| Paper | Title | Page |
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| MOPAB075 | Measurement of Electron Bunch Length via a Tunable-Gap Undulator | 295 |
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| A THz undulator with widely tunable gap is constructed and installed at Tsinghua University beamline, which is applied for narrow-band THz radiation and measurements of electron bunch longitudinal structure. This is a planar electromagnetic device with 8 regular periods, each 10 cm long. The field range B=0.15- 0.99 T peak field on axis while changing the gap from 75mm to 23mm. In the experiments, we scanned the undulator gap to measure the radiation intensity at different resonant frequency, thus we can get the bunch length even form factor of the bunch. The demonstrated experimental results show that the bunch of 220pC compressed by chicane in Tsinghua beamline is about 120fs (rms), which agree well with the simulations. The resolution of bunch length measurement with this method can be attoseconds by optimized undulator. Furthermore, the form factor of electron bunch train can also be measured. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB075 | |
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| MOPAB076 | 2D Beam Profile Monitors at CPHS of Tsinghua University | 298 |
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| Beam profile is a key parameter for high current proton linac. Compact Pulsed Hadron Source(CPHS) has two type of detectors to monitor beam 2D beam profile: scintillator screen and rotatable multi-wire scanner. A retractable chromium-doped alumina (Chromox) screen is used as scintillator, emitted lights when impacted by proton are captured by a 12 bit CCD camera. Nineteen carbon fibre wires with a diameter of 30 'm, 3 mm separated from each other, are used to measure beam 1D distribution. Projection can be measured at different direction by rotating the multi-wire scanner about beam direction. 2D beam distribution is reconstructed from multiple projections with the help of CT. Different CT algorithms, Algebra Reconstruct Technique (ART) and Maximum Entropy algorithm (MENT), are applied to achieve accurate or quick reconstruction. The preliminary experimental results show the two profile monitors working consistently with each other. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB076 | |
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| MOPAB077 | Spatial Decoding Electro-Optic Bunch Measurement at Tsinghua Thomson Scattering X-ray Source | 302 |
| SUSPSIK075 | use link to see paper's listing under its alternate paper code | |
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| Electron bunches with duration of sub-picosecond are essential in ultraviolet and X-ray free electron laser (XFEL) to reach the desired peak current. Electro-optic (EO) technique is suitable for temporal profile measure-ment of these ultrashort bunches which is one of the key diagnostics in FELs. An electro-optic monitor based on spatial sampling has recently been designed and installed for bunch profile diagnostic at Tsinghua Thomson scat-tering X-ray source (TTX). An ultrashort laser pulse is used to detect the field induced birefringence of the bunch Coulomb field in an electro-optic crystal and the monitor allows direct time-resolved single-shot measure-ment of bunch profile with an accuracy of 135 femtosec-onds for a 40 MeV electron bunch in a non-destructive way, which can simultaneously record the relative time jitter between probe laser and electron bunch. This paper performs the layout of the setup and presents the current measurement results. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB077 | |
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| MOPVA027 | Measurement of High Power Terahertz with Dielectric Loaded Waveguide at Tsinghua University | 914 |
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Funding: Work supported by the National Nature Science Foundation of China (NSFC Grants No.11475097) and the National Key Scientific Instrument and Equipment Development Project of China (Grants No. 2013YQ12034504) We have measured an intense THz radiation produced by a sub-picosecond, relativistic electron bunch passing through a dielectric loaded waveguide (DLW) at Tsinghua University accelerator beamline. The DLW was 3 cm long quartz tube with 900 'm inner diameter and 100 'm wall thickness metallized on the outside. Radiated energy of the THz pulse was measured to be proportional to the square of the effective charge. The end of the DLW was cut at an angle for efficient THz pulse extraction. Tens of 'J THz energy per pulse were measured outside the vacuum chamber with a calibrated Golay cell in the experiment. *wangdan16@mail.tsinghua.edu.cn *yanlx@mail.tsinghua.edu.cn |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA027 | |
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| MOPVA031 | Low Energy Compact Storage Ring Design for Compton Gamma-Ray Light Source | 921 |
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| Gamma-ray sources with high flux and spectral densities are highly demanded by many nuclear experiments. We design a low energy compact storage ring to produce gamma-ray with energy in the range of 4-20 MeV based on Compton backscattering technique. The storage ring energy is 500-800 MeV with the circumference of about 59 m and natural emittance of about 3 nmrad at 500 MeV. In this paper, we present the storage ring lattice design and propose two collision configurations for Compton gamma-ray generation. Intrabeam scattering has been investigated which can increase emittance from 3 nmrad to 6 nmrad horizontally for 500 MeV ring. We also discuss how Compton scattering affects longitudinal and transverse beam dynamics by tracking macro particles using our parallel simulation code. Based on this study, we can further optimize our storage ring lattice design for the higher gamma-ray flux production. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA031 | |
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| TUPAB070 | S-Band Accelerating Structure for High-Gradient Upgrade of TTX | 1485 |
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| Thomson scattering x-ray source is an indispensable scientific X-ray imaging tool in various research fields. The 3-meter S-band linac in Tsinghua Thomson scatter-ing X-ray source (TTX) has been running at an accelerat-ing gradient of 15 MV/m so far. The gradient will be upgraded to 30MV/m by replacing the old structure with a shorter linac. Detailed optimization of the RF design of the new S-band linac structure is presented in this paper. Finally, further research on energy upgrade with X-band structures are also discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB070 | |
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| TUPAB071 | Experimental Results on THz Superradiation From the Undulator in Tsinghua University Beamline | 1488 |
| SUSPSIK024 | use link to see paper's listing under its alternate paper code | |
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| In this paper, the first operation of a widely tunable 8-period undulator at terahertz (THz) frequency in Tsinghua University beamline was reported. Superradiate undulator radiation from sub-picosecond electron bunches compressed by chicane was observed. The measured radiation curve shows clearly that the radiation energy is proportional to the charge square, and the THz frequency can be changed from 0.4 THz to 10 THz with narrow-band spectrums. Our results demonstrate a high power and tunable coherent THz source, which could be useful for many applications in the future. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB071 | |
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| TUPAB075 | Compact High Energy Electron Radiography System Based on Permanent Magnet Quadrupole | 1494 |
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| High energy electron radiography(HEER) is a promising diagnostic method for High Energy Density Physics (HEDP) or Inertial Confinement Fusion (ICF) owing to its capability of picosecond-nanometer spatio-temporal resolution, and is cost-effective in the meantime. A Compact HEER (CHEER) system based on Permanent Magnet Quadrupoles (PMQ) instead of conventional electromagnetic quadrupole is proposed. Its lattice design and beam optics optimization is finished, and experiment is to be carried out on Tsinghua Thomson X-ray source (TTX) beamline after PMQs fabrication and installation. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB075 | |
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| TUPAB076 | Design of an X-Band Photocathode for Tsinghua Thomson Scattering X-Ray Source | 1497 |
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| Compared with S-band and C-band accelerating structures, X-band structures can run at a higher accelerating gradient and are more compact in size. In order to obtain higher electron energy in a limited space, a new X-band photo-injector operating at 11.424GHz has been designed at the Accelerator Laboratory of Tsinghua University. The structural design of the X-band photo-cathode RF gun and the accelerating structures as well as the beam dynamics simulation are presented in this paper, followed by the optimization of the structure based on the dispersed optimization experiment method(DOE). The results show that the design satisfies the working requirements with a small space occupied and a high beam quality. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB076 | |
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| WEPVA067 | Preliminary Results on the Resonant Excitation of THz Wakefield in a Multi-Mode Dielectric Loaded Waveguide by Bunch Train | 3426 |
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Funding: Work supported by the National Nature Science Foundation of China (NSFC Grants No.11475097) and the National Key Scientific Instrument and Equipment Development Project of China (Grants No. 2013YQ12034504) We report the preliminary experimental results on the resonant excitation of THz wakefield in a multi-mode dielectric loaded waveguide (DLW) by electron bunch train at the Tsinghua University accelerator beamline. The bunch train with certain longitudinal periodicity was generated based on nonlinear longitudinal space charge oscillation [1]. By passing such bunch train through a multi-mode DLW, we observed selective excitation of the fifth longitudinal mode (TM05 mode) was resonantly excited. Future experiment plan is to tune the bunch train interval with a chicane in the beamline in order to selectively excite arbitrary mode for tunable THz radiation source with multi-mode DLWs. *wangdan16@mail.tsinghua.edu.cn *yanlx@mail.tsinghua.edu.cn |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA067 | |
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| THPVA055 | The Preliminary Performance of the Timing and Synchronization System at Tsinghua University | 4565 |
| SUSPSIK113 | use link to see paper's listing under its alternate paper code | |
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| A precise timing and synchronization system is developed in Tsinghua University(THU). The whole system scheme includes fiber-based CW carrier phase reference distribution system (PRDS) for delivering stabilized RF phase reference to multiple receiver clients, Low Level RF (LLRF) control system to stabilized the accelerating mi-crowave field and laser-RF synchronization system for high precise synchronization of optical and RF signals. The system test and the demonstration experiment of each subsystem are carried on to evaluate the system and the phase error jitter resources are analysed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA055 | |
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