innerRadius: Number/String

innerRadius property allows you to set a Doughnut chart’s inner radius. Value can either be in pixels (number – ex: 100) or percent (string – ex: “80%”). Percent values are relative to the outer radius of doughnut chart.

• Pixel values are Numbers.
• Percent values are strings.

var  chart =  new  CanvasJS.Chart("container",
{
 .
 .
  data: [{
   type: "pie",
   radius:  "90%", 
   innerRadius: "70%"
 
  },
 ]
 .
 . 
});
chart.render();