Pub Date : 2020-08-20DOI: 10.18429/JACOW-IPAC2021-MOPAB142
Yelong Wei, A. Grudiev, B. Freemire, C. Jing
It has been technically challenging to efficiently couple external radiofrequency (RF) power to cylindrical dielectric-loaded accelerating (DLA) structures, especially when the DLA structure has a high dielectric constant. This paper presents a novel design of matching section for coupling the RF power from a circular waveguide to an X-band DLA structure with a dielectric constant epsilon_r=16.66 and a loss tangent tan_delta=0.0000343. It consists of a very compact dielectric disk with a width of 2.035 mm and a tilt angle of 60 degree, resulting in a broadband coupling at a low RF field which has the potential to survive in the high-power environment. To prevent a sharp dielectric corner break, a 45 degree chamfer is also added. A microscale vacuum gap, caused by metallic clamping between the thin coating and the outer thick copper jacket, is also studied in detail. Through optimizations, more than 99% of RF power is coupled into the DLA structure, with the maximum electromagnetic fields located at a DLA structure. Tolerance studies on the geometrical parameters and mechanical design of the full-assembly structure are also carried out as a reference for realistic fabrication.
{"title":"A compact, low field, broadband matching section for externally-powered X-band dielectric-loaded accelerating structures","authors":"Yelong Wei, A. Grudiev, B. Freemire, C. Jing","doi":"10.18429/JACOW-IPAC2021-MOPAB142","DOIUrl":"https://doi.org/10.18429/JACOW-IPAC2021-MOPAB142","url":null,"abstract":"It has been technically challenging to efficiently couple external radiofrequency (RF) power to cylindrical dielectric-loaded accelerating (DLA) structures, especially when the DLA structure has a high dielectric constant. This paper presents a novel design of matching section for coupling the RF power from a circular waveguide to an X-band DLA structure with a dielectric constant epsilon_r=16.66 and a loss tangent tan_delta=0.0000343. It consists of a very compact dielectric disk with a width of 2.035 mm and a tilt angle of 60 degree, resulting in a broadband coupling at a low RF field which has the potential to survive in the high-power environment. To prevent a sharp dielectric corner break, a 45 degree chamfer is also added. A microscale vacuum gap, caused by metallic clamping between the thin coating and the outer thick copper jacket, is also studied in detail. Through optimizations, more than 99% of RF power is coupled into the DLA structure, with the maximum electromagnetic fields located at a DLA structure. Tolerance studies on the geometrical parameters and mechanical design of the full-assembly structure are also carried out as a reference for realistic fabrication.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89820279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-14DOI: 10.1103/physrevaccelbeams.23.124201
K. Ruisard, A. Aleksandrov, S. Cousineau, A. Shishlo, V. Tzoganis, A. Zhukov
Modern accelerator front ends almost exclusively include radio-frequency quadrupoles for initial capture and focusing of the low-energy beam. Dynamics in the RFQ define the longitudinal bunch parameters. Simulation of the SNS RFQ with PARMTEQ seeded with a realistic LEBT distribution produces a 2.5 MeV, 40 mA H- beam with root-mean-square emittance of 130 deg-keV. In measurement, a detailed characterization of the longitudinal phase space is made, including a novel study of the dependence of longitudinal emittance on transverse coordinates. This work introduces a new virtual slit technique that provides sub-slit resolution in an energy spectrometer as well as an approach for visualizing 4D phase space data. Through simulation and measurement, the RFQ-formed bunch is confirmed to have significant internal correlated structure. The high-dimensional features are shown to be in qualitative agreement. However, the measured rms emittances are up to 30% lower than predicted, closer to the design value of 95 deg-keV.
{"title":"High dimensional characterization of the longitudinal phase space formed in a radio frequency quadrupole","authors":"K. Ruisard, A. Aleksandrov, S. Cousineau, A. Shishlo, V. Tzoganis, A. Zhukov","doi":"10.1103/physrevaccelbeams.23.124201","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.23.124201","url":null,"abstract":"Modern accelerator front ends almost exclusively include radio-frequency quadrupoles for initial capture and focusing of the low-energy beam. Dynamics in the RFQ define the longitudinal bunch parameters. Simulation of the SNS RFQ with PARMTEQ seeded with a realistic LEBT distribution produces a 2.5 MeV, 40 mA H- beam with root-mean-square emittance of 130 deg-keV. In measurement, a detailed characterization of the longitudinal phase space is made, including a novel study of the dependence of longitudinal emittance on transverse coordinates. This work introduces a new virtual slit technique that provides sub-slit resolution in an energy spectrometer as well as an approach for visualizing 4D phase space data. Through simulation and measurement, the RFQ-formed bunch is confirmed to have significant internal correlated structure. The high-dimensional features are shown to be in qualitative agreement. However, the measured rms emittances are up to 30% lower than predicted, closer to the design value of 95 deg-keV.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74446818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-14DOI: 10.1103/PHYSREVACCELBEAMS.24.014201
K. Ruisard, A. Aleksandrov
Recently, the first direct measurement of a full 6D accelerator beam distribution was reported [1]. That work observed a correlation between energy and transverse coordinates, for which the energy distribution becomes hollowed and double-peaked near the transverse core. In this article, a similar structure is shown to emerge in expansion of an initially uncorrelated, high density bunched beam as the result of velocity perturbation from nonlinear space charge forces. This hollowing is obscured when the 6D phase space is projected onto one- and two-dimensional axes. This phenomenon has not been widely recognized in accelerator systems, but parallels can be drawn to observations of laser-ionized nanoclusters and electron sources for diffraction. While this effect provides insight into the origin of the measured core correlation, it does not provide a complete description. A better reproduction of the measured structure can be obtained via self-consistent simulation through the radio-frequency quadrupole. [1] B. Cathey, S. Cousineau, A. Aleksandrov, and A. Zhukov, PRL 121, 064804 (2018).
{"title":"Rapid charge redistribution leading to core hollowing in a high-intensity ion beam","authors":"K. Ruisard, A. Aleksandrov","doi":"10.1103/PHYSREVACCELBEAMS.24.014201","DOIUrl":"https://doi.org/10.1103/PHYSREVACCELBEAMS.24.014201","url":null,"abstract":"Recently, the first direct measurement of a full 6D accelerator beam distribution was reported [1]. That work observed a correlation between energy and transverse coordinates, for which the energy distribution becomes hollowed and double-peaked near the transverse core. In this article, a similar structure is shown to emerge in expansion of an initially uncorrelated, high density bunched beam as the result of velocity perturbation from nonlinear space charge forces. This hollowing is obscured when the 6D phase space is projected onto one- and two-dimensional axes. This phenomenon has not been widely recognized in accelerator systems, but parallels can be drawn to observations of laser-ionized nanoclusters and electron sources for diffraction. While this effect provides insight into the origin of the measured core correlation, it does not provide a complete description. A better reproduction of the measured structure can be obtained via self-consistent simulation through the radio-frequency quadrupole. [1] B. Cathey, S. Cousineau, A. Aleksandrov, and A. Zhukov, PRL 121, 064804 (2018).","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83665864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-07DOI: 10.1103/PHYSREVACCELBEAMS.23.111002
N. Fuster-Martínez, R. Bruce, F. Cerutti, R. de Maria, P. Hermes, A. Lechner, A. Mereghetti, J. Molson, S. Redaelli, E. Skordis, A. Abramov, L. Nevay
Protons and heavy-ion beams at unprecedented energies are brought into collisions in the CERN Large Hadron Collider for high-energy experiments. The LHC multi-stage collimation system is designed to provide protection against regular and abnormal losses in order to reduce the risk of quenches of the superconducting magnets as well as keeping background in the experiments under control. Compared to protons, beam collimation in the heavy-ion runs is more challenging despite the lower stored beam energies, because the efficiency of cleaning with heavy ions has been observed to be two orders of magnitude worse. This is due to the differences in the interaction mechanisms between the beams and the collimators. Ion beams experience fragmentation and electromagnetic dissociation at the collimators that result in a substantial flux of off-rigidity particles that escape the collimation system. These out-scattered nuclei might be lost around the ring, eventually imposing a limit on the maximum achievable stored beam energy. Accurate simulation tools are crucial in order to understand and control these losses. A new simulation framework has been developed for heavy-ion collimation based on the coupling of the Sixtrack tracking code and the FLUKA Monte Carlo code that models the electromagnetic and nuclear interactions of the heavy-ions with the nuclei of the collimator material. In this paper, the new simulation tool is described. Furthermore, Sixtrack-FLUKA coupling simulations are presented and compared with measurements done with Pb ions in the LHC. The agreement between simulations and measurements is discussed and the results are used to understand and optimise losses. The simulation tool is also applied to predict the performance of the collimation system for the High-Luminosity LHC.
{"title":"Simulations of heavy-ion halo collimation at the CERN Large Hadron Collider: Benchmark with measurements and cleaning performance evaluation","authors":"N. Fuster-Martínez, R. Bruce, F. Cerutti, R. de Maria, P. Hermes, A. Lechner, A. Mereghetti, J. Molson, S. Redaelli, E. Skordis, A. Abramov, L. Nevay","doi":"10.1103/PHYSREVACCELBEAMS.23.111002","DOIUrl":"https://doi.org/10.1103/PHYSREVACCELBEAMS.23.111002","url":null,"abstract":"Protons and heavy-ion beams at unprecedented energies are brought into collisions in the CERN Large Hadron Collider for high-energy experiments. The LHC multi-stage collimation system is designed to provide protection against regular and abnormal losses in order to reduce the risk of quenches of the superconducting magnets as well as keeping background in the experiments under control. Compared to protons, beam collimation in the heavy-ion runs is more challenging despite the lower stored beam energies, because the efficiency of cleaning with heavy ions has been observed to be two orders of magnitude worse. This is due to the differences in the interaction mechanisms between the beams and the collimators. Ion beams experience fragmentation and electromagnetic dissociation at the collimators that result in a substantial flux of off-rigidity particles that escape the collimation system. These out-scattered nuclei might be lost around the ring, eventually imposing a limit on the maximum achievable stored beam energy. Accurate simulation tools are crucial in order to understand and control these losses. A new simulation framework has been developed for heavy-ion collimation based on the coupling of the Sixtrack tracking code and the FLUKA Monte Carlo code that models the electromagnetic and nuclear interactions of the heavy-ions with the nuclei of the collimator material. In this paper, the new simulation tool is described. Furthermore, Sixtrack-FLUKA coupling simulations are presented and compared with measurements done with Pb ions in the LHC. The agreement between simulations and measurements is discussed and the results are used to understand and optimise losses. The simulation tool is also applied to predict the performance of the collimation system for the High-Luminosity LHC.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89047766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-05DOI: 10.1103/PHYSREVACCELBEAMS.23.110702
A. Fisher, P. Musumeci, S. B. van der Geer
In this paper we present a novel approach to FEL simulations based on the decomposition of the electromagnetic field in a finite number of radiation modes. The evolution of each mode amplitude is simply determined by energy conservation. The code is developed as an expansion of the General Particle Tracer framework and adds important capabilities to the suite of well-established numerical simulations already available to the FEL community. The approach is not based on the period average approximation and can handle long-wavelength waveguide FELs as it is possible to include the dispersion effects of the boundaries. Futhermore, it correctly simulates lower charge systems where both transverse and longitudinal space charge forces still play a significant role in the dynamics. For free-space FEL interactions, a source dependent expansion approximation can be used to limit the number of transverse modes required to model the field profile and speed up the calculation of the system evolution. Three examples are studied in detail including a single pass FEL amplifier, the high efficiency TESSA266 scenario and a THz waveguide FEL operating in the zero-slippage regime.
{"title":"Self-consistent numerical approach to track particles in free electron laser interaction with electromagnetic field modes","authors":"A. Fisher, P. Musumeci, S. B. van der Geer","doi":"10.1103/PHYSREVACCELBEAMS.23.110702","DOIUrl":"https://doi.org/10.1103/PHYSREVACCELBEAMS.23.110702","url":null,"abstract":"In this paper we present a novel approach to FEL simulations based on the decomposition of the electromagnetic field in a finite number of radiation modes. The evolution of each mode amplitude is simply determined by energy conservation. The code is developed as an expansion of the General Particle Tracer framework and adds important capabilities to the suite of well-established numerical simulations already available to the FEL community. The approach is not based on the period average approximation and can handle long-wavelength waveguide FELs as it is possible to include the dispersion effects of the boundaries. Futhermore, it correctly simulates lower charge systems where both transverse and longitudinal space charge forces still play a significant role in the dynamics. For free-space FEL interactions, a source dependent expansion approximation can be used to limit the number of transverse modes required to model the field profile and speed up the calculation of the system evolution. Three examples are studied in detail including a single pass FEL amplifier, the high efficiency TESSA266 scenario and a THz waveguide FEL operating in the zero-slippage regime.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77931360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-05DOI: 10.1103/PHYSREVAPPLIED.15.L021002
U. Niedermayer, D. Black, K. Leedle, Yu Miao, R. Byer, O. Solgaard
We demonstrate a compact technique to compress electron pulses to attosecond length, while keeping the energy spread reasonably small. The technique is based on Dielectric Laser Acceleration (DLA) in nanophotonic silicon structures. Unlike previous ballistic optical microbunching demonstrations, we use a modulator-demodulator scheme to compress phase space in the time and energy coordinates. With a second stage, we show that these pulses can be coherently accelerated, producing a net energy gain of $1.5pm0.1$ keV, which is significantly larger than the remaining energy spread of $0.88 ,_{-0.2}^{+0.0}$ keV FWHM. We show that by linearly sweeping the phase between the two stages, the energy spectrum can be coherently moved in a periodic manner, while keeping the energy spread roughly constant. After leaving the buncher, the electron pulse is also transversely focused, and can be matched into a following accelerator lattice. Thus, this setup is the prototype injector into a scalable DLA based on Alternating Phase Focusing (APF).
{"title":"Low-Energy-Spread Attosecond Bunching and Coherent Electron Acceleration in Dielectric Nanostructures","authors":"U. Niedermayer, D. Black, K. Leedle, Yu Miao, R. Byer, O. Solgaard","doi":"10.1103/PHYSREVAPPLIED.15.L021002","DOIUrl":"https://doi.org/10.1103/PHYSREVAPPLIED.15.L021002","url":null,"abstract":"We demonstrate a compact technique to compress electron pulses to attosecond length, while keeping the energy spread reasonably small. The technique is based on Dielectric Laser Acceleration (DLA) in nanophotonic silicon structures. Unlike previous ballistic optical microbunching demonstrations, we use a modulator-demodulator scheme to compress phase space in the time and energy coordinates. With a second stage, we show that these pulses can be coherently accelerated, producing a net energy gain of $1.5pm0.1$ keV, which is significantly larger than the remaining energy spread of $0.88 ,_{-0.2}^{+0.0}$ keV FWHM. We show that by linearly sweeping the phase between the two stages, the energy spectrum can be coherently moved in a periodic manner, while keeping the energy spread roughly constant. After leaving the buncher, the electron pulse is also transversely focused, and can be matched into a following accelerator lattice. Thus, this setup is the prototype injector into a scalable DLA based on Alternating Phase Focusing (APF).","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78125964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-24DOI: 10.1103/physrevaccelbeams.23.101002
A. Gorzawski, A. Abramov, R. Bruce, N. Fuster-Martínez, M. Krasny, J. Molson, S. Redaelli, M. Schaumann
In the scope of the Physics Beyond Colliders studies, the Gamma-Factory initiative proposes the use of partially stripped ions as a driver of a new type of high-intensity photon source in CERN Large Hadron Collider (LHC). In 2018, the LHC accelerated and stored partially stripped $^{208}text{Pb}^{81+}$ ions for the first time. The collimation system efficiency recorded during this test was found to be prohibitively low, so that only a very low-intensity beam could be stored without the risk of triggering a beam dump when regular, minor beam losses occur. The worst losses were localised in the dispersion suppressor of the betatron-cleaning insertion. This article presents an analysis to understand in detail the source of these losses. Based on this understanding, possible mitigation measures that could significantly improve the cleaning efficiency and enable regular operation with partially-stripped ions in the future are developed.
{"title":"Collimation of partially stripped ions in the CERN Large Hadron Collider","authors":"A. Gorzawski, A. Abramov, R. Bruce, N. Fuster-Martínez, M. Krasny, J. Molson, S. Redaelli, M. Schaumann","doi":"10.1103/physrevaccelbeams.23.101002","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.23.101002","url":null,"abstract":"In the scope of the Physics Beyond Colliders studies, the Gamma-Factory initiative proposes the use of partially stripped ions as a driver of a new type of high-intensity photon source in CERN Large Hadron Collider (LHC). In 2018, the LHC accelerated and stored partially stripped $^{208}text{Pb}^{81+}$ ions for the first time. The collimation system efficiency recorded during this test was found to be prohibitively low, so that only a very low-intensity beam could be stored without the risk of triggering a beam dump when regular, minor beam losses occur. The worst losses were localised in the dispersion suppressor of the betatron-cleaning insertion. This article presents an analysis to understand in detail the source of these losses. Based on this understanding, possible mitigation measures that could significantly improve the cleaning efficiency and enable regular operation with partially-stripped ions in the future are developed.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80805898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-29DOI: 10.1103/physrevaccelbeams.23.104001
E. Laface, B. Folsom
The common treatment of time-dependent potentials, such as those used for radio frequency cavities, is to average a potential's time component through the interval that the reference particle spends in the cavity. Such an approach, using the so-called transit-time factor, uses time as the independent variable in the Hamiltonian. In this paper, we instead propose a fully covariant Hamiltonian to treat the time component of the potential like any other space component. We show how to calculate the dynamics of the particles in a pill-box cavity using an explicit sympletic integrator. Finally, we compare the results with the simulator TraceWin.
{"title":"Covariant Hamiltonian approach for time-dependent potentials applied to a pill-box cavity","authors":"E. Laface, B. Folsom","doi":"10.1103/physrevaccelbeams.23.104001","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.23.104001","url":null,"abstract":"The common treatment of time-dependent potentials, such as those used for radio frequency cavities, is to average a potential's time component through the interval that the reference particle spends in the cavity. Such an approach, using the so-called transit-time factor, uses time as the independent variable in the Hamiltonian. In this paper, we instead propose a fully covariant Hamiltonian to treat the time component of the potential like any other space component. We show how to calculate the dynamics of the particles in a pill-box cavity using an explicit sympletic integrator. Finally, we compare the results with the simulator TraceWin.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85940285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-26DOI: 10.1103/physrevaccelbeams.23.100701
P. H. Williams, G. P'erez-Segurana, I. Bailey, S. Thorin, B. Kyle, J. Svensson
Electron bunch compressors formed of achromat arcs have a natural advantage over the more commonly used chicane compressors in that linearisation of the longitudinal phase space is of the correct sign to compensate for the curvature imprinted by rf acceleration. Here we extend the utility of arc compressors to enable variation of the longitudinal compaction within a fixed footprint. We also show that this variability can be achieved independently order-by-order in momentum deviation. The technique we employ consists of additional dipoles, leading to the advantageous property that variability can be achieved without incurring significant penalty in terms of chromatic degradation. We show this by comparison to an alternative system where additional quadrupoles are utilised to enable variation of momentum compaction. Each of these alternative approaches are being considered in the context of an upgrade of the MAX IV linac, Sweden, to enable a soft X-ray free-electron laser (FEL) in addition to its existing functions.
{"title":"Arclike variable bunch compressors","authors":"P. H. Williams, G. P'erez-Segurana, I. Bailey, S. Thorin, B. Kyle, J. Svensson","doi":"10.1103/physrevaccelbeams.23.100701","DOIUrl":"https://doi.org/10.1103/physrevaccelbeams.23.100701","url":null,"abstract":"Electron bunch compressors formed of achromat arcs have a natural advantage over the more commonly used chicane compressors in that linearisation of the longitudinal phase space is of the correct sign to compensate for the curvature imprinted by rf acceleration. Here we extend the utility of arc compressors to enable variation of the longitudinal compaction within a fixed footprint. We also show that this variability can be achieved independently order-by-order in momentum deviation. The technique we employ consists of additional dipoles, leading to the advantageous property that variability can be achieved without incurring significant penalty in terms of chromatic degradation. We show this by comparison to an alternative system where additional quadrupoles are utilised to enable variation of momentum compaction. Each of these alternative approaches are being considered in the context of an upgrade of the MAX IV linac, Sweden, to enable a soft X-ray free-electron laser (FEL) in addition to its existing functions.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89784932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-06-02DOI: 10.3390/INSTRUMENTS4040028
E. Barzi, F. Berritta, D. Turrioni, A. Zlobin
A major focus of Nb$_3$Sn accelerator magnets is on significantly reducing or eliminating their training. Demonstration of an approach to increase the $C_p$ of Nb$_3$Sn magnets using new materials and technologies is very important both for particle accelerators and light sources. It would improve thermal stability and lead to much shorter magnet training, with substantial savings in machines' commissioning costs. Both Hypertech and Bruker-OST have attempted to introduce high-$C_p$ elements in their wire design. This paper includes a description of these advanced wires, the finite element model of their heat diffusion properties as compared with the standard wires, and whenever available, a comparison between the minimum quench energy (MQE) calculated by the model and actual MQE measurements on wires.
{"title":"Heat Diffusion in High-Cp Nb3Sn Composite Superconducting Wires","authors":"E. Barzi, F. Berritta, D. Turrioni, A. Zlobin","doi":"10.3390/INSTRUMENTS4040028","DOIUrl":"https://doi.org/10.3390/INSTRUMENTS4040028","url":null,"abstract":"A major focus of Nb$_3$Sn accelerator magnets is on significantly reducing or eliminating their training. Demonstration of an approach to increase the $C_p$ of Nb$_3$Sn magnets using new materials and technologies is very important both for particle accelerators and light sources. It would improve thermal stability and lead to much shorter magnet training, with substantial savings in machines' commissioning costs. Both Hypertech and Bruker-OST have attempted to introduce high-$C_p$ elements in their wire design. This paper includes a description of these advanced wires, the finite element model of their heat diffusion properties as compared with the standard wires, and whenever available, a comparison between the minimum quench energy (MQE) calculated by the model and actual MQE measurements on wires.","PeriodicalId":8436,"journal":{"name":"arXiv: Accelerator Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90035886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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