Reconsideration of Tamm's problem in Cherenkov radiation

Cherenkov radiation is one of most basic and well-known radiation phenomena generated from dielectric medium with which charged particles interact at a constant velocity. In recent years this radiation is widely applied to many research areas, not only particle physics and high-energy accelerators but also medical and industrial applications. The radiation mechanism of Cherenkov radiation was experimentally and theoretically well verified in the past researches. However, it is little known that the Tamm problem on Cherenkov radiation has been enthusiastically investigated at a long time in history of the theoretical development on the radiation mechanism with a finite length of dielectric medium. The Tamm problem is related to the Tamm approximation in the derivation of the radiation intensity under experimental conditions, and it may offer mysterious and unphysical results. Nowadays, the Tamm problem has been solved after the historical long investigations by several experts. The purpose of this report is to revisit the Tamm problem and to re-recognize what is the Tamm problem, and to offer some cautionary notes on the Tamm problem in calculations under the experimental conditions from the point of view in diagnostics and instrumentations of high-energy accelerators. (author)