title: Observation of enhanced transformer ratio in collinear wakefield acceleration.
abstract: One approach to future high energy particle accelerators is based on the wakefield principle: a leading high-charge drive bunch is used to excite fields in an accelerating structure or plasma that in turn accelerates a trailing low-charge witness bunch. The transformer ratio R is defined as the ratio of the maximum energy gain of the witness bunch to the maximum energy loss of the drive bunch. In general, R<2 for this configuration. A number of techniques have been proposed to overcome the transformer ratio limitation. We report here the first experimental study of the ramped bunch train (RBT) technique in a dielectric based accelerating structure. A single drive bunch was replaced by two bunches with charge ratio of 1:2.5 and a separation of 10.5 wavelengths of the fundamental mode. An average measured transformer ratio enhancement by a factor of 1.31 over the single drive bunch case was obtained.
authors.affiliation: Euclid Techlabs LLC, Solon, Ohio 44139, USA.
authors.forename: C
authors.initials: C
authors.lastname: Jing
authors.forename: A
authors.initials: A
authors.lastname: Kanareykin
authors.forename: J G
authors.initials: JG
authors.lastname: Power
authors.forename: M
authors.initials: M
authors.lastname: Conde
authors.forename: Z
authors.initials: Z
authors.lastname: Yusof
authors.forename: P
authors.initials: P
authors.lastname: Schoessow
authors.forename: W
authors.initials: W
authors.lastname: Gai