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- Title
- Output power stabilization of collimated, solid-state laser emissions as applied to high accuracy attenuance measurements.
- Creator
- Caimi, F. M., Tusting, Robert F., Kennedy, G., Harbor Branch Oceanographic Institute
- Date Issued
- 1984
- PURL
- http://purl.flvc.org/fcla/dt/3180377
- Subject Headings
- Lasers, Lasers and optical engineering
- Format
- Document (PDF)
- Title
- Spectroscopic studies of ZnWO4 and doped ZnWO4 single crystals.
- Creator
- Wang, Hong, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Zinc tungstate (ZnWO4) is promising as a scintillator and laser host material. However, the presence of color centers limit its applications. It has been found that special annealing techniques or doping with metallic elements such as Nb or Sb can bleach the samples (Zhou et al. 1986a, 1986b, 1989). A group-theoretical analysis of the characteristic lattice vibrational modes for ZnWO4 single crystals is given. The mode assignments have been made. The temperature dependence of the Raman...
Show moreZinc tungstate (ZnWO4) is promising as a scintillator and laser host material. However, the presence of color centers limit its applications. It has been found that special annealing techniques or doping with metallic elements such as Nb or Sb can bleach the samples (Zhou et al. 1986a, 1986b, 1989). A group-theoretical analysis of the characteristic lattice vibrational modes for ZnWO4 single crystals is given. The mode assignments have been made. The temperature dependence of the Raman spectra has been obtained experimentally in various polarization geometries. Anharmonic contributions and interactions between phonons are discussed. Photoluminescence studies of ZnWO4 (colored, color-free), ZnWO4: Nb and ZnWO4:Sb have been carried out in the temperature range from 11 to 430 K. All samples show the blue emission band. An IR emission band with a zero-phonon line (ZPL) has been found in ZnWO4 colored samples only. The lineshape function of the emission bands has been theoretically studied and compared with the experimental results. Radiative, non-radiative and multiphonon transitions have been investigated in the thermal quenching model. The temperature dependences of the intensity, the frequency and the linewidth of the ZPL have been studied. Using the Single Configurational Coordinate model, the linear coupling between electrons and phonons has been analyzed. The quadratic coupling of electrons and phonons has been studied in the Debye approximation. The coupling of electronic transitions to normal vibrational modes, pseudo-localized vibrational modes and localized modes is also discussed.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/12346
- Subject Headings
- Physics, Condensed Matter, Physics, Optics, Engineering, Materials Science
- Format
- Document (PDF)
- Title
- The Advantages of Collimator Optimization for Intensity Modulated Radiation Therapy.
- Creator
- Doozan, Brian, Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
The goal of this study was to improve dosimetry for pelvic, lung, head and neck, and other cancers sites with aspherical planning target volumes (PTV) using a new algorithm for collimator optimization for intensity modulated radiation therapy (IMRT) that minimizes the x-jaw gap (CAX) and the area of the jaws (CAA) for each treatment field. A retroactive study on the effects of collimator optimization of 20 patients was performed by comparing metric results for new collimator optimization...
Show moreThe goal of this study was to improve dosimetry for pelvic, lung, head and neck, and other cancers sites with aspherical planning target volumes (PTV) using a new algorithm for collimator optimization for intensity modulated radiation therapy (IMRT) that minimizes the x-jaw gap (CAX) and the area of the jaws (CAA) for each treatment field. A retroactive study on the effects of collimator optimization of 20 patients was performed by comparing metric results for new collimator optimization techniques in Eclipse version 11.0. Keeping all other parameters equal, multiple plans are created using four collimator techniques: CA0, all fields have collimators set to 0°, CAE, using the Eclipse collimator optimization, CAA, minimizing the area of the jaws around the PTV, and CAX, minimizing the x-jaw gap. The minimum area and the minimum x-jaw angles are found by evaluating each field beam’s eye view of the PTV with ImageJ and finding the desired parameters with a custom script. The evaluation of the plans included the monitor units (MU), the maximum dose of the plan, the maximum dose to organs at risk (OAR), the conformity index (CI) and the number of fields that are calculated to split. Compared to the CA0 plans, the monitor units decreased on average by 6% for the CAX method with a p-value of 0.01 from an ANOVA test. The average maximum dose remained within 1.1% difference between all four methods with the lowest given by CAX. The maximum dose to the most at risk organ was best spared by the CAA method, which decreased by 0.62% compared to the CA0. Minimizing the x-jaws significantly reduced the number of split fields from 61 to 37. In every metric tested the CAX optimization produced comparable or superior results compared to the other three techniques. For aspherical PTVs, CAX on average reduced the number of split fields, lowered the maximum dose, minimized the dose to the surrounding OAR, and decreased the monitor units. This is achieved while maintaining the same control of the PTV.
Show less - Date Issued
- 2017
- PURL
- http://purl.flvc.org/fau/fd/FA00004804, http://purl.flvc.org/fau/fd/FA00004804
- Subject Headings
- Radiation--Dosage., Optical engineering., Medical physics., Image-guided radiation therapy., Cancer--Radiotherapy., Medical radiology--Data processing., Medicine--Mathematical models.
- Format
- Document (PDF)
