BNL, Upton, Long Island, New York
The most important parameter for the high intensity linacs are the losses. The losses are about limited to 1W/m for the hand on maintenance requirements. This limit translates about 1 nA at 1 GeV and 100 nA at 10 MeV. Therefore less attention are paid to physics design low energy area, especially for the longitudinal plane which is responsible for the implanting non-linearity in the particle distribution which are often responsible for the losses at high energies. We will present upgrade for BNL 200 MeV linac in the low energy and medium energy transport system. We were able to reduce the transverse emittance by more than factor of two and losses in the entire linac complex by order of magnitude.
Fermilab, Batavia
ORNL, Oak Ridge, Tennessee
BNL, Upton, Long Island, New York
One of the initial motivations for replacing the aging Fermilab Proton Source was to support the 120 GeV Neutrino program at the 2 MW level while supporting a broad 8 GeV Physics program. Over the years the design parameters of the new Proton Source have evolved from the 2005 Proton Driver configuration of a 2MW 8 GeV pulsed H- linac injecting directly into the Main Injector or Recycler ; to a 2MW 2 GeV CW linac supporting a 2 GeV Experimental Program while injecting into a new 2-8 GeV Rapid Cycling Synchrotron which would then supply protons to the Main Injector. The current design parameters of the project include a 3 GeV CW linac accelerating up to 1 mA (average) H- and a 3 GeV Experimental Area with the connection to the Main Injector Complex as an upgrade. Whether the upgrade path includes a new 6(or 8)GeV CW or pulsed linac, or 3 to 8 GeV RCS and the ultimate linac current remains to be determined. The basic issues of injection insertion design, foil and laser stripping options, foil survivability and loss issues will be discussed in context of the present options. Both analytical estimates and simulation results will be discussed.
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.
