From The Stargate Omnipedia
Asgard energy weapon
Shaped charge of Asgard
design which emits an energy-based explosive powerful enough to puncture quantum realities. One such device was loaned to Stargate Command
by the Asgard, with assurance that the weapon would be returned to them after it was used.
Ripple Effect - Kvasir supervises the use of an Asgard energy weapon so that a hole may be cracked between quantum realities.