Linac team has reached major milestones

Linac team has reached major milestones


A big milestone was reached for the MAX IV Linear Accelerator end of May. The electron bunches accelerated in the linac was compressed to a time duration below 100 femtoseconds (fs). That means that they were shorter than 1*10^-13s. In fact, we could measure a pulse duration as low as 65 fs FWHM.

While optimizing compression factor through scanning the off crest phase before the first bunch compressor in the MAX IV linac, a minimum value of 65 fs FWHM and 32 fs RMS was achieved.

The RMS bunch length was then recorded at 32 fs. These results were achieved using only the first of the 2 electron bunch compressors in the MAX IV linac and shows not only that we can deliver short electron bunches, but also that the novel concept adopted in the compressors is working according to theory and simulations.

The ultra-short electron pulses are used to create X-ray pulses with the same short time duration in the linac based light source SPF (Short Pulse Facility). These bursts of X-rays can then be used to make time resolved measurements on materials, meaning you can make a movie of how reactions happen between parts of a molecule.

The linac team has also been able to accelerate and compress two pulses on one RF wave, so called double pulses. One area where this will come in handy is when you would like to do a so called pumb-prob experiment (time-resolved spectroscopy) where both pulses comes from the accelerator (linac) instead of having the pump pulse coming from a laser. The bunch compressors in the linac at MAX IV is especially suited to produce this type of pulses. Which is quite unique in the world.

Image on the first screen in BC2, using the main linac and BC2 as a streak camera to measure bunch length, after compression in only BC1. Only lightly compressed, first attempt.
Projection in the x-direction of the image shows the longitudinal profile of the electron bunch.