For a project as ambitious and complex as CERN's Large Hadron Collider (LHC), setbacks are likely, in fact almost inevitable. However, the delay would be worth it according to Bob Cousins, deputy to the scientific leader of one of the sensor experiments as it would allow the sensors to be made "even more perfect than before".
While the sensor may indeed be nearing perfection, the overall design is still experiencing problems. Leaks in the insulating layer's vacuum were discovered in sectors 8-1 and 2-3 that would prevent it from properly operating. This new problem will delay the restart from October to November.
The leaky sectors will be needed to be warmed from their current temperature of 80K to room temperature in order to plug the leaks. The near-vacuum of the beam pipe will not be impacted.
The LHC is cooled with liquid helium injected into an insulating layer which surrounds the beam tube and is kept at near-vacuum. This allows the LHC beam tube to be cooled to temperatures colder than that of outer space. Last fall the particle collider was briefly turned on, but a cooling circuit melted leading to the damage to the electrical and cooling systems. Scientists initially wanted to restart the LHC in April, but the large extent of the damages necessitated more repairs.
The cost of all the repairs thus far, though, have been small compared to the $10B USD estimated cost of building the LHC. Current repairs have run over $35M USD, according to reports.
The LHC sits on the border between Switzerland and France and consists of a 17 mile long ring. The ring is capable of imparting energies of 7 TeV onto particles, making for potential collisions at unprecedented energies. Scientists hope these collisions will help them unlock physics secrets including understanding how dark matter and energy work and the discovery of the law theorized "God Particle" -- the Higgs boson.
The accelerator, when active will continue to close each winter, to avoid the prohibitively high energy costs. The accelerator requires massive amounts of power to operate.