WIR SCHAFFEN WISSEN – HEUTE FÜR MORGEN Intra Pulse Phase Control Manuel Brönnimann :: Paul Scherrer Institut LLRF Workshop 2015

SwissFEL Project Concept of IPPC Characterization of the amplifier chain Controller design Results of IPPC at the RF test stand Conclusion and Outlook Agenda Page 2

SwissFEL Project Page 3 6 x 3GHz and 1 x 12GHz accelerator stations (phase tolerance ° and ° ) 26 x 6GHz accelerator stations (phase tolerance ° ) 720m 420m Tunnel Gallery

Page 4 Concept for first prototype The IPPC loop is separated from the LLRF control loop The klystron is operating in saturation therefore the focus is on an intra pulse phase control Studies of several digital and analog concepts have been done →Analog baseband solution has been chosen due to the higher control bandwidth Adjusting of controller parameters by potentiometers Calibration of RF mixer has been done manually for the first prototype The timing system is used to control S&H and resetting the Integrator

Group delay measurement  Rising edge of the different RF pulses has been taken into account => Delay of control path ≈ 100ns Characterization of amplifier chain  Pseudo Random Binary Signal (PRBS) method  Identification of transfer functions for amplitude and phase  Calibration done for excluding the different receiver inputs characteristics The actual LLRF system has been used as measurement system Characterization of Amplifier chain Page 5

Characterization with PRBS method Page 6 phase amp RF pulse after LLRF

Analog PI controller Page 7 PI parameters transferred from Simulink simulations The operational amplifier THS4031 and the analog switch ADG433 have been selected due to several criteria for an intra pulse system S&H was bypassed, the integrator reset command was operational In the lab test a control bandwidth of 1MHz has been measured

Setup at the test stand Page 8

Results of test stand Page 9 measurement Intra pulse pwr in MW(avg) Intra pulse phase stv. dev. in degree P2p phase jitter in degree Without IPPC IPPC in open loop IPPC in closed loop Fast IPPC in closed loop

Conclusion: An Analog baseband concept has been chosen due to higher control bandwidth With the characterization and simulation of the control path the control parameter for the prototype has been calculated. A prototype of the IPPC has been designed and tested (in the Lab and at the RF test stand) successfully Reached three times better pulse to pulse phase jitter when IPPC is used Outlook: 1.Integration of IPPC into the LLRF System 2.Re-engineering with respect to the frequency bands 3.Testing S-band IPPC system at the SwissFEL injector Conclusion & Outlook Page 10

Page 11 Wir schaffen Wissen – heute für morgen Thanks for your attention Questions? Special thanks goes to the entire PSI LLRF team