Silicon Surface Barrier Detector Research Articles

Analysis of the composition of incident hydrogen ion beams accelerated by a Van de Graaff electrostatic accelerator

A new technique is proposed for analysis of the composition of incident hydrogen ion beams accelerated by Van de Graaff electrostatic accelerators. The procedure is based on the analysis of the energy distribution of the neutral fraction of the hydrogen ion beam by a silicon surface barrier detector. It is shown that along with the main beam components (H +, H 0) at the energy E 0, another component exists at the energy 0.25 E 0. This component is brought about through acceleration and breakup of molecular H 2 + ions. However such inhomogeneities do not play a noticeable role in formation of the low energy tail of hydrogen ions backscattered from thin self-supporting films.

Incident Angle Dependence of Residual Defect in Silicon Surface Barrier Detector

Incident Angle Dependence of Residual Defect in Silicon Surface Barrier Detector

The limit of stability of proton-rich thallium isotopes: a search for the decay of177Tl

The fusion reaction74Se+106Cd→180Pb* at a compound nucleus excitation energy Ex ≃ 40 MeV, has been used in a search for the decay of the unknown nucleus177Tl. Evaporation residues were velocity and mass analysed prior to implantation into a position sensitive silicon surface barrier detector. No evidence was discovered for the proton or alpha-decay of177Tl for a cross-section > 10−5+10 nb. This indicates either that177Tl decays too rapidly (t1/2 < 1 μs) by proton emission for the decay to be detected, or that177Tl is produced with a cross-section less than the limit established in the present experiment. The following nuclear decay half-lives were measured with improved accuracy;177Hg (t1/2 = 130±5 ms),178Hg (t1/2=250±25 ms) and177Au (t1/2=1180±70 ms). The experiment also provided the first direct confirmation of the correct mass assignment of the alpha-decay, Eα=6.26 MeV, to the decay of176Au. Two additional halflife measurements of proton-rich Osmium isotopes are also presented from a previous similar experiment;165Os (t1/2=73±8 ms) and166Os (t1/2 = 194±17 ms).

Pulse height defect of low energy ions in surface barrier detectors

Data of pulse height defects (PHD) of silicon surface barrier detectors (SBD) are very important for the particle mass assignment by means of TOF measurements. We have measured pulse height signals from SBD for protons (control) and five heavy ion species ( 16O, 19F, 28Si, 35Cl, 81Br) in the incident energy range of 2–8 MeV. The experimental data have been best-fitted to a proposed empirical formula which reproduces PHD values for all particles with A = 16–80 in this energy range. The experimental results are discussed by comparing them with defect values calculated by using the TRIM code and with values calculated by the empirical formula proposed by Kaufman.

Imaging of thin biological sections using STIM and related techniques — a comparative study

When using STIM for imaging of thin biological sections, the obtainable energy resolution is an important parameter. A comparison is made between three detector types, a conventional silicon surface barrier detector, a photodiode and a time of flight system. The study shows that the surface barrier detector has the best energy resolution; however, the time of flight system has the potential to reach the best energy resolution by simply increasing the corresponding flight length.

The application of channeling to masked ion beam lithography

Various orientations of undoped single crystal silicon were examined from the standpoint of transmitted half-angle to determine the best orientation for masked ion beam lithography (MIBL). The effect of boron, present at a level of ∼ 10 20/ cm 3, was also determined. Transmitted angular distributions, for particles of incident energy in the range 80–180 keV, were measured using a moveable silicon surface barrier detector with a resolution of ∼ 3 keV and an acceptance angle of < 0.1°. Planar orientations yielded smaller transmitted half-angles than axial orientations without a significant loss in transmitted yield. The half-angle of particles transmitted along planes, unlike axes, was found to vary with azimuthal angle. The best orientation for use in MIBL was determined to be the {110} planar orientation. Half-angles for particles transmitted along this plane were smallest for scans perpendicular to the plane and largest for scans parallel to it. The presence of boron was found to increase the transmitted half-angle by ∼ 10% over the entire energy range.

A proton polarimeter for beam energies below 300 keV

A nuclear polarimeter based on the low energy analyzing power of the 6Li(p, 3He)α reaction has been developed and tested for proton energies below E p = 300 keV. The polarimeter uses a 6LiF target evaporated on a water-cooled tantalum backing. The target is observed at backward angles by four silicon surface barrier detectors. The energy dependence of the analyzing power under 130° for the 6Li(p, 3He)α reaction has been determined down to 200 keV. Spin rotation has been observed via a magnetic field incorporated in a Wien filter demonstrating that the polarimeter is operational.

Candidate for Residual Defect in Silicon Surface Barrier Detector

The residual defect in the pulse height defect of a silicon surface barrier detector is investigated theoretically. An application of the model of charge collection process leads to another candidate for the residual defect than the recombination defect. The residual defect is due to incomplete charge induction by electrons and holes inside a plasma column, which has dielectricity-like property. Quantity of induced charge is shown in a ratio to the number of produced electron-hole pairs as functions of depletion layer thickness, plasma column length and resistivity of the detector. Experimental result of the residual defect of 58Ni ion and its analysis method applying this model are presented. The residual defect is successfully explained by this model.

Incident Angle Dependence of Residual Defect in Silicon Surface Barrier Detector.

(1991). Incident Angle Dependence of Residual Defect in Silicon Surface Barrier Detector. Journal of Nuclear Science and Technology: Vol. 28, No. 6, pp. 582-584.

Feasibility Study of Silicon Surface Barrier Detector as Charged Particle Identifier.

The residual defect in pulse height defect in a silicon surface barrier detector (SSB) has been a theme of extensive studies. The residual defect was taken as recombinations of electrons and holes under a weak electric field strength(1). Although many works reported models of recombination, none of them could explain the dependences of the residual defect on bias voltage and on resistivity of SSB(2)(4).Recently, the author reported a model of dielectric effect of a plasma column(5). In this model, the residual defect was theoretically explained by a dielectric property of a plasma column, which was produced by an incident heavy ion. The residual defect is caused by an incomplete charge induction by electrons and holes inside the dielectric plasma column, which screens the movement of inner carriers. The model of dielectric effect included one parameter, called screening factor. The screening factor indicated the time averaged rate of screening carriers from positive and negative electrodes and were determined by experiments on the residual defect. With the experiments on the residual defect of many kind of charged particles, it was concluded that the screening factor was almost proportional to the density of electron-hole pairs of a plasma column(6). In this short note, a method of deducing heavy ion energy is proposed, first. Withthis method, the energy of heavy ion is estimated more accurately than before. Secondly, a feasibility of an SSB as a charged particle identifier is discussed. With one SSB, the atomic number and mass number of incident heavy ion are determined, provided that the screening factor is proportional to the electron-hole density of a plasma column.

Candidate for residual defect in silicon surface barrier detector.

The residual defect in the pulse height defect of a silicon surface barrier detector is investigated theoretically. An application of the model of charge collection process leads to another candidate for the residual defect than the recombination defect. The residual defect is due to incomplete charge induction by electrons and holes inside a plasma column, which has dielectricity-like property. Quantity of induced charge is shown in a ratio to the number of produced electron-hole pairs as functions of depletion layer thickness, plasma column length and resistivity of the detector. Experimental result of the residual defect of 58Ni ion and its analysis method applying this model are presented. The residual defect is successfully explained by this model.

Search for the cold fusion d(d, 4He) in electrolysis of D 2O

A search for high-energy α-particlesfrom the reaction d+d+Pd|Ti| → 4He+Pd′|Ti′| has been carried out using track detectors CR-39 and silicon surface barrier detectors. The upper limit of the investigated partial reaction rate has been estimated per deuteron pair: λ(d+d+Pd|Ti| → 4He+Pd′|Ti′|vb) ⩽ 8 × 10 −27 s −1 .

Restoration of the depth–concentration profile from the angle‐resolved relative intensities of x‐ray photoelectron spectra

AbstractA numerical method for the restoration of the depth–concentration profile from the angular distribution of XPS intensities is described. The proposed method is based on the regularization theory. A simpler formulation of the basic relationships than has been given in previous works2–8 enables the inclusion of more general a priori information. A new approach is also given for the choice of the most suitable profile for the experimental data, which enables restoration of profiles with up to two extremes. Calculations performed for all typical profiles show good agreement with the simulated data. The applicability of the method is demonstrated on the depth–concentration profile restoration of the SiO2/Si interface in the silicon surface barrier detector.

Dual silicon surface-barrier detectors and associated electronics for monitoring chemical separation of 249Cf and 249Bk

The isotopes 249Cf and 249Bk are chemically separated by ion-exchange chromatography at the Oak Ridge National Laboratory Transuranium Processing Plant. Control of the separation depends on the operator's ability to distinguish electronically between alpha radiation from the 249Cf and beta particles from the 249Bk. This new monitoring system consists of two surface-barrier detectors, each having its own channel of electronics and data acquisition. The two detectors are mounted in a Teflon holder and positioned near the tip of the ion-exchange column, where droplets of solution are formed as the nuclides are eluted from the column. Amplifier gain and window settings on the single-channel analyzer (SCA) for one detector are adjusted to count the energetic alpha particles from the 249Cf, while the electronic settings of the other channel are adjusted to count the lower-energy beta particles from 249Bk. The alpha count rate will increase first as 249Cf passes from the column; then the beta count rate increases, indicating that 249Bk is being eluted. At this point, the operator can make a cut in the separation process.

Excess noise of the silicon surface barrier detectors

From our experiments the following conclusions follow: i) The value of a in the l/fa law lies within the intervala e (0.6, 1.0). ii) The detectors featuring low reverse currentIc havea ≈ 1.0. iii) The cutoff frequency of the noise characteristicfc is at low frequency compared with the using frequency band of the detector. iv) The excess noise is given by generation-recombination process in the volume of the space — charge region of the sample.

Radiobiology of α Particles: I. Exposure System and Dosimetry

A 238Pu alpha-particle exposure apparatus was designed and constructed for use in radiobiological studies with cultured cell systems. The system provides a wide dynamic range of absorbed doses and a uniform radiation field. Average dose rate in air was measured with a small-volume ionization chamber. Estimates of dose rate at the cell surface were obtained from measurements taken with a silicon surface barrier detector. Particle fluence uniformity and fluence rate were measured using track etch procedures. The design and dosimetric characterization of the apparatus are discussed.

Charged particle spectra of palladium thin films during low energy deuterium ion implantation

An effort was made to create cold fusion in thin films of palladium under low energy bombardment with high currents of deuterium ions in a vacuum chamber. Samples were monitored with a silicon surface barrier detector in order to detect any massive energetic reaction products. The films were deposited by sputtering onto smooth silicon substrates, and consisted of approximately 130 A of palladium sandwiched by thin layers of high chrome stainless steel. These films were bombarded with deuterium ions at an energy of 1.5 keV with a current density of about 0.5 mA/cm2. The sample temperature was monitored during implantation, and was subject to some measure of control using a combination of beam heating and cooling with flowing liquid nitrogen. Several counts were observed to appear in the high energy region of the spectra which did not appear during an extended background spectrum, however, the source of these counts is unclear at this time.

The new nuclide230Pu

In the heavy-ion complete fusion reaction208Pb+26Mg at a beam energy of 135 MeV the new nuclide230Pu was produced. The measuredα-decay energy was found to be Eα=7050±15 keV. The new isotope was identified after in-flight separation with the kinematic separator VASSILISSA, followed by its implantation into a silicon surface-barrier detector and the observation of the genetic relationships of subsequentα-decays. The half-life of226U was measured more accurately.

Silicon detector for low-energy electron spectroscopy

A novel silicon surface barrier detector has been constructed for low-energy electron spectroscopy. This detector consists of a high-resistance silicon wafer which is sandwiched between a rectifying barrier front and ohmic back contacts. The front electrode is a gold mesh metallization with an effective area of 8% of the detector surface. This electrode allows most of the electrons to reach the active region of the detector with the smallest possible degradation in their energy distribution due to electron straggling in the front electrode.

X-ray detection efficiency of a silicon surface barrier detector using synchrotron radiation in the 0.06–0.9 keV energy region

Using synchrotron radiation from 0.056 to 0.900 keV, the detection efficiency of a silicon surface barrier (SSB) detector. η SSB, has been investigated. The experimental data are compared with the theoretically calculated results using the detector parameters of the depletion layer, the dead layer and the electrode. As a whole, the data points agree well with the theoretical results except for an oscillatory structure for the 0.07–0.17 keV region. In this energy region, sharp edge structures in η SSB are observed near the Al L II and L III absorption edges as well as the Al L I edge. In particular, this structure in η SSB near the Al L I edge is accompanied by an oscillatory behaviour like an X-ray absorption near-edge structure (XANES) on the high energy side of the edge.