Scintillation detectors systems

The concrete block walls of the cell housing the generator tube and associated components are 1.7 meters thick. The facility also includes a Kaman Nuclear dual-axis rotator assembly for simultaneous transfer and irradiation of reference and unknown sample, and a dual Na iodide (Nal) scintillation detector system designed for simultaneous counting of activated samples. Automatic transfer of samples between load station to the rotator assembly in front of the target, and back to the count station, is accomplished pneumatically by means of two 1.2cm (i.d.) polyethylene tubes which loop down at both ends of the system and pass underneath the concrete shielding thru a pipe duct. Total one-way traverse distance for the samples is approx 9 meters. In performing quantitative analysis for a particular element by neutron activation, the usual approach is to compare the count rates of an unknown sample with that of a reference standard of known compn irradiated under identical conditions... 

The expts were conducted in stainless steel sigma-blade type mixers with proplnt mixing capacities of 60, 600 and 2000 lbs, respectively. Radioactivity measurements on samples taken from various locations in the batch at different mixing times were performed with a sodium iodide scintillation detector system... 

The Berthold radioactivity monitor (produced by Laboratorium Prof. Dr. Berthold, D-7547, Wildbad 1, Calmbacher Strasse 22) is the only on-line radiometric scintillation detection system suitable for HPLC that is commercially available. The monitor is offered with cells for heterogeneous scintillation counting or as pert of a homogeneous scintillation detector system. Flow cells filled with glass... 

In comparison with the other sources of uncertainty discussed above, electronic noise in scintillation detector systems is a minor problem. More important, as we shall see, is gain drift caused by instability in the high-voltage supply. The priorities when selecting electronic modules for scintillation counting are somewhat different from those which determine a system for high-resolution (semiconductor) spectrometry. 

Figure 2.81 (a) Schematic of the system for in situ X-ray reflectivity measurements. Syn = synchrotron source M = monochromator S = slit /0, /R = incident and reflected X-rays beams, respectively 9 = angle of incidence W = teflon windows WE = working electrode RE = reference electrode CF = counter electrode D = scintillation detector, (h) Cyclic voltammogram of Cu-on-Si electrode in borate buffer solution (pH 8.4), scan rate = lOmVs-1. From Melendres... 

The conditions for Pu reduction and elution were examined in detail, and a variety of reducing agents were tested.82 A flow system with an on-line scintillation detector was used to show the elution behavior in detail under well-controlled flow conditions. It was found that reduction and elution with hydroquinone was slow, resulting in broad tailing peaks and incomplete reduction. Some Pu remained in the Pu(IV) state and could be eluted with a complexant on completion of the reductant/HCl elution step. However, by choosing other reductants, rapid reduction and clean elution as a sharp peak could be obtained. These results are shown in Figure 9.14. 

It is also interesting to note that the limitations of most neutron systems lie not in the neutron source(s) but rather in the (gamma ray) detectors and subsequent data acquisition system. The obvious need is for development of detectors with higher rate capability and improved energy resolution. All modern digital data processing techniques have allowed significant improvement in the performance of conventional scintillation detectors with respect to rate and pileup rejection. 

A modern Pb/scintillating fiber detector system, incorporating a Loran frequency standard, capable of measuring time intervals with a precision of 20 ps. 

With modem Vidicon tubes the spatial resolution power of a detector system is predominantly determined by the optical properties of the scintillator. 

The experimental equipment requires a standard fine structure X-ray generator operated usually with monochromatic K -radiation. The measurements of the refraction effect are taken by using a commercial small angle X-ray camera of the Kratky type in combination with two scintillation detectors for simultaneous detection of X-ray refraction intensity Ir and sample absorption U- A standard DOS-computer handles the scattering intensity data acquisition and the micromanipulator scanning-system. Figure 1 shows the experimental setup. 

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