JLab, Newport News, Virginia, USA
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
Initial vertical RF test results and quench studies for six of the eight undressed 9 cell cavities slated for use in the Jefferson laboratory LCLS-II prototype cryomodule were presented at IPAC2015*. For the final string 2 more cavities AES029 and AES030 (work done at Cornell) are being processed and tested for qualification before helium vessel welding. In addition, AES034 (initial R&D treatment) is being reworked with the current production protocol after a surface reset to improve the overall performance. After final qualification all 8 cavities will be welded into helium vessels and equipped with HOM couplers. In this paper we will present the final undressed and dressed vertical RF data comparing the changes in the surface resistance before their installation in the cryomodule string.
*A.D. Palczewski et al. Quench Studies of Six High Temperature Nitrogen Doped 9 Cell Cavities for use in the LCLS-II Prototype Cryo-module at Jefferson Laboratory, Proc. IPAC2015, WEPWI019, 2015.
ORNL RAD, Oak Ridge, Tennessee, USA
Omega Technical Services, Oak Ridge, Tennessee, USA
ORNL, Oak Ridge, Tennessee, USA
Many of the SRF activities involve interactions to cavities which presents risk for particulate contamination to RF surfaces. In order to understand and reduce contamination in cavities during cleaning, vacuum pumping and purging, and in-situ cryomodule repairs, a Quality Assurance (QA) studies were initiated to evaluate these activities and improve them where possible. This paper covers the results of investigations on the effectiveness of the SNS ultrasonic cleaning systems, particulate control during pumping and purging, procedure development for in-situ cryomodule repairs, the application of these studies to the repair of a linac cryomodule, and discussion of further improvement in these areas.
JLab, Newport News, Virginia, USA
Particles are one possible cause of field emission issues in SRF cavity operations. During clean room cavity preparation, several processes could contribute to the generation of particles. One of them is friction between hardware during assembly and disassembly. It is important to understand the behaviours that generate and propagate particles into cavities. Using a single cell cavity, particle shedding between flanges and other materials have been tested. The number of particles is recorded with an airborne particle counter, and the generated particles are examined with microscope. The migration of particles into a cavity due to different movements is studied. Suggestions are made to reduce particle generation and prevent contamination of the cavity interior area.
JLab, Newport News, Virginia, USA
The LCLS-II project aims to build 35 accelerating cryomodules, which are based on the European XFEL design but modified for operation in CW mode. Each cryomodule houses eight TESLA-style nine-cell superconducting radio-frequency cavities. The activities to assemble the first two prototype cryomodules are ongoing at FNAL and JLab. 264 cavities worth of cavities for the remaining 33 cryomodules will be procured from two industrial vendors in similar quantity considering the option to produce spares. The assembly of cavities into the production cryomodules will be distributed among FNAL (16 cryomodules) and JLab (17 cryomodules). In this paper the cavity procurement and qualification plan for the LCLS-II project is detailed.
ORNL, Oak Ridge, Tennessee, USA
ORNL RAD, Oak Ridge, Tennessee, USA
The Spallation Neutron Source (SNS) has developed a vertical test area (VTA) for the testing and qualification of superconducting radio frequency cavities. The associated RF System successfully supported the initial commissioning of the VTA system and has been utilized for cavity testing at both 4 and 2 K. As operational experience was gained, improvements to the RF system were implemented to better utilize the dynamic range of the system, and software updates and additions were made to meet the operational needs. The system continues to evolve as we gain better understanding of the testing needs.