High field hybrid photoinjector electron source for advanced light source applications

A fast tracking code for evaluating collective effects in linear accelerators

“…In either cases we assume monochromatic rectangular beams with uncorrelated bi-gaussian transverse distribution with σ x = 0.5 mm and n = 1 µm • m. Such beams are injected into a distributed coupling ∼ 1 mlong C-band linac section with eE z = 50 MeV/m accelerating gradient and second order focusing strength η = 1.12 − 0.5 cos(2∆φ) [12]. As an additional comment, the beam moments as well as the linac parameters in our benchmark tests usually match those for the ICS source in [14] unless stated differently. Figure 1 shows the center-of-mass trajectory and the energy for a beam injected with a transverse offset of x 0 = 50 µm.…”

“…In Ref. [13,14] we presented a C-band hybrid photo-injector producing high brightness electron beams and driving advanced light sources. Once emitted from the cathode, the beam experiences the typical processes involved in rf guns such as strong rf acceleration, low energy space charge repulsion, focusing through solenoid lenses, chromaticity and, due to the hybrid structure, velocity bunching.…”

“…Improvements of the beam brightness are made possible by novel rf photo-injectors either in the traditional standing wave (SW) or in the hybrid standing wave/traveling wave (SW/TW) [8,9] configuration. Recent designs have proposed a high field SW cryo-cooled gun with optimized cell shape [10][11][12] and a hybrid gun [13,14] both working in C-band at 5.712 GHz. In ad-need for solenoid magnets.…”

“…As a result, the iris dimensions are no longer constrained to coupling requirements and the individual cell shape can be optimized to maximize the acceleration process. This clever concept has been embraced for the realization of cutting edge facilities based on C-band linacs such as ultra-compact X-ray FELs [19], low bandwidth and high flux ICS machines [13,14] and linear colliders [20,21].The above features combined together define a unique scenario for the beam dynamics of high brightness electrons for the following reasons.• The high accelerating gradient and the rich content of space harmonics arising from the optimized cavity topology have a strong impact on the transverse optics [22,23]. As we will discuss in the next section, such features make possible to provide radial focusing in booster linacs following the gun without…”

“…As a result, the iris dimensions are no longer constrained to coupling requirements and the individual cell shape can be optimized to maximize the acceleration process. This clever concept has been embraced for the realization of cutting edge facilities based on C-band linacs such as ultra-compact X-ray FELs [19], low bandwidth and high flux ICS machines [13,14] and linear colliders [20,21].…”