| Paper | Title | Page |
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| WPAP003 | Emission Mechanisms in a Photocathode RF Gun | 856 |
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| In photocathode rf guns, emission mechanisms at the photocathode play a crucial role in the overall beam dynamics. A low bunch charge as well as a short Gaussian bunch profile allow us to study the beam dynamics depending on emission phase without space charge force. This paper presents experimental and simulation studies toward detailed understanding of the photo emission and secondary emission processes at the cathode. | ||
| WPAP004 | Dark Current and Multipacting in the Photocathode RF Guns at PITZ | 895 |
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| For photocathode rf guns, the amount of dark current depends on the cavity surface and the photocathodes. Smooth conditioning reduces the amount of dark current. Mechanical damages of the cathodes induce high dark current and chemical pollution changes emission properties of the cathode. Multipacting in the gun cavity changes the surface status of the cathodes and sometimes makes the gun operation impossible due to vacuum interlocks. In this paper, dark current and multipacting features of the rf gun are presented including experimental and simulation studies. | ||
| WPAP006 | Recent Developments at PITZ | 1012 |
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| The ability to produce high brightness electron beams as required for modern Free Electron Lasers (FELs) has been demonstrated during the first stage of the Photo Injector Test Facility at DESY Zeuthen (PITZ1). The electron source optimization at PITZ1 was successfully completed, resulting in the installation of the PITZ rf gun at the VUV-FEL (DESY, Hamburg). One of the main goals of the second stage of PITZ (PITZ2) is to apply higher gradients in the rf gun cavity in order to obtain smaller beam emittance by faster acceleration of the space charge dominated beams. In order to reach the required gradients a 10 MW klystron has to be installed and the gun cavity has to be conditioned for higher peak power. Another important goal of PITZ2 is a detailed study of the emittance conservation principle by using proper electron beam acceleration with a booster. Further photo injector optimization, including update of the photocathode laser and diagnostic tools, is foreseen as well. Recent progress on the PITZ developments will be reported. | ||
| WPAT083 | Steering and Focusing Effects in TESLA Cavity Due to High Order Mode and Input Couplers | 4135 |
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Funding: This work was supported by Universities Research Association Inc. under contract DE-AC02-76CH00300 with the U.S. Department of Energy, and by NICADD. Many state-of-art electron accelerator proposals incorporate TESLA-type superconducting standing wave cavities. These cavities include input coupler (to feed the RF power into the cavity) and a pairs of high order mode couplers (HOM) to absorb the energy associated to HOM field excited as the bunch passes through the cavity. In the present paper we investigate, using numerical simulations, the impact of the input and HOM couplers on the beam dynamics. We show the overall effects are: a dipole kick (zeroth order) and normal and skew quadrupole-type focusing (first order). We present parametric studies of the strength of these effect for various operating gradients and incoming beam energies. We finally study the impact of this non-asymmetric field on the beam dynamics, taking as an example the low energy section of the European X-FEL injector. |
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| RPPP006 | The PITZ Booster Cavity–A Prototype for the ILC Positron Injector Cavities | 1030 |
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| A critical issue of the design of the Positron Pre-Accelerator (PPA) for the future International Linear Collider (ILC) is the operational reliability of the normal conducting, high accelerating gradient L-band cavities. Now a booster cavity, intended for increasing the beam energy at the Photo Injector Test Facility in Zeuthen (PITZ), and developed by a joined INR-DESY group, is under construction at DESY, Hamburg. With the PITZ requirements (accelerating gradient up to 14 MV/m, rf pulse length up to 900 mks, repetition rate up to 5 Hz) this cavity, which is based on the Cut Disk Structure (CDS), is a full scale, high rf power prototype of the cavities proposed for the PPA. The booster cavity operation will allow us to confirm the main design ideas for the high gradient PPA cavities. A detailed technical study was performed during the booster cavity design, resulting in some modifications for the PPA cavities, which are described in this paper. We also propose a program of rf experiments with the PITZ booster cavity for further improvements of the PPA structures. | ||
| RPPT011 | Optimized Bunch Compression System for the European XFEL | 1236 |
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| The European XFEL bunch compressor system has been optimized for greater flexibility in parameter space. Operation beyond the XFEL design parameters is discussed in two directions: achieving the uppermost number of photons in a single pulse on one hand and reaching the necessary peak current for lasing with a pulse as short as possible on the other. Results of start-to-end calculations including 3D-CSR effects, space charge forces and the impact on wake fields demonstrate the potential of the XFEL for further improvement or, respectively, its safety margin for operation at design values. |