D3Js vertical collapsible graph node overlap due to bigger radius - html

Question

I have created a D3Js vertical collapsible tree by taking the code from this site. I want to increase the radius of the nodes. Currently, its at r=10 and would like to increase it to 30. Which results the neighbour nodes to overlap with each other like below.. How can I increase the distance between each node so it doesnt overlap with each other?
Thank you
function buildVerticalTree(treeData,treeContainerDom){
var margin = {top :40,right:120,bottom:20,left:120};
var width = 960 - margin.right - margin.left;
var height = 700 - margin.top - margin.bottom;
var i = 0, duration = 750;
var tree = d3.layout.tree()
.size([height,width]);
var diagonal = d3.svg.diagonal()
.projection(function(d){
return [d.x, d.y];
});
var svg = d3.select(treeContainerDom).append("svg")
.attr("width",width+margin.left+margin.right)
.attr("height",height+margin.top+margin.bottom)
.append("g")
.attr("transform","translate("+margin.left+","+margin.top+")");
var root = treeData;
update(root);
function update(source){
var nodes = tree.nodes(root).reverse();
var links = tree.links(nodes);
nodes.forEach(function(d){
d.y = d.depth * 100;
});
var node = svg.selectAll("g.node")
.data(nodes,function(d){
return d.id || (d.id=++i);
});
var nodeEnter = node.enter().append("g")
.attr("class","node")
.attr("transform",function(d){
if(!source.x0 && !source.y0)
return "";
return "translate("+source.x0+","+source.y0+")";
})
.on("click",nodeclick)
nodeEnter.append("circle")
.attr("r",10)
.attr("stroke",function(d){
return d.children || d._children ? "steelblue" : "#00c13f";
})
.style("fill",function(d){
return d.children || d._children ? "lightsteelblue" : "#fff";
});
nodeEnter.append("text")
.attr("y",function(d){
return d.children || d._children ? -18 : 18;
//return 0;
})
.attr("dy",".35em")
.attr("text-anchor","middle")
.text(function(d){
return d.name;
})
.style("fill","black")
.style("fill-opacity",1e-6)
var nodeUpdate = node.transition()
.duration(duration)
.attr("transform",function(d){
return "translate("+ d.x+","+ d.y+")";
});
nodeUpdate.select("circle")
.attr("r",10)
.style("fill",function(d){
return d._children ? "lightsteelblue" : "#fff";
});
nodeUpdate.select("text")
.style("fill-opacity",1);
var nodeExit = node.exit().transition()
.duration(duration)
.attr("transform",function(d){
return "translate("+source.x+","+source.y+")";
})
.remove();
nodeExit.select("circle")
.attr("r",1e-6);
nodeExit.select("text")
.style("fill-opacity",1e-6);
var link = svg.selectAll("path.link")
.data(links,function(d){
return d.target.id;
});
link.enter().insert("path","g")
.attr("class","link")
.attr("d",function(d){
if(!source.x0 && !source.y0)
return "";
var o = {x:source.x0,y:source.y0};
return diagonal({source:o,target:o});
});
link.transition()
.duration(duration)
.attr("d",diagonal);
link.exit().transition()
.duration(duration)
.attr("d",function(d){
var o = {x:source.x,y:source.y};
return diagonal({source:o,target:o});
})
.remove();
nodes.forEach(function(d){
d.x0 = d.x;
d.y0 = d.y;
});
}
function nodeclick(d){
if(d.children){
d._children = d.children;
d.children = null;
}else{
d.children = d._children;
d._children = null;
}
update(d);
}
}//end of buildVerticalTree
buildVerticalTree(that.objectList, "#tree");