Microwave System for 20 MeV Microtron

A 20 MeV, 30 mA Microtron is used as electron injector for the booster of the synchrotron radiation facility, Indus-I and Indus-II. The microtron operates near 2856 MHz with type 2 cavity having coupling coefficient of the order of 2.62 which resonates in TM010 mode. A cylindrical pin made of lanthanum hexa Boride (LaB6) is used as electron emitter in this accelerator.

The microtron requires about 5 MW of pulsed power at about 2856 MHz. This power is provided by a single beam klystron driven by a S- Band pulsed power solid state amplifier. The source of frequency is a high stability frequency synthesizer. The pulsed beam power to klystron is provided by a line type pulse forming network based Modulator. The pulse forming network is a series of L-C network simulating a transmission line and it is charged using a stable constant current DC supply. A -110kV, 80A & 3us pulse is delivered to the cathode of klystron using a Thyratron tube and a Pulse transformer for the required klystron beam power.

The pulse width of the microwave power decides the duration of the electron beam. A RF switch has been inserted between the frequency synthesizer and the amplification chain which provides variable pulse width of Microwave Power. The electron beam width can be varied from 60 nanoseconds to 1 microsecond.

Wave Guide Feeding Power to Microtron via circulator Internal Microtron structure
High Power Klystron amplifier H.V. Modulator System
Solid State Amplifier
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