Layout of the absorbers for the synchrotron light source ANKA

The 2.5 GeV synchrotron light source ANKA is now under construction at the Research Center in Karlsruhe. For a designed current of 400 mA, a power of 250 kW is radiated by the circulating e-beam in the 16 dipole magnets. 90% of the synchrotron radiation (SR) is absorbed by the 32 crotch absorbers in the dipole and the adjacent ante chamber, the remaining 10% by distributed absorbers in the straight chambers. The power per length is up to 50 W/mm for the crotch and 2 W/mm for the distributed absorbers. A special design was needed for the crotch absorbers due to the limited space. The final design is optimized for reduced thermal stress in order to increase the number of maximum possible cycles. The temperature distribution and the stresses were calculated with the finite element program ANSYS. The maximum temperature is 270°C, the maximum strain 0.13%. The achieved strain will be small enough in order to sustain more than 10⁴ cycles, the expected lifetime of the absorbers. The SR entering the beam lines (15 mrad) will be absorbed either by one moveable absorber before the first valve or by the movable radiation protection shutter close to the shielding wall. The power per length is 13 W/mm, respectively 7 W/mm