In accelerator physics, the term acceleration voltage means the effective voltage surpassed by a charged particle along a defined straight line. If not specified further, the term is likely to refer to the longitudinal effective acceleration voltage V ∥ {displaystyle V_{parallel }} . In accelerator physics, the term acceleration voltage means the effective voltage surpassed by a charged particle along a defined straight line. If not specified further, the term is likely to refer to the longitudinal effective acceleration voltage V ∥ {displaystyle V_{parallel }} . The acceleration voltage is an important quantity for the design of microwave cavities for particle accelerators. See also shunt impedance.