PubIic reporting burden for this collection of information is estimated to average 1 hour per res... more PubIic reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of Informakrn, including suggestions for reducing 'ids burden to Department of Defense, Washington Heaedquarters Services, Directorate for Information Operations and Reports (0704-0188). 1215 Jefferson Davi Highway, Suite 1204, Arlngton, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a colleclion 0o Intormalfon if it does not display a currently valid 0M8 control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
This paper presents overviews of a number of processes and applications associated with high-powe... more This paper presents overviews of a number of processes and applications associated with high-power, high-intensity lasers, and their interactions. These processes and applications include: free electron lasers, backward Raman amplification, atmospheric propagation of laser pulses, laser driven acceleration, atmospheric lasing, and remote detection of radioactivity. The interrelated physical mechanisms in the various processes are discussed.
Laser-driven accelerators require guiding of the laser pulse over many Rayleigh lengths. Plasma c... more Laser-driven accelerators require guiding of the laser pulse over many Rayleigh lengths. Plasma channels such as those produced by a capillary discharge have been shown experimentally to be capable of guiding intense laser pulses over distances as long as 6 cm. Simulations of laser propagation in these channels show that the laser pulse radius undergoes oscillations about the matched radius at the expected frequency. The pulse may be distorted by several effects, including laser-generated ionization. Experiments to date have been at relatively high densities (1018-1019 cm-3). For standard laser wakefield accelerator applications, the channel density is likely to be substantially lower. As expected, simulations in this lower density regime show lower accelerating gradients, larger laser spot sizes, and higher wakefield phase velocities and dephasing-limited energy gain
This paper presents a new concept for the remote detection of radioactive materials. The concept ... more This paper presents a new concept for the remote detection of radioactive materials. The concept is based on the detection of electromagnetic signatures in the vicinity of radioactive material and can enable stand-off detection at distances greater than 100 m. Radioactive materials emit gamma rays, which ionize the surrounding air. The ionized electrons rapidly attach to oxygen molecules forming O2− ions. The density of O2− around radioactive material can be several orders of magnitude greater than background levels. The elevated population of O2− extends several meters around the radioactive material. Electrons are easily photo-detached from O2− ions by laser radiation. The photo-detached electrons, in the presence of laser radiation, initiate avalanche ionization which results in a rapid increase in electron density. The rise in electron density induces a frequency modulation on a probe beam, which becomes a direct spectral signature for the presence of radioactive material.
PubIic reporting burden for this collection of information is estimated to average 1 hour per res... more PubIic reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of Informakrn, including suggestions for reducing 'ids burden to Department of Defense, Washington Heaedquarters Services, Directorate for Information Operations and Reports (0704-0188). 1215 Jefferson Davi Highway, Suite 1204, Arlngton, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a colleclion 0o Intormalfon if it does not display a currently valid 0M8 control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
This paper presents overviews of a number of processes and applications associated with high-powe... more This paper presents overviews of a number of processes and applications associated with high-power, high-intensity lasers, and their interactions. These processes and applications include: free electron lasers, backward Raman amplification, atmospheric propagation of laser pulses, laser driven acceleration, atmospheric lasing, and remote detection of radioactivity. The interrelated physical mechanisms in the various processes are discussed.
Laser-driven accelerators require guiding of the laser pulse over many Rayleigh lengths. Plasma c... more Laser-driven accelerators require guiding of the laser pulse over many Rayleigh lengths. Plasma channels such as those produced by a capillary discharge have been shown experimentally to be capable of guiding intense laser pulses over distances as long as 6 cm. Simulations of laser propagation in these channels show that the laser pulse radius undergoes oscillations about the matched radius at the expected frequency. The pulse may be distorted by several effects, including laser-generated ionization. Experiments to date have been at relatively high densities (1018-1019 cm-3). For standard laser wakefield accelerator applications, the channel density is likely to be substantially lower. As expected, simulations in this lower density regime show lower accelerating gradients, larger laser spot sizes, and higher wakefield phase velocities and dephasing-limited energy gain
This paper presents a new concept for the remote detection of radioactive materials. The concept ... more This paper presents a new concept for the remote detection of radioactive materials. The concept is based on the detection of electromagnetic signatures in the vicinity of radioactive material and can enable stand-off detection at distances greater than 100 m. Radioactive materials emit gamma rays, which ionize the surrounding air. The ionized electrons rapidly attach to oxygen molecules forming O2− ions. The density of O2− around radioactive material can be several orders of magnitude greater than background levels. The elevated population of O2− extends several meters around the radioactive material. Electrons are easily photo-detached from O2− ions by laser radiation. The photo-detached electrons, in the presence of laser radiation, initiate avalanche ionization which results in a rapid increase in electron density. The rise in electron density induces a frequency modulation on a probe beam, which becomes a direct spectral signature for the presence of radioactive material.
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Papers by Bahman Hafizi