This paper describes contributions to the workshop, 'Technology Development for a CMB Probe of Inflation,' held at NIST in Boulder CO, Aug. 25-28, 2008 concerning technologies to read out direct detectors (including bolometers and microwave kinetic inductance detectors) in a CMBPol satellite mission. The large number of polarimeters required for a satellite mission will likely make it necessary to multiplex the output signals into a small number of readout channels at the cold state. We describe both the cryogenic components and the present-generation warm readout electronics, consider the benefits and challenges of each option, and analyze their technology readiness level and needed additional investments.
We investigate the electronic structure of several double quantum dot systems: (i) hetero-dot artificial molecules built from two CdS chemically synthesized nanocrystals and (ii) two vertically stacked pyramidal self-organized InAs/GaAs quantum dots. The calculations are performed using the empirical tight-binding approach. The results of calculations show significant coupling between the nanocrystals that form a quantum-dot molecule. When two quantum dots are close enough, the strong coupling can split and reorder energy levels, change state symmetries and make substantial changes in optical spectra. Formation of double-dot states having bonding and antibonding character by analogy to diatomic molecules is shown.
We calculate the hadron bubble nucleation rate in the quark plasma after the quark-hadron phase transition within chiral models of QCD. The model parameters are constrained by the phenomenology of low energy hadron physics. It is found that for some of the values of the parameters in the ranges allowed by these constraints the bubble nucleation rate is strongly suppressed, resulting in a high degree of supercooling, indicating the possibility of forming large quark star-like objects.
Bone disease represents one of the most common diseases in the western world. Often the result is rarefied bone tissue, which leads to a loss in bone strength and is a precursor to clinical osteoporosis. Many different techniques have been used to determine the density of bone tissue at the most important clinical sites in the skeleton for diagnosis of the disease. Measurement of total attenuation or scattering of a radiation beam, attenuation of ultrasonic beams and the activation through neutron irradiation have all been used. This review first considers the skeletal changes that need to be monitored and then considers each technique in turn. When comparing the success of these different approaches accuracy, precision, site of measurement, patient convenience, sensitivity and radiation hazard must all be taken into account.
After a long period of mainly static application of ISFETS, other more sophisticated applications are being developed, based on the exploitation of the dynamic properties of ISFETS. Examples are the use of flow-through cells with sample injection and the integration of a pH actuator electrode for very fast titration in a microvolume. The development of an immunoFET makes use of induced transient phenomena.
A novel dual-wavelength thermal-lens spectrometer with pump/probe configuration that is capable of simultaneously measuring thermal-lens signals at two different wavelengths has been developed. In this instrument, the two excitation beams are derived from the same argon-ion laser operating in a multiline mode. The sample is excited by these two wavelengths alternately and the corresponding thermal-lens signals are monitored by a He-Ne probe laser. Advantages of this dual-wavelength apparatus include its inherent sensitivity and enhanced selectivity. The selectivity is improved because the ratio of the thermal-lens signals at the two different wavelengths provides fingerprints and allows identification of the sample. Therefore, it can be used not only to detect and identify trace chemical species at very low concentration but also to analyse two-component mixtures. Using this apparatus, the detection limit for NO2 using 30 mW excitation beams modulated at 4.6 Hz is estimated to be 300 PPB.
Ion implantation systems, used for producing high-current ion beams, employ wide-beam ion sources which are rotated through 90 degrees . These sources need mass analyser optics which are different from the conventional design. The authors present results of calculation of the image distance as a function of entrance and exit angles of a sector magnet mass analyser having such a source. These computations have been performed for the magnetic deflection angles 45 degrees , 60 degrees and 90 degrees . The details of the computations carried out using the computer program MODBEAM, developed for this purpose, are also discussed.
A method for narrowing the energy width of e+ and e- beams using a 22Na radio-isotope and a W moderator is developed. The method provides a width of about 1 eV for 10-20 eV beams, and is applied to inelastic scattering measurements on the Schumann-Runge excitation of an O2 molecule by e+ and e- impact. The ratio of the excitation cross section in O2 by e+ impact to that by e- is about 1.2 for impact energies in the range 13-22 eV.
A model has been developed, and tested experimentally, to account for the apparent dependence of the effective cross-sectional area of pistons in gas-piston-gauge pressure standards on the particular gas with which the gauge is operated, in the absolute mode. The model treats a pressure drop or loss that depends on the pressure difference across the gauge (P1-P2), the fall rate of the piston, the density of the gas and the viscosity of the gas. The model was tested using helium, neon, argon, nitrogen and krypton, and several values of (P1-P2). An algorithm was developed for calculating the piston cross-sectional area. The experimental results confirmed the model and resulted in a reduction in measurement uncertainty arising from this effect by approximately one order of magnitude.
PIN silicon photodiodes used with low-noise preamplifiers are an attractive alternative to photomultipliers in some industrial scintillation counters. They are compact, robust, stable and insensitive to magnetic fields. A high-voltage supply is not required and the photodiode and preamplifier may be battery operated. The energy resolution of a scintillation counter comprising a 10*10*20 mm3 CsI (Tl) scintillator coupled to a silicon photodiode has been compared with that of a similar counter using an identical crystal coupled to a photomultiplier, and with that of a conventional NaI(Tl) scintillation probe. The equivalent noise charge of the photodiode used with a cheap, hybrid, low-noise preamplifier is 470 e- RMS, with the result that the CsI(Tl) scintillator-photodiode combination has a better energy resolution than the equivalent photomultiplier-based counter for gamma-ray energies above 150 keV, and is better than the NaI(Tl) scintillation probe above 600 keV.
A new type of crossed-field energy filter for charged particles has been developed. It is intended for use with electron or ion beams that move in the direction of a uniform magnetic field and it employs mutually perpendicular transverse electric and magnetic fields. It can be regarded as a form of Wien filter immersed in a longitudinal magnetic field. By introducing an appropriate non-uniformity in either of the transverse fields the device is made stigmatic (double focusing). The focusing and dispersing properties have been determined by calculation of the first- and second-order transfer coefficients, and the dependence of these on the ratio of the longitudinal to transverse magnetic field has been found. The new analyser offers the important advantage of an in-line geometry. Its performance is compared with that of the trochoidal and stigmatic Wien filters. The transfer coefficients of the stigmatic Wien filter are also presented.
A system for the measurement of the Fourier components of low-level electrical signal is presented. The system has been applied to the measurement of the harmonics of the dynamic hysteresis loop of an amorphous material, finding a good correlation between the hysteresis loop obtained by conventional methods and the one reconstructed from the harmonics measurement. The theoretical limit of the system sensibility in magnetic flux measurement, assuming that the noise from the sense coil is sufficiently small to allow the most sensitive range of the lock-in amplifier used, is 1 nWb at 20 Hz.
A computerised phase-shifting speckle interferometer (PSSI) has been developed, capable of measuring deformations as well as vibrations. The performance of the PSSI is given by presenting results from experiments where simple objects have been deformed or excited. Algorithms used to calculate the amplitude of deformation or vibration are given. Results on properties affecting the performance of the input lens and CCD-array sensor are presented. A possible way to increase the lateral resolution is to place the narrow end of a tapered fibre-optic faceplate in the image plane, with the wide end focused on the CCD array. This increases the spatial sampling rate of the speckle pattern.
An oven design suitable for producing stable beams of highly reactive metals is reported. Its attraction is in its simplicity, low cost and versatility in molecular beam and atomic/molecular physics experiments involving highly reactive metals such as rubidium, caesium, etc. An application is described for the case of atomic caesium, where the metal is produced by the chemical reaction Ba(s)+CsCl(s) to BaCl(s)+Cs(v). One of the main advantages of the present design is the use of a thin-walled, stainless steel pipe, as crucible and heater simultaneously, which considerably simplifies its design. With respect to the experimental method, the simplicity in the loading, working and cleaning procedures compared with the use of pure metal should be noted.
Characteristics of different analogue bandpass-filter banks generating power spectra with a logarithmically uniform frequency resolution and a constant relative analysis band-width are discussed. Equivalent digital filters are derived for use with digital spectrum analysers. As an example of application, an algorithm for digital third-octave band analysis is demonstrated and used for the evaluation of fluctuation power spectra characterising the real part of the impedance of standard RC circuits.
Traditionally, rigid endoscopes employed relay systems consisting of doublet relay objectives and singlet field lenses, until about 1960 when the rod-lens relay system was invented and led to the manufacture of endoscopes with much improved light throughput and image quality. The authors review these systems and describe the design of a new type of rod-lens relay system which employs an 'air-lens triplet' as the relay objective. This new system has greatly improved correction of astigmatism and field curvature, even when compared with the rod-lens relay system. Constructional data are given for the optical system of a laparoscope which uses the new 'air-lens triplet' relay system. The magnitude of the improvement in image quality, particularly for closed circuit television (CCTV) and photography, is demonstrated by a comparison of calculated modulated transfer function (MTF) results.
A simple modification of a test-cell which enables the field dependence of the complex susceptibility of ferrofluids to be measured at fields up to 40 kA m-1 is reported. The technique may be used for much larger fields.
