Experimental verification of space-charge saturation scaling laws in high-gradient photocathode RF guns
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arXiv
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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| _version_ | 1866909885650698240 |
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| author | Denham, Paul Garcia, David Kulkarni, Atharva Schaap, Brian Liu, Ziteng Musumeci, Pietro Filippetto, Daniele |
| author_facet | Denham, Paul Garcia, David Kulkarni, Atharva Schaap, Brian Liu, Ziteng Musumeci, Pietro Filippetto, Daniele |
| contents | We investigate the limits of photoemission yield in a high-gradient S-band radiofrequency photoinjector in the space-charge-dominated regime. Using an RF phase-scan technique, where the emitted charge is measured as a function of the RF-field phase in the gun, we directly monitor photoemission over a range of launch fields and laser parameters, enabling quantitative characterization of space-charge saturation. Measurements, supported by simulations and analytic modeling, confirm the characteristic charge-field scaling laws for pancake beams and provide the first experimental verification of cigar-regime scaling in an RF photogun. These results establish a predictive framework for identifying the onset of space-charge saturation and guide the optimization of photoinjectors for ultrafast electron diffraction, microscopy, and high-brightness light sources operating at ultra-high gradients. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_02035 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Experimental verification of space-charge saturation scaling laws in high-gradient photocathode RF guns Denham, Paul Garcia, David Kulkarni, Atharva Schaap, Brian Liu, Ziteng Musumeci, Pietro Filippetto, Daniele Accelerator Physics We investigate the limits of photoemission yield in a high-gradient S-band radiofrequency photoinjector in the space-charge-dominated regime. Using an RF phase-scan technique, where the emitted charge is measured as a function of the RF-field phase in the gun, we directly monitor photoemission over a range of launch fields and laser parameters, enabling quantitative characterization of space-charge saturation. Measurements, supported by simulations and analytic modeling, confirm the characteristic charge-field scaling laws for pancake beams and provide the first experimental verification of cigar-regime scaling in an RF photogun. These results establish a predictive framework for identifying the onset of space-charge saturation and guide the optimization of photoinjectors for ultrafast electron diffraction, microscopy, and high-brightness light sources operating at ultra-high gradients. |
| title | Experimental verification of space-charge saturation scaling laws in high-gradient photocathode RF guns |
| topic | Accelerator Physics |
| url | https://arxiv.org/abs/2511.02035 |