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| MOPTS052 | Simulation of Electric and Thermal Behavior of Cryogenic Three-cell Copper Accelerating Cavity for High Gradient Experiments | 980 |
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| A C-band three-cell pi-mode accelerating cavity made of high purity copper is under design for use in ultra-high accelerating gradient experiments at a cavity temperature of 20 K. The basic configuration, consisting of mode converter, short circular waveguide and cells with round periphery, is the same as that which was previously employed in the cold model for a 2.6-cell photocathode electron gun cavity. Though the 0.6-cell part in the previous model is replaced with a full cell having a beam duct, the overall electric property of the cavity will not change significantly. The RF input coupling coefficient is adjusted to around 10 at 20 K, which is expected to be lowered significantly due to the increase in the surface resistance by the rapid temperature rise during a high power RF input. The results of the simulations on the electric field and the temperature rise along the cavity surface during the RF pulse are discussed in the report. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS052 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019 | |
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| TUPRB039 | Research of Coherent Edge Radiation Generated by Electron Beams Oscillating Free-Electron Lasers | 1772 |
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Funding: JSPS KAKENHI Grant Number JP16H03912 We have studied far-infrared coherent radiation with an S-band linac at Laboratory for Electron Beam Research and Application (LEBRA) at Nihon University. We have already developed a couple of terahertz-wave sources based on coherent synchrotron radiation and coherent transition radiation*, which have been applied to spectroscopic research**. Moreover, we developed coherent edge radiation (CER) at the downstream bending magnets in the FEL sections. Because the edge radiation has an annular shape distribution characterized by the asymmetric first-order Laguerre-Gaussian mode, the CER can be extracted from an optical cavity of the FEL system without a diffraction loss of the FEL beam***. The root-mean-squared bunch length of the electron beam was evaulated by measuring the CER spectra, which was about the same level as the FEL micropulse width. Although the infrared FELs at LEBRA had a long slippage length, the CER intensity can be a guidepost enhancing the FEL power because of the existence of their correlation. In this presentation, the characteristics of the CER including correlation between the CER and the FEL will be reported. * N. Sei et al., Jpn. J. Appl. Phys. 56, (2017) 032401. ** N. Sei et al., J. Opt. Soc. Am. B, 31, (2014) 2150. *** N. Sei et al., Phys. Lett. A in press. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB039 | |
| About • | paper received ※ 19 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| TUPRB040 | Development of Coherent Terahertz Wave Sources and Transport Systems at LEBRA Linac | 1775 |
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Funding: This work was supported by JSPS KAKENHI (Grant-in-Aid for Young Scientists (B)) Grant Number JP16K17539 and JP16H03912. Development of a 125 MeV S-band electron linac for the generation of Free Electron Laser (FEL), Parametric X-ray Radiation (PXR) and coherent terahertz waves (THz waves) has been underway at LEBRA of Nihon University as a joint research with KEK and National Institute of Advanced Industrial Science and Technology (AIST). The high power coherent transition radiation (CTR), coherent edge radiation (CER) and the coherent synchrotron radiation (CSR) wave sources development has been carried out since 2011 at LEBRA. The transport systems of the each THz wave were installed in the vacuum chamber on the downstream side of the 45 degrees bending magnet of the PXR and FEL beam-line. In particular, a CER of the generated the FEL beam line can also be guided without disturbing the FEL oscillations. Additionally, a part of the mirror of the transport optical system is constructed using Indium Tin Oxide (ITO) mirror with the optimized for the transport of the THz wave. In this report, construction of the THz transport beam lines and the property of the THz lights are discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB040 | |
| About • | paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| TUPRB041 | Simulation of Short-Pulse Generation from a Dynamically Detuned IR-FEL Oscillator and Pulse Stacking at an External Cavity | 1778 |
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Funding: Q-LEAP program supported by Ministry of Education, Culture, Sports, Science and Technology, Japan At the LEBRA facility of Nihon U., we have an IR-FEL oscillator to generate radiations in the range of wavelengths 1-6 um for various experiments. A research program has been established to explore the application of the IR-FEL to generate attosecond UV and X-ray pulses through the high harmonic generation (HHG) in noble gases, where the IR-FEL pulses must have a high-peak power and a short-pulse duration. The property of generated FEL pulse is affected by the cavity length detuning of FEL oscillator as well as the small signal gain and the cavity loss. The operation at a small- or zero-detuning length is necessary to generate a FEL pulse shorter than the bunch length, although it requires a long macro-pulse to reach the saturation. For the short FEL pulse generation within a limited macro-pulse length at the LEBRA LINAC, we apply a dynamical modulation to the electron bunch repetition, that is equivalent to a dynamical detuning of the FEL cavity length. We illustrate the potential performance of the IR-FEL with the dynamical detuning by time-dependent 3D FEL simulations. We also evaluate the enhancement of the FEL pulses by an external cavity stacking for the sake of the HHG application. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB041 | |
| About • | paper received ※ 29 April 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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