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Detailed introduction
Main features
Hardware
- The time width of each channel is selectable from 100 ns to 1,300 seconds
- Number of channels per scan selectable between 4 and 65,536
- Fast analog input accepts count rates up to 150 MHz
- 1 MHz single-channel analyzer input with computer-controlled high and low level discriminators, independently adjustable from 0 to +10 V
- Computer-adjustable discriminator thresholds for fast analog input and external channel advance input
- Zero dead time between lanes: no counts are lost and no counts are repeated at lane boundaries
- No "pass through" dead time
- Sum mode for signal averaging; replace mode for single scan data; replace first then sum mode to avoid reset dead time between acquisitions
- Up to 1,073,741,823 counts per channel in single or multiple channels
- Automatically terminate data collection after a preset number of passes (up to 4 billion)
- A scan start can trigger an experiment, or an experiment can trigger a scan start.
- Includes ramp output with computer-adjustable sawtooth and triangle waveforms
Software
- Equipped with operating, display and analysis software
- All functions can be controlled by computer
- SCA scan mode for recording pulse height spectra and selecting accurate SCA windows
- Spectra and instrument settings can be saved to disk and recalled later for further processing
- Software features include smoothing, summing, stripping, comparing and normalizing spectra; peak searches, reporting and user-defined workflows
- Calibrate results to user-defined units via least squares fit
- A11 Programmer's Toolkit for ActiveX™ programming under LabVIEW®, Visual Basic or Visual C++
Rich time range selection
EASY-MCS uses a crystal-controlled clock with 100 ppm accuracy and high-speed digital electronics to achieve a wide range of precise operating parameters. Since the time width of each channel can be selected from 100 ns to 1300 seconds and the scan length can be varied from 4 to 65,536 channels, the time scan can be selected from 400 ns to 2.7 years.
No dead time between lanes, and zero "pass through" dead time
EASY-MCS uses sophisticated digital circuitry to eliminate inter-channel dead time typically encountered in low-performance multichannel scalers. There are no lost counts and no double counting as the multichannel scaler advances from one time channel to the next. Fast digital processing also ensures there is no dead time passing through before starting a new scan.
Multi-function counting input terminal
Two different types of counting inputs make the EASY-MCS suitable for almost any signal source. The fast analog signal input (IN) accommodates analog and digital signals with pulse widths >3.5 ns and count rates up to 150 MHz. The input discriminator threshold is computer adjustable from -1.6 V to +3 V in 1.5 mV steps (pulse amplitude must be >30 mV). This facilitates prioritizing larger pulses for counting and noise suppression. Positive slope or negative slope triggering can be selected to match pulses of either polarity.
For positive analog signals with count rates up to 1 MHz, EASY-MCS provides pulse amplitude selection on the SCA input. This "single-channel analyzer" has two computer-controlled discriminators at the input, with thresholds programmable between 0 and +10 V and a resolution of 12 bits. EASY-MCS only counts analog pulses that are above the low threshold but not above the high threshold. This input is ideal for analog signals whose amplitude is proportional to a measured parameter, such as the number of photons in the pulse. Pulse widths from 0.5 to 100 μs can be easily accommodated.
Features* SCA scan mode
SCA scan mode sets SCA thresholds quickly, easily, and accurately. In this mode, the width of the window between the lower and upper SCA thresholds remains constant (1/512 of 10 V), while the computer repeatedly scans the position of the window from 0 to +10 V in 512 equal steps. When synchronized, the multichannel scaler repeatedly scans channels 0 through 511 while counting the SCA outputs. The result will show the pulse amplitude spectrum at the SCA input. The mouse can be used to mark the lower and upper limits of spectral features on the screen for selective counting in subsequent multichannel scaler mode. After marking these limits, clicking the Set SCA button on the display locks SCA's lower and upper thresholds into the precise settings that support that feature.
Improve accuracy through signal averaging
For any selected dwell time and storage length, the data collected in each scan can replace, or be added to, the data stored in memory. The latter mode can be used to reduce statistical scatter. It effectively improves the signal-to-noise ratio through signal averaging. For random noise (noise not correlated with the start trigger or dwell time clock), the signal-to-noise ratio improves proportionally to the square root of the number of scans added together. Select Preset Pass Count to set up the instrument to collect data for the desired number of scans (or passes) and then automatically stop data collection. After data collection begins, the computer is free to run other software programs. To allow repeated addition of data with high accuracy, the preset number of passes can be set to any value between 1 and 4,294,967,295, with a memory capacity of 1,073,741,823 counts per channel.
Multifunctional scan synchronization
EASY-MCS provides two methods for synchronizing scans at the start of an event for a desired count. The start of a scan in EASY-MCS can trigger an event (internal trigger mode), or an external trigger of an event can start a scan (external trigger mode).
internal trigger mode
The start output is a 160 ns wide positive TTL signal generated synchronously with the start of the scan. This output can be used to trigger external events. For example, this signal can trigger a laser, whose output light pulses can be used to excite phosphorescence in the sample. After each laser pulse, the decay count rate of photons emitted by the sample is counted by EASY-MCS.
For measurements that require analog control parameters (e.g., Mössbauer experiments), EASY-MCS provides a ramp output voltage proportional to the number of channels in the scan. The ramp can be operated with a zigzag pattern or a triangular waveform. In sawtooth mode, the ramp voltage changes linearly from the start voltage to the end voltage as the scan progresses. At the end of the sweep, the voltage quickly changes back to the starting voltage. For the triangular pattern, the ramp voltage changes linearly from the starting voltage to the midpoint voltage during the first half of the scan. During the second half of the sweep, it makes another linear transition from the midpoint voltage to the end voltage. All three voltages (start, middle and end) are computer adjustable from 0 to +10 V (65,536 steps). To achieve precise repeatability, the ramp curves are stored as digital images in half of the memory. This limits the storage length available for counting events to 32,768 channels when ramping is active.
External trigger mode
In external trigger mode, a positive TTL logic pulse sent to the start input will start a scan in EASY-MCS. Scanning can be based on the internal dwell time clock in EASY-MCS, or channel advancement can be achieved by providing pulses to the channel inputs.
When using the internal dwell time, scanning begins on the edge of the internal 50 MHz clock after the rising edge of the start input pulse. When using external channel advance, scanning begins after the rising edge of the enable input and when the rising edge of the channel advance input pulse exceeds its discriminator threshold. The external channel advance input includes a computer-controlled discriminator threshold selectable from -1.6 V to +3 V in 1.5 mV steps (pulse amplitude must be >30 mV). This discriminator can accommodate a variety of signal sources at the forward input of the external channel. The minimum interval between external channel advance pulses is 100 ns.
Instrument control with a single mouse click
EASY-MCS software running under Windows provides a comprehensive graphical user interface for spectral data display and instrument control. All controls can be activated instantly on the computer display via the mouse. The control is always displayed next to the spectrum. Less commonly used setup parameters are easily accessible from drop-down menus. In addition to quick operations using the mouse, most controls can also be activated via keystrokes. To protect against power outages, all control settings are automatically stored on the hard drive when the scan begins. In addition, settings can be saved in a file so that specific operating conditions can be recalled later.
Quick access to multiple spectra
On-screen controls allow the operator to view spectra acquired in the EASY-MCS dual-port memory, or previously transferred to the computer's buffer memory. All functions related to display and operation can be applied to any of these stored spectra. Spectra can also be saved as disk files for later recall and inspection, or further processing.
Full and extended display of quantitative details
Two views of the selected spectrum are displayed. The box in the upper right corner always shows the complete spectrum. Areas selected and marked on this small screen will expand in the larger screen, allowing for better resolution of details. By using the mouse pointer, markers can be moved across the spectrum to features of interest. At the same time, the computer displays the horizontal coordinates of the channel specified by the marker location, as well as the number of counts recorded in that channel. By default, horizontal coordinates are displayed as channel numbers in external dwell time mode. In internal dwell time mode, the default horizontal coordinate corresponds to the selected dwell time. Horizontal scales can be easily calibrated to user-defined units by least squares fitting to linear, quadratic, or cubic functions. In this case, the mark position will be read in calibrated units. Once calibration is complete, operators can quickly switch between default and calibrated units.
This marker is also used to draw "regions of interest" (ROIs) on the spectrum. Typically, this is a colored area that marks the entire area under the peak of the spectrum. Single or multiple ROIs can be marked in the spectrum. By using the Data Info command under the Calculate menu, markers can be positioned within the ROI to trigger the computer to display the center tract of the ROI, the total counts in the ROI, and the net counts in the peak above background.
More analysis options
Further software features allow the operator to compare two spectra, subtract or add two spectra, normalize the vertical scale, subtract a flat background or smooth statistics. Additionally, a routine is provided that automatically finds each peak in the spectrum and labels it with an ROI. Center lanes, total counts, and net counts can be printed for all ROIs in the spectrum with or without library matching. If the computer is asked to match a user-defined library of peak locations, the library information will be printed along with the matching ROI data. In addition to the standard .MCS file format, spectra can be imported and exported as ASCII text.
Programmed data collection
Some measurements require changes in data acquisition conditions due to the acquisition of different spectra. The Start Job command under the Services menu provides operators with an easy way to define a flow of job commands that change instrument settings and control multiple spectral acquisitions. Job flows can be simple or complex. Once a job flow is defined and implemented, data collection occurs automatically under job control.
Other software programs can activate EASY-MCS to perform specific operations by calling the EASY-MCS software using the job file name specified on the command line. Alternatively, the A11 CONNECTIONS Program Development Kit can be purchased for programming EASY-MCS at the command level. Programming with LabVIEW®, Visual Basic, or Visual C++ becomes even easier with ActiveX™ controls in A11.
