Introduction

In the PMT-3000 we combine the successful eMorpho design with the ability to directly operate a PMT-based radiation detector. The PMT-3000 retains all the powerful capabilities of the eMorpho, including direct waveform sampling at 40MHz for on-the-fly pulse shape discrimination.

While the FPGA is acquiring data, the ARM processor controls the PMT, executes gain and performance stabilization. On top of that it has the resources to provide data processing and exposes a USB interface.

The PMT-3000 is ideal for high-precision spectroscopy combined with pulse shape discrimination (PSD). Applications are traditional Phoswich detectors and, of course, the newer multipurpose scintillators NAIL, CLLB, and CLYC. In these materials PSD can be used to separate gamma-rays from neutrons.

Capabilities

PMT-3000 Standard and Optional Capabilities
Capability	Description
Analog	Operate PMT-arrays at up to 37V. Direct anode to amplifier coupling for highest signal fidelity and best pulse shape discrimination.
Gain stabilization	The PMT-3000 can adjust the operating voltage and the digital gain independently as a function of temperature to ensure that both gain and trigger threshold remain constant over temperature. Such a look up table necessarily depends on the scintillator, and developers can program their own tables. A third lookup table can be used in conjunction with LED-based gain stabilization or for custom purposes.
Two-bank counter and histogram	The PMT-3000 can count pulses in either of two active banks, one for samples to be measured and one for storing a background measurement. In dynamic environments, the two banks can be used to implement loss-less counting: One bank acquires data while the other bank can be read at leisure.
Net counts and histograms	Custom PMT-3000 embedded software can report background-subtracted histograms and count rates.
High-speed DSP	In the PMT-3000 the MCA is implemented in an FPGA and its input data stream is the digitized scintillator pulse waveform. As a result, the FPGA can apply pulse shape discrimination in real time. This supports various specialty applications at the highest possible speed and throughput. Examples are phoswiches and neutron/gamma detectors.
Analysis	Custom PMT-3000 embedded software can report the probability that the measured sample count rate is compatible with the background count rate. Users can set an alarm threshold in terms of probability: Alarm if there is little chance (<ε) that the sample count rate is caused by the measured background.
Dynamic alarming	Custom PMT-3000 embedded software and FPGA firmware can analyse and report count rates in time slices of 100ms, ie at a rate of 10/s. The device automatically tracks slowly changing backgrounds and will alarm on a passing source. Its digital output can be used to drive an audio or visual alarm.
Communication	The PMT-3000 implements a USB-2.0 compatible USB 1.2 interface.

Gain stabilization

The PMT-3000 can use a 20-point lookup table that describes the desired operating voltage and digital gain vs temperature behavior. The embedded processor applies this to counteract the PMT vs temperature gain drift. Typically, the lookup table starts at lut_tmin=-30°C and increments in lut_dt=5°C steps up to 65°C. However, the developer can configure that to meet their requirements. And the developer can program a lookup table of their own choice into the non-volatile memory of the PMT-3000.

The developer programming the lookup tables into the PMT-3000 can set the lut_mode lock-bit to 1. That prevents a user from reading back a proprietary gain-stabilization lookup table.

Time-slice operation

There are dynamic situations, where a radioactive source can be measured only for a brief moment. Examples are a vehicle passing through a radiation portal monitor, or a person with a backpack detector walking past a stationary source.

The time-slice operation supports these cases. When equipped with the appropriate software and FPGA firmware, the PMT tracks slow changes in the environmental background. An alarm is created when during a summation time (L) of typically 4 seconds, the accumulated counts are significantly more than what is expected from the background. The alarm threshold is defined as the probability that the measured counts (N) during a period L, could have been caused by the established background rate over the same period (B).A threshold of 1.0e-4 means that we alarm when P(Counts ≥ N|BCK) < 1.0e-4.

For example, assume a summation time of 4 seconds and a background rate of 500cps for BCK=2000. Now assume that we count 2500cps in a particular 4s-period. The probability of the established background to cause 2224 counts or more in 4s is P(Counts ≥ 2224|BCK=2000) = 2.86e-7. This smaller than the alarm threshold of 1.0e-4, and the embedded program will generate an alarm.

If the alarm condition is permanent, the software resets all the logic after a period of H time slices and starts counting again. It now will accept the suddenly higher level of radioactivity as the new normal background.

Brief Specifications

• Hardware is suitable for all scintillators
• Energy histogram (on board) 4096 x 32
• Accurate count rate measurements
• Efficient pile up rejection
• On the fly pulse shape discrimination
• List mode: 340 events buffer
• Trace capture: 1024 ADC samples
• Non-volatile memory 16 kByte
• Power: 4.3V to 5.5V, 60mA
• Minimum time between gamma-rays: 0.125µs
• Open source application programmer's interface; Python API
• Web-based graphics user interface accessible from any browser.
• PMT supply: 1400V/250µA
• USB 1.2 interface compatible with USB 2.0
• On-board ARM software is secure against reverse engineering.

PMT-3000
Positive High Voltage Dividers

List of common positive high voltage dividers; Call for other pinouts.

Part number	Description	Application
P81L	R6231 or compatible 8-stage PMT, linear divider	High gain; For plastic scintillators, BGO, CsI(Na), SrI2
P81T	R6231 or compatible 8-stage PMT, tapered divider	For NaI(Tl), LaBr3
P10L	R878 or compatible 10-stage PMT, linear divider	High gain; For plastic scintillators, BGO, CsI(Na), SrI2
P10T	R878 or compatible 10-stage PMT, tapered divider	For NaI(Tl), LaBr3

PMT-3000
Negative High Voltage Dividers

List of common negative high voltage dividers; For best spectroscopy above 100kcps use a detector that can be operated at negative high voltage. Call for other pinouts.

Part number	Description	Application
N81L	R6231 or compatible 8-stage PMT, linear divider	High gain; For plastic scintillators, BGO, CsI(Na), SrI2
N81T	R6231 or compatible 8-stage PMT, tapered divider	For NaI(Tl), LaBr3
N10L	R878 or compatible 10-stage PMT, linear divider	High gain; For plastic scintillators, BGO, CsI(Na), SrI2
N10T	R878 or compatible 10-stage PMT, tapered divider	For NaI(Tl), LaBr3

PMT-3000
Common Part Numbers

See part builder for all valid part numbers.

Frequently ordered part numbers. Fill out our detector questionnaire and we can help to identify the correct part number. Part numbers for oemBases are similar; just replace the word usbBase with oemBase.

Part number	Description	Application
PMT3K-40-N81L	40MSPS ADC, negative high voltage, R6231 or compatible PMT	Plastic scintillators, BGO
PMT3K-80-P10T	80MSPS ADC, positive high voltage, standard 10-dynode PMT	NaI(Tl)
PMT3K-80-N81T	80MSPS ADC, negative high voltage, R6231 or compatible PMT	NaI(Tl), LaBr3(Ce)
PMT3K-120-N81T	120MSPS ADC, negative high voltage, R6231 or compatible PMT	LaBr3(Ce)

Downloads and Pricing

Prices may change without prior notice.

• Flyer: English, 简体中文
• User's manual
• Connector Pinouts
• PMT pinouts
• MCA Selection Guide
• Self-extracting Windows driver installer: Driver
• Software and documentation for all MCA wxMCA.zip
• On-line software documentation

See part builder for all valid part numbers.

Configure your PMT MCA