Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–83

Contents lists available at SciVerse ScienceDirect

Nuclear Instruments and Methods inPhysics Research A

0168-90

doi:10.1

n Corr

E-m

journal homepage: www.elsevier.com/locate/nima

Modular 20 kW solid state RF amplifier for Indus-2 syncrotronradiation source

Akhilesh Jain n, P.R. Hannurkar, D.K. Sharma, A.K. Gupta, A.K. Tiwari, M. Lad, R. Kumar,M.K. Badapanda, P.D. Gupta

Raja Ramanna Centre for Advanced Technology, RRCAT, Indore 452013, India

a r t i c l e i n f o

Article history:

Received 24 January 2012

Received in revised form

17 February 2012

Accepted 17 February 2012Available online 27 February 2012

Keywords:

RF amplifier

Solid state amplifier

Power combiner and divider

Directional coupler

02/$ - see front matter & 2012 Elsevier B.V. A

016/j.nima.2012.02.023

esponding author.

ail address: ajain@rrcat.gov.in (A. Jain).

a b s t r a c t

This article presents the design and development of 505.8 MHz modular solid state Radio frequency

(RF) amplifier capable of delivering 20 kW continuous RF power. It has been successfully commissioned

for serving as the modern RF power source in Indus-2 synchrotron radiation source. For this amplifier,

design procedure has been formulated for the solid state amplifier modules, radial combiner, divider,

directional coupler and overall system architecture, with specifications suited to RF source for particle

accelerator. This article describes underlying design principles and indigenous development of this

amplifier, consisting of 400 W amplifier modules, 5 kW 16-port radial combiner/divider and directional

couplers. Detail performance characterization of amplifier on component level as well as system level

serves as useful data for higher power solid state amplifier designers. Simple design, indigenous

technology, high efficiency and ease of fabrication, are the main features of this design.

& 2012 Elsevier B.V. All rights reserved.

1. Introduction

Few years back, utility of Solid State Power Amplifier (SSPA), atRadio frequency, was limited to driver amplifier [1], providingfew hundreds of watts, for driving vacuum tube amplifiers. Now,with the availability of powerful RF transistors, many particleaccelerator laboratories around the world have harnessed thepower of solid-state RF technology, by deploying RF power sourcefor large accelerators like synchrotrons [2] and high intensityproton linacs [3,4]. ESRF is on the wheels for replacing its 1 MWklystron based source with SSPA [5]. Numerous advantages [6,7]of SSPA, compared to vacuum tube counterpart, is the maindriving force behind rapid development of kW level SSPA. Alongwith getting clean RFM power (free from phase noise andspurious) solid state device failure rate reported from Soleil is3% per year including infant mortality. This is a desired feature [8]expected from RF source deployed for Spallation neutron source(SNS) and accelerator driven systems (ADS). As stated recently [9]price, performance and reliability of semiconductor based RFsource is quite likely to improve with evolution of 6th and 8thgeneration of LDMOS RF transistor technology.

The Indus Accelerator complex [10] at RRCAT consists of Indus-1(a 100 mA, 450 MeV storage ring) and Indus-2 (a 2.5 GeV storagering), sharing a common injector system, comprising of 20 MeV

ll rights reserved.

microtron and 700 MeV booster synchrotron. Indus-1 provides abroad electromagnetic spectrum extending from far infrared to softX-ray region while Indus-2 has critical wavelength in hard X-raysrange. Indus-2 RF power system [11] was designed and builtusing four Klystron based RF stations, each delivering 60 kW at505.8 MHz, making up total installed capacity of 240 kW of RFpower. Due to uncertainty in getting Klystron tubes, it was proposedto develop alternate high power RF source using solid state RFtechnology at 505.8 MHz [12]. In this direction, initially, 15 kWSSPAs [13] were developed successfully. Following this activity,20 kW SSPA has been designed and commissioned. These SSPAswere used to power RF cavities of Indus-2 synchrotron radiationsource. With addition of these amplifiers and optimization of RFsystem operating parameters, beam energy was enhanced. Thistechnology development is very useful to build high power RFamplifiers for proton LINACs for SNS and ADS applications, in future.

Due to moderate power output of semiconductor devices, largenumbers of Power Amplifier (PA) module are paralleled in makinga typical kW level RF power source [14]. In architecture of suchsource, due to divide, amplify and combine strategy, PAs aresynchronized together in amplitude and phase for maximumpossible combining efficiency. Power division and summingaction is achieved by power divider (PD) and power combiner(PC). All of the PAs, which are main gain blocks, cannot beidentical due to fabrication tolerances and impedance tuning, sothe output signals from the amplifiers feeding combiner will varyin amplitude and phase. For in-phase even mode combiner, suchvariation will reduce combining performance and thus overall

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–83 75

system efficiency. SSPA designers have tried different methodslike phase delay line [15] and forced compression of draincharacteristics [16] in order to synchronize amplitude and phaseof PAs. In order to tightly control this variation, design of PA andcombiner/divider are important and attraction of analysis indeciding final output power and efficiency of the system. In viewof this, design topology for PA and combiner/divider has beenselected so as to favor repeatable and indigenous developmentwith least amplitude and phase variation.

In this paper design methodology of various RF componentsused for making a complete 20 kW SSPA at 505.8 MHz is describedalong with high power continuous wave (CW) RF testing results.Experimental data with real time reflection, phase and amplitudebalance are very useful for studying power efficiency. This exerciseprovided useful data of performance evaluation, life testing andgraceful degradation for research community associated withhigher power solid state amplifiers.

2. Design description

20 kW SSPA has been materialized as scalable and modularcombination of two similar 10 kW amplifiers. Based on literaturestudies and component selection, simplified architecture designedfor 10 kW amplifiers is shown in Fig. 1.

Fig. 1. 10 kW Solid state RF

This consists of 32 PA (each one at 400 W) modules powercombined in two stages. In the first stage there are two similargroups each one having 16 PAs which are combined using 16-portcombiner. In second stage 5 kW outputs from two such groups arecombined with the help of a 2-port combiner to get required10 kW power. A 16-port divider splits about 300 W to feed all theinputs of 16 PAs in each group. A 2-port splitter divides signalpower to feed 16 port dividers of each group. A phase shifterinserted in one of the groups adjusts real time operational phasedifference. A low power directional coupler inserted betweenoutput of each PA and input of 16-port combiner monitor forwardand reflected RF component. Similarly 5 kW and 10 kW direc-tional couplers are used to sample RF powers at each stage.

Two such 10 kW amplifiers give, 20 kW of output power afterpower combining with the help of a 20 kW two-port combiner. Asevident, each 10 kW amplifier employs 32 numbers of 400 W PAmodules, two 16-port power dividers, two 16-port power combi-ners, one 2-port combiner and 5 kW and 10 kW directionalcouplers. All these components are described in detail below.

2.1. The RF amplifier module

As evident from amplifier hardware architecture above, 400 WRF PA modules are workhorse for amplification of RF power. Henceits design requires efforts to achieve best possible efficiency, stable

amplifier architecture.

Table 1Specification of 400 W RF power modules.

Sr. Parameter Value

1 Rated RF power output/power gain 400 W/18 dB

2 Operating frequency and 1 dB

bandwidth

505.8 MHz, 75 MHz

3 Operating mode/class of

operation/efficiency

CW/AB/58%

4 Protection VSWR, over temperature,

overdrive

5 Harmonic distortion/spurious output �30 dBc/�35 dBc

6 Cooling Water cooled at 30 1C

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–8376

operating point and minimum distortions like AM–AM andAM–PM, apart from achieving regular design specifications. ForPA design, based on load-line matching condition or power matchcondition [17] and impedance matching design [18], BLF 573LDMOS was selected to serve as an active device. As per datasheet this device is capable of providing 300 W at 230 MHz and50 V DC bias. Based on power vs. frequency roll-off simulationstudies, carried out in Microwave OfficeTM, 260 W output power at505.8 MHz was estimated for this device. Hence in order to get400 W power, two such devices, designed with impedance match-ing and class AB bias circuit, were paralleled with the help of semi-rigid coaxial transmission line based Wilkinson divider andcombiner. In order to match gate and drain side impedances (bothare having real part less than 2 O) to system impedance of 50 O,coaxial transformers were selected as basic impedance matchingunit in addition to L section of lumped capacitors and microstripline. Fig. 2 shows bias and impedance matching circuit of one halfof PA without Wilkinson divider, combiner and circulator.

At input side combination of two 4:1 transformers were used.On output side one 9:1 transformer was selected, keeping mini-mum number of components, so as to minimize componentlosses. For energizing RF cavities, bandwidth of the order of1–2% is sufficient. Selected circuit topology serves the purposeof impedance transformation in designated bandwidth. PA circuitlayout was generated and printed on RF board (TMM 4) withrelative permittivity of 4.5. Simulation results were furtherimproved by operating module at different gate voltages andtesting its effect on gain and power conversion efficiency. A400 W circulator (from RF & Noise Components Ltd. with inser-tion loss of 0.2 dB), placed before final output, protect the RFdevices from reflected power. With reference to Fig. 2 thepotentiometer P1 sets the optimum operating point (quiescentpoint) which, for this transistor, is given by a drain current ofaround 900 mA. Amplitude and phase synchronization is requiredfor combining all PA modules in divide and combine strategy usedfor SSPA, as discussed earlier. This tuning of each module is donewith the help of capacitors (C1, C5, C13 and C14).

Important design specifications of this PA are listed in Table 1.Finally these modules were fully characterized by RF test

bench including RF instruments and data acquisition controller.Five such amplifier boards were mounted directly on a watercooled copper heat-sink measuring 40 by 25 cm. This schemeallows sitting of LDMOS devices directly over this heat-sink,

Fig. 2. Impedance matching circuit for o

improving thermal performance of PAs. Minute air gaps betweentop of the heat-sink surface and bottom of LDMOS metal flangewere removed by applying thin layer of Silicone oil based thermalcompound having thermal resistance of only 0.05 1C/W (for a25 mm thick layer with area of 4 cm2). Fig. 3 shows one heat sinkwith PA modules and inner view of one of the modules.

For one of the modules, various RF parameters measured areshown in Figs. 4 and 5. Each module was tested up to 500 W. Dueto excessive temperature (nearly 160 1C) of ATC capacitors, nearto drain of LDMOS, module operation was restricted up to 400 W.Power transfer characteristic is linear, however efficiency andinput return loss are lower than calculated values. Relative phasespread of this module is 121 for an output power excursion from200 W to 500 W. From this data AM to PM conversion wasmeasured as 21/dB, centered at an input power of 38 dBm andan output power of 56 dBm. In real amplifier, AM to PM conver-sion gives an idea about the shifting of phase delay (gain phase) inresponse to the signal level change.

Measured amplitude and phase distribution of 32 modules tobe used in a 10 kW SSPA are shown in Fig. 6. This measurementof phase and amplitude imbalance is important in decidingcombining losses of the system. This imbalance disturbs desiredexcitation mode for combiner (even mode in case of in-phasecombiner). Deviation from desired EM mode sets up impedancemismatch at PA output and combiner input interface. Thismismatch and finite isolation of combiner result in reflectedpower going back to PA. This reflection apart from setting upinstability in the system reduces overall efficiency. In the presentcase amplitude scatter is quite low (o0.3 dB) while maximum

ne half of the 400 W power module.

Fig. 3. PA module heat-sink with inner view of PA module.

Fig. 4. Measured gain and efficiency of 400 W PA module.

Fig. 5. Measured return loss and phase variation of 400 W PA module.

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–83 77

phase scattering is nearly 201. York [19] characterized this effectand concluded that multi-way combiner systems can toleratesignificant amplitude errors as long as they have zero mean, butphase errors are particularly significant.

2.2. High power rigid system components

As evident from discussion about SSPA configuration, powercombiner and dividers are important part of the system and their

Fig. 6. Measured amplitude and phase distribution of 32 PA modules.

Table 2Rigid coaxial components designed for 20 kW SSPA.

Sr. Item RF interface Quantity for 20 kW SSPA

1 5 kW, 16-Port radial line power divider Input—N female, Output—N female 4

2 5 kW, 16-Port radial line power combiner Input—N female, Output—1-5/8 in. EIA flange 4

3 12 kW, 2 Port combiner Input—1-5/8 in. EIA Output—3-1/8 in. EIA flange 2

4 20 kW, 2 Port combiner Input—3–1/8 in. EIA, Output—3–1/8 in. EIA flange 1

5 1 kW Directional coupler N female 64

6 5 kW Directional coupler 1-5/8 in. EIA flange 2

7 20 kW Bi-directional coupler 3-1/8 in. EIA flange 1

Fig. 7. 2 port combiner for 20 kW power combining.

Fig. 8. 5 kW, 16 port radial combiner.

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–8378

design plays a vital role in deciding final output power andefficiency. Similarly low and high power directional couplers arenecessary for using as test points or power measurement. Differ-ent rigid coaxial components, as detailed in Table 2, have beendesigned for 20 kW SSPA.

2.2.1. Power dividers and combiners

Among other available combiner topologies, radial powercombiners [20] offer a superior approach to high order, reliableand high power combining in a compact housing. By their nature,they tend to be efficient for summing a large number of ampli-fiers. 2-port combiner is a junction of three ports. Fig. 7 showsdeveloped 20 kW combiner with two ports. 12 kW combiner issimilar except 1-5/8 in. EIA flange as input ports and reduced size.However, 16-port combiner (Fig. 8) designed for present require-ment is an (Nþ1) ports’ junction endowed with rotationalsymmetric N branch ports and rigid structure with respect tothe feed port.

Similar structure acts as a power divider with role of feed portand branch ports reversed. Designed procedure is similar to oneoutlined in [21]. The launcher or feed section is a cascadedstructure of coaxial lines, feeding radial transmission line at oneend and designed for 50 O at the other end. The combiningpath (the radial line) is a low loss parallel plate slab-line typetransmission disk structure, with a central point excitation of feedline. Peripheral ports are located opposite and parallel to feedport, near the circumference of combining path (disk). Designequation includes value of relative input impedance Z0(r) [22] andreal value of characteristic impedance of radial line at radius r fordominant E mode is given as

Z0ðrÞffipkr

2þ jkr for kr51 ð1Þ

Z0ðrÞ ¼ðb�tÞ

8prZTEM ð2Þ

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–83 79

ZTEM is given as

ZTEM ¼120pffiffiffiffi

erp ð3Þ

Here k is the wave number and value of g is 1.781. Here b is thedistance between ground planes of slab line and t is the thicknessof metallic disk of this slab line. (er) is the relative permittivity ofdielectric filled around metal disk.

Using this approach initial design of the 16-port combiners anddividers has been carried out. This design methodology togetherwith full wave analysis in HFSSTM results in accurate prediction foroperating parameters and optimiztion of Electromagnetic struc-tures. All of these fabricated structures were impedance tuned andoptimized for high power and compactness. Realized with goodmechanical and thermal design, these structures provide anexcellent electrical symmetry for power combiners thus improvingtheir amplitude and phase stability.

Fig. 9. Measured return loss and i

For total 8 units of 16-port combiners low power and highpower RF measurements have been performed. Worst case returnloss was better than 25 dB, while insertion loss was less than0.05 dB, corresponding to combining efficiency of 99%. Measuredfrequency characteristics and isolation among branch ports aregiven in Fig. 9. Isolation calculated from HFSS is also shown forcomparison. For criteria of 20 dB as acceptable return loss,bandwidth is nearly 50 MHz.

Imbalance in coupling from feed port to branch port is lessthan 0.3 dB in amplitude and nearly 51 in phase. Due to circulargeometry of RF dividing/combining path in PDC, isolation isfolding itself around measurement port 1 (Fig. 10).

2.2.2. Directional couplers

For directional sampling and measurement of high RF powercoaxial directional couplers are the reliable high-power solution

solation of 16-port combiner.

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–8380

when bandwidth specifications are not critical. Selected couplerstructure is coaxial with rectangular cross-section. Couplingmechanism is similar to the one suggested by Tepatti et al. [23]where a thin metal diaphragm with a properly shaped aperturehas been inserted between the two cylindrical rods forming innerconductors of longitudinal symmetric main and auxiliary coaxiallines of square cross-section. Aperture shape is corresponding tothe desired longitudinal profile of the coupling factor. In presentstructure, auxiliary line has been implemented as suspended stripline. The necessary analysis, carried out in parts for longitudinaland transversal problems, provide the coupling factor and thecharacteristic impedances as functions of the structure dimen-sions. For transversal part, use of even and odd mode impedances(Zoe and Zoo) [24] was made for such uniformly coupled asym-metric lines.

kðzÞ ¼ZoeðzÞ�ZooðzÞ

ZoeðzÞþZooðzÞð4Þ

Here k(z) is the coupling factor. The longitudinal design procedureadopted was based on following equations [25].

A13 ¼ j2p l

l

Z l

0kðzÞe�4pðl=lÞzdz ð5Þ

Fig. 10. Calculated and measured coupling (from feed or combined port to branch

port) of 16-port combiner.

Fig. 11. 1 kW, 5 kW and 20 k

Here A13 is the voltage coupling from main port to coupled port, l

is the length of the coupler and l is the wavelength. With properchoice of various dimensions, final design was carried out usingstructure simulator. Absence of any printed circuit structure andrequired mechanical tolerances of the order of 0.1 mm allow low-cost couplers with excellent repeatability. Using this approach,three types of wide band (300–700 MHz) couplers (Table 2) havebeen built and characterized (Fig. 11) for maximum forwardpower of 1 kW, 5 kW and 20 kW respectively. Measurementresults show very good agreement with the design specificationsand electromagnetic simulations as compared in Table 3. Mea-sured insertion loss for both of these couplers is less than 0.05 dB.Return loss is better than 28 dB at 505.8 MHz.

2.3. Power supply and data acquisition

In the present scheme, every 400 W PA module is powered bya dedicated and compact switched mode power supply (SMPS)capable of delivering 20 A at 48 V DC with 3 phase AC input. TheSMPS can deliver up to 1000 W to the RF amplifier module andalso allow the power supply voltage to be set from 46 to 50 V. Fordata acquisition, 10 kW amplifier together with its interlocksform an independent system with its own local monitoring anddata acquisition system performed by a graphical code developedin-house [26] using LabViewTM RT. All of the PAs, with the help of1 kW coupler connected externally at output, provide rectifiedsample of forward and reflected power to FPGA based CRio analogmodules from National Instruments. Developed FPGA logic isresponsible for fast decision based on interlock status fed todigital modules of CRio. An industrial Panel PC, communicatingusing TCP/IP network, serves as a ‘master’ of this distributed DAQnetwork. It runs human machine interface program, developedin-house. The whole system works as a complete distributedsystem where all 10 kW units function independently and arecentrally coordinated by a master. The parameters acquired fromeach module are output forward and reflected power, and heat

W directional couplers.

Table 3Coupling and directivity of designed directional couplers.

Directional

coupler type

(kW)

Calculated

(HFSS) coupling

(dB)

Measured

coupling

(dB)

Calculated

(HFSS)

directivity (dB)

Measured

directivity

(dB)

1 40 41 30 29

5 50 51 28 24

20 50 49.3 28 23

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–83 81

sink temperature. Other analog and digital I/Os are used tomeasure external parameters such as water flow, rigid linecomponents’ temperature, panel status, etc. The system can beeasily expanded by adding new members to this TCP/IP networkin order to expand DAQ for additional 10 kW RF power units.

2.3.1. Electrical power budget

For high power RF sources wall plug efficiency, the ratio of net RFpower to total electrical power consumed is very important. Fordesigned 20 kW SSPA estimated electrical power budget at 30 1Cwater temperature was calculated (Fig. 12) based on individualcomponent’s RF measurement. It is clear that main componentscontributing to electrical power loss are power dissipation in 400 Wmodules, bias power supply, and output cable loss. As earlier stated,radial power combiners consume very little amount of power.

Wall plug efficiency with above calculation comes equal to42%. In actual operating conditions this efficiency of integrated

Fig. 12. Electrical power distrib

Fig. 13. 20 kW Solid State Power A

Table 4Safety interlocks of 20 kW solid state amplifier.

Sr. Parameter Value

1 Front panel indicators and control System enable, sys

2 Main interlocks Water flow, fire al

3 Primary power 300–415 V, 47–63

4 External protection Excessive reflectio

system is expected to be slightly lower due to reflection producedby amplitude and phase imbalance in PA modules’ output signals.

2.4. 20 kW Amplifier: overall system

Finally, as outcome of these efforts, two 10 kW amplifierunits were developed indigenously. These units were used tomake a 20 kW solid state amplifier with the help of additionaltwo-port low power divider and 20 kW coaxial combiner, asdescribed above. After rigorous testing, this amplifier wascommissioned and interfaced with low level RF control (LLRF)system for powering RF cavity in Indus-2 Synchrotron RadiationSource successfully (Fig. 13). As seen in this figure, combined RFpower received from 20 kW combiner and 20 kW directionalcoupler (both shown in the middle of 10 kW units) is trans-ferred to RF cavity through rigid 6-1/8 in. rigid coaxial copperline. This amplifier is complete in all respect of safety inter-lock, water cooling and power supply. Panel PC provides GUI

ution for 20 kW amplifier.

mplifiers (SSPA) at 505.8 MHz.

tem ON/OFF, RF ON/OFF, system shutdown, emergency trip and

arm and SSPA ready (for LLRF)

Hz, 3 Phase

n, over temperature, overdrive

Fig. 14. Measured power transfer characteristics of 20 kW SSPA at 505.8 MHz.

A. Jain et al. / Nuclear Instruments and Methods in Physics Research A 676 (2012) 74–8382

for all user related controls and indicators. Water cooling systemis seen on the right side. An Independent Low conductivitywater (LCW) plant capable of delivering up to 1200 l/m at amaximum pressure of 8 bar was used in Indus-2 SSPA RF area.LLRF system communicates with the main accelerator controlsystem. Interface of this SSPA with LLRF was planned in a simplemanner. Each 10 kW unit occupies 1�1.2 m2 area of floor spaceand 2 m height. Complete amplifier, along with outer 3 in. coaxiallines and 20 kW combiner and directional coupler, takes 1�5 m2

of floor space.Table 4 gives control and other useful specification of this

amplifier. During operation, once amplifier passes all self-tests, itasserts one signal (SSPA ready) to LLRF unit, which enables RFinput signal to amplifier.

RF intensity measurement was carried out close to the modulesand RF leakage was found 0.1 mW/cm2. At a distance of 1 m fromthe cabinet RF leakage was found up to 0.02 mW/cm2, much lowerthan the permitted (1.7 mW/cm2 at 505.8 MHz). In actual operatingcondition, average reflection of 46–47 dBm was observed at thirdport of circulator of each 400 W PA. This reflection was expected dueto variation phase distribution (Fig. 6) of PAs.

Complete wall plug efficiency for this amplifier was measuredas 34.8%. In order to make a simple manageable power source, inpresent PA modules, none of the mechanisms like delay line atinput, forced compression of drain characteristics, etc. have beenused for improving phase imbalance. Hence measured efficiencyis lower than the figure estimated on the basis of RF measurementof each building block of SSPA. Nevertheless, with the progress inRF power transistor development, it is expected that a futureefficiency improvement of the transistors up to 70%–80% couldboost the overall efficiency.

Measured RF power transfer characteristics and gain of 10 kWand 20 kW SSPAs are shown in Fig. 14. This characteristic is linearin common operation region (5 kW onwards). For 20 kW SSPA1 dB compression point is beyond 20 kW with more than 80 dB RFpower gain (with driver amplifier).

3. Conclusions

At 505.8 MHz, modular and compact 20 kW solid state RFamplifier comprising GaN LDMOS based amplifier module, powercombiner, divider, directional coupler and FPGA based control andinterlock, has been successfully developed and commissionedwith Indus-2 synchrotron radiation source. Necessary designmethodology has been demonstrated for economic and repeata-ble development of high power rigid system components. Themeasured and predicted results are in good agreement. Successfuldevelopment adds confidence for future development for select-ing solid state RF source in particle accelerator, among other tubebased radio frequency and microwave sources. The experiencegained, will be useful for the development of high power solidstate amplifiers for Spallation neutron source (SNS) and accel-erator driven systems (ADS).

Acknowledgment

We are thankful to members of RF systems division for theircontribution in the development of high power solid state RFamplifiers. Thanks are also due to the members of Indus accel-erator team for their participation in Indus-2 operation withdeployment of these amplifiers.

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