XBAND Velocity Bunching and Linearizer Sapienza A Mostacci

X-BAND Velocity Bunching and Linearizer Sapienza –A. Mostacci, L. Ficcadenti, J. Arnesano 30/11/2018

Sapienza contribution to XLS-WP 3 Task 3. 1 - Gun Design => D 3. 1 M 18 => D 3. 3 M 36 a. S-Band Gun RF Design (CNRS + IASA+UAIAT-INFN+ALBA ) b. C-Band Gun RF Design (INFN +IASA+Sapienza) c. X-Band Gun RF Design (CSIC-IFIC + UAIAT+ Sapienza) d. DC Gun Design (TU/e ) e. Laser/Photocathode (IASA+CNRS+INFN ) Task 3. 2 - Compressor Design => D 3. 2 M 18 => D 3. 3 M 36 a. S-Band Velocity Bunching (TU/e + IASA+ALBA) b. C-Band Velocity Bunching (INFN +IASA+TU/e ) c. X-Band Velocity Bunching (Sapienza+CERN+IASA+INFN) d. Magnetic Compressor (ST + CERN+INFN+CNRS) Task 3. 3 – X-Band Transverse RF Deflector (Sapienza+IASA) => D 3. 3 M 36 Task 3. 4 - : RF Linearizer Design => D 3. 2 M 18 => D 3. 3 M 36 a. X-Band RF Linearizer Design (Sapienza) b. K-Band RF Linearizer Design (ULANC +Sapienza ) c. Passive linearizer (CNRS ) Started No variation to date Started

Accelerating sections Input Power Output Power - X-band range; TW structure; Δφ=2π/3 mode; Constant Impedance; Normal conducting; Time structure of Swiss. FEL electron beam

SINGLE CELL – on axis E field Siris - Resonant mode: Δφ= 2π/3; Working frequency: 11. 9952 GHz; Fields normalized to dissipated power; rcell riris Δφ Δφ Lcell

Siris SINGLE CELL – Sensitivities rcell riris Lcell - Cell length fixed by phase (RF mode) and velocity (light for electron); - Cell radius by operation frequency; - Iris depth by mechanical constraint (second order parameters variation); - Shunt Impedance strongly depends from aperture; - An average radius of 4 mm was considered; - Question: is the filling time period enough short?

Power coupler tuning* Input Power w (window) - w and Rcoupler tuned to obtain a reflection coefficient Γ as low as possible (0. 01); - Longitudinal Electric field for 1 Watt of input power; Rcoupler *D. Alesini, et al. : "Design of Input Couplers for Traveling Wave Structures", RF-SPARC, 22/01/2007

Power considerations - - Average accelerating voltage vs effective length for different incident power; Average accelerating voltage vs incident power for different structure length;

Conclusions • Single cell parameters Vs iris radius; • Couplers with one hole were tuned; • Different coupler geometries are under study; • We need to know: - Input power available; - Available space; - Required longitudinal voltage; • Next steps: - Long and Trans Wakefield studies;