# Presentation: 574080

## Overview Run-6 - RHIC 

- Vadim Ptitsyn
- C-AD, BNL

## RHIC Run-6 Timeline

- 1 Feb – Start of the Run-6.  Start of the cooldown to liquid He temperatures.
- 12 Feb - End of cooldown and PS tests
- 5 Mar – Start of the s=200 GeV  Physics Run.
-       Participating experiments: STAR and PHENIX.
**       ****PHENIX**  – radial pol ; **STAR**  – long pol
- 6 Apr – **PHENIX**  – radial pol ;  **STAR** – vertical pol
- 14 April –21 April – unscheduled shutdown (investigation of electric accident)
- 26 Apr – **PHENIX** – longitudal pol; **STAR** – vertical pol
- 10  May – **PHENIX** – longitudal pol; **STAR** – longitudinal pol
- 5 Jun  – End of s=200 GeV run
- 5 Jun-6 Jun, s=22 GeV development
- 6 Jun – Start of s=62 GeV Run.
-       Participating experiments: STAR, PHENIX and BRAHMS
-       **PHENIX** – longitudal pol; **STAR** and BRAHMS– vertical pol
- 20 Jun - End of** **s=62 GeV Run.
- 20 Jun – 26 Jun.  s=500 GeV development
- 26 Jun - 30 Jun warm-up to liquid Nitrogen temperatures.
- 30 Jun - End of Run-6. (21.2 weeks of cryo operation)

## Run-6 sub runs

| Beam energy  | 100 GeV  | 11 GeV  | 31.2 GeV  | 250 GeV  |
| --- | --- | --- | --- | --- |
| Purpose  | Physics operation  | Machine
 test  | Physics operation  | Machine
 test  |
| Time  | 12 weeks  | 1 day  | 2 weeks  | 1 week  |
| Participating
experiments  | PHENIX, STAR  |  | PHENIX, STAR, BRAHMS  |  |

## 2005 Shutdown: Major Upgrades

- RHIC ring vertical realignment
- Additional NEG coating in warm regions, bringing total to 430m covered in the warm sections..
- Lattice for lower injection energy ( G ) to provide better polarization matching for AGS-to-RHIC transfer
- Multiple tools for the emittance measurement ( polarimeter target, improved IPM, ATR line flags, jet luminescence monitor)
- BPM electronics upgrade
- New RampEditor.
- STAR detector shielding in the tunnel
- Injection kicker upgrade to provide shorter rise time.
- IR4 and IR8 cryostat measurements to understand the source of 24h orbit variations.

## Physics run lattices  

|  | IP6 | IP8 | IP10 | IP12 | IP2 | IP4 |
| --- | --- | --- | --- | --- | --- | --- |
| Injection | 10 | 10 | 10 | 10 | 10 | 10 |
| Store, 100 GeV | 1 | 1 | 10 | 10 | 10 | 10 |
| Store, 31.2 GeV | 3 | 3 | 10 | 10 | 3 | 10 |

- Lattice modifications:
- - minimized excursion of dispersion function in IR6 and IR8 in the store at 100GeV
- - decreased gamma_t lattice at the injection
- Working points:  (0.72-0.73) box at the injection;   (0.68-0.695) box at the store
- Tune swing done:  100GeV: at the very end of the acceleration, but before final
-                                               beta-squeeze part of the ramp
- 	               31.2GeV: right before the last stone of the ramp

- Beta* configuration (in meters):

## Machine setup

- Achieved in record 3 week time between end of the cooldown and the start of the Physics run.
- Even this period can be improved, taking account considerable machine downtime during the setup stage.
- Blue beam injection development and initial tune/decoupling feedback preparations were done already on the cooldown stage (after Blue ring was ready).
- Application of tune/decoupling feedback for the ramp development, from the very beginning.
-      Beam delivered to the store on the second ramp attempt!

## Polarized protons performance at 100 GeV

| Parameter | Unit | 2002 | 2003 | 2004 | 2005 | 2006 |
| --- | --- | --- | --- | --- | --- | --- |
| No. of bunches | -- | 55 | 55 | 56 | 106 | 111 |
|  bunch intensity | 1011 | 0.7 | 0.7 | 0.7 | 0.9 | 1.3 |
| store energy | GeV | 100 | 100 | 100 | 100  | 100  |
| * | m | 3 | 1 | 1 | 1  | 1  |
| peak luminosity | 1030cm-2s-1 | 2 | 6 | 6 | 10 | 35 |
| average luminosity | 1030cm-2s-1 | 1 | 4 | 4 | 6  | 20  |
| Collision points | -- | 4 | 4 | 4 | 3 | 2 |
| average polarization, store | % | 15 | 35 | 46 | 47  | 60-65% |

## Integrated luminosity; 100 GeV run

## Integrated luminosity by week; 100 GeV run

## Average integrated luminosity per store hour

## Golden store #7909 of 100 GeV run

- Luminosity

## Polarization during 100 GeV run

**Polarization during 100 GeV run**

## 100 GeV run: Luminosities and transverse emittances

- Improved transverse emittance
- control was important item at this run
- During the run the improvements to achieve smaller transverse emittance were done both in the injectors and in the RHIC:
- appropriate choice of working point
- avoiding short bunch length

## Luminosity improvement steps during 100 GeV run

- Improving (reducing)  the emittance from the injectors.
- Increasing number of bunches (54 -> 111)
- Separating Blue and Yellow working points.
- Improving synchro loop, tightening longitudinal phase on the ramp.
- Switching Blue and Yellow working points.
- Increasing bunch intensity (from 1e11 to 1.5-1.6e11 in injected bunches)

## Store working points

**Store working points**

## Integrated luminosity; 31.2 GeV run

## Integrated luminosity by day; 31.2 GeV run

## Golden store (8056) of 31.2 Gev run, with rotators

## Major operation achievements

- Successful application of tune/decoupling feedback for the initial ramp development.
- Fast collimation.
- Regular orbit correction at the beginning of the store (before the cogging) to provide the store reproducibility against 24h orbit variation.
- IR nonlinear corrections: used not only at the store but also on the ramp (after the beta-squeeze).
- 2/3 resonance correction
- Successful demonstration of “quad pumping” technique to provide better AGS-to-RHIC longitudinal emittance matching.  Unfortunately, could not be effectively used because of the transverse emittance deterioration.
- Developed Beam Transfer Function measurement diagnostic.

## Betatron tunes on the ramp with the Feedback on

## Rotator and Snake setup

- Snake setup included:
- Snake scans at the injection (on the machine set up stage)
- Additional inner snake PS current scans to maximize polarization preservation during the Physics run.
- Rotator setup.
- Rotator reconfiguration in several steps with beam in the store, making required orbit and tune correction.
- Propagate the tune and orbit correction to the ramp. (Nevertheless further orbit correction was required in all stones of the rotator ramp.)
- ~8h of beam work
- Continued working point adjustments at the beginning of 2-4 following stores to achieve optimal lifetime.
- Rotator and Snakes control was included into the Ramp Editor.

## Factors limiting machine performance

- Store lifetime:
- Qx=2/3 resonance
- beam-beam effects
- large momentum spread
- Factors affecting transverse emittance:
- small longitudinal emittance and higher beam intensity (enhanced electron cloud effect)
- emittance increase on the ramp (?)
- Deterioration of ramp transmission with the beam intensity
- Beam oscillations with parasitic frequencies 10Hz, 60Hz, ...
-      (coming from cryo and power supply systems)

## Some of the remaining operation issues

- _Reduce machine downtime, increase the time in the store._
- PHENIX vertex reduction.
- Broken “Up” sequence, because of the need for the manual orbit correction.
- The same ‘store’ stone before and after the cogging. So, it should provide the good lifetime with/without collisions at different working points. (There is tune shift both due to beam-beam and the IR bump removal) .
- BPM offsets in some triplets are still large ( >1mm).
- Model: tune/decoupling shifts versus orbit changes

## Further plans

-  Christoph Montag is the Run coordinator for polarized proton part of Run-7.

## Run-7 luminosity improvement factors

- Nonlinear chromaticity correction
- 10Hz IR orbit feedback
- 2/3 resonance compensation
- New working point
- Additional NEG pipes (~100m)

## Conclusions

- Congratulations with the successful run. Most of the goals were achieved.
- Further luminosity improvements (by factor 2) is planned for Run-7.
- It will be important to improve the machine reliability, reduce the downtime, increase the time in the store.