Experimental Characterization of Silicon Strip Detectors for the Proposed Deuteron Charge Radius Measurements*

The ∼6σ discrepancy between the smaller deuteron radius measured by muonic deuterium spectroscopy and the larger value from electron scattering and spectroscopy experiments is known as the "deuteron charge radius puzzle,'' similar to the well-known "proton charge radius puzzle." We made measurements to support the design of a recoil detector to be placed inside the target cell of the proposed DRad experiment at Jefferson National Lab to enable precise detection of low-energy recoil deuterons, ensuring the elasticity of the electron–deuteron (e–d) scattering process. A large-area silicon strip detector (SSD) was tested with alpha particles from a 241Am source from room to cryogenic temperature in a vacuum chamber on the 59° beamline at the Triangle University Nuclear Lab (TUNL) Tandem Accelerator, using a custom-designed and fabricated aluminum plate to mount the detector to the cold head. The SSD had 756 AC-coupled strips combined into 16 channels, instrumented with a Mesytec MMR pre-amplifier to record the alpha spectra, for evaluating energy resolution. The detector's energy resolution improved with decreasing temperature.