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| MOPAB028 | Estimation of Longitudinal Dimensions of Sub-Picosecond Electron Bunches with the 3-Phase Method | 139 |
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| An estimation of the longitudinal dimensions for short electron bunches in an accelerating field is an important diagnostic and can be extremely helpful in evaluating the performance of an accelerator. We investigate a method for close estimation of bunch length for sub-picosecond electron bunches from the measurement of their energy spreads. Three or more measurements for the bunch energy spread are made by varying the phase of the accelerating structure and later a reconstruction of the bunch longitudinal dimensions, namely bunch length, initial energy spread and chirp at the entrance of the accelerating structure are obtained using the least square method. A comparison of the obtained results with ASTRA simulations is also included to validate the 3-phase method for sub-ps electron bunches. It is a simple method from both understanding (easy reconstruction using transport matrices) and experimental point of views (multiple measurements of energy spread with varying phase of the accelerating structure). | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB028 | |
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| MOPAB048 | Simulation of fs Bunch Length Determination with the 3-Phase Method and THz Dielectric Loaded Waveguides | 199 |
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| In this paper, we investigate with ASTRA simulations the capability of the 3-phase method to reconstruct the length of a fs electron bunch. We show that a standard 3 GHz travelling wave accelerating structure is not suited for this purpose, because of the too important effect of the space-charge forces and of the too small variations of the induced energy spread with the bunch injection phase. Our simulations demonstrate that the use of dielectric-loaded waveguides driven by THz pulses would allow overcoming these two limitations and possibly achieving an ultimate resolution better than 5% for the determination of a 6.25 fs rms bunch length at 100 MeV energy and 1 pC charge. The next steps of the study to better evaluate, in simulations and experiments, the possible sources of degradation of the 3-phase method resolution are also mentioned. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB048 | |
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| MOPAB049 | Development of a Focusing System for the AXSIS Project | 203 |
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| In this paper, we investigate with ASTRA simulations the achievable performances for several focusing systems considered in the AXSIS project. We focus our attention on the requirements in terms of position of the focal point and bunch transverse size at this point. We show that they cannot be fulfilled with a solenoid resistive electro-magnet, but that it is possible when using a solenoid permanent magnet. The use of a quadrupole doublet proves to be adequate to fulfil the requirement on the position of the focal point and be very close to the one on the bunch transverse size, which could possibly be achieved by a further optimization of the parameters of the doublet. Finally, we also investigate the possibility to use an active plasma lens, showing that it could easily fulfil the requirements but that several points must be carefully studied before considering its implementation. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB049 | |
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| MOPAB052 | A Transverse Deflection Structure with Dielectric-Lined Waveguides in the Sub-THz Regime | 215 |
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Longitudinal bunch measurements are typically done with rf-powered transverse deflection structures with operating frequencies 1-12~GHz. We explore the use of mm-scale, THz-driven, dielectric-lined cylindrical waveguides as transverse deflectors by driving the fundamental deflecting mode of the structure, the HEM11. We give a brief overview of the physics, history, and provide an example with a 5~MeV beam using {\sc astra} and {\sc CST-MWS}.
This work was supported by the European Research Council (ERC) under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant agreement no. 609920 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB052 | |
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| MOPIK005 | Compact Electron Injectors Using Laser Driven THz Cavities | 506 |
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| We present ultra-small electron injectors based on cascaded cavities excited by short multi-cycle THz signals. The designed structure is a 3.5 cell normal conducting cavity operating at 300 GHz. This cavity is able to generate pC electron bunches and accelerate them up to 250 keV using less than 1 mJ THz energy. Unlike conventional RF guns, the designed cavity operates in a transient state which, in combination with the high frequency of the driving field, makes it possible to apply accelerating gradients as high as 500 MV/m. Such high accelerating gradients are promising for the generation of high brightness electron beams with transverse emittances in the nm-rad range. The designed cavity can be used as the injector for a compact accelerator of low charge bunches. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK005 | |
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| MOPIK006 | Characterization of the Electron Beam from the Thz Driven Gun for AXSIS | 509 |
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Funding: The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 609920 The AXSIS (Attosecond X-ray Science: Imaging and Spectroscopy) project aims for development of a compact, fully coherent, THz-driven, attosecond X-ray source. A compact THz driven gun was developed, produced and tested as a source of the ultra-short electron bunches required for the project. To characterize the low energy, low-charge beam produced by such a gun tailored diagnostic devices were developed and commissioned at a test-stand chamber in CFEL (DESY). Results of the first experiments on the production and characterization of the electron beam are presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK006 | |
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| MOPVA012 | The Dedicated Accelerator R&D Facility Sinbad at DESY | 869 |
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| We present an overview of the dedicated R\&D facility SINBAD which is currently under construction at DESY. The facility will host multiple independent experiments on the acceleration of ultra-short electron bunches and advanced acceleration schemes. In its initial phase, SINBAD will host two experiments: AXSIS and ARES. The AXSIS collaboration aims to accelerate fs-electron bunches to 15 MeV in a THz driven dielectric structure and subsequently create X-rays by inverse Compton scattering. The first stage of the ARES experiment is to set up a 100 MeV S-band electron linac to produce ultra-short electron bunches with excellent beam arrival time stability. Once this is achieved, the electrons will be ideally suited to be injected into experiments for testing advanced accelerator concepts e.g. DLA experiments in the context of the ACHIP collaboration. In the long term, external injection into a laser driven plasma acceleration stage is targeted as well. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA012 | |
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| TUPAB025 | Experimental Results for Multiphoton Nonlinear Photoemission Processes on Phil Test Line | 1369 |
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One of the prerequisites for the next generation high luminosity light sources is the availability of the short electron bunches. It also has several applications in other domains, including medical diagnostics and high-resolution imaging. In principle, using photoelectric effect a short electron bunch can initially be generated by illuminating a photocathode with an ultra-short light pulse of appropriate wavelength. Strong EM fields from a RF gun or similar accelerating structures, synchronized with the incoming laser pulses, are then used to accelerate these electron bunches initially up to an energy of tens of MeV. We present our preliminary results on the experimental investigation of two-photon nonlinear photoemission processes for the generation of picosecond, low-charge electron bunches conducted at PHIL photoinjector facility. A comparison of the emission efficiency and bunch characteristics with the single photon emission process is also made.
*PHIL is an acronym for Photo-injector at Linear Accelerator Laboratory (LAL). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB025 | |
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| TUPAB038 | Electron Acceleration With a Ultrafast Gun Driven by Single-Cycle Terahertz Pulses | 1406 |
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Funding: This work was supported by the European Research Council under the European Union Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no. 609920. We present results on an improved THz-driven electron gun using transversely-incident single-cycle THz pulses using a horn-coupler. Intrinsic synchronization between the electrons and the driving field was achieved by using a single laser system to create electrons by UV photoemission and to create THz radiation by difference frequency generation in a tilted-pulse front geometry. Details of the optical setups for the UV and THz pulses will be described as well as preliminary results showing evidence of electron acceleration. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB038 | |
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| WEPVA008 | Beam Dynamics in THz Dielectric Loaded Waveguides for the AXSIS Project | 3268 |
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| In this paper, we investigate with ASTRA simulations the beam dynamics in dielectric-loaded waveguides driven by THz pulses, used as linac structure for the AXSIS project. We show that the bunch properties at the linac exit are very sensitive to the phase velocity of the THz pulse and are limited by the strong phase slippage of the bunch respective to it. We also show that some margins for instabilities of the injection phase into the linac structure are allowed. We finally demonstrate that the bunch properties are optimized when low frequencies (< 300 GHz) are used inside the linac, and that the longitudinal focal point can be put several tens of cm away from the linac exit thanks to ballistic bunching. However, a strong asymmetry in the bunch transverse sizes remains for which a solution is still to be found. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA008 | |
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