1 / 10

RHIC √s=500GeV Run: Remaining Issues and Luminosity Status

This article discusses the remaining issues of the RHIC √s=500GeV run, including luminosity and polarization. It provides an overview of the achieved peak luminosity, reproducibility, and polarization variations. The article also covers polarization loss and plans for high precision polarization ramp measurements. Luminosity issues related to PHENIX background, shielding, and beam losses are also discussed, along with a proposed luminosity plan.

bettyjimenez
Download Presentation

RHIC √s=500GeV Run: Remaining Issues and Luminosity Status

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Remaining Issues of RHIC √s=500 GeV Run

  2. Status • Luminosity • Peak luminosity achieved: 122x10^30 cm^-2 s^-1 • 109 bunches with 1.2x10^11 bunch intensity • Reproducibility: • ~1.5 hour turn-around time if no hardware failures • Average: 4.5 hours • Orbit varies from store to store due to daily variation. Can cause failed ramps due to orbit correction • Polarization: • Jet data suggests polarization at 250 GeV is significantly lower than 60% in both rings. It also shows Blue polarization seems to be below Yellow • Variation from store to store • Seems to be associated with day to day orbit variation • No significant polarization lifetime issue with current rotator settings: ~10-15% transverse component in Blue at IP8 and similar amount in Blue and Yellow at IP6

  3. Polarization ramp measurement: pp93

  4. Tune scan of pp93

  5. Polarization issues • Polarization loss from 100GeV to 250GeV • Where? • All data so far show polarization losses are beyond 100 GeV • Tune scan data so far show surprising wide depolarizing resonance around 0.7 • Spin tune shift as function of beam energy • Theory: • snake contribution remains constant beyond 100 GeV • Contribution from orbital angle between two snakes linearly grows with energy • Needs to be verified experimentally • Polarization lifetime with PHENIX Blue rotator setting which yields close to zero transverse component

  6. Polarization plans • Polarization loss from 100GeV to 250GeV • High precision polarization ramp measurement: ~ 10 hours • 4~5 polarization ramp measurements to minimize statistics • 2 groups of 56x56 with 1.2x10^11 bunch intensity • In 60 bunch pattern to address polarization issue • In 120 bunch pattern to see whether there are differences between the study mode and operating mode • Scan snake orbital angle above 100 GeV: 14 hours • Measure polarization transmission efficiency • 56x56 ramp and profile by sweep before and after pp93 • Scan at step size of 0.1mrad for both Blue and Yellow • At store, measure spin tune using 0.7 resonance • Multiple ramps for each data point may be needed • For optimized snake H angle settin: polarization ramp measurement to confirm the polarization transmission efficiency

  7. Polarization plans • Fine tune scan of polarization transmission efficiency between Qy 0.68 and 0.7: ~ 4 hours • Similar mode as in previous study • Polarization transmission efficiency as function of vertical orbit distortion: ~ 4hours • Similar mode as in previous study • Vary orbit distortion using a single corrector in IR4 above 100GeV

  8. Luminosity issues • PHENIX background issues • inside shielding: collision related • Outside shielding: proportional to beam decay • Not limit bunch intensity at the moment • Beam loss at the end of pp93 due to ps switch from one ramp ps to store ps supply • Sensitive to local orbit at IR5 which varies due to 24 hour orbit variation • Reduced separation bumps • Could limit bunch intensity • Beam dump caused beam-induced magnet quench • Longer abort gap • Could be limit of bunch intensity

  9. Luminosity plan • Increase bunch intensity from store to store • Won’t go too far before the run ends • Try a ramp with 1.8x10^11 bunch intensity with 56x56 • Increase # of bunches • Pros: increase of lumi by 12% compare with current mode • Cons: may lose ramp due to high bunch intensity

  10. Polarization ramp measurement: pp93

More Related