Speaker
Description
The Paul Scherrer Institute PSI is the largest research institute for natural and engineering sciences within Switzerland. We perform cutting-edge research in the fields of future technologies, energy and climate, health innovation and fundamentals of nature. By performing fundamental and applied research, we work on sustainable solutions for major challenges facing society, science and econ-omy. PSI is committed to the training of future generations. Therefore, about one quarter of our staff are post-docs, post-graduates or apprentices. Altogether, PSI employs 2300 people.
Proton therapy, at PSI (SIN) initially introduced in 1984 for eye treatments, was significantly expand-ed in 1996 with the installation of Gantry 1, enabling the treatment of deep-seated tumors. Around this time, the innovative spot-scanning technique was developed, allowing for more precise target-ing of tumors.
Due to the remarkable success of proton therapy, the idea emerged in 1999 to build a dedicated accelerator exclusively for therapeutic and clinical studies use, enabling year-round treatment. This vision led to the launch of the PROSCAN project in 2000, which included several key developments:
• COMET, a 250 MeV accelerator designed specifically for therapy
• A new beamline to the new medical areas including Gantry 1
• Construction and development of Gantry 2, optimized for fast scanning
• A new eye-treatment facility named OPTIS2
In 2007, the first patient was successfully treated with protons delivered by COMET. Although COMET—developed as a prototype by the German company ACCEL based on specifications from PSI—was designed to provide a proton beam current of 500 nA, and briefly up to 1000 nA, it initially struggled to maintain a stable beam above 400 nA. Additionally, the high-voltage components known as extraction elements encountered significant issues when operating near 500 nA. Many of these early challenges were likely linked to the ion source, which is a cold cathode Penning ion source design.
These serious problems with the ion source led me to one of my favorite sayings:
"The origin of all evil is the source."
Over the past 20 years, the continued development of COMET and its subsystems has been driven by ongoing learning, technical hurdles, and groundbreaking innovations—such as the introduction of the new boron carbide degrader (B4C). This article presents not only operational statistics but also highlights key improvements and major outages, offering in-depth insights into the challenges of beam stability and ion generation at the source.