Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKB
In SuperKEKB high-current beam operation, achieving the stability of the zero mode associated with the accelerating mode of the rf system is an important concern because of heavy beam loading. The issue is a more serious problem in the high-energy ring (HER) compared to the low-energy ring (LER) bec...
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
American Physical Society
2022-10-01
|
| Series: | Physical Review Accelerators and Beams |
| Online Access: | http://doi.org/10.1103/PhysRevAccelBeams.25.102002 |
| _version_ | 1798019966355636224 |
|---|---|
| author | Kazunori Akai |
| author_facet | Kazunori Akai |
| author_sort | Kazunori Akai |
| collection | DOAJ |
| description | In SuperKEKB high-current beam operation, achieving the stability of the zero mode associated with the accelerating mode of the rf system is an important concern because of heavy beam loading. The issue is a more serious problem in the high-energy ring (HER) compared to the low-energy ring (LER) because of the high impedance of superconducting cavities operating in the HER. As a countermeasure, the rf system is equipped with a direct rf feedback system (DRFB) to effectively reduce the impedance of the cavities and a zero mode oscillation damper. The effect of these mitigations on improving the stability while coexisting with other control loops was quantitatively studied using two independent methods, namely, analysis with a characteristic equation and simulation in the time domain. For the analysis, we extended the transfer functions in the Pedersen model to include the DRFB to analyze the rf system with beam loading, while coexisting with the other control loops such as amplitude and phase controls. The consistency between both methods was confirmed by comparing the results obtained from them for different cases. Furthermore, simulation results were compared with measurements conducted during beam operation; they were consistent with each other. Having confirmed the validity of these methods, they were applied to extensively study the stability for future higher beam current operations in SuperKEKB. Particularly, several operation parameter sets, including possible system modifications, were identified for the HER and LER with considerably good margins to compensate for possible deficiencies in the performance of cavities or control functions at higher beam currents. The results can be used as guidelines for future beam operations with beam current increasing in a stepwise manner. |
| first_indexed | 2024-04-11T16:50:10Z |
| format | Article |
| id | doaj.art-91cab6c793194de3bce443ae00d4b1a4 |
| institution | Directory Open Access Journal |
| issn | 2469-9888 |
| language | English |
| last_indexed | 2024-04-11T16:50:10Z |
| publishDate | 2022-10-01 |
| publisher | American Physical Society |
| record_format | Article |
| series | Physical Review Accelerators and Beams |
| spelling | doaj.art-91cab6c793194de3bce443ae00d4b1a42022-12-22T04:13:28ZengAmerican Physical SocietyPhysical Review Accelerators and Beams2469-98882022-10-01251010200210.1103/PhysRevAccelBeams.25.102002Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKBKazunori AkaiIn SuperKEKB high-current beam operation, achieving the stability of the zero mode associated with the accelerating mode of the rf system is an important concern because of heavy beam loading. The issue is a more serious problem in the high-energy ring (HER) compared to the low-energy ring (LER) because of the high impedance of superconducting cavities operating in the HER. As a countermeasure, the rf system is equipped with a direct rf feedback system (DRFB) to effectively reduce the impedance of the cavities and a zero mode oscillation damper. The effect of these mitigations on improving the stability while coexisting with other control loops was quantitatively studied using two independent methods, namely, analysis with a characteristic equation and simulation in the time domain. For the analysis, we extended the transfer functions in the Pedersen model to include the DRFB to analyze the rf system with beam loading, while coexisting with the other control loops such as amplitude and phase controls. The consistency between both methods was confirmed by comparing the results obtained from them for different cases. Furthermore, simulation results were compared with measurements conducted during beam operation; they were consistent with each other. Having confirmed the validity of these methods, they were applied to extensively study the stability for future higher beam current operations in SuperKEKB. Particularly, several operation parameter sets, including possible system modifications, were identified for the HER and LER with considerably good margins to compensate for possible deficiencies in the performance of cavities or control functions at higher beam currents. The results can be used as guidelines for future beam operations with beam current increasing in a stepwise manner.http://doi.org/10.1103/PhysRevAccelBeams.25.102002 |
| spellingShingle | Kazunori Akai Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKB Physical Review Accelerators and Beams |
| title | Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKB |
| title_full | Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKB |
| title_fullStr | Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKB |
| title_full_unstemmed | Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKB |
| title_short | Stability analysis of rf accelerating mode with feedback loops under heavy beam loading in SuperKEKB |
| title_sort | stability analysis of rf accelerating mode with feedback loops under heavy beam loading in superkekb |
| url | http://doi.org/10.1103/PhysRevAccelBeams.25.102002 |
| work_keys_str_mv | AT kazunoriakai stabilityanalysisofrfacceleratingmodewithfeedbackloopsunderheavybeamloadinginsuperkekb |