Increasing the transformer ratio at the Argonne wakefield accelerator

• Main Authors: C. Jing, J. G. Power, M. Conde, W. Liu, Z. Yusof, A. Kanareykin, W. Gai
• Format: Article
• Language: English
• Published: American Physical Society 2011-02-01
• Series: Physical Review Special Topics. Accelerators and Beams
• Online Access: http://doi.org/10.1103/PhysRevSTAB.14.021302

The transformer ratio is defined as the ratio of the maximum energy gain of the witness bunch to the maximum energy loss experienced by the drive bunch (or a bunch within a multidrive bunch train). This plays an important role in the collinear wakefield acceleration scheme. A high transformer ratio is desirable since it leads to a higher overall efficiency under similar conditions (e.g. the same beam loading, the same structure, etc.). One technique to enhance the transformer ratio beyond the ordinary limit of 2 is to use a ramped bunch train. The first experimental demonstration observed a transformer ratio only marginally above 2 due to the mismatch between the drive microbunch length and the frequency of the accelerating structure [C. Jing, A. Kanareykin, J. Power, M. Conde, Z. Yusof, P. Schoessow, and W. Gai, Phys. Rev. Lett. 98, 144801 (2007)PRLTAO0031-900710.1103/PhysRevLett.98.144801]. Recently, we revisited this experiment with an optimized microbunch length using a UV laser stacking technique at the Argonne Wakefield Accelerator facility and measured a transformer ratio of 3.4. Measurements and data analysis from these experiments are presented in detail.