The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

BEAM DIAGNOSTICS WITH VISIBLE SYNCHROTRON RADIATION ATNEWSUBARUS. Hashimoto, Y. Fukuda and A. Ando
NewSUBARU, 1-1-2 Kouto, Kamigori, Akougun, Hyogo, 678-1205, JAPANAbstract
We have constructed two optical monitors using visible
synchrotron radiation (SR) from bending magnets ·(BM)for beam diagnostics in the NewSUBARU storage ring.
The visible SR is observed by a CCD camera andacquired image data is processed by a real-time image
processing system based on PC and LabVIEW.
Measurement of visible SR spot size provides an electron
beam size and emittance.
The measured horizontal
emittance of 38nrnrad is in good agreement with designedvalue. In this paper the detail of visible SR monitor andthe results of measurements of electron beam size andemitance are shown.

and optical GPIB cable. A small CCD camera for mirror
calibration is equipped near each remote-controlled
mirror.
As for SR2, a CCD camera for observation of SR is
located inside the tunnel.
Inside tunnel~---·---"""'"--------·-·CCDcamera

1 INTRODUCTION
Observation of visible SR is one of useful tools forbeam diagnostics [1]. The transverse beam size O'x,y isobtained by forming an image of the beam cross section
by means of emitted SR. To evaluate the emittance Ex,yfrom O'x,y. the lattice functions (a,p,y,n) at the source
point have to be known. We can use following relationsax =~exf3x(s)+77 2 (s)ac/,ay =~Ey{3y(s)M

Manual control

RRemote controlllall

halfmirror

M8f I mirrorFigure I: Basic layout of SRI.

2.2 PC based image acquisition and processing(1)

where 0' 0 is energy spread, Px,Y betatron function, Tl
dispersion function. The vertical dispersion is usuallysmall and can be neglected. The obtained resolution islimited by diffraction effect O'diF0.206(/}p) 113 and depthof field effect O'doF0.34(/.}p) 113 where 'A is observed
wavelength and p is radius of curvature of electron orbit.

(Hardware)
A PC with a Pentium III processor and National
Instruments (NI) PCI-1408 PCI card was used for image
acquisition and processing. The analogue video signal inNTSC format of a standard CCD camera in theexperimental hall is transmitted to the PC in the control
room by coaxial cable. The entire image frame of data
can be acquired to the PC at a rate of 30 Hz.

2 VISIBLE SR MONITOR.-------------c=p .--=sR~~coaxial cable
ceobeam orbit

2.1 General Layout
There are two visible SR monitor, SRI and SR2, near
BM7 and BMIO respectively. The general layout of SRI
is shown in Fig. I. Visible component of SR from theentrance of BM is extracted through the MO mirror (Aucoated copper block) and a quartz window. In SRI
several mirrors are used in order to guide the radiation tothe experimental hall, where adjustment of opticalcomponents such as neutral density filter, polarization
filter and band pass filter can be performed. The mirrors
inside the tunnel can be remote-controlled from thecontrol room using optical GPIB converter OMRON ZlO-367-(switcher~~------'·I-·"''~ ___P_C_I!'~·.

PCI-1408

IDI~PC

Figure 2: Hardware configuration.

The 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

(Software)
An operating system running on the PC for image
processing is Windows NT. The image acquisition andprocessing application was developed with NI Lab VIEW
and IMAQ Vision software. IMAQ Vision provides
complete functionality for scientific analysis. By image
processing of SR the standard deviation of r.m.s. beam
size and shift of beam center can be measured in real time.
The speed of image processing is about a few frames per
second. Typical image from the CCD camera and its
processed image are shown in Fig. 3. The resolution ofimage processing is 0.073

SR, the transverse beam sizes were measured withvarying stored current in single bunch mode (Fig.4).
From this figure we have beam sizes at zero stored
current of cr/=0.12mm 2 and cr/=0.03lmm 2 • Subtracting
the diffraction error and depth of field error,
O"diF0.0165mm and 0"doF0.0272mtn, respectively, wehave cr/=0.119mm 2 and cr/=0.03mm 2 •Assuming designed betatron functions at the source
point ~.=2.49m and ~y=10.6m, we have horizontal andvertical emittances, Ex=38 nm*rad and Ev=2.9 nm*rad.
These values are in good agreement with designed ones
[2].
0.4 ..,•••,••Y''T'"f"'T''T''I'..I''T"'l'..

single bunch
t''T''I''T'T''T''T''I..r'I'''I'"T''T'T"T''T''I-·r··;r•·r·····l''' ''"f''Y ..I' .. f''............ t ..........

,-...

0.3s

0.2

"'s'-'i' •.
!
····--6~---··········t········--·-·--i---···········-t-········•.j._ ••••!.___·········+···· -----------!--·-·

L~-;~···~-~~l········-·1. . .

No':i 0.1
Figure 3: Before (left) and after (right) an image
processing of the visible SR.

0-~---·....

····•····t······
0345678I 213 (rnA 213)bFigure 4: Horizontal and vertical beam sizes versus
stored current.

3 BEAM SIZEAND EMITANCEMEASUREMENTS
Theoretically speaking, the increase of energy spreadis proportional to the third power root of the stored
current Ib 113 in single bunch mode, cr11=Aib 113 • From eq.lthe square of horizontal and vertical beam sizes are given
bya~ = £xf3x (s) + 1J2(s)A 2/;13'a~ =£rf3r(s)(2)
Thus the natural emittance can be calculated frombeam size with zero current. Using band pass filter of
400 nm and polarization filter to select only a-mode of

4 REFERENCES[I] A. Hoffman, F. Meot, NIM A203, pp.483 (1982).
[2] A. Ando, Y. Fukuda, S. Hashimoto, "Beam size
blowup and energy widening in NewSUBARU", NIM
A, to be published.

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