The selection of 14 beamlines in Phase I
The construction of HEPS beamlines is to satisfy some major demands of the nation and to further cutting edge scientific development. It will support state-of-the-art research in multiple disciplines and facilitate technology innovation and development. Considering the needs of the users and science as well as the construction fees and time, after discussion experts and relevant professional groups selected fourteen public beamline stations to be constructed with auxiliary facilities in phase I.
User professors of relevant areas were gathered for discussion, which clarified scientific goals for each station to guide the beamline design. During the design process, because of the uniqueness of HEPS, thermal load and stability were considered essential, and the low-emittance storage ring's extremely high requirements on the optical components of beamline also became a difficulty in design.
With the support of HEPS-TF project, problems in high thermal load monochromator technology and high-precision optical metrology and bending technology have been solved. Firstly, as a light source close to the diffraction limit, the beamline design of HEPS need to consider the coherence problems. To achieve certain stability, we learned lessons from successful or failed experiences in the world and of other facilities, and then used a placement method of optical components different from that of the generation three and earlier ones, i.e. a vertical-placing-and-horizontal-deflection method. This reduces the influence from external vibration and eliminates transformation caused by gravity. In beamline stations with small focus spots, we comprehensively considered various measures to stabilize light spots on the sample, like the use of secondary light sources and high-performance optical components. Lastly, error distribution was carried on the main optical components on the beam line according to the current technology level, achieving the highest performance-price ratio when the design specifications were met.
The construction content of first batch of beamline stations