Mike McCarthy

Status of the 805-MHz pulsed klystrons for the Spallation Neutron Source

Communications and Power Industries, Inc (CPI) produced 81 klystrons for the Spallation Neutron Source at Oak Ridge National Laboratory. The klystrons are rated for 550 kW peak at 805 MHz. seventy units have accumulated 1,284,647 hours of filament operation and 820,429 hours of high voltage operation to date. A higher power 700 kW version has been developed and is now in production.

Design and high power processing of RFQ input power couplers

A RF power coupling system has been developed for future upgrade of input coupling of the RFQ in the SNS linac. The design employs two coaxial loop couplers for 402.5 MHz operation. Each loop is fed through a coaxial ceramic window that is connected to an output of a magic-T waveguide hybrid through a coaxial to waveguide transition. The coaxial loop couplers are designed, manufactured, and high power processed. Two couplers will be used in parallel to power the accelerating structure with up to total 800 kW peak power at 6% duty cycle. RF and mechanical properties of the couplers are discussed. Result of high power RF conditioning that is performed in the RF test facility of the SNS is presented.

Status of the ITER ion cyclotron heating and current drive system

The paper reports on latest developments for the ITER Ion Cyclotron Heating and Current Drive system: imminent acceptance tests of a prototype power supply at full power; successful factory acceptance of candidate RF amplifier tubes which will be tested on dedicated facilities; further design integration and experimental validation of transmission line components under 6MW hour-long pulses. The antenna Faraday shield thermal design has been validated above requirements by cyclic high heat flux tests. R&D on ceramic brazing is under way for the RF vacuum windows. The antenna port plug RF design is stable but major evolution of the mechanical design is in preparation to achieve compliance with the load specification, warrant manufacturability and incorporate late interface change requests. The antenna power coupling capability predictions have been strengthened by showing that, if the plasma scrape-off layer turns out to be steep and the edge density low, the reference burning plasma can realistically be di...

Development and testing of high power RF vector modulators

A fan-out RF power distribution system can allow many accelerating cavities to be powered by a single high-power klystron amplifier. High-power vector modulators can perform independent control of amplitudes and phases of RF voltages at the cavities without changing the klystron signal. A prototype high-power RF vector modulator employing a quadrature hybrid and two ferrite phase shifters in coaxial TEM transmission lines has been built and tested for 402.5 MHz. RF properties of the design and results of high power testing are presented.

Methods for matching to the ITER Ion Cyclotron Heating antenna

The US-ITER in-kind contribution to the ICH (Ion Cyclotron Heating) system for the tokamak being built in Cadarache, France, is the coaxial transmission lines, matching systems, and matching algorithms. A prematching system composed of 20 ohm triple-stub-tuned lines was proposed to match to the antenna. Because of constraints on the port cell and space availability, triple stub prematching may not be possible, so alternative prematching systems are proposed for use. Results of initial analyses of the prematching concepts are presented.

Evaluation of neutron and gamma detectors for high-temperature well-logging applications

Nuclear methods based on neutron and gamma-ray detection have been used for decades in the well-logging industry, including both oil and gas logging, for characterization purposes. Current well-logging tools operate in the range of 150 to 175°C. For geothermal logging applications, however, operations at higher temperatures are needed. In this paper, the results for neutron and photon detector measurements at higher temperatures, environmental tests, and modeling and simulations are presented.

Spallation Neutron Source (SNS) high pulse repetition rate considerations

Increasing the pulse repetition rate (PRR) of the SNS Linac to its designed maximum of 60 Hz to provide 1.4 MW of beam on target is in progress. Operation above 60 Hz to provide beam to a second target is also being considered in the future. Increasing the PRR to 80 Hz would allow the additional pulses to be diverted to a second target. This paper discusses the impact of increasing the PRR on the SNS infrastructure including radio frequency (RF) systems and structures, the ion source, cryogenics, controls and the target.