Fast-Track proposals will be accepted. Direct-to-Phase II proposals will be accepted. Number of anticipated awards: 2-3 Budget (total costs, per award): Phase I: up to $400,000 for up to 12 months Phase II: up to $2,000,000 for up to 2 years PROPOSALS THAT EXCEED THE BUDGET OR PROJECT DURATION LISTED ABOVE MAY NOT BE FUNDED. Summary An important development in the field of radiation oncology is demonstration that ultra-fast dose rate (also known as FLASH) radiation therapy has fewer side effects than regular radiation therapy at the same delivered dose. This finding is under intense investigation globally and a race is underway to understand and subsequently implement this methodology in the clinic. The current devices that measure radiation dose lack response times sufficient to adequately address ultra-fast dose rates of 40-120 Gy/second. This is especially problematic when the total prescribed dose may be only 8-20 Gy. Current medical practice dictates that radiation dose must be given within 20% of the prescription, or else be subject to a formal reportable medical event, as regulated by the United States Nuclear Regulatory Commission. To safely utilize FLASH treatment technique in the clinic, radiation detectors need to be developed that can reliably function at dose rate from 2-10 Gy/minute to 40-120 Gy/second. Additionally, the time structure and the fluence shape of the pulse must be verified to meet FLASH specifications. FLASH radiation delivery’s biological effect may be a function of a unique fine delivery structure that requires ultrafast dose measurement capacity to confirm that the proper, optimal time structure is being used (pulses versus continuous beam delivery).