Our DP5 is a high performance digital pulse processor (DPP) optimized for OEMs and lab users. It digitizes the preamplifier output signals, replacing both the shaping amplifier and MCA in a traditional, analog spectroscopy system. The DP5 offers several clear advantages over traditional systems, including improved performance (very high resolution, reduced ballistic deficit, higher throughput, and enhanced stability), enhanced flexibility, low power consumption, small size, and low cost.
The DP5 implements the pulse processing using dedicated circuitry. It includes an 8051 compatible microcontroller for controlling the unit. Communication interfaces include RS-232, USB, and Ethernet. Several general purpose I/O lines are also available. The DP5 is suitable for OEMs and for laboratory users who need custom capabilities and are familiar with electronics.
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Figure 2. Trace 1 above shows the input to the DP5, which is the output from a reset-type charge sensitive preamplifier. This is processed by the analog prefilter producing the prefilter output shown in Trace 2. This is digitized and then processed digitally, producing the DP5’s shaped output shown in Trace 3. Finally, the DP5 creates a multichannel anlayzer (MCA) type output spectrum shown in Graph 4.
|Gain||Combination of coarse and fine gains yields overall gain continuously adjustable from x0.84 to x127.5.|
|Coarse Gain||16 log spaced coarse gain settings from x1.12 to x102.00
|Fine Gain||Fine gain is adjustable between 0.75 and 1.25, 13 bit resolution|
|Full Scale||1000 mV input pulse @ x1 gain|
|Gain Stability||<20 ppm/° C (typical)|
|ADC Clock Rate||20 or 80 MHz, 12 bit ADC (software selectable)|
|Pulse Shape||Trapezoidal. A semi-gaussian amplifier with shaping time t has a peaking time of 2.2t and is comparable in performance with the trapezoidal shape of the same peaking time.|
|Peaking Times||30 software selectable peaking times between 0.1 and 102 µs, corresponding to semi-Gaussian shaping times of 0.05 to 45 µs.|
|Flat Top Times||16 software selectable values for each peaking time (depends on the peaking time), >0.05 µs.|
|Max Count Rate||With a peaking time of 0.2 µs, a 4 MHz periodic signal can be acquired.|
|Dead Time per pulse||Dead time is 1.05 x peaking time. No conversion time.|
|Fast Channel Peaking Times||20 MHz: 200, 400, 800, 1600, 3200 ns
80 MHz: 50, 100, 200, 400, 800 ns
|Fast Channel Pulse Pair Resolving Time||Equal to the fast channel peaking time plus the signal risetime.|
|Pile-Up Reject||Pulses separated by more than the fast channel resolving time, 120 ns, and less than 1.05 x peaking time are rejected.|
|Baseline Restoration||Assymetric, 16 software selectable slew rate settings.|
|Number of channels||Commandable to 256, 512, 1024, 2048, 4096, and 8192 channels.|
|Bytes per channel||3 bytes (24 bits) – 16.7M counts|
|Preset Acquisition Time||10 ms to 466 days|
|Data Transfer Time||1k channels in 5 milliseconds (USB), 280 milliseconds (RS-232)|
|Presets||Time, total counts, counts in an ROI, counts in a channel|
|MCS Timebase||10 millisec/channel to 300 sec/channel|
|External MCA Controls||Gate input: Pulses accepted only when gated on by external logic. Input can be active high or active low.|
|Counters||Slow channel events accepted by MCA, Incoming counts (fast channel counts above threshold), event rejected by selection logic, and external event counter.|
|Microprocessor||Silicon Labs 8051F340 8051-compatible core|
|External Memory||512kB low-power SRAM|
|Firmware||Signal processing is programmed via firmware, which can be upgraded in the field.|
|RS-232||Standard RS-232 serial interface at up to 115.2 Kbaud.|
|USB||Standard USB 2.0 full speed (12 Mbps).|
The primary purpose of this connector is to bring out logic signals which are not required for the primary use of the DP5: acquiring spectra and transmitting them over the serial interface. These are generally “low level” logic signals associated with each pulse processed by the DP5. They are primarily used for synchronizing the DP5 data acquisition to external hardware and for direct counter/timer outputs from the DP5. The signals are described below. The connector is a 2×8 right angle Samtec part number ASP-135096-01.
|Single Channel Analyzers (total of 16)||Hardware
8 SCAs with logic outputs, independent software selectable LLDs and ULDs, LVCMOS (3.3V) level (TTL compatible) The hardware SCA’s can also be directed to internal counters and read out by software.
8 SCA’s, independent selectable LLDs and ULDs, selectable between 8 settings including INCOMING_COUNT, PILEUP, MCS_TIMEBASE, etc. The software SCA’s are connected to internal counters and read out by software.
|Digital Inputs||Two independent inputs, software selectable for MCA_GATE, EXTERNAL_COUNTER I/O
Two general purpose I/O lines for custom application.
|Digital Outputs||Two independent outputs, software selectable between 8 settings including INCOMING_COUNT, PILEUP, MCS_TIMEBASE, etc.
Two general purpose I/O lines for custom application.
|I/O||Two general purpose I/O lines for custom applications.|
|Digital Oscilloscope||Displays oscilloscope traces on the computer. Software selectable to show shaped output, ADC input, etc., to assist in debugging or optimizing configurations.|
|Pin #||Name||Pin #||Name|
|Analog Input||The analog input accepts positive or negative going pulses from a charge sensitive preamplifier.
NOTE: Can be configured with a charge sensitive preamplifier for use with PMTs. Contact Amptek for details.
1×3 right angle header Molex part number 22-28-8032.
|Power||+ 5 VDC. Hirose MQ172-3PA(55)|
|RS-232||Standard 2.5 mm stereo audio jack.|
|USB||Standard USB mini-b jack.|
|Ethernet||Standard RJ-45 Ethernet jack.|
|Auxiliary||2×8 16-pin 2 mm spacing (Samtec part number ASP-135096-01). Mates with connector Samtec P/N TCMD-08-S-XX.XX-01|
|DAC Output||This output is used in oscilloscope mode, to view the shaped pulse and other diagnostic signals. Range: 0 to 1 V.
1×2 right angle header Molex part number 22-28-8022.
|DPPMCA||The DP5 can be controlled by the Amptek DPPMCA display and acquisition software. This software completely controls and configures the DP5, and downloads and displays the data. It supports regions of interest (ROI), calibrations, peak searching, and so on. The DPPMCA software includes a seamless interface to the XRS-FP quantitative X-ray analysis software package. Runs under Windows XP PRO SP3 or later. Click here for the software download page.|
|SDK||The DP5 comes with a free Software Developer’s Kit (SDK). The user can use this kit to easily write custom code to control the DP5 for custom applications or to interface it to a larger system. Examples are provided in VB, VC++, etc. Click here for the software download page.|
|VB Demonstration Software||The VB demonstration software runs on a personal computer and permits the user to set the DP5 parameters, to start and stop data acquisition, and to save data files. It is provided with source code and can be modified by the user. This software is intended as an example of how to manually control the DP5 through either the USB, RS232, or Ethernet interface using the most basic calls without the SDK. This is primarily needed as an example when writing software for non-Windows platforms. Click here for the software download page.|
|+5 V||80 Mhz clock: 200 mA (1 W) (typical)
20 MHz clock: 180 mA (0.9 W) (typical)
|Input Range||+4 V to +5.5 V (at 0.25 to 0.18 A typical)|
|Initial transient||2 A for <100 ns|
|Power Source||External supply or USB bus|
|Size||3.5 in x 2.5 in; 8.9 cm x 6.4 cm|
|Operating temperature||-40 °C to +85 °C|
|Warranty Period||1 Year|
|Typical Device Lifetime||5 to 10 years, depending on use|
|Storage and shipping||Long term storage: 10+ years in dry environment
Typical Storage and Shipping: -40 °C to +85 °C, 10 to 90% humidity noncondensing
The DP5 is a component in the complete signal processing chain of a nuclear instrumentation system. The input to the DP5 is the preamplifier output. The DP5 digitizes the preamplifier output, applies real-time digital processing to the signal, detects the peak amplitude (digitally), and bins this value in its histogramming memory, generating an energy spectrum. The spectrum is then transmitted over the DP5’s serial interface to the user’s computer. Clearly, the DP5 must be used with other components, including a detector, preamplifier, and computer.
The input to the DP5 is the output of a charge sensitive preamplifier. The analog prefilter circuit prepares this signal for accurate digitization. The main functions of this circuit are (1) applying appropriate gain and offset to utilize the dynamic range of the ADC, and (2) carrying out some filtering and pulse shaping functions to optimize the digitization.
NOTE: The DP5 can be ordered with a charge sensitive preamplifier on the board for use with PMTs.
The ADC digitizes the output of the analog prefilter at a 20 or 80 MHz rate (software selectable). The digitized values are sent, in real time, into the digital pulse shaper. 12 bit ADC is used.
The ADC output is processed continuously using a pipeline architecture to generate a real time shaped pulse. This carries out pulse shaping as in any other shaping amplifier. The shaped pulse is a purely digital entity. Its output can be routed to a DAC, for diagnostic purposes, but this is not necessary.
There are two parallel signal processing paths inside the DPP, the “fast” and “slow” channels, optimized to obtain different data about the incoming pulse train. The “slow” channel, which has a long shaping time constant, is optimized to obtain accurate pulse heights. The peak value for each pulse in the slow channel, a single digital quantity, is the primary output of the pulse shaper. The “fast” channel is optimized to obtain timing information: detecting pulses which overlap in the slow channel, measuring the incoming count rate, measuring pulse risetimes, etc.
The DP5 uses trapezoidal pulse shaping, which offers high energy resolution, reduces ballistic deficit, and provides excellent baseline stability at high count rates.
The pulse selection logic rejects pulses for which an accurate measurement cannot be made. It includes pile-up rejection, risetime discrimination, logic for an external gating signal, etc. At high count rates, the DP5 has both better pile-up rejection and higher throughput than a traditional, analog shaping amp.
The histogram memory operates as in a traditional MCA. When a pulse occurs with a particular peak value, a counter in a corresponding memory location is incremented. The result is a histogram, an array containing, in each cell, the number of events with the corresponding peak value. This is the energy spectrum and is the primary output of the DP5. The unit also includes several counters, counting the total number of selected pulses but also counting input pulses, rejected events, etc. Auxiliary outputs include eight different single channel analyzers, and both a DAC output and a digital output showing pulse shapes from several points in the signal processing chain.
The DP5 includes hardware and software to interface between these various functions and the user’s computer. A primary function of the interface is to transmit the spectrum to the user. The interface also controls data acquisition, by starting and stopping the processing and by clearing the histogram memory. It also controls certain aspects of the analog and digital shaping, for example setting the analog gain or the pulse shaping time.
The interface includes a microcontroller that impliments RS232, USB, and Ethernet communications.
Amptek’s DP5 Digital Pulse Processor is a component in the complete signal processing chain of a nuclear instrumentation system. It must be used with other components, including (at a minimum) a detector and preamplifier, and computer with a serial interface and software to communicate. The DP5 itself has its own power supplied so only needs a +5 V DC input. When using the DP5 with Amptek detectors, additional power supplies are needed for the detector and preamp. Amptek provides the PC5 board that mates with the DP5 and provides power to Amptek detectors.
The PC5 provides power to Amptek XR-100 detectors from a +5 VDC source. This board is intended for those using Amptek detectors and preamps. The USB interface cannot supply enough current to operate the XR-100, so an external DC supply is required, which must be between 4.0 and 5.5 V.
Dimensions: 3.5 in x 2.5 in
Figure 4. DP5 with PC5 and Amptek detector/preamp.
Figure 5. DP5 (top) mated with the PC5 (bottom).
There are two distinct software packages that are needed for the DP5: embedded software that runs on the microcontroller on the DP5 (firmware), and acquisition and control software that runs on the attached computer.
The embedded software is responsible for controlling the pulse processing, controlling the MCA, carrying out some data processing, and interfacing with the personal computer. This software is fixed and cannot be modified by the user. Firmware updates will be released by Amptek and can be uploaded in the field by the user.
The DP5 can be controlled by the Amptek DPPMCA display and acquisition software. This software can be used for control and display of the DP5 and supports regions of interest (ROI), calibrations, peak searching, and so on.
The DP5 comes with a complete Software Development Kit (SDK). The user can use this platform to easily develop software to control the DP5 for custom applications or to interface it to a larger system. Examples are provided in VB, VC++, etc.
Application Note AN-DPP-003: Using the DP5 with Germanium (HPGe) Detectors
The Amptek DP5G is a state-of-the-art, high performance, low power digital pulse processor designed for use in scintillation spectroscopy systems. Connected to the anode of a PMT, it includes a charge sensitive preamplifier and a digital pulse processor, which replaces both the shaping amplifier and the MCA in a traditional nuclear spectroscopy system. The DP5G offers several advantages over traditional systems, including higher performance, enhanced flexibility, small size, and low cost.