NIPM14 PMT REPLACEMENT WITH INTEGRATED 512 CHANNELS MCA, BASED ON SiPM MATRIX WITH INTEGRATED POWER SUPPLY AND REMOTE ETHERNET CONTROL WITH LORA SUPPORT

INTRODUCTION

The NIPM14 is 2 inch PMT replacement system based on a large Hamamatsu 15x15 mm SiPM matrix with integrated HV power supply, temperature, voltage and current monitor. It also integrate a shaper, a peak stretcher and a peak ADC to implement a simple MCA. The system integrate a temperature compensation loop that changes the SiPM power supply in function of the temperature measured on the detector. The NIPM14 module could be controlled by ethernet and provide as output an analog amplified signal with a 1GHZ BW amplifier on an analog output and a 512 channels Energy Spectrum calculated onboard.
NIPM13 can be coupled with LaBr, NaI(Tl), CsI(Tl), BGO, Lyso, and others scintillator.
Nuclear Instruments offers the mechanical tooling and scintillator coupling service.
The device include a LORA radio-modem and it is ready to connect to LORA/LORAWAN networks for IoT applications and enviromental radiation monitoring.

FEATURES

  • 15x15 Hamamatzu SiPM matrix
  • Passive current to voltage conversion and shaping followed by a x5 amplifier with 1GHz BW
  • Integrated 512 channels MCA
  • Up to 100Kcps sustainable input count rate
  • Leading Edge trigger logic
  • Small form factor: 35 x 39 x 5.5 (mm)
  • LEMO-0 analog signal output connection
  • Integrated High Voltage regulator (20...80V)
  • Temperature, Voltage and current monitor with 1 hour memory
  • Temperature compensation on HV power supply
  • Web based configuration and monitor interface with the possibility to access to the spectrum, process and download it directly from the Web Interface
  • REST API interface for automation control
  • LORA radio modem with LORAWAN support
  • 8 to 16v power supply, less then 2W power dissipation

WORKING PRINCIPLE

The NIPM14 module is an electronic system designed to replace existing system based on PMT. The integrated HV power supply provide a low noise accurate power supply for the SiPM detector. The detecor is an Hamamatzu MPPC 4x4 3mm pitch. All pixels of the matrix are connected in parallel in order to increase the active area of the matrix. A passive current to voltage stadium convert the SiPM photocurrent in a voltage signal. The SiPM current is converted to voltage by a 27Ω resistor and then shaped with 180ns single pole pure exponential shaper. The voltage signal in then amplified by a wideband gain of 5 Votage Mode Amplifier and provided to the output on the LEMO connector. It is strong suggested to 50Ω terminate the signal on receiver side due to very fast transition. A charge integrato amplifier collect the charge from the detector and an analog shaper reduce the high frequency noise contribution. A peak sensing ADC converts the energy of the pulse in a digital value. The microcontroller on board generate the spectrum and manage ethernet communication and HV control.
A leading edge trigger is used to detect pulses. The microcontroller implements a pile-up rejection logic.
The NIPM14 module include also a low noise HV power source for the SiPM detector. It is possible to regulate the output voltage with a resolution of 20mV and monitor the real voltage on the detector with a resolution of 1.9mV. More over it is possible to monitor the current with a resolution of 25nA and the temperature on the detector. The temperature could be also used as a feedback for the HV voltage generator. It is possible to insert a SiPM coefficient correction to automatic change the HV voltage in function of the temperature. The coefficient is expressed in mV/°C in respect to 25°C where the correction is considered 0V. The module could be controlled using ethernet connection. If dynamic change of parameters and monitor is not required the configuration could be stored in the internal flash and the module could be used as a stand alone unit without any external interconnection except the analog signal output as a standard PMT.
The device include a LORA radio-modem and it is ready to connect to LORA/LORAWAN networks.

CONNECTION

Multiple NIPM14 devices can be connected and controlled from a single PC.
The API interface allows to control multiple devices using very simple http requests and JSON vectors. Both HV parameters and MCA parameters can be controlled by the API interface.
It is possible to automate the spectrum download by the meaning of the API interface
Almost all programming languages can perform HTTP requests and encode/decode JSON vectors.

WEB BASED INTERFACE

The homepage show the status of the HV generator (voltage, current, enable and protection) and the temperature on the detector. User can power on/off the HV and set the output voltage. On the left menu it is possible to access to the secondaries pages:
  • Monitor: home page with HV and detector status
  • vHistory: download last hour of data (votage, current, and temperature) from the microcontroller and then accumulate data forever until the page is open
  • Spectrum: Allow to access to the spectrum data, perform online analysys (area under peak, fitting, setup alarms) and download the spectrum data
  • Settings: advanced settings for the HV controller like temperature compensation, protection and HV status on power on
  • Configuration: ethernet configuration



The NIPM13 module has an internal circular buffer memory of an hour where it stores voltage, current and temperature of the sensor. The history page download this information that are always sampled even if the history page is not opened. When the user open this page last hour of data is immediatly downloaded and then every second the whole data set is updated. If the page is opened there isn’t a real limit to the number of points that the plots will show. It depends only by the ram memory of the computer.


In the settings page user can program the following parameters:
  • HV ON/OFF: switch on/off the HV power supply using the programmed ramp
  • HV Voltage: Set the desidered HV voltage
  • HV mode: Select between Digital and Temperature Compensate. When Temperature Compensate is selected, the SiPM HV voltage will be automatically adjoust to correct the temperature drift changing.
  • Compliance (Vout): set the maximum Vout. If the ADC measure an higher voltage, the HV setpoint will be adjoust to limit the output voltage
  • Over current protection: If the output current overcomes this limit the HV output is immediatly switched of without any ramp. This is not a current limitation but a protection system to limit the current in case of short circuit or if the SiPM matrix is accidentally exposed to ambient light while it is powered on
  • Ramp Speed: Ramp up/down applied to the HV voltage to limit the derivate of the HV to do not damage AC coupled ASIC IC
  • SiPM temperature Coefficient This coefficient is applied to the HV output voltage reducing or increasing the nominal HV voltage by the following formula Vout = Vset - Tcoef*(T-25)
  • For example, if Vset = 50v, Tcoef =50mV/°C and T=35°C Vout will be corrected of 500mV. So the Vout = 49.5v
  • HV Output on startup: select the status of the HV when the power is applied to the NIPM13 device. If user wants to operate without ethernet connection to the device, it is possible to set HV output voltage and select Power ON in the HV Output on startup.