Crab cavities are specialized RF devices designed for colliders targeting high luminosities. It i... more Crab cavities are specialized RF devices designed for colliders targeting high luminosities. It is a straightforward solution to retrieve head-on collision with crossing angle existing to fast separate both beams after collision. The Electron Ion Collider (EIC) has a crossing angle of 25 mrad, and will use local crabbing to minimize the dynamic aperture requirement throughout the rings. The current crab cavity design for the EIC lacks axial symmetry. Therefore, their higher order components of the fundamental deflecting mode have a potential of affecting the long-term beam stability. We present here the multipole analysis and preliminary particle tracking results from the current crab cavity design.
A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Coole... more A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Cooler (LEReC) 2.1 GHz warm cavity. During RHIC run 2019, this tuner was found to cause cavity trips via different failure modes. After analyzing these failure modes, a new straight coaxial tuner without spring fingers was proposed and was installed. We show the operational experience of the new tuner in this paper.
For the radiofrequency (RF) applications of normal conducting film with large mean free path at h... more For the radiofrequency (RF) applications of normal conducting film with large mean free path at high frequency and low temperature, the anomalous skin effect differs considerably from the normal skin effect with field decaying exponentially in the film. Starting from the relationship between the current and the electric field (E field) in the film, the amplitude of E field along the film depth is calculated, and is found to be non-monotonic. The surface impedance is found to have a minimum value at certain film thickness.
The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration... more The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration of electron bunches. To further improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, a normal conducting RF cavity at 1.4 GHz was designed and fabricated for the LINAC that will provide longer electron bunches for the LEReC. It is a single-cell cavity with an effective cavity length shorter than half of the 1.4 GHz wavelength. This cavity was fabricated and tested on-site at BNL to verify RF properties, i.e. the resonance frequency, FPC coupling strength, tuner system performance, and high power tests. In this paper, we report the RF test results for this cavity.
We have started the first tests of the equipment for the coherent electron cooling proof-of-princ... more We have started the first tests of the equipment for the coherent electron cooling proof-of-principle experiment. After tests of the 500 MHz normal conducting cavities we proceeded with the low power beam tests of a CW SRF gun. The results of the tests with record beam parameters are presented.
Crab crossing is an essential mechanism to restore high luminosity and avoid synchro-betatron res... more Crab crossing is an essential mechanism to restore high luminosity and avoid synchro-betatron resonances in the electron-hadron collider eRHIC. The current ring-ring eRHIC design envisages a set of crab cavities operating at 338 MHz. This set of cavities will provide the crabbing kick to the hadron beam of eRHIC. Double-Quarter Wave (DQW) cavities are compact, superconducting RF deflecting cavities appropriate for crab crossing. This paper summarizes the main design requirements and presents an optimized RF design of a DQW cavity for the crabbing system of the ring-ring eRHIC hadron beam.
Coherent electron cooling is new cooling technique to be tested at BNL. Presently we are in the c... more Coherent electron cooling is new cooling technique to be tested at BNL. Presently we are in the commissioning stage of the accelerator system. In this paper we present status of various systems and achieved beam parameters as well as operational experience. Near term future plans are also discussed.
The compact SRF Crab Cavities required for HL-LHC have complex geometries making prediction of av... more The compact SRF Crab Cavities required for HL-LHC have complex geometries making prediction of average and local BCP etch rates a difficult task. This paper describes a series of experiments and simulations used to determine the etch uniformity and rate within these structures. An initial experiment was conducted to determine the correlation between etch rate and flow rate in a Nb tube. These results were then incorporated into Computational Fluid Dynamics simulations of acid flow in the Double Quarter Wave (DQW) cavity to predict etch rates across the surface and allow optimisation of the BCP setup. There were several important findings from the work; one of which is that the flow rate in the relatively large body of the cavity is predominantly driven by natural convection due to the exothermic reaction. During BCP processing of the DQW cavity a significant difference in etching was observed between upper and lower horizontal surfaces which was mitigated by etching in several orien...
The future electron ion collider eRHIC adopts large crossing angle (22 mrad) to allow fast separa... more The future electron ion collider eRHIC adopts large crossing angle (22 mrad) to allow fast separation of two beams in the ring-ring scheme. Crab cavities are required to recover the luminosity from geometric losses. Initial calculation shows that the frequency of the cavities for the ion beam is no more than 336MHz. In this paper, we discuss the crab cavity related lattice parameters for both ion and electron beams in ring-ring design, the frequency choice, and the cavity design considerations.
The eRHIC project will be a electron and proton collider proposed in BNL. These high repetition r... more The eRHIC project will be a electron and proton collider proposed in BNL. These high repetition rates will require Super-Conducting Radio-Frequency cavities with fundamental frequency of 650MHZ for high current applications. Each with a string of two of those cavities. The strong electromagnetic fields in the SRF cavities will extract electrons from the cavity walls and will accelerate those. Most dark current will be deposited locally, although some electrons may reach several neighbour cyromodules, thereby gaining substantial energy before they hit a collimator or other aperture. Simulation of these effects is therefore crucial for the design of the machine. Track3P code was used to simulate field-emission electrons from different SRF cavities setup to optimize the field emission dark current characterizes.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC... more To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for bunch stretching and energy spread correction. In this paper we report the design of these two cavities.
Radio frequency field and particle interaction is of critical importance in modern synchrotrons. ... more Radio frequency field and particle interaction is of critical importance in modern synchrotrons. Accelerator Physics Emulation System (APES) is a C++ code written with the purpose of simulating the particle dynamics in ring-shaped accelerators. During the tracking process, the particles interact with each other indirectly through the EM field excited by the charged particles in the RF cavity. This a hot spot in the algorithm that takes up roughly 90% of the execution time. We show how a set of well-known code restructuring and algorithmic changes coupled with advancements in modern compiler technology can bring down the Ninja gap to provide more than 7x performance improvements. These changes typically require low programming effort, as compared to the very high effort in producing Ninja code.
The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosi... more The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow rings. For the first stage of the project, LEReC-I, we will install a 704 MHz superconducting RF cavity and three normal conducting cavities operating at 9 MHz, 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.
In the development of new superconducting materials for possible use in SRF-based accelerators, i... more In the development of new superconducting materials for possible use in SRF-based accelerators, it is useful to work with small candidate samples rather than complete resonant cavities. The recently commissioned Jefferson Lab RF Surface Impedance Characterization (SIC) system can presently characterize the central region of 50 mm diameter disk samples of various materials from 2 to 40 K exposed to RF magnetic fields up to 14 mT at 7.4 GHz. We report the recent measurement results of bulk Nb, thin film Nb on Cu and sapphire substrates, Nb{sub 3}Sn sample, and thin film MgB{sub 2} on sapphire substrate provided by colleagues at JLab and Temple University.
A 112 MHz superconducting RF photoemission gun was designed, fabricated and installed in RHIC for... more A 112 MHz superconducting RF photoemission gun was designed, fabricated and installed in RHIC for the Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL. The gun was commissioned first without beam. This was followed by generating the first photoemission beam from a multi-alkali cathode. The paper presents the commissioning results.
A recent new analysis of field-dependent BCS rf surface impedance based on moving Cooper pairs ha... more A recent new analysis of field-dependent BCS rf surface impedance based on moving Cooper pairs has been presented.[1] Using this analysis coded in Mathematica TM, survey calculations have been completed which examine the sensitivities of this surface impedance to variation of the BCS material parameters and temperature. The results present a refined description of the "best theoretical" performance available to potential applications with corresponding materials.
Crab cavities are specialized RF devices designed for colliders targeting high luminosities. It i... more Crab cavities are specialized RF devices designed for colliders targeting high luminosities. It is a straightforward solution to retrieve head-on collision with crossing angle existing to fast separate both beams after collision. The Electron Ion Collider (EIC) has a crossing angle of 25 mrad, and will use local crabbing to minimize the dynamic aperture requirement throughout the rings. The current crab cavity design for the EIC lacks axial symmetry. Therefore, their higher order components of the fundamental deflecting mode have a potential of affecting the long-term beam stability. We present here the multipole analysis and preliminary particle tracking results from the current crab cavity design.
A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Coole... more A folded coaxial tuner without spring fingers was designed for the Low Energy RHIC electron Cooler (LEReC) 2.1 GHz warm cavity. During RHIC run 2019, this tuner was found to cause cavity trips via different failure modes. After analyzing these failure modes, a new straight coaxial tuner without spring fingers was proposed and was installed. We show the operational experience of the new tuner in this paper.
For the radiofrequency (RF) applications of normal conducting film with large mean free path at h... more For the radiofrequency (RF) applications of normal conducting film with large mean free path at high frequency and low temperature, the anomalous skin effect differs considerably from the normal skin effect with field decaying exponentially in the film. Starting from the relationship between the current and the electric field (E field) in the film, the amplitude of E field along the film depth is calculated, and is found to be non-monotonic. The surface impedance is found to have a minimum value at certain film thickness.
The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration... more The Low Energy RHIC electron Cooler (LEReC) is the first electron cooler based on rf acceleration of electron bunches. To further improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, a normal conducting RF cavity at 1.4 GHz was designed and fabricated for the LINAC that will provide longer electron bunches for the LEReC. It is a single-cell cavity with an effective cavity length shorter than half of the 1.4 GHz wavelength. This cavity was fabricated and tested on-site at BNL to verify RF properties, i.e. the resonance frequency, FPC coupling strength, tuner system performance, and high power tests. In this paper, we report the RF test results for this cavity.
We have started the first tests of the equipment for the coherent electron cooling proof-of-princ... more We have started the first tests of the equipment for the coherent electron cooling proof-of-principle experiment. After tests of the 500 MHz normal conducting cavities we proceeded with the low power beam tests of a CW SRF gun. The results of the tests with record beam parameters are presented.
Crab crossing is an essential mechanism to restore high luminosity and avoid synchro-betatron res... more Crab crossing is an essential mechanism to restore high luminosity and avoid synchro-betatron resonances in the electron-hadron collider eRHIC. The current ring-ring eRHIC design envisages a set of crab cavities operating at 338 MHz. This set of cavities will provide the crabbing kick to the hadron beam of eRHIC. Double-Quarter Wave (DQW) cavities are compact, superconducting RF deflecting cavities appropriate for crab crossing. This paper summarizes the main design requirements and presents an optimized RF design of a DQW cavity for the crabbing system of the ring-ring eRHIC hadron beam.
Coherent electron cooling is new cooling technique to be tested at BNL. Presently we are in the c... more Coherent electron cooling is new cooling technique to be tested at BNL. Presently we are in the commissioning stage of the accelerator system. In this paper we present status of various systems and achieved beam parameters as well as operational experience. Near term future plans are also discussed.
The compact SRF Crab Cavities required for HL-LHC have complex geometries making prediction of av... more The compact SRF Crab Cavities required for HL-LHC have complex geometries making prediction of average and local BCP etch rates a difficult task. This paper describes a series of experiments and simulations used to determine the etch uniformity and rate within these structures. An initial experiment was conducted to determine the correlation between etch rate and flow rate in a Nb tube. These results were then incorporated into Computational Fluid Dynamics simulations of acid flow in the Double Quarter Wave (DQW) cavity to predict etch rates across the surface and allow optimisation of the BCP setup. There were several important findings from the work; one of which is that the flow rate in the relatively large body of the cavity is predominantly driven by natural convection due to the exothermic reaction. During BCP processing of the DQW cavity a significant difference in etching was observed between upper and lower horizontal surfaces which was mitigated by etching in several orien...
The future electron ion collider eRHIC adopts large crossing angle (22 mrad) to allow fast separa... more The future electron ion collider eRHIC adopts large crossing angle (22 mrad) to allow fast separation of two beams in the ring-ring scheme. Crab cavities are required to recover the luminosity from geometric losses. Initial calculation shows that the frequency of the cavities for the ion beam is no more than 336MHz. In this paper, we discuss the crab cavity related lattice parameters for both ion and electron beams in ring-ring design, the frequency choice, and the cavity design considerations.
The eRHIC project will be a electron and proton collider proposed in BNL. These high repetition r... more The eRHIC project will be a electron and proton collider proposed in BNL. These high repetition rates will require Super-Conducting Radio-Frequency cavities with fundamental frequency of 650MHZ for high current applications. Each with a string of two of those cavities. The strong electromagnetic fields in the SRF cavities will extract electrons from the cavity walls and will accelerate those. Most dark current will be deposited locally, although some electrons may reach several neighbour cyromodules, thereby gaining substantial energy before they hit a collimator or other aperture. Simulation of these effects is therefore crucial for the design of the machine. Track3P code was used to simulate field-emission electrons from different SRF cavities setup to optimize the field emission dark current characterizes.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC... more To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for bunch stretching and energy spread correction. In this paper we report the design of these two cavities.
Radio frequency field and particle interaction is of critical importance in modern synchrotrons. ... more Radio frequency field and particle interaction is of critical importance in modern synchrotrons. Accelerator Physics Emulation System (APES) is a C++ code written with the purpose of simulating the particle dynamics in ring-shaped accelerators. During the tracking process, the particles interact with each other indirectly through the EM field excited by the charged particles in the RF cavity. This a hot spot in the algorithm that takes up roughly 90% of the execution time. We show how a set of well-known code restructuring and algorithmic changes coupled with advancements in modern compiler technology can bring down the Ninja gap to provide more than 7x performance improvements. These changes typically require low programming effort, as compared to the very high effort in producing Ninja code.
The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosi... more The Low Energy RHIC electron Cooling (LEReC) is under development at BNL to improve RHIC luminosity at low energies. It will consist of a short electron linac and two cooling sections, one for blue and one for yellow rings. For the first stage of the project, LEReC-I, we will install a 704 MHz superconducting RF cavity and three normal conducting cavities operating at 9 MHz, 704 MHz and 2.1 GHz. The SRF cavity will boost the electron beam energy up to 2 MeV. The warm cavities will be used to correct the energy spread introduced in the SRF cavity. The paper describes layouts of the SRF and RF systems, their parameters and status.
In the development of new superconducting materials for possible use in SRF-based accelerators, i... more In the development of new superconducting materials for possible use in SRF-based accelerators, it is useful to work with small candidate samples rather than complete resonant cavities. The recently commissioned Jefferson Lab RF Surface Impedance Characterization (SIC) system can presently characterize the central region of 50 mm diameter disk samples of various materials from 2 to 40 K exposed to RF magnetic fields up to 14 mT at 7.4 GHz. We report the recent measurement results of bulk Nb, thin film Nb on Cu and sapphire substrates, Nb{sub 3}Sn sample, and thin film MgB{sub 2} on sapphire substrate provided by colleagues at JLab and Temple University.
A 112 MHz superconducting RF photoemission gun was designed, fabricated and installed in RHIC for... more A 112 MHz superconducting RF photoemission gun was designed, fabricated and installed in RHIC for the Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment at BNL. The gun was commissioned first without beam. This was followed by generating the first photoemission beam from a multi-alkali cathode. The paper presents the commissioning results.
A recent new analysis of field-dependent BCS rf surface impedance based on moving Cooper pairs ha... more A recent new analysis of field-dependent BCS rf surface impedance based on moving Cooper pairs has been presented.[1] Using this analysis coded in Mathematica TM, survey calculations have been completed which examine the sensitivities of this surface impedance to variation of the BCS material parameters and temperature. The results present a refined description of the "best theoretical" performance available to potential applications with corresponding materials.
Uploads