STATUS OF THE RAL FRONT END TEST STAND
The Front End Test Stand (FETS) under construction at RAL is a demonstrator for front end systems of a future high power proton linac. Possible applications include a linac upgrade for the ISIS spallation neutron source, new future neutron sources, accelerator driven sub-critical systems, a neutrino factory etc. Designed to deliver a 60mA H-minus beam at 3MeV with a 10% duty factor, FETS consists of a high brightness ion source, magnetic low energy beam transport (LEBT), 4-vane 324MHz radio frequency quadrupole, medium energy beam transport (MEBT) containing a high speed beam chopper plus comprehensive diagnostics. This paper describes the current status of the project and future plans.
Emittance Calculations based on Maximum Entropy ( MaxEnt ) ∗
Among present challenges for beam diagnostics and instrumentation are issues presented by high beam intensity, brightness, resolution and the need to avoid inserting mechanical parts into the beam. This very often means applying non–destructive methods, which avoid interaction between ions and mechanical parts and, furthermore, allow on–line measurements during normal beam operation. The preferred technique for H beams is the photo–detachment process where (laser) light within the range of 400. . . 1000 nm has a sufficient continuous cross section σPD to neutralize negative ions. The actual diagnostics are then applied to either the neutrals produced or the electrons. The latter are typically used for beam profiles whereas neutrals are more suitable for emittances, and form the subject of the present paper. This provides an overview of the basic features of the diagnostic technique, followed by discussion about computing the missing second transverse projection view using a method called Maximum Entropy Method (MEM or MaxEnt).
DEVELOPMENT OF MEANDER-LINE CURRENT STRUCTURE FOR SNS FAST 2.5-MEV BEAM CHOPPER
A new current structure for the fast traveling-wave 2.5MeV beam chopper for the Spallation Neutron Source (SNS) project has been developed [1]. The structure is based on the meander-folded notched stripline with dielectric supports and separators. Its design has been optimized using electromagnetic 3-D modeling with MAFIA to provide rise and fall times around 1 ns. A fulllength 50-cm prototype has been manufactured, and its measurements have been performed. Measurements results and their comparison with simulations are presented.