Solid State RF Amplifiers

Pulsed and CW Solid State RF amplifiers at different frequencies ranging from VHF to S band like at 31.613 MHz ,325 MHz, 476 MHz, 505.8 MHz,650 MHz,1.3 GHz and 2.856 GHz are designed and developed indigenously at RRCAT. Few are covered above and remaining developments are as follows.

a) 36 kW Solid State RF amplifier at 650 MHz for HTS

For high power testing of SC RF cavity HTS cryostat is installed at HTS facility. A 36 kW, 650 MHz Solid State RF (SSRF) amplifier system has been designed ,developed and installed in HTS facility along with indigenously built 40 kW high power 650 MHz RF circulator to test and qualify SC RF cavities in HTS. Several of such amplifiers and amplifiers of RF power 70 kW will be constructed for in kind contribution to Fermilab USA under IIFC collaboration activity.

Fig.11:650 MHz solid-state RF amplifier

b) 150kW 325 MHz Solid State RF amplifier for RFQ

The RRCAT is engaged in research and development efforts towards Indian facility for spallation source. As part of these efforts, the development of a Radio Frequency Quadrupole is under progress. This quadrupole will be powered by four solid state amplifiers, operating at central frequency of 325 MHz. Each amplifier’s output power will be 150 kW with variable pulse width from 1 ms to 5 ms, and up to 50 Hz of pulse repletion rate. This 150-kW amplifier is made up of three 50 kW units.

Fig.12 : 150 kW, 325 MHz solid-state RF amplifier

The main features of this amplifier are its modular and scalable design architecture using in-house designed amplifier modules, two-tier radial dividers, combiners and aperture coupled directional couplers.

With the use of Superconducting cavity, Solid State Radio Frequency Amplifiers (SSRFA) are being considered for an increasing number of accelerator applications, both circular and linear, in kW level RF power regime. Their capabilities extend from a few kW to several hundred kW, and from few MHz to above 1 GHz. It has drawn a considerable attention with the advent of SCRF cavity. Solid state device based RF source enjoys extreme modularity, simple maintenance, redundant design, and absence of high voltage power supply, easier maintenance, no warm up time, lower cost and simple start-up procedures. At RRCAT, SSRFA related activities were started for Indus-1 and Indus-2 RF systems.

c) S- Band SSRFA Development

Different S-Band high power amplifiers of up to 2 kW power, 20 µs pulse width and 400 Hz PRR are developed. These in-house developed amplifiers feature high amplitude stability and are rugged & reliable.

Fig. 13: 1 kW indigenous S-Band amplifier

d) Compact high-power pulsed amplifiers at 476 MHz and 499.75 MHz

Pulsed solid-state amplifiers of 10 kW and 20 kW at 476MHz and 499.75 MHz respectively have been developed. These amplifiers have a compact design. The images are shown below. The 10 kW amplifiers energize the sub harmonic pre-buncher cavities of IRFEL. The 20 kW amplifier was delivered to CERN for CLIC facility under DAE CERN collaboration.

Fig. 14: 20 kW 499.75 MHz pulsed SSPA

e) High Power Passive Coaxial Line Components

Coaxial passive components, 40 port divider-combiner, High-power 3-way combiner, directional couplers, and phase shifter were designed and developed indigenously at RRCAT. After baseline design calculation; optimization/tuning and full-wave electromagnetic (EM) analysis was carried out.

Fig. 15: 2-way combiners, 16-way and 40 way radial divider/combiners

Fig. 16: 3-way high power RF combiner	Fig. 17: 1 kW directional coupler and sensor

Fig. 18: High Power Directional Power Couplers