SPIE Proceedings [SPIE 20th International Congress on High Speed Photography and Photonics - Victoria, BC, Canada (Monday 21 September 1992)] 20th International Congress on High Speed

Repetitive compact flash x-ray generators for soft radiography

Eiichi Sato, Arimitsu Shikoda, Shingo Kimura, Michiaki Sagae and Teiji OizumiDepartment of Physics, Iwate Medical University, Monoka 020, Japan

Kei TakahashiMedical Computer Research Center, Iwate Medical University, Morioka 020, Japan

Yasuomi HayasiElectrical Engineering, Hachinohe National College of Technology, Hachinohe 039-1 1 ,Japan

Tetsuo Shoji and Koro ShishidoDepartment of Applied Physics, Faculty of Engineering, Tohoku Gakuin University, Tagajo 985, Japan

Yoshiharu TamakawaCenter for Radiological Science, Iwate Medical University, Morioka 020, Japan

Torn YanagisawaDepartment of Radiology, Iwate Medical University, Monoka 020, Japan

ABSTRACT

The constructions and the fundamental studies for the repetitive flash x-ray generators designedby Japan Impulse Laboratory in Iwate Medical University are described. These generators areclassified to the following two major types: (1) generators having diodes and (2) generators havingtriodes. In order to generate high-voltage impulses, we employed following transmission lines (pulsers):(a) high-voltage-inversion type with a maximum output voltage V0m of about 80 kV (b) high-voltage-inversion type having a coaxial cable (V0m=130 kV), (c) two-stage Marx pulser (V0m=150 kV), (d) two-cable-type Blumlein (V0m=l20 kV), (e) modified Blumlein (V0m=120 kV), (f) fundamental transmissionline for triode (V0m=100 kV), and (g) transmission line for an enclosed triode (V0m=lOO kV). Forobtaining high-dose-rate flash x rays, four kinds of diodes in conjunction with high-voltage lines (pulsers)[(a)—(e)]were employed. In contrast, the flash x-ray generators having two kinds of triodes were usefulfor generating stable and low-dose-rate x rays without considering generation of plasma x rays; low-dose-rate x rays decrease radiation damages of biological objects. Using the high-voltage pulsers withdiodes, although the x-ray intensity roughly increased in proportion to the electrostatic energies in thecondenser, the pulse widths were less than 200 ns, and the maximum repetition rate was about 50 Hzwhen a simple gas-gap switch was employed. In contrast, by using the triode lines, the dose rate waseasily controlled, and the x-ray duration was increased to a value of more than I j.is. When a triode linein conjunction with a glass-enclosed triode was employed, the stable repetitive x rays of sub-kilohertzwere obtained. Using these generators, we succeeded in performing high-speed radiography as follows:(a) delayed radiography; (b) multiple-shot radiography; and (c) cineradiography.

1. INTRODUCTION

Recently, high-voltage pulse techniques have been effectively applied in order to produce electronbeams,12 laser beams,34 and flash x rays.56 The flash x-ray generators are usually employed for

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performing high-speed radiography for technical and military applications, and various kinds of generatorsfrom very soft to hard types corresponding to the radiographic objectives have been developed bynumerous 71

In order to perform high-speed soft radiography with maximum photon energies of less than 200 key,although many types of generators have been developed, a new type of long-life and low-jitter generatordeveloped by D. Ebeling and F. Frungel11 of Impulse Technology (Germany) is quite famous in order toperform cineradiography with a maximum repetition rate of 20 kHz. In addition, a repetitive kilohertz-range soft generators having an extreme hot-cathode radiation tube having variable durations of less than1 ms1213 is useful for performing high-speed radiography in a microsecond range.

For the high-voltage transmission lines with maximum output voltage of less than 200 kV, althoughmany kinds of transmission lines (e.g., multiple-stage Marx,14-16 Blumlein,1718 high-voltage-inversiontype,192° and tesla-transformer21) used for driving cold-cathode radiation tubes can be considered, compacthigh-voltage pulsers are desired in order to drive easier and to design low-cost generators. In technical andbiomedical fields, single or dual head type generators with high-time resolutions are also useful forfundamental studies.

In this paper, we reported the constructions, the radiographic characteristics, and the applications ofvarious kinds of repetitive flash x-ray generators having cold-cathode radiation tubes designed byJapan Impulse Laboratory in Iwate Medical University.

2. GENERATORS

2. 1 . High-voltage transmission lines

The repetitive flash x-ray generators described in this paper employed energy-storage condensers withcapacities of more than 0. 1 .tF in order to increase repetition rates of flash x rays [see Fig. 1(a)]. Thesecondensers were charged to high voltages corresponding to the kind of pulser and charged the high-voltage condensers in pulsers through resistors. The triode can be also driven by various kinds of high-voltage pulsers as in Fig. 1(b). These pulsers were driven by a repetitive trigger pulser achieved with afree-air gap switch. In order to perform single-shot radiography with a high-time resolution, a Krytronpulser (KP-B) is employed.

Figure 2 shows the high-voltage transmission lines designed by the authors. In order to produce high-voltage impulses of about —itimes the charged voltage, a polarity-inversion-type transmission line22 (pulser)[type (a)] was employed [see Fig. 2(a)]. Using this pulser, the high-voltage condenser is charged toanegative voltage, and the output voltages V0(t) from the pulser is roughly given by the followingequation:

Fig. 1 Block diagrams of the flash x-ray generators having high-voltage pulsers: (a) for driving diodes; (b)for driving triodes.

SPIE Vol. 1801 High-Speed Photography and Photonics (1992)1629

(a) (b)


-T

Fig. 2 Circuit diagrams of the high-voltage transmission lines: (a) polarity-inversion type; (b) polarity-inversion type with a coaxial cable; (c) two-stage Marx type; (d) two-cable Blumlein type; (e)modified-Blumlein type; (0 fundamental line for triodes; (g) transmission line for a glass-enclosed triode.

630 ISPIE Vol. 1801 High-Speed Photography and Photonics (1992)

POWER SUPPLY POWER SUPPLY

(a)(b)

OUTPUT POWER SUPPLY

(e)

ANODE

TRIGGER

(f)POWER SUPPLY

pAAA

TRIGGER

°Ill(g)


II /\/

Fig. 3 Structures of the flash x-ray tubes: (a) needle-ring diode; (b) plate-plate diode; (c) needle-diskdiode (d) disk-pipe diode; (e) fundamental triode; (f) glass-enclosed triode.


II \ (c)I

I

A:ANODE ELECTRODEC:CATFIODE ELECTRODET:TRJGGER ELECTRODE

/ T (e) (f)


V(t)=—AV[exp(—tIRC)—(CoLo)°5exp(—ait)sin { bi t+tan' (bi/ai ) }/bi],

ai=Ro/2Lo, bi={(4Lo/Co)—Ro }°5aL2irf=2ir[T, (1)

where Vc jS the initial charged voltage of the condenser, C is the capacity, Co is the stray capacity, R is theresistance, Ro is the resistance of the high-voltage pulser, Lo is the total inductance of the pulser, f isthe oscillation frequency, T is the oscillation period, and A ( 0.9) is the attenuation factor due to theenergy loss and other factors.

Next, in order to obtain high-voltage impulses, a polarity-inversion-type pulser in conjunction with acoaxial cable [type (b)]23 was employed [see Fig. 2(b)]. In this generator, V(t) is well approximated by:

Vo(t)AVc[exp(—t/RC)—(CcLc)°5exp(—t)sin { b2t+tfl1 (b2/a)}/b2],a=Rof2L, b={(4L/C)—Ro2}°5/2L, (2)

where C is the capacity of a coaxial cable and L is the cable inductance. In this case, A is roughly givenby:

A1—2C/C. (3)

Using this high-voltage pulser, the duration of the first quarter cycle had a short time due to the high-voltage reflection by a cable.

Although the multiple-stage Marx (M stages) generators [type (c)] are employed for producing higherimpulse voltages of M times the charged voltage, we employed two stages as in Fig. 2 (c) in thisexperiment. For this pulser, V(t) is written by:

V(t)=2AV[exp(—2t/RC' )—(CoLo)°5exp(—ait)sin{ bi t+tan1 (bi/ai) }/bi], (4)

where ' is the capacity of each condenser and A 0.9.Although the Blumlein circuit [type (d)] is a kind of line pulser which produce high-voltage impulses

of —1 times the charged voltage when a matching resistor is employed, this pulser can produce impulsesof about —2 times the charged voltages without using a matching resistor.24 As shown in Fig. 2(d), thetwo cable condensers were charged to negative voltages, and V0(t) is approximated by:

V0(t)=—AV[exp(—t/RC)--(CcLc)°5exp(—a2t)sin( b2t+tarr' (b2/a.2)}/b2]. (5)

Without considering the energy loss, this pulser can produce rectangular pulses, the outputs displaydamped oscillations.16'17 But the duration of the first quarter cycle has a comparatively short time.

Figure 2(e) shows a modified Blumlein circuit with two condensers [type (e)]. This pulser isemployed in order to control the high-voltage rise time by controlling the inductance of a coil. Using thishigh-voltage pulser, V0(t) is given by:

V0(t)=—AV[exp(--t/R C ")+(C 'L)°5exp(a3t)sin ( bt-i-tarr1 (b3/w) }/b3],

a3=Ro/2L, bi={(4L/C D—Ro2}°512L, L=Lo+L0, (6)

632 / SPIE Vol. 1801 High-Speed Photography and Photonics (1992)


where L is the coil inductance. The fundamental line for triodes and the line for a glass-enclosed triodeare shown in Figs. 2(f) and (g) [(f) and (g) types], respectively. Using these lines, the maximum tubevoltages were equivalent to the charged voltages, and the voltage during main discharge primarilyvaried according to changes in the discharge impedance of the x-ray tube.

2.2. Flash x-ray tubes

The schematic drawings of the flash x-ray tubes are illustrated in Fig. 3. The tubes except for type(d) employed tungsten anodes in order to increase the x-ray intensity of the bremsstrahlung spectra andto increase the anode durability.

Figure 3(a) shows a diode which has a rod-shaped anode and a ring-shaped surface-discharge cathodemade of ferrite [type (a)]. Using this cathode, stable vacuum discharges were generated even when a largespace between the anode and cathode electrodes was employed, and a needle-shaped anode can beemployed. In contrast, when a surface-discharge diode with a set of plate-shaped electrodes wereemployed [see Fig. 3(b)],25 the anode durability became to high. In addition, the maximum tubevoltage was primarily determined by the A-C space, and the x-ray intensity distribution inside of theradiation space was quite uniform, when a disk-shaped graphite cathode [type (c)] was employed [seeFig. 3(c)].26 In order to apply the flash x-ray generator to the ionizing source for gaseous matter, a set ofa thin metal anode and a pipe-shaped cathode [type (d)] is useful [see Fig. 3(d)].27

The two-types of triodes [(e) and (f) types] in order to decrease the dose-rate of flash x rays forbiomedical radiography are shown in Figs. 3(e) and (f); radiation damages are caused by high-dose rate xrays. Since the A-C space had large values compared to those of diodes, the discharge impedances alsohad larger values, and the dose rate could be controlled by the A-C space.

The sizes of the x-ray spot of types (a), (c), (d) and (e) tubes are nearly equivalent to the anodediameters, the size of type (b) tube has a value of WaxWbsinø [cf. Fig. 3(b)].

3. PRINCIPLES OF OPERATION

3. 1 . Design of diode lines

Compared to the x-ray intensities of the characteristic x rays, because the bremsstrahlung intensitieshave larger values, the flash radiography is primarily performed by thebremsstrahlung spectra.The flash x-ray intensity is determined by both the tube voltage and current which display dampedoscillation. Thus the most flash x rays are produced at the first quarter cycle of the damped oscillations.

Although the tube voltage vary according to the kind of pulser or the tube, since the peak voltage V isprimarily determined by the breakdown time Tb(S) (as a function of the A-C space S) and V, V isrepresented by:

Vp—Vr{ Tb(S), V}, (7)

Although V increases according to increases in S and V, V is almost controlled by S when the effectof V is neglected. In this case, the tube current J, (at a V) and V are represented by:

Jp—Vop/(Zo+Z)_(Vop—Vp)Zo, (8)VV0Z/(Zo+Z), (9)

SPIE Vol. 1801 High-Speed Photography and Photonics(1992)/633


where Vop is the pulser output at a V, Z is the tube impedance, and Zo is the impedance of thetransmission line except for the tube impedance. Thus the x-ray intensity I, of the bremsstrahlungspectra at a V on the radiation gap is given by the following equation:

(10)

where Ki is some factor, Ki' =Ki/Zo, anda 2. Using this Eq. (10), because I is determined by V0 andV, I can be controlled by varying S at a constant V. Next, the impedance ratio P is written by:

P=Z/Zo=Vp/(Vo,,—Vp). (11)

Thus 'p 5 represented as two functions of V0 and P:

I=Ki ' V0'1 (Pa/(p+1 )a+1 } . (12)

We assume that P has a constant value, I,, increases in proportion to the third power of V. In contrast, 4maximizes at P=2 when a constant V is employed. For performing high-speed radiography, since theoptimum intensity corresponding to desired quality is necessary, both V and S should be selectedcorresponding to radiographic objectives. In addition, 4 roughly maximizes when S is increased.

3.2. Design of triode lines

The triode-type flash x-ray tube was primarily designed in order to demand the electrostatic energies Eoin the condenser at the anode electrode by increasing the discharge impedance of the tube; the tubeimpedance roughly increases according to increases in the A-C space. In this condition, Eo is approximatedby the following equation:

E0 =CV /2I J(t)V(t)dt= constant,Jo (13)

where Ct is the total capacity during main discharge, Vm is the maximum output voltage of the pulser, J(t)is the tube current, and V(t) is the tube voltage. When a two-stage Marx type generator is employed[cf. Fig. 2(c) and Eq. (4)], Ct and Vm have values of C 72 and 2V, respectively. In this case, J(t) isrepresented by:

J(t)=—C1 dV(t)/dt. (14)

Next, the total x-ray intensity Jo of the bremsstrahlung spectra is written by:

J0 =K2j J(t)V(t)adt,(15)

where D is the duration of the flash x rays, a is a constant ( 2), and K2 is some factor. Equations (13)



and (14) substituted in Eq. (15) give:

0

10=K2 V(tdV(t)=K2CV1=COflstant,vc (16)

where K2' =K2/(a+1). Thus Jo increases in proportion to Cr and (a+1) power of Vrn. In this case, Jomaximizes, and stable x-ray intensity are produced at a constant Vm

4. RADIOGRAPHIC CHARACTERISTICS

In this paper, because there were many combinations between transmission lines and tubes, wereported interesting characteristics concerning flash x-ray generation.

4. 1 . Characteristics using diode lines

Figure 4 shows typical high-voltage outputs produced from type (c), (d) and (e) pulsers. When the type(c) (Marx type) pulser with a C =O.85 nF was employed, high-voltage impulses with maximum voltagesof about 1.8 times the charged voltages were obtained [see Fig. 4(a)]. In the case of employing the type(d) pulser with a C of 1 .0 nF, the maximum output voltages of —1 .8 times the charged voltages wereobtained [see Fig. 4(b)]. In contrast, the rise times had larger values using the type (e) pulser because acoil of 3.3 iH for controlling the rise time was employed [see Fig. 4(c)]. These results correspondedqualitatively to Eqs. (4), (5) and (6).

The maximum tube voltage was primarily determined by the rise time of the pulser output and the A-Cspace (see Fig. 5). When a type (c) pulser (C '=0.85 nF) in conjunction with a type (a) tube wasemployed, the maximum tube voltage roughly increased in proportion to the charged voltage [see Fig.5(a)]. In contrast, the maximum voltage (—1 times the maximum cathode voltage) seldom varied accordingto increases in the charged voltage, when a type (e) pulser (negative charge, C '=0.85 nF) with a type (d)tube was employed [see Fig. 5(b)]. Using this pulser, the maximum tube current was easily controlledby varying the charged voltage at a constant maximum tube voltage. The results concerning the tubevoltage corresponded to Eq. (7).

Figure 6 shows the typical flash x-ray outputs achieved with a type (c) pulser in conjunction with atype (b) tube. The single output was measured by a combination of a toluene scintillator and aphotomultiplier. The pulse height roughly increased according to increases in the charged voltage sinceboth the maximum voltage and the tube current increased at a constant A-C space [see Fig. 6(a)]. Next,the repetitive x-ray outputs were detected by using a combination of a screen, a photomultiplier, andan integrator in order to increase the signal width. Since the time interval between two pulses wasquite long compared to the duration of flash x rays, the repetitive output could not be easily recordedby using a digital storage scope. In this experiment, the maximum repetition rate was 50 Hz, andcomparatively stable repetitive x rays were obtained [see Fig. 6(b)].

4.2. Characteristics using triode lines

Figure 7 shows the tube voltages produced from a repetitive flash x-ray generator which consists of atype (c) pulser and a type (e) tube. The maximum tube voltages were nearly equivalent to the outputvoltages from a pulser and did not display damped oscillations. In this case, since the electrostatic energies



0

0

Cx

100 ns/DIV.100 ns/DIV.

(a) (b) (c)

Fig. 4 Typical high-voltage outputs: (a) from a type [ci pulser; (b) from a type [d] pulser; (c) from a type[ci pulser.

ANODE-CATHODE SPACE=O.75 mmVc: CHARGED VOLTAGE

ANODE-CAThODE SPACE= 9iwnVc: CHARGED VOLTAGE

100 ns/DIV.

(a)

lOOns/DIY.

(b)

ANODE-CATHODE SPACE=3.O mmVc: CHARGED VOLTAGE

Fig. 5 Tube voltages according to changes in the changed voltage: (a) using a type [c] pulser and a type [a]tube; (b) using a type [e] pulser and a type [d] tube.

A01ODE:CATRODESPACE3Q mmCHARGED VOLTAGE=60 kVF: REPETITION RATE

0

kF=25HZ \__________

100 os/DIV. 10 ms/DIV.

(a) (b)

Fig. 6 X-ray outputs from a flash x-ray generator which consists of a type [c] pulser and a type [b] tube:(a) single outputs according to changes in the charged voltage; (b) repetitive outputs.



in the condenser were effectively demand at the anode, the maximized and stable x-ray intensities wereproduced. In addition, when a transmission line of type (g) in conjunction with a glass-enclosed cold-cathode triode (see Fig. 8) of a type (f) was employed, repetitive flash x rays of sub-kilohertz can beeasily generated (see Fig. 9).

5.1. Single-shot radiography

5. FLASH RADIOGRAPHY

Fig. 7 Charged voltage dependence of thetube voltage using a triode of type [e] inconjunction with a type (c) pulser.

Fig. 8 Schematic drawing of a glass-enclosedcold-cathode triode.


The single shot radiography was performed by using a combination of a type (b) pulser (C=4.8nF) and a type (a) tube. In this radiography, a Krytron pulser for triggering a high-voltage pulser, alaser timing switch,28 a delayed trigger device, and a CR system29 were employed. Figure 10 showsthe blowup of sands from a brass tube caused by an explosion of a fire cracker. The radiographicconditions are as follows: a condenser charged voltage (Va) of —75 kV and a distance between theimaging plate and the x-ray source (I-X distance) of 1.0 m. The complete stoppage of grains of sands areobserved.

Vc CHARGED VOLTAGE

TARGET

0

GLASS

SOOns/DIV.

TRIGGERELECTRODE

GRAPFIITE

F: REPETITION RATECHARGED VOLTAGE=5O kV

CATHODE TRIGGER

1 ms/DIV.

Fig. 9 Repetitive output signals of x rays.


Fig. 10 Radiograph of the blowup of sands froma brass tube achieved with a type [b] pulser anda type [a] tube with a V of —75 kV and an I-Xdistance of 1.0 m.

Fig. 11 Delayed radiographs of a breaking glass platefrom a collision of a plastic bullet by a combination ofa type [ci pulser and a type [c] tube with a V of 60 kV,an LX distance of 0.5 m, and a time interval between twoframes of 0.2 ms.

5.2. Delayed radiography

Figure 1 1 shows the delayed radiographs of a breaking glass plate from a collision with a plastic bulletachieved with a combination of a type (c) pulser (C '=0.85 nF) and a type (c) tube using a laser timingswitch with a V of 60 kV, an I-X distance of 0.5 m, and a time interval between two frames of 0.2 ms.Four stages in the breaking of the glass are clearly visible.

638 / SPIE Vol. 1801 High-Speed Photography and Photonics (1992)

Fig. 12 Multiple-shot radiograph of a swinging coinby using a type [c] pulser and a type [b] tube with aV of 60 kV, an I-X distance of 0.8 m, and a repetitiorate of 25 Hz.


5.3. Multiple-shot radiography

A multiple-shot radiograph of a swinging coin with a hole using a flash x-ray generator having a type(c) pulser and a type (b) tube is shown in Fig. 12. The radiographic conditions are as follows: a V of 60kV, an I-X distance of 0.8 m, and a repetition rate of 25 Hz. The accelerating and revolvingmovements of a coin are clearly visible.

5.4. Cineradiography

In order to perform cineradiography using an image intensifier (II) tube, a low-noise type repetitivegenerator is desired (see Fig. 13). In this experiment, a sub-kilohertz combination as in Fig. 9 wasemployed. Using a home-video system, although the maximum frame speed was 30 Hz (fps), themovement of a pendulum are observed. The radiographic conditions are as follows: a V of 60 kV and adistance between the II tube and the x-ray source of 0.8 m.

Fig. 13 Cineradiography of a metronome (ink-jet printer image) by a combination of a type [g]transmission line and a type [fj tube with a V of 60 kV, a distance between the II tube and the x-ray sourceof 0.8 m, and a repetition rate of 30 Hz.



6. DISCUSSION

In the field of high-speed radiography, although many kinds of high-voltage pulsers and the flash x-ray tubes have been developed, the fundamental studies concerning the high-voltage pulse techniqueand the flash x-ray generation are quite essential in order to create a new type of flash x-ray generator.

When a flash x-ray generator having a diode was employed, we obtained a maximum repetition rate of50 Hz. But the rate can be increased by improving a repetitive trigger pulser for driving the high-voltagepulser. Compared to a famous flash x-ray generator having a cold-cathode triode with a maximumrepetition rate of 20 kHz designed by Impulse Technology, a generator having a glass-enclosed cold-cathode triode designed by the authors produced lower-rate x-ray pulses of sub-kHz. But the rate can beeasily increased up to 1 kHz by decreasing the condenser capacity of the transmission line and byimproving the circuit for triggering.

The two materials of graphite and ferrite are useful in order to make cathode electrodes of the flash x-ray tube. When a graphite cathode with a large quantity of clumps30 is employed, although stable vacuumdischarges are generated, the maximum tube voltage slightly increased according to increases in the shotnumber of the flash x rays. In view of this situation, the surface-discharge cathode made from a ferriteplate is quite useful for producing stable tube voltages. Compared to the multiple-needle-type cathodeelectrode, the ferrite cathode has many protruding portions equivalent to needles, so that the stable fieldemission currents for facilitating the main discharging may be flowed. In addition, because the A-Cspace can be increased, the average tube voltage increased, and the maximum tube current decreased.

In order to perform cineradiography using an II tube in conjunction with a high-speed camera, a low-noise-type repetitive generator is desired, since the noise interferes with the image construction of the IItube or the television (TV) system. Although the x-ray intensity (dose) rate is roughly proportional tothe change rate of the tube current dJ/dt, dJ/dt should be reduced for decreasing noises. In view of thissituation, the experimental results using a triode in conjunction with a high-voltage transmission lineshowed possibilities for designing a low-noise (low-dose-rate) generator for x-ray TV system.

7. ACKNOWLEDGMENTS

The authors wish to thank Professor R. Germer of F. H. Telekom in Berlin for helpful advice in thisresearch. This work was supported by Grants-in Aid for Scientific Research from the Iwate MedicalUniversity-Keiryokai Research Foundation, the Private School Promotion Foundation, and theMinistry of Education and Culture in Japan.

8. REFERENCES

1 . D.K. Kania and L.A. Jones, "Observation of an electron beam in an annular gas-puff pinchplasmadevice," Phys. Rev. Leu., 5 3, pp.166-169, 1984.

2. H. Matsuzawa, 0. Ohmori, H. Yamazaki, J. Ueno, A. Furumizu, A. Saito, T. Takahashi andT.Akitsu, "High-Tc superconducting lenses for relativistic electron beams," J. Appi. Phys., 65, pp. 2596-2602, 1989.

3. K. Miyazaki, Y. Toda, T. Hasama and T. Sato, "Efficient and compact discharge XeC1 laser withautomatic UV preionization," Rev. Sci. Instrum., 5 6, pp. 201-204, 1985.

4. R.S.Taylor, "Preionization and discharge stability study of long optical pulse duration UV-preionized

640/SPIE Vol. 1801 High-Speed Photography and Photonics (1992)


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22. S. Kimura, E. Sato, M. Sagae, A. Shikoda, T. Oizumi, Y. Hayasi, Y. Ohta, Y. Tamakawa andT. Yanagisawa, "Generation of flash-ultraviolet rays from a surface-discharge glass substrate," SPIE,173 7, 1 992. to be published.

23. E. Sato, A. Shikoda, M. Sagae, T. Oizumi, Y. Tamakawa, T. Yanagisawa and K. Takayama,Rev. Sci. Instrum., in preparation.

24. K. Kondo, A. Sawaoka and S. Saito, "Flash x-ray diffraction study during shock-compression," Proc. 13th mt. Congr. High Speed Photography and Photonics, Tokyo, pp.377-380,1978.

25. A. Shikoda, E. Sato, S. Kimura, T. Oizumi, Y. Tamakawa and T. Yanagisawa, "High-durabilitysurface-discharge flash x-ray tube driven by a two-stage Marx pulser," SPIE, 173 7, 1 992. to bepublished.

26. E. Sato, S. Kimura, H. Isobe, K. Takahashi, Y. Tamakawa and T. Yanagisawa, "Disk-cathodeflash x-ray tube driven by a repetitive type of Blumlein pulser," SPIE, 1358, pp.146-153, 1990.

27. A. Shikoda, E. Sato, S. Kimura, H. Isobe, K. Takahashi, Y. Tamakawa and T. Yanagisawa,"Repetitive flash x-ray generator as an energy transfer source utilizing a compact-glass body diode,"SPIE, 1358, pp.154-161, 1990.

28. H. Isobe. E. Sato, S. Kawasaki, K. Sasaki, T. Akitsu, S. Oikawa, Y. Tamakawa, T.Yanagisawa, J. Takahashi, Y. Yasuda, H. Arima and J. Obara, "A flash radiographic system forbiomedical Use," SPIE, 1032, pp.242-249, 1988.

29. M. Sonoda, M. Takano, J. Miyahara and H. Kato, "Computed radiography utilizing scanninglaser stimulated luminescence," Radiology, 148, pp. 833-838, 1983

30. B. Juttner, "Vacuum breakdown," Nude. Instrum. Meth. Phys. Res., A268, pp. 390-396,1988.



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SPIE Proceedings [SPIE 20th International Congress on High Speed Photography and Photonics - Victoria, BC, Canada (Monday 21 September 1992)] 20th International Congress on High Speed