Design Study of a Compact Injector for a Synchrotron Light Source

Synchrotron light sources are commonly fed with 100-MeV normal conducting linear accelerators powered by a dc thermionic electron gun for high current applications. Such systems are robust solutions for electron sources; however, they tend to have complex bunching systems that increase the complexity and overall cost. In this work, we propose an approach where nonrelativistic bunches are directly injected into a relativistic accelerating structure that is detuned from the optimal frequency. This detuning causes a phase jump, enabling the achievement of beam parameters, such as transmission and energy spread, comparable to those obtained with conventional multistructure bunching systems. The proposed solution simplifies the longitudinal beam dynamics and avoids the need for complex bunching systems. The simplicity and reduced size of this design make the proposed solution interesting for compact electron sources. The article proposes, as an example, a possible upgrade of the Swiss Light Source (SLS) 100-MeV injection linac.