Measurement of Beam Intensity for Cross Section Measurement Normalization

Determination of beam intensity plays a major role in the normalization of cross section measurements, which are vital in nuclear structure and nuclear astrophysics. By developing a technique to measure beam intensity in cases where Faraday cups cannot be used, this work will improve cross section measurements with MARS (Momentum Achromat Recoil Separator), where most measurements are made close to 0°. In addition to beam intensity determination, this setup will also be used in future experiments with reaccelerated beams at the Texas A&M Cyclotron Institute. In this work, the elastic scattering resulting from the collision of a ⁴⁰Ar beam of 15 MeV/nucleon onto a ¹⁹⁷Au target of thickness 0.1 mg/cm² was measured. This was done by setting up a detector mount with specified angles inside the target chamber of the MARS. Silicon and diamond detectors were positioned at various angles to measure particles’ elastic scattering, while utilizing a Faraday cup positioned at 0° to normalize the measurements made by the detectors. By measuring the ⁴⁰Ar at fixed angles, a comparison of the yield measured to charge collected on the FC can be made, providing a needed normalization for cross section measurements. The analysis was done using ROOT, and the experimental cross section is compared to the Rutherford scattering model. The measured differential cross section showed some enhancement versus the Rutherford differential cross section.



Key words: beam intensity, cross section, diamond detector, Faraday cup, silicon detector.