Collisions were first recorded on June 15 at one of the four primary intersecting regions (experimental halls). The four major experiments are named STAR, PHENIX, BRAHMS, and PHOBOS. Each of these experiments is studying various properties of the quark-gluon plasma created when ions collide at high energy.
As expected, RHIC operation proved to be much less challenging from a residual radiation standpoint than the main Alternating Gradient Synchrotron (AGS) ring. RHIC is designed to be a near lossless particle accelerator, meaning that it is designed to lose beam only at crossover collision points in the experimental halls. Losses at injection are extremely modest. In fact, we could not find any residual activity with dose-rate meters in several large sections of the collider at all. The most heavily activated portion of the collider are the internal beam dumps, one in each ring, and these were only reading about 1 mrem/hr immediately following machine shutdown in September.
The shift in focus away from the high-energy physics fixed-target program and toward RHIC operation has resulted in falling cumulative exposures for the Collider-Accelerator Department, the new name adopted after the AGS merged with the RHIC project last year. Operation with heavy ions causes much less measurable activation of main ring components. In fact, average residual activity levels have actually fallen during the last two years. Heavy ion operation also results in less stress on key ring components, meaning that less maintenance and upkeep are required. These two factors have resulted in the department's annual cumulative radiation exposure being half of what it was several years ago. This trend is expected to plateau because of the revival of a smaller fixed-target program next year. The schedule has RHIC operations commencing in March and continuing through August 2001.
Concurrently, several high-energy physics experiments are scheduled to run during periods when RHIC is filled with beam. The goal is to fill RHIC twice a day with gold ions (takes only minutes) and to use the accelerator complex to deliver protons to the fixed-target experiments while collisions are occurring at RHIC. This will mark the first time the Collider-Accelerator Department has attempted this dual mode of machine operation.