Second virial coefficient of He4 in the temperature range from 2 to 20 K

We pre~e nt p re limin a ry values for Ih e seco nd viria l coeffic ie nt of He' in th e te mpe ra tu re range from 2 to 20 K . 1 hey wel e derI ved fro m rece nt so und ve lOC It y meas ure me nt s in Ih e gas made by Plumb a nd Cata la nd uSIn g a n ultras onI c Int erfe ro meter.