Sub-Nanosecond Detection of Heavy Ions Using Single-Crystal, Natural Type IIa Diamond
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SUB-NANOSECOND DETECTION OF HEAVY IONS USING SINGLE-CRYSTAL, NATURAL TYPE IIA DIAMOND SUNG HAN*, STANLEY G. PRUSSIN*, LAWRENCE S. PAN**, STEPHEN M. LANE**, DON R. KANIA***, RONALD S. WAGNER**** AND CALEB R. EVANS**** *Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720 "**LaserProgram of Lawrence Livermore National Laboratory, L-474, Livermore, CA 94550 ***Crystallume, 125 Constitution Drive, Menlo Park, CA 94025 ****Los Alamos National Laboratory, Los Alamos, NM 87545. Abstract The sub-nanosecond electrical transients induced by 5-MeV He+ and 10-MeV Si3+ ions have been measured in single-crystal, natural type Ila diamonds. The detectors were fabricated into conductivity modulated devices and were incorporated into 50-f4 high bandwidth transmission line structures. The electrical signals were recorded with a system based on a 70 GHz random sampling oscilloscope with the total recording rise time of 18.6 ±:0.6 ps. Signal rise times are less than 70 ps and fall times are less than 200 ps for electric fields in the range 3.8x10 4 - lxl0 5 V/cm. The plasma time appears to play a key role in defining the initial stages of the charge transport because signal rise times are much greater than the recording system rise time, especially with the Si-ion excitation. Furthermore, incomplete charge collection is quite severe even at the highest applied electric fields due to the dominance of carrier trapping/recombination at the defect sites. Introduction In recent years, it has been shown that a solid state detector operating in a mode similar to that of a photoconductor can be used as a fast detector for charged-particles [1] and 14-MeV neutrons [2]. (The term radiation induced conductivity (RIC) is used when a photoconductor detects particles rather than photons.) 14-MeV neutrons deposit energy in solids via nuclear reactions that produce charged-particles. These charged-particles then dissipate their energy in the detector through ionization. Energy deposition in this manner is localized to a small volume in the detector. In order to investigate the physics of charge collection under localized excitation conditions, we have used heavy ions from an external source to excite the detectors. In this
paper, the time-resolved current transient measurements from interactions of individual heavy ions in natural type Ha diamond RIC detectors excited with heavy ion of either 5-MeV He+ or 10-MeV Si3+ are presented.
Experimental arrangement The approach used to measure the response of diamond to single particle excitations centers on the Hypres model PSP750 high-bandwidth random sampling oscilloscope. This is a
70 GHz oscilloscope that uses a built-in superconducting, near dispersion- and loss-free, delay line that enables signal levels as small as 2 mV into 50 f0 to be sampled directly. Because the oscilloscope relies on sampling, many input waveforms are needed to "build" an average output waveform. The experimental apparatus and arrangement are similar to that used by Wagner et al. [3] to meas
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