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?

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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

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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