MEASUREMENT OF GAS BREMSSTRAHLUNG FROM ELECTRON STORAGE-RINGS

Bremsstrahlung is produced in electron storage rings when the particle beam interacts with the storage ring components or with the residual gas molecules in the storage ring vacuum, The interaction of the parti cle beam with the gas molecules occurs continuously during storage rin g operation, At straight sections of a storage ring, the gas bremsstra hlung contribution from each interaction adds up to produce a narrow m onodirectional photon beam that travels down the beamlines. At the Adv anced Photon Source (APS), where the stood electron beam energy is 7 G eV, gas bremsstrahlung generated in the straight sections of the inser tion device beamlines, which is a total of 15.38 m in effective length , can be significant. This paper presents the results of the bremsstra hlung spectrum and energy measurements from the insertion device beaml ines of the APS using a hermetic lead glass calorimeter, The calorimet er consists of 25 lead glass blocks, each 6.3 cm x 6.3 cm x 35 cm, sta cked into a 5 x 5 array. Phototubes connected to the lead glass blocks collected the signals. The calorimeter is calibrated using the maximu m energy of the observed bremsstrahlung spectrum. The total energy rad iated and the bremsstrahlung spectrum There measured as a function of the storage ring beam current: for both electrons and positrons of 7 G eV energy. Vacuum in the straight section was continuously monitored, and measurements to determine the nature of the residual gas inside th e storage ring were performed. The measured bremsstrahlung spectra are fitted to a function that shows an approximate l/E behavior, The gas bremsstrahlung rate from the APS undulator beamline straight path of 1 5.38 m is measured as 60.0 +/- 2.0 GeV/s/nT/mA. Significant contributi on of bremsstrahlung from sources other than the residual gas molecule s is observed. The maximum bremsstrahlung energy measured in a beamlin e during the experiment is 369.0 +/- 22.0 GeV/s/nT/mA.