Key elements of the solution

4GHz Time-to-Digital Converter (TDC)

The Kore 4GHz time-to-digital converter (TDC) is new for 2010 and is a compact, bench-top timing unit designed to record a fast stream of event times relative to a single start event (at time=0). It performs this task with a timing resolution of 0.25 ns with minimal dead time, high data rates and the ability to repeat the experiment at very high repetition rates. These features make the unit ideal for use in Time-of-Flight (TOF) mass spectrometry applications. In such an application, the unit issues or receives a cycle start signal at pre-set intervals and waits to receive timing pulses from an ion detector. The pulse times are recorded, buffered and streamed to the PC via a standard USB 2.0 serial interface. Here the standard driver software may process them to spectra 'live', or stream them to the hard disk for more flexible processing options.

GRAMS/AI

GRAMS/AI is a Windows based software package for spectroscopic and chromatographic processing, plotting and viewing offered by Thermo Galactic Corp. It has extensive facilities and is capable of exchanging and organising information used with other packages, e.g. reports, databases, graphics etc. In addition there are add-on applications that provide specialist processing, such as chemometrics and there is a powerful macro language, Array Basic, to ease repetitive tasks. Because it is used by a wide customer base in many fields, Grams enjoys the support of an extensive software team who continually improve facilities and ensure that it can take advantage of all the latest operating system features. Kore is an approved value-added reseller for GRAMS/AI and has made use of its flexible customization features to provide a friendly graphical user interface for TOF SIMS data collection.

Chemical map acquisition application

Kore have written a Windows XP application to collect chemical maps using the Kore TDC described above, for those instruments that have scannable primary beams. An analogue output card provides the scan control while the application records all the ion arrival times. Up to 16 chemical maps may be monitored during the acquisition to confirm correct operation of the instrument. The data is stored in "list-mode", which allows post processing to use any desired mass range for constructing images, without having to repeat the experiment. Images created during acquisition or post-processing may be saved in portable grey map (*.pgm) format. This is a standard ASCII format which may be easily read for DIY processing. Alternatively various free packages (for example ImageJ) can be used to convert to other image formats, or perform a wide variety of image processing operations.

The application is fully multitasking and therefore happily coexists with other software in a normal Windows environment. The acquisition may be run as a standalone application, but more often is launched from a purpose built interface under GRAMS/AI (above) that simplifies the selection of mass windows of interest.

SEM monitor/grab application

Most imaging systems are fitted with a secondary electron detector (SEM). Typically this has a pre-amplifier and then, on old systems, the signal is fed to a slow phosphor monitor. The resulting image is often rather dim and only transiently persistant, difficult to view in a well lit modern laboratory. In addition, the special monitor required is becoming a very expensive item to purchase should replacment ever be necessary.

Kore has written a very simple windows application to make use of the analogue input present on the PCI based scanning card. By connecting this to the SEM detector pre-amp, a continuously refreshed SEM image may be written to the computer screen. The image persistance is of course indefinite and the viewing contrast much higher. The scanning rate is fixed at about 1 frame per second, slow enough to get good signal-to-noise in the image and yet fast enough to give good visual feedback whilst setting up the ion gun.

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Last updated: 03 February 2010, 10:18