1. Experience with photoinjector at ATF
Vitaly Yakimenko
October 11, 2006
LCLS ICW2006

2. Laser uniformity

3. Standardized BPM (zoom lens with doubler and 20 cm achromat)
Old style
Min zoom
Max zoom
Work distance [mm]
155
160
Field of view [mm]
18x13
59x37
11x7
Relative intensity [a.u.]
279 60 62
Resolution
[ln/mm]
center 20 6 29
edge 14 4
Pixel Calibration [mm/pix]
24x29
77x91
14x17
Image

4. Laser alignment on the cathode
Emittance degrades from 1mm to 1.5mm for 200mm shift from the “centered” position
Laser profile on the cathode after 10 holes mask:
e-beam after the gun:
RF phase optimized to enhance distortions
Laser “centered” on the cathode
Laser moved ~200mm

5. Four step to improve emittance (FEL 2001, Darmstadt)
Stability of the driving laser and RF
Optimization of the drive laser (Mg plug cathode with Qe~0.25% is used to reduce laser load)
Accelerating gradient in the RF GUN and operating phase
Beam based alignment of the focusing quads to transport beam thought the linac center.
CCD Images of the 0.5 nC /60 MeV beam after linac

6. BPM resolution limit
Beam images taken consequently with the six different diagnostics under stable experimental conditions (the charge Q ~ 500 pC). µm
Electron beam horizontal spot size as a function of charge, measured with the scintillating diagnostics and the OTR.

7. Fitting the beam size using multiple BPMs to resolve emittance
BPMs were used to measure beam sizes >200 mm and quads for smaller sizes
Focusing properties of the transport line were extensively studied for the tomographic phase space rotation.

8. New Capabilities: Digital Mirror Array
Study underway to allow generation of flattop beams with <5% P-P variation
Shaping of an Optical Beam
Intensity Profile
-2nd order output
2nd order output
Input Signal
Mirror tilt axis