Energy Loss of a Charged Particle Traversing Superconductors

Abstract

The energy loss of a charged particle traversing superconductors is calculated by taking account ot the London equations of the superconductivity. A small amount of excess energy loss, which is of the order of 10-~ or less, is expected, in comparison with the energy loss in normal materials. As ·this is just the limit of observability, an accurate measurement of the. energy loss may give us informa­ tion on the value of the characteristic constant of a superconductor, A, introduced by London. The excess loss relative to the normal energy loss is estimated as about 2m/e2nA, where m is the mass of an electron and n the density of electrons. very low frequencies of the electromagnetic field caused by a charged particle, whereas the main contribution to the energy loss comes from its optical frequencies. The present authors2l have also considered similar problems, independent of Ivanenko and Tsrtovich, paying particular attention to the superconductor. As the influence on the energy loss is much larger in the latter case than in the case of ferromagnetic materials, we want to publish our result, hoping that observations of the energy loss, if accurate enough, may serve to determine a constant characteristic to the superconducting state. The energy loss of a charged particle in superconductors is different from that in normal matter in the following respects. It is well known that the energy loss due to electronic excitation is proportional to njm, where n is the density of electrons and m the mass of an electron. In a superconductor the so-called superelectron behaves in a different way from normal electrons, so that the effective mass of the former, m., is different frotti m. Hence the contribution from superelectrons is considered to be proportional to n.jm., where n, is the density of superelectrons. As it is believed to be m.;$10-3 m, one might think that superelectrons would contribute to the energy loss great deal, even though n, is far smaller than the density of whole electrons, n. However, the characteristic behaviour of superelectrons almost disappears in the optical region where the main contribution to the energy loss comes from normal electrons ; superelectrons play an essential role at lower