggest that for UV scintillator applications, this phenomenon in ZnO nanostructures can be reduced by using lower (< 100 mM) ZnAc concentrations during hydrothermal...
The development and characterization of the optical properties of a neodymium(III)‐doped 42.75AlF... more The development and characterization of the optical properties of a neodymium(III)‐doped 42.75AlF3–33.25CaF2–19BaF2–5YF3 (Nd3+‐doped BCA‐5Y) glass in the vacuum ultraviolet (VUV) region are reported. Photoluminescence peaks at 180 and 227 nm are observed upon excitation with the 157 nm emission of a F2 laser. The dominant 180 nm emission peak is assigned to the 4f25d–4f3 (4I9/2 level) transition in Nd3+. This emission peak exhibits a fast, single exponential luminescence with a 16 ns decay time. The strong luminescence intensity and the fast decay time allude to its prospects for scintillator applications.
First-principles density functional calculations together with experimental measurements demonstr... more First-principles density functional calculations together with experimental measurements demonstrate that pressure (uniform and uniaxial) increases the band gap of a perfect lithium hexafluoroaluminate (LiCaAlF6, LiCAF) crystal. As fluoride crystals can be highly transmitting at vacuum ultraviolet wavelengths, crystal modifications that further increase the band gap are highly sought after for future Vacuum ultraviolet applications. Through an extensive series of density functional theory simulations, we demonstrate that the band gap increases monotonically from 12.2 eV to 14.1 eV with the application of uniform pressure. Through joint theoretical and experimental investigation, we explore different uniaxial compressions that can be achieved through cutting-edge laser-shock compression. We find that uniaxial pressure also increases the LiCAF band gap by 0.3 and 0.4 eV for a- and c-axis compressions, respectively.
Conference on Lasers and Electro-Optics 2010, 2010
Experimental results are presented on the properties of a custom-designed fast-response lithium-6... more Experimental results are presented on the properties of a custom-designed fast-response lithium-6 glass scintillator for inertial confinement fusion diagnostics. This newly developed scintillator promises as an indispensable tool in the realization of scattered neutron diagnostics.
International Quantum Electronics Conference, 2005.
It has been known that the surface-field THz emission in a semiconductor and in a semiconductor q... more It has been known that the surface-field THz emission in a semiconductor and in a semiconductor quantum well occurs when a short laser pulse creates electron-hole (e-h) dipoles that are accelerated in opposite directions by the surface electric field. The accelerating charges emit a THz transient signal [1]. Other mechanisms include intersubband spontaneous emissions and the excitation of quantum beats in the quantum well subbands [2]. In these scenarios, it is always surmised that the energy of the excitation laser pulse is higher than the bandgap of the semiconductor for it to be able to create photogenerated e-h pairs. In this work, we present initial results showing surface field THz radiation of a narrow and wide uncoupled GaAs/AlGaAs multiple quantum well (MQW) heterostructures for excitation energies lower than the bandgap. Furthermore, the emission enhancement and suppression effects of an externally applied magnetic field (B-field) are also investigated.
... E. Estacio,' A. Quema.l' G. Diwa,' G. De los Reyes,' H. Murakami,1 S. Ono... more ... E. Estacio,' A. Quema.l' G. Diwa,' G. De los Reyes,' H. Murakami,1 S. Ono,' N. Sarukura,' A. Somintac.? ... The effect ofthe externally applied magnetic field parallel to the MQW plain is to enhance or reduce the THz emission intensity for the up or down direction, respectively. ...
Response time of an Indium ion-doped zinc oxide scintillator is measured to be ~3 ps, an improved... more Response time of an Indium ion-doped zinc oxide scintillator is measured to be ~3 ps, an improved of almost 50 times compared to the previously reported Iron ion-doped counterpart. Intentional impurityion doping introduces additional fluorescence quenching channels that facilitate shortening of the response time. This improved response time allows timing control between x-ray free electron laser pulses and a femtosecond laser to within a few picosecond accuracy.
Proceedings of the Samahang Pisika ng Pilipinas, 2013
We studied lanthanide-doped 20Al(PO3)3-80LiF, or simply APLF, as scintillator for neutron detecti... more We studied lanthanide-doped 20Al(PO3)3-80LiF, or simply APLF, as scintillator for neutron detection. Lanthanide-doped APLFs had faster fluorescence decay times by about 10 ns compared to a standard scintillator, GS2. Nd-doped APLF exhibited the fastest decay time of 6.6 ns. The fluorescence of the Pr-doped and GS2 using different radiation sources were also compared. The Pr-doped APLF had faster decay time compared to GS2 regardless of the radioactive excitation source. We demonstrated the potential of the Pr-doped APLF as a scintillator by neutron diagnostics. Lanthanide- doped APLFs can be better alternatives to conventional scintillators. We envision further developments of lanthanide-doped APLF-based neutronscintillators.
The energy coupling efficiency (CE) in Fast Ignition (FI) laser fusion was studied at GEKKO XII a... more The energy coupling efficiency (CE) in Fast Ignition (FI) laser fusion was studied at GEKKO XII and LFEx laser facility by using newly developed targets and plasma diagnostic instruments. The gated-liquid scintillator neutron detectors had been upgraded by using neutron collimators for intense background fluxes of γ-rays and neutrons in the FI experiment. Clear fusion neutron signal was successfully recorded in the sub-kJ heating FI experiment. Up to 5 times neutron yield enhancement was observed, and the CE of the heating laser to core plasma was estimated to be 1.6% for cone-in-shell target implosion by 9 beams and core heating by LFEX pulse 115 ps before bang time. The laser-to-electron energy conversion efficiency was separately diagnosed using a newly developed target and resulted to be 45%. The fast electron energy spectrum was estimated to be 2.3 MeV slope temperature by hard x-ray spectroscopy. Monte Carlo simulations demonstrate the consistency of the data set.
We report on the room-temperature optical emissions of hydrothermal-grown zinc oxide (ZnO) nanost... more We report on the room-temperature optical emissions of hydrothermal-grown zinc oxide (ZnO) nanostructures. The nanostructures were fabricated on seeded silicon (Si) substrates by hydrothermal growth method using different zinc acetate dihydrate [Zn(CH3COO)·2H2O, ZnAc] concentrations. Regardless of the ZnAc concentration, all nanostructures exhibit well-defined hexagonal facets and intense near-band-edge ultraviolet (UV) emissions. However, increasing the ZnAc concentration leads ZnO nanostructures which exhibit longer emission lifetimes and a secondary red-shifted UV emission around 392 nm. These changes in the nanostructures' UV emission properties are attributed to the multiple excitation/absorption and emission processes of coalescent structures and/or structures sharing common sides or boundaries. Our results suggest that for UV scintillator applications, this phenomenon in ZnO nanostructures can be reduced by using lower (< 100 mM) ZnAc concentrations during hydrothermal...
The development and characterization of the optical properties of a neodymium(III)‐doped 42.75AlF... more The development and characterization of the optical properties of a neodymium(III)‐doped 42.75AlF3–33.25CaF2–19BaF2–5YF3 (Nd3+‐doped BCA‐5Y) glass in the vacuum ultraviolet (VUV) region are reported. Photoluminescence peaks at 180 and 227 nm are observed upon excitation with the 157 nm emission of a F2 laser. The dominant 180 nm emission peak is assigned to the 4f25d–4f3 (4I9/2 level) transition in Nd3+. This emission peak exhibits a fast, single exponential luminescence with a 16 ns decay time. The strong luminescence intensity and the fast decay time allude to its prospects for scintillator applications.
First-principles density functional calculations together with experimental measurements demonstr... more First-principles density functional calculations together with experimental measurements demonstrate that pressure (uniform and uniaxial) increases the band gap of a perfect lithium hexafluoroaluminate (LiCaAlF6, LiCAF) crystal. As fluoride crystals can be highly transmitting at vacuum ultraviolet wavelengths, crystal modifications that further increase the band gap are highly sought after for future Vacuum ultraviolet applications. Through an extensive series of density functional theory simulations, we demonstrate that the band gap increases monotonically from 12.2 eV to 14.1 eV with the application of uniform pressure. Through joint theoretical and experimental investigation, we explore different uniaxial compressions that can be achieved through cutting-edge laser-shock compression. We find that uniaxial pressure also increases the LiCAF band gap by 0.3 and 0.4 eV for a- and c-axis compressions, respectively.
Conference on Lasers and Electro-Optics 2010, 2010
Experimental results are presented on the properties of a custom-designed fast-response lithium-6... more Experimental results are presented on the properties of a custom-designed fast-response lithium-6 glass scintillator for inertial confinement fusion diagnostics. This newly developed scintillator promises as an indispensable tool in the realization of scattered neutron diagnostics.
International Quantum Electronics Conference, 2005.
It has been known that the surface-field THz emission in a semiconductor and in a semiconductor q... more It has been known that the surface-field THz emission in a semiconductor and in a semiconductor quantum well occurs when a short laser pulse creates electron-hole (e-h) dipoles that are accelerated in opposite directions by the surface electric field. The accelerating charges emit a THz transient signal [1]. Other mechanisms include intersubband spontaneous emissions and the excitation of quantum beats in the quantum well subbands [2]. In these scenarios, it is always surmised that the energy of the excitation laser pulse is higher than the bandgap of the semiconductor for it to be able to create photogenerated e-h pairs. In this work, we present initial results showing surface field THz radiation of a narrow and wide uncoupled GaAs/AlGaAs multiple quantum well (MQW) heterostructures for excitation energies lower than the bandgap. Furthermore, the emission enhancement and suppression effects of an externally applied magnetic field (B-field) are also investigated.
... E. Estacio,' A. Quema.l' G. Diwa,' G. De los Reyes,' H. Murakami,1 S. Ono... more ... E. Estacio,' A. Quema.l' G. Diwa,' G. De los Reyes,' H. Murakami,1 S. Ono,' N. Sarukura,' A. Somintac.? ... The effect ofthe externally applied magnetic field parallel to the MQW plain is to enhance or reduce the THz emission intensity for the up or down direction, respectively. ...
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