1 Beam-Beam Collimation Study Stephanie Majewski, Witold Kozanecki June 4, 2004 Acknowledgments: Ted Fieguth, Roger Barlow

2 Strategy NOT a beam-beam simulation Use TURTLE (Trace Unlimited Rays Through Lumped Elements) Generate a large-emittance beam (first in x, then in y) that fills the phase space at the IP –This is the naïve equivalent of a multi-turn calculation Simulate tightening existing collimator apertures Explore moving existing PR02 collimators downstream of the IP

3 Input Parameters x [mm]x’ [mrad]y [mm]y’ [mrad]  /nominal Nominal Beam “Large” X-Emittance in x “Large” Y-Emittance in y  x (nominal) = 22 nm-rad  y (nominal) = 1.49 nm-rad

4 Large X-Emittance: Phase Space Plot Z location where particles are lost. Colors correspond to upper plot. Starting x, x’ coordinates of particles lost along the beamline. x/  x x’/  x; Z [m] IP

5 lost particles corresponding to red peak on previous plot IP

6 Large Y-Emittance: Phase Space Plot m m -135 m No particles hit near IP Z location where particles are lost. Colors correspond to upper plot. Starting y, y’ coordinates of particles lost along the beamline. IP Z [m] y’/  y; y/  y IP

7 Compare Loss Points with LER Beta Functions  [m] Z [m] IP

m m m m m m m  colors of arrows/text correspond to lost particle locations plotted on slides 4 &5  numbers are TURTLE coordinates solid arrows  x dashed arrows  y  [m] Z [m] IP

9 Q2 QFS3L before QD34 QD__ near SCY3 QF__ before SCX3 QF__ QF3R01 QF4R01 QFPR12 QF__ solid arrows  x dashed arrows  y  colors of arrows/text correspond to lost particle locations plotted on slides 4 &5  labels are MAD/TURTLE elements  [m] Z [m] IP

m m m  colors of arrows/text correspond to lost particle locations plotted on slides 4 &5  numbers are TURTLE coordinates solid arrows  x dashed arrows  y  [m] Z [m]

11 QFI_ near DIDF, DM1BFF QDI_ near DSEP QFI_ near DM1BFF, DM1AFF solid arrows  x dashed arrows  y  colors of arrows/text correspond to lost particle locations plotted on slides 4 &5  labels are MAD/TURTLE elements  [m] Z [m]

12 Collimator Locations HER LER PEP-II Regions Map

13 Collimator Locations LER

14 LER Collimator Apertures Collimator Distance from IP Current Setting 8  10  12  Primary Y my ≥ mmy ≥ -6.8 mmy ≥ -8.5 mmy ≥ mm Primary X mx ≤ 11.8 mmx ≤ 8.9 mmx ≤ 11.1 mmx ≤ 13.3 mm Secondary X mx ≤ 8.4 mmx ≤ 6.5 mmx ≤ 8.1 mmx ≤ 9.7 mm Secondary Y my ≤ 6.3 mmy ≤ 5.5 mmy ≤ 6.9 mmy ≤ 8.3 mm Movable Jaw m x ≥ mm x ≤ 22.0 mm |x| ≤ 18.9 mm Movable Jaw m x ≥ mm x ≤ 26.0 mm |x| ≤ 17.4 mm *** Note: These are TURTLE sign conventions (+x = toward inside of ring for LER) PR04 PR02  based on fully-coupled vertical emittance, wiggler on:  x = 48 nm-rad,  y = 24 nm-rad

15 X Distribution at Movable Jaw X Collimator, -25 m from IP X [mm] minimal aperture 10 sigma setting particles that hit within ±25 m of IP Closing PRO4 Collimators current setting

m from IP LER m from IP X [mm] xx  x [m]  x [2  ] +25 m m Results are based on an older LER deck (’98) with a tune of 0.57 (in x).

17 X Distribution at Movable Jaw X Collimator, -12 m from IP X [mm] minimal aperture 10 sigma setting Closing PRO4 Collimators current setting

m from IP m from IP X [mm] xx  x [m]  x [2  ] +12 m m Results are based on an older LER deck (’98) with a tune of 0.57 (in x). LER

19 Summary Selected plots will be redone with new LER deck & current tune of 0.51 (in x) +25 m collimator can’t replace PR04 Recommendation: –Move -12 m collimator to +25 m –Keep -25 m collimator in current location Step 1: Leaving the -25 m collimator allows flexibility in collimation and complements PR04 Step 2: If successful, consider removing -25 m collimator in future to reduce HOM heating

20 X Distribution at Proposed Collimator Location, +12 m from IP X [mm] minimal aperture 10 sigma setting

21 X Distribution at Proposed Collimator Location, +25 m from IP X [mm] minimal aperture 10 sigma setting

22 Consistency Check – Compare w/ Durin (0 m = IP) Z [m] Coulomb Scattering 12 & 25 m collimators closed

23 Multi-Turn Extrapolation TURTLE only simulates one turn Caveat: Following results use a LER deck with a tune of 0.57 Do these results make sense for a storage ring?

24 Starting Point: +25 m Plots include all particles produced X’ [mrad]Y’ [mm]Y’ [mrad]

25 First-Order MAD Calculation xx  x [m]  x [2  ] +25 m m (+1 turn) m (+1 turn) m (+2 turns) m (+2 turns)

26 TURTLE/Calculation Comparison X [mm] Plots include all particles produced X [mm] X’ [mrad] Calculation starting point

27 Direct Comparison TURTLE X[mm] Plots include all particles produced

28 Correlation Check X’ [mrad] at +25 mY’ [mrad] at +25 m Plots include all particles produced