650 MHz Solid State RF Power development at RRCAT Indian Institutions and Fermi lab Interaction Meeting P. R. Hannurkar, Akhilesh Jain, M. R. Lad RF Systems Division RRCAT, Indore

RF Systems RD & D RF Systems division, RRCAT is responsible for the design and development of RF systems for particle accelerators. It includes – High power amplifiers based on tetrodes, klystrons, IOTs and transistors Low level RF control and interlocks High voltage DC power supplies and Engineering design of coaxial and waveguide based RF components. Systems for Indus-1 and Indus-2 synchrotron radiation sources have been successfully commissioned. IOT based amplifier for Indus-2 upgrade is under progress. Development of solid state amplifiers operating at 505.8 MHz for Indus-2 is in progress. Two units of 15 kW solid state amplifiers commissioned recently. Technology development to reach 60-80 kW RF power level is in progress. Work on 30 kW 650 MHz solid state amplifiers for powering SCRF cavities, has been initiated.

Solid State Amplifier Experience RD & D in RRCAT 1 kW Solid State RF Amplifier for Booster Synchrotron 2 Nos SSPA at 15 kW, 505.8 MHz operational in Indus-2 SRS 4 kW, 352 MHz SSPA as test stand 2kW (pulse), 352 MHz SSPA 650 MHz RF Amplifier module and associated RF components Technology has been established for Power Divider, combiner, Amplifier modules, Directional couplers, LLRF, and RF dummy loads - all needed for making a complete system.

1 kW Solid State RF Amplifier for Booster Synchrotron Tetrode Tube based RF Amplifier has been replaced by 1 kW Solid State Amplifier for Booster Synchrotron. This has resulted in the improved performance. Frequency 31.6 MHz Output Power 1 kW Mode of Operation CW Gain 55 dB Harmonics -45 dBc Efficiency 48 % Gain characteristics of 1kW RF amplifiers 250 W RF Amplifier Module 1kW RF Amplifier

Indus-2 RF System Modular RF system at 505.8 MHz 1500 kV cavity gap voltage. 64 kW Multi beam Klystrons RF Transmitters

15 kW Amplifier 15 kW Amplifier commissioned in Indus-2 SRS Two 15kW SSPA have been built and deployed in Indus-2 to energize RF cavities. With addition of these amplifiers, 100 mA at 2.3GeV was achieved.

8 kW Solid State Amplifier Scheme for Indus-2 8kW unit is housed in a single euro rack with 32 amplifier modules of 320W RF power To cater immediate requirement in Indus-2 accelerator , development of 60kW solid state amplifier is under progress at 505.8 MHz. As a part of this project, two units of 8kW RF amplifier have been developed and tested successfully. 8 kW Solid State Amplifier architecture 8 kW, 505.8 MHz Solid State Amplifier

505.8 MHz 320W RF Amplifier RF PA module, operating at 320 W, with 28V DC bias, is workhorse for 8 kW amplifiers. specifications are listed below. Sr. Parameter Value 1 Rated RF Power Output 320 W 2 Operating frequency and 1 dB Bandwidth 505.8 MHz, ± 5 MHz 3 Power Output @ 1db Compression 300 W 4 Operating Mode/ Class of operation CW/ AB 5 Power Gain 15 dB 6 Input and output Impedance 50  7 Power Added Efficiency 50 % 8 Harmonic Distortion -30 dBc 9 Spurious Output -35 dBc 10 Input VSWR 1.2 11 Cooling Water Cooled Additional Specifications for 8 kW Amplifier Sr. Parameter Value 1 Controls System Enable, System ON/OFF, RF ON/OFF, system Shutdown, Emergency Trip 2 Front Panel Meter Forward & Reflected Powers, System & alarm status 3 Primary Power 300-415V, 47-63Hz, 3 Phase 4 External Protection Excessive Reflection, over temperature, overdrive

Indus-2 60 kW Design Scheme Scheme for 60 kW solid state amplifier - 30 kW RF power will be obtained by summing output of four 8 kW units. Two 30 kW will be combined to get 60 kW RF power.

InPAC - 2011, IUAC, New Delhi Feb 15-18, 2011 RF Power Combiners Using radial topology, novel 8-way and 16-way combiners, operating at 352, 505.8 and 704 MHz have been developed. Successful experimental work encouraged to develop 15 and 20 kW 2-way structure. 2kW 8- way combiners at 352, 505.8 and 704 MHz 4kW 16- way Unit at 352 MHz 15kW 2- way combiner at 650 MHz -> Work published in Rev of Sci Instru, Jan 2009 InPAC - 2011, IUAC, New Delhi Feb 15-18, 2011

Rigid coaxial transmission line Power combiners 16-way 4kW Power combiner 2-way 20 kW Power combiner All power combiners are made up of silver coated brass material. Output power is taken from 1-5/8”, 3-1/8” and 6-1/8” coaxial lines respectively in 4 kW, 20 kW and 40 kW combiners. 2-way 40 kW Power combiner

Wide-Band Directional Couplers 4 kW 1 kW 20 kW Directional couplers are useful for measurement of forward and reflected RF power. Three types of directional couplers with different power handling capacity viz. 1 kW, 4 kW and 20 kW have been designed and tested. 1 kW coupler is very compact having length 70 mm. 4 kW coupler is 200mm and 20 kW is 320 mm long. All three items have been made of silver coated brass material.

2kW Pulse Solid State Amplifiers 200W and 2kW pulse Solid State Amplifier Developed for H- LINAC at 352MHz are shown here. 200W (peak) Amplifier at 352 MHz Power (P1dB): 2kW Pulse Power Gain: 60 dB Pulse Width : 500 µsec Pulse Repetition Freq. : 25 Hz 2kW (pulse) Solid State Amplifier at 352 MHz

352 MHz Solid State Amplifiers 4kW level Solid State Amplifier at 352 and 8kW amplifier with High power 16-way radial power divider, combiner, 2-way combiner and directional coupler, developed in-house, are shown here. 4kW Solid State Amplifier at 352 MHz Power Gain: 50-55 dB Pulse power: 5kW at 3% DF 8kW Solid State Amplifiers at 352 MHz Power (P1dB): 8kW CW Power Gain: 63 dB Measured Power transfer Performance of 4kW Amplifier at 352 MHz Measured Gain, power and efficiency distribution of individual Amplifier modules used in 4kW Unit Inset showing High power 16-way radial power divider, combiner, 2-way combiner and directional coupler

650 MHz RF System Requirement -for powering two cavities viz. LB-650 (beta=0.61) and HB-650 (beta=0.9) in the energy range of 160-2000 MeV. Output power ~ 25-30 kW for each type of cavity Possible choice- IOT or Solid state based amplifier For this power regime, Solid state RF amplifier seems better candidate as RF power source, due to many advantages.

200 W module at 650 MHz At 650 MHz, 200W module is developed. Design studies and simulation have been carried out using Newer LDMOS device, operating at 50V to obtain 350 W. Its PCB layout design and prototyping is under progress. 200 W solid state amplifier with measured power

650 MHz RF Components Developed at RRCAT 20W Low Power Driver 2-way 8 kW and 18kW Power combiners Output : 3-1/8” EIA 200 W Amplifier Module Gain: 13 dB VSWR: 1.1 P1dB: 200W Coaxial Transitions 3-1/8” EIA to 1-5/8” EIA 1-5/8” EIA to N Type 1 kW 4 kW 16-way 4kW Power combiner Output : 1-5/8” EIA 20 kW 30kW, 80kW and 200kW RF Dummy Loads DC to 800 MHz, VSWR: 1.1, Water cooled Wide-Band Directional Couplers

Proposed Design Scheme 1 N=16 8kW Unit scheme used in 30kW Amplifier 1 2 31 32 Driver 350W modules + RF Generator 16 17 4 30 kW RF Generator Driver 8 kW Units 30kW Amplifier Scheme + 2 3 8 kW 4 kW Proposed scheme for 30kW solid state amplifier - 30kW power will be obtained by summing output of four 8kW units. 8kW unit will be housed in a single euro rack with 32 amplifier modules, each one using LDMOS giving output around 350 W. Complete system consists of various blocks.

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