| Paper | Title | Page |
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SUSPF001 |
Probing the Forced Dynamic Aperture in the LHC at Top Energy Using AC Dipoles | |
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| Measurements of the dynamic aperture in colliders are a common method to ensure machine performance and offer an insight in the nonlinear content of the machine. Such direct measurements are very challenging for the LHC and High Luminosity LHC. Forced dynamic aperture has been demonstrated for the first time in the LHC at injection energy as a potential new observable to safely probe the nonlinear content of the machine. This paper presents the first measurements of forced dynamic aperture at top energy and discusses the proposed measurement schemes and challenges. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF033 | |
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SUSPF002 |
Experimental Interaction Region Optics for the High Energy LHC | |
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Funding: Work supported by the Horizon 2020 project EuroCirCol, grant 654305 and by the Science and Technology Facilities Council The High Energy LHC (HE-LHC) is one option for a next generation hadron collider explored in the FCC-hh program. The core concept of the HE-LHC is to install FCC-hh technology magnets in the LHC tunnel. The higher beam rigidity and the increased radiation debris, however, impose severe challenges on the design of the triplet for the low beta insertions. In order to achieve 25 cm β* optics and survive a lifetime integrated luminosity of 10 ab-1 a new longer triplet was designed that provides sufficient shielding and enough beam stay clear. This triplet has been designed using complimentary radiation studies to optimise the shielding that will also be presented. The optics for the rest of the interaction region had to be adjusted in order to host this more rigid beam and longer triplet whilst leaving enough room for crab cavities. Moreover, the effects non-linear errors in this triplet have on the dynamic aperture will be outlined. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMK006 | |
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SUSPF003 |
A Design Study of the Electron-driven ILC Positron Source Including Beam Loading Effect | |
| MOPMF077 | use link to access more material from this paper's primary paper code | |
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| The International Linear Collider (ILC) is a next-generation accelerator for high-energy physics to study the Higgs and top sector in the Standard Model, and new physics such as supersymmetry and dark matter. ILC positron source based on Electron-driven method has been proposed as a reliable technical backup. In this article, we report the design study of the positron source based on the off-the-shelf RF components. The positron is generated and accelerated in a multi-bunch format. To compensate the energy variation by the transient beam loading effect, we employ AM (Amplitude Modulation) technique and the results were 16.60 ± 0.14 MV (peak-to-peak) for L-band 2m cavity driven by 22.5 MW power and 25.76 ± 0.19 MV (peak-to-peak) for S-band 2m ac-celerator driven by 36 MW power with 0.78 A beam load-ing. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF077 | |
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SUSPF004 |
Pre-Booster Ring Considerations for the FCC e+e− Injector | |
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| The FCC-e+e− injector complex needs to produce and to transport a high-intensity e+/e− beam at a fast repetition rate for topping up the collider at its collision energy. Two different options are under consideration as pre-accelerator before the bunches are transferred to the high-energy booster: using the existing SPS and a completely new ring. The purpose of this paper is to explore the needs and parameters of the existing SPS and the conceptual design of an alternative accelerator ring with injection and extraction energies of 6 and 20 GeV, respectively. In this study, the basic parameters of both choices are established, including the optics design and layout updates. Consideration for non-linear dynamics optimization and the impact of intra beam scattering are also presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-MOPMF002 | |
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SUSPF005 |
From Coherent Harmonic Generation to Steady State Microbunching | |
| THPMK113 | use link to access more material from this paper's primary paper code | |
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| Steady state microbunching (SSMB) is an electron storage ring based scheme proposed by Ratner and Chao to generate high average power narrow band coherent radiation with wavelength ranging from THz to EUV. One key step towards opening up the potential of SSMB is the experimental proof of the SSMB principle. In this paper, the SSMB experiment planned and prepared by a recently established collaboration is presented starting from a modified coherent harmonic generation (CHG). Single particle dynamics of microbunching in an electron storage ring are analyzed. Though oriented for CHG and SSMB, some of the effects analyzed are also important in cases like bunch slicing, bunch compression, FEL beam transport lines etc, in which precise longitudinal phase space manipulations are involved. These dynamics together with some SSMB related collective effects are to be investigated on the storage ring MLS in Berlin. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK113 | |
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SUSPF006 |
Mobile Free-Electron Laser for Remote Atmospheric Survey | |
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Funding: This paper is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05- 06OR23177. E.J. was supported by the Virginia Space Grant Consortium, grant number 16-589. Reliable atmospheric surveys for carbon distributions will be essential to building an understanding of the Earth's carbon cycle and the role it plays in climate change. One of the core needs of NASA 's Active Sensing of CO2 Over Nights, Days and Seasons (ASCENDS) Mission is to advance the range and precision of current remote atmospheric survey techniques. The feasibility of using accelerator-based sources of infrared light to improve current airborne lidar systems has been explored. A literary review has been conducted to asses the needs of ASCENDS versus the current capabilities of modern atmospheric survey technology, and the parameters of a free electron laser (FEL) source were calculated for a lidar system that will meet these needs. By using the "Next Linear Collider" from the Stanford Linear Accelerator Center (SLAC), a mobile FEL-based lidar may be constructed for airborne surveillance. The calculated energy of the lidar pulse is 0.1 joule: this output is a two orders of magnitude gain over current lidar systems, so in principle, the mobile FEL will exceed the needs of ASCENDS. Further research will be required to asses other challenges to mobilizing the FEL technology. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK026 | |
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SUSPF007 |
Lattice Design for a 1.2 GeV Storage Ring | |
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| It is a very effective way to bring down the emittance of storage ring by using the MBA lattice design. Based on this concept, some other solutions have been developed to reduce the emittance furthermore for recent years. In this paper, the lattice design for a 1.2 GeV storage ring will be presented. The solution of horizontal and longitudinal gradient bending magnets tried in this lattice is going to be discussed in detailed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK071 | |
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SUSPF008 |
Lattice Tweaking Using A Tune Knob Based On Global Mechanism | |
| THPMK129 | use link to access more material from this paper's primary paper code | |
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| The transverse tunes are important parameters for a storage ring and tune knobs are used to adjust the tunes in a specific range. Usually for large rings, a set of quadrupoles is set on the straight sections for the use of tune knob. A tune knob has been designed for the HLS-II storage ring without affecting the twiss parameters of the injection section. This paper introduces the design and online test of this tune knob. The quadrupoles are adjusted according to the simulation results and the tunes are measured and calibrated. The online test results show that the tune knob design works well on the HLS-II storage ring and can be applied for various machine studies. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK129 | |
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SUSPF009 |
A Possible Scheme for Generating High-harmonic Coherent Radiation in Storage Rings | |
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| A possible scheme for storage ring FEL which can introduce small energy dispersion and emittance simultaneously to generate intense coherent light in the storage rings is described. Based on a modified version of echo-enabled harmonic generation from free-electron lasers, the technique uses a dogleg and a wave-front tilted seed laser, one normal seed laser and two chicanes to make three-dimensional manipulation of the electron beam phase space, producing high-harmonic microbunching of a relativistic electron beam. Due to small energy dispersion and emittance growth, the storage rings do not need long damping time to recover the quality of the electron beams, so this scheme will significantly improve the performance of FELs based on rings. Theoretical analysis and numerical simulations demonstrate the capability of the proposed technique in Shanghai Synchrotron Radiation Facility. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK075 | |
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SUSPF010 |
Temporal X-ray Reconstruction Using Temporal and Spectral Measurements | |
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Transverse deflecting structures (TDS) are widely used in accelerator physics to measure the longitudinal density of particle bunches. When used in combination with a dispersive section, the whole longitudinal phase space density can be imaged. At the Linac Coherent Light Source (LCLS), the installation of such a device downstream of the undulators enables the reconstruction of the X-ray temporal intensity profile by comparing longitudinal phase space distributions with lasing on and lasing off*. However, the resolution of this TDS is limited to around 1 fs rms (root mean square), and therefore, in most cases, it is not possible to resolve single self-amplified spontaneous emission (SASE) spikes within one photon pulse. By combining the intensity spectrum from a high resolution photon spectrometer** and the temporal structure from the TDS, the overall resolution is enhanced, thus allowing the observation of temporal, single SASE spikes. The combined data from the spectrometer and the TDS is analyzed using an iterative algorithm to obtain the actual intensity profile. In this paper, we present the reconstruction algorithm as well as analyzed data obtained from simulations which shows the reliability of this method. Real data will be published at a later stage.
*Y. Ding et al., Phys. Rev. ST AB, 14, 120701, 2011. **D. Zhu et al., Appl. Phys. Lett., 101, 034103, 2012. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF076 | |
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SUSPF011 |
Suppression of Microbunching Instability Using a Quadrupole Inserted Chicane in Free-Electron-Laser Linacs | |
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| The microbunching instability (MBI) driven by beam collective effects in a linear accelerator of a free-electron laser (FEL) facility can significantly degrade the electron beam quality and FEL performance. A method exploited longitudinal mixing derived from the natural transverse spread of the beam was proposed several years ago using two dipoles to suppress the instability. In this paper, instead of using bending magnets to introduce the transverse-to-longitudinal coupling, which will lead to an inconvenient deflection of the downstream beam line, we propose a scheme using a quadrupole inserted chicane to introduce the longitudinal mixing inside the accelerator transport system to suppress this instability. And we finally eliminate the transverse-to-longitudinal coupling after the dogleg section. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF082 | |
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SUSPF012 |
Power Enhancement of Free-Electron Lasers Oscillators With the Natural Gradient of a Planar Undulators | |
| THPMK138 | use link to access more material from this paper's primary paper code | |
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Funding: Work supported by National Natural Science Foundation of China (No. 21327901, 11205156) Transverse Gradient Undulator (TGU) has been proposed with the initial purpose of mitigating the gain degradation in free electron laser (FEL) oscillators driven by beams with a large energy spread. However, a special-designed TGU with a fixed transverse gradient is required to enhance the gain. In this paper, we investigate using the natural field gradient of a normal planar undulator instead of a TGU to enhance the FEL oscillator (FELO) power. In this method, the beam is first vertically dispersed by a dogleg and then the dispersed beam passes through a normal undulator with a vertical off-axis orbit. Theoretical analysis and numerical simulation based on parameters of FELiChEM are presented. It demonstrates that this scheme can enhance the FEL power with careful optimization of dispersion strength and vertical beam orbit offset, especially when the energy spread is relatively large. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK138 | |
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SUSPF013 |
Micro Bunch Rotation and Coherent Undulator Radiation From a Kicked Beam | |
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| Recent observations of x-rays from a microbunched beam that has been kicked off-axis have shown coherent radiation at surprisingly large angles, in some cases reaching 30-50 uRad. Previous work on the topic has suggested that radiation at such large angles is inconsistent with classical radiation theory because microbunches cannot tilt. Here we show that, when kicked in a quadrupole lattice, microbunches can automatically tilt toward a new direction of propagation. This allows for coherent radiation farther off axis. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK082 | |
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SUSPF014 |
Simulation of Inverse Compton Scattering and Its Implications on the Scattered Linewidth | |
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Funding: This paper is authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Compton scattering, though first described some one hundred years ago, has recently experienced a surge of interest due to the search for energy sources that are capable of yielding low emission bandwidths. In particular, the desire for hard x-rays with energies greater than 10 keV has led to increased study of inverse Compton sources. The rise in interest concerning inverse Compton sources has increased the need for efficient models that properly quantify the behavior of scattered radiation given a set of interaction parameters. The current, state-of-the-art, simulations rely of Monte Carlo-based methods, which may fail to properly model collisions of bunches in low-probability regions of the spectrum. Furthermore, the random sampling of the simulations may lead to inordinately high runtimes. Our methods can properly model behaviors exhibited by the collisions by integrating over the emissions of the electrons in the bunch in a lessened amount of time. Analytical simulations of Gaussian laser beams closely verify the behavior predicted by an analytically derived scaling law describing bandwidth of scattered radiation. Current affiliation of primary author (Nalin Ranjan) is Princess Anne High, Virginia Beach, VA 23452, USA. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF005 | |
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SUSPF015 |
Design of 9/6 MeV S-band Electron Linac Structure with 1.5 Bunching Cells | |
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Funding: University of Science and Technology of Korea The Korea Atomic Energy Research Institute (KAERI) has been developing several 9/6 MeV dual energy S-band RF electron linear accelerators (linacs) for non-destructive testing such as container inspection system. Until now the bunching cell of the linac has a full-cell geometry. However, to maximize the acceleration of electrons after emission from the electron gun, the geometry of the first bunching cell is modified from a full-cell to a half-cell. The optimization of Q-factor and flatness of electric field along the linac structure can be obtained by adjusting diameters of bunching and power coupling cells. By adjusting gap of the first side-coupling cell, we can optimize the field ratio between the bunching cells and normal accelerating cells. In this paper, we describe design concepts of a 9/6 MeV linac with 1.5 bunching cells as well as optimization of RF parameters such as the quality factor, resonance frequency, and electric field distribution. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK139 | |
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SUSPF016 |
RF Design of the X-band Linac for the EuPRAXIA@SPARC_LAB Project | |
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| We illustrate the RF design of the X-band linac for the upgrade of the SPARC_LAB facility at INFN-LNF (EuPRAXIA@SPARC_LAB). The structures are travelling wave (TW) cavities, working on the 2π/3 mode, fed by klystrons with pulse compressor systems. The tapering of the cells along the structure and the cell profiles have been optimized to maximize the effective shunt impedance keeping under control the maximum value of the modified Poynting vector, while the couplers have been designed to have a symmetric feeding and a reduced pulsed heating. In the paper we also present the RF power distribution layout of the accelerating module and a preliminary mechanical design. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK058 | |
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SUSPF017 |
E-field Measurement of 9.3 GHz RF cavity for 6 MeV LINAC | |
| THPMK084 | use link to access more material from this paper's primary paper code | |
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In order to achieve performance close to the design value, fabricated cavity was tuned at Sunkyunkwan university. Tuning was done in two step: each cell tuning and bead-pull system. Each cell tuning was used to determine the status of each cell and to remove the stop-band. Bead-pull system was used to measure the E-field distribution and obtain the required field flatness. This paper describes each cell measurement data and bead-pull measurement system and data.
x-band, linac, measurement |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK084 | |
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SUSPF018 |
Study of the Saturation of Radiation Energy Caused by the Space Charge Effect in a Compact THz Coherent Radiation Source | |
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Funding: Institute of Advanced Energy, Kyoto University To generate an intense quasi-monochromatic Terahertz Coherent Undulator Radiation (THz-CUR), a compact linac system, which employs a magnetic electron bunch compressor with a beam energy of 4.6 MeV, has been constructed at Kyoto University. The THz-CUR has suc-cessfully been generated in a frequency range from 0.16 to 0.65 THz with a bunch charge of 60 pC. The maximum micro-pulse energy of THz radiation was observed higher than 1 μJ at 0.16 THz with 160 pC. However, when a bunch charge was higher than 80 pC, the micro-pulse energy of THz radiation gradually went to the saturation and obviously at the bunch charge higher than 110 pC because of the bunch lengthening and degradation of electron beam quality due to the space charge effect. The dependence of a bunch length on a bunch charge has been studied by GPT simulation and compared with CTR and CUR experiments. The trends of the measured results from CUR and CTR are in good agreement with the GPT simulation. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF074 | |
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SUSPF019 |
Initial Testing of Techniques for Large Scale Rf Conditioning for the Compact Linear Collider | |
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| Nominal operating conditions for the Compact Linear Collider (CLIC) 380 GeV requires 72 MV/m loaded accelerating gradients for a 180 ns flat-top pulse. Achieving this requires extensive RF conditioning which past tests have demonstrated can take several months per structure, when conditioned at the nominal repetition rate of 50 Hz. At CERN there are three individual X-band test stands currently operational, testing up to 6 structures concurrently. For CLIC's 380 GeV design, 28,000 accelerating structures will make up the main linac. For a large scale conditioning programme, it is important to understand the RF conditioning process and to optimise the time taken for conditioning. In this paper, we review recent X-band testing results from CERN's test stands. With these results we investigate how to optimise the conditioning process and demonstrate the feasibility of pre-conditioning the structures at a higher repetition rate before installation into the main linac. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK103 | |
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SUSPF020 |
Beam Dynamics Studies for Beam Focusing and Solenoid Alignment at SINBAD | |
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SINBAD (Short INnovative Bunches and Accelerators at DESY) facility under construction at DESY plans to host several experiments for the production of ultra-short bunches and will be a test facility for high-gradient compact novel acceleration techniques. The ARES (Accelerator Research Experiment at SINBAD) linac is foreseen to produce ultra-short bunches to be injected e.g. into Novel Dielectric Laser Acceleration structures or Laser Wake-Field Acceleration experiments. The work presented in this paper is based on optimization of the focusing system consisting of solenoids for the ARES, which have been studied earlier in detail but is revisited for updated beamline. Moreover tolerances for the possible misalignment of solenoids are presented investigating the effect on the beam properties during the gun commissioning.
* J. Zhu, R. Assmann, U. Dorda, B. Marchetti, "Matching sub-fs electron bunches for laser-driven plasma acceleration at SINBAD", Nucl. Instrum. Methods Phys. Res., Sect. A 829, 229 (2016) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF001 | |
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SUSPF021 |
Smith-Purcell Radiation for Bunch Length Measurements at the Injection of MESA | |
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Funding: Federal Ministry of Education and Research MELBA is a test apparatus for the injector of the energy recovering, superconducting accelerator MESA in Mainz. A chopper-buncher system containing two circularly deflecting cavities and a first and second harmonic buncher cavity have been built. They serve to produce short bunches with a longitudinal extension < 600 μm (one degree of RF-phase) in the longitudinal focus for beam currents of up to 10mA. We intend to use Smith-Purcell Radiation (SPR) to test this arrangement. SPR is generated if a charged particle passes close to a periodic metallic structure, e.g. a grating. The signal has a coherent part which increases its intensity quadratically with the bunch charge if the bunch length is smaller than or comparable to the grating period. Different gratings can be placed below the electron beam to determine the length of the electron bunches. This measurement is non-destructive. The generated THz radiation will be observed with a bolometer cooled down to 4.2K which offers sufficient sensitivity in our regime of operation. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF062 | |
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SUSPF022 |
Generation of Tunable Femtosecond X-Rays from High-Period-Number Resonant Transition Radiation Emitters | |
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Funding: Work supported by the Ministry of Science and Technology, ROC (Taiwan). Femtosecond resonant transition radiation (RTR) in x-ray region can be generated from alternatively stacked multilayer structures when they are driven by relativistic ultrashort electron beams. These structures can be fabricated by coating layer pairs of high and low density materials. By increasing the number of these layer pairs, narrow-band x-ray can be generated. In this report, we present our efforts on the development of a 12 keV femtosecond narrow-band x-ray source by driving high-period-number RTR emitters with the NSRRC photoinjector linac system. Radiation wavelength is tunable by varying the incident angle of the beam. A few tens MeV, ultrashort beam has been available from the photoinjector system via velocity bunching in the rf linac. A 100-period (200 layers) Mo/Si multi-layer emitters with thin substrate have been fabricated. For a 100 pC drive beam, the expected photon yield from such emitter is about 4x104. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK019 | |
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SUSPF023 |
Research of a Locally-round Beam in HEPS Storage Ring Using Solenoids | |
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| "Round beam", that is, a beam with equivalent transverse emittance, is expected for a significant fraction of the beamline users in light sources. We investigate the possibility of reaching round beam in a storage ring, by means of a local exchange of the apparent horizontal and vertical emittance, performed with solenoids in a dedicated insertion line in the storage ring. In this paper, we show that a locally-round beam can be achieved by using solenoid in High Energy Photon Source (HEPS) storage ring, particularly to one of the design having natural emittance of 34.2 pm·rad. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF051 | |
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SUSPF024 |
Setup for Cooled GaAs Cathodes With Increased Charge Lifetime | |
| THPMK100 | use link to access more material from this paper's primary paper code | |
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Funding: DFG (GRK 2128) BMBF (05H15RDRB1) GaAs photocathode lifetime is limited, and to ensure re- liable operation for high power-applications it is necessary to maximize its charge lifetime. By using a cryogenic sub- volume it is expected to improve the local vacuum condi- tions due to cryogenic adsorption of reactive residual gas molecules. Yielding an enhanced lifetime of the negative- electron-affinity surface of the cathode. Furthermore the cooling of the cathode itself ishould allow higher laser power deposition in the material. Introducing an electrostatic bend is expected to reduces the ion-backbombardment on the cath- ode surface. A dedicated set-up is being developed at the Photo-CATCH test facility in Darmstadt, Germany to measure the charac- teristics of such a cryogenic source. This contribution updates the report given at PSTP 2017. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK100 | |
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SUSPF025 |
Study of Secondary Electron Generation and Transport in Diamond | |
| THPML136 | use link to access more material from this paper's primary paper code | |
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| Energetic primary electrons (~ keV) impinging on the diamond film with its both surface under bias field in ~ MV/m, will excite secondary electron (SE) response including SE generation & transport. Although there have been 3D Monte Carlo (MC) simulation to study the two processes, this paper will introduce another method. Based on optical dielectric model, 3D MC simulation was implemented to study the generation process, and SE generation function was obtained by fitting the calculations. Using this function, the diffusion-drift equation of charge carriers (electron and hole) can be solved in 1D for the transport process, and the variation of SE depth distribution with time can be obtained. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML136 | |
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SUSPF027 |
The Role of Electron-Phonon Scattering in Transverse Momentum Conservation in PbTe(111) Photocathodes | |
| TUPMF065 | use link to access more material from this paper's primary paper code | |
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Funding: The U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams. The state of the art in creating high quality electron beams for particle accelerator applications and next generation ultrafast electron diffraction and microscopy involves laser-generated photoemission. A high quality beam requires that electrons emerge from the surface with low mean transverse energy (MTE). Recent density-functional theory calculations by T. Li and W. A. S. [arXiv:1704.00194v1 [physics.acc-ph] (2017)] suggest that PbTe(111) will produce low-MTE photoelectrons due to the low effective electron mass associated with its electronic band structure. Based on this, we measured the distribution of photoelectrons from PbTe(111) and found the MTE to be about 20x larger than expected. To explain the apparent lack of transverse momentum conservation, we carried out many-body photoemission calculations including electron-phonon scattering. Our results are in far better agreement with the experiment, underscoring the importance of electron-phonon scattering in photoemission from PbTe(111), and suggest that cooling could mitigate the phonon effects on the MTE for this material. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF065 | |
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SUSPF028 |
300 kV DC High Voltage Photogun with Inverted Insulator Geometry and CsK2sb Photocathode | |
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Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177 A compact DC high voltage photogun with inverted-insulator geometry was designed, built and operated reliably at 300 kV bias voltage using alkali-antimonide photocathodes. This presentation describes key electrostatic design features of the photogun with accompanying emittance measurements obtained across the entire photocathode surface that speak to field non-uniformity within the cathode/anode gap. A summary of initial photocathode lifetime measurements at beam currents up to 4.5 mA is also presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK110 | |
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SUSPF029 |
On-Axis Beam Accumulation Based on a Triple-Frequency RF System for Diffraction-Limited Storage Rings | |
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| Since the multi-bend achromats have been applied to lattice design in the future light source to achieve ultralow emittance, strong sextupoles and concomitant nonlinearities restrict its performance to a certain extent. The empirical understanding is the exclusion of conventional off-axis injection scheme on these light sources. In this paper, we will present a new on-axis beam accumulation scheme, which is based on the triple-frequency RF system. By means of delicate superposition of RF voltage with fundamental and two other harmonic frequencies, a commodious and steady main bucket is able to be formed. The electron bunch from the injector will be kicked into the main bucket on-axis with a reasonable time offset to the circular bunch, and this process may make the minimal disturbance to the experiment users while operating on the top-up mode. The application of this scheme to the High Energy Photon Source (HEPS) will be discussed in the paper, corresponding simulation results are also presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMF048 | |
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SUSPF030 |
Inverse Free Electron Laser Separatrix Crossing for Energy Gain and Stability | |
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| The laser wakefield accelerator (LWFA) has been proposed as a driver for next generation compact light sources. However, the beams produced by LWFA's typically exhibit correlated energy spread and energy jitter too large to drive the Free Electron Laser instability. We present here a novel scheme whereby using a highly non-linear strongly tapered undulator interaction directly after the LWFA we are able to trap and accelerate a large fraction of charge in the moving Inverse Free Electron Laser ponderomotive bucket. The final correlated energy spread and output energy are determined by the final bucket height and central energy of the ponderomotive bucket which are both determined by the stagnant undulator parameters, resulting in a significant decrease in the normalized energy spread (< 1%) and output energy jitter (< 1%). This interaction is treated both analytically and numerically. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK028 | |
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SUSPF031 |
Advances in the Sirius Delta-Type Undulator Project | |
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| The Delta undulator is a compact adjustable-phase insertion device that provides full light polarization control. Five undulators of this type will be installed in the initial operation phase of Sirius, the new 4th generation synchrotron light source that is being built by the Brazilian Synchrotron Light Laboratory (LNLS). In this work we present the recent advances in the development of Sirius Delta-type undulator, the studies of the effects of this device in the storage ring beam dynamics and assembly and measurements strategies. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPMK003 | |
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SUSPF032 |
Optical Cavity R&D for Laser-Electron Interaction Applications | |
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| Laser-electron Inverse Compton Scattering X-ray source based on optical enhancement cavity is expected to produce higher-flux and better-quality X-rays than conventional sources, in addition, to become more compact, much cheaper than Free Electron Laser and Synchrotron Radiation. One X-ray source named ThomX is under construction at LAL, France. An electron storage ring with 50 MeV, 16.7 MHz electron beam will collide with a few picosecond pulsed laser to produce 1013 photons per second. A prototype cavity with a high finesse (F=25,100) in the picosecond regime is used to perform R & D for ThomX. We obtained 380 kW power stored in the optical cavity and mode instabilities were observed. The EOM-based frequency modulation to measure the finesse, the influence of dust on finesse, high-power experiments and other related issues are mentioned briefly. We will also describe the TTX2 (Tsinghua Thomson Scattering X-ray source) at Tsinghua University which is in design process. TTX2 prefers using an electron storage ring and an optical cavity in order to get high X-ray flux. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK115 | |
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SUSPF033 |
A Non-parameteric Density Estimation Approach to Measuring Beam Cooling in MICE | |
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| The goal of the international Muon Ionization Cooling Experiment (MICE) is to demonstrate muon beam ionization cooling for the first time. It constitutes a key part of the R&D towards a future neutrino factory or muon collider. The intended MICE precision requires development of analysis tools that can account for any effects (e.g., nonlinearities) which may lead to inaccurate cooling measurements. Non-parametric density estimation techniques, in particular, kernel density estimation (KDE), allow very precise calculations of the muon beam phase-space density and its increase as a result of cooling. In this study, these density estimation techniques and their application to measuring the reduction in muon beam phase-space volume and amplitude in MICE are investigated. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML063 | |
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SUSPF034 |
Design of a High Gradient 60 GHz Dielectric Accelerating Structure | |
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| RF breakdown are the main limitation for the application of high gradient structures. Higher frequencies and shorter pulse length benefit the design of accelerating structure for the breakdown threshold of surface field is Es=f1/2 τ-1/4. Power source which generates very short V-band pulse with nearly hundred megawatt is now available. The paper presents the analysis of a V-band dielectric acceleration structure and power source. Future plan about RF transmission and power coupling of the whole structure will be discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML091 | |
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SUSPF035 |
Modeling of Self-Modulated Laser Wakefield Acceleration Driven by Sub-Terawatt Laser Pulses | |
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Funding: This work has been supported by the Ministry of Science and Technology in Taiwan by grant MOST104-2112-M-008-013-MY3 and by grant MOST105-2112-M-007-036-MY3. Laser wakefield accelerator (LWFA) can be achieved in a scheme in which a sub-terawatt (TW) laser pulse is introduced into a thin, high-density target*. As a result, the self-focusing and the self-modulation can greatly enhance the peak intensity of the laser pulse capable of exciting a nonlinear plasma wave to accelerate electrons. A particle-in-cell model was developed to study the sub-TW LWFA, in which a 0.6-TW laser pulse is injected into a hydrogen gas cell with a flat-top density profile. In addition to using 800-nm laser pulses, laser pulses of 1030 nm were used in simulations as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems**. Process of the electron injection is complicated in such a high-density plasma; however, the simulation results show that the appropriate injection and acceleration of electrons can be achieved by optimizing the length of the gas cell. When a 340-micrometer long gas cell is introduced, energetic electrons (> 1 MeV) are produced with a relatively low emittance of 3.5 pi-mm-mrad and a total charge of 0.32 nC accordingly. * A. J. Goers et al., Phys. Rev. Lett. 115, 194802 (2015). ** E. Kaksis et al., Opt. Express 24, 25, 28915 (2016). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML018 | |
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SUSPF036 |
A Metamaterial Wagon Wheel Structure for Wakefield Acceleration by Reversed Cherenkov Radiation | |
| THPML014 | use link to access more material from this paper's primary paper code | |
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Funding: U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0015566 and the U.S. Department of Energy Office of Science under Contract No. DE-AC02-06CH11357 We present the design and experimental operation on an X-band metamaterial (MTM) wagon wheel structure for wakefield acceleration. The structure was designed and fabricated at MIT, and tested at the Argonne Wakefield Accelerator (AWA) laboratory at Argonne National Lab. The MTM wagon wheel structure is an all-metal periodic structure at 11.4 GHz. The fundamental TM mode has a negative group velocity, so when an electron beam travels through, energy is extracted from the beam by reversed Cherenkov radiation, which was verified in the experiment. Single bunches up to 45 nC were sent through the structure with a beam aperture of 6 mm and generated microwave power up to 25 MW in a 2 ns pulse, in agreement with both the analytical wakefield theory and the numerical CST simulations. Two bunches with a total charge of 85 nC generated 80 MW of microwave power. The structure is scalable to a power extractor of over 1 GW by increasing the structure length from 8 cm to 22 cm. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML014 | |
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SUSPF037 |
Simulation of Phase-Dependent Transverse Focusing in Dielectric Laser Accelerator Based Lattices | |
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Funding: Gordon and Betty Moore Foundation. Grant GBMF4744 The Accelerator on a CHip International Program (ACHIP) funded by the Gordon and Betty Moore Foundation aims to demonstrate a prototype of a fully integrated accelerator on a microchip based on laser-driven dielectric structures until 2021. Such an accelerator on a chip needs all components known from classical accelerators. This includes an electron source, accelerating structures and transverse focusing arrangements. Since the period of the accelerating field is connected to the drive laser wavelength of typically a few microns, not only longitudinal but also transverse effects are strongly phase-dependent even for few femtosecond long bunches. If both the accelerating and focusing elements are DLA-based, this needs to be taken into account. In this work we study in detail the implications of a phase-dependent focusing lattice on the evolution of the transverse phase space of a transported bunch. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML038 | |
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SUSPF038 |
Using Deep Reinforcement Learning for Designing Sub-Relativistic Electron Linac | |
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| Generally, when designing an accelerator device, the design is based on the experience and knowledge of the designer. Most of the design process proceeds by chang-ing the parameters and looking at the trends and then determining the optimal values. This process is time-consuming and tedious. In order to efficiently perform this tedious design process, a method using an optimization algorithm is used. Recently, many people started to get interested in the algorithm used in AlphaGo, which became famous when it won the professional Go player developed by google The algorithm used in AlphaGo is an algorithm called reinforcement learning that learns how to get optimal reward in various states by moving around a solution space that the agent has not told beforehand. In this paper, we will discuss about designing an particle accelerator by applying Deep Q-network algorithm which is one kind of deep learning reinforcement learning. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML032 | |
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SUSPF040 |
Staged Two Beam Acceleration Beam Line Design for the AWA Facility | |
| TUPML064 | use link to access more material from this paper's primary paper code | |
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Funding: This work is funded by the DOE Office of Science, grant no. DE-SC0015479, and contract No. DE-AC02- 06CH11357. Two beam acceleration is a candidate for future high energy physics machines and FEL user facilities. This scheme consists of two independent electron beam lines operating synchronously. High-charge, 70 MeV drive bunch trains are injected from the RF photo-injector into decelerating structures to generate a few hundred of MW of RF power. This RF power is transferred through an RF waveguide to accelerating structures that are used to accelerate the witness beam. Staging refers to the sequential acceleration (energy gain) in two or more structures on the witness beam line. A kicker was incorporated on the drive beam line to accomplish a modular design so that each accelerating structure can be independently powered by a separate drive beam. Simulations were performed in OPAL-T to model the two beam lines. Beam sizes at the center of the structures was minimized to ensure good charge transmission. The resulting design will be the basis for proof of principle experiments that will take place at the Argonne Wakefield Accelerator (AWA) facility. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML064 | |
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SUSPF041 |
A Beamline Design to Transport Laser Wakefield Electrons to a Transverse Gradient Undulator | |
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Funding: This work was supported by the UK Science and Technology Facilities Council, Grant No. ST/G008248/1. The Cockcroft Beamline is to be installed at the Scottish Centre for the Application of Plasma-based Accelerators (SCAPA). The beamline is designed to transport 1 GeV electrons from a laser wakefield acceleration (LWFA) source to a pair of transverse gradient undulators. The project aims to produce X-ray undulator radiation in the first phase and free-electron laser (FEL) radiation in the second phase. The total beamline will be less than 23 m long, thus the Cockcroft Beamline has the potential to be the UK's first compact X-ray FEL. Here we present the main features of the beamline design. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML021 | |
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SUSPF042 |
Amplitude Enhancement of the Self-Modulated Plasma Wakefields | |
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| Seeded Self-modulation (SSM) has been demonstrated to transform a long proton bunch into many equidistant micro-bunches (e.g., the AWAKE case), which then resonantly excite strong wakefields. However, the wakefields in a uniform plasma suffer from a quick amplitude drop after reaching the peak. This is caused by a significant decrease of the wake phase velocity during self-modulation. A large number of protons slip out of focusing and decelerating regions and get lost, and thus cannot contribute to the wakefield growth. Previously suggested solutions incorporate a sharp or a linear plasma longitudinal density increase which can compensate the backward phase shift and therefore enhance the wakefields. In this paper, we propose a new plasma density profile, which can further boost the wakefield amplitude by 30%. More importantly, almost 24% of protons initially located along one plasma period survive in a micro-bunch after modulation. The underlying physics is discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML023 | |
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SUSPF043 |
A Start to End Simulation of the Laser Plasma Wakefield Acceleration Experiment at ESCULAP | |
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| We present a start to end (s2e) simulation of the Laserplasma Wake Field Accelerator (LPWA) foreseen as the ESCULAP project. We use a photo injector to produce a 5 MeV 10 pC electron bunch with a duration of 1 ps RMS, it is boosted to 10 MeV by a S-band cavity and then compressed to 74 fs RMS (30 fs FWHM) by a magnetic compression chicane (dogleg). After the dogleg, a quadrupole doublet and a triplet are utilized to match the Twiss parameters before injecting into the subsequent plasma wakefield. A 40 TW laser is used to excite plasma wakefield in the 10 cm plasma cell. An optimized configuration has been determined yielding at the plasma exit an electron beam at 180 MeV with energy spread of 4.2%, an angular divergence of 0.6 mrad and a duration of 4 fs. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML079 | |
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SUSPF044 |
Excitation of Plasma Wave by Lasers Beating in a Collisional and Mild-Relativistic Plasma | |
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Funding: Work supported by Department of Science and Technology (DST), Government of India. Excitation of plasma wave by two lasers beating in a collisional dominated relativistic plasma is investigated. We study the energy exchange between a plasma wave and two co-propagating lasers in plasma including the effect of relativistic mass change and electron-ion collisions. Two lasers, having frequency difference equal to the plasma frequency, excite a plasma beat wave resonantly by the ponderomotive force, which obeys the energy and momentum conservation*. The relativistic effect and the electron-ion collision both contribute in energy exchange between the interacting waves in the beat-wave acceleration mechanism. Our study shows that the initial phase difference between interacting waves generates a phase mismatch between lasers and plasma wave, which alters the rate of amplitude variations of the interacting waves and, hence, affects the energy exchange between the interacting waves**. This study may be crucial to design a compact plasma accelerator in low-intensity regime***. *T. Tajima, and J. Dawson, Phys. Rev.Lett. 43, 267(1979) **D. N. Gupta, M. S. Hur, and H. Suk, J.Appl. Phys. 100, 103101 (2006) ***M. Kaur and D. N. Gupta, EuroPhysics letter 116, 35001 (2016). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML052 | |
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SUSPF045 |
The Design and Construction of a Novel Dual-Mode Dual-Frequency Linac Design | |
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| One promising approach in boosting accelerators efficiency is dual-mode simultaneous operation. In our work, the topic of dual-mode acceleration is studied from a wider perspective with new approaches and tools. We present a new type of accelerator structures that operates simultaneously with two modes and two frequencies. The frequencies are not constrained to be harmonically related, but rather have a common sub-harmonic. These designs will utilize a newly developed parallel-feeding network that feeds each individual accelerating cell independently using a distributed feeding network. As a result, the design problem converges to a single-cell design with identical cells. The cells are designed for maximum efficiency using new geometrical optimization that utilizes nonuniform rational B-spline (NURBS) with a series of control points. We will present a study on the topic for S-band simultaneous operation with C-band or X-band. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK048 | |
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SUSPF048 |
Laser Ablation Plasma with Solenoid Field Confinement | |
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Funding: This work is supported by National Natural Science Foundation of China (Grant Nos. 11722547, 11605263 and 11505257) and West Light Foundation of The Chi-nese Academy of Sciences (Grant Nos. 29Y637020) A Laser Ion Source (LIS) can produce high charge state and high intensity ion beams (~emA), especially refracto-ry metallic ion beams, which makes it a promising candi-date as an ion source for heavy ion cancer therapy facili-ties and future accelerator complexes, where pulsed high intensity and high charged heavy ion beams are required. However, it is difficult for LIS to obtain a long pulse width while ensuring high current intensity, thus limiting the application of LIS. To solve the conflict, magnetic fields are proposed to confine the expansion of the laser produced plasma. With a solenoid along the normal direc-tion to the target surface, the lateral adiabatic expansion of the laser ablation plasma is suppressed which extends the pulse width of the ion beam effectively. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML070 | |
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SUSPF049 |
Long Lifetime Spin-Polarized GaAs Photocathode Activated by Cs2Te | |
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Funding: This work was supported by the Department of Energy Grant Nos. DE-SC0016203 and NSF PHY-1461111. High intensity and highly spin-polarized electron source is of great interest to the next generation Electron Ion Colliders. GaAs prepared by the standard activation method, which is the most widely used spin-polarized photocathode, is notorious for its vacuum sensitivity and short operational lifetime. To improve the lifetime of GaAs photocathodes, we activated GaAs by Cs2Te, a material well known for its robustness. We confirmed the Cs2Te layer forms negative electron affinity on GaAs with a factor of 5 improvement in lifetime. Furthermore, the new activation method had no adverse effect on spin-polarization. Considering Cs2Te forms much thicker activation layer (~ 2 nm) compared to the standard activation layer (~ monolayer), our results trigger a paradigm shift on new activation methods with other robust materials that were avoided for their thickness. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML025 | |
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SUSPF050 |
Study of Mean Transverse Energy of (N)UNCD with Tunable Laser Source | |
| TUPML061 | use link to access more material from this paper's primary paper code | |
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Funding: NSF grant No. NSF-1739150, DOE SBIR program grant No. DE-SC0013145, NSF grant No. PHYS-1535279, DOE Contract No. DE-AC02-06CH11357. There is a strong motivation to develop and understand novel materials with the potential to be utilized as photocathodes, as these could have desirable photoemission properties for research and industrial applications. Nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) photocathodes have potential to become a material of choice for photocathode applications*. (N)UNCD has high quantum efficiency when processed in hydrogen plasma*, low surface roughness, and high electron conductivity through the bulk**. The mean transverse energy (MTE) was calculated for (N)UNCD thin films using the double-solenoid scan method. (N)UNCD thin film with thickness of 160nm was deposited on highly-doped silicon substrate. Studies of the MTE of a (N)UNCD sample were done using a tunable laser source with photon energies of 3.56 eV to 5.26 eV. These results are presented. * K.J. Pérez Quintero et al., Appl. Phys. Lett. 105, 123103 (2014). ** S. Bhattacharyya et al., Appl. Phys. Lett. 79, 1441 (2001) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML061 | |
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SUSPF051 |
Design Studies of an S-Band Multipacting Electron Gun | |
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| A multipacting electron gun (MEG) is a micro-pulse electron source based on secondary electron emission in a resonant microwave cavity structure for the generation of low emittance electron bunches with high repetition rate. By theoretical simulations a suitable radio-frequency gun design at 3 GHz is established, simultaneously meeting the demands of bunch production and amplification process as well as including the effects of space charge and beam loading for the evolution of a stable beam. In this contribution we show detailed simulation studies of the impact of important design parameters like mechanical dimensions and choice of material on the average output current, which is in the order of several mA. For the experimental investigation a test setup is under construction, which may demonstrate the application of MEG's as a serious alternative or addition to commonly used electron sources like thermionic and photocathodes. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML054 | |
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SUSPF052 |
Electron Cloud Build Up for LHC Sawtooth Vacuum Chamber | |
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| At high proton-beam energies, beam-induced synchrotron radiation is an important source of heating, of beam-related vacuum pressure increase, and of primary photoelectrons, which can give rise to an electron cloud. For the arcs of LHC a sawtooth pattern had been imprinted on the horizontally outward side of the vacuum chamber in order to locally absorb synchrotron radiation photons without dispersing them all around the chamber. Using the combination of the codes Synrad3D and PyCLOUD we examine the effect of realistic absorption distributions with and without sawtooth on the build up of electron clouds. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF030 | |
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SUSPF053 |
Technical Workings of the 6D Phase Measurement at SNS | |
| TUPAL044 | use link to access more material from this paper's primary paper code | |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. This work has been partially supported by NSF Accelerator Science grant 1535312. The Beam Test Facility (BTF) is a functional duplicate of the Spallation Neutron Source (SNS) frontend with a 2.5 MeV beam on which the first six-dimensional phase space measurement has been completed. This presentation will show the technical underpinnings involved in performing the 6D scan with the BTF. The first part will examine the diagnostic setup involving apertures, a screen, and a bunch shape monitor and how the integrated system functions. The next part will cover the scan logic used in the software. The last part will briefly discuss ongoing efforts to analyze 6D measurements and identify correlations. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL044 | |
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SUSPF054 |
Progress Work on a CW Deuteron RFQ with Magnetic Coupling Windows | |
| TUPAL050 | use link to access more material from this paper's primary paper code | |
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Funding: This work was supported by the National Basic Research Program of China (Grant No. 2014CB845503). A new 162.5 MHz RFQ has been built for a joint 973 project between Peking University (PKU) and Institute of Modern Physics (IMP). It is designed to deliver 50-mA deuteron beams to 1 MeV in CW mode, with an inter-voltage of 60 kV and a length of 1.809 m. Due to its window-type structure, the RFQ has compact cross-section, sufficient mode separation and high specific shunt impedance. It consists of two segments fabricated and installed at IMP. The assembling error of the cavity is less than 0.05 mm. The RF measurements show good electrical properties of the resonant cavity with a measured unloaded quality factor equal to 96.4% of the simulated value. After tuning, we obtained the nominal frequency and field unbalance within 1.0%. Preparation of high-power test of this RFQ is underway. This paper will cover the fabrication details and RF measurements, as well as the progress of high-power test. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL050 | |
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SUSPF055 |
Studying a Prototype of Dual-beam Drift Tube Linac | |
| TUPAL009 | use link to access more material from this paper's primary paper code | |
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For generating high-intensity ion beams from linear ac-celerators, a multi-beam acceleration method which in-volves multiple accelerating beams to suppress the defo-cusing force from space charge effects, then integrating these beams by a beam funneling system, has been pro-posed. An Inter-digital H-mode (IH) two-beam type radio frequency quadrupole (RFQ) with accelerating 108mA (54mA/channel×2) carbon ion from 5 to 60 keV/ u and an IH four-beam RFQ with accelerating 160.8mA (40.2mA/channel×4) carbon ion from 3.6 to 41.6 keV/u had been successfully designed for low energy heavy ion acceleration [1]. In order to demonstrate that an IH dual-beam drift tube linac (DB-DTL) is suitable for high-intensity heavy ion beam acceleration in middle energy region, we has been developing a DB-DTL prototype by using three dimensional electromagnetic CST MicroWave Studio (MWS) and using particles tracking Pi Mode Linac Orbit Calculation (PiMLOC) [2-3]. According to the simulation results, the beam dynamics design and elec-tromagnetic design will be presented in this paper.
* Shota. Iketa et al., Nucl. Instr. and Meth. in Phys. Res. B.239-243 (2017). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL009 | |
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SUSPF056 |
Conceptual Design of a Drift Tube LINAC for Proton Therapy | |
| TUPAL073 | use link to access more material from this paper's primary paper code | |
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Funding: National Key Research and Development Program of China (grant number 2016YFC0105408) The conceptual design of an Alvarez-type Drift Tube Linac for one proton therapy facility is described in this paper. The design optimization of the Drift Tube Linac is carried out in the principle of adopting domestic mature technologies and cost control. The error study of the Drift Tube Linac is also given in this paper. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL073 | |
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SUSPF057 |
Design and Fabrication of Hybrid RFQ Prototype | |
| TUPAL012 | use link to access more material from this paper's primary paper code | |
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| Hybrid RFQ is proposed as a potential good choice at the low-energy range of linear accelerator. The complexi-ty of mechanical design and difficulty of fabrication are part of reasons impeding application of it and similar structures. In order to explore the practicable structure and research on RF parameters of this accelerating struc-ture, an aluminium prototype is developed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAL012 | |
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SUSPF058 |
Commissioning of the Diagnostic Beam Line for the Muon RF Acceleration with H− Ion Beam Derived from the Ultraviolet Light | |
| TUPAK016 | use link to access more material from this paper's primary paper code | |
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Funding: This work is supported by JSPS KAKENHI Grant Numbers JP15H03666, JP16H03987, and JP16J07784. A muon LINAC is under development for a precise measurement of muon g-2 / EDM at J-PARC. We conducted an experiment of a muon RF acceleration on October and December 2017. The surface muon beam is irradiated to a metal degrader to generate slow negative muonium. The slow negative muoniums are accelerated to 90 keV with an electrostatic accelerator and an RFQ. Prior to muon RF acceleration, we conducted a commissioning of the diagnostic beam line consisting of two quadrupole magnets and a bending magnet. The ultraviolet light is irradiated to an aluminum foil and H− ion is generated. It simulates a negative muonium and is accelerated with an electrostatic accelerator. This system allowed us to check operation for the diagnostic beam line, which is essential task for transportation and momentum selection of the negative muonium. In this paper, I would like to report the performance evaluation of the diagnostic beam line by H− ions. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAK016 | |
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SUSPF060 |
Investigating Beam Loss Reduction with Octupoles During Slow Extraction in the CERN SPS | |
| TUPAF051 | use link to access more material from this paper's primary paper code | |
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| Several different methods for reducing beam loss during resonant slow extraction at the CERN Super Proton Synchrotron (SPS) are being studied. One of these methods is the use of multipoles to manipulate the separatrices in order to reduce the fraction of protons hitting the thin wires of the electrostatic extraction septum (ES). In this paper the potential of using octupoles for this purpose is explored. Beam dynamics simulations using both a simplified model and full 6D tracking in MAD-X are presented. The performance reach of such a concept at the SPS is evaluated and the potential of future machine development studies using the octupoles already installed is discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPAF051 | |
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SUSPF061 |
The Influence of Higher Order Multipoles of IR Magnets on Luminosity for SuperKEKB | |
| THPAK099 | use link to access more material from this paper's primary paper code | |
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| SuperKEKB is an electron-positron circular collider upgraded from KEKB. To reach higher luminosity, values of beta are extremely small at Interaction Point. Although magnets in interaction region have a very strong focusing effect, they make a large disturbance to beams. Higher order multipoles and their skew components of magnetic fields of IR magnets are located at a very high beta section with pi/2 phase difference from IP. These multipoles can give critical effect to beam dynamics at interaction point and reduce luminosity on SuperKEKB design. In this study, we calculated beam dynamics for effect of skew components for multipole magnet, and estimated the influence on luminosity by them. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK099 | |
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SUSPF062 |
Reduction of Coherent Betatron Oscillations Using RF Electric Fields in the Fermilab Muon g-2 Experiment | |
| THPAF010 | use link to access more material from this paper's primary paper code | |
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| The Fermilab Muon g-2 experiment aims to measure the muon anomalous magnetic moment with a 140 parts-per-billion precision to investigate the greater than 3 standard deviation difference between the Standard Model prediction and the previous measurement by the BNL Muon g-2 experiment. The coherent betatron oscillation (CBO) beam effects must be corrected for in the decay-positron time spectra fits used in high precision muon storage ring based anomalous magnetic moment measurements. This MC simulation study indicates that the application of radio frequency (RF) electric fields to the muon storage ring beam can reduce the CBO amplitude by up to a factor of 10, as well to increase the symmetry of the beam phase space. This is achieved by correcting the mismatched oscillation phases between the high and low momentum muon populations by modulating the muon beam betatron oscillation frequencies with off-resonance RF fields. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF010 | |
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SUSPF063 |
Optics Measurements in Storage Rings Based on Simultaneous 3-Dimensional Beam Excitation | |
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| Optics measurements in storage rings usually employ excitation in both transverse directions. This needs to be repeated at several different beam energies and is time-consuming. In this paper, we develop a new optics measurement technique, which excites the beam in all three spatial dimensions simultaneously. It allows measuring the linear optics and chromatic properties at the same time, leading to speed up of the optics measurements. The measurement method has been successfully demonstrated in the LHC using AC-dipoles and RF frequency modulation. Analysis methods have been derived for the 3-dimensional beam excitation case. We quantify the resolution of the measured optical quantities. The first results suggest that the added complexity does not deteriorate the resolution of the linear optics measurement. In the future, this method can serve as an operational tool to check the optics or even to correct it. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF046 | |
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SUSPF066 |
Initial Tests of Nonlinear Quasi-Integrable Optics at the University of Maryland Electron Ring | |
| THPAK141 | use link to access more material from this paper's primary paper code | |
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Funding: Funding for this project and travel is provided by DOE-HEP, NSF GRFP and NSF Accelerator Science Program. An octupole channel has been inserted into the University of Maryland Electron Ring (UMER), in order to investigate the mitigation of destructive resonances as a novel approach in high-intensity beam transport. The individual octupole magnets have been characterized using our in-house 3-dimensional magnet mapping stage, with a measured gradient of 51.6 ± 1.5 T/m3/A. A single section (20°) of an 18-cell FODO lattice has been replaced by a longitudinally-varying octupole channel constructed from seven flexible printed circuits (PCBs). We present the design of the channel and preliminary beam based measurements on the ring. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK141 | |
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SUSPF067 |
Beam-Based Sextupolar Nonlinearity Mapping in CESR | |
| THPAK137 | use link to access more material from this paper's primary paper code | |
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Funding: Work supported by the U.S. National Science Foundation under Award No. PHY-1549132, the Center for Bright Beams In order to maintain beam quality during transport through a storage ring, sextupole magnets are used to make chromatic corrections, but necessarily introduce deleterious effects such as nonlinear resonances and reduced dynamic aperture. Implementing intricate sextupole distributions to mitigate these effects will rely on precision beam-based measurement of the applied sextupole distribution. In this work, we generalize previous sextupole mapping techniques by using resonant phase-locked excitation of the beam at the Cornell Electron Storage Ring (CESR), which accounts for variations in the normal mode tunes on a turn by turn basis. The methods presented here are applied to simulation and actual turn by turn data in CESR for both simplified and realistic sextupole distributions. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK137 | |
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SUSPF069 |
Tuning Low-Current Beam for Nonlinear Quasi-Integrable Optics Experiments at the University of Maryland Electron Ring | |
| THPAK143 | use link to access more material from this paper's primary paper code | |
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Funding: Travel was supported by the NSF, the APS DPB, and TRIUMF. Funding for the work was provided through DOE-HEP Award DESC0010301, NSF Award PHY1414681 and the NSF GRFP program. Design of accelerator lattices with nonlinear integrable optics is a novel approach to suppress transverse resonances and may be crucial for enabling low-loss high-intensity beam transport. Lattices with large amplitude-dependent tune spreads, driven by strong nonlinear magnet inserts, have reduced response to resonant driving perturbations [*]. This paper describes preparations for tests of a quasi-integrable octupole lattice at the University of Maryland Electron Ring (UMER). The planned tests employ a low-current highemittance beam with low space charge tune shift (∼ 0.005) to probe the dynamics of a lattice with large external tune spread (∼ 0.26). * V. Danilov and S. Nagaitsev, Nonlinear accelerator lattices with one and two analytic invariants, PRSTAB, 13, 084002, 2010. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK143 | |
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SUSPF070 |
A Benchmark Study of a High Order Symplectic Integration Method With Only Positive Steps | |
| THPAF060 | use link to access more material from this paper's primary paper code | |
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| The symplectic integrators CSABA & CSBAB are used in order to calculate single particles dynamics in accelerators and storage rings. These integrators include only forward drift steps while being highly accurate. Their efficiency to describe various optical and dynamical quantities for main magnetic elements and non-linear lattices is calculated and compared with the efficiency of the splitting methods used in MAD-X - PTC. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF060 | |
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SUSPF071 |
Multi-Objective Optimization of an SRF Photoinjector with Booster Section for High Brightness Beam Performance | |
| THPAF087 | use link to access more material from this paper's primary paper code | |
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| Several future accelerator projects, light sources and user experiments require high brightness electron beams. SRF photoinjectors operating in continuous-wave (cw) mode hold the potential to serve as an electron source generating beams of high average brightness and short bunch lengths. Different operation and design parameters of the SRF photoinjector impact the beam dynamics and thus the beam brightness. A universal multi-objective optimization program based on a genetic algorithm was developed to extract optimum gun parameter settings from Pareto-optimum solutions. After getting the first optimum results, the photoinjector is supplemented with a booster section downstream. The new optimization results are presented. Further, the optimization program is applied to evaluate the impact of the field flatness of the gun cavity on the high brightness performance. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF087 | |
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SUSPF072 |
A 2D Steady-State Space Charge Solver for Azimuthally Symmetric Problems of Arbitrary Degree | |
| THPAK086 | use link to access more material from this paper's primary paper code | |
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| Correctly and rapidly simulating the steady-state interaction between particle beams and electromagnetic fields is crucial to the design and optimization of accelerator and radiofrequency (RF) source components. Iteratively solving for the self-consistent interaction between particles and fields can prove challenging and highly susceptible to numerical noise and mesh induced instabilities. We present herein two new approaches to solving the self-consistent trajectories of particles in the presence of external and self fields. The first method reformulates the integrated self field contribution as a path integral. The second method uses a hybrid Eulerian framework and produces an interpolated continuous current density, resulting in 1-2 orders of magnitude fewer particles required to obtain an accurate solution. We conclude with benchmarking results which show this method is as accurate as state of the art PIC solvers, while running 80-120X faster. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK086 | |
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SUSPF073 |
Beam-Loading Transients and Bunch Shape in the Operation of Passive Harmonic Cavities in the ALS-U | |
| THPAK037 | use link to access more material from this paper's primary paper code | |
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| The ALS-U is a major upgrade of the LBNL ALS to a diffraction limited light source. The current plan is to replace all the vacuum and magnet components while retaining the existing 500 MHz main and third-harmonic, passively operated, rf cavities, but replacement of the existing rf cavities is also being considered. A new feature, is represented by beam-loading transients associated with a beam consisting of 11 bunch trains separated by 10 ns gaps as needed to enable on-axis swap-out injection. In this paper we study these transients and the associated bunch-to-bunch phase, length, and profile variations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK037 | |
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SUSPF074 |
Measuring the Coupling Impedance of Vacuum Components for the Advanced Photon Source Upgrade Using a Goubau Line | |
| THPAK005 | use link to access more material from this paper's primary paper code | |
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| The Planned upgrade of the Advanced Photon Source to a multi-bend achromat (MBA) will increase the x-ray brightness by two to three orders of magnitude. Storing such an intense beam stably inside the narrow gap vacuum chambers requires sophisticated and appropriately designed rf-components that helps to minimize rf heating and collective instabilities associated with the impedance of these small-aperture vacuum components. As part of this effort, my research focuses on impedance measurement and simulation of various MBA vacuum components. In this paper, we briefly introduce the novel Goubau line (G-line) test fixture for the impedance measurement, at first, and then present our measurements data along with simulations with simulations for various vacuum components designed for the APS Upgrade. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK005 | |
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SUSPF075 |
A Multi-Physics Approach to Simulate the RF Heating 3D Power Map Induced by the Proton Beam in a Beam Intercepting Device | |
| THPAK093 | use link to access more material from this paper's primary paper code | |
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| The project High Luminosity Large Hadron Collider (HL- LHC) calls for a streaking beam intensity and brightness in the LHC machine. In such a scenario, beam-environment electromagnetic interactions are a crucial topic: they could lead to uneven power deposition in machine equipment. The resulting irregular temperature distribution would gener- ates local thermal gradients, this would create mechanical stresses which could lead to cracks and premature failure of accelerator devices. This work presents a method to study this phenomenon by means of coupled electro-thermo- mechanical simulations. Further, examples of applications on real HL-LHC devices is also discussed. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK093 | |
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SUSPF076 |
Single Bunch Instabilities in FCC-ee | |
| THPAK052 | use link to access more material from this paper's primary paper code | |
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| FCC-ee is a high luminosity lepton collider with a centre-of-mass energy from 91 to 365 GeV. Due to the machine parameters and pipe dimensions, collective effects due to electromagnetic fields produced by the interaction of the beam with the vacuum chamber can be one of the main limitations to the machine performance. In this frame, an impedance model is required to analyze these instabilities and to find possible solutions for their mitigation. This paper will present the contributions of specific machine components to the total impedance budget and their effects on the beam stability. Single bunch instability thresholds will be estimated in both transverse and longitudinal planes. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK052 | |
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SUSPF077 |
Pyroelectric Detection of Coherent Radiation on the CLARA Phase 1 Beamline | |
| THPAK140 | use link to access more material from this paper's primary paper code | |
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| The impacts of coherent synchrotron radiation (CSR) and space charge in the bunch compressor section of the CLARA Free Electron Laser (FEL) are expected to be significant, given the relatively high charge and short bunch lengths expected. The General Particle Tracer (GPT) code allows for the modelling of these effects in tandem, presenting an opportunity to more reliably estimate their effects on the CLARA beam. To provide confidence in future studies using GPT, a benchmarking study on the CLARA Phase 1 beamline is presented alongside relevant simulations. This study will make use of pyroelectric detectors to measure the emitted coherent power of the CLARA beam as it passes through a dispersive section whilst varying the chirp imparted on the bunches longitudinal phase space (LPS). Simulations presented demonstrate the viability of such a study, with energies between ∼ 10-100 nJ per pulse expected to be incident upon the detector face. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK140 | |
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SUSPF078 |
Beam Breakup Studies for the 4-Pass Cornell-Brookhaven Energy Recovery Linac Test Accelertor | |
| THPAF022 | use link to access more material from this paper's primary paper code | |
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| Cornell University and Brookhaven National Laboratory are currently designing the Cornell-BNL ERL-FFAG Test Accelerator (CBETA). To be built at Cornell Wilson Lab, CBETA utilizes the existing ERL injector and main linac cryomodule (MLC). As the electron bunches pass through the MLC cavities, higher order modes (HOMs) fields are excited. The recirculating bunches interact with the HOMs, which can give rise to beam-breakup instability (BBU). We would present simulation results on how BBU limits the maximum achievable current, and potential ways to improve the threshold current. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF022 | |
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SUSPF079 |
Coupled Bunch Instability from JLEIC Crab Cavity Higher Order Modes | |
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| Particle bunches traveling in a ring can excite wakefields inside any radio-frequency element present. These electromagnetic modes can resonate long enough and interact with subsequent passing bunches. A coherent oscillation between bunches can quickly become an instability and needs to be addressed. The Jefferson Lab electron ion collider has a large 50 mrad crossing angle and thus relies on bunch crabbing to achieve high luminosity. Bunch crabbing is done with compact superconducting rf dipole cavities. We study coupled bunch oscillations driven by the higher order modes of multicell RFD crab cavities under study for JLEIC, we calculate the instability growth time assuming a symmetric beam spectrum, identify the HOMs driving the instability and discuss mitigation measures. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK070 | |
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SUSPF080 |
A new method to measure the Beta function in a Paul trap | |
| THPAK024 | use link to access more material from this paper's primary paper code | |
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| The Simulator of Particle Orbit Dynamics (S-POD) is a linear Paul trap at Hiroshima University, Japan, used to study beam physics. S-POD has so far been used to study resonances in high intensity beams, predominantly using a simple alternating gradient lattice configuration. Recently a similar apparatus, the Intense Beam Experiment (IBEX), has been constructed at the Rutherford Appleton Lab in the UK. To use either of these experiments to study beam dynamics in more complex lattice configurations in the future further diagnostic techniques must be developed for Paul traps. Here we describe a new method to measure the beta function and emittance at a given time in a Paul trap. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK024 | |
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SUSPF081 |
Resonance Identification Studies at the CERN PS | |
| THPAK056 | use link to access more material from this paper's primary paper code | |
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| In view of the LHC Injectors Upgrade (LIU) and the challenging high brightness target beam parameters, a broad range of possible working points for the Proton Synchrotron (PS) is being investigated. High order resonances have been identified, both structural resonances driven by space charge due to the lattice harmonics of the PS, and resonances excited by multipolar components in the machine. This paper provides a summary of the performed tune scan studies, covering both experimental and simulation results. Furthermore, non-linear analysis techniques have been used to characterize the resonances and their effect on the beam in presence of space charge. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK056 | |
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SUSPF082 |
Space Charge Limitations for Bunch Compression in Synchrotrons | |
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| Bunch compression achieved via a fast bunch rotation in longitudinal phase space is a well-accepted scheme to generate short, intense ion bunches for various applications. During bunch compression, coherent beam instabilities and incoherent single particle resonances can occur because of increasing space charge, resulting in an important limitation for the bunch intensity. We present an analysis of the relevant space charge driven beam instability and resonance phenomena during bunch compression. A coupled longitudinal-transverse envelope approach is compared with Particle-In-Cell (PIC) simulations. Two distinct cases of crossing are discussed and applied to the GSI SIS18 heavy-ion synchrotron. It is shown that during bunch compression, the 90° condition of phase advance is associated with a fourth order single particle resonance and the 120° condition with the recently discovered dispersion-induced instability. The agreement between the envelope and PIC results indicates that the stop band is defined by the 120° dispersion instability, which should be avoided during bunch compression. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK117 | |
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SUSPF083 |
Space Charge and Microbunching Studies for the Injection Arc of MESA | |
| THPAK008 | use link to access more material from this paper's primary paper code | |
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For intense electron bunches traversing through bends, as for example the recirculation arcs of an ERL, space charge (SC) may result in beam phase space deterioration. SC modifies the electron transverse dynamics in dispersive regions along the beam line and causes emittance growth for mismatched beams or for specific phase advances. On the other hand, longitudinal space charge together with dispersion can lead to the microbunching instability. The present study focuses on the 180° low energy (5 MeV) injection arc lattice for the multi-turn Mainz Energy-recovering Superconducting Accelerator (MESA), which should deliver a CW beam at 105 MeV for physics experiments with an internal target. We will discuss matching conditions with space charge together with the estimated microbunching gain for the arc. The implication for the ERL operation will be outlined, using 3D envelope and tracking simulations.
Supported by the DFG through GRK 2128 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK008 | |
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SUSPF084 |
Transverse-to-Longitudinal Photocathode Distribution Imaging | |
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| In this paper, we present a tunable picosecond-scale bunch train generation technique combining a microlens array (MLA) transverse laser shaper and a transverse-to-longitudinal emittance exchange (EEX) beamline. The modulated beamlet array is formed at the photocathode with the MLA setup. The resulting patterned electron beam is accelerated to 50 MeV and transported to the entrance of the EEX setup. A quadrupole channel is used to adjust the transverse spacing of the beamlet array upstream of the EEX, thereby enabling the generation of a bunch train with tunable separation downstream of the EEX beamline. Additionally, the MLA is mounted on a rotation stage which provides additional flexibility to produce high-frequency beam density modulation downstream of the EEX. Experimental results obtained at the Argonne Wakefield Accelerator (AWA) facility are presented and compared with numerical simulations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK060 | |
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SUSPF085 |
Application of Transverse-to-Longitudinal Phase-Space-Exchanged Beam Produced from a Nano-Structure Photocathode to a Soft X-Ray Free-Electron Laser | |
| THPAK065 | use link to access more material from this paper's primary paper code | |
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| Nano-structured cathodes can form transversely modulated beams which can be subsequently converted to temporally modulated beam via a transverse-to-longitudinal phase space-exchanging beamline. We demonstrate via numerical simulation the generation of transversely modulated beam at the nm scale and investigate the corresponding enhancement in a soft-X-ray SASE free-electron laser. Our study is supported by start-to-end simulation combining WARP, IMPACT-T and GENESIS(FEL process) and focuses on the optimization of the beamline to preserve initial modulation at the nanometer level. We also discuss the scaling of the concept to shorter-wavelengths. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK065 | |
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SUSPF086 |
Simulation Study of the Magnetized Electron Beam | |
| THPAK071 | use link to access more material from this paper's primary paper code | |
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Funding: This work is supported by the Department of Energy, Laboratory Directed Research and Development funding, under contract DE-AC05-06OR23177 Electron cooling of the ion beam plays an important role in electron ion colliders to obtain the required high luminosity. This cooling efficiency can be enhanced by using a magnetized electron beam, where the cooling process occurs inside a solenoid field. This paper compares the predictions of ASTRA and GPT simulations to measurements made using a DC high voltage photogun producing magnetized electron beam, related to beam size and rotation angles as a function of the photogun magnetizing solenoid and other parameters. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK071 | |
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SUSPF087 |
A Pseudospectral Method for Solving the Bloch Equations of the Polarization Density in e- Storage Rings | |
| THPAK144 | use link to access more material from this paper's primary paper code | |
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Funding: Work supported by DOE under DE-SC0018008 We consider the numerical evolution of Bloch equations for the polarization density in high-energy electron storage rings. Equilibrium polarization is well characterized by the DK formulas for current rings, but deviations may be important at the high energies we have in mind. We believe the Bloch equations derived in* give a more accurate description at all energies. These form a system of three coupled linear partial differential equations for the three components of the polarization density. Following** we formulate the equations in action-angle variables and approximate the Fokker-Planck terms. We aim to integrate these equations numerically in order to approximate the equilibrium and compare with the DK formulas. The smoothness and simple geometry of the problem makes it amenable to pseudospectral discretization using Fourier modes in the angles and Chebyshev polynomials in the actions, leading to a large ODE system. We will explore time stepping algorithms for the needed long time integration. Here, we present results for simple models checking the accuracy of the numerical method but note that our ultimate goal is to simulate polarization in the FCC and CEPC rings. * Ya.S.Derbenev, A.M.Kondratenko, Sov. Phys. Dokl., 19, p.438 (1975). ** D.P.Barber, K.Heinemann, H.Mais, G.Ripken, A Fokker-Planck treatment of stochastic particle motion…, DESY-91-146, 1991. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK144 | |
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SUSPF088 |
Software-Computing System for Numerical Modelling of Beam Dynamics in Accelerators | |
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| The spectrum of software packages for the physics of charged particles beams is extremely wide. From most popular and effective systems can be allocated such programs as COSY Infinity, MAD X, MARYLIE, TRANSPORT. Heterogeneous individual formats of input and output data, the lack of a common and user-friendly interface and the narrow specialization of these programs poses a number of challenges for the modern researchers. It significantly reduces the effectiveness and quality of corresponding computational experiments. In this article we present a universal tool for automation and acceleration of computing experiments. The authors consider a method for developing the concept and prototype of a corresponding software package that would combine the advantages of existing (non-commercial) systems. This software will be able to unify the input and output data format for certain programs, visualize the information in various ways, provide reference and training information for "beginners". The results obtained within the developed framework will be a significant contribution both to the development of numerical and symbolical methods for solving evolution nonlinear equations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK087 | |
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SUSPF089 |
Development and Benchmarking of the IMPACT-T Code | |
| THPAK076 | use link to access more material from this paper's primary paper code | |
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| The multi-particle tracking code IMPACT-T is widely used to calculate the particle motion in high intensity linacs. The code is a self-consistent three-dimensional beam dynamics simulation toolbox that utilizes the particle-in-cell method in the time domain. In the collaboration between PKU and LBNL, an RFQ module was implemented to the IMPACT-T code, which enables simulations of the accelerator front-end. In order to benchmark the newly developed module in the IMPACT-T code, we have simulated the beam transport in Beijing Isotope Separation On-Line (BISOL) high intensity deuteron driver linac. It consists of a 3 MeV RFQ and 40 MeV superconducting HWR linac with five cryomodules. After comparing the simulation results with PARMTEQM, TraceWin and Toutatis, we obtained a very good agreement, which represents the validation of the new code. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK076 | |
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SUSPF090 |
Wide-Ranging Genetic Research of Matching Line Design for Plasma Accelerated Beams with GIOTTO | |
| THPAK136 | use link to access more material from this paper's primary paper code | |
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GIOTTO is a code based on a Genetic Algorithm, being used in the field of particles accelerators for some years*-***. Its main use concerns beam-dynamics optimizations for low energy linacs, or injectors, where the beam space-charge plays an important role on its dynamics. Typical optimizations regard the Velocity Bunching technique or, more generally, the emittance and energy spread minimization. Recent improvements in GIOTTO, here discussed, have added the important capability to solve problems with a wide research domain, making GIOTTO able to design a beam Transfer Line (TL) from scratch****. The code, taking as input the TL length and the optics elements, can define the correct lattice of the line that transports and matches the beam from the linac to the undulators of an FEL, finding the right gradients, positions and dimensions for the optics elements by exploring the parameters values in selected ranges. Further, the introduction of Twiss parameters into the fitness function makes GIOTTO a powerful tool in the design of highly different beam lines. Lastly, a new routine for the statistical analysis of parameters jitters effects on the beam is under development.
*Bacci et al, NIM-B, 263, 488 (2007) **Bacci et al, presented at PAC'07, THPAN031 ***Bacci et al, presented at IPAC'16, WEPOY039 ****Rossetti Conti et al, NIM-A (2018, in press) |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAK136 | |
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SUSPF091 |
Studies of Horizontal Instabilities in the CERN SPS | |
| THPAF034 | use link to access more material from this paper's primary paper code | |
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| In the framework of the LHC Injectors Upgrade (LIU), beams with double intensity with respect to the present values will have to be successfully accelerated by the CERN Super Proton Synchrotron (SPS) and extracted towards the Large Hadron Collider (LHC). However, first experience running with intensity higher than the nominal LHC beam has shown that coherent instabilities in the horizontal plane may develop, becoming a potential intensity limitation for the future high intensity operation. To understand the mechanism of these instabilities, the PyHEADTAIL code has been used to check if the SPS impedance model reproduces the observations. The instability growth rates have been studied for different machine models and different chromaticity settings. In addition, the effect of other stabilizing methods, like the octupoles and the transverse damper, has also been investigated. Measurements are presented to benchmark the simulations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPAF034 | |
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SUSPF092 |
Tunable Q-Factor Gas-Filled RF Cavity | |
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Funding: Work supported by Fermilab Research Alliance, LLC under Contract No. DE-AC02-07CH11359 and DOE STTR Grant, No. DE-SC0013795. Fermilab is the main institution to produce the most powerful and wide-spectrum neutrino beam. From that respective, a radiation robust beam diagnostic system is a critical element in order to maintain the quality of the neutrino beam. Within this context, a novel radiation-resistive beam profile monitor based on a gas-filled RF cavity has been proposed. The goal of this measurement is to study a tunable Q-factor RF cavity to determine the accuracy of the RF signal as a function of the quality factor. Specifically, the measurement error of the Q-factor in the RF calibration is investigated. Then, the RF system will be improved to minimize signal error. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAG002 | |
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SUSPF093 |
X-Band Low Q Cavity Beam Position Monitor Study | |
| THPML061 | use link to access more material from this paper's primary paper code | |
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| The high repetition-rate and high peak brilliance of X-ray free-electron laser (XFEL) allow studying many scientific experiments that have not been feasible. To realize such high performance, a sub-micron beam transverse position measurement is required. The cavity-type beam position monitor (CBPM), as a non-destructive diagnostics tool with high potential in resolution performance, has been applied in different free electron laser facilities (FELs). In this research, an X-band high bandwidth CBPM has been studied and used for pre-research on bunch-by-bunch diagnostic for the pulsed FEL with high repetition-rate. Its bandwidth reaches 300 MHz. Design considerations and simulation results of the CBPM have been discussed and presented in this paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML061 | |
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SUSPF094 |
SXFEL Linac BPM System Development and Performance Evaluation | |
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| Shanghai Soft X-ray Free Electron Laser (SXFEL) is a test facility to study key technologies and new FEL physics. In order to deliver high quality electron beams to the undulator section, a high resolution (better than 10 microns with 200pC beam) Linac beam position monitor system has been developed. The system consists of stripline pickup and custom designed DBPM processor. The hardware and software architecture will be introduced in this paper. The online performance evaluation results will be presented as well. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML067 | |
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SUSPF095 |
A Beam Based Method to Optimize the SBPM System | |
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| For the electron accelerator, it is hoped that the trajec-tory of the beam can pass through the magnetic center of the quadrupole to minimize the orbital motion caused by the instability of the power supply. The relative deviation between the magnetic center of quadrupole and the elec-tric center of adjacent BPM is measured by electron beam usually in various accelerator facilities. But for the stripline BPM (SBPM) system, in order to achieve the best performance, the beam trajectory should also need to pass through the electrical center of the SBPM system. In this paper, a beam based method to optimize the SBPM system was proposed, the intensity of the magnet power was scanned to change the beam position in two-dimension and combine the change trend of the sum signal of adjacent SBPM to find out the relative deviation of BPM electric center and mechanical center. Relevant beam experiment work on the Shanghai Soft X-ray free electron laser (SXFEL) and the benefit of this method will be addressed as well. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML062 | |
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SUSPF096 |
A Time-of-Flight Based Energy Measurement System for the LIGHT Medical Accelerator | |
| THPML119 | use link to access more material from this paper's primary paper code | |
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| The LIGHT proton therapy facility is the first compact Linac that will deliver proton beams up to 230 MeV for cancer treatment. The proton beam is pulsed; pulses repetition rate can reach 200 Hz. LIGHT prototype is currently being commissioned by AVO/ADAM at CERN, while the first full installation is foreseen in 2019. Beam energy translates directly to range penetration in the body, so it is of the utmost importance to monitor it accurately especially for Linacs, since each beam pulse is directly transported to the patient. We present the implementation of a non-interceptive beam energy measurement system based on the Time-of-Flight technique. Unlike state of the art ToF systems this one has been designed to measure autonomously the mean energy of the beam with medical resolution (0.03 %) by processing as little as 1 us of data providing the result within 1 to 2 ms over an energy range from 5 to 230 MeV. The first results for beams up to 7.5 MeV are shown. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML119 | |
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SUSPF097 |
Applications of a Distributed Beam Loss Monitor at the Australian Synchrotron | |
| THPML130 | use link to access more material from this paper's primary paper code | |
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| A distributed beam loss monitoring system, based on Cherenkov silica fibres, has been installed at the Australian Synchrotron. The fibres are installed parallel to the beam pipe and cover the majority of the injection system and storage ring. Relativistic charged particles from beam loss events that have a velocity above the Cherenkov threshold produce photons in the fibres. These photons are then guided along the fibres to detectors outside of the accelerator tunnels. Originally the system was installed to determine its suitability for measuring losses at a future linear collider, such as the Compact Linear Collider, with single pass 150 ns bunch trains. This study builds on these results and attempts to use the system to measure loss locations with a circulating beam. We present the preliminary results and describe how the system could be improved. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML130 | |
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SUSPF098 |
A Cryogenic Current Comparators (CCC) Customized for FAIR-Project | |
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| The principle of non-destructive measurement of ion beams by detection of the azimuthal magnetic field, using low temperature Superconducting Quantum Interference Device (SQUID) sensors, has been established at GSI already in the mid 90's. After more recent developments at Jena, GSI and CERN, a CCC was installed in the CERN Antiproton Decelerator (AD) and is operated there routinely as the first stand-alone CCC system. For the Facility for Antiproton and Ion Research (FAIR) a new version of the CCC with eXtended Dimensions (CCC-XD) - especially with a larger inner diameter and adapted parameters - was constructed and first lab tests have already been performed. In parallel, a concept for a dedicated UHV beamline cryostat has been worked out. The CCC-XD system - together with the new cryostat - will be ready for testing in the CRYRING at GSI before the end of 2018. In this contribution, experimental results for the resolution, frequency range, slew rate and pulse-signal obtained by electrical laboratory measurements with the CCC-XD are presented. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAK005 | |
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SUSPF100 |
Synchrotron Radiation Beam Diagnostics for the Integrable Optics Test Accelerator | |
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Funding: Work supported by the U.S. National Science Foundation under Award PHY-1535639. Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. The Integrable Optics Test Accelerator (IOTA) is a research electron and proton storage ring currently being commissioned at Fermilab's Accelerator Science and Technology (FAST) facility. An extensive beam physics research program is planned, including tests of novel techniques for improving beam intensity, stability, and emittance. A key part of IOTA beam diagnostics suite are synchrotron light beam monitors, mounted onto each dipole. In this paper, we present the hardware and software design of this system. Mechanical layout and actuator control electronics are described. High throughput image acquisition and analysis architecture is outlined, and its preliminary performance is explored. Integration of the system within accelerator control network and possible user applications, such as camera auto-focusing, are discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAG005 | |
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SUSPF101 |
Determination of RF Resonator Axis Inclination to Beam Axis in Electron-Positron Storage Ring | |
| WEPAL066 | use link to access more material from this paper's primary paper code | |
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| We proposed and tested the method that allows obtaining of an upper limit for an angle of the RF resonator axis inclination relative to a beam axis. Such disturbance gives an additional contribution to separation of electron and positron orbits due to action of the transverse component of the electric field. In the horizontal plane, this effect can lead to increase of the difference between electrons and positrons spin precession frequencies in a storage mono-ring collider. This effect can play a great role in FCC. At the angular disturbance of axis in the certain VEPP-4M RF resonators ~10-3 rad, the difference between the spin frequencies is about 10-8. Our method is based on resonant excitation of betatron oscillations using phase modulation of the master oscillator of the RF system. The maximal amplitude of the enforced oscillations is measured by the counting rate of the VEPP-4M Touschek polarimeter scintillation counters. Comparison of the obtained results with the data of the special calibration experiment allows estimating the value of the inclination angle. In this calibrated experiment the betatron oscillations excite using the VEPP-4M kicker. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL066 | |
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SUSPF102 |
Time-Synchronized Beam Diagnostics at SPEAR3 | |
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| The SPEAR3 timing system supplies a 10Hz trigger pulse synchronous with charge injection into the main storage ring. In the past the 10Hz pulse train has been used to study injected charge transients as seen by visible-light synchrotron radiation diagnostics and turn-by-turn BPMs. More recently the 10Hz pulse has been used to synchronize the bunch-by-bunch feedback data acquisition system with other triggered diagnostic systems. The suite of measurement systems can be used to study injected beam dynamics, grow/damp instability transients and drive/damp physics. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF055 | |
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SUSPF103 |
Design of the Diagnostic Stations for the ELI-NP Compton Gamma Source | |
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| A high brightness electron Linac is being built in the Compton Gamma Source at the ELI Nuclear Physics facility in Romania. To achieve the design luminosity, a train of 32 bunches, 16 ns spaced, with a nominal charge of 250 pC will collide with the laser beam in the interaction point. Electron beam spot size is measured with optical transition radiation (OTR) profile monitors. Furthermore, OTR angular distribution strongly depends on beam energy. Since OTR screens are typically placed in several positions along the Linac to monitor beam envelope, one may perform a distributed energy measurement along the machine. This will be useful, for instance, during the commissioning phase of the GBS in order to verify the correct functionality of the C-Band accelerating structures, due to the fact that there are OTR screens after each accelerating module. This paper deals with the studies of different optic configurations to achieve the field of view, resolution and accuracy in order to measure the energy of the beam. Several configurations of the optical detection line will be studied with simulation tools (e.g. Zemax). | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL013 | |
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SUSPF104 |
Simulations of 3D Charge Density Measurements for Commissioning of the PolariX-TDS | |
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The prototype of a novel X-band transverse deflection structure, the Polarizable X-band (PolariX) TDS*, is currently being prepared for installation in the FLASHForward beamline** at DESY in early 2019. This structure will have the novel feature of variable polarization of the deflecting mode, allowing bunches to be streaked at any transverse angle, rather than at just one angle as in a conventional cavity. By combining screen profiles from several streaking angles using tomographic reconstruction techniques, the full 3D charge density of a bunch can be obtained***. It is planned to perform this measurement for the first time during commissioning of the structure. In this paper, simulations of this measurement are presented and the effects of jitter are discussed.
*P Craievich et al. paper THPAL068, this conference **A Aschikhin et al. Nucl. Instr. Meth. Phys. Res. A., vol.806, pp.175-183, 2018 ***D Marx et al. J. Phys.: Conf. Ser., vol.874, p.012077, 2017 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAF050 | |
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SUSPF105 |
Image Reconstruction Technique Based on Coded Aperture Imaging for SuperKEKB X-ray Beam Size Monitor | |
| THPML074 | use link to access more material from this paper's primary paper code | |
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| The fast reconstruction techniques based on principles originally developed for coded aperture imaging have been investigated for SuperKEKB accelerator. The establishment of this technique will very important for measuring the beam sizes of all 2500 bunches in the SuperKEKB accelerator over thousands of turns, as needed for instability studies and luminosity tuning, due to the vast quantity of data that needs to be processed in a timely manner. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML074 | |
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