CollimationBackground Activities at RHIC

1
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
2
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)

3
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!

4
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)

5
Measured loss map from 2005 (low energy protons)
data available with different species, different
collimators (V H) and different energies gt
still awaits comparison with sixtrack simulations.
6
Bound-free Pair Production (BFPP) Measurement at
RHIC

• Ions after e-capture can cause a hot-spot at
  a location downstream of
• the IR gt potential problem at the LHC
• collimators cant 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)
7
Loss Monitor data
losses at point of impact are driven by colliding
beams

• beginning of store when beams are brough into
  collision

• data taken during an uncogging experiment

8
Vernier Scan fits to the loss data
prelim. result sBFPP(140.5 m) 1 mb (tot. pred.
150 mb)
sBFPP(140.5 m) needs to be multiplied by total
area of impact (several meters) to compare with
total cross section.
9
Collimation Efficiency and Setup

• at RHIC collimators protect experiments from
  backgrounds (not magnets from quenching)
• gt 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)

10
STAR and PHENIX Au-Au backgrounds
January 11, 2004 Store 4235 New Collimation
System
Blue Background STAR PHENIX
Yellow Background STAR PHENIX
heavy ions background reduction continuous with
secondary collimators. setup based on feedback
from loss monitors and background signals, fully
automated
11
Beam Position in collimator area
with orbit correction at start
w/o orbit correction at start
yellow
blue
orbit at collimators with or w/o orbit correction
not reproducible to better than 0.5 mm
12
Positioning of collimators using exp. background
signals
yellow
yellow
blue
STAR
PHENIX
background signals from exp.
13
Collimators at end-of-store
yellow collimators being pulled out no effect on
PHENIX but big effect on STAR gt x10
14
continued
blue collimators being pulled out effect on
both, PHENIX and STAR both planes are effective
(step in the background signal)
15
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)
16
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

17
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.)