New UNILAC bunchers delivered
Two radio-frequency buncher cavities for GSI/FAIR's UNILAC linear accelerator have recently been delivered. They are used to shape the ion beams during transfer to the poststripper section (Alvarez structure) and are essential for longitudinal matching to achieve low-loss acceleration and good beam quality, especially at high intensities. The two bunchers, with operating frequencies of 36 and 108 MHz, are intended to replace the existing devices, which have been in operation for about 25 years, and thereby reducing the operational risks.
A combined process of CNC milling and thick-film electroplating was developed to produce the spirals, which allows the exact reproduction of a free geometry while at the same time integrating the cooling sufficiently. The design frequencies of the cavities were achieved on instantly with deviations of only 8 and 6 per mil. This was enabled by verifying the design of the 36 MHz spirals with two prototypes made of plastic using 3D printing. The experience gained in this project will also benefit the new Alvarez accelerator currently under construction. After passing the factory acceptance test (FAT), both cavities will now be fully equipped and prepared for the upcoming high-performance tests. (CP)