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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
0.105 0.210 0.00477 0.313 1
“Large”
X-Emittance3.15 6.29 0.00477 0.313 900 in x
“Large”
Y-Emittance0.105 0.210 0.477 31.3 10000 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]
IPIP
5
lost particles corresponding to red peak on previous plot
IP
6
Large Y-Emittance: Phase Space Plot
-2095 m
-1101 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.
IPZ [m]
y’/
y;
y/y
IP
7
Compare Loss Points with LER Beta Functions
[m]
Z [m]
IP
8
-3.6 m
-2118 m
-2095 m
-2042 m
-1900 m
-1600 m-1325 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
IP
9
Q2
QFS3L before QD34
QD__ near
SCY3
QF__ before SCX3
QF__QF3R01QF4R01QFPR12
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
IP
10
-1125 m
-1101 m
-1075 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 AperturesCollimator
Distance from IP
Current Setting
8 10 12
Primary Y
3014-365 m y ≥ -10.5 mm y ≥ -6.8 mm y ≥ -8.5 mm y ≥ -10.2 mm
Primary X
2082-345 m x ≤ 11.8 mm x ≤ 8.9 mm x ≤ 11.1 mm x ≤ 13.3 mm
Secondary X
2042-320 m x ≤ 8.4 mm x ≤ 6.5 mm x ≤ 8.1 mm x ≤ 9.7 mm
Secondary Y
2032-313 m y ≤ 6.3 mm y ≤ 5.5 mm y ≤ 6.9 mm y ≤ 8.3 mm
Movable Jaw
3076-25 m
x ≥ -19.5 mmx ≤ 22.0 mm
|x| ≤ 18.9 mm
Movable Jaw
3043-12 m
x ≥ -27.5 mmx ≤ 26.0 mm
|x| ≤ 17.4 mm
*** Note: These are TURTLE sign conventions(+x = toward inside of ring for LER)
PR
04P
R02
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]
X [mm]
X [mm]
X [mm]minimal aperture
10 sigma setting
particles that hit within
±25 m of IP
Clo
sing
PR
O4
Col
limat
ors
current setting
16
+25.2 m from IP
LER
-25.2 m from IP
X [mm]
X [mm]
x x [m] x [2]
+25 m -13.6 54.2 0.0
-25 m +13.6 54.2 37.11
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]
X [mm]
X [mm]
X [mm]minimal aperture
10 sigma setting
Clo
sing
PR
O4
Col
limat
ors
current setting
18
+12.5 m from IP
-12.5 m from IP
X [mm]
X [mm]
x x [m] x [2]
+12 m -11.9 46.1 0
-12 m 11.9 46.1 38.11
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]
X [mm]
X [mm]
X [mm]minimal aperture
10 sigma setting
21
X Distribution at Proposed Collimator Location, +25 m from IP
X [mm]
X [mm]
X [mm]
X [mm]minimal aperture
10 sigma setting
22
Consistency Check – Compare w/ Durin (0 m = IP)
Z [m]
Z [m]
Z [m]
Z [m] Z [m]
Z [m]
Z [m]
Z [m]
Coulomb Scattering
Coulomb Scattering
Coulomb Scattering
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 mPlots include all
particles produced
X’ [mrad] Y’ [mm] Y’ [mrad]
25
First-Order MAD Calculation
m25m 25m 25
m25m 25m 25
m25m 25m 25
m25m 25m 25
1211
12
11
2221
1211
'8.418.9
'2.528.12
'1.239.4
'9.406.9
'
sin
sincos
''
turns)(after two
turns)(after two
turn)one(after
turn)one(after
xxx
xxx
xxx
xxx
xRxRx
R
R
x
x
RR
RR
x
x
aab
ba
aa
b
ab
x x [m] x [2]
+25 m -13.6 54.2 0.0
-25 m(+1 turn)
+13.6 54.2 37.11
+25 m(+1 turn)
-13.6 54.2 38.57
-25 m (+2 turns)
+13.6 54.2 75.71
+25 m(+2 turns)
-13.6 54.2 77.14
26
TURTLE/Calculation Comparison
m25m 25m 25 '9.406.9 xxx
m25m 25m 25 '1.239.4 turn)one(after xxx
X [mm]X [mm]
X [mm] X [mm]
Plots include all particles produced
X [mm] X’ [mrad]
Calculation starting
point
27
Direct Comparison
TURTLE X[mm] TURTLE X[mm]
Plots include all particles produced
28
Correlation Check
X’ [mrad] at +25 m Y’ [mrad] at +25 m
Plots include all particles produced