Introduction
GLAD Ver. 5.5

s = 100 µm(First aperture)s = 200 µm

s = 3 mms = 6 mm (second aperture)s = 10 mm

Fig. 8: Horizontal beam profile at the aperture

KEKB Injector Linac•600-m-long electron/positron injector:	

•100-m-long straight section	

•500-m long straight section	

• Provides the beams for four independent rings:	

•KEKB e-: 8 GeV, 1 nC	

•KEKB e+: 3.5 GeV, 1 nC (primary electron : 3.7 GeV, 10 nC)	•PF: 2.5 GeV, 0.1 nC 	

•PF-AR: 3 GeV, 0.2 nC 	s=0ms=1ms = 40 ms = 50 m

s = 20 m

s=1m

s = 10 m

s = 20 m

s = 30 m

40 m

s = 50 m

s = 60 m

s = 70 m

s = 80 m

s = 60 m

GLAD Ver. 5.5s = 100 m

s = 80 m

Fig. 9: Laser profile (atmospheric)Fig. 1: Schematic drawing of KEKB Injector Linac

In airLaser alignment system(1) Laser Diode (Mitsubishi Electric, ML101J27)	

•Single mode fiber coupling (core diameter: Φ3.5 μm)	•Wavelength : 660 nm (red)	

(2) Laser direction control: 5-axis autostage	

!X, Y, Z, θ , and φ	(3) Quadrant silicon photodiode (PD)	

• Φ10 mm (OSI Optoelectronics, Model SPOT-9D)	

(4) Detector	

In vacuum (25 [Pa])s = 90 m

s = 100 m

Fig. 10: Horizontal profile
Waist position: 50m
Distance between fiber and spherical mirror: 15.29 mm
Front view

Horizontal meter

Vertical meter

Fig. 11: Laser profile at 100-m point
Back view
Voltage output⋅Difference between horizontal and vertical
waist position is caused by the oblique
incidence to spherical mirror.	

leverFig. 3: Photograph of detector
moduleFig. 12: Simulation and measurement resultof laser beam size

Fig. 2: Photograph of PD and chamber

Alignment method

Fig. 4: Schematic drawing of laser-based alignment

Fig. 5: Girder and acceleratingstructure(1) Reference laser line:
At the most upstream/downstream position(PD#1, PD#2) , adjust the laser position and angle
like (X#1,Y#1) = (X#2,Y#2) = (0, 0)

s = 20 m

s = 40 m

s = 60 m

s = 80 m(!) Alignment measurement and adjustment"•At Acc. Girder #N, adjust the girder position
so that PD position is (XNu, YNu) = (XNd, YNd) = (0, 0).
(*) Pre-alignment has been carried out before girder installation.
Relative position among center of PD, accelerating structure, and plate

Summary and Future Plan

Optical system

Fig. 6: Schematic drawing of optical system

Fig. 7: Enlarged drawing of flat mirror•Optical system consists of a flat mirror and spherical mirror (D=152.4, f = 152.4 mm)	•Fiber scheme:	

• Reduction of pointing stability 	• Power supply of laser can be installed in klystron galley (avoidance of radiationinjuries)	

•First aperture makes the diffraction beam. Second aperture cut the side-lobe. Only narrowmain-lobe beam is utilized for the alignment measurement (Airy beam)	

•Laser-based alignment system by using PD with Φ10 mm	

• Need a collimated beam propagation along 500-m-long as
small diameter as possible.	

•Reconstruction of alignment system in KEKB linac:	

• Development of the new optical system and laser source.	

• Preliminary test at 100-m-straight line and simulation havebeen carried out.	

•Results of measured and simulated beam sizes.	

• Good agreement for waisted beam	• Bad agreement for collimated beam	•More accurate simulation with aberration effect of sphericalmirror	

•We need to develop the robust laser extraction part (stable girder)
and design the optimized optical system.	

•Laser propagation test and alignment for the 500-m-long straightsection.