=Paper=
{{Paper
|id=Vol-2507/142-146-paper-24
|storemode=property
|title=The New Data Acquisition System MPD-32 for the High-Resolution Fourier Diffractometer at the IBR-2 Pulsed Reactor
|pdfUrl=https://ceur-ws.org/Vol-2507/142-146-paper-24.pdf
|volume=Vol-2507
|authors=Andrey Bogdzel,Vladimir Drozdov,Vladimir Kruglov,Svetlana Muraskevich,Valentin Prikhodko,Vasilii Shvetsov
}}
==The New Data Acquisition System MPD-32 for the High-Resolution Fourier Diffractometer at the IBR-2 Pulsed Reactor==
https://ceur-ws.org/Vol-2507/142-146-paper-24.pdf
Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
THE NEW DATA ACQUISITION SYSTEM MPD-32 FOR THE
HIGH-RESOLUTION FOURIER DIFFRACTOMETER AT
THE IBR-2 PULSED REACTOR
A.A. Bogdzel, V.A. Drozdov, V.V. Kruglov, S.M. Murashkevich,
V.I. Prikhodko, V.V. Shvetsova
Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 6 Joliot-Curie,
Dubna, Moscow region, 141980, Russia
E-mail: shvetc_vas@mail.ru
In the Laboratory of Neutron Physics a new high-performance data acquisition system (DAQ)
is being developed in the framework of the project on creation of a high-aperture backscattering
detector (BSD) for the high-resolution Fourier diffractometer HRFD.
The designed increase in the BSD aperture of 12.5 times and an increase in the neutron flux on
the sample of 2-3 times due to employment of the new neutron guide, demand raising the neutron
registration rate to ~ 3*107 n/s [1]. Time encoders, besides signals from the multielement scintillation
detector BSD, also digitize pick-up signals from the chopper as well as of reactor startups that are
transmitted to the computer in the list mode to be recorded on the disk for further processing. This has
required development of new electronics and programs as the MPD-240-based DAQ system used
today has the neutron registration limit on the level of ~ 106 n / s.
Earlier, in order to increase the transmission capacity of data acquisition systems with a USB-
2 interface for the IBR-2 spectrometers, the FLINK USB 3.0 was developed [2] to provide links
between the modules having an optical interface with a computer according to the USB 3.0 protocol.
This has solved the problem of increasing the performance of the DAQ systems for all the
spectrometers except those for the HRFD that has undergone modernization. This work presents the
results of development of a high-performance data acquisition system on the basis of MPD-32 blocks
integrated into a common system of a high-speed interblock interface and a USB 3.0 computer
interface with an optical fiber extender.
Keywords: Data acquisition system, high resolution, neutron diffraction, back-scattering
detector.
Andrey Bogdzel, Vladimir Drozdov, Vladimir Kruglov,
Svetlana Muraskevich, Valentin Prikhodko, Vasilii Shvetsov
Copyright © 2019 for this paper by its authors.
Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
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Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
1. Introduction
The IBR-2 reactor is equipped with a unique complex of neutron spectrometers allowing a
wide range of studies. At present, 18 spectrometers operate, or are in the final stage of development at
the reactor. Fourteen are used for condensed matter research, two for nuclear physics research, one for
radiation material science, and one for neutron activation analysis. This paper describes the results of
development of the DAQ for the new large-area BSD detector at HRFD
The High-Resolution Fourier Diffractometer (HRFD) developed in the framework of
collaboration between FLNP JINR (Dubna), PNPI (Gatchina) and VTT (Espoo, Finland) has been
operating at the IBR-2 reactor since 1995.
Nowadays а wide-aperture backscattering detector [fig. 1] for the HRFD diffractometer is
being developed in FLNP. In the past few years, some of the key HRFD units, that became morally
obsolete or worn out, have been replaced. Specifically, in 2016 a new mirror neutron guide and a fast
Fourier chopper were put into operation and in the previous years, there was complete replacement in
the data acquisition and experiment control electronics [3].
Next priority in the HRFD development plan is the forthcoming replacement of the two
existing backscattering detectors (BSD) by a new large-area scintillation detector with a total area of
sensitive elements of about 13m2. The planned BSD aperture increase by a factor of 12.5 and an
increase in the neutron flux on the sample by a factor of 2–3 due to the use of a new neutron guide
require raising the neutron detection rate to ~ 107 n/s. This requires an increase in the throughput of
data acquisition system up to 400 MB/s.
Figure 1. Wide-aperture back-scattering detector
2. Hardware
A general approach to developing new data acquisition systems for our spectrometers is to use
and develop unified blocks, unified standards, and unified software. As a result, the systems installed
on different spectrometers have a unified structure. Such unification can be realized because the main
method is the time-of-flight method for measuring the energy of the detected neutrons. Also,
scintillation, gas or position sensitive counters are used as detectors in all the spectrometer set ups.
The data acquisition system could be constructed based on one or two types of basic electronic
modules, one of which (De-Li-DAQ) processes and accumulates data from a one- or two-coordinate
PSD, and the other (MPD-240) collects data from multielement detectors [4].
Nowadays, the MPD-240 DAQ (Fig. 2) is used on HRFD for high resolution data acquisition.
The MPD-240 unit allows event-by-event data acquisition (list-mode). In this case, during on-line
measurements the MPD-240 system provides transmission of raw data from the reactor pulse, chopper
pick-up signals, and from an array of detector elements for their subsequent off-line processing.
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Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
To input the data from the reactor pulse and the pick-up signals, there are made additional
inputs on the front and back panels of the unit. To input the detector signals, one 32-channel
discriminator module is used.
Such MPD-240 data acquisition systems are now used on three Fourier diffractometers,
HRFD, FSD, and FSS.
Figure 2. The MPD-240 and the 32-Chanel Discriminator
This DAQ has a hardware limitation on the neutron registration rate of 106 n/s. Thus, it cannot
provide high resolution data acquisition from the BSD under development. This issue requires
development of a new high performance DAQ with a bandwidth of transmission channels of 400
MB/s.
To this end, a new MPD-32 module (Fig. 3) is being developed at FLNP. The MPD-32
module combines the functions of a 32-channel discriminator and a time-of-flight encoder of detector
signals. New MPD-32 modules can be made by upgrading 32 existing channel discriminator modules.
The digital part is constructed on the basis of two FPGA, one of which is the time-of-flight encoder
FPGA and the other is the communication controller FPGA.
Start
A
Pick-Up
B USB 3.0
16 USB 3.0
to FIFO
Encoder
Z bridge
TOF
Communication
D1 LVDS
http://www.nvtc.ee/e-oppe/Sevtsenko/images/
Controller
differential%20transferring.gif
16
Ser
D32 16 Des
DAC
I2C
x 32
32-Chanel Discriminator
Figure 3. The MPD-32 with a 32-chanel discriminator
Signals from preamplifiers of detectors pass through an analog-digital functional block which
receives, discriminates and transmits signals to the time-of-flight encoder FPGA. The TOF encoder
FPGA is used to encode signals from 32 detector elements, to register their appearance time, to
convert the received data from parallel to serial bit stream form, and to transfer them through the
LVDS port to the communication controller FPGA at a speed of about 800 Mbit /s. The
communication controller FPGA performs the functions of receiving and buffering data from all
detector elements and of transferring the generated data packets to the computer memory via a fast
serial link or via USB3.0. Fast serial links are used to integrate several MPD-32 modules into a
common DAQ system with the required number of channels. The structure of MPD-32 module is
shown in figure 3.
Main features of MPD-32:
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Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
MPD-32 allows one to organize the data acquisition system that meets the requirements of all
types of multipoint detector systems of neutron spectrometers at the IBR-2M reactor;
MPD-32 combines a discriminator and an encoder for 32 analog inputs;
USB3.0 interface with an optical fiber extender;
High speed (2.5 Gb) interblock linking;
Range of analog input signals 0÷2V p-p, with selectable polarity;
Programmable thresholds of discriminators in the range of 30 ÷ 400 mV with 8 bits ADC;
Maximum number of detector elements 32 for one MPD-32 in the system;
Maximum detection rate = 3 x 107 events/s;
Events are recorded in absolute time of experiment, max. exposure time = 4.5 x 106 s (length
of time counter = 48 b);
Registration of service signals with the same accuracy as that of detector elements: such as
start of reactor, start/end of time window, end of exposure, etc.;
Registration of additional 6 external signals for example PICK-UP Fourier chopper signals on
the HRFD diffractometer;
Time digitization rate – programmable (maximum 62.5 MHz).
Some functions and parameters are the same as those of MPD-240 [5].
3. Architecture of the new DAQ system
The architecture of the MPD-32-based DAQ system is constructed on the basis of 8 modules
integrated into a common system to ensure operation of 216 PMTs of the BSD. The number of
modules can be 8 at minimum or 12 for more convenient determination of signals from 12 sectors of
the detector. One sector of BSD provides operation of 18 PMTs. Figure 4 shows the structure of the
data acquisition system for the detector under development [6].
Every module will be made to suite any type of spectrometers with multi-point detectors at the
IBR-2 reactor and can be used as a «master» or «slave» module.
The «slave» modules can be connected successively through the High-Speed Fast Serial Link
which provides inter-block data exchange at the speed 2.5 Gb/s.
The «master» module is connected to the computer via a USB 3.0 fiber optic extender. Such
extender allows operation of the USB 3.0 interface in the super speed mode with a fiber of up to 300
meters long as required for the IBR-2M spectrometers.
The data from the TOF Encoder FPGA is formed into packets containing the detector number
and the module number. In the case when 12 modules are used, their number matches the number of
sectors. The Encoder digitizes the pick-up data of the chopper signal and of the reactor start signals for
subsequent spectra processing using the RTOF correlation method. Then the generated packets are
transferred to the FIFO leveling buffer of the Communication Controller FPGA.
Figure 4. The variant of the architecture the DAQ system for BSD
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Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
4. Conclusion
Development of MPD-32 is one of the main tasks in connection with meeting the needs of the
new wide-aperture detector on the HRFD neutron spectrometer that is to be further optimized for
operation on other IBR-2M reactor spectrometers. To date, five test samples have been developed for
software and communication interface debugging.
References
[1] A. Balagurov et al. «High-resolution neutron Fourier diffractometer at the IBR-2 pulsed reactor:
A new concept». Nuclear Inst. and Methods in Physics Research B 436 (2018) 263–271;
[2] V.V. Shvetsov, V.A. Drozdov. «Increasing Bandwidth of Data Acquisition Systems on IBR-2
Reactor Spectrometers in FLNP». Proceedings of the XXVI International Symposium on Nuclear
Electronics & Computing (NEC’2017) Becici, Budva, Montenegro, September 25 - 29, 2017,
European repository of the CEUR Workshop Proceedings Vol-2023, pp. 293-298;
[3] S.A. Kulikov, “Development of a wide-aperture backscattering detector (BSD) for the HRFD
diffractometer” Report on the 46th meeting of the PAC for Condensed Matter Physics, JINR June 20–
21, 2017;
[4] S.A. Kulikov and V. I. Prikhodko. «A New Generation of Data Acquisition and Data Storage
Systems of the IBR-2 Reactor Spectrometers Complex». Physics of Particles and Nuclei, 2016, Vol.
47, No. 4, pp. 702–710;
[5] F. Levchanovskiy and S. Murashkevich, “A data acquisition system for neutron spectrometry–the
new approach and the implementation,” in Proceedings of the NEC’2013. JINR E10. 13-2013-136.
(Joint Institute for Nuclear Research, Dubna, 2013), pp 176-179;
[6] V. Kruglov et al. «Development of a new wide-aperture backscattering detector (BSD) for the
HRFD diffractometer on IBR-2 facility». Poster presentation on European Conference on Neutron
Scattering (ECNS 2019), Saint Petersburg, Russia, July 2, 2019.
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