photoconductive switching stacked blumlein pulsers
Post on 05-Feb-2022
7 Views
Preview:
TRANSCRIPT
Pulsed Electrical Power
at
100 Megawatt Levels
TABLE OF CONTENTS
HISTORY and STATUS [Not Installed]
CONCEPT [Not Installed]
Excerpt from ARTICLE #1 presented at the Technical Conference AMEREM '96 held in
Albuquerque, NM June 12-15, 1996.
BibliographyReturn to MAIN Table of Contents
PHOTOCONDUCTIVE SWITCHING
of
STACKED BLUMLEIN PULSERS
In recent years photoconductive semiconductor switches have gained much attention and have
become competitors to the conventional high-power switches for certain applications. These new
devices operate jitter-free with optical isolation of the trigger. They have switching speeds which
either match or greatly exceed the risetimes of the the optical pulses triggering them. Suchphotoconductive switches are described as LINEAR or AVALANCHE, respectively.
The application of linear switches has been limited by the relatively high optical power required to
obtain their closure. In the avalanche type switches, the electron-hole pair produced by each
trigger photon is multiplied through an avalanche process, thus reducing the optical energy levels
necessary for initiation of the switch closure. The nonlinearities of the multiplication accelerates
the pace of commutation so that the switch closes faster than the trigger power rises. It is
interesting to note that Blumleins may be the most appropriate pulse-forming line for use with
photoconductive switches. They provide faster output pulse risetimes and reduce the percentage of
stored energy deposited in the switch.
Recent efforts in the Center for Quantum Electronics at UTD have been directed toward
commuting Blumlein pulsers with GaAs switches in the avalanche mode. Adaptation of the design
and fast charging schemes haveenabled the stacked Blumleins to
produce extremely high-power
nanosecond pulses of electrical
energy with sub-nanosecond
risetimes.
A 2-line stacked Blumlein pulser
shown in the photograph was
designed and constructed for
commutation by photoconductive
switches. A low-profile switching
assembly was constructed to
distribute the switching current toeach of the two Blumleins with line
impedances of about 100 ohms eachand line lengths of 15 cm.
During operation, the pulser was resonantly pulse charged using the charging circuit seen in the
figure to voltages in the range of 30-60 kV and repetition rates of 1 to 10 Hz.
The Charging Pulse Compression (CPC) moduleshown in detail in the figure was resonantly charged
by the slower pulse charge supply after which itsconventional thyratron was triggered to generateshorter charging waveforms for the main stacked
Blumlein pulser. About 80 nsec. later, when the main pulser was fully charged, the laser systemproduced a short burst of photons for commutation of the GaAs switch in the avalanche mode
causing a rapid discharge of the Blumleins. In this way output pulses were produced with very fastrisetimes and peak powers approaching 100 Megawatts.
Typical output waveforms obtained from this pulser
using either a Nd:YAG laser or a low-power laserdiode are seen in the figure reproducing typical data.
These measurements were obtained using an SCD5000 oscilloscope capable of recording single
electrical transients with risetimes of under 100 psec.The particular data shown corresponded to thelaunch of a pulse carrying 70 Megawatts peak power
from the system in the photograph that is as small as hand luggage.
These results prove that with small photoconductive switches,stacked Blumleins can provide nanosecond electrical pulses atpowers approaching 100 Megawatts with risetimes faster than300 picoseconds.
References
C.B. Collins, F. Davanloo and T.S. Bowen, Rev. Sci. Instrum. 57,863 (1986).
F. Davanloo, T.S. Bowen and C.B. Collins, Rev. Sci. Instrum. 58,2103 (1987).F. Davanloo, J.J. Coogan, T.S. Bowen, R.K. Krause and C.B. Collins, Rev. Sci. Instrum.
59,2260 (1988).F. Davanloo, J.J. Coogan, R.K. Krause and C.B. Collins, Nucl. Instrum. Methods,
B40/41,912 (1989).J.J. Coogan, F. Davanloo and C.B. Collins, Rev. Sci. Instrum. 61,1448 (1990).C. Cachoncinlle, J.M. Pouvesle, F. Davanloo, J.J. Coogan and C.B. Collins, J. Phys. D: Appl.
Phys. 23,984 (1990).F. Davanloo, J.J. Coogan, R.K, Krause, J.D. Bhawalkar and C.B. Collins, Nucl. Instrum.
Methods, B56/57,1068 (1991).F. Davanloo, R.K. Krause, J.D. Bhawalkar and C.B. Collins in Proceedings of the 8th
International Pulsed Power Conference, pp 971-974 (1991).F. Davanloo, J.D. Bhawalkar, C.B. Collins, F.J. Agee and L.E. Kingsley in Conference
Record of the 1992 Twentieth Power Modulator Symposium, pp 364-367 (1992).J.D. Bhawalkar, F. Davanloo, C.B. Collins, F.J. Agee and L.E. Kingsley in Proceedings of
the International Conference on Lasers '92, pp 360-364 (1992).J.D. Bhawalkar, F. Davanloo, C.B. Collins, F.J. Agee and L.E. Kingsley in Proceedings ofthe 9th International Pulsed Power Conference, pp 857-860 (1993).
J.D. Bhawalkar, D.L. Borovina, F. Davanloo, C.B. Collins, F.J. Agee and L.E. Kingsley in
Proceedings of the International Conference on Lasers '93, pp 712-717 (1993).F. Davanloo, D.L. Borovina, J.D. Bhawalkar, C.B. Collins, F.J. Agee and L.E. Kingsley in
Conference Record of the 1994 Twenty- first Power Modulator Symposim, pp 201-205
(1994).
D.L. Borovina, F. Davanloo, C.B. Collins, F.J. Agee and L.E. Kingsley in Proceedings of theInternational Conference on Lasers '94 (in press).
F. Davanloo, D.L. Borovina, C.B. Collins, F.J. Agee and L.E. Kingsley in Nucl. Instrum.
Methods, B99, 1995, pp 713-716.
Return to Table of Contents
top related