W. KozaneckiPEP-II MAC Review, 9-11 Oct 03 Beam-beam: Experimental Status Introduction: PEP-II...

W. Kozanecki PEP-II MAC Review, 9-11 Oct 03

Beam-beam: Experimental StatusBeam-beam: Experimental Status

Introduction: PEP-II collision parameters & recent performanceIntroduction: PEP-II collision parameters & recent performance

Interplay between eInterplay between e-- - cloud & beam-beam issues - cloud & beam-beam issues

Beam-beam limit studiesBeam-beam limit studies

SummarySummary

W. Kozanecki, CEA-Saclay


IP Parameter Design Peak performance (Jun 03)

C-M energy (GeV) (e+: 3.1 ; e-: 9.0) 10.58 10.58Crossing angle (mrad) 0.0 < 1.0Luminosity (x 1033/cm2/s) 3.00 6.57

Number of bunches 1658 1034LER current (mA, e+) 2146 1550HER current (mA, e-) 750 1175LER/HER current ratio 2.9/1 1.3/1

y*/x* (cm/cm) 1.5 / 50 1.2 / 40+, 1.2 / 28-Emittance (nm-rad) (y/x) 1.5 / 49 1.8 / 30+, 1.8 / 49-IP rms beam size y/x (m) 4.7 / 157 4.6 / 113

LER tunes (x/y) 38.64 / 36.57 38.52 / 36.57HER tunes (x/y) 24.62 / 23.64 24.52 / 23.62Beam-beam parameter (vertical +/-) 0.03 0.082 / 0.040Beam-beam parameter (horizontal +/-) 0.03 0.109 / 0.040

PEP-II Collision ParametersPEP-II Collision ParametersJ. Seeman, Jun 03


Typical recent performance (May-Jun 03)Typical recent performance (May-Jun 03)L

um

inos

ity

(b

-1)

I+ x I- (mA-2)

Sp

ecif

ic lu

min

osit

y (

b-1m

A-2b

-2)

I+ x I- (mA-2)

Near ½ integer Near ½ integer ((++x/yx/y ~ 0.52/0.57) ~ 0.52/0.57)

e- y-size with e+ current

e+ x-size with e- current

Total luminosity: some tune-shift saturation, but potential for more L

Specific luminosity scales (primarily) with e+ current


Interplay between eInterplay between e-- - cloud & beam-beam issues - cloud & beam-beam issues

Bunch-by-bunch luminosity versus position along the whole train. Pattern: ‘by-4’ (8.4 ns

spacing) with 7 additional big gaps, July 2000.

The first bunches of each mini-train have a high luminosity, which drops to 40 % of its initial value at the end of the longest train. The long gaps clear the electron cloud, which slowly builds up again over along the mini-train. Solenoids had been installed in part of the straights only.

Standard luminosity pattern in spring 2003 Pattern: ‘by-3’ (6.3 ns spacing)

Mini-trains of 10 and 11 bunches are alternating. There is an ion gap of about 3%. In this pattern each mini-train has constant luminosity (except for bunches 1+3). Solenoids now cover most of the beam pipe in all straights and arcs.

F.-J. Decker, et. al.,

PAC’01, ‘03


Interplay between eInterplay between e-- - cloud & beam-beam issues: impact - cloud & beam-beam issues: impact

Bunch pattern optimization: maximize IBunch pattern optimization: maximize Ibunchbunch , taking into account , taking into account

total-current budget (RF power, beam-heating problems)

minitrain spacing (larger minigaps => better e- cloud suppression)

minitrain length (shorter minitrains => less e- cloud buildup)

# of minitrains (fewer minitrains => fewer ‘fragile’ bunches)

need for current ramps at start of train (and/or minitrains)

The severity of electron-cloud effects (for a fixed bunch pattern) The severity of electron-cloud effects (for a fixed bunch pattern) has been steadily decreasing over the yearshas been steadily decreasing over the years

Low-field (25-35 G) solenoids now cover most of the accessible beam-pipe sections. This system was upgraded this summer ( up to 3x higher field in the straights + cover remaining short sections)

Vacuum-pipe scrubbing appears to have played a significant role

Some e– cloud effects are no longer apparent single-beam e+ blowup at high I+ no longer observed (but what once I+ ?)

In typical recent running, only 1st (few) bucket(s) in each minitrain affected by electron cloud (if any)


Interplay between eInterplay between e-- - cloud & beam-beam issues: - cloud & beam-beam issues: towards higher luminositiestowards higher luminosities

Impact of eImpact of e-- cloud may be more severe once higher currents force cloud may be more severe once higher currents force the use of a the use of a denser pattern (‘by-2’)denser pattern (‘by-2’)

e- cloud

Pattern: ‘by-2’ (4.2 ns spacing), long trains (Feb 03)

20-25% luminosity loss after the first 5-10 bunches in each train

Pattern: ‘by-2’ (4.2 ns spacing), short trains [2-4-2-4.-..] (Apr 03)

The first buckets of the duplets have the same high L, while the L of the second ones drops about 50% over 320 ns. It remains constant for several hundred ns, then slowly grows to nearly 75% before it starts dropping again.

F.-J. Decker, et. al.,PAC’ 03


Beam-beam limit studiesBeam-beam limit studies

Experimental procedureExperimental procedure Fix one beam current (typically similar to physics conditions)

Vary the current of the other beam from 0 to maximum possible; at each setting, optimize luminosity on tunes

Measure L/bunch, specific luminosity Lsp, individual beam sizes -x,y in-

& out-of-collision

DiagnosticsDiagnostics Fast luminosity monitor (e+e- e+e- )

Horizontal beam sizes: synchrotron-light monitor (SLM)

Vertical beam sizes: SR-light interferometer


Specific luminosity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.00 0.50 1.00 1.50 2.00 2.50LER bunch current (mA/b)

L_s

p (

E30 m

A^

-2 b

^-1

)

I- ~ 625 mA ~ 1.05 mA/b

HER b-b limit @ high e- current: I- =625 mA, I+ = 100-1400 mA, 597 bunches

LSP drops by ~ 25-30%

HER SLM x-width

1.10

1.20

1.30

1.40

1.50

0.00 0.50 1.00 1.50 2.00 2.50LER bunch current (mA/b)

SLM

RM

S w

idth

(m

m)

Colliding I- ~ 625 mA ~ 1.05 mA/b

HER SLM y-width

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0 500 1000 1500LER current (mA)

SLM

RM

S w

idth

(m

m)


W.K., PEP-II Performance

Workshop, Dec 00

e+ horizontal beam size

1.5

2.0

2.5

0 500 1000 1500LER current (mA)

sig

ma_x

(m

m)

Colliding

No electron beam

Collisions: LEB blowup in

both x & y

(N.B.: y blowup instrumental?)

Single-beam: LEB blowup

minimal

• LEB blowup in collision >> single-beam blowup, by an amount that depends on its own current => LSP drops!

• HER:SLM x & y size in collision flat with I+

No indication of b-b induced HER blowup

(in this data set)


Specific luminosity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.2 0.4 0.6 0.8 1 1.2HER bunch current (mA/b)

L_s

p (

E30 m

A^

-2 b

^-1

)

Colliding

I+ ~ 1070 mA ~ 1.8 mA/b

I+ ~ 90 mA

LER b-b limit @ high e+ current: I+ =1070 mA, I- =200-630 mA, 597 bunches

• LER:SLM x & y size in collision >> single-beam, flat with electron current (not “naive” b-b!)

• HER: I- dep. of x, y SLM size in collision, consistent with single-beam behavior (flat)

LSP drops by < 5%


1.50

1.75

2.00

2.25

2.50

2.75

3.00

0 0.2 0.4 0.6 0.8 1 1.2 1.4HER bunch current (mA/b)

SLM

RM

S w

idth

(m

m)

Colliding

I+ ~ 1070 mA ~ 1.8 mA/b

I+ ~ 90 mA

LER SLM x-width

1.50

1.75

2.00

2.25

2.50

2.75

3.00

0 0.2 0.4 0.6 0.8 1 1.2

HER bunch current (mA/b)

SLM

RM

S w

idth

(m

m)

High I+

I+ = 90 mA

LER b-b limit @ low e+ current: I+ = 90 mA, I- = 20-750 mA, 829 bunches


6 Feb 03 data

I- vs. I+

0

100

200

300

400

500

600

700

800

900

0 200 400 600 800 1000 1200 1400 1600LER current (mA)

HER

cu

rren

t (m

A)

Specific luminosity vs. I+

2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

0 200 400 600 800 1000 1200 1400 1600LER current (mA)

Sp

ec.

lum

inosit

y

Horizontal beam size (SLM)

0.0

0.5

1.0

1.5

2.0

2.5

0 200 400 600 800 1000 1200 1400 1600LER current (mA)

sig

ma-x

(m

m)

LER

HER

Vertical beam size (interferometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0 200 400 600 800 1000 1200 1400 1600

LER current (mA)

sig

ma-y

(m

m)

LER

HER

Typical current-dependence of specific luminosity & beam sizes, Jan-Apr 03


Wandering in Wandering in tune spacetune space......

LERLER Apr 03:

x = .64

y = .56

since May 1, 2003: x = .52

y = .57

HERHER Apr 03:

x = .57

y = .64

since May 1, 2003: x = .52

y = .62

The values quoted here are nominal, unshifted tunes


““Before” Before” ½ integer½ integer vs. vs. “after”“after”: LER beam sizes: LER beam sizes

LER y-size (28 Apr)

+7 %

LER x-size (28 Apr)

+11 %

LER current (e+) [mA]


+ 50-60 % wrt x ( single-

beam)

+ 8 %

LER x-size (2 May)

HER current (e+) [mA]

LER y-size (2 May)

+ 12 %

HER current (e+) [mA]


““Before” Before” ½ integer½ integer vs. vs. “after”“after”: HER beam sizes & Luminosity: HER beam sizes & Luminosity

HER y-size (2 May)

+ 39 %

HER y-size (28 Apr)

L/bunch (28 Apr)

L/bunch (2 May)

LER current (e+) [mA] LER current (e+) [mA]

Product of bunch currents [(mA2/b)2] Product of bunch currents [(mA2/b)2]


LSP (2 May 03)

Msrd: - 25 %

Predctd: -25%

Sp

ec. l

um

inos

ity

[1030

cm

-2 s-1

mA

-2/b

]


Original tunes (Original tunes (++x/yx/y ~ 0.64/0.56) ~ 0.64/0.56)

e- size ~ independent of e+ current

e+ size ~ with e+ current (mostly x: proximity to 2/3?)

Near ½ integer Near ½ integer ((++x/yx/y ~ 0.52/0.57) ~ 0.52/0.57)

e- size with e+ current

e+ size with e- current

Specific luminosity

scales (primarily) with e+ current

=> HEB the ‘weaker’ beam (at that time...)

Total luminosity

some tune-shift saturation (prob. HEB), but potential for more luminosity!

Ibunch(e-) x Ibunch(e+) [(mA/b)2]

L /

bu

nch

(10

30 c

m-

2 s-1

b-1) Luminosity/bunch

(2 May 03)


Dynamic-Dynamic- effect? effect?

(skipped these runs)

Measurement of Measurement of luminous-region sizeluminous-region size by BaBar (dimuons & Bhabha’s) by BaBar (dimuons & Bhabha’s)

1/1/LL = sqrt (1/ = sqrt (1/++22 + 1/ + 1/--

22))

Reduction of horizontal spot size from ~ 100 m to ~ 70 m.

No changes observed in longitudinal spot size.

before April 28th after April 28th

x ~ 0.5

M. Baak, Sep 03


Tune spectra Tune spectra in collisionin collision

++xx

++yy

--xx

--yy

Old tunes x ~ 0.5 (June 03)

??


LER y-tune: b-b tune shift!

~ .004 for 0.81 < I- < 1.07 A

HER y-tune: not fully compensated

HER bunch current (e-) [mA/b]


LEB x-size

+ 64 % wrt x ( single-beam)


y-tunes in collision, vs. ey-tunes in collision, vs. e-- bunch current (LEB trickle, 12 Jun 03) bunch current (LEB trickle, 12 Jun 03)


Determination of beam-beam parameters Determination of beam-beam parameters from from luminosityluminosity & spot-size data & spot-size data


““Measured” beam-beam parametersMeasured” beam-beam parameters


Beam-beam performance summaryBeam-beam performance summaryJ. Seeman, Aug 03


Summary (I)Summary (I)

Electron-cloudElectron-cloud effects have been minimized by a combination of effects have been minimized by a combination of scrubbing, solenoid-suppression, and bunch-pattern optimizationscrubbing, solenoid-suppression, and bunch-pattern optimization

LuminosityLuminosity (& (& backgroundbackground!) optimization relies on a delicate !) optimization relies on a delicate balancebalance between the currents, tunes, beam-beam parameters and between the currents, tunes, beam-beam parameters and e-cloud effects as these parameters vary along each bunch train.e-cloud effects as these parameters vary along each bunch train.

Current-dependenceCurrent-dependence of the of the spot sizesspot sizes in collision (@ in collision (@ xx ~ 0.5) ~ 0.5)

LEB (HEB) sizes depend only on e- (e+) current

y(e-) grows by 30-70% wrt the e- single-beam size

30-40% is more typical of recent (stable) running : mostly ‘spontaneous’ ?

x(e+) grows by a factors of 1.5 to > 2 wrt the e+ single-beam size

50-60% is more typical of recent (stable) running: ‘spontaneous’ or effective optimum?

offline analysis of luminous region size (using dimuons & Bhabh’as) corroborates the expected reduction in IP x-spot size ( simulation?)

...but the observed variations of IP spot size are not always consistent with the measured current-dependence of individual e+ and e- beam sizes


Summary (II)Summary (II)

Beam-beam parameter measurementsBeam-beam parameter measurements

some tune measurements in collision are difficult (esp. LER x)

extracting (or limits thereon) from L and (SL+,- x,y promising, but...

it needs better control of SLM/interferometer systematics

it would greatly benefit from the ability to ‘translate’ SL sizes into IP sizes

the interpretation/analysis is complicated by dynamic- effects.

1 measurement of vertical LEB beam-beam tune-shift vs. HER current! but interpretation not straightforward..

can we gain more from such parasitic monitoring?

New diagnostics being commissionedNew diagnostics being commissioned gated cameras in HER & LER

on-line measurements of IP positions & spot sizes by BaBar

gated tune monitor

PEP-II has recently achieved, near the ½ integer, beam-beam PEP-II has recently achieved, near the ½ integer, beam-beam parameters parameters xx/ / yy of about of about .109 / .082.109 / .082 ( (.040 / .040.040 / .040)) in the LER (HER) in the LER (HER)


Spare slidesSpare slides


In contrast to ‘classical’ single-ring collider,In contrast to ‘classical’ single-ring collider,

+x,y -

x,y (and +x,y -

x,y only) => +x,y -

x,y

interpreting luminosity in terms of requires additional knowledge and/or assumptions on individual IP spot sizes

energy-transparency conditions

+x,y = -

x,y <===> I+b E

+ = I-b E

-

(provided +x,y = -

x,y , +

x,y = -x,y ,

+x,y = -

x,y...)

largely violated in PEP-II

best performance repeatedly achieved with I + / I

–~ 1.3 (more typically 1.7 – 2, not 2.9!)


Typical performance since Run 4 startupTypical performance since Run 4 startup

I+ x I- (mA-2)

Lu

min

osit

y (

b-1)

I+ x I- (mA-2)

Sp

ecif

ic lu

min

osit

y (

b-1m

A-2b

-2)


At high I At high I ++, e, e-- cloud strength varies along minitrain => cloud strength varies along minitrain => e+ beam size varies (long range + within train) => Luminosity varies

e- beam-beam tune-shift varies (=> e- beam size may vary ??)

tunes optimized on the average only => slight L loss

‘raining’ buckets (rapid loss of charge, background spikes, flip-flop)

electron-cloud enhanced beam-beam blowup of the e+ beam

Interplay between eInterplay between e-- - cloud & beam-beam issues (2) - cloud & beam-beam issues (2)

Gated-camera measurements

(2001 data, 4-by-22 pattern)

R. Holtzapple, PEP-II Performance Workshop, Jan 2002


Beam-beam flip-flopBeam-beam flip-flop

Near the top of a fill: Several LER bunches have

reduced beam size (~30% reduction in beam size)

Several bunches - typically near the head of the train - have ~ ½ L

2 states2 states of low-luminosity bunches: they have either reduced LER current or reduced LER beam size

IIbb++ = low = low; Ib

- = average

Ib+, Ib

- = average; x, yx, y++ = smal = small.

Small LER bunches + low L implies transverse blow-up of the e- beam, since bunch currents are not particularly low for these.

R. Holtzapple, et. al., SLAC-PUB-9238 (2001 data)


Beam-beam flip-flop (2)Beam-beam flip-flop (2)

Single Bunch Transition to low-luminosity state

Initially at average beam size

Luminosity dropped when rings were filled

The bunch experiences a sudden change in luminosity/beam size

This bunch went from one unstable state (low luminosity / small x, y) to the other unstable state (short lifetime)

Transition between states is fast (~0.5 sec.)

Horizontal beam size oscillation accompanies the transition


Beam-beam flip-flop (c’td)Beam-beam flip-flop (c’td)

Possible Explanation of Beam Size Flip-Flop Dynamics

The LER bunches at the front of the train have a smaller transverse beam size (lower electron cloud density). These small (strong) LER bunches blow-up the HER bunches.

The resulting tune shift for the these LER bunches is smaller than “normal”, and as a result, they have a horizontal tune located near a resonance which gives them a shorter lifetime.

The LER bunches lose charge. Eventually the HER becomes strong enough to flop itself, and the LER bunch, back to “normal” size.

To confirm this theory, a 2nd gated camera has been installed in the HER and is being commissioned.

Start of the store (high I): L/bunch (almost) uniform throughout each train.

End of the store (low I): single-bunch L dropouts are prevalent in the 1st few trains


HER b-b limit (continued)

• LEB blowup in collision >> single-beam blowup, by an amount that depends on its own current => LSP drops!

• LEB blowup with both beams present but out of collision, is similar to single-beam blowup

LER SLM x-width

1.50

1.75

2.00

2.25

2.50

2.75

3.00

0 500 1000 1500LER current (mA)

SLM

RM

S w

idth

(m

m)

Colliding

Separated

No HER

I- ~ 625 mA ~ 1.05 mA/b

LER SLM y-width

0.56

0.60

0.64

0.68

0.72

0.76

0 500 1000 1500LER current (mA)

SLM

RM

S w

idth

(m

m)

Colliding

Separated

No HER

I- ~ 625 mA ~ 1.05 mA/b

HER SLM x-width

1.10

1.20

1.30

1.40

1.50

0 500 1000 1500

LER current (mA)

SLM

RM

S w

idth

(m

m)


HER SLM y-width

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0 500 1000 1500LER current (mA)

SLM

RM

S w

idth

(m

m)


No indication of b-b induced HER blowup

(in this data set)

Collisions: LEB blowup in

both x & y

(N.B.: y blowup instrumental??)

Single-beam or separated: LEB blowup

minimal

By-5 - 1/50th, 597 bunches , *y = 1.25, July 00


Specific luminosity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 0.2 0.4 0.6 0.8 1HER bunch current (mA/bunch)

L_s

p (

E30 m

A^

-2 b

^-1

)

I+ = 90 mA

LER b-b limit @ low e+ current: I+ = 90 mA, I- = 20-750 mA, 829 bunches

Luminosity/bunch

0

0.05

0.1

0.15

0.2

0.25

0 0.02 0.04 0.06 0.08 0.1 0.12

(I+/b) * (I-/b) (mA^2/bunch)

L/b

unch

(E30/b

unch

)

• LER: definite, but moderate, increase in both x,y SLM sizes with electron current (as expected)

• HER: I- dep. of x, y SLM size in collision, consistent with single-beam behavior

LER SLM x-width

1.50

1.75

2.00

2.25

2.50

2.75

3.00

0 0.2 0.4 0.6 0.8 1 1.2


SLM

RM

S w

idth

(m

m)

High I+

I+ = 90 mA

LSP drops by ~ 10-15%

LER SLM y-width

0.56

0.60

0.64

0.68

0.72

0.76


SLM

RM

S w

idth

(m

m)

High I+I+ = 90 mA


Specific luminosity

0.0

0.5

1.0

1.5

2.0

2.5

3.0


L_s

p (

E30 m

A^

-2 b

^-1

)

Colliding

I+ ~ 1070 mA ~ 1.8 mA/b

I+ ~ 90 mA

LER b-b limit @high e+ current: I+ =1070 mA, I- =200-630 mA, 597 bunches

• LER:SLM x & y size in collision >> separated, but both are flat with electron current (not “naive” b-b!)

• HER: I- dep. of x, y SLM size in collision, consistent with single-beam behavior (flat)

LSP drops by < 5%

LER SLM x-width

1.50

1.75

2.00

2.25

2.50

2.75

3.00

0 0.2 0.4 0.6 0.8 1 1.2


SLM

RM

S w

idth

(m

m)

Colliding

Separated

I+ ~ 1070 mA ~ 1.8 mA/b

I+ ~ 90 mA

LER SLM y-width

0.56

0.60

0.64

0.68

0.72

0.76


SLM

RM

S w

idth

(m

m)

Colliding

Separated

I+ ~ 1070 mA ~ 1.8 mA/b

I+ ~ 90 mA


1.50

1.75

2.00

2.25

2.50

2.75

3.00

0 0.2 0.4 0.6 0.8 1 1.2 1.4HER bunch current (mA/b)

SLM

RM

S w

idth

(m

m)

Colliding

I+ ~ 1070 mA ~ 1.8 mA/b

I+ ~ 90 mA


Horizontal beam size (SLM)

0.0

0.5

1.0

1.5

2.0

2.5

100 350 600 850 1100 1350 1600LER current (mA)

sig

ma-x

(m

m)

LER

HER

Vertical beam size (interferometer)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

100 350 600 850 1100 1350 1600

LER current (mA)

sig

ma-y

(m

m)

LER

HER

Vert. size of lum. region (L_sp + CapSy)

3.00

3.25

3.50

3.75

4.00

4.25

4.50

4.75

5.00

100 350 600 850 1100 1350 1600

LER current (mA)

sig

_yL (

L_s

p)

(mic

ron

s)

sig_yL(Lsp)

CapSY/2

Horizontal size of luminous region (BBR+ CapSy)

60

70

80

90

100

110

120

100 350 600 850 1100 1350 1600LER current (mA)

sig

_xL (

mic

ron

s)

sig_xL(B)CapSX/2

6 Feb 03 dataComparison of individual beam sizes with luminous-region measurements


Very little HEB current-dependence of either LER or HER spot sizeVery little HEB current-dependence of either LER or HER spot size

LEB current-dependence : for 1.1 < ILEB current-dependence : for 1.1 < I++ < 1.85 A < 1.85 A,,

LER x-size: + 20%

y- : + 10-15 %

HER x-size: + 6% (but: large spread)

y- : + 10% (but: large spread; may be consistent with ~0)

Lsp : - 30% (measured)

: - 21% (predicted from spot size variations)

Lsp

Lsp =2.9 predicted from HER/LER beam size

relative variation

5 Apr 03 data

LER bunch current (mA/bunch)


Specific luminosity vs. beam currentsSpecific luminosity vs. beam currents

I- (mA)

I+

LSP

I- (mA)

I+ (mA)

LSP

Msrd: - 25 %

Predctd: -25%


LEB size vs beam currentsLEB size vs beam currents

LER x-size

+ 8 %

LER x-size

LER y-size

LER y-size

+ 12 %


““Before” Before” ½ integer½ integer vs. vs. “after”“after”: LER beam sizes: LER beam sizes

LER x-size (28 Apr)

LER y-size (28 Apr)

+ 8 %

LER x-size (2 May)

LER y-size (2 May)

+ 12 %

+11 %

+7 %


LER y-tune: b-b tune shift!

~ .004 for 0.81 < I- < 1.07 ALER y-tune knob

HER y-tune: not fully compensated

HER y-tune knob

HER bunch current (e-) [mA/b] HER bunch current (e-) [mA/b]

HER bunch current (e-) [mA/b] HER bunch current (e-) [mA/b]

y-tunes in collision, vs. ey-tunes in collision, vs. e-- bunch current (LEB trickle, 12 Jun 03) bunch current (LEB trickle, 12 Jun 03)


• No apparent dependence of the horizontal luminous size on LER or HER currents

• No apparent dependence of the longitudinal luminous size on LER current.

Luminous spot sizes Luminous spot sizes vs. beam currentsvs. beam currents

after April 28th x ~ 0.5

M. Baak, Sep 03


Current-dependence of measured SL spot sizesCurrent-dependence of measured SL spot sizesLER X spot size

0

0.5

1

1.5

2

2.5

0.8 0.9 1 1.1 1.2HER bunch current (mA/b)

Sp

ot

size

(m

m)

LER_Sx

sLx_f

LER Y spot size

0.28

0.29

0.3

0.31

0.32

0.33

0.34

0.8 0.9 1 1.1 1.2HER bunch current (mA/b)

Sp

ot

size

(m

m)

LER_Sy

sLy_f

HER X spot size

0.57

0.58

0.59

0.6

0.61

0.62

0.63

0.64

1.1 1.3 1.5 1.7 1.9LER bunch current (mA/b)

Sp

ot

size

(m

m)

HER_Sx

sHx_f

HER Y spot size

0.15

0.2

0.25

0.3

0.35

0.4

1.1 1.3 1.5 1.7 1.9LER bunch current (mA/b)

Sp

ot

size

(m

m)

HER_Sy

sHy_f


Current-dependence of estimated IP spot sizesCurrent-dependence of estimated IP spot sizes


Comparison ofComparison of fitted fitted && measuredmeasured L & LL & LSPSP


ButBut it does not always work so well...it does not always work so well...

Specific luminosity

2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

4.1

4.3

4.5

0 10000 20000 30000 40000 50000

Time (sec)

L_sp

(10^

30 b

^-1

mA

^-2)

L_SP

L_sp_c

Specific luminosity

2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

4.1

4.3

4.5

0 10000 20000 30000 40000 50000

Time (sec)

L_sp

(10^

30 b

^-1

mA

^-2)

L_SP

L_sp_c

HER X spot size

0.58

0.59

0.6

0.61

0.62

0.63

0.64

0.65

0.8 1 1.2 1.4 1.6 1.8 2

LER bunch current (mA/b)

Spo

t siz

e (m

m)

HER_Sx

sHx_f

HER X spot size

0.58

0.59

0.6

0.61

0.62

0.63

0.64

0.65

0.8 1 1.2 1.4 1.6 1.8 2

LER bunch current (mA/b)

Spo

t siz

e (m

m)

HER_Sx

sHx_f

5-6 Jun3 May

W. KozaneckiPEP-II MAC Review, 9-11 Oct 03 Beam-beam: Experimental Status Introduction: PEP-II...

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Transcript of W. KozaneckiPEP-II MAC Review, 9-11 Oct 03 Beam-beam: Experimental Status Introduction: PEP-II...