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Automated Measurements and Data Processing for Laboratory Exercises in Nuclear Physics

Authors: Toskov B. P, Petrov A. G., Antonov A. D.The Paisii Hilendarski University of Plovdiv

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      IntroductionThe equipment used to provide laboratory experiments in educational laboratories in nuclear physics has the following characteristics:·Relative simplicity of hardware; Possibility for using various types of detectors;·Moderate rate of data acquisition;·Performance of various tasks on the same hardware;·Possibility for automation of data acquisition and data processing;·Option for working in computer network and data exchange;·Using standard software as well as specially developed one;· Possibility for future adaptation to other tasks;· Simplified usage.

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Main goals of the development:

Creation of a rather simplified but intelligent interface module for data acquisition and data transmission to PC; Adaptation of standard software (MS Excel, Table Curve etc.) for data processing as well as development of specialized software for more convenient planning of the experiments and solving of more specific tasks.

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Contents of the hardware:

Measuring probe including detectors;Standard radiometer Robotron 20046;Interface module;Personal computer IBM PC/AT or similar.

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Tasks of the radiometer:

Connecting, HV power supply and data collecting from various types of detectors;Ensuring of proper amplification, forming and amplitude selection of the detector’s pulses;Manual setting of measurement time and generating of START/STOP signals; Possibility to be replaced by another type of radiometer with similar possibilities.

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Tasks of the Interface module:

Ensuring the reception of formed pulses from the radiometer;Preliminary pulses counting;Saving the data in 16-, 32-bits or more extended format;Providing logical compatibility with the ports of PC for the following data transmission to it;Used ports: COMx via RS-232 or keyboard port. Operation in several modifications.

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Tasks of the PC:

Receiving the data from IM;Data processing according to the conditions of the performed experimental task;Representation the results;Possibility for application either standard or special developed software;Communication with other PC (if works in Network).

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Properties of the interface module (IM)

Based on MC PIC16F874;Communication with PC via RS-232 or keyboard port (keyboard emulation);Levels conformation with ICL232;Easy FLASH reprogram-ming by the option ICSP via 2 pins by means of programmer unit.

Microchip PIC16F874

+ Software

Async.Timer

Module

I/OPorts

10 bitADC

ICL232TTL toRS-232

PowerSupply

Fig.1

InterfaceModule

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The main functions performed by IM:

Data receiving from the measuring probe through the radiometer for the time adjusted manually or by PC software;Saving the data in 16-, 32-bits or more extended format;Data transfer to PC after finishing the current measurement upon a control signal STOP from the radiometer or via a command from the PC;Preparation for the next measurement;Possibility for working in several modifications, ensuring various measurement modes and transmissions to PC.

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Module operation mode-1Program control of the measurements (fig.2):PC software sets the time and the number of measurements and controls the measurement’s process in IM by RTS in RS-232;After finishing the measurement time the current portion of data is read by the PC via COM port and a new measurement is prepared; The advantages of this mode are the missing interrupt handling in PC and simplified communication interface.

Detec

tor Robotron

20046InterfaceModule

PCCOM Port

RxData

RTSStart and stop control

Fig.2

Personal computer

PCSoftware

Formedpulses

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Module operation mode-2Asynchronous mode (fig.3) The time of measurement is set manually in the radiometer;The signals START and STOP from the radiometer passes to IM;After measuring and entering a new signal START the internal counter is initialized and a new measurement begins;At the same time IM generates an asynchronous IRQ and sends it to PC, which causes a reading of information from IM; Ensures a higher speed of transmission but requires interrupt handling in PC.

Det

ecto

r

Robotron20046

InterfaceModule

PCCOM Port

RxData

Asynchronousdata acquisition

Fig.3

Personal computerControlsignals

PCSoftware

Formedpulses

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Module operation mode-3Bidirectional mode (handshaking mode-fig.4) Transfer protocol is required to be set beforehand ;Measurement the time set by PC in the interface module ;Possibility to set short time intervals of the measurement (below 100 s) ;The long time intervals require organizing more precisely the measurement of the time intervals;To solve this problem we could use the input for external quartz resonator in the microcontroller.

Det

ecto

r

Robotron20046

InterfaceModule

PCCOM Port

RxData Fig.4

Personal computer

PCSoftware

Formedpulses

TxData

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Module operation mode-4Keyboard emulation (fig.5) Connection to the keyboard input of PC (fig.8) ;The keyboard of the PC is connected through the IM via special input; Adjustment the measurement time by the radiometer ;Data transfer to PC on coming the STOP signal from the radiometer ; Transmission the data to PC in keyboard format (sequence of keyboard codes) ;Full independence on PC platform ; Direct entering the data to standard software (Excel, Word etc);Low speed of transfer limiting measurement time to 1s but not below.

Det

ecto

r

Robotron20046

InterfaceModule

Keyboardinterface

Fig.5

Personal computer

Controlsignals

PCSoftware

Formedpulses

IM-ON

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Communication formats-1

In mode 1, 2 or 3 via RS-232 (sequence of ASCII codes) – fig.6.

<Tab> and <CR> codes are convenient for better formatting in text programs.

09 3x 3x 3x 3x 3x 3x 0D

MSB LSB

<Tab> <CR>Decimal values

Fig.6

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Communication formats-2

A0 xx xx xx xxdata ID

Fig.7

data values

55 3x 3x AAtime ID time value start ID

A5

5A

ready ID

read ID

PCInterfaceModule

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Technical data of IM:

Supply voltage 5V;Consumed current 10mA;Communication:

VIA RS-232 (1200, 8, n, 1);VIA keyboard port;

Inputs/outputs – see fig.8;Input rate of counting –limited by the radiometer and the internal counter 20MHz.

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Software properties:The operation modes of IM is defined by control software, recorded previously in FLASH memory;The full package of control software is less than 1KB;In keyboard emulation mode (4) standard software is used (Excel, Word, Table Curve etc.)In case of usage RS-232 modes (1 – 3) special developed program systems are used – LABEX for DOS and LABEXWIN for Windows 9x+;LABEX is written on Turbo Pascal using standard package Turbo Professional;LABEXWIN is written on Borland Delphi.

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Exercises and general flow diagramExercises’ measurements:Halftime period of decay of shortliving isotopes;Beta/gamma rays energy by the absorption method;Working characteristics of G-M counters;Statistical character of the radioactive decay (Poisson’s and Gauss’ laws);Cross section of interaction of fast neutrons with lead, iron and other metals nuclei and evaluation of nuclei sizes.Both program systems include mathematical methods (LSM, statistical etc.) for data processing and wide possibilities for graphical representation of results.

start

task choice and settinginitial parameters

PC control?

set up measurementparameters

measurementsare finished?

data receiving andprocessing

results representation ingraphical or text format

stop

no

no

yes

yes

fig.9

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Conclusions

The present-day microcontrollers give opportunities for the creation of new types of nuclear electronics’ devices. To this aim it is enough the developers to be acquainted with the architecture of microcontrollers and with the method of its programming.

The above described interface module can be used in various automated radiation measurement devices and systems and the application software may be adapted to them. This development is a useful step toward automation of educational experiments in atomic and nuclear physics.

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References:[1] Microchip microcontrollers – http://www.microchip.com [2] Interfacing the AT keyboard - http://www.beyondlogic.org/keyboard/keybrd.htm[3] AVR313: Interfacing the PC AT Keyboard - http://www.atmel.com[4] Balabanov N., Petrov A., Mitrikov M., Srentz A., Antonov A. A Practical Guide for Laboratory Exercises in Nuclear Physics, Plovdiv, 1988 (in Bulgarian).[5] Antonov A., Balabanov N., Mitrikov M., Marinova S., Srentz A., Toskov B., Hristov H., Tcholakov V. A Practical Guide for Laboratory Exercises in Atomic and Nuclear Physics, PUI, Plovdiv, 2002 (in Bulgarian).