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Features:

• Credit-card sized unit replaces shaping amplifier, pileup inspector and multi-channel analyzer.
• Very high throughput:
  >164,000 cps output count rate at 515mW (>1,000,000 cps for a periodic signal)
  >328,000 cps output count rate at 560mW (>2,000,000 cps for a periodic signal)
• User settable gain and pileup inspection criteriapeaking times from 375ns - 96 microseconds.
• High level integration of control and acquisition parameters into reconfigurable sets that are stored in non-volatile memory. Stored sets are accessible with a single command to easily switch between corresponding data acquisition modes.
• Accurate ICR and live-time reporting for precise dead-time corrections.
• Real multi-channel analysis, allowing for optimal use of data to separate fluorescence signal from backgrounds
• Serial communications via RS-232 (and USB with the Development Kit).
• Alternate IDMA parallel interface supports a wide range of communications including Universal Serial Bus (USB).
• Real-time control via 4 general purpose digital I/O lines, two of which can be configured for industry standard I2C interface.

Specifications

• Input (Analog)
  Preamp Input: 1k Ohms input, voltage range +5.0 V to -5.0 V standard. Works with common reset or resistor feedback preamps of either polarity.
  
• Interface
  Standard: RS-232 Serial communications
  OEM Option 1: Analog Devices high-speed serial port (SPORT) via the flat-flex interconnect
  OEM Option 2: 16-bit IDMA bus; 4 general purpose digital I/O lines, two of which can be configured for industry standard I2C interface; connected via a high-density board-to-board connector. The microComU USB interface employs this connection.
  
• Digital Controls
  Gain Option a): Fixed gain for embedded applications
  Gain Option b): 50X range controlled by 16 bit DAC. For general use with preamplifiers with gains nominally in the 0.1 to 5.0 mV/keV range. Adds 125mW to the power budget.
  Shaping: Triangular/Trapezoidal.
  Peaking times: 375ns - 96 microseconds. Adjustable dwell time may be used to eliminate ballistic deficit effects.
  Pileup: Set fast channel filter time, pulse detection threshold, and fast channel pileup inspection test limits to achieve best results in each situation.
  Spectrum: 1K-8K bins, High/Low limits, bin widths.
  
• Data Outputs
  Spectrum Size: 1024-8192 channels standard, more with optional extra memory.
  Other: collection livetime; total counts; pileup rejected counts; baseline statistics.
  
• Power Requirements
  +/-5 V @ 25mA
  +3.3V @ 85mA - 150mA
  
• Dimensions
  2.125" W x 3.375" L

Examples of Systems that Incorporate the microDXP

The microDXP miniaturized circuit-board can easily be incorporated into a variety of benchtop, portable, networked and embedded x-ray and gamma-ray spectroscopy data acquisition systems. In the first example the microDXP runs either on the laboratory benchtop as a peripheral device under the control of an x86 Personal Computer, or similarly in portable systems under the control of a PDA. No hardware or firmware modifications are required.

In the second example a more complex dedicated system is considered. The I2C serial bus is used to control a ‘smart’ x-ray tube and detector HV bias supply, and the auxiliary digital I/O drives electromechanical or pneumatic components in real time based upon user defined metrics of acquired data.

Example 1. General-Purpose Spectrometer

In this example the microDXP and hardware included in the Development Kit act as a general-purpose spectrometer, connected as a peripheral device under the control of a host computer or PDA. No specialized data acquisition modes are required, thus no firmware development is necessary.

XIA non-recurring engineering (NRE) required: None

User development required: Enclosure design

The microDXP, power supplies and microComU together constitute a spectrometer that can be connected to virtually any controller with USB or RS-232 communications. Note: The microComU interface board included with the development kit falls into this category.

Fig. 1: A general-purpose spectrometer incorporating the microDXP. The microComU interface connects the microDXP to the host computer/PDA and power supplies.

Example 2. Dedicated Embedded Spectrometer

This example considers a materials sorting application where objects with certain pre-defined alloy ratios X, Y and Z are to be separated from others. An x-ray source irradiates incoming samples, and incident x-rays are collected by a solid-state detector connected to the microDXP. The microDXP is configured to assert a combination of its auxiliary digital I/O lines whenever the peak ratio X,Y, or Z is detected. The digital I/O lines drive electromechanical or pneumatic components in real-time to execute the appropriate mechanical operation, e.g. put the recognized object in the desired bin. User controls are limited to starting and stopping the system, and selecting one out of a small number of operating modes. Power supplies for the microDXP are also included. Finally, an external data port (e.g. RS-232) is also included so that ratios corresponding to new alloys can be defined, and new firmware uploaded without dismantling the hardware; or, alternatively, the microDXP could periodically be run in full MCA mode under computer control for diagnostic purposes.
This example demonstrates a system that uses a very small data acquisition command set (i.e. ‘start run’ and ‘stop run’) but that, conversely, requires customizations to the microDXP as well as significantly more user-designed hardware.

XIA non-recurring engineering (NRE) required:

1. Customized PIC microcontroller code is required to implement the I2C peripheral device control.
2. Customized PIC microcontroller code is required to implement high-level data acquisition routines controlledthrough the user pushbutton interface.
3. Customized DSP code is required for peak ratio calculations, possibly implemented in lookup tables.
4. Minimal FiPPI (FPGA) code modification is required to implement the auxiliary digital I/O functionality.

User development required:

1. A more advanced interface unit is required to break out the microDXP high-density internal connection to standard RS-232, auxiliary and power connections. Still, this interface does not involve many active components, i.e. the I2C and auxiliary digital I/O are simply routed to additional connectors. The pushbutton interface might include an additional microcontroller, but could be implemented simply in logic.
2. As drawn, the power supply is integrated on the interface board, with the same requirements as in the previous example. As stated there, optional voltage regulators for the analog circuitry are included on the microDXP for systems in which high-quality power supplies are not available.
3. Again, some additional mechanical design, i.e. enclosure design, may be necessary.

Fig. 2: A system with a fully embedded host and user interface, with real time controls via the Auxiliary digital I/O.

Designing the system described above using conventional spectroscopy components would be a much more complex (and considerably more expensive) task, when compared with the solutions proposed here. Please contact the microDXP team at to discuss your application today!

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http://www.xia.com/microDXP.html, last updated August 9, 2012
© XIA LLC 2013