Speaker: Mihaly Vadai (BE-RF-BR)
Reduction of extraction losses with barrier buckets in the PS
The residual beam losses at the transfer of fixed target beams from PS to SPS using the Multi-Turn Extraction (MTE) are due to the longitudinally unbunched structure of the beam. They occur during the rise time of the kicker magnets. Creating a short gap in the beam with a so-called radiofrequency (RF) barrier bucket addresses this problem.
Interestingly, the existing wide-band cavity in the PS has well-suited parameters to generate such a barrier bucket. The beam synchronous multi-harmonic sources driving the accelerating cavities were moreover an ideal starting point to develop a dedicated RF source to drive the Finemet cavity. The new source produces a pre-distorted signal, which compensates the frequency dependence of the cavity.
Following beam studies with barrier buckets below and above transition, the combination of MTE with the barrier bucket manipulation was achieved successfully. The reduction of beam losses at extraction from the PS by an order of magnitude was proven. Additionally, the barrier bucket RF manipulation was modelled with the longitudinal tracking code BLonD to better understand the extraction process.