Beam Diagnostics of the SPring-8 Storage Ring

Characteristics of synchrotron radiation (SR) are closely related to those of the source electron beam. For
example, pulsed nature of SR is originated from bunched structure of the electron beam. Brilliance of SR isdominated by transverse size and angular divergence of the electron beam. This laboratory course is practice at
the SPring-8 diagnostics beamline I (BL38B2).

1) Accelerator diagnostics beamline I (BL38B2).
BL38B2 has a bending magnet light source, and wide band spectral availability from visible light to X-rays
has been achieved. The schematic layout of the beamline is shown in Fig.1. The visible synchrotron light istransported to a dark room on the experiment hall, where single bunch purity is measured by gated photon
counting method and bunch length is measured by a streak camera. X-rays are used in the optics hutch tomeasure profiles of the electron beam (X-ray beam imager).

Accelerator Tunnel
eBending Magnet
MovableMetal Filter
4-Jaw Slit
Double Crystal
Monochromator

MirrorFZP
X-ray Zooming Tube

Streak CameraBunch Purity
MonitorOptics Hutch

Dark RoomExperiment HallFIR laser

Laser RoomFig.1 Layout of the accelerator diagnostics beamline I. Components of the beam diagnostics systems are shown.

2) Practice2-1) Photon counting
When the photon beam is attenuated by slits and filters, we can count photons from each electron bunch one
by one (Fig. 2). The counting rate of photons are in proportion to the number of electrons in each bunch. Thus
the time spectra of detected photons give us the information on the filling pattern of the storage ring. The block
diagram of the photon counting system prepared for the BL practice is shown in Fig. 3.

Storage RingSRSlit

ND iflterPhotonDetector
Fig. 2 Concept of photon counting method.

Cable for HVshutter
MC PPM TSR
N D slitfilter

D iscri.
Cablef or Signalstartatt.
∆t
209kH zD ivi
der508MH z

V ariable
D elay1/2436

Fig.3 Block diagram of the photon counting system for the BL practice.

HVMC ATA Cstop∆V∆V ∝∆t2-2) Streak Camera
A streak camera is a fast device to detect short light pulses. The length of SR pulses gives information of thelength of electron bunch. The principle of operation of a streak camera is illustrated in Figs. 4 and 5. At theSPring-8, we use the streak camera Hamamatsu C5680 with time resolution of 2 ps. The timing
signal system for operating the streak camera is shown in Fig. 6.

Circuit for Vert ical Sweep

Trigge r

St reak Imageon the Screen

Sweep Elect rod e（Vert ical ）Slit

Phosphor Screen（Elect ron→Pho to n）
MCP（Int ensifies
Elect ronBeam)Pho tocat hode
（Phot o n→Elec tron） Accelerat ing
Elec trode

Project ed Time Pro fileFig.4 Principle of operation of a streak camera (single sweep mode).

T rigger

Circu ti fo r Vert ical Sweep

Circuit for Horizon tal Sweep

TriggerSlit

Sweep Ele ct rod e
MCP（Vert ical）（In tensifies
Elec tron
Beam )

Phot oca thode（Phot o n→Elect r on）
Accele rat ing
Elect rode

St reak Imageon the Screen

Phosphor Screen（Elect r on→Phot o n）

Sweep Elect rod e（Ho rizont al）

Fig.5 Principle of operation of a streak camera (dual sweep mode).

Project ed Time Pro fileD ivider1/2436

TriggerU nit
C4547〜10H z508M H z

Streak Cam era
C5680-01
H ori.Scan U nit

BPFBPF
D ivi
der1/7508MH z508MH z508M H z

V ariable
D elay72.65MH z

D elay U nit
C6878

V ert.
ScanU nit

Ref.in72.65M H z

Cam era Cont.
C4742-95

Fig.6 Timing signal system for operating the streak camera.

Pow er
Supply