DAY 6 – CAMPing at world’s most brilliant light source

Exploring a terra incognita

May 7 2010

Free Electron Lasers (FEL) produce ultra-intense and ultra-short pulses of UV or X-ray light. In terms of brilliance – which is a measure how intense, well focused and how low the energy spread of the pulsed laser beam is – the new FELs exceed existing sources like synchrotrons by a factor of up to one billion. “New tools create new science” is the motto of the Linear Coherent Light Source (LCLS) for X-rays at Stanford Linear Accelerator Center (SLAC). Another FEL for UV light (FLASH) is operational since 2005 at DESY in Hamburg. The next generation there (X-FEL) is under construction.

A few words about the principle of a free electron laser: A bunch of high-energy electrons from an accelerator travelling almost with the speed of light enters a structure of alternating magnetic fields – a so-called undulator. The wiggling electrons change periodically their velocity direction and form an accelerated charge which – according to the laws of electrodynamics – emits electromagnetic waves, i.e. light. Due to the relativistic speed of the electrons, the radiation is transformed into UV or X-ray light. Furthermore, the electron bunch becomes micro-structured on the wavelength of the radiation. This effect, called “Self-Amplified Spontaneous Emission” (SASE) leads to a coherent amplification of the light intensity which scales with the number of electrons squared.

Principle of an FEL with SASE.

Exploring the “terra incognita” asks for advanced detection instrumentation. One example is the newly developed CFEL ASG Multi-Purpose Chamber CAMP – designed and built by the Advanced Study Group (ASG) of the Max Planck Society at the Center for Free-Electron Laser Science (CFEL). It combines a spectrometer for charged particles (electrons, ions) with world’s largest X-ray CCD chips developed by the Max Planck Semiconductor Laboratory. Pioneering first studies started in November/December 2009. Currently 8 new experiments are under way using the new apparatus. I wish all the participating scientists a successful campaign!

CAMP apparatus in operation at LCLS (Stanford).

And the evening and the morning were the sixth day.


One Response to “DAY 6 – CAMPing at world’s most brilliant light source”

  1. Li Hua Yu Says:

    Dear Sir,

    I am writting a chapter for FEL in a book about synchrtron radiation facilities. In searching through websites, I saw your plot about SASE principle. I hope to use your figure as an illustration for SASE.

    I will appreciate it very much if I can get your permission to use your figure.

    Best Regards

    Li Hua Yu

    Senior Physicist
    NSLSII, Brookhaven National Laboratory

    Upton, NY11973

    Telephone number: 631-344-5012

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