# Presentation: 681476

## RHIC Machine Status

- Wolfram Fischer
**— ****Run Coordinator for Run-4 Gold-Gold Operation ****—**
**For the C-A RHIC Team**
- RHIC Spin Collaboration Meeting27 February 2004

## Content

- Run-4 Au-Au luminosity development
- Peak luminosities and best performance
- Time in store
- Luminosity limitations
- Luminosity estimates for pp operation
- Summary

## RHIC Run-4                                                                                                                               Physics stores

**design****luminosity**

- Best week (9 Feb to 17 Feb)

**enhanced****luminosity**

**60e9 Au****intensity**

**Beam experiments**

## RHIC Run-4                                                                                                                   Luminosity evolution

- As of 02/22/04 24:00   Star     	0.9   Phobos 	0.3    Brahms 0.4

- Delivered 766 (b)-1 to Phenix [week ago : 480]                 132 (b)-1 last week [best week:  153]

## RHIC Run-4                                                                               Peak luminosity and best week performance

| Mode | No ofbunches | Ions/bunch [9]  | *[m]  | Emittance
[m]  | Lpeak [cm-2s-1]  | Lstore ave[cm-2s-1]  | Lweek[b-1] |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Run-4 achieved | 56 | 0.9 | 1 | 15-40 | 15  1026  | 4  1026  | 153  |
| Run-4 goal* | 56 | 0.9 | 1 | 15-40 | 12  1026  | 3  1026  | 70  |
| Design | 56 | 1.0 | 2 | 15-40 | 9  1026  | 2  1026  | 50  |

- [* Run-4 goal: basis for maximum projection]

## RHIC                                                                                                                                           Time in store

- [last month]

- [last month]

- [last month]

- [last month]

- [1st 8 weeks]

-  new target including:           11h beam exper.
- 10h maintenance

- Comments: - Not all store time used by experiments (initial background, detector turn-on, etc.)
- - Usable store time differs from experiment to experiment

- [Best week withoutmaintenance: 66%]

## RHIC Run-4                                                                                                        Beginning of store activities

- Beam intensity

- Luminosity

- Background

- 2min steering

- 5min collimator setting

- Steering and
- collimatorsetting within
- ~10min
- [up to 1hr in previous Runs]

**Notes:**
Beginning of store 4508

## RHIC Run-4                                                                                            Rebucketing and vertex distribution

- 5ns

- Improved rebucketing
-  fully automatic at end of energy ramp
-  only small amount of beam in adjacent  buckets Almost no further improvement possible(Widening of longitudinal distributions are from intra-beam scattering. This limit can only be overcome by beam cooling at full energy.)

## RHIC Run-4                                                                                                                         Luminosity limits

-  Beam intensities in both rings are limited by vacuum instabilities
-  Machine operates as closely as possible at these limits

- intensities

- pressure in Blue sector 8

- exponential pressure increase after rebucketing(bunch length shortened)

## RHIC Run-4                                                                                                                  PHOBOS background

- PHOBOS background increase after rebucketing, drops after minutes to 2 hours

- intensity

- vacuum

- background

- 4544: drop after 8min

- 4536: drop after 1:43hrs

- rebucketing

-  under investigation

## RHIC Run-4                                             Expected pp luminosity for hypothetical operation (conservative)

- Assume
- Same charge can be stored for p and Au beams(45x45, 1.1e9/bunch – not yet the vacuum limit)
- pp luminosity lifetime of 7h (2h for Au beams)
- 20mm·mrad transverse normalize emittance
- 5h store length, 2h refill (optimum store length 4.7h)
- 50% of calendar time in store
- Luminosity is
- 71030cm-2s-1 peak
- 3.51030cm-2s-1 average per store
- 1.1 pb-1/week

## Summary

- Delivered Au-Au luminosity exceed most optimistic assumptions:delivered 800(b)-1 to PHENIX in 8 weeks(almost the same to STAR, 1/3 to BRAHMS and PHOBOS)
- Calendar time in store increased to 50%
- Smaller vertex distribution, fast steering and collimator setting than in Run-3
- Vacuum limits beam intensity, and severely affects PHOBOS background