Status of a carbon Ξ^-atomicX-ray measurement at J-PARC (2)

In J-PARC E96 experiment, we will make precisely measure X rays from carbon atoms by using a Ge detector array, the modified Hyperball-X. We need a high-precision energy calibration method to measure the energy shift of X rays from the ^- carbon atoms in accuracy of 0.1 keV. We use LSO pulsers for the energy calibration.

Lu₂SiO₅ (LSO) scintillator contains natural radioactive nuclide of ¹⁷⁶Lu. The LSO pulser provides a timing signal for -ray emissions from ¹⁷⁶Lu by detecting a -ray. Through a - coincidence measurement between a LSO pulser and a Ge detector, we can discern rays (88 keV, 202 keV, 307 keV) and X rays (~54 keV) from ¹⁷⁶Lu efficiently even in the in-beam condition. Those -ray and X-ray peaks are used for in-beam energy calibration.

I studied accuracy of the energy calibration in the LSO pulser method under the E96 conditions such as Ge detector counting rates and a necessary calibration frequency. We need to calibrate the low energy region of 50-150 keV for atomic X rays. First, I accumulated ADC data with LSO and checking sources (¹³³Ba, ¹⁵²Eu, etc.) without beam and I analyzed them to understand the ADC channel dependence of the peak efficiency, mixing of different X-ray transitions, and the deformation of peak structure. Second, I analyzed the data accumulated in E96 commissioning experiment in June and determined the accuracy of the energy calibration under the actual E96 conditions. In the meeting, I will also report the results of these studies.