Mission

The front ends, the interface between the light source and the optics, holds many indispensable components to user experiments with safety and stably, for example, the main beam shutter, slits, valves, beryllium windows and so on.  However, almost every component is located within the ring tunnel under the severe radiation environment, where the entry is usually restricted.  Therefore, it is the basic mission to maintain and improve the front ends, considering the limitation and the life of the components properly, so that users might not be interfered to enjoy their experiments.  On the other hand, the SPring-8 insertion device, even the standard type, produces a total power of 13.7 kW with a peak power density of 550 kW/mrad² (in case of the very long insertion device at BL43LXU, a total power of about 50 kW with a peak power density of 3 MW/mrad²), and the beam divergence is extremely small. Thus, handling this huge power and monitoring the X-ray beam position accurately and continuously are the major technical challenges in the engineering of the front ends.

 

Activities

Grazed angle technology, dispersing power into area by inclining absorbing surfaces, is the basics of design for high-heat-load components. In addition to this technology, we originally have contrived to insert wire coils in cooling channels to enhance the heat transfer characteristics at cooling surfaces.  Consequently, the heat transfer coefficient of this wire coil technique could be increased by four times than plain pipes with moderate pressure loss but without any special techniques. Combining these technologies, we can deal with almost 10 kW of power per one meter in the light axis direction. Moreover, to increase the cooling ability within a more compact space, volumetric heating technology, which dissipates high surface heat flux into depth by utilizing a low-Z material, has been being developed and a combination component of fixed mask and absorber was put to practical use. The front ends team has been making the most use of a finite element analysis of ANSYS for the engineering of these technologies. Recently, a procedure to predict the fatigue life of high-heat-load components made of GlidCop (dispersion-strengthened copper with aluminum oxide) within a factor of 2 has been successfully established by consolidating the results of experiments and elastic-plastic analyses. Following this fruitful outcome, we are now starting not only to investigate thermal limitation of other high-heat-load components but also to develop a new high-heat-load handling technology.
As to the beam monitoring technology, a simultaneous photon beam diagnostic system has been prepared satisfactorily, which is composed of photo-emission type XBPMs in every front end, optical cables spread over the experimental hall, and electric circuits.  Although this type monitor is influenced fundamentally by the change of insertion device gap, an excellent performance is positioning resolution (less than 0.5~1 μm), ring current dependence (less than 1 μm), filling pattern dependence (less than 1.2~3.5 μm), and stability (less than 3~5 μm/day) by optimizing the configuration of detectors to the SPring-8 light sources. By using this system, a long-term stability is checked by fixed point observation at the beginning of each operation cycle and a short-term orbit variation caused by phase driving of the insertion device e.g. is also observed. Basically, any information on this system is available to users. We are working on development of a pulse-by-pulse XBPM having microstripline structure in order to meet requirements of time-resolved experiments that have come to be carried out more actively.
In addition to the development of these key technologies, the prescribed maintenance work for vacuum components, driving components, high-heat-load components, cooling and compressed air system, and interlock system, is executed carefully during a long shutdown period,