PHYS07200604007 Manas Kumar Dala - Homi Bhabha National ...

Experimental Techniques 50
exploration of matter. Synchrotron radiation are produced when charge particles
Figure 2.17: Schematic of the synchrotron radiation.
moving with relativistic velocity are deflected in a magnetic field. The synchrotron
radiation had been developed by taking the effect of Heinrich Hetz [1] as the electrons
fly around the curves through the magnetic field emit electromagnetic radiation. In
SR facilities the accelerated electrons fly in a closed orbit inside a stainless steel
tube, which consists of large electromagnets at regular intervals to guide the electrons
around the curves and keep them focussed in the center of the tube called the storage
ring. The electrons are generated in an injection system consisting of an electron
source and an accelerator, either a synchrotron or a linear accelerator. When the
electrons are accelerated to the operating energy of the storage ring, they are injected
into the storage ring. The bending magnets are used to deflect the electron beam.
In order to compensate the energy loss of the electrons during the SR emission, the
electrons are accelerated each time as they pass through the RF cavity installed inside
the storage ring. A schematic of SR light source is shown in the Fig. 2.17.
In the developed synchrotrons the intensity of the emitted radiation is enhanced
by insertion devices (undulator or wiggler). The insertion devices are periodic arrays
of permanent magnets. When electrons traverse in the periodic array of magnets are
forced to undergo oscillations and radiate (Fig. 2.18 shows the schematic representation).The
static magnetic field is alternating along the length of the insertion devices
with a wave length λ 0 . The radiation produced by insertion devices is very intense and
is guided through beam lines for various experiments. An important dimensionless
parameter K which characterizes the nature of electron motion is defined as,