S. J. Park, C. K. Min, Y. G. Park, S. D. Jang, G. Y. Jang, H. S. Shin
{"title":"PAL速调管电子枪的设计改进","authors":"S. J. Park, C. K. Min, Y. G. Park, S. D. Jang, G. Y. Jang, H. S. Shin","doi":"10.1007/s40042-025-01338-1","DOIUrl":null,"url":null,"abstract":"<div><p>Several prototype S-band pulsed klystrons for use at the Pohang Accelerator Laboratory (PAL) have been developed by a domestic company in collaboration with PAL. These klystrons successfully achieved the required RF output power at a low repetition rate (< 30 Hz) but suffered from gun arcing when operated at 60 Hz, which is the repetition rate required for the PAL-XFEL. Post-mortem inspection revealed that the arcing spots on the focusing electrode (Wehnelt) were not located at the regions of maximum electric field. Particle trajectory simulations in the electron gun region suggest that the initial arcing is triggered by electron emission and followed by clump-induced breakdown processes. In addition, vacuum breakdown can be initiated from the so-called triple point (TP) at the lower end of the ceramic insulator, where a negative potential is applied during high-voltage (HV) operation. Further numerical simulations confirmed that electrons emitted from this TP can travel along the ceramic surface, undergo multiplication, and eventually cause breakdown near the anode housing. Based on these findings, we propose design improvements—most notably enhanced cleaning and polishing procedures as well as an added electric field shield near the TP—to suppress vacuum breakdown at higher repetition rates (e.g., 60 Hz). Initial high-voltage (HV) processing data show that the improved gun design significantly reduces arcing events, enabling stable klystron operation.</p></div>","PeriodicalId":677,"journal":{"name":"Journal of the Korean Physical Society","volume":"87 on","pages":"860 - 867"},"PeriodicalIF":0.9000,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Design improvements of electron gun for PAL klystron\",\"authors\":\"S. J. Park, C. K. Min, Y. G. Park, S. D. Jang, G. Y. Jang, H. S. Shin\",\"doi\":\"10.1007/s40042-025-01338-1\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Several prototype S-band pulsed klystrons for use at the Pohang Accelerator Laboratory (PAL) have been developed by a domestic company in collaboration with PAL. These klystrons successfully achieved the required RF output power at a low repetition rate (< 30 Hz) but suffered from gun arcing when operated at 60 Hz, which is the repetition rate required for the PAL-XFEL. Post-mortem inspection revealed that the arcing spots on the focusing electrode (Wehnelt) were not located at the regions of maximum electric field. Particle trajectory simulations in the electron gun region suggest that the initial arcing is triggered by electron emission and followed by clump-induced breakdown processes. In addition, vacuum breakdown can be initiated from the so-called triple point (TP) at the lower end of the ceramic insulator, where a negative potential is applied during high-voltage (HV) operation. Further numerical simulations confirmed that electrons emitted from this TP can travel along the ceramic surface, undergo multiplication, and eventually cause breakdown near the anode housing. Based on these findings, we propose design improvements—most notably enhanced cleaning and polishing procedures as well as an added electric field shield near the TP—to suppress vacuum breakdown at higher repetition rates (e.g., 60 Hz). Initial high-voltage (HV) processing data show that the improved gun design significantly reduces arcing events, enabling stable klystron operation.</p></div>\",\"PeriodicalId\":677,\"journal\":{\"name\":\"Journal of the Korean Physical Society\",\"volume\":\"87 on\",\"pages\":\"860 - 867\"},\"PeriodicalIF\":0.9000,\"publicationDate\":\"2025-03-10\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of the Korean Physical Society\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://link.springer.com/article/10.1007/s40042-025-01338-1\",\"RegionNum\":4,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"PHYSICS, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of the Korean Physical Society","FirstCategoryId":"101","ListUrlMain":"https://link.springer.com/article/10.1007/s40042-025-01338-1","RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"PHYSICS, MULTIDISCIPLINARY","Score":null,"Total":0}
Design improvements of electron gun for PAL klystron
Several prototype S-band pulsed klystrons for use at the Pohang Accelerator Laboratory (PAL) have been developed by a domestic company in collaboration with PAL. These klystrons successfully achieved the required RF output power at a low repetition rate (< 30 Hz) but suffered from gun arcing when operated at 60 Hz, which is the repetition rate required for the PAL-XFEL. Post-mortem inspection revealed that the arcing spots on the focusing electrode (Wehnelt) were not located at the regions of maximum electric field. Particle trajectory simulations in the electron gun region suggest that the initial arcing is triggered by electron emission and followed by clump-induced breakdown processes. In addition, vacuum breakdown can be initiated from the so-called triple point (TP) at the lower end of the ceramic insulator, where a negative potential is applied during high-voltage (HV) operation. Further numerical simulations confirmed that electrons emitted from this TP can travel along the ceramic surface, undergo multiplication, and eventually cause breakdown near the anode housing. Based on these findings, we propose design improvements—most notably enhanced cleaning and polishing procedures as well as an added electric field shield near the TP—to suppress vacuum breakdown at higher repetition rates (e.g., 60 Hz). Initial high-voltage (HV) processing data show that the improved gun design significantly reduces arcing events, enabling stable klystron operation.
期刊介绍:
The Journal of the Korean Physical Society (JKPS) covers all fields of physics spanning from statistical physics and condensed matter physics to particle physics. The manuscript to be published in JKPS is required to hold the originality, significance, and recent completeness. The journal is composed of Full paper, Letters, and Brief sections. In addition, featured articles with outstanding results are selected by the Editorial board and introduced in the online version. For emphasis on aspect of international journal, several world-distinguished researchers join the Editorial board. High quality of papers may be express-published when it is recommended or requested.