2011 Particle Accelerator Conference - List of Authors (Jia, B.)

Paper	Title	Page
THP152	Calibration of Spectrometers with Undulator Radiation	2402
	S. Huang PKU/IHIP, Beijing, People's Republic of China B. Jia, J.Y. Li, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the U.S. Department of Energy, Office of Nuclear Physics under grant number DE-FG02-97ER41033 A well-calibrated spectrometer is critical for measuring the real spectra of spontaneous radiation of an electron beam in undulators (i.e. undulator radiation), which is important for FEL research. A calibration method of spectrometers based upon the known undulator radiation spectrum has been developed at Duke FEL Laboratory (DFELL). It has been used to provide a precise calibration for spectrometers from infrared (IR) to ultraviolet (UV). This calibration method is expected to be useful for the calibration of spectrometers working in the extreme ultraviolet (EUV) and X-ray region. In this work, we present the details of the calibration method and illustrate the usefulness of the method using a portable spectrometer in the visible region as an example.

THP153	Manipulating the FEL gain process with an In-cavity Aperture System	2405
	J.Y. Li, B. Jia, S.F. Mikhailov, V. Popov, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA S. Huang PKU/IHIP, Beijing, People's Republic of China
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. The 53.73 meters long free-electron laser (FEL) resonator at Duke University consists of two concave mirrors with the similar radius of curvature. The downstream mirror receives not only the fundamental but also higher order harmonic radiation (typically in the UV and VUV range) emitted by relativistic electrons in the magnetic field of wigglers. The power load of wiggler radiation on this mirror can thermally deform and permanently damage the multi-layer coating of the mirror, therefore, limiting the maximum power of the FEL operation and reducing the mirror lifetime. To mitigate these problems, a water-cooled aperture system has been installed inside the FEL resonator. This aperture system has been used to prevent most of off-axis helical wiggler radiation from reaching the downstream FEL mirror. It has also been used to manipulate the FEL gain process by increasing the FEL beam diffraction loss inside the resonator. In principle, this aperture system can be used as an independent FEL gain control device for FEL operation. This paper reports our preliminary study of the FEL operation using the in-cavity apertures to manipulate the FEL gain process.

Paper

Title

Page

Calibration of Spectrometers with Undulator Radiation

2402

S. Huang
PKU/IHIP, Beijing, People's Republic of China
B. Jia, J.Y. Li, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the U.S. Department of Energy, Office of Nuclear Physics under grant number DE-FG02-97ER41033
A well-calibrated spectrometer is critical for measuring the real spectra of spontaneous radiation of an electron beam in undulators (i.e. undulator radiation), which is important for FEL research. A calibration method of spectrometers based upon the known undulator radiation spectrum has been developed at Duke FEL Laboratory (DFELL). It has been used to provide a precise calibration for spectrometers from infrared (IR) to ultraviolet (UV). This calibration method is expected to be useful for the calibration of spectrometers working in the extreme ultraviolet (EUV) and X-ray region. In this work, we present the details of the calibration method and illustrate the usefulness of the method using a portable spectrometer in the visible region as an example.

THP153

Manipulating the FEL gain process with an In-cavity Aperture System

2405

J.Y. Li, B. Jia, S.F. Mikhailov, V. Popov, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA
S. Huang
PKU/IHIP, Beijing, People's Republic of China

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
The 53.73 meters long free-electron laser (FEL) resonator at Duke University consists of two concave mirrors with the similar radius of curvature. The downstream mirror receives not only the fundamental but also higher order harmonic radiation (typically in the UV and VUV range) emitted by relativistic electrons in the magnetic field of wigglers. The power load of wiggler radiation on this mirror can thermally deform and permanently damage the multi-layer coating of the mirror, therefore, limiting the maximum power of the FEL operation and reducing the mirror lifetime. To mitigate these problems, a water-cooled aperture system has been installed inside the FEL resonator. This aperture system has been used to prevent most of off-axis helical wiggler radiation from reaching the downstream FEL mirror. It has also been used to manipulate the FEL gain process by increasing the FEL beam diffraction loss inside the resonator. In principle, this aperture system can be used as an independent FEL gain control device for FEL operation. This paper reports our preliminary study of the FEL operation using the in-cavity apertures to manipulate the FEL gain process.