NSCL, East Lansing, Michigan
FRIB, East Lansing, Michigan
The 2007 Long Range Plan for Nuclear Science had as one of its highest recommendations the “construction of a Facility for Rare Isotope Beams (FRIB) a world-leading facility for the study of nuclear structure, reactions, and astrophysics. Experiments with the new isotopes produced at FRIB will lead to a comprehensive description of nuclei, elucidate the origin of the elements in the cosmos, provide an understanding of matter in the crust of neutron stars, and establish the scientific foundation for innovative applications of nuclear science to society.” A superconducting heavy-ion driver linac will be used to provide stable beams of >200 MeV/u at beam powers up to 400 kW that will be used to produce rare isotopes. Experiments can be done with rare isotope beams at velocities similar the driver linac beam, at near zero velocities after stopping in a gas cell, or at intermediate velocities (0.3 to 12 MeV/u) through reacceleration. An overview of the design proposed for implementation of the DOE national users facility FRIB on the campus of Michigan State University will be presented.
JLAB, Newport News, Virginia
Several 9-cell cavities electropolished and tested at Jefferson Lab are found to be quench limited. Pass-band mode excitation measurements provide the first clue of candidate cells responsible for the quench limit. A second RF test with thermometers attached to the equator region of candidate cells (typically only 2 candidates) reveals a hot spot caused by excessive heating of the operational defect and hence determines its location. High resolution optical tools inspect the RF surface corresponding to the hot spot to image and document the defect. All defects in cavities quench limited ~ 20 MV/m are sub-mm sized irregularities near but outside of the equator EBW. In contrast, no observable irregularities are found in some other cavities that are quench limited ~ 30 MV/m. These two types of quench limited cavities have different response to a second EP processing. In this paper, we will give a summary of the test result and attempts to catalog the observed defects.
JLAB, Newport News, Virginia
We have EP processed several multi-cell cavities previously heavy BCP etched. With a surprisingly light EP removal of less than 50 micron, all cavities have shown significant gradient and Q improvement. So far three cavities including two fine-grain niobium 7-cell CEBAF upgrade prototype cavities and one large-grain niobium 9-cell ILC cavities have been treated and tested. Both 7-cell cavities reached a quench limit without field emission. Another 7-cell cavity has been treated and is under RF test. We give a summary of the test results.
KEK, Ibaraki
Fermilab, Batavia
JLAB, Newport News, Virginia
We have continued high gradient R&D of ICHIRO 9-cell cavities at KEK. ICHIRO 9-cell cavity #5 (I9#5) that has no end groups on beam tube to focus on high gradient sent to Jlab as S0 tight loop study. Surface treatments and vertical test were repeated 3 times at Jlab, and then I9#5 sent back to KEK. We also repeated surface treatments and test at KEK. Maximum gradients were 36.5MV/m at Jlab, and 33.7MV/m at KEK so far. Now we are struggling with the puzzle why the results of singles do not work well on 9-cell cavities.
