JAERI-Conf 95-021

3a2-2
Study. on Quantum Beam Science by using Ultra Short Electron Pulse, FEL, andSlow Positron Beam at ISIR, Osaka University
Y. Yoshida, S. Tagawa, S. Okuda, Y. Honda, N. Kimura, T. Yamamoto, and G. Isoyama
The Institute of Scientific and Industrial Research, Osaka Univet·sity
8-1 Mihogaoka, Ibaraki, Osaka 567, Japan

Abstract
Three projects for quantum beam science,
an ultra fast electron pulse, a free electron laser,
and a slow positron beam, has been started byusing 38 MeV L-band and 150 MeV S-handlinacs at ISIR in Osaka University.
Both study on the production of three beams
and study on quantum material science by using
three beams will play an important role in thebeam science.
1. Introduction

Fig. 1 Generation of Quantum beams
and its application.

The new research system has been started
since this April by the reorganization of theInstitute of Scientific and Industrial Research(ISIR) at Osaka University. The Radiation
Laboratory in ISIR will play an important roleof studies on quantum beam science incollaboration with the division of quantum beamscience and technology which is composed of two
departments, department of accelerator scienceand department of beam material science.
Fig 1 shows a new project that three kindsof quantum beam, ultra short electron pulse,FEL, and slow positron beam, generated byusing the electron linac are used for thequantum beam science.
Picosecond pulse radiolysis by using theultra short electron pulse is very important for
the elucidation of the primary process of theradiation chemistry which contributes to thematerial science. Infrared FEL is also important

for the material analysis. The analysis of atomic
and molecular structure near matedal surface
can be achieved by using the slow positrim.
In this paper, the developments of threequantum beams and its application aredescribed.
2. Quantum Beams Genet·ation
The ultra shot·t pulse is produced by the 38 MeV
L-band linac with the pulse compressed system
which is composed of two 1/12 sub hannonic
prebunchers and a 1/6 sub harmonic prebuncher.
The FEL is produced by using the L-band linac.
The slow positron is generated by using 150 MeV
S-band linac. Fig. 2 shows the location of the linacs
and the experimental ports for the quantum beams.

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ultra fast pulse
Fig. 2 The Location of S&L-band linacs and experimental ports for three beams.

controlled.
The first expedment of the new system will
start this autumn.

3. Ultra Short Electron Pulse

A 20 ps single bunched beam from the L-band
linac has the maximum charge of 67 nC, which ishundred times larger than that of typical S-band
linac. The highly intended beam as irradiation
source has many advantages f(Jr jpicosecond pulse
radiolysis.
A new picosecond pulse radiiolysis system[l]combined with a femtosecond laser is underdevelopment. Fig. 3 shows the block diagram of thenew system. The femtoscond Ti-sapphier laser isused as the analyzing light instead of theCherenkov light produced by the electron beam. [2]The laser analyzing light can cover the wide
wavelength region from ultra violet to infrared byusing the technique of second harmonic generation,
third
harmonicgeneration,
andopticalparametoric oscillation.
The important point to get the time resolutionof picosecond is the timing jitters between theelectron pulse and the laser pulse. The timing
jitters is within 10 ps by synchronization of rf by
which both the linac and the laser can be

4. Infrared Free Electron Lase,-FEL experiments in visible region by usinglinac have been succeeded at about 10 places in theworld. For Infrared FEL, the development has
been proceeded. At ISIR, the FEL lasing[3] in theregion from 32 - 40 [lm was succeeded in 1994 byusing the L-band linac[4J. The estimated maximum-420-RFSampll'·1·i-Sappl1ier 1-'aser

Argou lou Laset[{[IFig. 3 A new picosecond pulse radiolysis
combined with femtosecond laser.

JAERI-Conf 95-021

f\/

3...lr:.1~i:l~.....

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c:::!
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2iI.g 1.!1........
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Horizontal Size (mm)Fig. 5 The space pro tile of slow positronbeam.

Fig. 4 The typical time profile of FEL
monitored at 40 l-tm.

peak power at 40 l-tm was 8.3 MW.
Fig. 4 shows the typical time profile of the FELat 40 l-tm monitored by a fast response tar infrareddetector. The net FEL gain obtained by the raise of
the time profile and the optical cavity loss obtained

avoid the interference with L-band linac.
Fig. 5 shows the space pn>tile of the slow
positron beam. The transport etliciency wasimproved by the optimization of the opet·ation
condition of the S-band linac, the modet·ator, andby the decay after the electron pulse are 58 % andgood
6.2 %, respectively. The results havemagnetic field. The estimated beam intensity ofslow positron beam was 2 x 108 n/s.
The beam quality of the slow positron willimproved by increasing the brightness of the beam.
The de and pulsed slow positron beam and theiragreements with the calculated values based on thetwo-dimensional model.
In order to get more high performance of theFEL, several improvements, such as the a newly
designed electron gun of the Iinac, a variable gap
system of the undulator, and an optimized opticalcavity, will be required. The preparation of theexperimental port fi>r FEL application is underconsideration.
5. Slow Positron Beam
Since the first image of the slow positron beam
produced by the S-band linac was obtained in 1995,
the measurement of numbers of positrons andextension of the slow positron beam line have been
perfi>rmed. [5]The present position of the end of the slow

application will be started in near tutm·e.
references
1) Y. YoshidaHonda et. al., Pro. 20th Linac Meetingin Japan, 4 (1995).
2) Y. Yoshida et al., Nucl. lnstrum. Meth., A327, 41(1993).
3) S. Okuda et al., Nucl. lustrum. Mcth., A358, 248(1995).
4) S. Okuda et al., Nucl. lnstrum. Meth., A358, 244(1995).
5) Y. Honda et. al., Pro. 20th Linac Meeting in Japan,50 (1995).

positron beam line is point A in fig 2, where theperformance of the slow positron beam ismeasured. The end position will be prolonged tothe measurement room located over point B to-421-