ORNL, Oak Ridge, Tennessee
University of Tennessee, Knoxville, Tennessee
ORNL RAD, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725.
Nanocrystalline diamond foils are now in use for injection stripping at the SNS. Typical dimensions are 17x25 mm x 300-350 ug/cm2 physical thickness. Corrugations of the foil help to maintain flatness, but after ca. 300 C of injected charge curling is observed. We continue to experiment with foil preparation techniques. To allow independent stripper foil testing without impacting SNS neutron production, we have assembled a 30 keV electron beam foil test facility to investigate foil lifetimes. At 30 keV acceleration, a 1.6 mA/mm2 electron beam imparts the same peak heating load to a carbon foil as the injected and circulating current of the 1.4 MW SNS. At this energy the electron stopping distance is approximately six-fold longer than the foil thickness. The electron gun is capable of 5 mA current in a focal spot less than 1 mm FWHM diameter. Two foil stations are available for sequential tests, and foils can be rotated relative to the beam to vary their effective thickness. A 6 us risetime optical pyrometer records instantaneous foil temperatures over the 60 Hz heating profile. A CCD camera captures foil images over time. Results using this test stand are described.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725
The SNS Ring has now been operating for about 2.5 years, and our march continues to increase the beam power to the design value of 1.4 MW. The Ring is a loss-limited machine, and in general the radioactivation levels are good, but there are some unanticipated hot spots that we are working to relieve. Beam optics functions have been measured using the model independent and orbit response matrix methods, and our results will be compared to the ideal model. High-intensity beam profiles measurements show space-charge effects, and these will be compared to model calculations. We will also discuss the status of equipment upgrades that are now in progress in the high-energy beam transport momentum dump, the injection-dump beam line, and in the ring-to-target beam line.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC05-00OR22725
As the SNS beam power is increased, the collimator systems are becoming correspondingly more important. The High Energy Beam Transport (HEBT) transverse collimators are now routinely used during neutron production. We are in the process of redesigning the HEBT momentum collimation system due to problems with gas production from radiolysis. The Ring collimators are designed for two-stage operation but to date they are mainly used in one-stage mode. In this paper we will discuss the status, the operational performance, and upgrades to the collimation systems.
IUCF, Bloomington, Indiana
ORNL, Oak Ridge, Tennessee
Funding: Division of Materials Science, U.S. Department of Energy, under contract number DE-AC05-96OR22464 with UT-Battelle Corporation for Oak Ridge National Laboratory
In order to achieve a more robust and optimal performance, the difference between the real machine and its underlying model should be understood and eliminated. Discrepancies between the measuremed and predicted linear optics suggest possible errors of the focusing magnets and diagnostic devices. To find and correct those errors, a widely used method, orbit response matrix (ORM)* approach is applied to the SNS storage ring, which successfully brings the tune deviation from 3% to 0.1%, improves horizontal beta beating from 15% to 3%, and perfectly flattens the orbit. In this article, we discussed the progress and possible future improvements with the SNS ring optics correction.
*J. Safranek, "Experimental determination of storage ring optics using closed orbit response measurements", Nucl. Inst. and Meth. A388, (1997), pg. 27