# Presentation: 860203

## RHIC Machine Performance in Runs 6 and 7

-  Summary of Run 6
-  Expectations and goals for Run 7
-  Run-7 in a nutshell
-  Compare Run 6 and Run 7
-  Conclusions

## Polarized protons performance at 100 GeV (last three runs)

| Parameter | Unit | 2004 | 2005 | 2006 |
| --- | --- | --- | --- | --- |
| No. of bunches | -- | 56 | 106 | 111 |
|  bunch intensity | 1011 | 0.7 | 0.9 | 1.35 |
| * | m | 1 | 1  | 1  |
| emittance | mm mrad | 18 | 28 | 18 |
| peak luminosity | 1030cm-2s-1 | 6 | 10 | 35 |
| average luminosity | 1030cm-2s-1 | 4 | 6  | 20  |
| collision points | -- | 4 | 3 | 2 |
| time in store | % | 41 | 56 | 46 |
| average polarization, store | % | 46 | 47  | 65% |

- Luminosity gain in run-6:
-   2.2   X  1.5  = 3.3

- Increased bunch intensity

- Improved emittance
-  control

- AGS cold snake:
- polarization

- Reduced number of
- collision points

- Courtesy V. Ptitsyn

## Integrated luminosity: 100 GeV run

- Courtesy V. Ptitsyn

## Polarization during 100 GeV run

- Courtesy V. Ptitsyn

## Expectations and Goals for Run-7

- Do better than Run-4 ;)
- Increase number of bunches to 111
- Reach 60% time at store on average
- Reach avg. luminosity/store
- > 8 1026 cm-2 s-1 routinely
- Reach peak luminosity/store
- > 30 1026 cm-1 s-1
- Increase bunch intensity

- yes
- yes
- No!
- yes
- yes
- 	no

## Achieved beam parameters for Run7

- Avg. Luminosity gain: x2-3
- Int. Luminosity gain: x2
- Peak Luminosity gain: x2-2.5
- Reached maximum
- Number of bunches
- Transition crossing/bunch intensity
- Luminosity lifetime? -> cooling
- Transv. emittance preservation?
- We reached the enhanced design goal!

## Scrubbing at the beginning of the run

- Pressure bump moves from IR4 to IR12
- Pressure bump reduces after 4th high intensity injection
- Spend a total of 2 hours

## Example of a good week (May 14-May 20)

- Peak luminosity of 30 1026 cm-2 s-1

- Avg. store luminosity
- of 8 1026 cm-2 s-1

- This weeks integrated luminosity totaled 380 b-1
- Stochastic cooling effect clearly visible
- Initial beam intensity routinely above 120 109

## Example of a bad week May 28 – Jun 3

- Tue-Wed

- Thu-Fri

- Sun-Mon

- Sat-Sun

## AGS merge

- 8897

- 8900

- B QLI:
- bo6-qd3

- cavity damaged
- by water leak

- 8890

- 8892

- Blue QLI
- de-bunching
- cfe-4a-rfb2
- reset

- B QLI:
- b06-qd3

- cfe-4b-rtd1
- repair

- B abort
- pre-fire
- during
- ramp
- down

## 1) blue q-main

- ground fault

- 2) high-pot new
- supplies; bo2-qd1
- replaced

- 3) B and Y QLI;
- blue d-main
- oscillation; yi3-qd2

- 4) BA2 RF
- station trip

- 5) Yellow low
- level RF

- 6) Y and B
- QLIs again;
- Replace
- yi3-qd2

- 7) Breaker
- panel in 914
- blows off

- 8) bi5-qf9
- housekeeping
- supply dead

- 9) bo11-sxf2
- problem

- 10) upstream
- switch in 914
- replaced

- 11) Recovery
- from 914
- power outage

- Physics
-   8739

## Total Bunch Number 111->103

- standard

- _Fancy Gap_:
- More crossings

- beam losses along the bunch train
- Rebucketing issues, debunching beam
- Higher bunch intensity?

## Losses along the bunch train

- 103 std. ramp (1.15) shows beam blow up in all late bunches (ramp failed)
- Next 103 fg ramp with same bunch intensity (1.17) worked
- Gap pattern clearly visible in 8837
- 103 fg set to be default

- 1o3
- Std.

- 103
- f.g.

## Stochastic Cooling (Yellow only)	

- Stochastic cooling was commissioned and made operational for the 2nd half of the run
- Yellow beam decay reduced to “burn-off” rate
- More beam in the center bucket
- Increased luminosity lifetime
- Net-effect on integrated luminosity 10%-20% (analysis not yet finished)

## Bunch Intensity at Injection

- -> 103 bunches

- -> exp.magnet field swap

## Ramp Efficiency

- -> 103 bunches:
- B: 95
- Y: 91

- -> exp.magnet field swap

- 111 bunches <-
- B: 92
- Y: 90

## Time between newfill and accramp (turn-around indicator)

- -> store2store procedure implemented
- Before: 60 min.
- After: 36 min.

## Run7 average luminosityhighest with 103 bunches/ring

- -> 103 bunches

- -> field orientation changed

## Low Energy study:Challenges and Successes

- Challenges
- h=366 invalid events stopped PHENIX, nearly stopped STAR, interfered with V125 abort trigger module
- 3-bucket cogging in h=366 prevented simultaneous expt cogging
- Unipolar defocusing sextupoles limited chromaticity to near zero
- Minor online model issues prevented full range of tune adjustment
- All challenges are addressible either offline or during test run setup
- Successes
- LLRF worked like a charm, RF capture quick with phase detectors
- Instrumentation worked remarkably well with h=366 timing
- Orbit correction, coupling corrections worked well
- Longitudinal beam distribution shorter than expected (scraping?)
- Vernier scans still feasible even with 2-20 minute beam lifetimes
- Have data for luminosity measurement deliverable

- Courtesy T. Satogata

- Setup within 24 hours!

## Low Energy: STAR Vernier Scans

- Courtesy T. Satogata

## Compare Activities in Run-6 and -7

- Run6 includes setup time, Run7 is only physics
- Run6:
- Machine development reappears for 31 GeV, 250 GeV
- Failure hours increase at the end
- Failure hours peak with full field
- Run7
- Less development at the end
- Bi-weekly structure in failure hours?
- Low field -> more reliable

## Failures in hours for Run-6 and Run-7

- Run-6 had 15 weeks, also late spring but at reduced magnetic field (p@100 GeV, 31 GeV)
- Top 3: PS, controls, access controls
- Run-7 had 12 weeks, late spring, full magnetic field/current (Au@100 GeV)
- Top 3: PS, cryo, RHIC RF
- Increase factors (Run6->Run7):
- PS: 2.2
- RF: 2.5
- Cryo: 4.5

## Week-by-week integrated luminosity Run 7

- Only 2 weeks above goal
- Contributing factors:
- Temperature (late start of run), weather
- Full field (Au @ 100 GeV)
- Unprecedented intensity (beam loading)
- Pushing the envelope (transition crossing, pressure rise, number of bunches etc.)
- Aging?

- goal

- avg.

## Time at store

- Data included until Jun 9th 2007
- Goal: 60%
- Failed to reach goal by 15%
- Break up into week-by-week on next slide
- Beam induced quenches not correlated with uptime

- Beam induced quenches:
- 46       69    54     37    18  41

## Integrated Au-Au Luminosity Run-7

- Integrated luminosity well between min. and max. expectation
- Corrected for acc. collisions (due to high coll. rate)
- “bi-weekly” performance oscillation coinciding with maintenance days
- Slope change after experimental magnets polarity flip
- Integrated luminosity still in upper half even with only 40% time at store!

## Conclusions

- Analysis of data not yet finished (Run still going on!)
- We met our goals (almost)
- 111 bunches
- Exceeded 8 1026 cm-2 s-1 avg. luminosity/store
- 30 1026 cm-1 s-1 peak luminosity
- Some weeks exceeded 300 ub-1 integrated luminosity
- Bunch intensity limit (~1.2 109)
- Up-time or reliability needs significant changes:
- Plans for next year
- Long-term plans
- Stochastic Cooling concept worked very well
- Need to work on mechanical design