Beam diagnostics and collector for the electron cooler of the cryogenic storage ring CSR

The CSR electron cooler will be employed both for phase space cooling and as a target for electron-ion collision experiments. Aligning the beams is essential for both applications and, therefore, the cooler features two rotating wire scanners for beam position determination. In the course of this work their design has been finalised. A scheme has been developed to calculate the transverse beam location from two measured rotation angles. This can be utilised to determine the centres of the electron and ion beams. While in the former case a signal is directly induced at the wires, identification of the latter depends on an increasing restriction of phase space with advancing rotation. A procedure is proposed to detect the decline in ion intensity with the CSR’s current pick-up. Furthermore, the electron collector of the cooler has been designed and assembled. A Wien filter is included to minimise backstreaming of secondary electrons, which will prolong the lifetime of the GaAs photocathode. Calculations and a simulation were conducted to optimise its design. Additionally, an analyser cup allows for beam profile and energy distribution measurements. From this, among others, the electron density can be computed, which is necessary for rate coefficient calculations