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

STUDY OF AN ELECTRON BEAM PUMPED AR-XE LASER
S.Okada,T.Hattori, ,Y.Hayashizaki,T.Sugita, K.Yamamoto, and M.Aoke, Research Laboratory for
Nuclear Reactors,Tokyo Institute ofTechnology,Meguro·ku,Tokyo,Japan
H.Tomizawa, JASRI, Mikazuki-cho, Sayo-gun, Hyogo, Japan

Abstract

beam maximum kinetic energy is 200keV, so the energy

The study of electron pumped Ar-Xe laser was started.

loss by bremsstrahlung can be disregarded, and include

The scattering simulation of a laser medium and anrelaticistic effect, it can be presented by the Bethe

electron within the laser tube which impressed theformula. 1>

magnetic field of 0.4T using the Monte Carlo method
was carried out to optimization of laser efficiency. TheT 2 (T + 2)

design and manufacture of lambda type laser tube~m~c'equipment was performed using the simulation result.

!.INTRODUCTION

rSince, as for Ar-Xe laser, high intensity and anefficient laser oscillation are expected in a 1.73 to 3.65 f.lm the near infrared wavelengths. So by the present age,many study has been done with the various pumping
systems, electric discharge, electron beam, electron beam

where N. is the Avogadro number, P is the density, Z issustained discharge, UV-preionized discharge, X-ray

the atomic number, T is the kinetic energy of electron

preionized discharge, and nuclear pumping. In this study,beam, A is the atomic weight, and I is the ionizationin order to aim at optimization of the laser efficiency bypotential,and given by the following formula

electronic beam pumping, the Monte Carlo technique

1 = z~.16 +5s.sz-u9 )was used to carry out the simulation of the multiple

z <!: 13scattering with electron beam and laser medium in laser
tube. Now, design and manufacture of the Lambda type3. ELECTRON ORBIT IN THE

laser tube equipment was carried out using theMAGNETIC FIELD
The electron beam in a laser medium is spreaded bysimulation result, and the experiment was started.

multiple scattering, and excitation of a laser medium

2. ENERGY LOSS OF THE ELECTRON

become uneven spatially. Since the quality of a laser

BEAM IN A LASER MEDIUM

beam deteriorates as a result, it is necessary to control a

The high energy electron beam in laser medium loses

spread by using an external magnetic field. It drifts alongenergy gradually, deposit energy to a composition atomwith a line of magnetic force, an electron receiving

and ionization or excitation by repeating an inelastic

Lorentz force by impressing an external magnetic field,collision. When considering this energy deposit process,and carrying out circular motion in a Larmor radius. If an

stopping power is important. In this study, the electron

external magnetic field is strengthened, since a Larmor-429-The 13th Symposium on Accelerator Science and Technology, Suita, Osakn, Japan, October 2001

radius becomes small, it can control a spread more byscattering. In this study, the magnetic field of 0.4T wasused with the solenoid coil so that an electron beammight be drifted along with axis of a laser tube.
Moreover, the magnetic field of O.lT was used todeflect.(Fig.l)::-.....

L\_l

l1__l_'1.

,}_r - - - - - - - - 4 0 0 _ _ _ _ _ _-1...

deflection coil 0. IT'/.
UHH15.......... (OM)

10i

Dislanolt . . . hUFig2 Deflection coillcm

Fig.l

Layout of laser tube and solenoid coils'/'_j_4.THE MONTE CARLO TECHNIQE
The Monte Carlo technique is the general term of a__'1.

j__l_/

numerical computation method which used the random
number. The details of the Monte Carlo simulation,__'1.
~;.:;:_-·

11105mu"~~..,.the.._. 111M ... (om)carrying out incidence of the electron beam into a
Fig3 Deflection coil 6cm

material is writen out reference 2) and reference 3).Inthis study, we used reference 3) continuous energy loss
type program :type (A).

S.RESULTS
Simulation results of an electron beam 200ke V pentrate
the kapton foil with thickness of 25 11 m, and inject intor

deflection coil to lcm, 6cm, and 12cm and magnetic
field intensity on the main axis is shown in Fig.2, Fig3,and Fig4. Consequently, the length of a deflection coil is' _'1.

_l_laser tube containg Ar latm, changing length of-·./.

£1L:

j_j_1

__'1.

'i1015aH

U~ ............ luflllt . . (.-)

set to 6cm, it turns out that an electron beam spreads
Fig4 Deflection coil12cm

most uniformly within a laser tube.

-430-UThe 13th Symposium on Accelerator Science and Technology, Suita, Osaka, Japan, October 2001

6. CONCLUSION AND FUTURE PLAN

S.EXPERIMENTAL SETUP
The whole equipment setup is shown in FigS. An

As a result of changing the length of a diflection coilelectron gun and a turbo pump are on the mountand calculating, the length of a deflection coil is 6cm, it

insulated with four insulated insulators, and ·the highturns out that an electron beam spreads uniformly within

voltage are applied by the high voltage power supply toa laser tube most. Design and manufacture of equipment

200kV. The electron gun is grided electron gun and thewas carried out based on this simulation result. After

material of cathode is BeO. The electron beam isconducting a test experiment with the electron beam ofaccelerated with a 200kV acceleration tube, andSOke V first as a future schedule using the manufactured

penetrate a circular kapton foil with a diameter of Smm

equipment, the energy of an electron beam is raised tothickness of 2S 11 m. Then the electron beam is deflected

200keV.

4S degrees with a deflection coil, and is injected into alaser medium. The length and the diameter of inner of a

7.REFERENCES

laser tube is 40cm and 34mm, and the vacuum is1)H.A.Bethe : AnnPhys.5,3S2 (1930)

measured with a Baratron. A laser resonator consists of2)R.Shimizu,T.Ikuta,anK.M urata:J .Appl.Phys.43,4233

all the reflective mirrors of a golden coating plane mirror,(1972)and the plane mirror of 99.5% of the reflectance. Laser is3)E.Hujiwara,Y.Kato,S.Ichimura,andR.Shimizu:The

measured by germanium photo-diode.

Review of Laser Engineering.8,S1 (1980)

TJ.IP

entrancegas cleaner)

Baratoronle photodiodeBW'I

output coUPler

FigS Schematic of the experimental setup-431-