Better Physics

Dr. John Kovac, Assistant Professor of Astronomy and Physics at Harvard University, presented a two-part talk. First, he gave a gripping account of detector development, installation, and use at the South Pole Telescope; then he described his course in which undergraduates build a microwave horn, assemble the necessary electronics, and detect the cosmic microwave background.

Detecting the Cosmic Microwave Background at the Frontier of Cosmology and in the Classroom

Author: John Kovac  (Harvard University, Departments of Astronomy and of Physics)

The 3K blackbody Cosmic Microwave Background (CMB), while exceedingly faint, is the most abundant light in the Universe, permeating all of space as a relic of the hot, dense, primordial fireball. Its detection in 1965 established the Big Bang as the standard model of cosmology and earned its co-discoverers Penzias and Wilson a Nobel Prize. Over the past two decades, advances in detector technology driven by CMB research have produced telescopes with ever-increasing numbers of photon background-limited microwave detectors, capable of mapping fine structure of the CMB to micro-Kelvin precision. These have had enormous impact, determining the geometry of the universe, quantifying the dark matter and dark energy that dominate it, and detecting the faint polarization arising from the primordial seeds of structure. The current frontier is defined by new arrays of thousands of superconducting, polarized detectors producing maps approaching nano-Kelvin precision. In this decade, these measurements will answer questions about the physics driving the earliest moments of the Big Bang and will survey the large-scale structure of the universe, determining neutrino masses and constraining the nature of dark energy. The advanced detector technology fueling this frontier provides superb device-physics training for graduate students and postdocs working on current-generation CMB telescopes. At the same time, careful experimental techniques developed for CMB observations can now be combined with inexpensive high-quality satellite TV detectors to allow even undergraduates to detect the CMB, reproducing Penzias and Wilson’s famous discovery. I describe one such undergraduate class at Harvard, which builds CMB telescopes from scratch in a few weeks with a modest budget, teaching students about microwave techniques and detectors and allowing them to find their own evidence for the Big Bang.  — SLIDES

Dr. Zoran Ninkov, Professor in the Center for Imaging Science at Rochester Institute of Technology, described his year-long course in which his students learn and use basic physics and engineering to design and build a working CCD camera. For more information, see his A full-year university course sequence in Detector Array Theory, Camera Building, and System Testing.

Coupling physics to understanding the performance of detector arrays

Author:  Zoran Ninkov (Rochester Institute of Technology)

Over the last few decades developments in microelectronics have led to the development of arrays of detectors that can be used to measure unprecedentedly small levels of signal. Such arrays have been used to detect electromagnetic radiation ranging in energy from the X-ray through sub-millimeter wavelengths and also particles. Perhaps nowhere have the improvements been more astonishing than in devices available for the visible part of the spectrum (400 — 1000 nm). The most successful detector array in this spectral region is the Charge Coupled Detector (CCD) whose inventors were recognized with the Nobel Prize in Physics in 2009. In this talk I will review some of the detectors and technologies that are used in low light level imaging. I will also describe a full year sequence of classes (i.e. a theory class, a CCD camera building class and a CCD camera performance measurement class) that students at the Rochester Institute of Technology can take to make them knowledgeable as to the physics underlying the operation and performance of such detector arrays. Finally I will discuss the associated laboratory classes that students must take to measure the performance of the camera they have built and what aspects of fundamental physics are integrated into their understanding. These classes have been taken by both calculus and non-calculus trained students. The classes appeal to students with both types of backgrounds as it couples an understanding of physics to something that they build and use.  — SLIDES

Dr. George Ricker, Senior Research Scientist in MIT’s Kavli Institute for Astrophysics and Space Research, described the work of four of his graduate students. Detector development was central to the Ph. D. education of each, opened new frontiers, and led to a career and leadership in astronomy or space science.

Gamma-ray Bursts, Black Holes, and Exoplanets: How CCD Detectors have Revolutionized Astronomy

Author:  George Ricker (Massachusetts Institute of Technology)

I will tell the story of my research group’s role in the development of astronomical charge-coupled detectors (CCDs) by relating the contributions of four MIT research students to projects which we have undertaken together over the past three decades. These projects have empowered observations extending over four decades of the electromagnetic spectrum, enabling discoveries ranging from gamma-ray burst emitting collapsars at cosmological distances, to accretion-driven black holes in the Galaxy, and to exoplanets in the solar neighborhood. This story will illustrate the key contributions which student researchers can make when a novel detector technology arrives on the scene. Finally, I will also describe some of the ways in which their early education in these possibilities has impacted my students’ future careers as astronomers and experimental physicists.  — SLIDES

The lead-off speaker, Dr. James Beletic, Director of Astronomy & Civil Space at Teledyne Imaging Sensors (TIS), also chaired the session. He gave a fine overview of optical and infrared detectors and their physics.

The basic physics of astronomical detectors, our eyes on the Universe

Author:   James Beletic (Teledyne Imaging Sensors)

The universe is an amazingly huge place. While humankind has directly explored Earth’s sister planets with space probes, we don’t have the means to venture beyond the solar system, and so almost all information about the universe comes from sensing light that happens our way. Astronomy is constantly striving to find better ways to sense the feeble amount of energy from distant stars and galaxies. This quest has led to a new generation of large telescopes on the ground and in space. Possibly more important than the development of bigger telescopes is the rapid advancement in solid state detector technology. In the x-ray, visible and infrared wavelengths, the most advanced detectors are based on two fundamental technologies: (1) nearly perfect detector materials that efficiently convert photon energy to electrical charge, and (2) very sensitive transistors that convert a few electrons into a measurable voltage. This talk presents the basic physics of astronomical detectors and provides an introduction to the more specialized talks that follow in this session of presentations. Since detectors of light are critical to nearly every aspect of scientific research and involve a wide range of physical phenomena, this session of talks will provide the audience with physics lessons that can be readily incorporated in an undergraduate physics curriculum.        — SLIDES