Bi-metal foil for a beam intensity/position monitor, method for determining mass absorption coefficients

A method for determining mass absorption coefficients, the method comprising:

• a) measuring the absorption of an incident radiation beam by a first metal and a second metal as a function of a first energy and a second energy, wherein the first metal and second metal comprise an upstream bi-metal foil;
• b) calculating the relative first metal thickness;
• c) using the relative thickness of the first metal foil as a target value to fit the mass absorption coefficients for the first metal foil based on absorption measurements performed at multiple energies across the first metal foil's absorption edge boundary;
• d) perform repeat steps a-c on a free standing downstream single metal foil which is positioned downstream of the upstream bi-metal foil;
• e) using the free standing downstream single metal foil absorption measurements, bulk first metal density and bimetal foil fit coefficients to determine the free standing downstream single metal foil thickness;
• f) using the free standing downstream single metal foil to conduct a high resolution scan from just below one of its absorption edges and extending 1 or more keV above the absorption edge;
• and
• g) using the downstream single metal foil absorption measurements and predetermined thickness to compute mass absorption coefficients below its absorption edge.