A+ A A-

Pulsed diode accelerator

 

 

Construction of Pulsed Accelerator KALI-5000:

There are various devices to generate the high voltage pulses but the most popular technique is the Marx generator in which energy storage capacitors are charged in parallel and discharged through synchronized spark gap switching in series resulting in enhanced voltage and power [3]. Once the voltage pulse is generated, it is required to shape them into a flat top type so that when it is injected into the electron gun, the same energy beam will be emitted during that time span. With this flat top pulse as input, the electron gun produces the pulsed electron beam, which can be used for various applications.

 

The schematic of this pulsed electron beam accelerator is presented in Fig.2. It is comprised of a high voltage ± 50 kV DC charging power supply followed by an impulse generator based on a plus-minus charging type Marx generator. The output pulse is shaped through a Blumlein type pulse forming line and terminated across a field emission type electron gun. The whole assembly has been put on rails for ease in assembly and maintenance point of view.

Marx Generator

1 MV, 12 Ohm Castor Oil Blumlein

In a pulse power system, a transmission line could be defined as a power amplifier, which receives the energy to be stored at the low average power over a long period of time and delivers the stored energy at the high average power over a short period of time. The transmission line could take one of the numerous well-known geometries like two-electrode simple pulse forming line in stripline or coaxial geometry, five electrode Blumlein line in strip-line geometry, or stacked configuration of simple or Blumlein lines. The dielectric could be (a) solids like polyethylene or Mylar impregnated with oil, water, or CuSO4 solution, or (b) liquids like transformer oil, castor oil, de-ionized water, or glycerin. The transmission line in the present pulse power system is a three-electrode coaxial Blumline with castor oil as the dielectric. When the Marx generator is triggered and erected, the resulting stepped-up voltage then charges the Blumlein to a peak voltage Vp, where further shaping of the pulse takes place. Pulsed charging of this line enables to make the system compact. When the PFL is charged to the voltage corresponding to the preset breakdown voltage of SF6 spark gap S2, it breaks down & discharges the stored energy into a matched dummy CuSO4 load of 17 W for testing purposes or into a beam diode for the generation of the relativistic electron beam (REB). Reversing the polarity of the HVDC supply can reverse the polarity of the output pulse.