Presentation on theme: "Note: most of the slides shown here are picked from CERN accelerator workshops. Please refer to those workshop for further understanding of the accelerator."— Presentation transcript:
Note: most of the slides shown here are picked from CERN accelerator workshops. Please refer to those workshop for further understanding of the accelerator physics.
The result, reported at the January 1931 APS meeting, earned Livingston his Ph.D. and Lawrence $500 from the National Research Council towards the construction of a machine that might be useful for nuclear physics."
RHIC consists of two 3.8 km long rings, called Blue (clockwise) and Yellow (counter clockwise) It has six interaction regions (IR), four of which are equipped with detectors: PHENIX and some other less important experiments There are 3(4) pre-injectors and transfer lines involved when filling RHIC. A briefing on RHIC
Some Basics: Bunched Beam total of 55 bunches per ring 12.8 s per revolution Abort gap Beam is accelerated by Radio Frequency (RF) cavities: 28 MHz for acceleration 200 MHz for storage to reduce bunch length 28 MHz defines the number of “ buckets ” = 360, length is 12.8 s/360=35 ns (or 10 m) Coasting beam: continuous, no bunch structure (debunched), cannot be accelerated Bunched (or captured) beam: every 6 th (3 rd ) bucket, i.e. 55+5 (110+10) bunches per ring with 10 9 Au ions or 10 11 protons Bunch 1 Bunch 55 “cogging”: lock f rev of both beams and rotate bunches such that they collide at IRs
RHIC ramp with 56 bunches Acceleration BLUE Fill 56 bunches YELLOW Fill 55 bunches Transition energy Storage energy Correction points (stepstones) Total Yellow current Bunched Yellow current Total Blue current Bunched blue current The beam is accelerated from Injection Energy (10 GeV) to Storage Energy (100 GeV). The acceleration process is called “ ramp ”. Injection energy
RHIC Run-4 - Low Energy Stores during last week, Monday to Monday 60e9 Au intensity beam experiment 31GeV/u setup 31GeV operation Luminosity 10x lower (relativistic , *)
RHIC Run-4 Some statistics (week 22-Mar to 28-Mar), no maintenance, setup for 31.2GeV/u No of stores: 20 Time in store: 77hrs (46% of calendar time) (53% Run-4 average) Average store time: 3.9hrs Av. store-to-store time: 2.0hrs (ex beam exp. & setup) Rms store-to-store time: 2.0hrs Optimum store length: 3.2hrs (for zero detector turn-on time)
Delivered Integrated Luminosity maximum projection minimum projection physics target Best 7 days: delivered 179 ( b) -1 to Phenix
Below the transition energy, high-energy particles take less time (higher frequency) to navigate the accelerator than low-energy particles. above the transition energy, when the particle speed is very close to the speed of light, it is the increase of R that becomes the dominant effect, df/f < 0, and thus high-energy particles take longer (lower frequency) to move around the accelerator than do low- energy particles. Due to significantly smaller emittance and the phase instability in the synchrotron oscillation, the beam with large enough intensity tends to be very unstable when the transition energy is reached. Near the transition energy, the accelerating voltage is jumped in phase (of the synchrotron oscillation) so that the accelerating particles from the rising slope of the synchrotron oscillation would find themselves on the descending slope. This way, the particles can be further accelerated to energies beyond the transition energy. After that,all particles, regardless of their slight differences in momentum, take exactly the same amount of time to circle the machine. Transition Energy
β* is the β (amplitude-function in the phase oscillation) at the collision point.
Circulate: Betatron Motion Particles perform oscillations around closed orbit. The number of oscillations per revolution is called the “ tune ”. The quadrupole configuration ( “ optic ” ) defines the tune (betatron function). Integer and 1/2, 1/3, 1/4 … tunes would cause magnetic imperfections to be repetitive and resonant => beam loss This example: tune = 11.27 1 oscillation Number of oscillation is defined by the magnet configuration.