Particle Detection Applications Research Articles

A new method for detection of alpha particles in 1 mm thick polycarbonate detectors using 50 Hz – HV ECE method

Recent studies in our laboratory have proved that electrochemical etching (ECE) of polycarbonate track detectors (PCTD) under 50 Hz – high voltage (HV) field conditions has potentials for time-integrated heavy charged particle detection and dosimetry applications. The rationale in the study is the ECE process of alpha particle tracks in 1 mm thick PCTDs by a 50 Hz – HV generator at optimized ECE conditions. Tracks of 3.2 MeV alpha particles from a collimated beam of an 241Am source degraded in air and background tracks were registered. The effects of HV and ECE duration on alpha track registration efficiency and track diameters were studied for 3 sets of 50 Hz – 4, 5 and 6 kV field conditions in a PEW solution (potassium hydroxide, ethanol and water) at 26 °C. The optimized ECE conditions obtained at this stage of development for 1 mm thick PCTDs are 50 Hz – 4 kV in PEW solution at 26 °C for 10 h. Alpha track registration efficiency at 3.2 MeV is about 30% with 37 ± 6 μm mean track diameter. The mean background track density at the above stated optimized conditions is about 571 ± 16 tracks.cm−2 with a mean diameter of 65 ± 5 μm. All tracks are observable by the unaided eyes. The mean background track diameter is near two times larger than that of alpha particle tracks at the optimum conditions applied; they are easily distinguished against each other. This high background track density while at this stage of development seems a drawback for low dose and low fluence particle applications, it has minimal effects on high fluence ion detection applications. The simple 50 Hz – HV generator used proved to be convenient for efficient alpha track amplifications. Studies are underway for improvement of the method in particular for reducing background track density.

Controlling the electric field enhancement factor of photonic nanojets by using the magneto-optical effect

In recent years, many researchers have studied photonic nanojets. These nanojets are created when an incident plane wave is focused into a narrow and high intensity emerging optical beam leaving a micro-object (e.g. microcylinder). These narrow beams may find applications in particle imaging and detection, optical sensors, enhanced Raman scattering, and particle manipulation. They also allow the projection of a particle to the far-field where it can be easily visualized. In this paper, it is shown that the electric field enhancement factor can be dynamically controlled by the application of an external intense magnetic flux density.

Latchup Topology for Pixel Readout Using Commercial Transistors

The stimulated ignition of latchup effects caused by external radiation has till now proved to be a hidden hazard. However this paper presents the effect in a new light-as a new approach for detecting particles by means of a solid-state device susceptible to latchup effects. This device can also be used as a circuit for reading a sensor's signal by leaving off-circuit sensing capabilities. Given that MOS transistors are widely used in microelectronics devices and sensors, the latchup-based cell is proposed as a new structure for future applications in particle detection, in the amplification of sensor signals and also in radiation monitoring.

A 4-$\mu\hbox{W}$ CMOS Front End for Particle Detection Applications

A complete low-power front end for particle detection applications is presented. The front end integrates a charge-sensitive amplifier with a novel adaptive biasing scheme that allows the dc bias currents to be scaled below conventional limits. A downstream peak detector circuit captures the peak value for each detection event, which is then fed to an integrated analog-to-digital converter (ADC). The event-driven ADC is shut off in between detection events to further reduce power consumption. The circuit has been fabricated using a 0.18- μm CMOS technology, with a power consumption ranging between 4 and 20 μW, depending on the particle detection rate. This low-power operation facilitates the development of compact long-life battery-powered remote particle sensors.

Feasibility study of a latchup-based particle detector exploiting commercial CMOS technologies

The stimulated ignition of latchup effects caused by external radiation has so far proved to be a hidden hazard. Here this effect is described as a novel approach to detect particles by means of a solid-state device susceptible to latchup effects. In addition, the device can also be used as a circuit for reading sensors devices, leaving the capability of sensing to external sensors. The paper first describes the state-of-the-art of the project and its development over the latest years, then the present and future studies are proposed. An elementary cell composed of two transistors connected in a thyristor structure is shown. The study begins using traditional bipolar transistors since the latchup effect is originated as a parasitic circuit composed of such devices. Then, an equivalent circuit built up of MOS transistors is exploited, resulting an even more promising and challenging configuration than that obtained via bipolar transistors. As the MOS transistors are widely used at present in microelectronics devices and sensors, a latchup-based cell is proposed as a novel structure for future applications in particle detection, amplification of signal sensors and radiation monitoring.

Novel approaches to radiation detection and readout using the latch up effect

An alternative topology for solid-state pixel detectors is described. It is based on latch-up effect, usually exploited in solid-state electronic switches like thyristor and Silicon Controlled Rectifiers (SCRs). It is proposed here to use this effect as a simple building-block element for particle and radiation detection. Review of the latch-up effect and description of circuit topologies under investigation to assess the operating principle and initial experimental results will be presented. Applications in particle and radiation detection will be suggested.

Improvement of a Gas Scintillation Proportional Counter

A prototype GSPC without the gas purification system was developed in China Institute for Radiation Protection(CIRP). Xenon filled GSPC has many advantages, including high energy resolution, large detection area, ability for implementing position sensitive detection, etc. It may find a wide application in low energy X-ray and γ-ray fields, e.g., astronomy X-ray detection, medical imaging. Further applications in neutron and charged heavy particle detection are also possible. Several tests for 241Am and 55Fe have been carried out to check out its preliminary performance. Currently the energy resolution is still far from expectation, nevertheless, the concept is proved to be promising and the experimental results suggest the way for further improvements. The possible ways for improvement of the detector performance are discussed in conclusion. This work was funded by National Natural Science Foundation of China.Authorization number:10375054(National Natural Science Foundation of China).

Metastable Frenkel pairs and the W11–W14 electron paramagnetic resonance centers in diamond

Diamond is a material that shows great promise for particle detection applications. However, under irradiation with energetic particles, many thermally stable defects are created, made up of lattice vacancies, self-interstitials, and complexes with impurities. Relatively distant Frenkel (vacancy--self-interstitial) pairs have long been used to explain optical and magnetic spectra in irradiated material. However, in diamond we show, using first-principles methods, that the ability of carbon to form $s{p}^{2}$-, $s{p}^{3}$-, and $\ensuremath{\pi}$-bonding configurations leads to particularly strong reconstructions between vacancy--self-interstitial pairs within a few atomic spacings of each other. The resultant complexes are anticipated to be optically and paramagnetically active, and we propose correlation of negatively charged Frenkel pairs with the W11--W14 paramagnetic centers, where substitutional nitrogen donors act as source of electrons and are not an intimate component part of the paramagnetic defects.

Radiation damage microstructures in silicon and application in position sensitive charged particle detection

Area selective irradiation using MeV ions having different ranges has been performed in a nuclear microprobe to produce radiation damage microstructures in silicon photodiodes. IBIC (Ion Beam Induced Charge) technique has been used for on line monitoring of radiation damage produced by different fluences of He, Li and O ions of MeV energies. Three-dimensional patterning of radiation damage structures may be used for different applications. By creating a region of constant damage gradient in Si photodiode, position sensitive radiation detection has been demonstrated.

Track analysis system for application in alpha particle detection with plastic detectors

In this work a track analysis system used to detect alpha particles with SSNTD and installed recently in our laboratory is presented. With this system we intend to avoid the disadvantages found in the manual counting, with an improvement of the counting statistics. Also, the determination of various track parameters and their relation with exposure conditions were achieved. Some results of detector and tracks’ features determined in the new system are presented, e.g., the detector (LR 115) response to the alpha particle energy and typical track shape parameters and their relation to the particle characteristics.

Influence of electrical defects on diamond detection properties

Abstract The remarkable properties of diamond, together with its radiation hardness, make it an attractive material for specific applications in X-rays and charged particle detection. Because electrically active defects are known to influence the detection properties, a thorough study of these defects is of great interest in order to improve the detector characteristics. In this work, the response of diamond devices to X-rays and alpha particles is investigated and the results are correlated with the presence of traps analysed using thermally stimulated current (TSC) methods. The results of TSC analysis on natural diamond have enabled the determination of the energy of three levels activated near room temperature at 0.7, 0.71 and 0.95 eV and of a main principal level on CVD diamond at 1.2 eV activated near 550 K. The comparative study of TSC measurements and time dependent X-ray sensitivity are investigated on natural diamonds. The results confirm the improvement of the detection properties after having filled deep trap levels, and show a detrimental effect of the trapping levels emptied at room temperature on the turn-off time of diamond. Further, the temperature dependence of the detector response under alpha particles was also investigated. Clearly, a temperature increase above a level activated at 375 K leads to the improvement of the detection properties.

A 2-D amplifier array chip for pixel detector readout

A 32 × 16 array of 200 × 200 μm 2 pixel amplifier cells has been fabricated using 1.5 μm CMOS technology. Each pixel contains charge amplification and noise filtering, a comparator and a one-bit latch. A fast readout scheme incorporating zero suppression has been designed. Amplifier array chips can be interconnected and “tiled” onto the surface of a large area pixel detector using the bump-bonding technique. The measured performance of the individual pixel amplifiers is presented, and the operation of the readout circuitry is described. The noise dependence on input capacitance is 125+0.33/fF rms electrons. For the anticipated detector capacitance noise levels of less than 200 rms electrons can be expected. Silicon hybrid pixel detectors can be used for applications in synchrotron X-ray, autoradiography and high energy particle detection.

Observation of soft-x-ray spatial coherence from resonance transition radiation.

We have observed the spatial distribution of coherent or resonance transition radiation (RTR) in the soft-x-ray region of the spectrum (1--3 keV). Resonance transition radiators were constructed and tested at two accelerators using electron-beam energies ranging from 50 to 228 MeV. These radiators emitted soft x rays in a circularly symmetrical annulus with a half-angle divergence of 2.5--9.0 mrad. The angle of peak emission was found to increase with electron-beam energy, in contrast to the incoherent case, for which the angle of emission varied inversely with electron-beam energy. By careful selection of foil thickness and spacing, one may design radiators whose angle of emission varies over a range of charged-particle energies. A particular RTR mode (r=m=1) was found to give a sharp annular ring that becomes more accentuated as the number of foils is increased. The RTR effect has application in particle detection, beam diagnostics, x-ray source brightness enhancement, and x-ray free-electron-laser emission.

A prototype pixel readout chip for asynchronous detection applications

A two-dimensional array of amplifier cells has been fabricated as a prototype readout system for a matching array of silicon diode detectors. Each cell contains a preamplifier, shaping amplifier, comparator and analogue signal storage in an area of 300 μm × 320 μm using 3 μm CMOS technology. Full size chips will be bump bonded to pixel detector arrays. Low noise and asynchronous operation are novel design features. With noise levels of less than 250 rms electrons for input capacitances up to 600 fF, pixel detectors will be suitable for autoradiography, synchrotron X-ray and high energy particle detection applications. The design of the prototype chip is presented and future developments and prospects for applications are discussed.

Electron emission from sharp points in liquid argon

Electron charge injection from a point electrode in gaseous and in liquid argon has been observed and its characteristics studied. In liquid argon, as we have observed, the charge dependence on applied voltage is governed by space charge limitation. The emission was found to take place (with the electrode in liquid phase) not continuously but as a pulsed injection. The pulsing rate has been studied as a function of the voltage, time and electrode separation. The measurements done so far have been performed in a closed environment with an impurity content of argon of the order of some tenth of p.p.b. (oxygen, CO2, etc.). Possible applications in liquid-argon purification and particle detection is presented.

Recent developments in detector research

Recently developed methods of cryogenic particle detection and potential applications will be introduced. The main part of this article focuses on our experimental results on two different approaches of detecting nuclear radiation with superconducting tunnel junctions. The best energy resolution is obtained when the junction itself serves as absorber. Using Sn/SnO x/Sn tunnel junctions we obtained an energy resolution of about 90 eV for 6 keV X-rays up to now. The processes limiting the resolution of the present devices will be discussed. Larger absorber masses and position resolution are realized by an entirely new type of particle detector based on the detection of nonthermal phonons which are generated by the absorption of radiation within a single-crystalline absorber of dielectric material. We report on experimental tests of a detector composed of a silicon single crystal (size: 10 × 20 × 3 mm 3) and of an array of superconducting Al/Al 2O 3/Al tunnel junctions evaporated onto the surface of the crystal, serving as phonon detectors. Pulse height analysis and the investigation of time differences between pulse onsets in different junctions are shown to yield information about the absorption point of α-particles.

Thomas point process in pulse, particle, and photon detection

Multiplication effects in point processes are important in a number of areas of electrical engineering and physics. We examine the properties and applications of a point process that arises when each event of a primary Poisson process generates a random number of subsidiary events with a given time course. The multiplication factor is assumed to obey the Poisson probability law, and the dynamics of the time delay are associated with a linear filter of arbitrary impulse response function; special attention is devoted to the rectangular and exponential case. Primary events are included in the final point process, which is expected to have applications in pulse, particle, and photon detection. We refer to this as the Thomas point process since the counting distribution reduces to the Thomas distribution in the limit of long counting times. Explicit results are obtained for the singlefold and multifold counting statistics (distribution of the number of events registered in a fixed counting time), the time statistics (forward recurrence time and interevent probability densities), and the counting correlation function (noise properties). These statistics can provide substantial insight into the underlying physical mechanisms generating the process. An example of the applicability of the model is provided by betaluminescence photons produced in a glass photomultiplier tube, when Cherenkov events are also present.

Multiplied-Poisson noise in pulse, particle, and photon detection

Multiplication effects in point processes are important in a number of areas of electrical engineering and physics. We examine the properties and applications of a point process that arises when each event of a primary Poisson process generates a random number of subsidiary events, with a given time course. The multiplication factor is assumed to obey the Poisson probability law, and the dynamics of the time delay are associated with a linear filter of arbitrary impulse response function; special attention is devoted to the rectangular and exponential cases. The process turns out to be a doubly stochastic Poisson point process whose stochastic rate is shot noise; it has application in pulse, particle, and photon detection. Explicit results are obtained for the single and multifold counting statistics (distribution of the number of events registered in a fixed counting time), the time statistics (forward recurrence time and interevent probability densities), and the power spectrum (noise properties). These statistics can provide substantial insight into the underlying physical mechanisms generating the process. An example of the applicability of the model is provided by cathodoluminescence (the phenomenon responsible for the television image) where a beam of electrons (the primary process) impinges on a phosphor, generating a shower of visible photons (the secondary process). Each electron produces a random number of photons whose emission times are determined by the (possibly random) lifetime of the phosphor, so that multiplication effects and time delay both come into play. We use our formulation to obtain the forward-recurrence-time probability density for cathodoluminescence in YVO 4 :Eu3+, the excess cathodoluminescence noise in ZnS:Ag, and the counting distribution for radioiuminescence photons produced in a glass photomultiplier tube. Agreement with experimental data is very good in all cases. A variety of other applications and extensions of the model are considered.

Discrimination of shot-noise-driven poisson processes by external dead time: Application to radioluminescence from glass

The shot-noise-driven doubly stochastic Poisson point process (SNDP) describes the photodetection statistics for several kinds of luminescence radiation (e.g., cathodoluminescence). This process, which is bunched (clustered) in character and is associated with multiplied Poisson noise, has many applications in pulse, particle, and photon detection. In this work we describe ways in which dead time can be used to constructively enhance or diminish the effects of point processes that display such bunching, according to whether they are signal or noise. We discuss in some detail the subtle interrelations between photocount bunching arising in the SNDP and the antibunching character arising from dead-time effects. We demonstrate that the dead-time-modified count mean and variance for an arbitrary doubly stochastic Poisson point process (DSPP) can be obtained from the Laplace transform of the single-fold and joint moment-generating functions for the driving rate process. The dead time is assumed to be small in comparison with the correlation time of the driving process. Specific calculations have been carried out for the SNDP. The theoretical counting efficiency ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> and normalized variance ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">υ</inf> fox shot-noise light with a rectangular impulse response function are shown to depend principally on the dead-time parameter and on the number of primaxy events in a correlation time of the driving rate process. The values of ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</inf> and ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">υ</inf> are significantly reduced below those obtained with the constant-rate Poisson because of the clustering associated with the SNDP. The theory is in good accord with the experimental values of these quantities for radioluminescence radiation in three transparent materials (fused silica, quartz, and glass). Various parameter values for each material have been extracted. For large counting times, the experimental photon-counting distributions are shown to be well described by the Neyman Type-A theoretical distribution, both in the absence and in the presence of dead time.

Heavy Ion Nuclear Tracks—An Emerging Technology

Nuclear tracks are a logical extrapolation of the principles of cloud and bubble chamber onto solids. Besides their well‐known application in particle detection, in solids a completely new aspect arises, the generation of extremely fine permanent tracks, which can be transformed into open channels. Nuclear tracks are therefore a unique single‐particle structuring tool. Applications comprise (i) single hole membranes for particle counting and sizing, (ii) manufacture of microfilters with very uniform hole sizes, (iii) modification of magneto‐optic materials for application in display memories, and (iv) micromachining\\ of surfaces.