gun test facility layout longitudinal emittance measurement technique longitudinal emittance

John Schmerge, SLACJohn Schmerge, [email protected]@slac.stanford.edu

Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center

S2E Workshop August 18, 2003

Longitudinal and slice emittance measurements at the SLAC Gun Test Facility

John Schmerge, SSRL/SLAC

August 18, 2003

Longitudinal and slice emittance measurements at the SLAC Gun Test Facility

John Schmerge, SSRL/SLAC

August 18, 2003 Gun Test Facility LayoutGun Test Facility Layout

Longitudinal Emittance measurement techniqueLongitudinal Emittance measurement technique

Longitudinal Emittance Longitudinal Emittance Linear AnalysisLinear Analysis Nonlinear AnalysisNonlinear Analysis

Slice Emittance measurement techniqueSlice Emittance measurement technique

Slice EmittanceSlice Emittance Emittance MeasurementsEmittance Measurements Slice Offset Measurements Slice Offset Measurements

Gun Test Facility LayoutGun Test Facility Layout

Longitudinal Emittance measurement techniqueLongitudinal Emittance measurement technique

Longitudinal Emittance Longitudinal Emittance Linear AnalysisLinear Analysis Nonlinear AnalysisNonlinear Analysis

Slice Emittance measurement techniqueSlice Emittance measurement technique

Slice EmittanceSlice Emittance Emittance MeasurementsEmittance Measurements Slice Offset Measurements Slice Offset Measurements

http://www-ssrl.slac.stanford.edu/




GTF GroupGTF Group

Paul Bolton Laser

John CastroJohn Castro GTF operatorGTF operator

Jym ClendeninJym Clendenin AcceleratorAccelerator

Dave DowellDave Dowell LCLS Injector Group LCLS Injector Group LeaderLeader

Steve GiermanSteve Gierman AcceleratorAccelerator

Cécile Limborg-DépreyCécile Limborg-Déprey SimulationsSimulations

John SchmergeJohn Schmerge GTF Group LeaderGTF Group Leader

Paul Bolton Laser

John CastroJohn Castro GTF operatorGTF operator

Jym ClendeninJym Clendenin AcceleratorAccelerator

Dave DowellDave Dowell LCLS Injector Group LCLS Injector Group LeaderLeader

Steve GiermanSteve Gierman AcceleratorAccelerator

Cécile Limborg-DépreyCécile Limborg-Déprey SimulationsSimulations

John SchmergeJohn Schmerge GTF Group LeaderGTF Group Leader





Experimental GoalsExperimental GoalsExperimental GoalsExperimental Goals

Transverse EmittanceTransverse Emittancenn < 1.2 mm-mrad (projected) < 1.2 mm-mrad (projected)

Q = 0.2-1 nCQ = 0.2-1 nC

Longitudinal EmittanceLongitudinal Emittancet < 10 pst < 10 ps

// < 0.1% < 0.1%

LaserLaserjitterjitter < 1 ps < 1 ps

Temporal shape – flat-topTemporal shape – flat-top

EElaserlaser > 100 > 100 J (UV)J (UV)

Transverse EmittanceTransverse Emittancenn < 1.2 mm-mrad (projected) < 1.2 mm-mrad (projected)

Q = 0.2-1 nCQ = 0.2-1 nC

Longitudinal EmittanceLongitudinal Emittancet < 10 pst < 10 ps

// < 0.1% < 0.1%

LaserLaserjitterjitter < 1 ps < 1 ps

Temporal shape – flat-topTemporal shape – flat-top

EElaserlaser > 100 > 100 J (UV)J (UV)





MOD1 KLY-1

GTFLASERROOM

3M LINACRF

GUN

DIAGNOSTICROOM

MOD2 KLY-2

MOD3 KLY-3

GTFControlRoom

8 m LaserTransportSystem

SSRL Injector Vault

DIAGNOSTICS

Gun Test Facility at SSRLGun Test Facility at SSRL





3m S-BandSLAC Linac

PhosphorScreens &FaradayCups

Solenoid

PCRFGun

YAG Screen& OTR Screen Quadrupole

Doublet

Phosphor Screen

Toroids

AnalyzingMagnet

FaradayCup

PhosphorScreen &EnergyFilter

GTF Linac and DiagnosticsGTF Linac and Diagnostics





Scale2" 3"0 1"

FullCell

“Half” Cell

ElectronBeamExit

Photocathode Laser Port

With single crystal(100) Cu cathode

GTF 1.6 cell S-band gunGTF 1.6 cell S-band gun





GTF BeamlineGTF Beamline





300 350 400 450 500 550 6000

5000

10000

15000uv4.tif horizontal projection

100 150 200 250 300 350 400 4500

0.5

1

1.5

2x 10

4 uv4.tif vertical projection

Laser spot used for slice emittance measurementLaser spot used for slice emittance measurement

20

40

60

80

100

120

140

160

uv4.tif

50 100 150 200 250 300

50

100

150

200

250

300

2 mm

pixels

Vertical Projection

UV Laser Image

coun

ts

Horizontal Projection





0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-5 -3 -1 1 3 5

Time (ps)

No

rma

lize

d C

ou

nts

1.8 ps FWHM

4.3 ps FWHM

Streak camera resolution at 263 nm 1 ps

Laser Pulse LengthLaser Pulse Length





Determine Longitudinal-Space at Linac Entrance

Measure Energy Spectra vs linac phaseLinear analysis allows only linear time energy correlationsNonlinear analysis allows quadratic and cubic correlations

Technique analagous to quadrupole scan of transverse emittance

Longitudinal Emittance MeasurementLongitudinal Emittance Measurement

3 m linac(varylinac)

GunSpectrometer

Energy Screen

QuadDoublet





Energy Spectrum at 15 pCEnergy Spectrum at 15 pC

100 200 300 400 500 600

100

200

300

400

-3 -2 -1 0 1 2 3-2

0

2

4

6

8

10amps

Time

Energy





Energy Spectrum at 290 pCEnergy Spectrum at 290 pC

100 200 300 400 500 600

100

200

300

400

-4 -3 -2 -1 0 1 2 3 4 5 6-20

0

20

40

60

80

100amps

Time

Energy





1222112

222

112212

1211 ; ; ;

lEt

1sin

01;

linaclinaclinac

Tlinacentrancelinaclinacerspectromet V

RRR

)sin2(sinsin

sin

1112221112

111211

linaclinaclinaclinaclinaclinac

linaclinacerspectromet VVV

V

)sin2(sin 111222 linaclinaclinaclinacerspectrometE VV

Find by fitting energy spread vs. linac phase

Linear Longitudinal AnalysisLinear Longitudinal Analysis





-40 -30 -20 -10 0 10 20 3025

26

27

28

29

30

31

Linac Phase (degrees)

Cen

tro

id E

ner

gy

(MeV

)

Egun=4.7402 Elinac=25.6895

15 pC

-30 -25 -20 -15 -10 -5 0 5 1028

28.5

29

29.5

30

30.5

31

31.5


Cen

tro

id E

ner

gy

(MeV

)

Egun=8.3787 Elinac=22.8197

290 pC

Centroid Energy vs Linac PhaseCentroid Energy vs Linac Phase

Least Square Error Fit Egun, Elinac and Flinac





-40 -30 -20 -10 0 10 20 300

10

20

30

40

50

60

70

80

90aveQ=16.4091pC t11=3.4424e-005 t12=-0.12986 t22=497.2666 keV&rad


rms

En

erg

y S

pre

ad (

keV

) 15 pC

-30 -25 -20 -15 -10 -5 0 5 100

50

100

150

200

250aveQ=289.7483pC t11=0.00066313 t12=-3.8645 t22=22589.8179 keV&rad


rms

En

erg

y S

pre

ad (

keV

)

290 pC

RMS Energy Spread vs Linac PhaseRMS Energy Spread vs Linac Phase

Least Square Error Fit 11, 12 and 22





-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4-100

-80

-60

-40

-20

0

20

40

60

80

10015 pCLinear Fit 15 pCLinear Fit 15 pC

keV

ps

Linac ExitSlope = -242 keV/ps

Linac EntranceSlope = -69 keV/ps

linac = +25°





-2 -1.5 -1 -0.5 0 0.5 1 1.5 2-200

-150

-100

-50

0

50

100

150

200290 pC

keV

ps

Linear Fit 290 pCLinear Fit 290 pC

Linac ExitSlope = -127 keV/ps

Linac EntranceSlope = -97 keV/ps

linac = +4°





Linear Analysis Fit results after linacLinear Analysis Fit results after linac

ParameteParameterr

Q = 15 pCQ = 15 pC Q = 290 pCQ = 290 pC UnitsUnits

1111 0.1250.125 2.402.40 psps22

1212 -30.1-30.1 -303-303 keV pskeV ps

2222 72907290 3840038400 keVkeV22

ll 0.9240.924 12.512.5 keV pskeV ps

E-E-

uncorrelateduncorrelated

2.622.62 8.048.04 keVkeV

t-uncorrelatedt-uncorrelated 0.01080.0108 0.06350.0635 psps

slopeslope -242-242 -127-127 keV/pskeV/ps

IIpeakpeak 99 8080 AA





Spectrometer ResolutionSpectrometer Resolution

Longitudinal Emittance Measurements made at IQ2 = 0 A

0

2

4

6

8

10

12

0.00 2.00 4.00 6.00 8.00

IQ2 (A)

re

solu

tio

n (

keV

)

300 pC

15 pC





221112

222 2 lEEtt

30

200

11

12

11

22022

2

11

0120 tbtat

ttE l

SpreadEnergyrms

LengthBunchrms

22

11

Longitudinal beam ellipse

Include distortions by adding quadratic and cubic terms

01001 ;coscos tttEEE linaclinaclinac Ray trace to fit 5 parameters

Nonlinear Longitudinal AnalysisNonlinear Longitudinal Analysis





20

QuadraticDistortion

12 = 0a > 0, b = 0

CubicDistortion

12 = 0a = 0, b > 0

Undistorted Phase Space12 = 0

a = 0, b = 0

E (keV)

t (ps)

Distortions of the Longitudinal Phase Space EllipseDistortions of the Longitudinal Phase Space Ellipse





30.2 30.25 30.3 30.350

200

400

600

800

1000

1200

1400

1600

1800

2000calc-blue,data-red66 -6 degrees

-2 -1 0 1 230.15

30.2

30.25

30.3

30.35

30.4

30.45

30.5

30.1230.1430.1630.18 30.20

200

400

600

800

1000

1200

1400

1600

calc-blue,data-red81 -9 degrees

-2 -1 0 1 230.08

30.1

30.12

30.14

30.16

30.18

30.2

30.22

30.24

30.26

30 30.02 30.04 30.06 30.080

200

400

600

800

1000

1200

1400calc-blue,data-red91 -11 degrees

-2 -1 0 1 229.95

30

30.05

30.1

30.3 30.4 30.5 30.60

200

400

600

800

1000

calc-blue,data-red55 0 degrees

-2 -1 0 1 230.3

30.35

30.4

30.45

30.5

30.55

30.6

30.65

30.7Nonlinear Fit for 15 pC as a function of linac

Nonlinear Fit for 15 pC as a function of linac

linac = 0°

linac = -11°linac = -9°

linac = -6°

Fit SpectraMeasured Spectra





Temporally Resolved Transverse Emittance MeasurementTemporally Resolved Transverse Emittance Measurement

Introduce linear chirpIntroduce linear chirp

Measure beam size in dispersive Measure beam size in dispersive sectionsection

Slice beam in energy (time) with Slice beam in energy (time) with softwaresoftware

Maintain chirp in the spectrometerMaintain chirp in the spectrometerSmall Small in bend plane at quad in bend plane at quad

Large Large in bend plane at quad in bend plane at quad

Quad scan in non-bend planeQuad scan in non-bend plane

Introduce linear chirpIntroduce linear chirp

Measure beam size in dispersive Measure beam size in dispersive sectionsection

Slice beam in energy (time) with Slice beam in energy (time) with softwaresoftware

Maintain chirp in the spectrometerMaintain chirp in the spectrometerSmall Small in bend plane at quad in bend plane at quad

Large Large in bend plane at quad in bend plane at quad

Quad scan in non-bend planeQuad scan in non-bend plane





Set Booster Phase for optimum linear chirp

Measure Transverse Beam Size vs quad strength for different energy/time slices (typically 10 slices)

Quad Scan Slice Emittance MeasurementQuad Scan Slice Emittance Measurement

BoosterGunSpectrometer

Energy Screen

QuadDoublet

Determine Transverse-Space at Quad Entrance





Quad Scan Slice Emittance MeasurementQuad Scan Slice Emittance Measurement

Measure beam size as a function of quad current in a Measure beam size as a function of quad current in a dominantly dispersive section with linearly chirped beamdominantly dispersive section with linearly chirped beam

Fit Fit 1111, , 1212, , 2222

Also measure slice centroids with respect to the projected Also measure slice centroids with respect to the projected centroid centroid

Fit xFit x00, x, x00’ (centroid position and angle)’ (centroid position and angle)Actually 5 parameters to describe the slice ellipse not just 3 Actually 5 parameters to describe the slice ellipse not just 3 Twiss parametersTwiss parameters

Measure beam size as a function of quad current in a Measure beam size as a function of quad current in a dominantly dispersive section with linearly chirped beamdominantly dispersive section with linearly chirped beam

Fit Fit 1111, , 1212, , 2222

Also measure slice centroids with respect to the projected Also measure slice centroids with respect to the projected centroid centroid

Fit xFit x00, x, x00’ (centroid position and angle)’ (centroid position and angle)Actually 5 parameters to describe the slice ellipse not just 3 Actually 5 parameters to describe the slice ellipse not just 3 Twiss parametersTwiss parameters

2

1 ( , )n n nx x x f x y dx dy

1 0( , ) ( , )n n projected n nx x f x y dx dy x f x y dx dy x x





Centroid FittingCentroid Fitting

0' '

0

'2 2 0 2 0( ) ( ) ( )

n n

n n

n n n

x xA B

x xC D

x I A I x B I x

xn, x’n measured with respect to the projected centroidLeast Square Error routine used to determine xn, x’n





Q = 15 pC and Bsolenoid =1.669 kG

Measured Beam Size and Centroids with Best FitsMeasured Beam Size and Centroids with Best Fits

-100

0

100

200

300

400

500

600

0 1 2 3 4 5 6 7 8k (m-1)

RM

S s

pot

siz

e (

m)

-250

-200

-150

-100

-50

0

50

100

150

200

Cen

troi

d P

osit

ion

at

Sp

ectr

omet

er ( m

)

beam size fitmeasured beam sizecentroid fitmeasured centroid

n = 0.52 m

= 0.42 ma = -1.3x0 = -31 m

x'0 = -97 rad





Q = 300 pC and Bsolenoid =1.982 kG

Measured Beam Size and Centroids with Best FitsMeasured Beam Size and Centroids with Best Fits

-200

0

200

400

600

800

1000

1200

0 1 2 3 4 5 6 7k (m-1)

RM

S s

pot

siz

e (

m)

-600

-500

-400

-300

-200

-100

0

100

200

Cen

troi

d P

osit

ion

at

Sp

ectr

omet

er ( m

)

beam size fitmeasured beam sizecentroid fitmeasured centroid

n = 1.95 m

= 3.88 ma = -4.56x0 = 126 m

x'0 = 80 rad





Beam Images as a function of Quad StrengthBeam Images as a function of Quad Strength

70

80

90

100

110

120

qslice0101.tif

100 200 300 400 500

20

40

60

80

100

80

100

120

140

qslice0201.tif

100 200 300 400 500

20

40

60

80

100

80

100

120

140

160

180

qslice0301.tif

100 200 300 400 500

20

40

60

80

100

100

150

200

qslice0401.tif

100 200 300 400 500

20

40

60

80

100

100

150

200

250

qslice0501.tif

100 200 300 400 500

20

40

60

80

100

80

100

120

140

qslice0601.tif

100 200 300 400 500

20

40

60

80

100

Energy/Time Axis (pixels)

Hor

izon

tal B

eam

Siz

e (p

ixel

s)






Head

High Energy Low Energy

Tail

Converging beam (underfocused)

Slice ImageSlice ImageH

oriz

onta

l Bea

m S

ize

(pix

els)





Head

Tail

Horizontal Beam Size Projections (pixels)

Converging beam (underfocused)






Head

High Energy Low Energy

Tail

Beam near waist

Slice ImageSlice ImageH

oriz

onta

l Bea

m S

ize

(pix

els)





Head

Tail

Horizontal Beam Size Projections (pixels)

Beam near waist





Beam at the Spectrometer ScreenBeam at the Spectrometer Screen

-1.5 -1 -0.5 0 0.5 10

50

100

150

0 5 100

1

2

3

4

slice

x(m

icro

ns)

1.982kG1.937kG

1.967kG

Time (ps)

Cu

rren

t(a

mp

eres

)

head tail

Energy/Time

Sp

ectr

omet

er

Imag

e

-1.5 -1 -0.5 0 0.5 10

50

100

150

0 5 100

1

2

3

4

slice

x(m

icro

ns)

x(m

icro

ns)

1.982kG1.937kG

1.967kG

Time (ps)

Cu

rren

t(a

mp

eres

)

head tail

Energy/Time

Sp

ectr

omet

er

Imag

e

-1.5 -1 -0.5 0 0.5 10

50

100

150

0 5 100

1

2

3

4

slice

x(m

icro

ns)

1.982kG1.937kG

1.967kG

Time (ps)

Cu

rren

t(a

mp

eres

)

head tail

Energy/Time

Sp

ectr

omet

er

Imag

e

-1.5 -1 -0.5 0 0.5 10

50

100

150

0 5 100

1

2

3

4

slice

x(m

icro

ns)

x(m

icro

ns)

1.982kG1.937kG

1.967kG

Time (ps)

Cu

rren

t(a

mp

eres

)

head tail

Energy/Time

Sp

ectr

omet

er

Imag

e

Q = 290 pC, linac = + 4 °





Twiss parameters, offsets and current as function of timeTwiss parameters, offsets and current as function of time

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-3.0 -1.0 1.0 3.0

Time (ps)Projected values displayed at t=0

n (

m

)

-6.0-4.0-2.00.02.04.06.08.0

a,

(m

),

(m

-1)

xn

x

ax

x

Q = 300 pC, Bsol = 1.937 kG

0.0

20.0

40.0

60.0

80.0

100.0

-3.0 -1.0 1.0 3.0


I(A

)

-600.0

-400.0

-200.0

0.0

200.0

X0

(m

), X

0' (

ra

d)

I

X0'

X0






0.00.51.01.52.02.53.03.5

-3.0 -1.0 1.0 3.0


n (

m

)

-10.0

-5.0

0.0

5.0

10.0

a,

(m

),

(m

-1)

xn

x

ax

x

0.0

20.0

40.0

60.0

80.0

100.0

-3.0 -1.0 1.0 3.0


I (A

)

-800.0

-600.0

-400.0

-200.0

0.0

200.0

400.0

X0

(m

), X

0' (

ra

d)

I

X0'

X0

Q = 300 pC, Bsol = 1.982 kG





-1200 -1000 -800 -600 -400 -200 0 200 400 600-800

-600

-400

-200

0

200

400

600

X (microns)

X' (

mic

rora

dia

ns)

10

9

8

7

6

5 4

3 2

1

Projected

-1200 -1000 -800 -600 -400 -200 0 200 400 600-800

-600

-400

-200

0

200

400

600

X (microns)

X' (

mic

rora

dia

ns)

10

9 8

7

6

5

4

3

2

1

Projected

Bsol = 1.937 kG Bsol = 1.982 kG

Phase Space at Q = 300 pCPhase Space at Q = 300 pC






0.0

2.0

4.0

6.0

8.0

10.0

-1.5 -0.5 0.5 1.5


I (A

)

-200.0

-100.0

0.0

100.0

200.0

X0

(m

), X

0' (

ra

d)

I

X0'X0

Q = 15 pC, Bsol = 1.609 kG

0.0

0.2

0.4

0.6

0.8

1.0

-1.5 -0.5 0.5 1.5


n (

m

)

-0.50.00.51.01.52.02.53.0

a,

(m

),

(m

-1)

xn

x

ax

x






0.0

2.0

4.0

6.0

8.0

10.0

12.0

-1.5 -0.5 0.5 1.5


I (A

)

-300.0

-200.0

-100.0

0.0

100.0

200.0

300.0

X0

(m

), X

0' (

ra

d)

I

X0'X0

Q = 15 pC, Bsol = 1.669 kG

0.0

0.2

0.4

0.6

0.8

-1.5 -0.5 0.5 1.5


n (

m

)

-3.0-2.0-1.00.01.02.03.04.05.0

a,

(m

),

(m

-1)

xn

x

ax

x





-400 -300 -200 -100 0 100 200 300 400-400

-300

-200

-100

0

100

200

300

400

X (microns)

X' (

mic

rora

dia

ns)

10 9

8 7

6

5

4

3

2

1

Projected

-400 -300 -200 -100 0 100 200 300 400-400

-300

-200

-100

0

100

200

300

400

X (microns)

X' (

mic

rora

dia

ns)

10 9

8 7

6 5

4

3

2

1

Projected

B solenoid = 1.609 kG B solenoid = 1.669 kG

Phase Space at Q = 15 pCPhase Space at Q = 15 pC





Measured and Reconstructed Projected EmittanceMeasured and Reconstructed Projected Emittance

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

1.5 1.6 1.6 1.7 1.7 1.8 1.8 1.9 1.9 2.0 2.0

Bsol (kG)

n (

m)

Measured Projected Emittance

Weighted Average Slice Emittance

Reconstructed Projected Emittance with offsets

Reconstructed Projected Emittance zero offsets

measured

slice

reconstruct with offset

resconstruct with zero offsetQ = 15 pC

Q = 300 pC





Slice EmittanceSlice Emittance

0

0

0

0 0

0

' '

' ' ' '

2 ' '11

' ' ' '12

2' ' ' '22

1,

1,

1,

1,

1,

n

n

n

n n

n

nn

nn

n nn

n nn

n nn

x xG x x dx dxQ

x x G x x dx dxQ

x x G x x dx dxQ

x x x x G x x dx dxQ

x x G x x dx dxQ





Reconstructed Projected EmittanceReconstructed Projected Emittance

0 0

0 0

0 11

0 0

' '0

1

' '0 0

1

' '0

10 0

' ' ' ' '0

10 0

2 ' ' 2 211 0 0 0

10 0

' ' ' '12 0

0 0

, ,

,

1 1,

1 1,

1 1,

1 1,

n

n

n

N

nn

N

nn

N

nn

N

nn

N

n nn

nn

G x x G x x

Q G x x dx dx Q

x xG x x dx dx Q xQ Q

x x G x x dx dx Q xQ Q

x x G x x dx dx Q x xQ Q

x x x x G x x dx dx QQ Q

12

0 22

' '0 0 0 0

1

2' ' ' ' '2 '222 0 0 0

10 0

1 1,

n

n

N

n n

N

n nn

x x x x

x x G x x dx dx Q x xQ Q





Sources of Time Dependent KicksSources of Time Dependent Kicks

Transverse WakefieldsTransverse WakefieldsLinacLinac

Normal Incidence MirrorNormal Incidence Mirror

GunGun

RF kicksRF kicksGun ExitGun Exit

Linac EntranceLinac Entrance

Linac ExitLinac Exit

RF couplersRF couplers

LaserLaserAlignmentAlignment

Time-Space correlationTime-Space correlation

Transverse WakefieldsTransverse WakefieldsLinacLinac

Normal Incidence MirrorNormal Incidence Mirror

GunGun

RF kicksRF kicksGun ExitGun Exit

Linac EntranceLinac Entrance

Linac ExitLinac Exit

RF couplersRF couplers

LaserLaserAlignmentAlignment

Time-Space correlationTime-Space correlation





Xoffset vs Z for Q = 15 pC and Bsol = 1.669 kGXoffset vs Z for Q = 15 pC and Bsol = 1.669 kG

Transverse offset vs Longitudinal Position for 10 beam slices

-2000

-1500

-1000

-500

0

500

1000

1500

2000

0.000 2.000 4.000 6.000 8.000

z position (m)

x o

ffse

t (

m)

Slice 1Slice 2Slice 3Slice 4Slice 5Slice 6Slice 7Slice 8Slice 9Slice 10Components





Xoffset vs Z for Q = 300 pC and Bsol = 1.982 kGXoffset vs Z for Q = 300 pC and Bsol = 1.982 kG

Transverse offset vs Longitudinal Position for 10 beam slices

-2000

-1500

-1000

-500

0

500

1000

1500

2000

0.000 2.000 4.000 6.000 8.000

z position (m)

x o

ffse

t (

m)

Slice 1Slice 2Slice 3Slice 4Slice 5Slice 6Slice 7Slice 8Slice 9Slice 10Components





Time Dependent Angle in the linac for different ChargesTime Dependent Angle in the linac for different Charges

Time Dependent Kick

-400

-300

-200

-100

0

100

200

300

400

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Time (ps)

Tra

ns

ve

rse

Kic

k (

rad

)

Linac Center

Linac Exit

Q = 15 pC

Bsol = 1.669 kG

Time Dependent Kick

-800

-600

-400

-200

0

200

400

-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0

Time (ps)

Tra

ns

ve

rse

Kic

k (

rad

)

Linac Center

Linac Exit

Q = 300 pC

Bsol = 1.982 kG





x’ vs zx’ vs zxxmaxmax 35 35 radrad

x offset in 3-m structure = 1 mm, x offset in 3-m structure = 1 mm, qq = 300 pC, = 300 pC, IIpkpk 120 A 120 A

x vs zx vs zxxmaxmax 20 20 mm

Transverse Wakefield due to Linac MisalignmentTransverse Wakefield due to Linac Misalignment

Courtesy of P. Emma





Back Propagate Linac Wakefield SimulationBack Propagate Linac Wakefield Simulation

Simulated Linac Wake producesSimulated Linac Wake producesXX00 = -20 = -20 m at linac exitm at linac exit

X’X’00 = -35 = -35 rad at linac exitrad at linac exit

Back propagate output conditions and assume no Back propagate output conditions and assume no wakefield to see where the beams intersectwakefield to see where the beams intersect

X = 0 at z = 50 cm from linac exitX = 0 at z = 50 cm from linac exit

Simulated Linac Wake producesSimulated Linac Wake producesXX00 = -20 = -20 m at linac exitm at linac exit

X’X’00 = -35 = -35 rad at linac exitrad at linac exit

Back propagate output conditions and assume no Back propagate output conditions and assume no wakefield to see where the beams intersectwakefield to see where the beams intersect

X = 0 at z = 50 cm from linac exitX = 0 at z = 50 cm from linac exit





-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

1.5 1.6 1.7 1.8 1.9 2.0

Bsol (kG)

Zcr

oss

(m

)

Gun offset position 0 crossing

Linac offset position 0 crossing

Gun angle offset 0 crossing

15 pC 300 pC

Slice Intersection PointsSlice Intersection Points





End of PresentationEnd of Presentation


gun test facility layout longitudinal emittance measurement technique longitudinal emittance

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