Proceedings o f the 21st Linear Accelerator Meeting in Japan(Septem ber 3 0 -October 2J996,Tokyo, Japan)( P 3 0 - 1〕

FEL User’s Facilities for Application Researches at the FELIS. Okuma, E. Oshita, K. Wakita, T. Takii, A. Koga, S. Nishihara, A. Nagai, K. Wakisaka,
H. Tongu， A. Kohayashi, Y. Miyauchi, T. Mitsuyu, S. Kuribayashi， K. Nishi, H. Ohyama,T. Suzuki, E Nishimura， K. Awazu, S. Ogino, M. Yasumoto and T. Tomimasu
Free Electron Laser Research Institute，Inc. (FELI)
2 - 9 - 5 , Tsuda-Yamate, Hirakata, Osaka 5 7 3 -0 1 , Japan

Abstract
Two electron linacs and five FEL facilities were designed and constructed at the FEU from FY1993
to FY1995. Three FEL Facilities 1，2 and 3 achieved losings in Oct. 1994, in Feb. and in Dec. 1995,
respectively. The FEL Facility 3 has broken a world record for the shortest wavelength oscillation using alinac with a thermionic gun up to 0.278 jim on June 6 , 1996. FEL Facilities 4 and 5 were designed andconstructed in 1995 to extend FEL applications to semiconductor devices at far—infrared wavelengths.
Facilities 4 and 5 are in the commissioning stage.
The FEL Facility 1 covering the wavelength from 4.8 to 20 jim is opened for the FEL users for twodays of a week. Basic studies on MIR—FEL applications are earned out in four user’s rooms. Mam
subjects are DNAs and material introduction into the stem cell, ablation of dental substance, annealing ofSiC, hand discontinuity measurement of heterojunctions, optical modulation in semiconductor quantum
wells and isotope separation of carbon and silicon.
The Free Electron Laser ResearchInstitute, Inc. (FELI) was establishedin March 1 9 9 1 . A building (floorspace 4,013m 2) used for developmentso f FEL facilities and FEL applications
was designed and constructed in Tsuda
ScienceHills,
Hirakata CityinNovember 1993.
The main facility consists of anS-band, 1 6 5 -MeV electron linac witha thermionic gun, beam transport (BT)lines and four FEL Facilities 1 , 2 , 3and 4 as shown in F i g . 1 . A compact
facility composed of a 20-M eV linac
with an RF-gun and FEL Facility 5 isalso shown in F i g . 1 . Each FEL
Facility consists of an undulator, anoptical cavity and an optical pipeline.
FEL Facilities 1 , 2 and 3 were
designed in 1993 and 1994 to cover
the wavelengths from 0.23 //m to 2 2 //m of our appointed research target.
However, FEL Facilities 4 and 5 were
designed in 1995 to extend our FEL
applications to semiconductor devices
at far—infrared wavelengths from 2 0 //m to 100 [i in.

F i g . 1 Bird's eye view of FEL Facilities，user's
rooms and beam transport system at the FELIThe spontaneous radiation and FEL beamfrom the main facility are delivered from theoptical cavity on the first floor to the diagnostic

repetition rate o f the micropulse up to 89.25M H z
and the repetition rate o f the macropulse up to20Hz. Another attempt is to use a cavity mirror

room on the third floor with six A l—coatedmirrors.
Their macropulse shape, macropulse
power and spectrum are measured simultaneously
there.

with a larger aperture, for instance, a cavity

Their installations were begun

in January

1994 and finished in March 1996. The main one
was installed in the accelerator room, the klystronroom and the FEL user’s rooms, and the compact
one was installed in the laser instrument room .
The FEL oscillation experiment was begun at
the Facility 1 ( 5 - 2 2 //m ) in August andsucceeded in lasings at 5 - 7 //m in October 1994
[1]. The Facilities 2 ( 1 - 6 / / m) and 3 (0 .23 -1 .2jjiva) achieved lasings at 1.88—3 .1 " m inFebruary [2] and at 0 .3 3 9 -0 .3 5 3 //m and in
December 1995, respectively [3].

mirror with a 2.0-m m 0 aperture for the FEL
Facility 1 and a cavity with a 1.0—mm 必 aperture
for the FEL Facility 2. Although this procedure
reduces a net FEL gain and an FEL macropulse
duration, the average FEL power will increase.
These improvements are expected to increase
average powers up to several W.
The wavelength dependence o f FEL
spectral width
A 1 is also an importantparameter，especially in Si isotope separation bymultiphoton decomposition process.
Experimental data on the wavelength dependenceof A A / A are plotted in Fig 2 [4].

It has been said that no lasing at ultraviolet
wavelengths can be achieved by using an electron
linac with a thermionic gun from the wavelength
limit due to optical diffraction, because of beamemittance growth in the bunching process fromthe thermionic gun to the linac. Therefore, theFELI linac was carefully designed to reduce theemittance growth in the bunching process and theFacility 3 has broken a world record for theshortest wavelength oscillation up to 0.278
asof June 6 ,1 9 9 6 .

Fig. 2The FEL beams are delivered from the opticalcavities to the diagnostics room and four user'srooms through the optical pipes as shown in Fig.
1 . Si nce October 1995, the FEL Facility 1 isopened for FEL users for two days o f a week.

The FEL beam extracted from the narrow
aperture becomes thick and round due to hole
coupling and is delivered to the diagnostics roomand four user’s rooms on the third floor throughThree days of a week are used to grade up theFacilities 2 and 3 and to achieve lasings at theFacilities 4 and 5 in far-infrared range.

Wavelength スR ( p m)

Relations between spectral width and .
wavelength

the optical pipelines as shown in Fig. 3. The
FEL power and spectrum are always monitoredwith a fan-shaped mirror at the diagnostic room.

The FEL micropulse structure depends on theTwo manipulators were installed in Lab. 2.

electron micropulse and macropulse structures,

Each can focus the FEL beam to a 0.1-m m 0

the detuning effect of the optical cavity, and asmall signal gain o f the undulator.

sopt of M1R-FE し beam inside of 2 -m diameter.

In order to increase the average FEL power,
we are trying to increase the present 22.3125M H z

Basic studies on IR-FEL applications
carried out in four user's rooms arc as follows.

( 1 ) DNAs introduction into the stem cell fromwhich all blood cells are derived (in L a b .1)[5].
(2) Ablation and annealing o f dental hard

GaAs heterojunction (in Lab. 3) [8].
(5) Ultrafast all-optical modulation in semicon­
ductor quantum wells (in Lab. 3) [9].
(6) Isotope separation o f carbon and silicon bysubstances (in Lab. 2) [6].
(3) Material introduction into cultured T lympho­
cytes (in Lab. 2) [7].
(4) Band discontinuity measurement of ZnSe/

multiphoton decomposition process (in Lab.
3 )[1 0 ].
(7) Annealing of silicon carbide and amorphoussilicon (in Lab. 4 )[1 1 ].

L A S E R A N N EA LIN G(S iC , etc.)

N Q N -R A D IO A C TIV E

L A S E R A B LA TIO N

M E D IC A L & B IO LO G IC A L

IS O T O P E S E P A R A T IO N(d entine, m e m b ra n e )A P P LICA T IO N SlA JFig. 3 FEL user's facilities at the FELIThe FEL Facility 4 (20- 60 "m ) including a2 .7 -m long hybrid type undulator with electroand permanent-magnets (ス u=9cm, N=30) and a
6 .7 2-m long optical cavity was installed at the33 -M eV beam line of the downstream of theFEL Facility 1 in March 1996. An FEL beam isdelivered frotn the downstream optical cavity tothe user's rooms through the pipeline of theFacility 2. Since the middle of June, we aretrying to pass a well collimated beam through theundulator 4 [12].
The FEL Facility 5 (5 0 -1 0 0 //m ) of thecompact facility, including a 2.24-m longundulator ( フ ..=8cm, N=28) and a 5 .04-m long
optical cavity, was installed at the 20-M eV beamline of the 20—MeV linac with an RF-gun in thelaser instrument room in March 1996. An FEL
beam is delivered from the upstream opticalcavity to the laser experimental room through thepipeline. The operation of compact facility
including final RF ageing was begun in May andthe beam acceleration was started in the middleof June for the legal inspection of our radiation
protection system.

References[ 1 ] A. Kobayashi, et al., Nucl. Instr. Meth., A375
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(1996) 626[5] M. Yasumoto, et al., Extended Abstract of 43rd
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(1996)
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L760[9] T. Mitsuyu, et al., Proc. IEEE Lasers andElectro-Optics Society 1996 Annual Meeting
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User's Workshop (Rome, Aug. 26-28, 1996)[ 1 1 ] H. Ohyama, et al., Jpn. J. Appl. Phys., 35(1996) L683
[12] T. Takii, et al” Presented at FEL ’96 (Rome,Aug. 26-30, 1996)