internal virtual void MakeIndex()
            {
                // we use RAMDirectory here, because we dont want to stay on open files on Windows:
                  d = new RAMDirectory();
                  RandomIndexWriter w = new RandomIndexWriter(Random(), d);
                  Document doc = new Document();
                  doc.Add(newField("ints", "1", StringField.TYPE_NOT_STORED));
                  w.AddDocument(doc);
                  w.ForceMerge(1);
                  r = w.Reader;
                  w.Dispose();

                  SubR = (AtomicReader)(r.Leaves()[0]).Reader();
            }