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| MOPPH027 |
Status of the KAERI THz FEL for the Application on Security Inspection
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- P. Ahn, H. J. Cha, B. C. Lee, J. Mun, S. H. Park, Y. U. Jeong
KAERI, Daejon
- G. M. Kazakevich
Fermilab, Batavia, Illinois
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Terahertz (THz) technology has been considered as a new tool for security inspection due to its safe energy range to human irradiation, foot-print spectral characteristics for most chemicals and bio-materials, and relatively high spatial resolution for imaging. One of the main tasks in the THz inspection technology is to develop a high power and compact source to realize a real-time imaging. We have developed a compact terahertz (THz) free electron laser (FEL). The FEL operates in the wavelength range of 100–1200 micrometers, which corresponds to 0.3–3 THz. THz radiation from the FEL shows much higher power of 100 W when compared to the power level, < 100 mW, of the table-top sources by conventional lasers. The THz FEL beam shows a good performance in pulse-energy stability, polarization, spectrum and spatial distribution. We report the experimental studies of the transmission and reflection-type scanning imaging of baggage and a window dummy. The required power level of the THz sources is estimated for the practical applications of the inspection imaging.
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| MOPPH039 |
Sideband Instability in a Compact THz Free-Electron Laser at KAERI
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- P. Ahn, H. J. Cha, B. C. Lee, J. Mun, S. H. Park, Y. U. Jeong
KAERI, Daejon
- G. M. Kazakevich
Fermilab, Batavia, Illinois
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Frequency offset of a Sideband instability has been observed in a compact waveguide-mode terahertz (THz) free-electron laser (FEL). The spectra of the FEL pulses were measured by a Fabry-Perot spectrometer having a resolution of 10(-4) of the central wavelength at a 2-3 THz range. The shift of the sideband was measured to be 0.5-1.2 micrometers depending on the FEL wavelength from 110 to 165 micrometers. An increase of the sideband shift for a longer wavelength can be explained by the change of the wave’s group velocity in a plane-parallel waveguide. Mode competition between the sidebands and primary wave was observed by changing the cavity length of the FEL. We could decrease the number of the modes and reduce the linewidth of the spectra by controlling the cavity detuning. We have discussed the complexity of the sideband instability depending on the FEL wavelengths and its gain characteristics.
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| TUPPH015 |
Diffraction Effects in the Coherent Transition Radiation Bunch Length Diagnostics
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- V. A. Lebedev, S. Nagaitsev, G. M. Kazakevich
Fermilab, Batavia, Illinois
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Diffraction effects in the Coherent Transition Radiation (CTR) bunch length diagnostics were considered for the A0 Photoinjector and the ILC injection module. The effects can cause a noticeable distortion of the measured CTR spectra dependently on the experimental setup and the bunch parameters. The distortion results in the the errors of the bunch length determination. Presented calculations show possible errors in determination of the bunch length in assumed experiments based on the CTR spectra measurements at A0 Photo injector and the ILC injection module.
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