ALICE detects spontaneous radiation from IR-FEL undulator
On 4 February 2010 ALICE detected spontaneous radiation emitted from the newly installed infra-red free electron laser (IR-FEL) undulator.
A 20 pico-Coulomb, 30 MeV electron beam was transported though the undulator. The cavity-type FEL reflects the 6 μm wavelength IR radiation from the beam backward and forward using mirrors, and the radiation is emitted through a hole in one of the mirrors where it is detected on a sensitive mercury-cadmium-telluride detector (see image). The size of the signal seen indicates that the radiation has reflected multiple times within the cavity.
This result represents another important step in achieving the goal of achieving lasing with the IR-FEL. In the coming weeks the ALICE electron beam and IR-FEL will be optimised to set the conditions required for lasing.
Oscilloscope trace showing spontaneous radiation signal from the IR-FEL detected by an infra-red detector. The negative going pulse is generated by the undulator radiation making multiple round trips within the laser cavity.
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