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.

http://microcosm.web.cern.ch/Microcosm/RF_cavity/ex.html

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."

http://www.youtube.com/watch?v=qQNpucos9wc

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

SvOutPlaceObject

Some Basics: Bunched Beam total of 55 bunches per ring

12.8 ms 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 ms/360=35 ns (or 10 m)

Coasting beam: continuous, no bunch structure (debunched), cannot be accelerated

Bunched (or captured) beam: every 6th (3rd) bucket, i.e. 55+5 (110+10) bunches per ring with 109 Au ions or 1011 protons

Bunch 1

Bunch 55

“cogging”: lock frev of both beams and rotate bunches such that they collide at IRs

RHIC ramp with 56 bunches

Acceleration

BLUEFill 56bunches

YELLOWFill 55bunches Transition energy

Storage energy

Correction points (stepstones)

Total Yellow currentBunched Yellow current

Total Blue currentBunched 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 Monday60e9 Au

intensityb

eam

exp

erim

ent

31G

eV/u

set

up

¬ 31GeV operation ®

Luminosity 10x lower(relativistic g, b*)

RHIC Run-4

Some statistics (week 22-Mar to 28-Mar), no maintenance, setup for 31.2GeV/u

No of stores : 20Time 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

maximumprojection

minimumprojection

physics target

Best 7 days: delivered 179 (mb)-1 to Phenix

• N1, N2: number of beam particles per bunch. • B: number of bunches per ring • f. Revolution frequency

A Large Ion Collider Experiment at the LHC: 30 times higher collision energy

ALICE @ PT2

Tunnel radius 27 kilometres (17 mi)

A Large Electron-Positron Collider

• 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.