PIPS detector

A He(KCl)-jet transportation system was used for the transfer of the activities. The KC1 aerosol with the reaction products was collected by impaction on a Pt or Teflon slip for 60 or 90 s, was picked up with lOpL of the aqueous phase and was transferred to a 1 mL centrifuge cone containing 20 iL of the organic phase. The phases were mixed ultrasonically for 5 s and were centrifuged for 10 s for phase separation. The organic phase was transferred to a glass cover slip, was evaporated to dryness on a hot plate, and was placed over a passivated ion-implanted planar silicon detector (PIPS). This procedure took about 1 min. 

PIPS-detector Electrostatic spectrometer or time-of-flight... 

LEIS the energies of the ions are too low for PIPS detectors and would lead to a sig-nal-to-noise ratio less than unity. A stack of microchannel plates is, therefore, used to detect the ions in LEIS. The detection efficiency of the microchannel plates is included in the experimental transmission factor Tin Eq. (3.34). 

Egorov, O. B., Addleman, R. S., O Hara, M. J., Marks, T., and Grate, J. W., Direct measurement of alpha emitters in liquids using passivated ion implanted planar silicon (PIPS) diode detectors, Nucl. Instrum. Methods Phys. Res., Sect. A, 537, 600-609, 2005. 

Adsorption of Hg nuclides on silicon detectors, as in the successful experiment with Hs04, proved experimentally not feasible, since Hg was adsorbed on quartz surfaces only at temperatures of -150 °C and below. However, Hg adsorbed quantitatively on Au, Pt, and Pd surfaces at room temperature. As little as 1 cm2 of Au or Pd surface was sufficient to adsorb Hg atoms nearly quantitatively from a stream of 1 1/min He. Therefore, detector chambers containing a pair of Au or Pd coated PIPS detectors were constructed. Eight detector chambers (6 Au and 2 Pd) were connected in series by Teflon tubing. The detector chambers were positioned inside an assembly of 84 3He filled neutron detectors (in a polyethylen moderator) in order to simultaneously detect neutrons accompanying spontaneous fission events, see Figure 27. 

Fig. 27. Detector arrangement for the detection of 283112 consisting of pairs of Au and Pd coated PIPS detectors inside an assembly of 84 3He filled neutron detectors. Photograph reproduced from [109].

In a next experiment, the question whether element 112 remained in the gas phase and passed over the Au and Pd surfaces was addressed [110]. Therefore, a special ionization chamber to measure a-particle and SF fragments of nuclei remaining in the gas was added at the exit of the Au or Pd coated PIPS detector array. 

These detectors are thin (>500pm) discs of passivated, implanted planar Si (known also as PIPS detectors) for beta and high-energy positron detection they have extremely thin entrance window regions, not deposited metallic films but an ion-implanted region. A detector of active area 50mm2 can detect positrons above 18 keV, with an energy resolution of 6 keV [23]. 

The ICP-SFMS instrument was tuned using a I ng mf uranium standard solution prior to analysis. Sensitivity was about 2 x 10 cps for 1 ng g" solution. Concentrations of plutonium isotopes and " Am were calculated as a function of Pu/ Pu, Pu/ Pu, Pu/ Pu and Am/ Am ratios according to the isotope dilution method. All raw data were corrected for instrumental mass bias using linear correction. NdFs micro coprecipitated alpha sources were counted by a PIPS type alpha Si detector with a surface... 

A modem version of the charged particle detector is called PIPS, an acronym for Passivated Implanted Planar Silicon. This detector employs implanted rather than surface barrier contacts and is therefore more mgged and reliable than the Silicon Surface Barrier (SSB) detector it replaces. 

The authors have demonstrated that it is possible, by the coincidence technique, to reduce the contribution of noise and background from a PIPS detector by a factor of ten and to improve its energy resolution. Such a detector system could be a useful tool for quality control of low-level, low-energy, pure beta emitters such as Ni from environmental samples. 

Later, using a similar approach, Gaggeler and co-workers [24-28] at PSI, Villi-gen built the first dedicated setup for isothermal chromatography experiments with short-lived, a- or s.f.-active isotopes of transactinoids. The essential parts of the equipment are shown in Fig. 1.7. A major concern was high efficiency at every step of processing. Several modifications of this OLGA setup have been built and employed. They differed in the parameters of the column and in the complexity, as well as quality, of the detection system. For example, the older detectors were replaced by the passivated implanted planar silicon (PIPS) detectors, which are much more resistant to elevated temperature and to chemicals. 

In some cases, the filter is used as both particulate trapping medium and as a substrate for holding a derivatizing reagent that reacts with and stabilizes the particulate matter. For example, l-(2-pyridyl)pip-erazine-coated glass fiber filters are used to trap and react with particulate methylene bisphenyl isocyanate to form a derivative that is then analyzed using HPLC coupled with a fluorescence detector. 

To measure the decay of the separated species, they are - after leaving the chromatographic column and entering a water-cooled recluster chamber - attached to new aerosols and transported through a capillary to a detection system, a rotating wheel or a moving tape system (Tiirler 1996) that positions the deposited activity in front of successive PIPS detectors (Passivated Ion-implanted Planar Silicon), which register a particles and SF events. The... 

PIPS detectors have been designed to replace SSB (silicon surface barrier) and DJ (diffused junction) detectors in alpha and beta/(conversion-)electron spectroscopies. Passivation normally means a Si02 layer on the surface, a key to low noise and relative ruggedness. Due to ion-implanted junctions, PIPS s have a very thin (<50 nm) and well-defined dead... 

Alpha spectrum of a Pu/ °Pu mixture obtained with a PIPS detector of 9 keV resolution... 

Fig. 24 Photograph of one side of the detector array used in the COMPACT system. Always four PIPS detectors are arranged on one detector chip, with a spacing of 100 pm. The detectors shown here have been covered with a thin layer of Au of few nm thickness. Two such detector panels are mounted facing each other to form a chromatographic channel...

The concept of CTS, COLD, and COMPACT proved very successful in studying even heavier elements such as Cn and H in their elemental state [41-43]. In order to study the interaction of single Cn and H atoms with Au, the PIPS detector surfaces were covered with a thin, few nanometer thick layer of Au. In the photograph in Fig. 24, the array of Au covered detectors is displayed. Always four detectors are arranged on a detector chip. The spacing between the individual detectors on one chip is only 100 pm. This array of detectors is covered with an identical second one forming thus the chromatographic channel. The two arrays are sealed with an In wire, which is an ideal sealant at the very low temperatures at which one end of the detector array is operated. 

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