Cryogenic microcalorimeters for precision measurements in nuclear science and other disciplines
Abstract: A microcalorimeter is a sensor that measures deposited energy by transducing it into a temperature rise that can be sensed electrically. When operated at temperatures near absolute zero, thermal and electrical noise sources are suppressed and microcalorimeters can perform extremely precise (E/DE > 1,000) energy measurements of single photons, particles, and radioactive decays. Advances in milliKelvin cryogenics and powerful readout techniques similar to those used in quantum computing are now enabling practical microcalorimeter instruments based on arrays of hundreds-to-thousands of sensing elements. With different optimizations, these instruments can be used for uv/vis/nir, x-ray, gamma-ray, and decay-energy spectroscopy, as well as for far-infrared and millimeter-wave detection. In this seminar, I review recent work at NIST on microcalorimeter sensors. In addition to describing the physics of microcalorimeters and their readout, I will discuss a range of applications, emphasizing work in nuclear science. For example, microcalorimeter instruments are now deployed at Los Alamos and Idaho National Laboratories and have been used to analyze a wide range of nuclear materials. In a recent campaign to assay actinide reference samples, microcalorimeter gamma-ray sensors surpassed the precision and accuracy of well-established germanium detectors.
Bio: Joel Ullom received his A.B. in physics from Princeton University in 1993 and his Ph.D. in physics from Harvard University in 1999. He is presently a group leader at the National Institute of Standards and Technology (NIST) in Boulder, Colorado and a Lecturer in the Department of Physics at the University of Colorado Boulder. His research is focused on low temperature sensors, low temperature electronics, and cryogenic systems. He has created and disseminated a variety of instruments based on arrays of cryogenic sensors with applications in metrology, astrophysics, materials analysis, and synchrotron science. His honors include a Presidential Early Career Award for Scientists and Engineers, the R. W. Boom Award from the Cryogenic Society of America, an Arthur S. Flemming Award, and the 2023 Joseph F. Keithley Award from the American Physical Society.