Millimetre-wave amplifiers and oscillators have been developed and commercialized by CPI Canada for over five decades, utilizing Extended Interaction-type Klystron circuits. This type of circuit has proven to be an effective means of achieving high RF power with high electrical efficiency in a physically compact device. In this paper, an overview of recent advancements is provided, with a description of the applications driving these developments.

This paper summarizes the performance improvements of a 264 GHz EIO subsystem achieved over the last decade. Every characteristic, practical, and reliability aspects were considered and addressed. Newer mechanical tuning provides operation with 5 W output power across a 1 GHz frequency range. Reduced voltage ripple of the Gen-IV power supply provides RF signal with linewidth of less than 4 MHz. Available LifeExtender option has the capability to extend a cathode’s lifetime beyond three years of continuous operation. A modified water-cooling design prevents electro-etching of the miniature RF circuit, while the collector has a depression capability of up to 77%.

This paper presents the development and test of a 198 GHz pulsed Extended Interaction Klystron (EIK) subsystem for THz markets including Dynamic Nuclear Polarization (DNP). The EIK amplifies a 30 mW input signal to 140 Watts with a - 3dB bandwidth of ~275 MHz. The operating cathode voltage is 17.7 kV and the cathode current is 178 mA. With electron beam transmission of 84 %, the subsystem is capable of operating with a duty cycle up to 5%. Liquid cooling is used to maintain the radio frequency (RF) signal stability required for DNP applications.

Modern Dynamic Nuclear Polarization (DNP) experiments often utilize gyrotron sources for irradiation of electron spins at 140-593 GHz. The total cost of ownership, size, and complexity of gyrotrons, however, limits wider adoption. The introduction of lower-cost and more compact sources can have a significant impact on the DNP community. This contribution describes the development of a 263 GHz EIK, design of transmission line for optimal irradiation of the DNP NMR sample, and detailed performance characterization for DNP experiments.

A compact, conduction-cooled 5.355 GHz Klystron, based on EIK technology, has been developed for use in the Scatterometer Instrument segment of the forthcoming MetOp-Second Generation mission. Two engineering model Klystrons have been built since the start of the development effort in 2016 and a full space-qualification model will follow in 2017. The Klystron draws upon space heritage from higher frequency Extended Interaction Klystrons developed for the CloudSat and EarthCARE programs, and utilizes a new RF circuit design, tailored to the MetOp-SG requirements.

To meet demands of DNP, sub-mm-wave radar and other THz frequency markets, CPI Canada continues the performance improvements of CW and pulsed compact EIKs. The novel model of a 266 GHz oscillator generates up to 15 W of CW power, while the expected power of a 264 GHz pulsed amplifier currently in fabrication is 50 W. Together with power enhancements, major attention is paid to reliability, lifetime and signal stability.

This paper presents recently performed at CPI Canada development of high power 263 GHz CW EIO generator for DNP enhancement and pulsed 263 GHz EIK for radar applications.

An Extended Interaction Klystron (EIK) design has been developed to the support extreme signal stability requirements of space-borne interferometric applications. This is an unprecedented set of requirements for an EIK. In conjunction with the Canadian Space Agency (ASC/CSA)and Jet Propulsion Laboratory, Communications and Power Industries, Canada (CPI) advanced this development through testing of a heritage design EIK, testing a dedicated Demonstration Model EIK and an Engineering Model EIK. Each step of testing provided guidance in the development of the EIK Design, finally providing confidence in the EIK's ability to support the needs of the interferometric radar.

Rapid development of advanced millimeter wave radars affected all markets including space-borne Earth observation. Space missions require long-life, high power amplifiers in a compact package with high efficiency and reliability. The Extended Interaction Klystron technology has demonstrated its capability to meet or exceed all requirements for space-borne applications. This paper reviews EIK performance and the specifics of the development, qualification, fabrication and acceptance process. Brief description of current and future missions is presented.

Significant progress in modeling and manufacturing technologies open wide possibilities for performance improvements of millimeter-wave vacuum electron devices. However, many practical aspects should be considered to realize reliable long-life high-power sources. These are: thermal and RF stability, materials and assembly sensitivity to manufacturing, electrical stresses, cathode poisoning prevention, thermal beam effects, and many others. We address the full spectrum of design and manufacturing aspects while developing state-of-the-art extended interaction klystrons (EIKs). EIKs provide unprecedented RF performance and reliability in a compact user-friendly package. This paper discusses EIK design methodology and manufacturing concepts stating self-imposed restrictions and design modifications enhancing power capability, bandwidth, and extending operating frequencies into the terahertz region.

A novel model of the compact high power 264 GHz CW Extended Interaction Oscillator has been developed by CPI Canada. By combination of mechanical tuning and electronic switching between two operating modes, this EIO provides over 1 W of power in the range of 258 to 270 GHz. Liquid cooling is used to stabilize RF circuit temperature and prevent frequency detuning. Further development is ongoing to support THz operation with enhanced output power, which is currently limited by vacuum window capability.

Experimental testing of electron beam formation, transport, and depressed collection is performed in a beamstick for a 670 GHz extended interaction klystron with a 25 kV, 100 mA nominal operating point. Beam transmissions of 77–86% are achieved through a 125 micron diameter by 1.7 cm long beam tunnel.

We describe our progress on the development of extended interaction klystron amplifiers operating at 670 GHz, meeting demanding requirements for output power, gain, bandwidth, and efficiency.

The design and test of an Extended Interaction Klystron operating at 17.2 GHz is presented. The program goal is to demonstrate the feasibility of meeting the technical requirements of the proposed CoReH20 mission. The device will provide over 3.5kW of peak RF power and 20% duty cycle in a conduction cooled configuration weighing less than 9 kg.

The large-signal code TESLA (Telegraphist's Equations Solution for Linear-beam Amplifiers) was originally developed for the analysis and design of klystrons. It has now been applied to the simulations of an extended interaction klystron (EIK) for the first time. Results for the power transfer curve and bandwidth curves computed for a G-band EIK compare well to their measured values. TESLA obtains these results almost two orders of magnitude faster than a 3D particle-in-cell simulation code.

The large-signal code TESLA (Telegraphist's Equations Solution for Linear beam Amplifiers) was originally developed for the analysis and design of klystrons. It has now been applied to the simulation of an extended interaction klystron (EIK) for the first time. Results for the power transfer curve and bandwidth curves computed for a G-band EIK compare well to their measured values. TESLA obtains these results almost on the two orders of magnitude faster than a 3D particle-in-cell simulation code.

This paper reviews the technology and demonstrated capability of millimeter wave Extended Interaction Klystrons for use in wide range of radar systems. It discusses design and manufacturing concepts stating selfimposed restrictions and design modifications to enhance RF performance, lifetime, reliability and extended operating frequency into the THz region. Presented data are supported using information provided by various academic and industrial customers.

EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) is the 6th Earth Explorer Core Mission of the European Space Agency and a joint undertaking with the Japan Aerospace Exploration Agency (JAXA). It will study and analyze the interaction and impact of clouds and aerosols on the Earth's radiative budget. Along with other instruments, the satellite payload will include a 94 GHz Cloud Profiling Radar (CPR) with Doppler capability. This paper presents the development of a High Power Amplifier for the EarthCARE CPR and reviews HPA requirements, design and performance.

This paper reviews the technology and demonstrated capability of mmW and Sub-mmW Extended Interaction Klystrons at CPI Canada. It discusses design and manufacturing concepts stating self-imposed restrictions and design modifications enhancing power capability, bandwidth and extending operating frequency into the THz region.

This presentation describes the performance of a recently developed 218 GHz extended interaction klystron (EIK) amplifier producing 7W CW and weighing less than 4.3 kg.