Author: Crofford, M.T.
Paper Title Page
MOP257 High Power RF Distribution and Control for Multi-Cavity Cryomodule Testing 591
 
  • Y.W. Kang, M. Broyles, M.T. Crofford, X. Geng, S.-H. Kim, S.W. Lee, C.L. Phibbs, K.R. Shin, W.H. Strong
    ORNL, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The SNS has been successfully operating 81 superconducting six-cell cavities in 23 cryomodules in its linac to achieve the goals in beam power and energy. For near-term production of spare cryomodules and the upcoming power upgrade project that will need 36 additional cavities in 9 cryomodules, high RF power testing and qualification of the cavities is required in the RF test facility. Simultaneously powering all the cavities in a cryomodule is considered desirable for robust conditioning and studying of cavity field emission since certain cavities exhibit field emissions that could be mutually coupled. A four-way variable output power waveguide splitting system is being prepared for testing cryomodules with up to four cavities. The splitting system is fed by an 805 MHz, 5 MW peak power pulsed klystron. The power output at each arm can be adjusted in both amplitude and phase to wide ranges of values using two mechanical waveguide phase shifters that form a vector modulator. The system control is implemented in the EPICS environment similar to the main accelerator controls. The work performed on the design, integration, operation, and test of the system are presented.
 
 
MOP300 The Spallation Neutron Source Eight-Channel Pulsed Power Meter 684
 
  • M.T. Crofford, X. Geng, T.W. Hardek
    ORNL, Oak Ridge, Tennessee, USA
  • T.L. Davidson
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  The Spallation Neutron Source (SNS) Low Level Radio Frequency (LLRF) Control System currently utilizes the High-Power Protection Module (HPM) to monitor RF power levels, arc faults, and associated signals for the protection of the RF systems and accelerating cavities. The HPM is limited to seven RF channels for monitoring signals which in some instances leaves some signals of interest unmonitored. In addition, the HPM does not support monitoring of RF frequencies below 100 MHz which makes it unusable for our Ring and Ion Source systems that operate at 1 and 2 MHz respectively. To alleviate this problem, we have developed a microprocessor based eight channel pulsed RF power meter that allows us to monitor additional channels between the frequency range of 1 MHz to 2.5 GHz. This meter has been field tested in several locations with good results and plans are in place for a wider deployment.  
 
THOAS3 Status of the Oak Ridge Spallation Neutron Source (SNS) RF Systems 2050
 
  • T.W. Hardek, M.T. Crofford, Y.W. Kang, M.F. Piller, A.V. Vassioutchenko
    ORNL, Oak Ridge, Tennessee, USA
  • S.W. Lee, M.E. Middendorf
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  The SNS has been delivering production neutrons for five years with first beam delivered to the neutron target at the end of April 2006. On September 18, 2009 SNS officially reached 1 megawatt of beam on target marking the achievement of a decades-old dream of providing a U.S. megawatt class pulsed spallation source. The SNS is now routinely delivering 1 megawatt of beam power to the neutron target at over 85 percent of the scheduled beam time. The present effort is aimed at increasing availability eventually to 95 percent and gradually increasing the intensity to the 1.4 megawatt design level. While the RF systems have performed well since initial installation some improvements have been implemented. This paper provides a review of the SNS RF Systems, an overview of the performance of the various components and a detailed review of RF related issues addressed over the past several years.  
slides icon Slides THOAS3 [2.759 MB]  
 
THOCS3 R&D Status for In-Situ Plasma Surface Cleaning of SRF Cavities at Spallation Neutron Source 2124
 
  • S.-H. Kim, M.T. Crofford
    ORNL, Oak Ridge, Tennessee, USA
  • M. Doleans
    NSCL, East Lansing, Michigan, USA
  • J.D. Mammosser
    JLAB, Newport News, Virginia, USA
  • J. Saunders
    ORNL RAD, Oak Ridge, Tennessee, USA
 
  Funding: This work was supported by SNS through UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. DOE.
The SNS SCL is reliably operating at 0.93 GeV output energy with an energy reserve of 10MeV with high availability. Most of the cavities exhibit field emission, which directly or indirectly (through heating of end groups) limits the gradients achievable in the high beta cavities in normal operation with the beam. One of the field emission sources would be surface contaminations during surface processing for which mild surface cleaning, if any, will help in reducing field emission. An R&D effort is in progress to develop in-situ surface processing for the cryomodules in the tunnel without disassembly. As the first attempt, in-situ plasma processing has been applied to the CM12 in the SNS SRF facility after the repair work with a promising result. This paper will report the R&D status of plasma processing in the SNS.
 
slides icon Slides THOCS3 [3.294 MB]