Terminal voltage calibration of a 3 MV Tandetron accelerator at Sichuan University, China

The 3 MV Tandetron accelerator at Sichuan University has been calibrated across a wider terminal voltage range (500–2100 kV), employing the narrow resonance of the ¹³C($\alpha ,n$)¹⁶O reaction along with neutron threshold measurements from ⁷Li($p,n$)⁷Be, ¹³C($p,n$)¹³N, and ¹⁹F($p,n$)¹⁹Ne reactions. The calibration demonstrates excellent reproducibility of energy measurements over a two-year period, with about 0.12 keV variation in repeated measurements at $E_{\alpha }=1055.63$ keV. However, an approximate 5 keV shift observed in the ⁷Li($p,n$)⁷Be threshold energy over seven years demonstrates the necessity for periodic recalibration. Given the sub-keV reproducibility demonstrated over a two-year period, we recommend recalibrating at least every two years to ensure ongoing energy accuracy for this accelerator. The calibration parameters are a = 0.9918 ± 0.0005 and b = 4.3104 ± 0.5319 kV, where V = $a\cdot V_{\text{set}}$ + b. This work establishes a robust calibration framework that ensures reliable accelerator performance for nuclear physics researches and applications.