Cecile Limborg-Deprey Injector [email protected] October 12 2004 Injector Physics...

Cecile Limborg-Deprey

Injector Physics [email protected]

October 12 2004

Injector PhysicsC.Limborg-DepreyInjector Physics

C.Limborg-Deprey

• Diagnostics and Commissioning– GTL measurements

• Thermal emittance measurements• Gun spectrometer

– Straight Ahead spectrometer • Energy measurements• Slice emittance measurements (both planes)

– Low Charge tunings• RF studies

– L01 dual feed– RF gun dual feed– mode 0 studies



October 12 2004

Gun S1 S2 L0-119.8MV/m

L0-224 MV/m

‘Laser Heater’

‘RF Deflecting cavity’ TCAV1

3 screen emittance measurement

6 MeV = 1.6 m ,un. = 3keV

63 MeV = 1.08 m ,un. = 3keV

135 MeV = 1.07 m ,un. = 3keV

DL1

135 MeV = 1.07 m ,un. = 40keV

Spectrometer

Lina

c tu

nnel

UV Laser 200 J, = 255 nm, 10ps, r = 1.2 mm

Spectrometer



October 12 2004

‘Laser Heater’

‘RF Deflecting cavity’ TCAV1

3 screen emittance measurement

Gun Spectrometer

Lina

c tu

nnel

Straight Ahead Spectrometer

Uniformity + Thermal emittance

1

2

43

Commissioning DiagnosticsCommissioning Diagnostics

YAG1 YAG2



October 12 2004

Above: Laser cathode image of air force mask in laser room.

Below: Resulting electron beam at pop 2.

Above: Laser cathode image with mask removed showing smooth profile.

Below: Resulting electron beam showing hot spot of emission.

Laser masking of cathode image at DUVFEL

Courtesy W.Graves

Point-to-point imaging of cathode on YAG1

Emission uniformityEmission uniformity1



October 12 2004

YAG2

==

Image of

divergence of sourceAssumes th = 0.6 mm.mradAssumes th = 0.6 mm.mrad

Very good resolution of divergence

Infinite-to-point imagingwhat type of momentum

distribution?

Thermal Emittance1



October 12 2004

Gun Spectrometer

Energy Absolute energy

Alignment using laser Spectrometer field calibration

Correlated Energy Spread for all chargesUncorrelated energy spread for low charges

Introducing a time-energy correlation (varying injection phase)

Slice thermal emittanceRelay imaging system from YAG1 to spectrometer screens

Point-to-point imaging in both planes

Uniformity of line density

Energy Absolute energy

Alignment using laser Spectrometer field calibration

Correlated Energy Spread for all chargesUncorrelated energy spread for low charges

Introducing a time-energy correlation (varying injection phase)

Slice thermal emittanceRelay imaging system from YAG1 to spectrometer screens

Point-to-point imaging in both planes

Uniformity of line density

YAG01

Spectrometer

YAGG1

YAGG2

Quadrupoles

2



October 12 2004

High Charge Operation : 1nC Nominal tuning – no quadrupole on –

Very good linearity

Longitudinal at YAG1

YAGG1YAGG1



October 12 2004

Resolves line density uniformity at high charge

YAG1

RF + 25 / nominal

Quadrupoles on for manageable image size

Resolves modulation

+/- 8% modulation on laser beam



October 12 2004

Laser Heater

Transverse RF Cavity

OTR Emittance Screens

DL1 Bend

Straight Ahead Spectrometer

135MeV Diagnostics

Point-to-point imaging of the 75 m waist (OTR5)

Horizontal slice emittanceVertical deflecting cavity + 3screen

Vertical slice emittanceQuad scan + spectrometerQuad Scan + Dogleg bend

Verification of thermal emittance

Longitudinal Phase space Vertical deflecting cavity + spectrometerEfficiency of laser heater

(spectrometer has 10 keV resolution)

Horizontal slice emittanceVertical deflecting cavity + 3screen

Vertical slice emittanceQuad scan + spectrometerQuad Scan + Dogleg bend

Verification of thermal emittance

Longitudinal Phase space Vertical deflecting cavity + spectrometerEfficiency of laser heater

(spectrometer has 10 keV resolution)

6D beam measurements



October 12 2004

Longitudinal Phase Space at waist • Transverse deflecting cavity

y / time correlation

(1mrad over 10ps )

• Spectrometer

x / energy correlation

From PARMELA simulations (assuming 1m emittance), resolution of less than 10 keV

rms fwhm

Spectrometer + Vertical deflecting cavity

Direct longitudinal Phase Space representation



October 12 2004

Alternate tunings for improving th = 0.6 mm.mrad per mm laser spot size

Name Q

(nC)

Laser pulse (ps)

r

(mm)

th

(m.rad)

80

(m.rad)

RF

()

80 5%

Nominal 1 10 1.2 0.72 0.9 32 2.5

1 nC, 17.5 ps 1 17.5 0.85 0.5 0.75 33 1.5

0.2nC,10ps 0.2 10 0.39 0.234 0.38 37 2.5

0.2nC,5ps 0.2 5 0.42 0.25 0.37 32 5

1nC 0.2nC



October 12 2004

RF Studies- L01 coupler

Dipole moment

Quadrupole moment

From Z.Li, L.Xiao,

ACD/SLAC

0.0200.20Cross Dual

0.0040.04Race-track dual

0.0630.63Symmetric dual

0.0780.78SLAC Single feed

Head-tail angle (rad/m)

()/m

0.0200.20Cross Dual

0.0040.04Race-track dual

0.0630.63Symmetric dual

0.0780.78SLAC Single feed

Head-tail angle (rad/m)

()/m



October 12 2004

RF Gun – Racetrack in full cell 2d-: no port = benchmark omega3p/sf

3d-cylin: with coupling ports- cell cylindrical

3d-rtrack: with coupling ports- cell racetrack

Full : with laser ports + racetrack

Full retuned: with laser ports + racetrack+ retuned

-6-4-202468

-180 -130 -80 -30 20 70 120 170

rf phase (degree)

cylindrical cavity (lc=2.475cm)

racetrack cavity (lc=2.413cm)with d=0.315cmracetrack cavity (lc=2.413cm)with d=0.356cm

Qu

adru

po

le

r(1

/m)

-8-6-4-202468

-180 -130 -80 -30 20 70 120 170-180 -130 -80 -30 20 70 120 170

rf phase (degree)

cylindrical cavity (lc=2.475cm)

racetrack cavity (lc=2.413cm)with d=0.315cmracetrack cavity (lc=2.413cm)with d=0.356cm

Qu

adru

po

le

r(1

/m)

-8

From L.Xiao, ACD/SLAC

b b

d

x = y =0.88

x = 0.96 y =1.01

x = y = 0.90

x = 0.97 , y = 0.99

x = 0.91, y = 0.915



October 12 2004

RF Gun – Mode 0 studies

dF 3.4 MHz 8 MHz

3s, Vcath. in 0 mode 11.77 MV/m 4.96 MV/m

0.82s, Vcath. in 0mode 10 MV/m 5.7 MV/m

3.4MHz mode separation 8MHz mode separation

From Z.Li, ACD/SLAC

Solution : Klystron Pulse shaping



October 12 2004

Conclusion

http://www-ssrl.slac.stanford.edu/lcls/prd/1.2-001-r0.pdfDiagnostics were designed to provide

Tools for performing correctly emittance compensation 6D characterization of beam at end of injector

Diagnostics for degraded beam startedTemporal Modulation laser Large emittance => impact on energy spread measurement

RF studies L0-1 dual feed: racetrack shape Gun dual feed: racetrack shapeMode0 : problem identified; working on solution



October 12 2004

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