M. Pedrozzi

Commissioning of the Swiss Light Source

The Swiss Light Source (SLS) at the Paul Scherrer Institute (PSI) consists of a turn key 100 MeV linac, a novel type of booster synchrotron and a 12-TBA storage ring providing 5 nm-rad natural emittance at 2.4 GeV, The SLS project was approved by Swiss Government in Sept. 1997. By June 1999 the building was finished. Linac and booster commissioning concluded by April, resp. Sept. 2000. First beam in the ring was stored Dec. 15, 2000. By June 2001 storage ring commissioning entered the final phase: The design current of 400 mA was reached, an excellent agreement of lattice functions with design calculations was achieved and first undulator spectra were measured. Commissioning of booster and storage ring included commissioning of the innovative subsystems like the digital BPM system, the digital power supplies, the high stability injection system and the CORBA based beam dynamics software.

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.

Development of a low emittance electron gun based on field emission cathodes

Field emitters are investigated for use as a low emittance electron gun. Two available field emitter technologies are currently explored; the field emitter arrays (FEAs) with individual focusing and single tip cathode with robust and fairly blunt apex. The challenge is to achieve several amperes of peak current without tip destructions. Very good cathode and environmental conditioning procedures with extremely short emission duration (ns) at low repetition rate (10 Hz) gave encouraging results to reach high peak current emission. For a free electron laser application, very short emission durations are preferred. Such operation regime should prevent the tip from overheating so that higher current densities could be reached. Another possible low emittance electron sources are single needle tips made from etched wires and which can be coated and formed in order to carry high current emission. One way to achieve short emission duration is to use pulsed laser light illuminating the tip while high electric field is applied.