Hardware
The Universal Computer Spectrometer offers a unique solution for nuclear spectrometry using the Macintosh platform. A 1K ADC combined with 4K of data memory and multichannel scaling is ideally suited to scintillation spectroscopy and time related studies such as half-life decay.
Constructed in a sturdy, fully-shielded benchtop enclosure with SCSI computer interface, the multichannel analyzer contains many advanced features including computer controlled amplifier and high voltage for PM tubes, upper and lower level discriminators, on-card data memory, and comprehensive software packages for use under Macintosh System 7 or higher.
The UCS-10 requires only an available external SCSI port and is designed to work seamlessly with most types of SCSI-equipped Apple Macintosh™ computers. For stability and low noise operation, the unit is AC-line powered with an autosensing power supply for 100-250 VAC operation. An on-board microprocessor acts as the master controller and data storage device, as well as the communication link directly to the SCSI interface.
The integrated amplifier and high voltage are fully compatible with most standard scintillation detectors, eliminating the need for special tube bases and external modules. For ease of setup and calibration, coarse gain, fine gain, high voltage, and lower and upper level discriminator settings are controlled directly from the desktop computer. For operation with other types of detector systems such as alpha spectrometers or single photon counting, a DIRECT input is provided to bypass the scintillation amplifier and allow direct access to the ADC.
A 1024 channel ADC with derandomizing buffer offers excellent data throughput at high counting rates with minimal dead-time losses. Conversion gain may be changed from 1024 to 512 or 256 channels via the software. Data from the ADC is stored directly in on-board memory for autonomy and high-speed operation, freeing the host computer for other tasks. Three additional 1024 channel memory buffers are included for storing other spectra such as system background.
Software
The UCS-10 produces a high-resolution, real-time live color or monochrome display of spectral data with standard Macintosh graphics running under Mac System 7. Operation is intuitive using pull-down menus and function buttons for the most commonly used commands and display options. The software offers full control of all features including preset live/real time, preset count, and unlimited regions-of-interest together with centroid, gross and net area calculations.
Control of the hardware amplifier, high voltage, ADC and input discriminators is also through function buttons for straightforward calibration and operation. To simplify identification of peaks, the cursor may be calibrated to read directly in energy units, using either a 2-point, or quadratic relationship to allow for detector non-linearity.
In addition to the on-board acquisition data memory, the UCS-10 provides 3 additional hardware memory buffers for holding spectra. A background spectrum may be collected over a long counting period and stored in the Background Buffer. The computed fraction is then subtracted from the data spectrum to remove the environmental background component from each measurement. The remaining buffers may be used for temporary data storage such as when performing spectral comparisons. Spectral files may be transferred to disk for long-term storage as binary files or transferred through the clipboard in ASCII format for exporting to other programs.
To aid in the identification of nuclides, the UCS-10 contains a unique peak labeling feature named ISOMATCH. Providing the unit is accurately energy calibrated, the user may select a nuclide from the library and the corresponding characteristic emission lines are superimposed on the spectrum along with isotope and energy information. Using this feature, users may quickly check a spectrum and visually identify the emission components for each nuclide present. The ISOMATCH libraries may be created or customized using a text editor.
When operating in multichannel scaling mode, the system may be calibrated in time units for direct readout from the cursor. Both linear and logarithmic vertical display ranges are included which can be useful when performing decay studies.
Hardware.
Physical: Fully shielded benchtop metal enclosure, 9x13x2.5 in. Preamp In: BNC connector for direct connection to PMT anode signal. Utilizes on-board amplifier/preamplifier. Direct In: BNC connector bypasses internal amplifier and connects directly to ADC input. Accepts unipolar or bipolar signals 0-8volt range. Ext MCS In: BNC connector bypasses internal amplifier. Accepts positive TTL signals >150nsec., 5MHz maximum rate. HV Output: MHV (or optional SHV) connector supplies positive 0-1280volt @ 1mA maximum current to power scintillation detector. High voltage is fully regulated and computer controlled in 5volt increments. SCSI: 50 pin SCSI-1 input and output connectors for interfacing to Macintosh. Amplifier: On-board combination preamp./amplifier for use with scintillation detectors and PMT's. Computer controlled coarse and fine gain from x2 to x1000. ADC: Wilkinson type with 80MHz clock and computer selected conversion gain of 1024, 512, or 256 channels. Direct input accepts pulse peaking times of 1sec. to 10sec. Includes deadtime correction when used in Live-Time mode. LLD & ULD: Independently computer controlled in 4-channel increments over entire input range. Operates prior to ADC for reduced system dead time. Modes: MCA for pulse height analysis, or MCS for half-life decay or other time related studies. Timers: Real-Time or Live-Time operation selectable from 1msec. to 60sec. per channel in MCS mode. Data Memory: On-board dynamic RAM, 4 x 1024 channel x 3 Bytes for data, plus region-of-interest flag. Deadtime: System dead-time is computed and displayed on screen during acquisition. Power: AC line, 100-250VAC, 50/60Hz, autosensing internal power supply with Universal Power Cord input. Status Indicators: High voltage, Communication, Acquire, Activity.
Software.
System: Operates under Macintosh System 7 or higher. Display: Color or monochrome monitor, Vertical scale adjust from 32 to 16M and LOG display. Horizontal 1024 channels with expansion down to 128 channels. Time Mode: Preset live-time or preset real-time selection. Both times are recorded and displayed. Count Mode: Preset count mode for selected channel or gross region-of-Interest. ROI'S: Multiple Regions-of Interest using color coding. Integral: When cursor is in ROI, computes gross area, net area with end point averaging, centroid and FWHM. Energy Cal: 2-point linear or 3-point quadratic converts cursor position reading directly to energy units. (Time units in MCS mode.) Bkgd Buffer: Used to store background spectrum for time normalized background subtraction. Subtract: Subtracts channel-by-channel time normalized data stored in Background Buffer from display data. Data Buffers: 2 additional software buffers for storing spectra. Used with COMPARE feature. Compare: Overlays data memory spectrum with up to 3 additional spectra stored in Buffers. Smooth: 3-point, or 5-point smoothing of displayed data. Does not modify data in acquisition memory. Control: Software control of High Voltage, Amplifier Gain, Lower and Upper level discriminators, and ADC Conversion Gain. File: Save or load data file and header information in binary format. Clipboard: Clips data and header information, graphic screens, ROI data containing, centroid, FWHM, gross and net integrals, and header information in spreadsheet compatible format for transferring into other applications. ISOMATCH: Isotope library text file with peak markers and labeling for overlaying on spectrum. Provides quick isotope identification. Libraries may be edited and extended using word processor or text editor programs.
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