High Rate Digital Signal Processing for Multi-Channel Microcalorimeters

U.S. national laboratories are developing microcalorimeters as very precise detectors of electromagnetic radiation from near infrared to gamma ray frequencies, with much better energy resolution than existing detectors. Since microcalorimeters are small, they must be fabricated in large, 100-to-1000 channel arrays that, in turn, will require low-cost readout electronics with good energy resolution and high count rate capability. This project will extend the high precision digital readout electronics and digital filter algorithms, previously developed for germanium gamma-ray detectors, to very large microcalorimeter arrays. The objectives are to achieve (1) energy resolutions comparable to existing electronics, but with much higher count rates; (2) automated software for setup, calibration, and monitoring; and (3) a price of $100 per channel. In Phase I, microcalorimeter data was acquired from several research laboratories, and then processed offline and occasionally online. The resolution matched or exceeded the resolution from currently used ¿optimum¿ filters: ~0.07% resolution at low rates (versus 0.7-0.9% for optimum filters) and ~0.13% resolution at higher rates (versus 0.31%). The maximum theoretical count rate with good resolution was 155-1100 counts/s (versus ~ 8 counts/s). A preliminary design of a multi-channel prototype board was created that would meet the cost target. Phase II will complete the multi channel electronics design, build the hardware, and develop on-board firmware and software for multiplexed processing of slow microcalorimeter signals in high speed digital components. Commercial Applications and Other Benefits as described by the awardee: The proposed instrument should have applications in various scientific experiments employing arrays of microcalorimeters for X-ray or gamma-ray spectroscopy. A notable practical application is very precise isotope analysis of nuclear materials, which would make the instrument a valuable tool for nuclear non-proliferation. Similar instruments also could be used for quality control in semiconductor processing.