LANL, Los Alamos, New Mexico, USA
Beam bunching optimization at low energy (750keV) before injecting into a DTL (100MeV) is essential for beam transport, emittance reduction, and focusing on to a target. The LANSCE simultaneously utilizes H+ and H− beam (with a timing variation) for many important national security sciences. In addition to quadrupole, several bunchers are utilized in the transport. A technique with pre-bunching at lower frequency and main bunching at higher frequency is utilized for beam injection into the linac. The buncher parameters (voltage and frequency) are well established for operations. However, there is the possibility that the parameters vary with time due to electrical malfunction or adverse tuning during a beam development activity. Some effort is needed to correct the parameters as a non-optimized pre-bunching setup can alter the beam phase space and the nominal beam intensity at a desired location. Here, we examine emittance and phase space distribution variation for H− beam due to variation of the low frequency (16 MHz) buncher voltage, which typically operates at 25 kV peak. Beam phase dynamics with buncher voltage variation is also examined using the beam transport code Parmila.
LA-UR-16-23822
LANSCE: Los Alamos Neutron Science Center
DTL: Drift Tube Linac
LANL, Los Alamos, New Mexico, USA
The presence of duodecapole components in quadrupole focusing field results in excitation of sixth-order single-particle resonance if the phase advance of the particles transverse oscillation is close to 60 deg. This phenomenon results in intensification of beam losses. We present analytical and numerical treatment of particle dynamics in the vicinity of sixth-order resonance. The topology of resonance in phase space is analyzed. Beam emittance growth due to crossing of resonance islands is determined. Halo formation of intense beams in presence of resonance conditions is examined.
