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Scanning probe microscopy is at the verge of revolutionizing microscopy once again. Video-rate scanning tunneling microscope (STM) and video-rate atomic force microscope (AFM) technology will enable the direct observation of many dynamic processes that are impossible to observe today, such as atom or molecule diffusion, real time film growth, or catalytic reactions. In this paper we discuss the critical aspects that have to be taken into account when working on increasing the imaging speed of scanning probe microscopes. We highlight the state-of-the-art developments in the control of the piezoelectric scanning elements and describe the latest innovations regarding the design and construction of the whole mechanical loop including new scanner geometries. We identify critical aspects for which no obvious solution exists and aspects where advanced control engineering can help, like piezo non-linearities, the acceleration limit and the challenging technical requirements for the preamplifiers that are needed for measuring a tunneling current. Finally, we provide an overview of a number of new directions that are being pursued to solve the problems currently encountered in scanning probe technology.

A simple, efficient, and robust on-line data-processing scheme was developed for the digital front-end electronics of the electromagnetic calorimeter of the PANDA spectrometer at FAIR, Darmstadt. The implementation of the processing algorithm in FPGA enables the construction of an almost dead-time free data acquisition system. The prototype of a complete trigger-less readout chain has been developed and evaluated. The precision of time synchronisation commands has been verified. A pile-up recovery algorithm was developed and evaluated over a large dynamic range of signal amplitudes. (C) 2012 Elsevier B.V. All rights reserved.

The PANDA collaboration at the future FAIR facility at Darmstadt, Germany, will employ antiproton annihilations to investigate resonances in the charmonium mass region. In order to gain high flexibility for physics event selection, a readout system without hardware trigger, i.e. a trigger-less data-acquisition system will be employed and is currently being developed. The event-selection is based on high-level reconstructed information, e.g. invariant mass, secondary vertices, and time correlations, which may be contributed from all sub-detector systems. Prototypes of the PANDA Electromagnetic Calorimeter have been exploited to verify the desired event-selection approach. The prototype readout system includes a dedicated Sampling ADC (SADC), data concentrator (DCON) and compute-node (CN) modules. An optical link connects several SADC digitizers to a DCON module from where the data are streamed to the CN network. Data, collected by the SADCs are processed online in FPGAs by a feature-extraction algorithm. This processing technique guarantees a dead-time free operation and allows including an on-line pile-up recovery process for single detector counting rates up to 1 MHz. The prototype of the readout-chain has been evaluated using pulse generators and high-energy photon beams; the proper event correlation could be verified. The applied FPGA has been irradiated with protons to demonstrate its applicability in the radiation environment of the PANDA experiment.

The PANDA experiment at the future FAIR facility at Darmstadt, Germany, will employ a novel electronics-readout concept: the trigger-less readout. This concept implies an event selection based on the physics properties of detected particles, such as reconstructed invariant mass or a detected secondary vertex. Such an approach requires a completely new design of the readout chain from the front-end to the data acquisition. This paper describes a fully-functional prototype of the readout chain for one of the PANDA subdetectors - the Electromagnetic Calorimeter. The prototype consists of digitizer and data-multiplexer modules. The crucial component of the prototype is the synchronous optical-link connection, which allows to transfer clock signal and time-synchronisation commands in an unambiguous way. The implementation and performance tests of the synchronous optical-link connection are described in the paper.

An instrument is described for the measurement of circular and linear polarizations of the luminescence with a time resolution up to 50 ns. The spectrometer, which makes use of a 50-kHz photoelastic modulator and a differential photon-counting technique, is accurate and absolute and is capable of detecting small degrees of polarization. Making use of excitation light pulses which lie randomly in the modulator's duty cycle, the instrument can be readily interfaced with a variety of externally triggered or free running pulsed light sources.

An instrument is described for time-resolved (TR) detection of circular polarisation of the luminescence (CPL). The TR-CPL spectrometer combines the optical part of a commercially available gated photon-counting spectrofluorimeter with the differential photon-counting system of a home-built continuous-wave (CW) CPL instrument described previously. The resulting spectrometer is sensitive and accurate, and allows for the determination of circular (and linear) polarisation data in the time domain 10 mu s-100 ms. Similarly, a CW photon-counting spectrofluorimeter can be transformed into a high performance CPL spectrometer.

In this article we introduce a, video-rate, control system that can be used with any type of scanning probe microscope, and that allows frame rates up to 200images∕s. These electronics are capable of measuring in a fast, completely analog mode as well as in the more conventional digital mode. The latter allows measurements at low speeds and options, such as, e.g., atom manipulation, current–voltage spectroscopy, or force–distance curves. For scanning tunneling microscope (STM) application we implemented a hybrid mode between the well-known constant-height and constant-current modes. This hybrid mode not only increases the maximum speed at which the surface can be imaged, but also improves the resolution at lower speeds. Acceptable image quality at high speeds could only be obtained by pushing the performance of each individual part of the electronics to its limit: we developed a preamplifier with a bandwidth of 600kHz, a feedback electronics with a bandwidth of 1MHz, a home-built bus structure for the fas...