development of 499.75 mhz solid state wide band rf power amplifiers for the clic injector...

Development of 499.75 MHz Solid State Wide Band RF Power Development of 499.75 MHz Solid State Wide Band RF Power Amplifiers for the CLIC injector pre-buncher *Amplifiers for the CLIC injector pre-buncher *

Purushottam Shrivastava, P. Mohania, A. Mahawar, P.D. GuptaPurushottam Shrivastava, P. Mohania, A. Mahawar, P.D. Gupta

Raja Ramanna Centre for Advanced TechnologyRaja Ramanna Centre for Advanced Technology

Indore, IndiaIndore, India

CLIC Workshop Jan 26-30, 2015

* DAE (India) CERN Collaboration under NAT Protocol* DAE (India) CERN Collaboration under NAT Protocol

Motivation

Under DAE (India) CERN collaboration in Novel Accelerator Technologies, of which CLIC collaboration is a part, a 20kW Solid State RF Power Amplifier R, D & D effort by RRCAT, Indore is envisaged.

RRCAT had earlier built a 476 MHz, 10kW Solid State RF Power Amplifier for use in its FEL project which established base for the present collaboration. Long term experience in this field is available.

All required design, fabrication, testing and qualification facilities are available in-house at RRCAT.

In order to achieve the desired specifications, as well as to have feasibility studies it was thought to have 1kW, 4/5 kW intermediate stages as a part of development so that necessary improvements/ modifications can be done at 20kW level after tests at CERN.

Purushottam Shrivastava, RRCAT, CLIC Workshop Jan 26-30, 2015, CERN Geneva

Compact, 10kW solid state RF power amplifier, @476 MHz using LDMOS transistors and Compact, 10kW solid state RF power amplifier, @476 MHz using LDMOS transistors and novel planar combiners and dividers for pre-buncher cavity novel planar combiners and dividers for pre-buncher cavity of injector LINAC for CUTE of injector LINAC for CUTE

FEL project at RRCATFEL project at RRCAT

10kW SSPA during tests


A compact 10 kW, 476 MHz solid state radio frequency amplifier for pre-buncher cavity of free electron laser injector linear accelerator. Published in: Review of Scientific Instruments (Volume:84 , Issue: 9 ) Sept 2013.

http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=4915264

http://ieeexplore.ieee.org/xpl/tocresult.jsp?isnumber=6589054

Parameter Nominal value Unit

Output power 20 kW

Frequency 499.75 MHz

Band width (3dB) 58 MHz

Pulse Length 140.3 micro sec

Repetition rate 50 Hz

Phase variation shot to shot, flat top ~1 deg

Amplitude stability ~1 %


Specifications of the 20kW Solid State AmplifierSpecifications of the 20kW Solid State Amplifier

Proposed 20kW SSPA Architecture

x8

Pre Driver Amplifier

Driver Amplifier

4kW Amplifier Modules

RF Switch

I/P (Type-N) O/P (DIN7/16)


Load

Generator Pre-Driver 1W Driver 100W 5kW

5kW Prototype Amplifier Configuration

Feasibility Studies: Prototype development at 4/5kW power level


5kW Amplifier Module 210mmx300mm Amplifier Module enclosed and mounted on heat sink

Parameter Test Result CommentsPeak Power obtained 67.1dBm (~5120W) The maximum input power required is

+13dBm.

Gain @ 5kW 57 dB

54dB

54dB

@499.75MHz

@469.75MHz

@529.75MHzBandwidth (3dB) 60 MHz (+/-30MHz) Centre Frequency 499.75MHzPulse To Pulse Amplitude variation ~0.1dB @67.1dBm

Pulse to Pulse Phase variation ~1° @67.1dBmIn pulse amplitude variation <0.2dB @ 67.1dBmIn pulse phase variation <2° @67.1dBm

Test results of the 5kW prototype amplifier


Input trigger signal 2.5V-5 V, 2 µs (high Impedance)


The amplifier has been developed as a three stage amplifier which consists of the following stages.

1 W Pre-driver amplifier 100 W GaN HEMT based driver amplifier 4kW High Power stage which is developed by combining 4 LDMOS transistors using Wilkinson combiner and divider networks on low loss flexible PTFE based laminates.

The switching ON time is defined by a RF switch which is having a controlled mono-shot circuit which sends TTL signal to switch for 150µs at rising edge of the input trigger (delay in RF ON ~200ns)

The three stages of the amplifier uses the following power supplies1. 1W Pre-driver amplifier 24V, 600mA2. Driver Amplifier 32V, 200mA for drain and -3.15V for Bias3. High power stage 55V, 2A for drain and 2.15V for Bias

Description of stages of amplifier

Front Panel of amplifier .. The front panel contains six LED indicators, five are meant to indicate the status of Power supplies (+55V/54V, +32V,+24V,+5V,-5V) and one LED shows the trigger Input status.

Back Panel has N-Type connectors for Input and Output signals, a BNC connector for Trigger Input and a 5 pin connector for D.C. Power supply connections.

Inside view of the amplifier system chassis. SSPA with the DC power supply.

Test Results of the prototype Test conditions: 50Hz repetition rate, 150µs pulse width, Input Power, 12.5dBm

Output Power vs Frequency response. Gain characteristics at 499.75 Mhz

Gain characteristics at 470.75 Mhz Gain characteristics at 528..75 Mhz


Amplitude and phase response of the Pulse O/P @ 499.75MHz. Left image shows the amplitude response of the amplifier as seen on a peak power analyzer. Analyzer scale 0.2dB/div. Right image shows phase detector output as seen on a CRO, Scale 10mV/div.

Conclusion:

•The amplifier system was tested for all characteristics and was subjected heat run tests of more than 20 Hours, no additional cooling was required.•Amplifier power reaches thermal equilibrium after 30 minutes and has excellent phase and amplitude stability meeting specifications. •Amplifier heat sink temperature 65°C at steady state.•All the tests were performed using a 4 channel D. C. power supply which has stability of better than +/-0.05%.•For achieving the stability the 5kW amplifier module is operated at 4kW power level.•Looking into various losses and safe margin, 8 units of such modules will be integrated.•The intermediate step to build a prototype has been achieved and paves the way for the final 20kW amplifier system after further tests at CERN.


development of 499.75 mhz solid state wide band rf power amplifiers for the clic injector...

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