Pulse Height Defect Research Articles

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.

The effect of heavy-ion irradiation on an implanted-Si position-sensitive detector

Characteristics of an implanted-Si position-sensitive detector, which was designed for the Coulomb excitation experiment with NORDBALL, were investigated while varying the amount of the heavy-ion flux injected into the detector. Marked effects on the pulse height defect as well as increased reverse current were observed around a fluence of 1.5 × 10 9 particles/cm 2. Under the same condition, severe deterioration of the position spectrum was not observed.

On the calibration of low-energy ion accelerators

The pulse height measured in a silicon detector for MeV 4 He ions backscattered from a monoisotopic target, e.g. Au, has been compared to that from a radioactive 241 Am source. Using previous results for the so-called “pulse height defect”, including the effects of nonlinear detector response, we have determined the incident beam energy at ∼ 2.4 MeV with a precision of ∼ 3 keV. The data are in good agreement with a calibration performed using the 27 Al(p, γ) 28 Si nuclear reaction resonance technique.

Pulse height defect in an ionization chamber investigated by cold fission measurements

The cold fragmentation of 235U thermal neutron fission has been studied in a twin ionization chamber working with pure methane gas. Due to the very high fragment mass resolution, a careful investigation of the pulse height defect in this detector has been achieved. No dependence of the pulse height defect on the fragment mass has been observed. Therefore, it is easy to calibrate the energy response of such a detector. An accurate calibration method is proposed.

Pulse height defects for 16O, 35Cl and 81Br ions in silicon surface barrier detectors

Abstract The total pulse height defects (PHDs) of a silicon surface barrier detector (SSBD) for 16 O, 35 Cl and 81 Br ions in the energy range 2–40 MeV have been measured. To evaluate the contribution E w of the dead layer, its thickness was measured using α-particles. The nuclear defect E n was calculated in first-order approximation, using Ziegler's values [J.F. Ziegler, J.P. Biersack and U. Littmark, The Stopping and Ranges of Ions in Matter, vol. 1 (Pergamon Press, New York, 1985)] for both the nuclear and the electronic stopping powers, and the results are compared with other calculations of E n . The observed total defects could be essentially accounted for by E w + E n , suggesting that E r , the contribution due to residual defects, is small, in agreement with estimates based on the plasma recombination model [E.C. Finch et al., Nucl. Instr. and Meth. 163 (1979) 467].

The detection of heavy ions with PIN diodes

Abstract The pulse height defect (PHD) and the resolution (ΔE) of a low-cost PIN photodiode (Hamamatsu Model S 1223-01) have been studied for 11B (0.2–16.2 MeV), 35Cl (1.0–8.2 MeV) and 81Br (0.5–8.0 MeV) ions, and found comparable to those of ORTEC silicon surface barrier detectors. The major contribution to the difference in performance of the PIN diode may come from the surface dead-layer which was measured to be 90 ± 11 nm. The dependence of diode properties on the bias voltage shows that even at 0 V the relative pulse height is ≥95% of the value of saturation which is attained within 5 V. The relative resolution (ΔE/E) is nearly constant for all bias values up to 30 V (maximum reverse bias). Some preliminary results on the effect of radiation dose on the leakage current are also presented. These results demonstrate that the low-cost PIN diode can be successfully used as a charged-particle detector in applications such as ion beam analysis (RBS, HIRBS, ERD) and space technology.

Heavy-ion energy resolution of SSB detectors

The energy resolution of the silicon surface barrier detectors currently used for ERD (elastic recoil detection) and HIRBS (heavy-ion Rutherford backscattering spectroscopy) limits both the mass and depth resolution achieveable. Although the timing properties and pulse height defect of SSBDs have been well documented, only limited studies of their heavy-ion energy resolution in the energy range 5–20 MeV were available. Data on the energy resolution and line shape of two Ortec BA-017-100-100 detectors are presented and compared with a survey of SSB detector resolution data available in the literature.

Systematic measurements of pulse height defects for heavy ions in surface barrier detectors — A comment

Newly published data on the pulse height defect and its field dependence in heavy ion surface barrier detectors are reported by Oginara et al. to be in conflict with previous models developed by us. We show that this apparent discrepancy is due to the use by them in our models of inappropriately chosen parameters.

Bragg peak spectroscopy of low-energy heavy ions

A small ionization chamber with the electric field lines parallel to the particle trajectory (Bragg ionization chamber) allowing the determination of the nuclear charge and the energy of low energetic heavy ions ( E A ∼ 0.8–2.0 MeV ) is presented together with an adapted shaping amplifier. Using the customary technique of pulse shaping with a long and a short time constant the energy and the Bragg peak resolutions for projectiles between 2 4He and 16 32S were determined. With purified n-pentane an energy resolution of ΔE E = 1.0% and a nuclear charge resolving power of Z ΔZ = 47 were measured for 1.5 McV/amu 28Si ions elastically scattered on 197Au. No significant pulse height defect is observable for the energy determination of particles with Z ≦ 17. The Z resolution obtained via Bragg peak measurements was found superior to the Z determination using energy loss measurements which at low energies, in particular, suffer from large uncertainties due to straggling.

Systematic measurements of pulse height defects for heavy ions in surface-barrier detectors

The pulse height defect (PHD) in several Si-surface-barrier detectors for 12C, 16O, 28Si, 63Cu, 79Br and 127I ions was measured. The electric field strength dependence as well as the energy dependence were investigated. The results are compared with the recombination model. An empirical formula that describes well the total PHD is suggested.

The Use of Cf-252 to Measure Latchup Cross Sections as a Function of LET

Latchup cross-section measurements of HM6504, HM6641, HD6434, and HM6516, all CMOS devices were performed at various values of LET near threshold by adjusting the air pressure between the source and device. The energies of representative light and heavy fission fragments at the device were determined using an analytical approach which was considered preferable to spectrum measurements if the pulse-height defect in a silicon detector is unusually large.

Radiation damage effects in tritium implanted Si(Li) detectors

Tritium implanted Si(Li) detectors suffer from the effects of radiation damage during the implantation. These effects are manifested as a pulse height defect and as a broadening of the response function, and thus cause problems in the determination of the tritium beta end-point energy and in the determination of the electron antineutrino mass from the shape of the spectrum near the end point. We use simple models of the trapping of charge carriers to illustrate some of these problems.

Precision in neon ion energy loss measurements with a silicon surface barrier detector

Neon ions were accelerated to energies between 1.5 and 3.0 MeV. Pulse height distributions were measured with a silicon surface barrier detector both for directly incident ions and for ions transmitted through carbon foils. Detector line shapes are skewed with widths of about 100 keV (fwhm) and are not strongly dependent on energy or energy loss. The impact of line shapes on thickness resolution in energy-loss radiography is discussed. Information is developed for detector pulse height defect for neon ions and for neon ion stopping powers in carbon.

The application of empirical calibration procedures for heavy ion surface barrier detectors to pulse height defect mass dependence data

The pulse height defect mass dependence at constant energy for heavy ion surface barrier detectors is used as a parameter to compare fission fragment data with two empirical detector calibration schemes. The usefulness and limitations of these schemes are discussed.

Response studies on silicon surface barrier detectors for low energy ion spectrometry in space

Accurate measurements of the three-dimensional directional distribution of low energy ions in space require a careful calibration of the silicon surface barrier detectors mostly employed. This paper describes a systematic search for the pulse-height defects in the detector response to protons in the 25–150 keV energy range. The results ensured a proper pre-flight calibration of the ISEE-3 proton spectrometer and also allow some conclusions on the ratio of the average energies ϵ p and ϵ e− expended for electron-hole pair generation in silicon.

Study of the asymmetrical response of silicon surface barrier detectors to MeV light ions. Application to the precise analysis of light ions energy spectra I. Helium ions

The response of silicon surface barrier (SSB) detectors to light ions ( 3He, 4He, 12C, 14C, 16O, 20Ne) was investigated using a 2 MV Van de Graaff. In this paper, the results for He ions in the 0.5 MeV to 3.3 MeV energy domain are presented. Pulse height defects (PHD) were measured with respect to the proton response mean amplitude. For a detector with 40 μg cm −2 gold layer, a small PHD was observed ranging from 15 keV at 0.5 MeV to 8 keV at 1.6 MeV. For another similar detector, a slightly negative PHD was observed above 1.4 MeV. All the response peaks are asymmetrical with a low energy tail. Once the electronic noise contribution is removed, the skewness of the peaks obtained for helium ions is close to those of the heavier ions, γ 3 ≅ −1.2. The noise corrected widths of the helium response peaks range, for a 20 μg cm −2 gold layer convered detector, from 5.7 keV at 0.5 MeV to 8.3 keV at 3.3 MeV. All the peaks can be fitted accurately by the convolution product of a gaussian with a one-sided exponential factor.

Channeling effect in the dead layer of ion implanted, position-sensitive detectors in heavy-ion studies

Channeling in the dead layer and surface region of ion-implanted, position-sensitive detectors used in heavy-ion studies may lead to marked high energy tailing effects being recorded in the energy spectra. This results predominantly from the lower value for dE dx in the dead layer with a small contribution from a reduction of the recombination component of the pulse height defect. Knowledge of the crystal orientation of the detector material and care in the associated alignment are demanded, especially when used in detection geometries having a large angular acceptance, where the particle angle of incidence varies considerably across the active length of the position-sensitive detector.

The response of silicon position sensitive detectors to heavy ions

The pulse height response characteristics of surface barrier and ion implanted position sensitive detectors have been measured. Surface barrier detectors with junctions formed using oxidation by potassium dichromate exhibit small heavy ion pulse height defects indicating thin entrance windows. Ion implanted detectors give considerably larger defects because of penetrating tails in the distribution of implanted ions and electrically active defects.

The pulse-height correction technique for improving γ-ray spectra from coaxial Ge detectors

We demonstrate that the pulse-height correction technique can be used for coaxial as well as planar Ge γ-ray detectors. Pulses from the detectors are analyzed according to their rise-times, and an improved spectrum is obtained by correcting the incompleteness of charge collection, using the relation between rise-time and pulse-height defect. Geometrical effects in coaxial detectors require at least a three-parameter correlation, in which the rise-times of the pulses are analyzed for two time segments. We have been able to improve the energy resolution of neutron-damaged Ge detectors by more than 50% and their peak-to-Compton ratios by almost as much, all without significant loss in detector efficiency.