Year
2016
Abstract
Cesium-137 has been identified as the single most worrisome radioactive isotope in use today, with blood and research irradiators accounting for 99% of all Cs-137 activity in the U.S. Stellarray Inc. is developing a Self-Contained Blood Irradiator (SCBI) and three self- contained (cabinet) research irradiators to replace Cs-137 unitsii. The key innovation is Stellarray’s Flat Panel X-ray Source (FPXS), a broad source of x-ray flux in which cathode arrays in a glass panel shower high-energy electron beams over a metal anode assembly that has one side facing the vacuum enclosure of the source and the other side facing the outside environment, where it is directly coupled to ambient or closed-loop cooling. The x-rays emit back up from the anode and out past the cathodes through a top glass window. The flux- emitting surface area can be approximately the same as the target surface area and the source can be brought close to the target. In SCBI, blood bags or other blood containers are placed in a tray and moved on a sliding drawer between upper and lower FPXS panels inside a radiation-shielded cabinet. The source panels emit flux to both sides of the blood bags at close proximity to deliver a highly uniform dose. These source and irradiator designs provide advantages in power efficiency, size, weight, ease of use, economy and reliability that are important to users in the blood banking community. Research irradiators are being developed to address a variety of radiobiology and radiochemistry user needs for which Cs-137 remains the preferred flux source. One model will provide sustained high dose rate flux, while another is being developed for applications that require higher energy flux (200-350 kV). The third model uses a variation of the FPXS in which individual cold cathodes in a matrix array emit electron beams to small areas on the anode, with digital switching between the cathodes. A standard micro-titer plate can be placed on top of the source and collimated x-ray flux delivered to individual wells in the plate, with variation in flux energy, dose, time and modulation between wells. This design will offer research users much higher throughput and experimental variation than is possible with an isotope irradiator.