ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source has been operational for over three years, characterized by a rapid power ramp-up over the first two years and operation at a beam power of about one MW for the past year. Equipment reliability is a major concern at a user facility like SNS, and beam power has been limited primarily by equipment robustness to date. Beam loss is also a major concern, and is the primary driver in beam tuning. Many beam loss reductions are found empirically, and are not well understood. SNS is operating at the MW level with uncontrolled beam loss below the 1 W/m level, as required for hands on maintenance, and has not limited the operational beam power to date.
ORNL, Oak Ridge, Tennessee
ORNL RAD, Oak Ridge, Tennessee
LANL, Los Alamos, New Mexico
BNL, Upton, Long Island, New York
The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H0 excited states created during the H− charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H− beam, which circled around to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and contribute to foil and bracket failure. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we will detail these and other interesting failure mechanisms, and describe the improvements we have made to mitigate them.
ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source (SNS) has been operating at the MW level for about one year. Experience in beam loss control and machine activation at this power level will be presented. Also experience with machine protection systems will be reviewed, which are critical at this power level. One of the most challenging aspect of high power operation has been attaining high availability, and these issues will also be discussed.
ORNL, Oak Ridge, Tennessee
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
PSI, Villigen
As hadron machines approach higher beam intensity and operational power levels, issues such as machine activation caused by beam loss, machine protection and machine availability become more critical concerns. The operational experience of the high power, high intensity facilities in these areas is compared.