Convert `Ellipsoid` into `EllipsoidGraphics`

I am so confused about definition of these two EllipsoidGraphics and Ellipsoid I want to add an simple Ellipsoid into my map and find its intersection with a ray, I know that I must add an entity to map,I also know that each entity can have EllipsoidGraphics property, But I don’t know how to Convert Ellipsoid into EllipsoidGraphics

Can some one helps me with it? this is a sample code that I use but it does not show any thing

var elip =new Cesium.Ellipsoid(300000.0, 300000.0,200000.0);

var redSphere = viewer.entities.add({
    name : 'Red sphere with black outline',
    position: Cesium.Cartesian3.fromDegrees(-107.0, 40.0, 300000.0),
    ellipsoid : {
        radii : elip,
        material : Cesium.Color.RED.withAlpha(0.5),
        outline : true,
        outlineColor : Cesium.Color.BLACK

can Anyone give me some hints please?