Thin foil calorimeter calibration using a 2 MV Van de Graaff accelerator

Abstract

The Laboratory for Laser Energetics at the University of Rochester uses a set of thin foil calorimeters to study the absorbed energy in direct-drive inertial confinement fusion. Each calorimeter consists of two tantalum foils and a copper reference plate of equivalent thermal mass. The foils are approximately 25 μm thick and have a frontal area of approximately 1 cm2. A set of type-E thermocouples is used to make three differential temperature measurements (foil 1-reference, foil 2-reference, and foil 1-foil 2). We have developed a technique to calibrate the response of these thin foil calorimeters “off-line” using proton beams of 800 keV from the 2 MV Van de Graaff accelerator located at the Geneseo Nuclear Structure Laboratory. The calibration constants obtained for 16 calorimeter foils are clustered within ±10% of 7 mV/J. The uncertainty in each measurement is typically less than 5%.