High resolution silicon detectors for colliding beam physics

Resolution and linearity of the position measurement of Pisa multi-electrode silicon detectors are presented. The detectors are operated in slightly underdepleted mode and take advantage of their intrinsic resistivity for resistive charge partition between adjacent strips. 22 μm resolution is achieved with readout lines spaced 300 μm. Possible applications in colliding beam experiments for the detection of secondary vertices are discussed.     

Gel electrode imaging of fatigue cracks in aluminium alloys

Previous papers have described a gel electrode technique recently devised for detecting and imaging fatigue cracks in aluminium tested in simple bending. In this study, the technique is shown to be applicable to testing in both bending and torsion and to high strength aluminium alloys 7075-T6, 2024-T3 and 2024-T4. Fatigue cracks as short as 10 μm in length are consistently detected and located. The flow of charge during image formation under standard conditions provides a quantitative measure of crack length, which is independent of alloy composition. A crack 100 μm long can be reliably detected by charge flow measurement; thus, this approach is not as sensitive as the information contained in the actual images.     

Book Review

Triboelectrification affects particle adhesion and agglomeration and hence the formulation, manufacture, and use of dry powder inhaler (DPI) devices. Electrostatic charge measurement of two component mixes of spray-dried or crystalline lactose fine particles (<10 μm) 0, 5, 10, 15, 20, and 30% w/w with spray-dried or crystalline lactose 63–90 μm, respectively, has been undertaken using a system incorporating pneumatic transport of the mixed powders to a stainless steel cyclone charging device. The magnitude of charge on the mixes was shown to decrease with increased fine particle content, and there was no significant difference in charge for each concentration between spray-dried and crystalline lactose. Both the variation of charge and powder adhesion to the cyclone surface increased with increase in fine particle content. The proportion of fine particles in carrier systems in DPIs may thus have an important role where triboelectrification is involved.     

Synthesis of nanocrystalline SiC at ambient temperature through high energy reaction milling

This study investigated the in-situ synthesis of nanosized crystalline SiC powders at room temperature through high energy ball milling of elemental silicon and carbon mixtures. Milling conditions including the mill design, the milling speed, the milling time and the ball-to-powder weight ratio (i.e. the charge ratio) necessary for the in-situ synthesis were studied. It was found that uniform formation of nanosized crystalline SiC powders within the powder charge could be achieved with a correctly designed attritor and the contamination could be minimized with proper selections of milling conditions. The crystalline β-SiC powders synthesized were themselves in nanosize scale, quite different from many previous studies which have shown that it is the internal grain structure of milled powders that is the “nanocrystalline” component of the powders (typically 5–20 nm), while the powders are themselves typically 0.1 μm to > 1 μm in size. Furthermore, it was found that the product structures generated by high energy reaction milling depended strongly on the milling speed, the charge ratio and the milling time.     

First results from a silicon-strip detector with VLSI readout

A 256-strip silicon detector with 25 μm strip pitch, connected to two 128-channel NMOS VLSI chips (Microplex), has been tested using straight-through tracks from a ruthenium beta source. The readout channels have a pitch of 47.5 μm. A single multiplexed output provides voltages proportional to the integrated charge from each strip. The most probable signal height from the beta traversals is approximately 14 times the rms noise in any single channel.     

Cover Picture: Microscopic Evidence for Spatially Inhomogeneous Charge Trapping in Pentacene (Adv. Mater. 11/2005)

Trapped charge has been observed in polycrystalline pentacene films by electric force microscopy in work reported by Muller and Marohn on p. 1410. The cover shows an optical fiber watching the motion of a metal‐coated cantilever hovering over a polycrystalline pentacene film. The film occupies the 6.5 μm gap in a working field‐effect transistor. Trapped charge (dark blue and black areas in the pentacene) appears as large patches randomly distributed throughout the device, implying that long‐lived traps in polycrystalline pentacene are not correlated with grain boundaries.     

Investigation of Charge Transfer Kinetics of Polyaniline Supercapacitor Electrodes by Scanning Electrochemical Microscopy

Scanning Electrochemical Microscopy (SECM) is introduced as a promising technique to probe localized interfacial kinetics at the interface of electrolyte/supercapacitor electrode based on polyaniline (PANI) by measuring approach curves from which heterogeneous charge transfer rate constants (k _eff) are extracted. The values correlate with the effectiveness of the electrode material for supercapacitor application. Specifically, measurements on PANI films of different thicknesses show that potential‐dependent rate constants are observed only for PANI films of up to 5 μm thickness. In addition to the thickness of PANI, k _eff is also found to be affected by the applied potential and surface morphology of PANI electrodes. These findings correlate with the macroscopic electrochemical performance of PANI electrodes which shows enhanced specific charge storage ability when their thickness is below 5 μm. Under these conditions, they deliver a specific capacitance of 486 F g⁻¹ and a rate capability of 89%. The observed correlation between microscopic kinetic data determined by SECM and macroscopic device characteristics provides rational guidelines for the optimization of the physical and structural properties of high performance supercapacitor electrodes.     

Thick oxide pMOSFET dosimeters for high energy radiation

This work examines the response of pMOSFET dosimeters to ionizing radiation. The dosimeters were fabricated with gate oxides having a range of thicknesses varying from 0.69 μm for the thinnest oxide up to 2.3 μm for the thickest oxide. In separate experiments the dosimeters were irradiated by ⁶⁰Co γ-rays and linac X-rays both with biassed and unbiassed gates. The effects on transistor characteristics were measured and analysed to show the relative contributions to the shift in the threshold voltage from trapped charge in the oxide and charges trapped at the silicon-silicon dioxide interface.     

A study of the detection accuracy of proportional chambers with cathode read-out

Results are presented of a study of the accuracy in detecting relativistic particle coordinates in proportional chambers using the cathode information read-out. The width of the cathode strips was 2 mm and the anode to cathode distance 4 mm. For the tracks perpendicular to the chamber plane the detection accuracy was 50 μm. Two methods of calculation of the centre of the induced charge distribution on the cathode strips are described: by the centre of gravity and by fitting this distribution by a special formula. It is shown that for single-particle events the change of the width of the induced charge distribution does not exceed 1.2%.     

糊精氮化铅球形化工艺参数的研究

通过起爆药在有机玻璃管壳中压药上浮试验和流散性测定,发现球形糊精氮化铅中粒径<45μm颗粒的含量增多,使药剂装药性能下降、流散性变差,压药容易上浮;频繁压爆、毫秒延期电雷管瞬爆是压药上浮所致。提出两项质量控制指标：药剂堆积密度≥2.00 g/cm3;粒径<45μm颗粒的质量分数≤20％。工艺参数：3％(质量分数)氮化钠溶液加入8％(质量分数)硝酸铅溶液,水药质量比30︰1,工业酸性糊精质量分数(外加)5％,氮化钠溶液碱度0.080％,化合温度60℃。保持一定的加料速度和搅拌强度,能稳定生产出满足雷管装配需求的起爆药。     

Control of electrostatic charge on particles by impact charging

The control of electrostatic charge on particles in gas–solids pipe flow has been studied experimentally and theoretically. Alumina particles of 3.3 μm in count median diameter were dispersed in airflow and pneumatically transported in the dilute phase. Five different materials were used for the transport pipes, and the relationships between the particle charge and the pipe length were obtained. The polarity and the amount of particle charge were found to depend on the pipe material and the length. In order to control the particle charge, a system combining two different pipe materials was proposed depending on the particle-charging characteristics. The charge controlled by this method was in good agreement with the theoretical calculation. Furthermore, it was found that the distribution of particle charge as well as the average can be controlled.     

Electrical conduction in solution-grown polycarbonate films

The electrical conduction in solution-grown polycarbonate films was studied at different voltages between 1 and 10⁴V as a function of thickness from 25 to 65 μm at a constant temperature of about 385 K and as a function of temperature in the range 328–430 K at a constant thickness of about 50 μm. The results show two distinct regions corresponding to different types of conduction: region I at low or moderate fields where the slope of the current-voltage characteristics is about 2 and region II at high fields where the slope is about 4. The Richardson-Schottky effect was suggested as the dominant mode of conduction at moderate fields whereas at high fields the currents were found to be space charge limited.     

CDF central muon detector

Design, construction and performance characteristics of the streamer chambers for the central muon detector at CDF are described. A single hit TDC is used for measurements in the drift (azimuth) direction while charge division is used for measurements along the sense wire (pseudorapidity). The chambers operate in the limited streamer mode with a 50%/50% ratio of argon/ethane bubbled through ethanol. Measurements in a cosmic ray test stand, pion test beam and as part of the CDF detector indicate that an rms resolution of 250 μm in the drift direction and an rms resolution of 1.2 mm along the sense wire are attainable.     

Optimal foil material and thickness for the charge striping of heavy ions of around 100 MeV

In order to seek an optimal charge stripping material and its thickness for the charge stripping of heavy ions of around 100 MeV, the transmission of highly charged ions after passage through charge stripping foils has been measured using 95 MeV Cl ions. Tested foils are Be and C foils of various thicknesses. As a result, Be foils with several tens of μg/cm² are most efficient for the obtainment of highly charged ions whose charge states are higher than the most probable charge state. On the other hand, for the use of ions with the most probable charge state, there is no noticeable difference between the use of C and Be foils provided that their thicknesses are a few tends of μg/cm².     

Electric field dependent photocurrent decay length in single lead sulfide nanowire field effect transistors

We determined the minority carrier diffusion length to be ～1 μm in single PbS nanowire field effect transistors by scanning photocurrent microscopy. PbS nanowires grown by the vapor-liquid-solid method were p-type with hole mobilities up to 49 cm(2)/(V s). We measured a photoresponse time faster than 14 μs with near-unity charge separation efficiency at the contacts. For the first time, we also observed a field-dependent photocurrent decay length, indicating a drift dominant carrier transport at high bias.     

Layered nanocomposites from gold nanoparticles for neural prosthetic devices

Treatments of neurological diseases, diagnostics of brain malfunctions, and the realization of brain-computer interfaces require ultrasmall electrodes that are "invisible" to resident immune cells. Functional electrodes smaller than 50 μm are impossible to produce with traditional materials due to high interfacial impedance at the characteristic frequency of neural activity and insufficient charge storage capacity. The problem can be resolved by using gold nanoparticle nanocomposites. Careful comparison indicates that layer-by-layer assembled films from Au NPs provide more than 3-fold improvement in interfacial impedance and 1 order of magnitude increase in charge storage capacity. Prototypes of microelectrodes could be made using traditional photolithography. Integration of unique nanocomposite materials with microfabrication techniques opens the door for practical realization of the ultrasmall implantable electrodes. Further improvement of electrical properties is expected when using special shapes of gold nanoparticles.     

MEASUREMENT AND CONTROL OF ELECTROSTATIC CHARGES ON PULVERIZED COAL IN A PNEUMATIC PIPELINE∗

Abstract

Pulverized coal particles flowing in a pneumatic pipeline are naturally charged to a detectable level due to collisions with pipe walls. Systematic charge measurements of Anthracite (AN) coals, Medium Volatile Bituminous (MVB) coals and Lignite A (LIGA) coals in a grounded copper pipe have been made with an upgraded charge measuring system. The net particle charges were found to be positive, although both negative and positive charges were detected in all experiments. Effects of air humidity and conveying velocity on particle charges were examined. The mean particle charge was found in the order of 10^?12 Coulomb and the charge-to-mass ratio in the order of 10^?5 C/kg. Charge elimination techniques by strict humidity control and by introducing neutralizing charge carriers, such as minus 1 μm activated charcoal fines, ammonia, and piezoelectric ionized gas were explored. Effective reduction of 70 % to 85 % of particle charges was achieved. A charge neutralization mechanism was proposed to interpretate the measured results.     

Deposition from an r.f. induction source of aluminum-copper alloys onto laminated polyimide substrates

A physical vapor deposition process with an r.f. induction vapor source was developed to deposit an aluminum-copper alloy 11.2 μm thick onto laminated polyimide substrates. The average thickness uniformity (the standard deviation divided by the average thickness), which was obtained using a beta backscatter technique, was approximately 1% for these deposits. The Al-0.3 wt.% Cu vapor charge resulted in a copper content in the deposit of 0.12 wt.%. The copper showed no preferential deposition pattern, as related to the surface of the laminate and its dispersion throughout the deposit. The resistivity of the aluminum-copper deposits was 3.0 μΩ cm and was stable from one deposition run to another. Also the resistivity was not related to the geometry of the domed substrate. The density of the aluminum-copper film 11.2 μm thick was within 1% of the theoretical density, and the film adhesion to the polyimide exceeded that required for post-deposition operations and handling. The deposited films exhibited a specular reflectance of above 90% using a source of wavelength 632.8 nm and had a grain size of 0.6 μm throughout the deposit.     

Design of a low noise,self-triggered,monolithic preamplifier dedicated to silicon trackers and X-β imaging

A monolithic and triggerable charge amplifier has been implemented in a 1.2 μm CMOS technology. Initially developed for the LEP-DELPHI spectrometer (CERN), this architecture is also potentially useful for X and β imaging due to its noise performances (ENC = 110 e⁻ rms + 10 e⁻ rms/pf), low power consumption (Pd = 1.5 mW/channel), internal triggerability and shaping time adjustability between 1 and 2 μs.     

Pore filling of nanostructured electrodes in dye sensitized solar cells by initiated chemical vapor deposition

The dye sensitized solar cell (DSSC) operation depends on a liquid electrolyte. To achieve better performance, the liquid should be replaced with a solid or gel electrolyte, e.g., polymers. Here, we demonstrate initiated chemical vapor deposition as an effective liquid-free means for in situ polymerization and pore filling. We achieve complete pore filling of 12 μm thick titania resulting in enhanced cell performance that is attributed to reduced charge recombination at the electrolyte-electrode interface.