Electrons are emitted at the electron gun by the cathode which is either operated in the thermal or photo-electric effect mode. The thermal mode is used for storage ring injection while a short pulse laser is used to generate photo-electrons used for the FEL experiments.
After being pre-accelerated by the RF gun to 2 MeV, the electrons are then further accelerated by two linear accelerators (linacs), each having an energy gain of 100 MeV. The electron beam can then either be brought upwards to the MAX I storage ring or recirculated by two 1800 bending magnet structures for another acceleration in the linacs up to 400 MeV. These electrons are then injected into the MAX II or MAX III rings or used for a FEL experiment set up inside the MAX II ring.
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Final electron energy MeV)
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200, 400
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Pulse current (mA)@400 MeV
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50
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Pulse length@400 MeV
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50 ns
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Rep rate (Hz)
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0-10 Hz
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RF
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3 GHz
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The MAX Injector
Recirculator magnet block
The recirculating magnet structure consists of several magnets of different kinds; dipole, quadrupole and sextupole magnets. All these magnets are precision-machined out from solid iron blocks. Two such iron blocks form a 1800 achromatic and isochronous bending structure.
This unusual injector configuration with a recirculated electron beam is motivated by cost savings and the need to squeeze the injector into a small and narrow hall.
Below, we will describe the functioning of this magnet system. All positions refer to the left iron block.
After the first acceleration in the linacs, 200 MeV electrons will enter at the top left corner in the figure above. Two magnet lenses (quadrupole magnets) will focus the electron beam before it enters the first 450 bending magnet. The next quadrupole magnet will focus the electron beam to negative dispersion in the middle of the next 900 bending magnet. The electron optics is mirror-symmetric around this middle point, so the electrons will leave at the left lower side of the iron block.
