| Paper | Title | Page |
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| THPOW001 | Design of a 4.6-Cell RF Gun for the PHIL accelerator at LAL | 3922 |
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| A photo-injector with 4.6-cell and resonate frequency of 2.998 GHz has been designed and studied to replace the 2.5-cell RF gun + booster association. The cavity iris shape and dimensions were simulated systematically to optimize the shunt impedance. In this study, electron beam reaches to 9.7 MeV with a moderate peak accelerat-ing gradient of 80 MV/m. Considering a beam charge of 1 nC/bunch, average transverse emittance of ~ 5.9 πmm mrad and energy spread of ~ 0.8% can be obtained at the exit of the gun. The RF input power is only 10.2 MW due to the high shunt impedance. Asymmetry of the electric field due to the coupling port has also been studied using 3D codes for RF and beam dynamics calculations. We will present the RF design and beam calculations results. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW001 | |
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| THPOW002 | Electromagnetic, Thermal, and Structural Analysis of a THOMX RF Gun Using ANSYS | 3925 |
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| Photocathode RF guns are used in the first stage of electron beam generation and acceleration. The RF gun of THOMX is a 2.5 cell standing wave copper cavity with resonance frequency of 2998.55 MHz at 30 °C under vacuum. The metal photocathode such as copper or magnesium is inserted into the backplane of the cavity. Due to high repetition rates up to 50 Hz with the average dissipated power into the internal surfaces up to 1.5 kW, causing a heating and deformation of the cavity shape. Therefore, the cooling system of the device has to be well designed to take under control the deformations of the structure, providing a temperature increase as small and uniform as possible. For this purpose a fully coupled electromagnetic-thermal-structural finite element analysis on this gun has been performed with Ansys workbench. Numerical results show that the gun could operate at 3 μs RF pulse length and 50 Hz repetition rate with an average dissipated power of 1.5 kW. The gun average temperature is around 30 °C while the incoming water temperature is around 24°C. Internal speed of water is 2.5 m/s which corresponds to 15 l/min for the incoming water. The total pressure drop is around 0.4 bar | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW002 | |
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| THPOW003 | Highlights on Metallic Photocathodes Used in SRF Gun | 3928 |
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For the accelerator-based light sources and the electron colliders, the development of photoinjectors has become a key technology. Especially for the superconducting radio frequency cavity based injector (SRF Gun), the searching for better photocathodes is always a principal technical challenge. To use metallic photocathodes for ELBE SRF Gun is the primary choice to prevent cavity contamination. In this contribution, we will report the investigation of Magnesium (Mg) in ELBE SRF gun, including laser cleaning treatment and the measurement on quantum efficiency, Schottky effect, dark current and damage threshold.
The work is supported by the European Community under the FP7 programme (EuCARD-2 and LA3NET) and by the German Federal Ministry of Education and Research (BMBF) grant 05K12CR1. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW003 | |
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| THPOW004 | Pulse Response Measurements of NEA Photocathodes at Different Laser Wavelengths | 3931 |
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| For high average electron beam currents the length of the electron bunches must match the acceptance of the accelerator. At Johannes Gutenberg-University Mainz we are able to measure the longitudinal pulse response of NEA photocathodes (GaAs) under photo excitation of different wavelengths. A time resolution of < 2 ps at a beam energy of 100 keV is achieved, furthermore, a high dynamic range allows to investigate long ranging tails of the response (longitudinal halo). This serves to identify the best possible operation mode for high current photo sources. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW004 | |
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| THPOW005 | A Study of CsK2Sb Multi-alkali Photocathode by Ultraviolet Photoelectron Spectroscopy at UVSOR | 3934 |
| SUPSS022 | use link to see paper's listing under its alternate paper code | |
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| Photocathode is one of the most important components in the next-generation accelerators, especially based on linear accelerators. Photocathode performance depends not only on electronic state in its bulk material but also on the surface condition. CsK2Sb multi-alkali photocathode is a candidate for the high brightness electron source because of its high quantum efficiency by green laser and its high robustness. We have carried out an UPS (UV Photoelectron Spectroscopy) experiment at UVSOR facility, synchrotron radiation light source in Aichi Japan. We have compared the UPS spectra among several samples, each one has a different quantum efficiency, and try to find physics which decide photocathode's performance. In this case, we focused some characters correlated to the quantum efficiency. I'm going to present a result of this analysis. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW005 | |
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| THPOW006 | A Study of Operational Lifetime of CsK2Sb Photo-cathode | 3938 |
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| A high performance electron beam generated with a laser photo-cathode is one of the most important pieces in the advanced accelerator. Because the CsK2Sb photo-cathode is robust with more than 10 % quantum efficiency (QE) by green laser (532nm), it is considered to be the best candidates of the cathode for Energy Recovery Lin-ac (ERL) and Free Electron Laser (FEL) requiring a high brightness beam. We developed a system to evaporate the cathode as a thin film in vacuum to study the cathode performance. The cathode operational lifetime regarding not only on time, but also extracted charge density was studied. We found the lifetime is long enough for practical use in an accelerator. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW006 | |
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| THPOW007 | Cs2Te Photocathode Response Time Measurements and Femtosecond Comb Electron Beam Generation as a Milestone Towards Pre-Bunched Thz Fel Realization | 3941 |
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Funding: Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan and JSPS KAKENHI: 23226020 and 24654076 Currently there is a rapidly growing demand to increase the brightness of electron beams generated by conventional RF guns as well as to decrease the cost of the injector accelerator system for many research facilities worldwide. To address this demand we investigate one of the most important parameter of the high Q.E. conventional semiconductor Cs2Te photocathode, its response time. It sets the principle limitation for generated bunch length and hence maximum achievable beam brightness of electron diffraction and pre-bunched THz FEL facility's injectors. The experimental investigation was done at KEK: LUCX facility. The Cs2Te photocathode response time better than 250 fs was demonstrated. The generation of 4 micro-bunch comb electron beam with variable time separation as a crucial technology for pre-bunched THz FEL realization was achieved. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW007 | |
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| THPOW008 | DC Photoemission Gun Upgrade at the Compact ERL | 3944 |
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Funding: This work is partially supported by a JSPS Grant-in-Aid for Scientific Research in Japan (15H03594). The DC photoemission gun at the compact ERL (cERL) has stably provided beam for ERL commissioning and laser Compton scattering experiments since April 2013. The operational voltage has however been limited to 390 kV due to failures of two segments out of the ten segmented insulator. In order to recover 500 kV operation, we installed an additional two segmented insulator on the existing ten segmented insulator during summer shutdown in 2015. The details of the gun upgrade and the operational experience of the upgraded cERL gun will be presented. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW008 | |
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| THPOW009 | Optimal Design of a Photocathode Electron Gun with High-brightness and High-repetition Rate Based on Genetic Algorithm | 3947 |
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| A low RF frequency of normal conducting photocathode gun with high-brightness and high-repetition rate is designed as an electron source of the Next Generation Light Source (NGLS). In order to optimize the performance of the gun, a genetic multi-objective algorithm has been used. A genetic algorithm is used because of the inherent complexity of the large number of parameters of the cavity geometry available for optimization. On the other hand, the multiplicity of requirements on the beam, which include beam emittance, beam pulse length, energy chirp, as well as pulse shape and peak current, leads to a multi-objective approach for the optimization technique. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PERMELA particle-in-cell code. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW009 | |
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| THPOW010 | Study on Characteristics of Asymmetric Centre Iris of Photocathode Microwave Electron Gun | 3951 |
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| The characteristics of asymmetric iris between first cell and second cell of 1.6 cell photocathode gun are studied. For π-mode, the RF radial field of two sides of the iris is non anti-symmetric. Thus, the RF transverse force at the iris is not negligible. In this paper, we present the status of the optimization simulations, using the SUPERFISH and PARMELA particle-in-cell code. Numerical results of beam dynamics show that it can improve the emittance at the exit of the gun. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW010 | |
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| THPOW011 | The Measurement System of the Electron Gun with Double-anode Structure | 3954 |
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Funding: National Natural Science Foundation of China(11175181); National Natural Science Foundation of China(10875116) The double-anode structure with an intermediate electrode has been proposed to overcome the strong space-charge force on the cathode and improve the transverse focusing, which make the goal of high perveance and high compression ratio achieved. This gun plays a key role as the external injecting electron source of the independently-tunable-cells (ITC) RF gun. In order to understand the quality of the beam, a measurement system has been designed. The papers present the measurement system and the result of the test. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW011 | |
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| THPOW013 | ARM-Based Controller of Power Supply for Focus Solenoid of Klystron | 3957 |
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Funding: Supported by the National Science Foundation of China 11175181 By the Fundamental Research Funds for the Central Universities WK2310000056 Klystrons are widely used in accelerators to provide powerful microwave power to the accelerating structure of linac to accelerate particles. The stability of a klystron is affected by the beam quality of high voltage gun of the klystron. The focus solenoid is needed to provide focus magnetic field around the klystron. ARM-based high performance of current stability power supply is designed to improve the quality of focus magnetic field of klystron, with a two-loop-hybrid design, which could achieve fast dynamic response and high static stability performance, instead of analogue power supply design. The bench test of the ARM-based controlled is done and the commissioning of the controller needs be done in future study. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW013 | |
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| THPOW015 | Study of the Performance of Cs2Te Cathodes in the PHIN RF Photoinjector using Long Pulse Trains | 3960 |
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| The drive beam of CLIC requires unusually high peak and average currents which is challenging for the electron source. As an alternative to the thermionic electron gun foreseen in the baseline design, a photoinjector option is under study at CERN using the PHIN photoinjector, which was designed for a bunch charge of 2.3 nC and 1200 ns train length. During operation with nominal train length in 2014, a large pressure increase in the vacuum system, attributed to a heating of the Faraday cup, caused a degradation of the photocathode. To overcome this problem a vacuum window has been installed to separate the Faraday cup from the rest of the vacuum system. In addition the train length has been further increased to 1600 ns to advance the beam parameters towards CLIC requirements. In this paper recent improved photocathode lifetime measurements carried out under these new conditions will be presented and compared with earlier measurements. Furthermore, the utilized Cs2Te cathode has been analyzed with X-ray Photoelectron Spectroscopy (XPS) before and after its usage in PHIN to get a better understanding of photocathode surface deterioration effects, which will also be discussed. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW015 | |
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| THPOW016 | Transverse Energy Spread Measurements from GaAs Photocathodes at Variable Wavelengths | 3964 |
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| The transverse energy spread spectrometer (TESS) is an instrument specially developed at Daresbury Laboratory to measure the intrinsic transverse and longitudinal energy distributions from photocathode materials. Early work on the instrument has focussed on its use for the characterisation of GaAs photocathodes such as those commonly used in DC photoinjectors. More recently work has been conducted to extend the range of materials which can be evaluated using this apparatus, in particular by incorporating a monochromated white light source. New results are presented using the white light source to measure the energy spread of a GaAs photocathode across a range of different wavelengths to evaluate how this changes with excess energy. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW016 | |
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| THPOW017 | VELA Photoinjector Cavity RF Investigations | 3968 |
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| One of two ALPHA-X photocathode gun cavities, designed and fabricated at the Laboratoire de l'Accélérateur Linéaire, has been in operation on the VELA electron accelerator at Daresbury Laboratory since first beam in April 2013. In this time the maximum beam momentum recorded is 5.06 MeV/c. An investigation of the cavity has been performed with the aim of reconciling the expected momentum of over 6 MeV/c with the measured momentum. RF and beam simulation results are presented along with low power RF measurements of the cavity. One source of momentum loss, the flatness of the cathode face, is identified and rectified. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW017 | |
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| THPOW018 | Simulations of Field Emitted Dark Current Dynamics in DC Photoinjectors | 3971 |
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| Field emission is a concern in injectors with DC photoelectron guns because of the constant generation of dark current, which is accelerated down the beam line and can deteriorate the photoemitted bunch quality and lead to hardware damage. Simulations were carried out on the co-propagation of a field emitted, dark current halo and a photoemitted bunch in a typical 350 kV gun as used in an ERL or FEL injector, followed by a single cell buncher cavity. The photoemitted bunch repelled the halo longitudinally, leaving the area in the centre of the bunch with very low dark current, surrounded by two peaks of relatively high current at the front and back of the bunch. The peaks in current occur at all levels of dark current and were about 3.5 times the amplitude of the undisturbed dark current. The buncher caused the dark current to overcompress, forming a 'ghost' pulse an order of magnitude larger than the initial level of dark current, in front of the photoemitted bunch. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW018 | |
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| THPOW019 | Beam Characterisation and Machine Developments at VELA | 3975 |
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| An overview is presented of developments on VELA (Versatile Electron Linear Accelerator), an RF photo-injector with two user stations at Daresbury Laboratory. Numerous commissioning, machine development, beam characterisation and user experiments have been completed in the past year. A new beamline and a dedicated multiuser station have been commissioned and the first experiments performed. A number of measures have been taken to improve the stability of machine by mitigating a phase drift, laser beam transport drift and a coherent ~1 Hz beam oscillation. The 6D phase space of the electron beam has been characterised through quad scans, transverse tomography and with a transverse deflecting cavity. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW019 | |
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| THPOW020 | S-Band Photoinjector Investigations by Multiobjective Genetic Optimizer | 3979 |
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| Photoinjectors has witnessed great progress in the past few decades, with low duty cycle high gradient guns, such as normal conducting S/L band gun, pushing the peak beam brightness frontier, and CW guns, such as DC gun, SRF gun and VHF gun, pushing the average beam brightness frontier. Due to different degrees of complexity, pulsed high gradient photoinjectors are usually optimized by manual scans, while CW photoinjectors are optimized by multi-objective genetic optimizers. In this paper, a multi-objective genetic optimizer is used to revisit S-band photoinjector beam brightness optimizations, showing a trade-off between peak current and transverse emittance, with the optimized injector layout depending on bunch charge and peak current. For 200 pC case, the final beam core brightness at injector exit is close to cathode maximum brightness in the 'cigar beam' regime. Assuming a thermal emittance of 0.5 μm/mm and a beam charge of 200 pC, about 90 nm slice emittance at 20 A peak current is achieved. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW020 | |
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| THPOW021 | Generation of Homogeneous and Patterned Electron Beams using a Microlens Array Laser-Shaping Technique | 3983 |
| SUPSS020 | use link to see paper's listing under its alternate paper code | |
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Funding: Northern Illinois University - US DOE contract No. DE-SC0011831. Fermilab - US DOE contract No. DE-AC02-07CH11359. The Argonne wakefield facility - US DOE contract No. DE-AC02-06CH11357. In photocathodes the achievable electron-beam parameters are controlled by the laser used to trigger the photoemission process. Non-ideal laser distribution hampers the final beam quality. Laser inhomogeneities, for instance, can be "amplified" by space-charge force and result in fragmented electron beams. To overcome this limitation laser shaping methods are routinely employed. In the present paper we demonstrate the use of simple microlens arrays to dramatically improve the transverse uniformity. We also show that this arrangement can be used to produce transversely-patterned electron beams. Our experiments are carried out at the Argonne Wakefield Accelerator facility. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW021 | |
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| THPOW023 | Intrinsic Emittance Reduction in Transmission Mode Photocathodes | 3987 |
| SUPSS021 | use link to see paper's listing under its alternate paper code | |
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| High quantum efficiency (QE) and low emittance electron beams provided by multi-alkali photocathodes make them of great interest for next generation high brightness photoinjectors. Spicer's three-step model well describe the photoemission process, however, some photocathode characteristics such as their thickness have not been completely exploited to further improve the brightness of the generated electron beam. In this work, we report on the emittance and QE of a multi-alkali photocathode grown onto glass substrate operated in transmission and reflection modes at different photon energies. We observed a 20% reduction on the intrinsic emittance from the reflection to the transmission mode operation. This observation can be explained by inelastic electron-phonon scattering events experienced by electrons during their transit towards the cathode surface. This scattering will expect the further emittance reduction than the no scattering at the cryo-temperatures. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW023 | |
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| THPOW025 | Photocathode Growth and Characterization Advances at Cornell University | 3990 |
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| Alkali-antimonides based photocathodes have demonstrated outstanding performance in high brightness electron beam production suitable for a wide range of applications such as FELs, ERLs and UED and for use in photomultiplier devices with picosecond resolution aimed at photon counting application in medicine and High Energy Physics. The photocathode laboratory at Cornell University is dedicated to studying the growth procedures and characterizing the properties in a wide range of photocathodes materials. Different experimental arrangements and alkali metal sources have been successfully explored to date to synthesize photosensitive materials. Recent work on commissioning a new growth chamber equipped with effusion cells loaded with pure metal allowing uniform deposition over large area substrates resulted on successful growth of photocathodes with extended sensitivity in the IR part of the spectrum and high efficiency alkali antimonides containing Rb metal. This and other advances aimed at demonstrating superior photocathodes will be presented. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW025 | |
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| THPOW026 | LLNL X-band RF Gun Results | 3993 |
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Funding: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 An X-band test station and Inverse Compton Scattering (ICS) x-ray source has been built and commissioned at LLNL. The electron beam source is a unique 5.59 cell RF photoinjector, which will be described in detail, including: quantum efficiency, emittance measurements, energy spread and jitter, final focus spot size and stability, laser profile and final transport, and consistency with expectations based on beam dynamics simulations. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW026 | |
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| THPOW027 | Compact X-band Accelerator Controls for a Laser-Compton X-ray Source | 3996 |
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Funding: This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL's compact, tunable, laser-Compton x-ray source has been built around an advanced X-band photogun and accelerator sections and two independent laser systems. In support of this source, a complete integrated control system has been designed and built from scratch to provide access to the critical control points and continues to grow to simplify operation of the system and to meet new needs of this research capability. In addition to a PLC-based machine protection component, a custom, LabView-based suite of control software monitors systems including low level and high power RF, vacuum, magnets, and beam imaging cameras. This system includes a comprehensive operator interface, automated and expandable arc detection to optimize rf conditioning of the high-gradient structures, and automated quad-scan-based emittance measurements to explore the beam tuning parameter space. An overview of this system is presented, including the latest upgrades to FPGA-based hardware for the RF system controls. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW027 | |
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| THPOW028 | Automated Design for Standing Wave Electron Photoguns: TOPGUN RF Design | 3999 |
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Funding: DOE SCGSR and DOE/SU Contract DE-AC02-76-SF00515 Systematic design of RF photoguns involves multiple RF simulations in conjunction with beam dynamic simulations. RF simulations include tuning gun frequency, matching the gun to the feeding RF circuit, balancing the on axis electric fields between gun cells, minimizing surface electric and magnetic fields and power consumption, and optimizing separation of resonant mode frequencies. We created a tool that allows this multiple parameter optimization to be done automatically. We used SUPERFISH to accomplish the RF simulations. We present an example of the rf photogun TOPGUN design using these tools. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW028 | |
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| THPOW029 | Single Electron Extraction at the ELSA Detector Test Beamline | 4002 |
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| The Electron pulse Stretcher Facility ELSA delivers polarized and non-polarized electrons with an adjustable beam energy of 0.5 - 3.2 GeV to external experimental stations. Extraction currents available range down from 1 nanoampere to several atto-amperes provided by single electron extraction. Especially the high energy physics community requires detector test stations with electron tagging rates between 100 Hz to 100 kHz, imposing particular requirements for stable minimum-current extraction from the storage ring. These requirements are met with the implementation of a low-injection mode for the booster synchrotron and photomultiplier-based stored current monitoring, providing feedback for a selectable limit of the injected current. A homogeneous extraction current with duty factor > 80% is routinely granted by the excitation of a 3rd integer optical resonance. The setup of the low-current injection system and measurements of the extraction properties at the preliminary detector test beamline are presented. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW029 | |
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| THPOW030 | ELI Eectron Beam Line for Laser-plasma-driven Undulator X-ray Source | 4005 |
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| ELI LUX experiment of the ELI-Beamlines Project is based on electron beam, accelerated by the laser plasma wakefield. ELI LUX aims to deliver for users the X-ray beams with radiation length (0.4-4.5)nm and the peak brilliance up to 1023 photons/(s mrad2 mm2 0.1% B.W.), which makes this source comparable with modern synchrotron sources. To provide small transverse size of the electron beam and small transverse beam divergence in the undulator, permanent quadrupole magnets with high gradient of the magnetic field up to 510 T/m are used in the electron beam line. In frame of this report we present main features of the designed electron beam line. 3D modeling of the magnetic field in the quadrupole magnets has been performed. Effects of the chromatic and spherical aberrations are taken into consideration. The electron beam dynamic is studied by using symplectic integration though the 3D field maps of the permanent quadrupole magnets. Effects of the space charge of the electron beam, beam collimation, injection and alignment errors and realistic field errors are discussed. Finally parameters of the photon beam, generated in compact undulator, are presented in this report. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW030 | |
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| THPOW032 | Experimental Test on the TPS Booster Injection Scheme Exploration and the Associated Bunch Train Analysis | 4008 |
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| In order to explore the tuning range of injection septum and kicker for TPS booster operation, an experimental test on the designed injection scheme has been performed. Tuning of these injection units is based on the top-up operation process for storage ring vacuum cleaning purpose. It is set for a fast beam accumulation in the storage ring where the stored beam variation range is selected for efficient operation consideration. The measurement results of booster beam current variation while tuning of injection septum and kicker are presented. A preliminary analysis concerning the observation of deteriorated phase space acceptance in the TPS booster is given in this report. This study also includes an effort to extend the present available operation bunch train for TPS booster. It shows that the increase of the booster beam current by bunch train tuning indicates an upper bound of about 400 ns. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW032 | |
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| THPOW033 | Transient Orbit of Injection in Taiwan Light Source Storage Ring | 4012 |
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| Top-up operation has been started since many years ago at Taiwan Light Source Storage Ring (SR). For this operation it is important to reduce the beam injections should not excite the oscillation of stored beams. For further reduction of these oscillations, corrections with kicker-magnets are used. The details of the study will be reported in this paper. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW033 | |
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| THPOW034 | TLS Booster Injection Scheme Exploration | 4016 |
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| In this paper, the booster injection efficiency and the parameter working range related to key components in-cluding septum magnet and kicker magnet for Taiwan Light Source (TLS) injector operation are introduced. Booster injection scheme for different lattice is explored by machine study plan using injector property. The study result may be used by the operator as booster injection parameter fine tuning reference. It is also helpful for the advanced injection scheme exploration. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW034 | |
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| THPOW035 | Statistical Analysis Package for the Opearion Monitoring at the TLS | 4019 |
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| Machine operation parameters and interruptions to user beam at Taiwan Light Source (TLS) and Taiwan Photon Source (TPS) are recorded in databases. The data retrieve to TLS uses the File Transfer Protocol (FTP) with two separated databases 10 Hz and 0.1 Hz for quick or detail data analysis options. TPS data storage uses the open source database PostgreSQL. A statistical analysis package HISTORY has been writ-ten in Microsoft Visual C to perform operation monitor-ing and data mining. Operation and failure statistics func-tions are produced for performance evaluation and User Administration & Promotion Office user time statistics. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW035 | |
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| THPOW036 | Evaluation of Immutability against Radiation-induced Demagnetization for a Hybrid Wiggler with NdFeB Magnets at the Canadian Light Source | 4022 |
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| The BioXAS beamline at Canadian Light Source installed a hybrid wiggler in 2013. Quantitative studies building on the experience of other facilities suggest the wiggler's NdFeB magnets are at risk of demagnetization due to radiation induced by the synchrotron's 2.9 GeV electrons. We use a phenomenological model to convert simulated peak demagnetizing fields into a radiation dose corresponding to a chosen %-demagnetization, and compare against an estimated dose per year due to injected beam. We find that injecting with the wiggler closed will cause 1% demagnetization in sections of its magnet blocks within 2 years of operation, assuming a worst case scenario. The wiggler has thus far been forced open for injections, but this will cease to be an option when CLS moves to top-up operation. In a related test, qualitative measurements of radiation during injections with the wiggler closed were taken by covering its magnets in Polaroid film. We find that radiation drops significantly when the injection efficiency is well-tuned. Our results suggest the wiggler will not receive damaging levels of radiation at closed gap so long as the injection system remains optimized. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW036 | |
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| THPOW037 | Simulated and Measured Magnetic Performance of a Double APPLE-II Undulator at the Canadian Light Source | 4025 |
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| Assembly and shimming are underway for a double APPLE-II type elliptically polarized undulator (i.e. two magnet arrays installed side by side on a single support structure) at the Canadian Light Source. The device is planned to be installed in spring 2017. Extensive preparation was done prior to device assembly, particularly in development of a simulated annealing algorithm for magnet virtual shimming, as well as assembly procedures that minimized positional errors in the installed magnet blocks. In this paper we present measurements taken throughout the shimming process, and compare with predictions from a RADIA model where each magnet block was magnetized uniquely according to individual Helmholtz coil measurements. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW037 | |
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| THPOW038 | First Results from Two Novel In-vacuum Magnetic Field Measurement Devices as Built at HZB | 4028 |
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| The characterization of cryogenic in vacuum permanent magnet undulators with periods less than 20 mm and correspondingly narrow gaps requires new in-vacuum measurement systems. The positioning accuracy of the HZB in-vacuum Hallprobe bench has substantially been improved (a few μm) with appropriate feedback systems. A new in-vacuum cable tray has been developed. Another system for field integral measurements, an in-vacuum moving wire, is under commissioning. Both devices are presented. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW038 | |
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| THPOW039 | Measurements of the Lattice Modifications for the Cryogenic Undulator CPMU17 | 4031 |
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| A 2 mrad-canted double undulator system is in preparation as the wide energy range light source for the Energy Material in-situ Laboratory EMIL at the HZB storage ring BESSY II. The cryogenic undulator CPMU-17 is the hard X-ray device of the double undulator system. The soft X-ray undulator UE-48 is of the APPLE II type. It was installed and commissioned a few months ago, whereas the CPMU-17 is under fabrication. The CPMU-17 will employ a minimum magnetic gap of 5.5mm. Including a CuNi-foil for RF-shielding and geometric tolerances the free aperture is planned to be 5.0 mm. The BESSY II lattice has been modified locally in order to cope with the small gap device. The adapted betatron functions with a shifted vertical beam waist were measured and fitted with LOCO. The new optics agrees with the predicted performance. The free aperture at the installation place of the CPMU-17 was measured with four vertical scrapers. It is compatible with the projected minimum undulator gap. Finally, the measured injection efficiency with the new EMIL optics switched on is compatible with top-up operation (injection efficiency ≥ 90 %). | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW039 | |
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| THPOW040 | Insertion Devices for Spring-8 Upgrade Project | 4035 |
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| In the upcoming major upgrade project of SPring-8 (SPring-8-II) planned in the early 2020's, the electron energy will be reduced from 8 GeV to 6 GeV and the straight sections will be shortened by nearly 2 m to accommodate more magnets, for the purpose of reducing the emittance down to around 100 pm.rad. The insertion devices (IDs) currently installed in SPring-8 are not compatible with the above upgrade plan, and thus most of them should be replaced with new ones optimized in the new storage ring, or at least be shortened to fit into the new straight sections. We report the status of R&Ds toward realization of IDs for SPring-8-II, such as shortening the magnetic period, reforming the fundamental structure of IDs to reduce the total cost and manufacturing lead time, and refurbishment of existing IDs for shorter lengths. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW040 | |
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| THPOW041 | Field Error Correction Considerations of Cryogenic Permanent Magnet Undulator (CPMU) for High Energy Photon Source Test Facility (HEPS-TF)* | 4038 |
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| Considerations are made for field error corrections of a 2m-long CPMU in built for HEPS-TF. Field changes in cooling to liquid nitrogen temperature are simulated. 1st field integral of terminal changes by tens of Gauss cm and RMS of phase errors induced by cold contraction is less than 1° when temperature gradient along girder is below 1.5K/m. Field signature of magic finger is unchanged with temperature. Strategy of the field error correction is discussed. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW041 | |
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| THPOW042 | Start-to-End Simulation on Terahertz Superradiation of Ultrashort Electron Bunch in an Undulator | 4041 |
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| The narrowband, intense and frequency-tunable THz radiation can be generated by letting an ultrashort electron bunch pass through an undulator. Start-to-end simulation of terahertz radiation from electron bunch in an undulator is studied in this paper. GPT code is used to track particle distribution from the photocathode RF gun to the entrance of the undulator and Genesis 1.3 is applied to simulate the radiation. The simulation results agree well with theoretical predictions. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW042 | |
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| THPOW045 | Development of PAL-XFEL Undulator System | 4044 |
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| Pohang Accelerator Laboratory (PAL) is developing a 0.1 nm SASE based FEL based on 10 GeV S-band linear accelerator named PAL-XFEL. At the first stage, PAL-XFEL needs two undulator lines for photon source. The hard X-ray undulator line requires 20 units of 5 m long hybrid-type conventional planar undulator and soft X-ray line requires 7 units of 5 m long hybrid type planar undulators. PAL is developing undulator magnetic structure based on EU-XFEL concepts. In this report, the results of final pole height tuning results, and magnetic measurement results will be presented. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW045 | |
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| THPOW046 | Status of Insertion Device Measurement Systems at MAX IV Laboratory | 4047 |
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| An insertion device lab was setup at MAX IV Laboratory and the production of insertion devices, mainly out-of-vacuum is ongoing and aided by new magnetic measurement systems. A new 5.5 m long Hall probe bench is used for field map measurements and a new hybrid flip coil and stretch wire system will be used for field integrals of full devices as well as individual magnet blocks characterisation. This paper describes these magnetic measurement systems and their achieved and expected performance. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW046 | |
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| THPOW048 | Optimization of a Multipole Wiggler for Tps | 4050 |
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| Taiwan Photon Source (TPS) is a synchrotron radia-tion facility with electron energy 3 GeV that was commissioned in 2015. Taiwan Light Source (TLS) with electron energy 1.5 GeV concurrently provides user time. Three beam lines of TLS supply photons of energy 6-18 keV for user experiments; these beam lines are served with an in-achromatic superconduct-ing wiggler (IASW, 3.1 T). This superconducting inser-tion device has the disadvantages of complicated maintenance and operation. A traditional multipole wiggler (MPW) magnet of hybrid type is hence planned to be installed in TPS to cover the range of photon energy of IASW for user experiments. For the design of the magnetic circuit, the side block and the extreme block are arranged surrounding a Permendur Vanadium cobalt steel pole that enhances the field strength and good field region of a MPW magnet. The dynamic integral field and the demagnetizing field of MPW magnet were estimated. The optimization of the pole dimensions and photon characteristics were simu-lated and are discussed in this work. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW048 | |
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| THPOW049 | Status of Insertion Devices at Taiwan Photon Source | 4054 |
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| The storage ring of Taiwan Photon Source (TPS) has eighteen short straight sections (length 7 m) and six long straight sections (length 12 m). In phase I, three elliptically polarized undulators of type APPLE II and seven in-vacuum undulators, which included four in-vacuum undulators and two elliptically polarized undulators in three double mini-βy sections, were installed. Commissioning of the insertion devices began in 2015 November. The influence of insertion devices on the electron beam and the results after compensation are presented. Problems during the commissioning induced by the electron beam and by radiation, and their solutions, are also explained. For insertion devices in phase II and for devices developed in TPS, the preliminary designs are presented herein, to cover from the VUV to the hard X-ray region. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW049 | |
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| THPOW050 | Upgrade of Septum Magnets of the Transfer Line in TPS | 4057 |
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| Taiwan Photon Source (TPS) is a 3-GeV light source. The full current of the storage beam and commissioning of insertion devices are still in progress. An improved injection between the booster ring (BR) and the storage ring (SR) was implemented to increase the efficiency of injection and the reliability of the electrical parts. A DC septum (length 0.8 m) was replaced with an AC septum (length 1 m, type C) to decrease the leakage field and to relax the loading of the power supply. Mapping the field with mu-metal shielding was also implemented to diminish the leakage field from the AC septum. The lattice of the transfer line between the booster ring and the storage ring, BTS, was also rearranged to meet the new injection requirements. The performance of the AC septum with mu-metal shielding and the upgrade of the BTS lattice are discussed in this paper. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW050 | |
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| THPOW051 | Design and Construction of Compact Electromagnetic Undulator for THz Radiation Production | 4060 |
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Funding: Chiang Mai University Research Fellowship Program The goal of this research is to design and construct a compact electromagnetic undulator. This insertion device will be installed at the PBP-CMU-LINAC system of Chiang Mai University (CMU), Thailand, to produce THz radiation. The undulator magnet is designed by using 2D POISSON and 3D RADIA computer code to optimize the magnet dimensions. The width of iron pole (W) should be 12 mm. The length of iron pole (L) should be about 80 mm long and the thickness of return yoke (d) should be more than 10 mm. The magnet design, the in-house con-struction of the magnet, and the measurement results will be presented. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW051 | |
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| THPOW052 | Recent Magnetic Measurement Activities at NSLS-II Insertion Device Laboratory | 4063 |
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| National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory (BNL) is a new 3 GeV third generation electron storage ring designated to provide extremely intense beams of X-ray, ultraviolet, and infrared light for basic and applied research. Insertion devices (IDs) play a significant role in achieving the high performance demands of NSLS-II. An accurate magnetic characterization and proper corrections of these devices are essential activities in the development of a state-of-the-art light source facility. This paper describes the results of the latest magnetic measurement activities at the NSLS-II ID laboratory. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW052 | |
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| THPOW054 | Cumulative Damage of Ultrafast Laser Pulses | 4066 |
| SUPSS023 | use link to see paper's listing under its alternate paper code | |
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| We demonstrate experimentally that damage threshold fluence (DTF) for fused silica changes with the number of femtosecond laser (10Hz 600Hz, 655 fs, 800nm) shots. Based on the experimental data we were able to develop a model which indicates that the change in DTF varies with number of shots logarithmically (lnp) up to a critical value. Above this value, DTF approaches an asymptotic value. Both DTF for a single shot and the asymptotic value as well as the critical value where this happens are extrinsic parameters dependent on the configuration (repetition rate, pressure and geometry near or at the surface). Indications are that the power of this dependence (p) is an intrinsic parameter independent of the configuration. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW054 | |
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| THPOW056 | Fiber Laser Development for Dielectric Laser-driven Accelerator and Electron Beam Source | 4070 |
| SUPSS024 | use link to see paper's listing under its alternate paper code | |
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Our group is aiming for developing a table-top electronμbeam source, whose beam size is micro-meter order so that we can irradiate just the nuclei of cells (1μm) and observe the behavior in real time. This beam source will be realized by dielectric laser-driven accelerators(DLAs), which is expected to produce acceleration gradients of ~GV/m. To drive these accelerators, ultra-short pulse laser has to be incident to the structure*. We chose Ytterbium (Yb) fiber laser for generating and amplifying ultra-short laser pulse, which has high quantum efficiency and can easily pumped by LD, and is proper to produce ultra-short pulses because of its wide-band oscillation. We succeeded in getting ultra-short pulse (central wavelength: {1030} nm, average output: 10 W, pulse duration: ~10 ps, reputation rate: 84 MHz) from Yb fiber laser system. Also in order to make electron bunch by photo cathode, we then converted the obtained IR laser to UV of 258 nm (4ω) using BBO and LBO crystals. We are planning to amplify the pulses by Yb:YAG in future, which has its amplification band in {1030} nm.
* K. Koyama el al., "Design Of Photonic Crystal Accelerator For Radiation Biology," IPAC'12 Proceedings (2014) |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW056 | |
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| THPOW057 | Direct High Power Laser Diagnostic Technique on Focused Electron Bunch | 4073 |
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| In laser produced plasma EUV source, high intensity pulse CO2 laser is essential for plasma generation. To achieve high conversion efficiency and stable EUV power, we would like to measure a laser profile in the interaction point. However, there is no way to measure directly the laser profile of such a high intensity laser at the focus point. Therefore, we have been developing laser profiler based on laser Compton scattering(LCS). LCS signal by using focused electron beam shows 1D laser profile. 2D laser profile can be reconstructed by one-dimensional laser profiles from various angles using computer tomography. This method is suitable for high intensity laser, but very small spot size of electron beam is required. To obtain small spot size, we used S-band Cs-Te photocathode RF-Gun and specially designed solenoid lens at Waseda university. We already succeeded in observing minimum beam size of about 20 μm rms and this is adequate to scan the CO2 laser. In this conference, we will report the result of the laser Compton scattering with pulse CO2 laser, the preparatory experiment in measuring a metal wire cross section and the present progresses. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW057 | |
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| THPOW058 | Drive Laser System for the DC-SRF Photoinjector at Peking University | 4076 |
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| The DC-SRF photoinjector, developed at Peking University, uses Cs2Te as the photocathode and accordingly 266 nm laser is used as the drive laser. A drive laser sys-tem，which includes a 1064 nm laser oscillator, a four-stage amplifier, and second and fourth harmonic genera-tors, has been designed and applied successfully. To avoid the high average current electron beam from hitting the vacuum tube and causing safety problems, a laser pulse selector with an EO modulator has been designed and included into the laser drive system to reduce the repetition rate of electron pulses during the DC-SRF photoinjector commissioning. It can adjust the repetition rate of laser pulses from 81.25 kHz to 81.25 MHz. In this paper, we introduce the drive laser system and describe the laser pulse selector in detail. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW058 | |
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| THPOW059 | UV Pulse Shaping with a-BBO Crystals for the Photocathode RF Gun | 4079 |
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| Recently, manipulation with the drive laser plays a significant role in high brightness electron beam production by the photocathode RF gun. The method based on pulse stacking with birefringent crystal serials was tried to longitudinally shape ultraviolet laser pulse. Using four or five pieces of a-BBO crystals to stack an input UV pulse with appropriate initial duration into 16 or 32 sub-pulses to form quasi flattop UV laser pulse, which can be applied for emittance optimization of the electron beam based on the photocathode RF gun. Moreover, the negative slop of the energy transmittance of a-BBO serials is also revealed to be a passive stabilization mechanism for energy jitter reduction in the driving laser. With appropriate design of a-BBO serials, this method can fulfill the requirements for driving laser in a broad scope of applications such as x-ray FELs and high-power Terahertz(THz) radiation production. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW059 | |
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| THPOW060 | Basic Design of Control System for IPM Linear Accelerator | 4082 |
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| A control system has been designed for the commissioning of 10 MeV linear accelerator which is under construction in institute for research in fundamental science (IPM). The IPM e-Linac is a traveling wave accelerator consisting of 62 components in five major sections: control and safety, beam injection, radio frequency production and transmission, acceleration tube and target. The existence of a central control system for controlling and monitoring all parts of the machine is necessary. The aim of the system design is to implement a fast and reliable control system which is easy to operate and extensible for future upgrades and improvements. For this purpose, EPICS has been chosen as the main environment due to high performance and distributed structure. In this system, Siemens PLC is used as EPICS IOC and graphical designs will performed by CSS and WinCC. In this study, first we present a brief description of the IPM electron linear accelerator, and then architecture of the control system will be discussed. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW060 | |
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