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Paul Scherrer Institut PSI Accelerator Development and Operation Support

Paul Scherrer Institut
5232 Villigen PSI, Schweiz/Switzerland
Tel. +41 56 310 21 11
Fax. +41 56 310 21 99

E-Mail: andreas.streun@psi.ch

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Parameter List of Linac

final energy 100 MeV
traveling wave structures 2*5.2m
RF frequency 3 GHz
pulse length:
single bunch mode 1 ns
multi bunch mode 700 ns
charge/pulse 1 nC
energy spread < 0.2%
normalized emittance < 50 pi mm mrad
traveling wave bunchers 2 at 3 GHz
subharmonic prebuncher 1 at 500 MHz
electron gun voltage 90kV
transmission through Linac 90%
cycling rate 3.125 Hz

The SLS Linac was bought as a turn key system from ACCEL instruments Gmbh in Germany. The two traveling wave structures (phase advance=2 pi/3) were built according to a structure developped at DESY in Hamburg.
Some components, like the 3 GHz Thomson-Klystrons (2*35MW), the diagnostic system and the beam-transfer lines were directly provided by PSI.
The first beam from the Linac was obtained in the spring of 2000.

The Linac was specified to operate in a short bunch mode as well as a long bunch mode. Since 2002 the Linac is running most of the time in the short bunch mode, which gives more flexibility for top-up injection into the SLS storage ring, the preferred operation mode since 2002.

To measure the beam properties of the Linac beam a diagnostic section with a 45 bend and a beam dump was built inside the Linac vault.

The electron source is a 90 kV triode gun with Pierce geometry. The socalled dispenser cathode is a porous tungsten matrix, impregnated with different oxydes like BaO, CaO and Al2O3. Applying a voltage pulse to the cathode with respect to the grid pulls the electrons from the cathode and accelerates them towards the anode, giving them an initial energy of 90 keV. After this electron gun the beam is bunched and further accelerated to 50 MeV by the first Linac structure. At this point the beam is refocused by a quadrupole triplett for optimal transmission through the second Linac structure, which brings the electrons to the final energy of 100 MeV.

More on the linac...