ipr-fel

The IPR-FEL

The IPR-FEL experiment was initiated in the early '90's and was enivisaged to look into the possibilities of using the FEL generated high power millimeter waves for Tokamak plasma heating applications.

The relativistic electron beam source is based on a Tesla transformer-pulse forming line type of accelerator and a field emission diode emitter. A Sheet electron beam configuration has been choosen for this experiment in order to enable the beam to carry the maximum current density keeping the wiggler gap minimal. The schematic of the REB-FEL system is shown below.

REB Type	Tesla Transformer
Transformer ratio	25
Pulse forming line	Water-filled co-axial
Beam Voltage	100-300 kV
Beam Current	50-150 Amperes
Pulse width	100-150 nsec
REB Capacitor bank	2.5 kJ @ 30 kV
REB Power Supply	50 kV @ 20 mA

The wavelength ranges expected to be accessed with the 50 period electromagnetic wiggler as well as the 15-period permanent magnet wiggler range from 70-90 GHz ( For EM wiggler ) and 7-25 GHz (For PM wiggler ) using the EM and permanent magnet wiggler at 100keV energy respectively.

In order to make sure that the electrons entering the wiggler sees the peak of the magnetic field, a low-jitter trigger synchronization circuit was designed and is being used on a routein basis. The synchronization of the REB and wiggler current pulses can be seen in this figure .

To detect the FEL radiation, an array of mm wave detectors ranging from 60-140 GHz. The experimental setup for the detection of FEL microwave radiation is shown here.