High resolution and low charge button and strip-line beam position monitor electronics upgrade at FLASH

B Lorbeer,R Neumann,D Lipka,N Baboi,H-T Duhme

doi:10.1088/1742-6596/1067/7/072011

Abstract

Historically the FLASH (Free Electron Laser in Hamburg) facility at DESY (Deutsches Elektronen-Synchrotron) in Germany has foreseen operation in a charge range from 1 nC-3 nC for which a VME based BPM (Beam Position Monitor) system has been in operation since 2005 with a later upgrade to lower charges. In the past few years the standard machine operation settled at a few hundreds of pC with a tendency to smaller charges down to 100 pC and less. The performance of the BPM system at charges below 300 pC was in many locations along the machine unsatisfactory, making the operation of the linac more unstable and less reliable. Therefore a new BPM electronic system based on the utca (Micro Telecommunication Computing Architecture) for physics MTCA.4 standard has been developed to overcome the limitations of the old electronics and has already been successfully in operation in FLASH 2. A substantially improved version of the RF (radio frequency) front-end and digital electronics/firmware has been developed in 2016 and tested successfully. The peak detector electronics have been extended to a double peak detection in four channels and the fully customized Firmware is working machine synchronous. In summer 2017 all old button and strip-line BPM electronics have been replaced with the new type. This paper summarizes the features and performance of the new BPM system, compares the beam jitter free resolution of the old and new BPM system and highlights its high single shot resolution of better than 10 μm rms at a charge of 15 pC.

Highlights

Here for simultaneous and independent operation at a different charge and a different FEL pulse wavelength [3]
Since the VME based BPM (Beam Position Monitor) installed at FLASH did not have a satisfactory performance at low bunch charge [3, 8, 9] it has been replaced with new utca based electronics in summer 2017
The electrons are generated by a UV photo injector laser which releases electrons from a cathode inside an RF gun

Summary

Introduction

Here for simultaneous and independent operation at a different charge and a different FEL pulse wavelength [3]. It has been shown that the generation of FEL pulses on the order of few fs depends crucially on the charge of the beam [4, 5]. Since the VME based BPM (Beam Position Monitor) installed at FLASH did not have a satisfactory performance at low bunch charge [3, 8, 9] it has been replaced with new utca based electronics in summer 2017. The electron beam is accelerated to an energy of up to 1.2 GeV after which it is fed to an undulator line to generate FEL pulses through the SASE (Self Amplified Spontaneous Emission) process.

Results

Conclusion