IUCF, Bloomington, Indiana
ORNL, Oak Ridge, Tennessee
SLAC, Menlo Park, California
Recently, discrepancies between model-based and observed linear optics, such as the tune and the closed orbit, have been observed in the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. Accurate accelerator modeling is very important for machine control during the ongoing power ramp up. The Orbit Response Matrix (ORM) method is applied here to find and correct errors in the linear optics of the SNS ring. With the closed orbit data (4472 data points), we are able to calibrate the strength of the steering magnets, the BPM gain factors, and 6 quadrupole power supplies. Current results and remaining challenges will be presented and discussed.
ORNL, Oak Ridge, Tennessee
The 248 meter Spallation Neutron Source accumulator ring is designed to operate with a beam intensity of 1.5·1014 ppp. A major concern for high intensity operation is the possibility of beam instabilities. Recently a series of experiments have been performed to systematically map out the instability parameter space. Beam instabilities have been measured versus betatron tune, ring RF voltage, lattice chromaticity, and beam intensity. The results of these studies are presented here
ORNL, Oak Ridge, Tennessee
Operating at 0.5 MW beam power on target, the Spallation Neutron Source (SNS) is already the world's most powerful pulsed neutron source. However, we are only one third of the way to full power. As we ramp toward full power, the control of the beam and beam loss in the ring will be critical. In addition to practical considerations, such as choice of operating point, painting scheme, and rf bunching, it may be necessary to understand and mitigate collective effects due to space charge, impedances, and electron clouds. In dedicated high intensity beam study shifts, we have already observed resistive wall, impedance driven, and electron cloud activity. The analysis and simulation of this data are important ongoing activities at SNS. This talk will discuss the status of this work, as well as other considerations necessary to the successful full power operation of SNS.
ORNL, Oak Ridge, Tennessee
Beam loss is higher than expected in the Ring injection section and in the injection dump beam line. The primary causes are fairly well understood, and we have made some equipment modifications to reduce the loss. In the ring extraction beam line the beam distribution exhibits cross-plane coupling (tilt), and the cause has been traced to a large skew-quadrupole component in the extraction Lambertson septum magnet. In this talk we will discuss the issues surrounding the ring injection and extraction systems, the solutions we have implemented to date, and our plans for future improvements.
KEK, Ibaraki
University of Tennessee, Knoxville, Tennessee
ORNL, Oak Ridge, Tennessee
At the 39th ICFA HB2004 workshop and the EPAC-2006 conference, we reported the lifetime and properties of the HBC (Hybrid type Boron-mixed Carbon) foils, a newly developed material, measured by the use of a 3.2 MeV Ne+ ion beam, which deposits significant energy in the foil due to the heavy ion. The content reported showed superior durability against high temperature damage due to foil deformation, thickness reduction and pinhole production at 1700 ± 100K compared with the cluster foils made by the CADAD method. This time, we measured the lifetime of the HBC-foils and the high quality nanocrystalline diamond foils including commercially available foils at 1800 ± 100K which induces the high temperature damage. The measurements were performed by using the KEK-650 keV high intensity H- and DC beam, which generates the same energy deposition as the RCS of J-PARC. In this workshop, we report the results obtained.