Electrons shine a new light at DESY

8 March 2000

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On Tuesday 22 February, 2000, a team at the TESLA Test Facility at the DESY laboratory in Hamburg observed the first lasing of the facility's free electron laser, and demonstrated for the first time that a free electron laser can produce wavelengths as short as 100 nanometres (nm) or so. TESLA (for TeV Energy Superconducting Linear Accelerator) is a proposed linear collider, designed to bring electron and positron beams head on at energies as high as 1 TeV (tera electronvolt). (This is 10 times the energies of the Large Electron Positron collider (LEP) at CERN.) However, the aim is to use the electron beam not only for the collider, but also in an X-ray laser which would be used to investigate physical, chemical and biological processes that take place on minute time and distance scales.

As a first step, the TESLA team at DESY have built a 300-m long superconducting accelerator to provide the electron beam for a free electron laser, which works by wiggling the electrons so that they emit tightly focussed light. The image shows the spectrum of light at about 109 nm wavelength, taken with a CCD camera. (View the variation of photon intensity with wavelength). The measurement was taken over 1 minute and is the sum of 60 photon pulses produced by 60 electron bunches. This is an important step towards producing an X-ray laser.

Credit: DESY / TESLA