Physics 111 Advanced Laboratory. Professor Sumner Davis This video accompanies the Gamma Ray Spectroscopy Experiment, providing students with an introduction to the theory, apparatus, and procedures. The purpose of this experiment is to measure the mass attenuation coefficients of several materials using gamma ray sources. First you will perform some tests to show the effect of various equipment settings. You will then use the known sources to calibrate your detector, and verify the inverse square law. Finally, you will make some measurements that will allow you to calculate the mass attenuation coefficients for several materials at several energies. In this apparatus, the gamma rays enter a NaI scintillator crystal, which converts them into many lower energy photons. These photons travel through the crystal to the photocathode of a photomultiplier tube, where they are converted into electrons by means of the photoelectric effect. The photo-electrons are sent through a series of electrodes where the number of electrons is multiplied. At the anode, a pulse of current is produced, and then counted. http://advancedlab.org

The "Rosenfeld Effect" Energy Symposium discussed the role of increased energy efficiency in California, in China, and on a global scale; the intersection of energy and safe drinking water in the developing world; the twin challenges of mitigating climate change and sustaining orderly markets in fluid fuels; how to turn good science into good politics; and defining, predicting, and coping with global warming. This seesion features Mark Levine - Director, Environmental Energy Technologies Division, LBNL; Ashok Gadgil - Senior Staff Scientist and Group Leader, Environmental Energy Technologies Division, LBNL & Adjunct Professor, Energy and Resources Group, UC Berkeley. [events] [glopubaffairs] [scitech] ...