122338314
Silicon detectors: New challenges
Abstract An introduction is given to the areas of current interest in silicon radiation detector design and fabrication. Problems associated with detector grade silicon are reviewed. Passivation of detector surfaces with silicon dioxide or amorphous silicon is described. Two examples of silicon detector applications in X-ray detection and X-ray angiography are presented.
15936884
Pulsed Power Supplies for the Fermilab 1 TeV Switchyard
An upgraded system of pulseed switching magnets has been implemented in the Fermilab Switchyard to accommodate proton energies up to 1 TeV. These devices are required for switching the ''slow'' and ''fast'' extracted beams into their respective beam lines. ''Slow'' beam passes undeflected through the magnet in the off condition. During a puls ''slow'' is disabled and ''fast'', which is of approx.1 ms duration, is deflected. The requirement then is for a ''flat-top'' current pulse of minimum rise and fall time. The circuit chosen is of the resonant charge recovery type. Several different styles and combinations of magnets and constraints. In all cases maximum voltage is limited to 600 volts and pulse width to 100 ms.
195865490
Determination Of Surface Recombination Velocity And Bulk Lifetime In Detector Grade Silicon And Germanium Crystals
The utility of a noncontact photoconductive decay (PCD) technique is demonstrated in measuring the bulk lifetime, zs, and surface recombination velocity, S, in detector grade silicon and germanium crystals. We show that the simple analytical equations which relate the observed effective lifetimes in PCD transients to ze and S have a limited range of applicability. The noncontact PCD technique is used to determine the effect of several surface treatments on the observed effective lifetimes in Si and Ge. A degradation of the effective lifetime in Si is reported as a result of the growth of a thin layer of native oxide at room temperature under atmospheric conditions.
118092727
Optical measurement of SSC ARC quadrupole cold mass location
The operation of the collider requires that the ARC quadrupoles’ beam center and rotational configuration be held to the tight tolerances of 0.2 mm rms and 0.5 mradian rms. The design of the collider superconducting magnets prevents direct access to the cold mass during operation. As a result, cold mass position is inferred from the relationship established by warm measurements relative to a secondary fiducial located on the vacuum vessel and an offset (warm to cold correlation) to account for the position change for a cold magnet. There is concern that the relation of these fiducials to the magnet centerline may change unpredictably due to the temperature drop required for superconducting operation or due to long term creep. This paper reports on a design that will allow visual observation of the cold mass shell position and roll orientation under cold as well as warm conditions.
117857758
Development of silicon drift detectors for strangeness measurements
Detection of multi‐strange and charm particles requires precise measurements of the secondary vertices close to the interaction point and the decay products of strange and charm particles. This presents an unprecedented challenge for relativistic heavy ion experiments, where multiplicity reaches thousands of final state particles per collision. Development of affordable technology for realizing high spatial resolution and low mass vertex detectors has become the ultimate goal of many R&D projects in major laboratories. In this paper we present preliminary results on silicon drift detectors fabricated for the first time on p‐type silicon substrates. These detectors were designed, fabricated and tested recently at LBL and show very interesting properties which make their use in future experiments very likely.
119775934
Progress in semiconductor drift detectors
Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements.
85521425
Spectroscopy of Ba and Ba + deposits in solid xenon for barium tagging in nEXO
Progress on a method of barium tagging for the nEXO double beta decay experiment is reported. Absorption and emission spectra for deposits of barium atoms and ions in solid xenon matrices are presented. Excitation spectra for prominent emission lines, temperature dependence and bleaching of the fluorescence reveal the existence of different matrix sites. A regular series of sharp lines observed in Ba$^+$ deposits is identified with some type of barium hydride molecule. Lower limits for the fluorescence quantum efficiency of the principal Ba emission transition are reported. Under current conditions, an image of $\le10^4$ Ba atoms can be obtained. Prospects for imaging single Ba atoms in solid xenon are discussed.
85509783
An RF-only ion-funnel for extraction from high-pressure gases
An RF ion-funnel technique has been developed to extract ions from a high-pressure (10 bar) noble-gas environment into a vacuum (10(-6) mbar). Detailed simulations have been performed and a prototype has been developed for the purpose of extracting Ba-136 ions from Xe gas with high efficiency. With this prototype, ions have been extracted for the first time from high-pressure xenon gas and argon gas. Systematic studies have been carried out and compared to simulations. This demonstration of extraction of ions, with mass comparable to that of the gas generating the high-pressure, has applications to Ba tagging from a Xe-gas time-projection chamber for double-beta decay, as well as to the general problem of recovering trace amounts of an ionized element in a heavy (m > 40 u) carrier gas. (C) 2015 Elsevier B.V. All rights reserved.