A 100 Mev Injector Linac for the Swiss Light Source Supplied by Industry

A 100 MeV ‘turn-key’ injector electron linac for the Swiss Light Source (SLS) is under construction at ACCEL Instruments. The system will be installed, commissioned and handed over to the SLS in late 1999, after a 18 month design and production period. This paper will present the special needs of an injector for a third generation synchrotron light source and the two specific modes of operation for this linac. The specification of the system and a description of the design results as well as the planned technical realisation will be given. 1 REQUIREMENTS FOR THE SLS INJECTOR SYSTEM A third generation synchrotron light source is equipped with several types of insertion devices such as wigglers, undulators and wavelength shifters. These devices can be driven in several operation modes. To drive a Free Electron Laser for example a single bunch mode operation is required. This results in single and multi bunch operation modes, to fulfil the different needs of the users. 1.1 General specification The SLS accelerating system will consist of a 100 MeV Linac and a full energy booster. The general parameters [1] of the linac are listed in the following table 1: Table 1: General Specifications RF frequency 2.997921 GHz Max. repetition rate 10 Hz Energy 100 MeV 1.2 Pulse modes Two modes of operation are foreseen. One single bunch mode and one variable multi bunch mode. The multi bunch mode will cover the range on 50-500 bunches. To reduce the effect of beam loading the multi bunch mode will carry the same charge as the single bunch mode. The basic parameters of both modes are given in table 2. In addition the SLS layout foresees a top up injection mode, this mode will deliver a low current to the storage 1 In this context the bucket length of the ring rf system defines the bunch length of 2 ns ring, to keep the mean current in the storage ring nearly constant. Table 2: Operation Modes Short Pulse Long Pulse Pulse length 1 ns 100-1000 ns Pulse charge 1.5 nC 1.5 nC Emittance 50 π mm mrad 50 π mm mrad Energy 100 MeV 100 MeV ∆E/E 0.5 % 0.5 % 2 LAYOUT OF THE SYSTEM The main components of the injector system are based on components which were developed for the S-Band Test Facility (SBTF) at DESY 2. Adopting these components for the special needs of the SLS project took place during the design phase. To fulfil the requirements the system consists of three functional sections: • The electron source • The bunching section • The accelerating structures Figure 1: General Layout 2.1 The electron source The electrons will be provided by a 90 kV DC conventional electron source as shown in Figure 2. The electron emitter is a standard EIMAC cathode YU-171. The pulser for the electron source comprises two systems, one for the single bunch and one for the multi bunch mode. In the single bunch mode a 1 ns pulse carrying 3 nC will be sufficient to guarantee 1.5 nC at the end of the Linac. The multi bunch mode will be modulated by the 499.652 MHz main ring rf, to insure a high bunch purity. 0-7803-5573-3/99/$10.00@1999 IEEE. 3510 Proceedings of the 1999 Particle Accelerator Conference, New York, 1999