Leonid Rivkin

High-precision x-ray FEL pulse arrival time measurements at SACLA by a THz streak camera with Xe clusters

The accurate measurement of the arrival time of a hard X-ray free electron laser (FEL) pulse with respect to a laser is of utmost importance for pump-probe experiments proposed or carried out at FEL facilities around the world. This manuscript presents the latest device to meet this challenge, a THz streak camera using Xe gas clusters, capable of pulse arrival time measurements with an estimated accuracy of several femtoseconds. An experiment performed at SACLA demonstrates the performance of the device at photon energies between 5 and 10 keV with variable photon beam parameters.

THz streak camera method for synchronous arrival time measurement of two-color hard X-ray FEL pulses

The two-color operation of free electron laser (FEL) facilities allows the delivery of two FEL pulses with different energies, which opens new possibilities for user experiments. Measuring the arrival time of both FEL pulses relative to the external experimental laser and to each other improves the temporal resolution of the experiments using the two-color FEL beam and helps to monitor the performance of the machine itself. This work reports on the first simultaneous measurement of the arrival times of two hard X-ray FEL pulses with the THz streak camera. Measuring the arrival time of the two FEL pulses, the relative delay between them was calculated and compared to the set values. Furthermore, we present the first comparison of the THz streak camera method to the method of FEL induced transient transmission. The results indicate a good agreement between the two methods.

Nanoseconds field emitted current pulses from ZrC needles and field emitter arrays

The properties of the electron source define the ultimate limit of the beam quality in linear accelerators such as free electron lasers (FELs). The goal is to develop an electron gun delivering beam emittance lower than the current state of the art. Such a gun should reduce the cost and size of an x-ray FEL (XFEL). In this article we present two concepts of field emitter cathodes which could potentially produce low emittance beam. The first challenging parameter for such cathode is to emit peak current as high as 5 A. This is the minimum current requirement for the XFEL concept from Paul Scherrer Institut (http://leg.web.psi.ch). Maximum currents of 0.12 and 0.58 A have been reached, respectively, with field emitter arrays and single needle cathodes. Laser assisted field emission gave encouraging results to reach even higher peak current and to prebunch the beam.

Pulsed field emitted current from different commercial samples in the purpose of a free electron laser application

The development of an electron gun with the lowest possible emittance would help reduce the total length and cost of a free electron laser. Recent progress in vacuum microelectronics makes field emitter tips an attractive technology to explore for high brightness electron sources. In order to be a good candidate for a low emittance gun, field emission cathodes must provide at least the peak current, stability, and homogeneity of current state of the art electron sources. In this article, we report on current voltage measurements of commercially available field emitter samples in both continuous and pulsed mode. Pulsed electron emission is of particular interest for a free electron laser application. As mentioned by other authors [F. Charbonnier, Appl. Surf. Sci. 94/95, 26 (1996); P. R. Schwoebol et al., J. Vac. Sci. Technol B 19, 980 (2001)], higher peak current and more stable emission can be achieved when using short square voltage pulses at low frequency. We present maximum peak currents achieved with ...

Simulation of FEL pulse length calculation with THz streaking method

Simulation of THz streaking of photoelectrons created by X-ray pulses from a free-electron laser and reconstruction of the free-electron laser pulse lengths.

The new design of the THz streak camera at PSI

SwissFEL is the Free Electron Laser (FEL) facility under construction at the Paul Scherrer institute (PSI), aiming to provide users with X-ray pulses of lengths down to 2 femtoseconds at standard operation. The measurement of the length of the FEL pulses and their arrival time relative to the experimental laser is crucial for the pump-probe experiments carried out in such facilities. This work presents a new device that measures hard X-ray FEL pulses based on the THz streak camera concept. It describes the prototype setup called pulse arrival and length monitor (PALM) developed at PSI and tested in Spring-8 Angstrom Compact Free Electron Laser (SACLA) in Japan. Based on the first results obtained from the measurements, we introduce the new improved design of the second generation PALM setup that is currently under construction and will be used in SwissFEL photon diagnostics.

A high-brightness accelerator-based EUV source for metrology applications

One of the challenges of actinic metrology tools for EUV lithography is the availability of light sources with high brightness, stability, and availability. In particular, actinic patterned mask inspection on EUV reticles is considered an essential tool for the EUV lithography ecosystem and it requires an EUV source of high brightness. We present the design of a compact and accelerator-based light source producing EUV radiation with high-brightness for actinic metrology applications in the semiconductor industry. Our design is based on the well-established components and design principles. The specifications required for actinic mask inspection is achieved using a short period undulator and 430 MeV electron energy. The concentric design of storage and booster rings enables stable operation with a relatively small footprint. This study shows the commercial viability of a compact and high-brightness EUV source with high stability and reliability and demonstrates its feasibility for actinic metrology applications.