# Presentation: 383290

## Collimation/Background Activities at RHIC

- Loss maps
- BFPP measurement with Cu
- collimator setup and positioning
- other LHC/LARP related activities

- A. Drees                     LARP collaboration meeting, LBL, 04/26/06

## Status of loss maps

- simulations available with teapot and for heavy ions
- sixtrack code modified for RHIC collimators (one-sided, dual plane)
- data available for 5 individual collimators with protons (100 GeV, 31 GeV) and Cu (various energies) and Au (various energies)
- plan to go to CERN to finish fell thru when the RHIC fy06 run was resumed
- we are in the process of hiring two RHIC/LARP postdocs (4 applicants, one is the sixtrack “expert”)

## Simulated Beam Losses

- TEAPOT tracks the particles in lattice, records lost particles
- ACCSIM track particles in scrapers
- ROOT draws the graphs, saves the particle distributions and the graph!

## Heavy Ion Loss Maps 

- Heavy Ion Loss Maps

- Loss maps for Heavy Ions, collab. w. H. Braun (CERN)
- data from Cu run (05), during gap cleaning (5 collimators, primaries and secondaries)

## Measured loss map from 2005 (low energy protons)

- data available with different species, different collimators (V & H) and different energies => still awaits comparison with sixtrack simulations.

## Bound-free Pair Production (BFPP) Measurement at RHIC

**Bound-free Pair Production (BFPP) Measurement at RHIC**

-   Ions after e-capture can cause a “hot-spot” at a location downstream of
-     the IR => potential problem at the LHC
-   collimators can’t clean this kind of beam loss
-   First attempt to measure the cross section at RHIC (A. Drees,
-     W. Fischer, J. Jowett et al.)

- location of loss monitor (140.5 m from IR)

## Loss Monitor data

- data taken during an uncogging experiment

- beginning of store when beams are brough into collision

- losses at point of impact are driven by colliding beams:

## Vernier Scan fits to the loss data

- prelim. result BFPP(140.5 m) = 1 mb (tot. pred. ~ 150 mb)

- BFPP(140.5 m) needs to be multiplied by total area of impact (several meters) to compare with total cross section.

## Collimation Efficiency and Setup

- at RHIC collimators protect experiments from backgrounds (not magnets from quenching)
- => exp. background signals are the quality measure for collimators (easy to tune)
- source of background is beam scraping in the triplets
- collimators are located around IR8 (PHENIX), primaries and secondaries
- Heavy Ions and protons very different
- positioning procedure for p is slow and tedious and not reproducible
- the effectiveness of the individual collimators changes from store to store and between the IRs
- needs systematic analysis (just started)

## STAR and PHENIX Au-Au backgrounds

- Blue Background:  STAR PHENIX

- Yellow Background: STAR PHENIX

- January 11, 2004 Store 4235 – New Collimation System

- heavy ions: background reduction continuous with secondary collimators.
- setup based on feedback from loss monitors and background signals, fully automated

## Beam Position in collimator area

- w/o orbit correction at start

- with orbit correction at start

- orbit at collimators with or w/o orbit correction not reproducible to better than 0.5 mm

- yellow

- blue

## Positioning of collimators using exp. background signals

- yellow

- blue

- yellow

- background signals from exp.

- STAR

- PHENIX

## Collimators at end-of-store ...

- yellow collimators being pulled out
- no effect on PHENIX but big effect on STAR > x10

## ... continued

- blue collimators being pulled out
- effect on both, PHENIX and STAR
- both planes are effective  (step in the background signal)

## Collimator Setup f. protons

- semi-manual
- (preset positions, and manual adjustments)
- collimation positioning time ~ 10 min.
- only 1 plane/collimator is effective (varies from store-store)

## Luminosity Monitor

- fast and rad. hard LHC type luminosity monitor (ionization chamber) is installed in IR10
- collaboration between BNL and LBNL (A. Ratti et al.), approved for APEX time this year
- 1st use “in the field” this year in RHIC, calibration with existing luminosity detectors (ZDCs).
- successful review this week (04/24)
- detector developed gas-leak, back at LBL for repair, ready to be shipped back to BNL next week

- installed inbetween ZDC modules behind DX magnets on one side of IR10

## LHC type electron detectors in IR10 for detailed e-cloud studies

- study e-cloud formation with and w/o dipole field
- much higher sensitivity than the RHIC type detectors
- focus on surviving electrons in gaps and fill pattern optimization
- approved for APEX time during this run in FY06 (polarized protons)
- collaboration BNL (A. Drees, D. Hseuh et al. ) and CERN (M. Jimenez et al.)