Alpha Particle Beam Research Articles

Survival of human lung epithelial cells following in vitro α-particle irradiation with absolute determination of the number of alpha-particle traversals of individual cells

Purpose : To throw light on human exposure to domestic radon and radon progeny, the effects of low doses of alpha-particle irradiation on normal human lung epithelial cells has been studied. At such low exposure levels the concept of dose is inadequate due to the stochastic variation in the number of α -particle traversals per cell. The objective of the current study was to establish an accurate survival curve for human lung epithelial cells with absolute determination of the exact number of α -particle traversals of individual cells. Materials and methods : Irradiation of L132 cells growing in tracketch detector-based cell dishes, was performed using a collimated alpha-particle beam from a 210 Po source. The number of α -particle traversals through each individual cell was scored by using a technique of retrospective track-etch dosimetry. This technique is based upon image matching and mapping of corresponding cell and α -particle track images. The spatial resolution of the hit determination procedure was ±0.9 μ m. Results : Surviving fractions of cells (SF) showed strict dependence on the number of nuclear traversals (n) , with SF (n) = a exp (-bn) , a =0.957 (±0.046), b =0.587 (±0.059), R 2 = 98.8%. No significant dependence on the number of nuclear membrane traversals (m) or the number of cytoplasm traversals (c) was observed.

Conference

A series of experiments has determined the response of CdZnTe radiation detectors to electrons and alpha particles. Densely ionising particles result in an “S-shaped” pulse which is somewhat different in shape to those generated during photon interactions. A preliminary analysis of these pulse shapes is presented and the impact of this on possible schemes for pulse-shape discrimination is discussed. By altering the position of interaction of the alpha-particle beam in the detector, it is possible to analyse the non-uniformity of the electric field present in these detectors. Results are presented to demonstrate these effects, and the implications of these for operation of CdZnTe detectors in charged particle beams will be discussed.

Comparative characterization of the irradiation effects induced in metallic glasses by pulsed laser and alpha particle beams

Nd:YAG laser (λ=532 nm, τ=8 ns, Φ=30 J/cm2, ν=10 Hz) induced transformations in Fe81B13.5Si3.5C2 metallic glass were characterized by transmission and conversion electron Mössbauer spectroscopy, hysteresis loops and AC susceptibility measurements. The radiation-driven changes were further compared with alpha particle beam irradiation effects (W=2.8 MeV, Φ=1016 and 1017 cm−2) in the same amorphous material. Pulsed laser irradiation of Fe81B13.5Si3.5C2 metallic glass was found to induce magnetic anisotropy, surface oxidation, onset of crystallization, slight increase in the saturation magnetic moment and changes in the imaginary susceptibility component. Alpha particle beam irradiation of Fe81B13.5Si3.5C2 metallic glass caused partial crystallization of the bulk of the specimen, total crystallization of the surface, as well as dose-dependent changes in the saturation magnetic moment, hysteresis and real susceptibility component.

The charged particle response of CdZnTe radiation detectors

A series of experiments has determined the response of CdZnTe radiation detectors to electrons and alpha particles. Densely ionising particles result in an “S-shaped” pulse which is somewhat different in shape to those generated during photon interactions. A preliminary analysis of these pulse shapes is presented and the impact of this on possible schemes for pulse-shape discrimination is discussed. By altering the position of interaction of the alpha-particle beam in the detector, it is possible to analyse the non-uniformity of the electric field present in these detectors. Results are presented to demonstrate these effects, and the implications of these for operation of CdZnTe detectors in charged particle beams will be discussed.

Interaction of alpha particle beams with metallic glasses

Samples of Fe 40Ni 38Mo 4B 18, Fe 78B 13Si 9 and Fe 66Co 18B 15Si 1 metallic glasses, selected with respect to the different values of their magnetostriction constants, were irradiated with alpha particle beams ( W=2.8 MeV) using radiation doses of 10 16 and 10 17/cm 2. The fundamental effects underlying the interaction of alpha particle beams with amorphous magnets were studied by transmission and conversion electron Mössbauer spectroscopy (CEMS), hysteresis loops and a.c. susceptibility measurements, and scanning electron microscopy (SEM). The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformation was found to depend on the particle flux and sample composition. Differences between bulk and surface behaviors of the magnetic texture and constituent phases were evidenced. Radiation-driven changes in the saturation magnetic moment, coercive field, real and imaginary components of the a.c. response were observed for all samples studied and found to depend on the radiation dose employed. The surface morphology of the radiation-induced crystalline precipitates was shown to vary as a function of composition, such that both spherical and dendritical modes of growth were observed. By stimulating unconventional pathways for the crystallization process, the interaction of alpha particle beams with glassy ferromagnets offers unique opportunities to understand the fundamentals of nucleation and growth in these systems.

Fluence dependence of IBIC collection efficiency of CMOS transistors

IBIC (Ion Beam Induced Charge) imaging of deep structures of semiconductor devices with a focused MeV light ion beam has been shown to offer significant advantages over the established EBIC (Electron Beam Induced Current) technique, because the large range and the small lateral straggling of the ion beam allows direct imaging of buried device structures. The technique is limited by the accumulation of radiation damage that reduces the charge collection efficiency. We report on measurements of the beam fluence dependence on IBIC collection efficiency for proton and alpha particle beams at 2000 keV energy. A HCF4007 CMOS transistor array was used in these measurements. The influence of surface passivation layers on charge collection efficiency and its evolution with ion dose is discussed.

Nuclear microprobe analysis and imaging: Current state of the art performances

The current state-of-the-art performances claimed for nuclear microbeam spatial resolutions are: (a) 400 nm spot sizes for high current (100 pA) proton beams, (b) 400 nm for high current alpha particle beams, (c) 100 nm for low proton current (<0.1 pA) applications such as Scanning Transmission Ion Microscopy (STIM) and Ion Beam Induced Charge (IBIC) and (d) 50 nm for low current alpha particles. These claims, however, have been undermined not only by the lack of a common and generally accepted resolution standard, but also by the lack of a consistent approach between groups regarding a recognised method of beam spot measurement. The lack of a definitive method for assessing spatial resolution is hindering the future development of nuclear microprobes to higher spatial resolutions. We require the manufacture of resolution standards specifically tailored for nuclear microprobe spot size measurements, for both high and low current operations. Until such resolution standards are available, one commercially available standard which has high potential for high current proton beam resolution tests is the Ebeam test chip manufactured for the characterisation of electron beam testers. This chip has patterns as small as 0.5 μm in size produced in 0.5 μm thick aluminium by direct electron beam writing. Using both analytical Particle Induced X-ray Emission (PIXE) imaging and PIXE line scans, the nuclear microscope facility at the National University of Singapore has demonstrated spatial resolutions of less than 400 nm for a 100 pA beam of 2 MeV protons. Low current resolution standards have more stringent requirements. One potential standard tested in Singapore is a prototype self-supporting X-ray mask used in X-ray lithography. This test standard, however, is not commercially available at the moment, is fragile and therefore difficult to handle and easily fractured. Using off-axis STIM imaging and line scanning over this mask, the NUS nuclear microscope facility has demonstrated beam spot sizes less than 130 nm for a 1 pA 2 MeV proton beam.

Ion sources at the KVI (abstract)

At the KVI there are presently four ion sources available: POLIS, for polarized protons and deuterons, to be injected in the new superconducting cyclotron AGOR ECRIS3, to produce highly charged ions for AGOR, ECRIS4, to produce highly charged ions for the Atomic and Surface Physics research facility (essentially a copy of ECRIS3), and CUSP, for high intensity AGOR beams of protons, deuteron, or alpha particles. We will report here on the performance and status of POLIS and ECRIS3. POLIS is an atomic beam type polarized ion source, according to the well known scheme with a cryo cooled dissociator, watercooled hexapole magnets, “strong field” and “weak field” radio frequency (rf) transitions for hydrogen and deuterium, and a 2.45 GHz electron cyclotron resonance (ECR) type ionizer. The source was constructed in a joint effort with the Forschungszentrum Karlsruhe, Cyclotron department. The ionizer section was modified and can be operated up to 40 kV. Following successful tests and deuteron polarization measurements at low energies, POLIS was connected to AGOR in November 1996. Most parts are now adapted to the AGOR-KVI control system. The first experiments with proton beams (190 MeV) from AGOR were done with polarized beams. As a consequence, the first measurement of proton polarization could be done only during these experiments, and all efforts to improve the polarization had to take place also during experiments. Efforts to get the weak field transition in operation have given a present best value of polarization of 70%±0.5% of the theoretical value. This value is deduced from an assumed analyzing power of the applied reaction. The strong field unit is not perfect; the best value which has been observed is 56%±0.5%. However, the difference between the given polarizations could be the result of a systematic error in the measurement of polarization “zero.” The output of POLIS is in the order of 50 μÅ. The running time is usually 1–2 weeks (with nozzle at 53 K) until the dissociator and nozzle become contaminated; with a nitrogen layer (nozzle at 35 K) the polarization degree tends to be higher, but the running time is reduced to 3–5 days. POLIS has been in operation during more than 70% of the 33 weeks scheduled for experiments with AGOR since November 1996. Present activities concentrate on the improvement of the strong field unit, increasing the ionizer efficiency and the running time. ECRIS3 is a room temperature ECR ion source, with rf and gas feed according to the CAPRICE scheme. Its performance has been reported earlier (RIKEN 95). Gas mixing is important for the production of highly charged ions. Like in other sources, the anomaly for oxygen isotopes has also been measured. One new observation concerning gas mixing, in particular for the production of argon beams, is the following: For medium charge states, e.g., Ar8+, there is a slight preference for helium as a mixing gas, as compared to pure argon. In fact, oxygen is not good here. On the contrary, for high charge states like Ar14+, oxygen is a very good mixing gas, helium has only a small effect, but the best results have been obtained with isotopic O18 as a mixing gas. Recently, the same has been observed with CAPRICE 10 GHz at CEN-Grenoble, and to some extent with ECRIS4.

Phase Transformations Induced in Metallic Glasses by Pulsed Laser and Alpha Particle Beam Irradiation

AbstractNd:YAG laser (λ,=532 nm, τ=8 ns, Φ =30 J/cm2, v=10 Hz) induced transformations in Fe81B135Si35C2metallic glass were characterized by transmission and conversion electron Mossbauer spectroscopy, hysteresis loops and ac susceptibility measurements. The radiation-driven changes were further compared with alpha particle beam irradiation effects (W=2.8 MeV, Φ=1016and 1017 cm−2) in the same amorphous material. Pulsed laser irradiation of Fe81B135Si3.5C2 metallic glass was found to induce magnetic anisotropy, surface oxidation, onset of crystallization, slight increase in the saturation magnetic moment and changes in the imaginary susceptibility component. Alpha particle beam irradiation of Fe81B13.5Si3.5C2 metallic glass caused partial crystallization of the bulk of the specimen, total crystallization of the surface, as well as dose-dependent changes in the saturation magnetic moment, hysteresis and real susceptibility component.

Minor heavy ion electromagnetic beam–plasma interactions in the solar wind

It is shown that the velocity threshold of the right‐hand‐polarized ion‐ion resonant instability decreases with decreasing gyrofrequency values of the beam ions, and also, the system can become unstable for very small beam concentrations. In order to illustrate the results, a plasma consisting of a proton background and a very tenuous O+ ion beam is considered. It is shown that for an ion beam of nO+/np = 10−4, the threshold velocity is VO+ ∼ 1.36VA (VA is the Alfvén velocity), and the maximum growth rate is of the order of 10−3Ωp (Ωp is the proton gyrofrequency). We apply these results to high‐speed solar‐wind‐type plasmas consisting of a proton background, an alpha particle beam, and a beam of O+ ions. It is also shown that the presence of alpha particles reduces the velocity instability threshold of the O+‐p resonant instability.

Technique for fluence attenuation by acceleration of decay particles

A nuclear beam of extremely low intensity was realized by accelerating decay particles from heavy radioactive nuclei through an AVF cyclotron. Alpha particles from a 241Am source (3.3 × 10 6 Bq) were accelerated up to 30 MeV with a cyclotron starting from a proper radius. The weak beam of alpha particles was detected and its energy and microscopic time structure was analyzed. The count rate was attenuated down to 5 counts per minute which is only 1 20 of the value estimated from source geometry and accelerator acceptance.

Alpha Particle Beam Interactions with Fe-Based and FeCo-Based Amorphous Magnets

AbstractSamples of Fe78B13Si1 and Fe66Co18B15Si1 metallic glasses were irradiated with alpha particle beams (W=2.8 MeV) using radiation doses of 1016 and 1017 cm2. Irradiation-induced effects on the magnetic and structural properties of alloy samples were studied by transmission and conversion electron Mbssbauer spectroscopy. The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformation was found to depend on the particle flux and sample composition. Differences between bulk and surface irradiation behaviors were demonstrated.

Ion-Beam Analysis of Polymer Surfaces and Interfaces

Ion-beam analysis of chemical composition as a function of depth is by now well-established for inorganic materials and is an important method of investigating growth of thin films. It has been applied to polymers much more recently, perhaps because fairly obvious problems with radiation damage discouraged workers in this field initially. Ion-beam analysis has developed, however, into a analytical tool that complements other methods, such as x-ray photoelectron spectroscopy and neutron reflection, very well. The purpose of this short article is to give the reader an introduction to its current uses in polymers.The ion beams of ion-beam analysis are typically highly energetic (1–5 MeV) beams of 4He++. While other beams are used, for example, 3He and 15N, alpha particle beams are used in the vast majority of experiments reported in the literature. Two major categories of experiments are carried out with such beams. Rutherford backscattering (RBS) spectrometry to detect heavy elements in the polymer and forward recoil spectrometry (FRES) (also known as elastic recoil detection) to detect the isotopes hydrogen and deuterium. The basic principles for each method are similar.

A strong isotopic effect in prescission charged particle multiplicities

In the framework of the Combined Dynamical Statistical (Langevin — Monte-Carlo) Model we investigate two properties of the multiplicities of light particles (neutrons, protons and alpha) accompanying the fission process: their dependence on the spin of the compound nucleus (CN) and on the neutron number of CN at a fixed proton number. Calculations are performed for fission of 246–258Cf induced by α-particles and by heavy ions. No noticeable dependence on the spin distribution has been found, whereas the isotopic dependence turned out to be very strong. These conclusions can be considered as theoretical predictions for experiments planned to the performed in the near future using protons and alphaparticle beams.

Alpha particle radiography with the CR-39 nuclear track detector

This work studies the alpha particle radiography technique, in conjunction with the CR-39 plastic track detector. The irradiations were made in the CV-28 cyclotron at IEN/CNEN/RJ, using a 7 MeV/nucleon alpha particle beam. All etches were performed by using a 6.25 N NaOH solution, at 70°C. The best etch time to obtain radiographs was determined. A calibration curve (Gray Levels x Energy Loss)was obtained, so as to permit a quantitative interpretation of the images. Its behavior was checked against several experiments with other energy degrading materials, namely, aluminum, mylar and CR-39 itself. The error propagation on energy resolution was also investigated. Several radiographs of in vitro biological specimens were obtained. The results showed the potential capability of this technique for studies in paleontology.

Radiography of biological specimens with alpha particles and the CR-39 SSNTD

This work studies the alpha particle radiography technique in conjunction with the CR-39 SSNTD. The irradiations were made in the CV-28 cyclotron at IEN/CNEN/RJ using a 7 MeV/nucleon alpha particle beam. The best etch time to obtain radiographs was determined as six hours. A calibration curve was obtained, so to allow a quantitative interpretation of the images to be performed. Its behavior was checked by several experiments with other energy degrading materials. Several radiographs of “in-vitro” biological specimens were obtained. The results showed the potential capability of this technique for studies in paleontology.

Interaction of Alpha Particle Beams with Fe-Based and FeNi-Based Glassy Ferromagnets

AbstractSamples of Fe78B13Si9 and Fe40Ni38Mo4B18 metallic glasses were irradiated with alpha particle beams (W=2.8 MeV) using radiation doses of 1016 and 1017 cm-2. Irradiation-induced effects on the magnetic texture and phase composition of alloy samples were studied by Mössbauer spectroscopy. Related morphological changes and resultant crystalline precipitates were characterized by scanning electron microscopy. The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformation was found to depend on the particle flux and sample composition. The lowest radiation dose employed was found to be more effective in inducing amorphous-to-crystalline transformations in both ferromagnetic alloys studied. In addition, the FeNi-based amorphous system investigated was found to be more stable than the Fe-based metallic glass, exposed to the same particle-beam irradiation conditions. By stimulating unconventional pathways for the crystallization process, the interaction of alpha particle beams with glassy ferromagnets offers unique opportunities to understand the fundamentals of nucleation and growth in amorphous magnets.

Application of “abnormal” X-ray yields from primary targets of compounds in XSQR studies with proton and alpha particle beams

Previous reports on “abnormal” yields from charge induced X-ray studies (CHIX) have demonstrated conclusively that such yields are exceptionally high when compared to PIXE at low incident particle energies. A combination of low incident energies and high X-ray yields could be useful for XSQR investigations with low energy accelerators, particularly in studies where the sample matrix “swamps” the signals from the impurities of interest such as chromium in steels (overwhelming Fe peak) and Cu in brass (high Zn peak). This work discusses the possible applications of CHIX to XSQR studies with primary targets of compressed powders of selected compounds under bombardment with 3000 keV alphas and 800 and 1000 keV protons. A feature of interest in the use of comparatively low beam currents (between 100–150 nA) in the absence of sample cooling. The advantages and limitations of the application are discussed.

Diffuse minor ions upstream of simulated quasi‐parallel shocks

We have performed a number of one‐dimensional hybrid (particle ions, massless fluid electrons) simulations of quasi‐parallel collisionless shocks in order to elucidate the origin of diffuse upstream minor ions. Minor ions are treated self‐consistently by the hybrid code; however, a number of runs have also been performed wherein the minor ions are treated as test particles. We have investigated the dependence of the density ratio bias factor fnof; (the alpha to proton ratio of the diffuse ions normalized to the solar wind ratio) on shock Mach number, solar wind beta (thermal to magnetic pressure) and on angle ΘBno between shock normal and magnetic field and found strong dependencies on all parameters. An addition of 5% alpha particles changes the shock structure, resulting in a significant modification of the density ratio bias factor as compared to the test particle cases. In the case of a low beta solar wind (β ≃ 0.1) the solar wind alpha particles penetrate the shock ramp rather unaffected and gyrate in the downstream magnetic field as a whole. The alpha particle beam returns occasionally to the shock ramp and spatially localized clouds of alpha particles can be found in the upstream region. With increasing Mach number the gyroradius of the alpha particles increases and it becomes easier for the alpha particle beam to return from downstream to the shock; a high density of clouds is found upstream. In the case of a higher beta solar wind (β≳0.5) and moderate Mach numbers, no localized alpha particle clouds leave from downstream into the upstream region. This can be attributed to the smoother shock transition in the case of higher beta shocks. The effect of beta and Mach number is counteracting: high Mach number shocks can lead even at higher beta to minor ion clouds in the upstream region. Higher beta shock simulations result in an increase of fnof; with beta and ΘBno. The increase with beta is due to the fact that diffuse ions originate mainly from the high‐energy tail of the distribution in the upstream rest frame. It is suggested that large ΘBno implies a more tangential downstream field and the alpha particles reach the shock during their downstream gyration easier.

Determination of nitrogen using the 14N(α, p) 17O nuclear reaction

A technique for quantifying nitrogen in thin films using the 14N(α, p) 17O reaction is reported. An incident alpha particle beam with energy near 3.9 MeV is used and emitted protons are detected at a lab angle of 135°. A 15 μm Kapton foil is placed over the detector to stop elastically scattered alpha particles. A thin film containing a known areal density of nitrogen is used for calibration. We present relative yield data on protons from the 14N(α, p 0) 17)O reaction at 135° lab angle from 3.4 MeV to 4.0 MeV as well as an example of the application of this technique in determining nitrogen content in thin films. Possible interfering reactions, particularly 28Si(α, p) 31, are also discussed.