Further measurements of Bremsstrahlung from the insertion device beam lines of the advanced photon source

Bremsstrahlung is produced in the Advanced Photon Source (APS) storage ring when the positron beam interacts with the storage ring components or with the residual gas molecules in the storage ring vacuum. The interaction of the positrons with the gas molecules occurs continually during storage ring operation. Bremsstrahlung is important at the insertion device straight sections because the contribution from each interaction adds up to produce a narrow mono-directional beam that travel down the beam lines. At the APS, with long storage ring beam straight paths (15.38 meters), gas Bremsstrahlung in the insertion device beam lines can be significant. The preliminary results of the Bremsstrahlung measurements in the insertion device beam lines of the APS was presented at SATIF-3. This paper presents the results of further measurements at the two insertion device (ID) beam lines with higher statistics in the data collection. The results, along with the results from the four previous independent Bremsstrahlung measurements, enabled us to conclude upon the various reasons causing this variation. (author)