A digital display device for displaying content associated with multiple sets of sources of content is described herein. In one embodiment of the invention, a method for instance based access control in a persistent application resource can be provided. The dual ion trap according to the present invention includes two linear ion traps, one positioned before an analytic quadrupole and one after the analytic multipole. A refrigerator chamber penetrates through the thermal shield unit and to which the cryocooler is attachably and detachably provided.