# Presentation: 448075

## Machine Goals of the RHIC SPIN program

- Mei Bai
- Collider-Accelerator Department
- Brookhaven National Laboratory

## What has been accomplished so far in the development of the RHIC spin capability .
 What are the machine goals for the RHIC spin program over the next 5-10 years
Where are the technical risks in the development of this spin capability?

-  What are the machine goals for the RHIC spin program over the next 5-10 years
- Where are the technical risks in the development of this spin capability?

**Charges from Peter Barnes**

## Outline

- What has been accomplished so far in the development of the RHIC spin capability
- Polarization capability
- Luminosity capability
-  What are the machine goals for the RHIC spin program over the next 5-10 years
- Important technical issues to improve the RHIC spin capability

## RHIC pp accelerator complex

## Machine configuration for FY2004

- RHIC
- Energy
- Injection: 24.3 GeV/c
- Store: 100.2 GeV/c
- Spin setup
- 2 Full snakes for each ring
- Longitudinal polarization at
-     STAR and Phenix
- Transverse polarization elsewhere
- Polarimetry: IP 12
- CNI polarimeter: pC scattering
- Hydrogen jet: pp scattering

- AGS
- Energy
- Injection: 2.2 GeV/c
- Extraction: 24.3 GeV/c
- Scheme for correcting spin resonance:
- 5% warm helix snake plus the Rf dipole
- Polarimetry
- CNI polarimeter
- E880 polarimeter

## What have been achieved in the AGS

- Successfully commissioned the warm helical partial snake which is provided by RIKEN, Japan. This new snake greatly reduced the polarization loss due to the linear coupling between the horizontal and vertical betatron oscillations.
- Routinely provide 0.7x1011 protons per bunch with 45% - 50% polarization and 1.0x1011 protons per bunch with 40% polarization at AGS extraction energy
- Capable of providing more than 1.0x1011 protons per bunch with 45% at the end of the run

## What has been achieved RHICoutline

- New working point development. The new working points demonstrated they are benign to both beam lifetime and beam polarization
- Absolute polarization was measured at RHIC injection energy as well as store energy with the newly installed H target. Polarization was also measured at the same time with the CNI polarimeter. This allows one to calibrate the pC analyzing power at these two energies.
- Routinely provided stores with average store luminosity 4x1030cm-2s-1, average blue polarization 45% and average yellow polarization 40%.
- High luminosity development with un-polarized proton source yielded 1x1031 cm-2s-1 average store luminosity with 2 collisions at STAR and Phenix.
- Explored the total beam intensity limit due to vacuum pressure. A total of 45 bunches per ring with 1.5-2.0x1011 protons per bunch yielded an vacuum pressure of 3x10-7 Torr at both IP10 and IP12.

## RHIC New Working Point

- good spot for
- polarization as
- well as for beam
- lifetime

- a snake depolarization
- resonance

## A typical ramp

- cross 7th order
- Resonance at 0.717
- around beta* 2m w.o.
- any beam loss

- flattop
- *=2m

- 10 seconds after flattop

- beta1
- *=1m

## A typical store

## Blue Polarization Performance FY04

- With horizontal target

- Qx=0.69, Qy=0.68

- Qx=0.739, Qy=0.738

## Yellow Polarization Performance FY04

- Qx=0.734, Qy=0.735

- Qx=0.68, Qy=0.69

##  Delivered Integrated Luminosity of RHIC PP FY04

** ****Delivered Integrated Luminosity of RHIC PP FY04**

## Projection for FY05 Run

|  | collision energy
[GeV/c] | bunch intensity
[1011] | # of bunch | # of collision points | £store average
[1030 cm-2s-1] | polari-zation at store |
| --- | --- | --- | --- | --- | --- | --- |
| FY05
min | 100 | 0.7 | 56 | 4 | 4.0 | 45% |
| FY05
goal | 100 | 0.7 | 112 | 4 | 8.0 | 50% |
| FY05
alternative | 100 | 1.0 | 56 | 4 | 8.2 | 40% |

## Machine Goals for the Next 4 years

-  Polarization
-  70% or more beam polarization at RHIC injection
-  70% beam polarization at RHIC store energy 250GeV/c
-  Luminosity
-  bunch intensity: 2x1011 protons per bunch
-  112 bunch per ring
-  with a normalized beam emittance of 20 mm-mrad, a luminosity of
-  60x1030 cm-2s-1 is expected at 250 GeV/c
-  150x1030 cm-2s-1 is expected at 100 GeV/c

## Available Techniques to Achieve the Goal

-  Polarization:
-  AGS cold snake is expect to yield 100% polarization transmission from its injection energy to the RHIC extraction energy. The expected absolute polarization is 70%
-  A survey and alignment of the whole machine are expected to reduce the effect of the depolarization resonance strength in RHIC
-  polarization ramp measurement will also allow one to identify the depolarization location quickly
-  Luminosity:
-  The AGS cold snake is also expect to deliver high polarization beam with high bunch intensity
-  by NEG coating all the IR beam pipe, the total beam intensity is also expect to be raised significantly

## Important Technical Issue for Improving RHIC Spin Capability

-  high polarization at 250 GeV
-  needs a major upgrade of the RHIC orbit control system
-  more robust polarization measurement
-  improve lifetime of the polarimeter target
-  improve the polarimeter target control
-  improve the working point control during the ramp
- Improve the on-line model
- tune control using PLL

## Summary

- Things achieved in FY04
- commissioned the new working point which is benign to both the beam lifetime as well as the beam polarization
- demonstrated providing stores with an average luminosity of 4x1030cm-2s-2 and beam polarization of 45% in blue ring and 40% in yellow ring.
- Measured absolute polarization with H Jet target at RHIC injection and store energy
-  Machine goals for the next 4 years
-  provide collisions of 112 bunches per ring with 2x1011 protons per bunch and beam polarization of 70%.
- Approaches for achieving the goal
- AGS cold snake
- NEG coating the beam pipes in all the IPs to eliminate the electron multipacing induced vacuum pressure rise

## Optimized snake current

## High Luminosity Development

-  collisions at STAR and Phenix
-  the difference between beam lifetime and the luminosity lifetime indicates the transverse size growth due to the beam-beam force.

## Achieved Beam-beam Limit 

- Note:
-  total beam intensity is limited by the vacuum pressure rise
-  high luminosity development was done with un-polarized proton source and brighter beam from AGS

|  | # of collisions | Luminosity
[x1030cm-2s-1] | bunch intensity at store[x1011] | Total beam-beam parameter |
| --- | --- | --- | --- | --- |
| RHIC FY04 | 4 | 5.0 | 1.7 | 0.016 |
| RHIC FY04 | 2 | 10 | 1.7 | 0.005 |
| RHIC FY03 | 4 | 5.0 | 0.7 | 0.01 |

## Machine Goals for the Next 5-10 years

|  | bunch intensity
[1011] | # of bunches | *
[m] | £store average
[cm-2s-1] | Time in store
 | Polazation at store |
| --- | --- | --- | --- | --- | --- | --- |
| FY05 | 1.0 | 56 | 1
 | 1.0x1031
 | 45% | 50% |
| FY06 | 2.0 | 56 | 1 | 3.2x1031
 | 55% | 65% |
| FY07 | 2.0 | 90 | 1 | 5.7x1031 | 60% | 70% |
| FY08 | 2.0 | 112 | 1 | 7.2x1031 | 60% | 70% |

## Store statistics

-  RHIC FY04 is using the last week as the data sample
-  during the last week of RHIC FY04, there were on the average 6-8 hours machine development on the daily bases.
-  Assuming:
-  average store luminosity: 4x1030 cm-2s-1
-  time in store: 45%
-  1.1pb-1 per week

|  | Total time[hr] | Time in store
[hr] | Average store to store time[hr] | Minimum store to store time[hr] |
| --- | --- | --- | --- | --- |
| RHIC FY03 | 557 | 227 | 5.7 | 1.1 |
| RHIC FY04 | 144 | 52.8 | 10.0 | 0.8 |