Worldwide there is a push for producing medical isotopes using particle accelerators rather than fission reactions. Here we report on the operation of a DC-photogun designed for producing Mo-99 in the Lighthouse facility and commissioned by the Institute for Radio Elements (IRE, Belgium). The gun is based on the successful CBETA design by Cornell University. It is installed at the RI site in Bergisch Gladbach, Germany. As innovative components it contains a photocathode deposition system allowing an automatic transfer of photocathodes into the gun and it uses Novec 4710, a gas developed by 3M as a sustainable replacement for SF6. The injector was installed at the RI site in Bergisch Gladbach, Germany and has produced first e-beam in April 2022. Currently we are ramping up the e-beam power and optimizing the photocathodes. The high-voltage has been conditioned up to >400kV and we see no negative impact of the NOVEC gas. The laser produces 40W at 515nm and 1.3GHz repetition rate and adjustable pulse length. It can deliver pulse trains of 100ns up to CW with variable pulse power onto the cathode. In the MBE system we routinely prepare photocathodes with at least 5% quantum efficiency, well sufficient for the design current of 40mA.The beam diagnostics is currently used to optimize the electron beam. The current focus is on ramping up the power to the design value of 40mA at 350kV.

RI Research Instruments (RI) in partnership with The Canadian Light Source (CLS) have designed a new 250 MeV electron linac to inject into the 0.25-2.9 GeV booster synchrotron. The RF frequency is 3000.24 MHz, the sixth harmonic of the 500.04 MHz booster and storage ring RF cavity frequency, and the main accelerating sections consists of three 5 m constant gradient accelerating structures. The 3 GHz bunching sections and the first accelerating structure are fed by a 40 MW klystron, while structures two and three are fed by a single 40 MW klystron with a SLED RF compression scheme. The electron source consists of a 90 keV thermionic cathode with a 500 MHz modulated grid and a 500 MHz sub-harmonic pre-buncher to synchronise with the booster ring cavity frequency. A single-bunch mode can be delivered, as well as a multi-bunch with up to 140 ns bunch trains of up to 5.6 nC of charge per shot, both at a 1 Hz repetition rate to match the booster ramp cycle. The project is scheduled to bring the linac into operation for top-up injection into the CLS storage ring by mid-2024. This paper will present the design with a special focus on the implementation of a SLED to deliver a recovery mode of operation using only a single klystron.

Medical isotopes are used for diagnostics and cure of tens of millions of patients worldwide every year. For the largest parts they are produced in fission reactors from enriched Uranium-235 leaving behind long-lived nuclear waste. Around the world organizations are therefore working to make medical isotope production more sustainable. RI Research Instruments was commissioned by the Institute for Radioelements (IRE, Belgium) with the design of a superconducting electron linac (75MeV, 40mA, CW) for the industrial production of Mo-99. The short development time and high requirements on availability (23h/d, ca. 360d/y) lead to the use of proven concepts from the Cornell CBETA accelerator and a redundant design with two DC photoguns able to produce the initial electron beam. We report on the innovative aspects of this design. They include a merger feeding e-beam from either of the guns into the linac, a beam splitter dividing the beam 50/50 for illuminating the target from opposite sides, beam dynamics for low-loss beam transport, and a machine protection system able to switch the beam off in <1µs. For the region near the target, where high gamma and neutron doses occur, a radiation-hard design using pillow seals was developed. For risk mitigation prototypes of the critical components were developed and are currently being tested. This involves especially the DC-photogun, which is described elsewhere*. *Test of a DC-photogun Injector for the Lighthouse facility, IPAC 2023.