The MAX IV

1
The injector for the MAX IV
Åke Andersson, Marlene Bergqvist, Mathias
Brandin, Mikael Eriksson, Tue Hansen, Jörgen
Larsson, Lars-Johan Lindgren, Lars Malmgren,
Hamed Tarawneh, Erik Wallén and Sverker Werin,
MAX-lab and LLC, Lund University, Lund Sweden
Introduction
The MAX IV
Injector system
The duty of the injector is two-fold. Both the
operation as injector for the storage rings,
where at least the MAX IV will opeate in top-up
mode (very frequent injections, 1 shot /
minute), and driving the FEL system for coherent
radiation.
Electron gun PC RF-gun 3 GHz
3 GeV NC-Linac
90 m
The main linac system
The MAX 4 rings
The linac will be built of building blocks, where
each block consists of one 35 MW klystron, one
SLED system (see below) and two linac structures.
Each such station will be able to deliver 200 MeV
of energy to the beam. The linac will consist of
17 stations, where two will be back-up stations
standing on line.
Warm v super conducting
Klystron
A normal conducting (NC) system will be able to
operate at 100 Hz, due to power limitations.
Neither the klystrons nor the power dissipation
in the linac structures will allow a higher
frequency. A 100 Hz NC system for MAX IV will
require 1.5 MW. A way to increase the repetition
rate of the system would be to introduce Super
Conducting (SC) accelerators. These will probably
be able to run continuously (CW). The limitations
will then lie on both the electron gun and the
laser systems (for the guns and the seeding of
the FEL process). A SC system like the BESSY FEL
will need 5 MW for CW operation of the linacs but
will be limited by the seed lasers to 1KHz. The
cost for going from SC to NC is large in money
and complexity, while the practical gain in
repetition frequency is limited.
SLED
Gun and pre-injector The injector design starts
out from what has been designed for the LCLS. A 3
GHz photo cathode RF-gun with a 150 MeV pre
accelerator linac has been designed and
experience is alredy available for control of
space-charge, coherent synchrotron radiation and
wakefield effects on emittance and peak
current. The main demands will be set by the
operation for FEL.
SLED SLED (Stanford Linac Energy Doubler) is a
system which in principle doubles the possible
accelerated energy. This is done by two storage
cavities which are fed by the long klystron
pulse. By a phase switch the stored energy is
rapidly extracted from the cavities to the linac.
The result is a shorter pulse with much higher
peak power.
SC ? NC 5 MW ? 1.5 MW 1 KHz ? 100 Hz Complex ?
Ordinary ?
Experiences with the current MAX injector
A new injector system has been put into operation
at MAX-lab. It consists of a recirculated system
with two linac structures that will provide 125
MeV after full commissioning. Electron beams of
up to 380 MeV have been extracted to the MAX II.
Currently the system is beeing commissioned to
reach full energy.
Linac
3
1
2
SLED system
Example pulses of June 22, 2004