NSLS in-vacuum undulators and mini-beta straights

We review the work carried out in the X13 R&D Straight Section of the NSLS X-Ray Ring on small gap in-vacuum undulators (IVUNs). Then we discuss: (1) plans to replace the pure permanent magnet undulator in X13 by a hybrid design providing stronger magnetic fields, enhancing the tunability of the device; (2) plans to install hybrid IVUNs in the two RF straights of the X-Ray Ring, increasing the number of insertion devices in the X-Ray Ring to eight; (3) the possibility of reducing the vertical beta function in the X13 straight from 0.33 m down to 0.16 m. This reduction in beta function would allow us to decrease the usable undulator gap from 3 mm down to 2 mm, further increasing the tuning range