A sub-50 femtosecond bunch arrival time monitor system for

Abstract A bunch arrival time monitor using the future laser based synchronization system at FLASH has been developed. The signal of a beam pick-up with several GHz bandwidth is sampled by a sub-ps laser pulse using a broadband electro-optical modulator. Bunch arrival time deviations are converted into amplitude modulations of the sampling laser pulses which are then detected by a photo-detector. A resolution of 30 fs could be reached with the capability towards sub-10 fs level. In this paper we describe the design of the optical system and present recent results

Empirical comparison of high gradient achievement for different metals in DC and pulsed mode

For the SwissFEL project, an advanced high gradient low emittance gun is under development. Reliable operation with an electric field, preferably above 125 MV/m at a 4 mm gap, in the presence of an UV laser beam, has to be achieved in a diode configuration in order to minimize the emittance dilution due to space charge effects. In the first phase, a DC breakdown test stand was used to test different metals with different preparation methods at voltages up to 100 kV. In addition high gradient stability tests were also carried out over several days in order to prove reliable spark-free operation with a minimum dark current. In the second phase, electrodes with selected materials were installed in the 250 ns FWHM, 500 kV electron gun and tested for high gradient breakdown and for quantum efficiency using an ultra-violet laser.Comment: 25 pages, 13 figures, 5 tables. Follow up from FEL 2008 conference (Geyongju Korea 2008) New Title in JVST A (2010) : Vacuum breakdown limit and quantum efficiency obtained for various technical metals using DC and pulsed voltage source

FELS AS X RAY SOURCES IN ERL FACILITIES

Hard x ray EnergyRecovery Linacs ERLs operate with high brightness electron beams, matching the requirements for x ray FELs in terms of emittance and energy spread. We have analyzed in how far it is feasible to include xray FELs in ERL facilities. x ray FEL oscillators require comparatively low peak currents and are therefore good candidates for FEL sources in ERLs. However, high gain FELs do not seem out of reach when bunch compression schemes for higher peak currents are utilized. Using the proposed Cornell ERL as an example, different FEL concepts are discussed and their suitability as x ray sources are analyze

X Ray FELs Based on ERL Facilities

The characteristic high repetition rate and the high brightness of electron beams delivered by ERLs have led to a great number of ERL based proposals for hard x ray sources including x ray FELs. FEL oscillators requiring comparatively low peak currents are often proposed for FEL sources in ERLs. However, single pass FELs in SASE or seeded mode do not seem out of reach when bunchcompression schemes for higher peak currents are utilized. Using the proposed Cornell ERL as an example, we present and discuss oscillator and single pass FEL schemes which provide high brightness ultra short x ray pulses for experiment