HiSOR-II, Compact light source with a torus-knot type accumulator ring

We are designing a new ring based on the shape of a (11, 3) torus knot for our future plan 'HiSOR-II'. This ring has eleven 3.6-m-long straight sections though the ring diameter is as compact as 15 m. The emittance reaches down to 20 nmrad with the lattice having bending magnets with combined function. This level of emittance is as low as the conventional compact 3rd generation light source. On the other hand, there are a few potential problems. One of them is that the orbit radius varies in a bending magnet and hence the focusing force are not constant. However, precise calculations by dividing a bending into several sections show that it does not make serious influence to the stored beam. Detailed parameters survey of this ring and estimation of performance confirmed that this new scheme may plausible as a synchrotron light source ring.