Kamran Vaziri and Don Cossairt
The Neutrinos at the Main Injector (NuMI) experiment was beset by three problems that delayed data collection by several weeks. The first one was caused by a slight back pressure and a check valve that was mounted incorrectly. Even though this job did not require removing the horn shielding, the task of removing the deionization system’s 10-micron resin beads that migrated into the wrong parts of the NuMI horn water-cooling system ended up incurring 791 person-mrem. This amount of total effective dose equivalent (TEDE) was significant and was accumulated over many hours of work in relatively low dose rates.
The second problem was caused by a broken ceramic connector on the horn that was 75 rem/hr on contact. This involved the removal and replacement of the failed connector and included practice with mockups because of the need to work “hands-on” in rather intense radiation fields of tens of mrem/sec. The TEDE for the job ended up being 926 person-mrem and the approval by the site radiation safety officer (SRSO), required by the Fermi Radiation Control Manual, to exceed 1000 person-mrem was applied for and granted during the job-planning phase.
The third problem was a stuck target drive, which could not be fixed. The target and the carrier assembly were replaced. The old target is cooling off in a shielded pit (morgue). This and probably the horn problem were caused by the very high radiation and the extremely corrosive atmosphere in the target chase (e.g., water condensed from air has a pH of 2.6!).
The Tevatron accelerator complex has run with few interruptions during the last three months, producing a series of records. The collider broke its own world luminosity record several times. The collider store 4949 pushed the peak luminosity of the Tevatron to 228.1E30/cm2/s. The integrated luminosity has also done well. The current record for weekly integrated luminosity was established during the week of August 28, when the Accelerator Division produced 33.3 picobarns-1, almost 60 percent more than the record in place a year ago.