Automated Control System for Radiation-Chemical Processof Composite Materials Formation*
G.F.Popov, A.I.Kalinichenko, and Yu.A.Kresnin
Kharkov State University, P.O.Box 60, Kharkov 310052, Ukraine
Abstract

2 Radiation facilities for PCM formation

A real-time control system is designed for radiationchemical process of polymer composite materials (PCM)
formation. PCM are manufactured by the bulk impregnation of solid capillary-porous materials, such as wood,
gypsum, ceramics, concrete, tuff by monomers or oligomers, and subsequent polymerization under effect ofbremsstrahlung or scanning electron accelerator beam withenergy of 5-10 MeV, time duration of 4 mcsec., and mean
beam power of 5 kW. The experimental results, which
demonstrate the control system′s utilization for the production of various PCM with extended strength properties andcorrosion resistance, are discussed.

Let′s consider a process of fabrication for polymer
modified wood as an example of the use of radiation chemical treatment of capillary-porous materials. In our
opinion, it is the favorite PCM, which has vast application.
We can, through programming, modify its operational
characteristics, as well as physical-mechanical properties.
As a starting material for polymer modified wood, one canuse soft low-grade wood poplar, aspen, alder, birch. Afterradiation - chemical treatment this wood acquires better
physical-mechanical characteristics than those of thehardest and most expensive sorts of wood, namely, oak,beech, hornbeam.

1 Introduction
At Kharkov State University the radiation-chemical process of polymer composite materials formation wasdeveloped [1-3]. The general technological scheme of
PCM production consists of impregnation by synthetic
monomer or oligomer of articles made of capillary-porous
materials such as wood, gypsum, concrete, ceramic, paper,
as well as pressed granular waste of papermaking, textile
and wood-working production. These are further treated byrelativistic electron or bremsstruhlung beams. Such
radiation treatment yields new PCMs in which thecapillary-porous structure acting as reinforcement is filledwith polymer. New compo-site materials (wood-plastic,
gypsum polymer, organic concrete) obtained by theradiation-chemical process have qualities such as highstrength characteristics, low water and moisture absorption,high stability of form and size, chemical and bioresistance; resistance to attack of atmospheric factors,
corrosive media, abrasion loads.
The comprehensive investigation of the kinetics andthermodynamics of the radiation-stimulated polymerizationof monomers/oligomers in heterogeneous media was performed. It was found experimentally that the following
parameters have an effect on the end composite material
properties: characteristics of the radiation (type of particles,
their energy, dose rate and integral dose); relative
concentrations of filler and saturant; characteristics of thefiller (strengths and elasticity, specific pore volume,
configuration and size of pores); characteristics of appliedchemicals (monomers, oligomers, solvents, initiators, sensitizes, catalysts); some external conditions (temperature,pressure). The authors developed a control processing
system for optimizing the radiation treatment of compound(monomer / oligomer capillary-porous material) byelectron/ bremsstrahlung radiation.
* Research supported by STCU, Grant # 155.

Fig. 1 Technological scheme of polymer-modified wood
production.
The technological scheme of polymer-modified wood
production is shown in Fig.1. The radiation facilities forpolymer composite material formation incorporates a linac
with scanning electron beams, microwave chamber for the
drying of the materials, an evacuation system, a system forthe impregnation of materials with synthetic monomers/
oligomers, a test bench for irradiation of samples, equipment for monomer/oligomer and gas cleaning, andequipment for working the PCM (cutting, grinding, andpolishing). The drying of raw materials was executed in a
vacuum or/and in a microwave field.
The stage of radiation treatment of the compound is themost complex. At the same time it determines the quality

of the produced PCM and the productivity of the radiationchemical installation. The main problems of this stage are
the formation of a uniform three-dimensional irradiation
field, and an optimal regime for the maintenance of theelectron or bremsstruhlung beam. The latter varies
according to prescribed low during the radiation treatmentof compound. The required time, t, for performance of theradiation-chemical polymerization process is between 5
and 30 min. depending on the compound composition.
The experimental radiation-chemical installation, as
shown in Fig.2, consists of an electron accelerator withelectromagnetic scanner, an electron beam monitor, aclosed container with the modified materials, and theprocess control system. As a source of the scanningelectron beams, a linear accelerator of the type "Electronica- U003" is used with following characteristics: electronenergy 5-8 MeV; electron beam current 0.5 mA; mean
beam power 5 kW; pulse duration 1-4 mcs; pulse frequency
1-250 Hz; scanning frequency of electromagnetic scanner
1-8 Hz; the deviation angle of scanning electron beam waswithin ± 20o ; the irradiation is possible both with electron
and bremsstrahlung beams. The bremsstrahlung radiation

was generated by an electron beam in a tantalum converter
which was placed in front of the container.
3 Structure of the process control system
The process control system incorporates a set of acoustic(AS) and temperature (TS) sensors, a CAMAC crate (CC),a subsystem for the control of the radiation-chemical
process (CSR-CP), a container displacement subsystem(CDS); a beam monitoring system (BMS), an electron
accelerator control subsystem (ACS), a scanner control
subsystem (SCS), a synchronization module (SM), and an
IBM-compatible PC with corresponding software.
The accelerator control system ACS is connected to theaccelerator power source APS, which consists of a highvoltage source, a modulator, a magnetron, a phase shifter,
an electron injector and other elements.
The (CSR-CP) system includes AS3, TS1 and TS2
sensors, pre PA and main MA amplifiers, a DCA, a fast
FADC - and slow SADC analog-to-digital converters.
Signals from the sensors are transmitted in analog form by
100m coaxial cables to the FADC, SADC where analog-to-

Fig. 2 Block diagram of the radiation facilities for composite materials formation.
e- - pulsed beam of electrons; ES - electromagnetic scanner; M - scanning electron beam monitor; MM - sample ofmodified material; C - closed container; AS1, AS2, AS3 - acoustic sensors; TS1, TS2 - temperature sensors; PA preamplifier; MA - main amplifier; DCA - direct-current amplifier; FADC, SADC - fast and slow analog-to digitalconverter; SM - synchronization module; ACS - accelerator control subsystem; APS - accelerator power source; ACC accelerator control console; SCS - scanner control subsystem; VCC - voltage-to-current converter; G - pulsed generator;
BMS - beam monitor system; CDS - container displacement subsystem; CSR-CP - control subsystem for radiationchemical process; PD - peak detector; RCM - relay control modules; PS-X, PS-Y - position sensors; CC - CAMAC crate
controller.

digital conversion is performed. The system uses both theacoustic emission and temperature distribution created byionizing radiation in a sample MM, as a source of primary
information concerning the current status of the monomer/
oligomer phase state in the PCM.
The monitor M includes thin rods as its sensitiveelements with a piezoelectric detector AS2 on its butt-end,
an electronic preamplifier PA, an amplifier MA, and abeam monitor system BMS.
Remote movement of the container C with modify
material samples MM, is carried out with RCM by
servoactuator, with controlled displacements along axes X
and Y in plane (X, Y), which is perpendicular to beam axis.
Acoustic sensor AS1, PA and PD serve for emergency
protection of the accelerator beam-transport pipe against
damage from a high-current beam. When the acoustic
signal amplitude exceeds a preset limit, the accelerator
injector is disabled.
The acoustic waves are detected by broadband
piezocera-mic ( ∆f ≤ 10 MHz) sensors AS1-AS3 withsensitivity of 10 V/Pa, placed on a sample of modified
material MM, on the beam monitor M, and on theaccelerator elements, e.g., on foil of the accelerator outlet
window. These sensors have high sensitivity and radiation
resistance and their construc-tion provides protection
against electro-magnetic inter-ference.
Analog-to-digital conversion is realized by fast 8-bit
digital quantizer TDA8703 (Philips Semiconductor) having
a maximum sampling frequency of 40 MHz. The frequency
band of the restored signal on digital quantizer input is 0 to
5 MHz.
Chromel- capel thermocouples having a thermopower of
0.064 mV/ 0C and nonlinearity of 8% in the temperature
range of 0 to 200 0C are used as temperature sensors TS1
and TS2 placed on the sample surface. Analog-digital
signal conversion is realized by 8-bit digital quantizer
ADC0808CCN (National Semiconductor) with integrated
8-channel multiplexer. The conversion range is 0 to 10 V
with a quantization step of 40 mV. Calibration curves ofthe sensors being used are stored in the computer memory
and are employed for shape reconstruction of the sensor
signals.
4 Control system operation
In order to obtaining high quality PCM by radiationchemical polymerization one should maintain thecompound temperature Tc in the range of 80 to 100 0C. At
continuous electron beam intensity Ie(t) = const
temperature Tc can increase up to 200 0C due to process
exothermicity, which causes PCM destruction. But wefound optimum regimes of intensity variation Ie (t)opt when
Tc does not exceed of 1000C
We designed physical methods for the control anddiagnostics of the kinetics of the radiation - chemical
polymerization of compound. These real-time methods
provide simultaneous registering the following parameters:
the heat release during exothermic reaction of radiationchemical polymerization of compound that leads toincreasing its temperature T; the amplitude of the acoustic

signal V generated by radiation in the sample of modified
materials; dose D and dose rate of radiation.
When a pulsed electron beam passes through the sample
of modified material and the accelerator constructive
elements, rapid heating and thermal expanding of theirmaterials takes place. Herewith generated acoustic waves
carry information concerning beam parameters and interaction spot location [4, 5]. The amplitude V, time andfrequency characteristics of these waves also carryinformation about the kinetics of the phase transition(monomer/oligomer −polymer), namely, about the stage,
the phase location and the concentration, as well as thermophysical and thermoelastic characteristics of composites[6,7].
The operation of the process control system based on thephase state monitoring of processed material MM resulting
from the measurement of the sample temperature T and theacoustic pulse amplitude V on dose D, intensity je and time
t of irradiation. These data permit controlling of the technological installation parameters to support the optimal
regime of the radiation treatment by the ACS, BMS, andSCS subsystems. The optimum values of the measured
temperature Topt(D,t) and of the acoustic signal amplitude
Vopt(D,t) for various monomer/oligomer−capillary−porous
material systems and regimes of bremsstrahlung or electron
irradiation are stored in the memory of the control
computer. They can be corrected in the course of data
storing, including the automatic regime. In the case of
departure of the measured parameters T(D,t) and V(D,t) of
optimum values Topt(D,t) and Vopt(D,t), the ACS, BMS,
and SCS subsystems change scanning beam parameters tomaintain these values.
5 Beam monitor system
Thermoacoustic one dimensional monitors M on thebase of thin rods and plates were used in the control systemof the scanning electron and bremsstrahlung pulsed beams
in the technological process. The monitors arecharacterized by high informativity, simplicity andreliability of construc-tion. The monitor provided
continuous, nondistorting acoustic dosimetry of theextensive area under pulsed radiation.
The monitor with ramifying body was displaced
normally to initial direction of electron beam axis. Its bodyconsisted of one or a few parallel titanium wires 140 cm
long. The wire diameter d , as well as its material, ischosen from conditions d << min{D, E e / χ }, to provide
nondistorting dosimetry. Here Ee is electron energy, χ specific energy loss of beam electron.
When a sequence of electron pulses passes through therectilinear body of the dosimeter, a sequence ofthermoacoustic waves appears in it. In the approximationof instantaneous heating τ b << D / s the stress wave
amplitude V (t ) generated in dosimeter body by either
electron pulse, is proportional to the spatial distribution ofdeposited energy. The sequence of thermoelastic waves
goes to a wide-range piezoelectric detector, which

transforms these into electric signals and is displayed by aregister device, operating in accumulation mode.
Each of the acoustic pulses, generated in the dosimeterbody by the accelerator pulse sequence, carried theinformation about the location and the transverse
distribution of the corresponding electron pulse. The
registration and the processing of the output signal was
executed by the BMS. As a result, a spatial profile of aradiation field je, caused by any periodic shape of current
in the scanning magnet ES, was displayed immediately (seeFig. 3). It permitted fitting the profile je, to a desired shapeby varying the shape of magnet current with help of a
voltage-to-current convertor VCC, a pulsed generator G,
and the scanner control subsystem SCS.

Figure 3. Scheme of utilization of a wire acoustic
dosimeter for the monitoring of a scanning electron beam.
The current in the scanning magnet had sinusoidal form.
6 Software
The software of the control system fulfills the following
functions: delivers information concerning the initial
regimes of beam parameters for any composition anddimensions of processed compound to the operator;
displays information concerning the radiation parametersand calculates a dose profile in the modified material;
determines the current status of the manufactured material;
maintains the optimal regime of the radiation treatment;
determines the termination time of polymerization process;realizes the remote manoeuvring of the modified samples;
leads the experiment record; stores statistical information.
Besides, the application package performs: the control of
the CAMAC crate moduli, and the graphic display ofrecorded data on the monitor screen, including thebroadband thermoacoustic signals from the radiationacoustic probes, and the slowly-changing signals from thetemperature probes are displayed; the graphic display ofthe calculated values and the curves; the control andoperation of the processing parameters, namely, thetechnological container coordinates; the registration ofprocessing para-meters, as well as, of control-administer
information; the submission of technological and reference
information, the formation and control of the processing
data base. The language C was used for the development of
this software.
7 Radiation treatment of compounds
The large-sized samples of modified materials MM(nearly 100x50 cm) were treated by the scanningelectron/bremsstrahlung beams in the radiation facilities(see Fig.2). The samples, more than 100 cm, and weretreated by shifting step by step transversely to the electron
beam. The uniform radiation flux distribution on the large
area (nearly 100 x 40 cm) of the PCM samples was createdby the scanning system with a special form of currenthistory in a scanning magnet.
Two-sided irradiation of the thick PCM samples or
sample stacks, whose thickness is more than the electron
range, was used to increase the beam utilization coefficientand to increase the installation productivity. The main goalof the optimization of the production process is to increase
the capacity of the plant per unit of power of ionizing
radiation. It is attained by the use of computer modelingand a precise does measurement system in the bulk of theirradiated material
Figure 4a and 4b represent the distribution of theelectron and bremsstrahlung dose along the depth of thetwo-sided irradiated compound (wood of aspen + 70 %MMA). Curves 1, 2, 3 in Fig. 4(a) correspond to electronenergies of 4, 6 and 8 MeV for two-sided irradiation.
Curves 1, and 2 in Fig. 4(b) correspond to two, and onesided irradiation of the modified wood. The bremsstrahlung
radiation was generated by an electron beam with energy of
5 MeV in tantalum convertor.
Optimal thickness of the PCM articles treated byelectron/bremsstrahlung beam with one-and two-sided
irradiation was determined. We choose the optimal thickness of the PCM that corresponds to the most uniform
distribution of electron/bremsstrahlung dose.
For example, for wood the optimal thickness depended
on the kind of wood, type of monomer, on the degree of
impregnation of wood by the monomer and on the electronenergy. Optimal thickness of the PCM article with adensity of 0,6-2 g/cm3 treated by electron/bremsstrahlung
beams of two-sided irradiation was in the range (3-8cm)/(12-60 cm).
The power possibilities of the linear accelerator withelectron energy 5-10 MeV and beam power 5-10 kW
permitted us to design and develop an experimental
installation for the manufacture of corrosion and highresistant building materials, such as parquet planks,
window and door frames, construction for chemicallycorrosive conditions, etc. For example, such a pilot-plant
equipment would be able to output 20 - 40 thousands
square meters per year of modified parquet planks. The

strength characteris-tics, corrosion resistance and abrasionloads of this modified parquet made of low value kinds ofwood (aspen, alder, poplar, birch) exceeds natural hardwoods (beech, oak, hornbeam, yew and the like).

(a)

(b)

aggressive environments; preservation andantiquities.

restoration of

8 Conclusion
A versatile universal system for monitoring of radiationchemical processes has been developed. The system isbased on the use of radiation-acoustic effect, namely, theinformation which is carried by thermoacoustic pulse
amplitude generated in the pulsed material irradiation in
the course of radiation-chemical process. This information,
as well as data delivered by other independent probes, and,systems measuring temperature, pressure etc., permits thecontrol of the phase state of the manufacturing materials, ofthe temperature regime of processing and of the final
material quality. The system can be used forcomprehensive control of kinetics and thermodynamics ofradiation-stimulated polymerization of monomer-oligomer
in heterogeneous medium under action of pulsed electronor bremsstrahlung beams, including scanning beams. Suchcontrol permits the provision of the optimum regime of theradiation-chemical process, which leads to higher qualityof the end products,
References

Fig.4 Distribution of electron (a) and bremsstrahlung (b)dose with depth in irradiated compound (wood of aspen +70 % methylmethacrylate).
The high waterproof, hardness, and shape stability, highdielectric and thermoinsulation characteristics, chemicaland biological durability, and perfect ornamental properties
allow the materials to be used in the production of parquet
flooring, window and door frames, constructions forchemically corrosive conditions and for inclement climate;
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