Detectors channel plate

The field-free drift region in our instrument has a length of 80 cm, while the ion reflector is 12 cm long. This results in a total time-of-flight of about 130 xs for ions of 700 eV and m/z 500. As an ion detector, channel plates in tandem configuration are used. The flight tube is pumped by a 350 Ls l turbomolecular pump. 

Modern XPS spectrometers employ a lens system on the input to the CHA, which has the effect of transferring an image of the analyzed area on the sample surface to the entrance slit of the analyzer. The detector system on the output of the CHA consists of several single channeltrons or a channel plate. Such a spectrometer is illustrated schematically in Fig. 2.6. 

For measurement of local ion intensities in the direct imaging mode (see Fig. 3.19), amplification ensuring laterally uniform-single ion detection is necessary. Depending on the sensitivity of the detector a single or double channel plate is used. Two imaging devices are in use ... 

Resistive Anode Encoder (RAE). This detector has the advantage that the single-ion events are detected digitally. It therefore it delivers quantitative results, irrespective of local differences in the amplification of the channel plate. One disadvantage is that the count rate is limited to 200000. 

For detection of secondary ions a laterally resolving detector is necessary. In the first step a channel plate for amplification is used secondary electrons from the output of this device are accelerated either to a fluorescent screen or to a resistive anode. If a fluorescent screen is used the image is picked up by a CCD camera and summed frame by frame by use of a computer. The principal advantage of this system is unlimited secondary ion intensities, but compared with the digital detection of the resistive anode encoder the lateral and intensity linearity is not as well-defined. 

The TOF energy telescope consists of two channel-plate timing detectors followed by a silicon energy detector. A simple short TOF spectrometer is also... 

This diffusion chamber was modified to provide a uniform flow from two channels at the entrance, one for the filtered room air and the other for the gas from the radon chamber. This modified mobility analyzer is schematically shown in Figure 2. The pressure heads are adjusted so that the gas velocities, v, are the same in both channels. An adjustable vertical electric field, E, is provided through the analyzer so that charged particles are drawn toward the detector located at x cm from the entrance. With the known distance, d, between the radon-laden gas channel and the detector implanted plate, the mobility can then be determined from... 

Fig. 11.13. Diagram of a TOF mass analyzer (with reflectron). Ions enter from an external source and are accelerated (orthogonally) by the pusher electrode toward the reflectron. The reflectron (ion mirror) retards, reverses and reaccelerates the ions back toward the micro-channel plate detector.

Fig. 1.35 Multi-channel plate multiplier. Each hole corresponds to a single channel detector.

The Chevron channel plate ion detector assembly of an imaging atom-probe can also be replaced by a position sensitive particle detector combined with a data processor, as reported by Cerezo etal.5s (A position sensitive detector was used earlier for the purpose of field ion image recording and processing.59) With such a detector both the chemical identity and the spatial origin on the emitter surface can be found for each field evaporated ion. This position sensitive atom-probe can be used to study the spatial distribution of different ion species on the emitter surface as well as inside the bulk of the emitter with a spatial resolution nearly comparable to the FIM. For such a purpose, one carries out the field evaporation at an extremely slow rate so that no more than one ion is detected from the entire field ion emitter surface in each pulsed field evaporation. From the flight time of the ion its chemical species is identified, and from the location of the detector where the ion is detected the spatial origin of the ion is located. With a fast data processor, a two-dimensional distribution of chemical species on the tip surface can be... 

Another approach to differentiating between the anode and cathode water contents is to perform through-plane visualization. Until recently, neutron radiography was not able to achieve the resolutions necessary to sufficiently resolve a membrane thickness of 25 pm and GDL thicknesses of 200 pm. However, Hussey et al.38 developed a new detector technology based on micro-channel plates that allowed in-plane visualization with a resolution of 30 pm (10 pm is feasible with further detector development). An exposure time of 20 min was used and the possibility of increasing temporal... 

FIGURE 10. Schematic drawing of a ZEKE experimental setup QD, quadrant diode PD, photodiode CP, channel plate detector INT, integrator SMS, stepping motor drive FL, dye laser ADC, analog to digital converter PI/O, output/ input port SHG, frequency doubler X, point of interaction. Reproduced by permission of the American Institute of Physics from Reference 27... 

TCSPC is Ulnstrated in Fig. 3a. In addition to a mode-locked laser for pnlsed excitation and a detector with high time resolntion (nsnally a micro-channel plate photomultiplier tube capable of time-resolution of 20-30 ps), the required instrumentation inclndes constant-fraction discriminators to generate electrical pnlses triggered by fluorescence photons and by the reference (the excitation pulse), a time-to-amphtude converter or other device to measnre the time lag between reference and flnorescence connts, and a multichannel scaler to accumnlate... 

The ions are electrostatically deflected after passing the interaction/detection region, and detected by a microchannel plate. The time difference between the photon and the ion depends on the position of the ion when emitting the photon. An improvement by imaging the fluorescence on a position sensitive detector, yielding a determination of decay position to less than 1 mm and thus a time resolution of 20ns, made it possible to do measurements on ion beams of less than lOOs T However, this method is limited by the maximal count-rate allowed on the channel plates. An alternative is to have a selective deflection, so that only when a photon has been detected the deflection is turned on and the ion detected. 

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