Search

Carbon nanotube (CNT)-based field emission X-ray source with the advantage of fast start-up response offers the chance to achieve high-frequency X-ray emission. In this study, a high-frequency random pulse X-ray source of CNT cold cathode combined with a channel electron multiplier (CEM) was built, and its direct current (DC) and pulse emission characteristics were tested. The DC measurement results were used for parameter selection for performing pulse experiments. During the DC test, with the conditions of 2.2 kV CEM bias voltage and 25 kV anode voltage, the anode currents are 141, 250, and 300 μA at grid voltages of 290, 387.6, and 432.2 V, respectively; the corresponding grid field values are 1.45, 1.94, and 2.16 V/μm. During the pulse test, the amplitude–frequency response of the X-ray source reaches 3.58 MHz at 3 dB. The developed pulse X-ray source was introduced into the X-ray communication (XCOM), and the experimental communication rate reached 6 Mbps with the bit-error-rate of 1.1 × 10−3. The developed high-frequency pulse CNT-CEM X-ray source has potential applications in XCOM, high-speed X-ray imaging, and other fields. • Proposed a high-frequency pulse CNT X-ray source combined with channel electron multiplier at low grid voltage. • Direct current and pulse emission characteristics were tested, respectively. • Frequency response of the CNT-CEM X-ray source is 3.58 MHz at 3 dB. • Communication rate reaches up to 6 Mbps with the bit-error-rate of 1.1 × 10−3. [ABSTRACT FROM AUTHOR]

The channel electron multiplier (CEM) current flicker noise was examined for different parameters of its operation. In particular, the dependence of CEM power spectral density function on its output current value has been verified. Also the dependence of the CEM power spectral density function on the input electron energy was investigated. [Copyright &y& Elsevier]

We have investigated channeltron operating in coincidence with silicon surface barrier detector for detection of extreme low energy particles. By use of Po-209 radionuclide and silver backing, a radioactive source was prepared as a fine emitter of released α particles, conversion electrons, recoil Pb-205 ions and knock out silver ions. To avoid parasite coincidence events mainly from channeltron anode RC circuit, we have applied appropriate Faraday screens. After getting proper counting rates, composite spectra were recorded. Based on time-of-flight and secondary electron emission coefficient arguments, particular spectra of mentioned particles were extracted. Final experimental data analysis enabled us to found channeltron efficiency curves for electrons, lead ions and silver ions with low detection thresholds at 40 eV, 4 keV and 1.7 keV, respectively. [Copyright &y& Elsevier]

A compact mono-energetic positron beam system has been constructed at The University of Hong Kong in order to perform positron re-emission measurements, after fast positrons from a radioactive 22Na source moderated by a variety of samples. The positron re-emission measurements are performed at a vacuum of 10−8 Torr. Re-emitted slow positrons are guided by longitudinal magnetic fields provided by three field coils located outside the vacuum tank and are detected by a gamma photon insensitive channel electron multiplier (CEM). The radioactive source, the sample, the focusing grid, the retarding-field energy analyzer (RFA) and the CEM detector were put into a compact assembly having a length of 33 cm and a diameter of 6 cm. Positron re-emission from W(1 1 1), GaN/SiC, Ga/GaN/SiC, 4H and 6H–SiC surfaces have been studied. The moderator conversion efficiencies of these samples are reported. [Copyright &y& Elsevier]