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IVVS actuating system compatibility test to ITER gamma radiation conditions
Fusion Engineering and Design 88 (2013) 2084–2087
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
IVVS actuating system compatibility test to ITER gamma radiation conditions夽 Paolo Rossi a,∗ , M. Ferri de Collibus a , M. Florean a , C. Monti a , G. Mugnaini a , C. Neri a , M. Pillon a , F. Pollastrone a , S. Baccaro b , A. Piegari b , C. Damiani c , G. Dubus c a
Associazione EURATOM-ENEA sulla Fusione, 45 Via Enrico Fermi, 00044 Frascati, Rome, Italy ENEA CR Casaccia, 301 Via Anguillarese, 00123 Santa Maria di Galeria, Rome, Italy c Fusion For Energy c/Josep Pla, n◦ 2 Torres Diagonal Litoral, 08019 Barcelona, Spain b
h i g h l i g h t s • ENEA developed and tested a prototype of a laser In Vessel Viewing and ranging System (IVVS) for ITER. • One piezo-motor prototype has been tested on the ENEA Calliope gamma irradiation facility to verify its compatibility to ITER gamma radiation conditions. • After a total dose of more than 4 MGy the piezo-motor maintained almost the same working parameters monitored before test without any evident and significant degradation of functionality.
• After the full gamma irradiation test, the same piezo-motor assembly will be tested with 14 MeV neutrons irradiation using ENEA FNG facility.
a r t i c l e
i n f o
Article history: Received 14 September 2012 Received in revised form 19 February 2013 Accepted 14 March 2013 Available online 6 April 2013 Keywords: IVVS Remote handling Laser beam Piezo-motor Gamma radiation
a b s t r a c t The In Vessel Viewing System (IVVS) is a fundamental remote handling equipment, which will be used to make a survey of the status of the blanket first wall and divertor plasma facing components. A design and testing activity is ongoing, in the framework of a Fusion for Energy (F4E) grant agreement, to make the IVVS probe design compatible with ITER operating conditions and in particular, but not only, with attention to neutrons and gammas fluxes and both space constraints and interfaces. The paper describes the testing activity performed on the customized piezoelectric motors and the main components of the actuating system of the IVVS probe with reference to ITER gamma radiation conditions. In particular the test is performed on the piezoelectric motor, optical encoder and small scale optical samples .The test is carried out on the ENEA Calliope gamma irradiation facility at ITER relevant gamma fields at rate of about 2.5 kGy/h and doses of 4 MGy. The paper reports in detail the setup arrangement of the test campaign in order to verify significant working capability of the IVVS actuating components and the results are shown in terms of functional performances and parameters. The overall test campaign on IVVS actuating system will be completed on other ENEA testing facilities in order to verify compatibility to Magnetic field, neutrons and thermal vacuum ITER typical environmental working conditions. © 2013 Euratom-ENEA Association sulla Fusione. Published by Elsevier B.V. All rights reserved.
1. Introduction The In Vessel Viewing System (IVVS) is a fundamental remote handling equipment, which will be used to make a survey of the status of the blanket first wall and divertor plasma facing components in ITER before first plasma and between plasma operations.
夽 Disclaimer: The views and opinions expressed herein are the sole responsibility of the authors and do not necessarily reflect those of Fusion for Energy, the European Commission or the ITER Organization. Fusion For Energy is not liable for the use which might be made of the information in this publication. ∗ Corresponding author. E-mail address: [email protected] (P. Rossi).
A design and testing activity is ongoing, in the framework of a Fusion for Energy (F4E) grant agreement, to make the IVVS probe design compatible with ITER operating conditions such as high temperature, very high magnetic field, ultra high vacuum (UHV), neutron and gamma fluxes. In particular gamma radiation dose rate will be up to 5 kGy/h and environmental radiation integrated dose will be up to 10 MGy. Furthermore, the IVVS probe must be compatible with the geometrical constraints coming from the space allocated to the system and the port to access to the vacuum vessel. The most important IVVS mechanical function is laser beam steering and control. The probe steers the laser beam through a silica fused prism attached to the mechanical axes. By rotating the axes of the prism, the probe can scan any desired area and point in any direction. The back scattered signal is then processed
0920-3796/$ – see front matter © 2013 Euratom-ENEA Association sulla Fusione. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2013.03.030
P. Rossi et al. / Fusion Engineering and Design 88 (2013) 2084–2087
2085
Fig. 2. Piezo-motor prototype.
Fig. 1. IVVS rotating head with prism, piezo-motors and optical encoders.
to measure the intensity level (viewing) and the time of flight that gives the distance from the probe (metrology). Two optical encoders accurately measure the angular orientation of the probe’s two mechanical axes. ENEA already developed and tested a prototype of a laser In Vessel Viewing and ranging System for ITER [1,2] and studied also an updated conceptual design where the tilt and the pan rotation actuators are driven by a couple of ultrasonic piezo-motors (see Fig. 1). Commercial ultrasonic piezo-motors are intrinsically nonmagnetic and vacuum-compatible but must be customized to work at 120 ◦ C, to be backed at 200 ◦ C and verified under neutrons and gamma radiations. One piezo-motor prototype has been realized for the purpose by Physik Instrumente (see Fig. 2) and has been tested to verify its compatibility to ITER gamma radiation conditions. The test was performed on the motor, optical encoder and small scale optical samples and was carried out on the ENEA Calliope gamma irradiation facility at rate of about 2.5 KGy/h up to the required total dose of 4 MGy.
water level. The irradiation cell biological protection is realized in baritic concrete with thickness up to 180 cm [3]. The maximum dose rate is achievable along the longitudinal axis of the source rack. In particular on May 2012 nine Red 4034 Perspex dosimeters have been placed in the center of the source cage and irradiated for 17 h. Afterwards the dosimeters were read and a dose rate of 2301.3 Gy/h was determined with a total uncertainty less than 5%. This dose rate value, corrected for the decay time, is used to evaluate the total dose delivered to the various IVVS components which have been hanged along the longitudinal source axis inside a containing structure (see Fig. 3). The intent was to reach a total accumulated dose of 4 MGy in about 70 days of irradiation in order to verify working capability of the IVVS actuating components and in particular of the piezo-motor in terms of functional performances and parameters. 3. Piezo-motor test assembly The PI piezo-actuator under test is a rotary stage prototype consisting of two piezo linear devices U-164 preloaded against a ceramic friction ring. They work as a break when at rest while in operation they oscillate with ultrasonic frequencies providing a rotation of the ring. The motor was controlled by the PI singleaxis C-867.160 motor controller operated by a host PC via USB port by means of a LabView application.
2. Gamma test facility Calliope is a pool-type irradiation facility equipped with a 60 Co gamma source in a high volume (7*6*3.9 m3 ) shielded bunker. The source has cylindrical geometry with 48 source pencils placed on two concentric cylinders of about 20 cm outer radius and 26 cm height. The source during no irradiation operation is stored in shielded position inside a water pool. For the irradiation operation the source is lifted-up using a crane and placed on air above the pool
Fig. 3. Piezo-motor test assembly on Calliope Facility.
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P. Rossi et al. / Fusion Engineering and Design 88 (2013) 2084–2087
The active components, i.e. the motor, were remote monitored using Kapton® insulated cables going from the irradiation zone to a shielded area, where the data acquisition hardware is placed. DAQ system (National Instruments compactDAQ) has three I/O modules to acquire temperature from RTD sensors + rheostat information (module NI 9217, analog input), to acquire optical encoder information (module NI 9215, analog input) and to acquire micro switches (module NI 9401, digital input). DAQ system is connected to a personal computer in which the data are stored. The local control room is located in the building of the Calliope facility but it is possible to remotely control the system. 3.1. Test procedure
Fig. 4. Detail of piezo-motor test assembly.
The rotary stage has been fixed on a supporting structure and has been equipped with a shaft driving a mechanical gear and a rad-hard rheostat. The Rheostat (RT12 Vishay Sfernice) works as angular position transducer, while the shaft activates two mechanical micro switches (Burgess V3F, rad-hard) placed at about 200◦ angular distance (see Fig. 4). The gear works as the rotative component of a very robust optical encoder system where teeth are optically read by a couple of optical fibers (silica/silica 600 m core) placed at a distance of 1 mm. The encoder electronic driver includes a transmission system using an adjustable laser source (up to 100 mW) coupled to the transmitting optical fiber. The receiving optical fiber is coupled to an amplified photo-detector, necessary to amplify the very low level optical signal. A gain controlled amplifier is necessary to adjust the electrical output with the Data Acquisition System input requirements On the structure were also fixed the custom optical encoder and collimator designed for ITER IVVS probe, both made from borofloat glass, to be optically compared after test to ones not irradiated. A rad-hard temperature sensor (electrotherm Type K10-E-3LS-400) monitors any increment of the motor temperature during the irradiation test.
The target of the test is to evaluate the behavior of the piezomotor prototype under gamma irradiation conditions similar to those of the IVVS scanning movements on ITER environment. The motor runs clockwise (CW) and counter clockwise CCW) directions driving the rheostat which gives a resisting torque of 0.1 N m and pressing two micro switches CW and CCW which give an additional resisting torque of 0.09 N m. Then, to move the motor and correctly press the switches it is necessary an effective motor torque of at least 0.19 N m (some additional friction is given from the internal bearing). The motor and its driver has a single dimensionless characteristic parameter “motor out” which varies both the speed and the torque and determines the amplitude of the output voltage (peakto-peak value Vpp) [4]. A specific characterization of the motor system has been performed before test and then repeated twice each working day one hour in the morning and one hour in the afternoon. In each characterization the following characteristic values have been evaluated: (a) Minimum motor-out-value to move the motor in both direction without pressing the switches; (b) Minimum motor-out-value to move the motor and to press switches; In case of degradation of the motor functions, it was possible to recover the movement increasing the value of “motor out”. The motor movement was controlled and monitored remotely from ENEA Frascati laboratories trough a LabVIEW user interface
Fig. 5. Detail of LabVIEW application interface for piezo-motor gamma irradiation test.
P. Rossi et al. / Fusion Engineering and Design 88 (2013) 2084–2087
2087
Fig. 6. Motor-out values plots during gamma irradiation test of piezo-motor in both directions.
developed to present all the relevant data: temperature, movement information of the motor by the encoder, by the micro switches and by the rheostat. A relevant part of the user interface is shown in Fig. 5. 4. Test results Since the Calliope facility is not operative during August, the gamma test campaign has been performed in two phases: the first between 6th July and 3rd August 2012 and the second phase from 4th September to 12th November 2012. In Fig. 6 is reported how the characteristic values (a, b, in the previous section) have changed during the full irradiation test of 2222 h for a total dose of about 4.88 MGy. The sign of the motor-out-value determines the direction of the motion; It has been noticed, also before the irradiation start, that the motor has more strength in negative direction than in the positive one, resulting in two different motor-out-values. Anyway the motor-out-values in both directions didn’t vary significantly from the first motor characterization, done before gamma irradiation start, with average values of 18,000 and 16,000. Considering that the motor-out maximum value is 24,000, there is also a consistent margin to operate the motor. No recovery effect due to the period of no gamma irradiation has been noticed. In fact the characteristic values collected during the first days of the second phase are similar to previous. Moreover, considering that the nominal torque of a commercial rotary stage (PI M660, similar to the tested prototype) is 0.3 N m, the motor has been operated without any evident loss of performances at about 70% of its mechanical capability, which approximately corresponds to the ratio between the used motor-out value and the maximum one. The monitored temperature remained quite constant around 30.5 ± 1.5 ◦ C. The small variation is due to laboratory environmental conditions and seems not to be linked to any irradiation effect, given the low energy deposited by the gammas (2500 Gy/h correspond to 0.7 W/kg).
5. Comments The gamma irradiation test of the IVVS actuating components reached a total dose of 4.88 MGy, higher than the target of 4 MGy, without any evident and significant damages and degradation of the piezo-motor functionality. The piezo-ceramic rotation stage prototype has been able to provide enough torque to both ensure the movement and the closure of the switches during the whole test campaign completing about 90 characterization cycles of 1 hour each at about 70% of its torque capability and maintaining almost the same working parameters monitored before test. After the gamma irradiation test, the same piezo-motor assembly will be tested with 14 MeV neutrons irradiation using ENEA FNG facility [5]. The overall test campaign on IVVS actuating system will be completed on other ENEA testing facilities in order to verify also compatibility to magnetic field and thermal vacuum ITER typical environmental working conditions. Acknowledgments The authors wish to thank the Calliope operators A. Pasquali and G. Ferrara for their precious assistance during the experimental session. This work has been supported by Fusion for Energy under the grant agreement F4E-GRT-282. References [1] C. Neri, P. Costa, M. Ferri De Collibus, M. Florean, G. Mugnaini, M. Pillon, F. Pollastrone, P. Rossi, Iter in vessel viewing system design and assessment activities, Fusion Engineering and Design 86 (2011) 1954–1957. [2] C. Neri, L. Bartolini, B. Brichard, A. Coletti, M. Ferri de Collibus, G. Fornetti, et al., The laser in vessel viewing system IVVS for ITER: test results on first wall and divertor samples and new developments, Fusion Engineering and Design 82 (2007) 2021–2028. [3] S. Baccaro, A. Cecilia, A. Pasquali, ␥ irradiation facility at ENEA-Casaccia Centre (Rome), ENEA RT/2005/28/FIS, ISSN/0393-3016, 2005. [4] MS185E User Manual, C-867 PILine® Controller, Release: 1.1.0 Date: 07.12.2009. [5] M. Martone, M. Angelone, M. Pillon, The 14 MeV Frascati neutron generator, Journal of Nuclear Materials 63 (1993) 1661–1663.
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
IVVS actuating system compatibility test to ITER gamma radiation conditions夽 Paolo Rossi a,∗ , M. Ferri de Collibus a , M. Florean a , C. Monti a , G. Mugnaini a , C. Neri a , M. Pillon a , F. Pollastrone a , S. Baccaro b , A. Piegari b , C. Damiani c , G. Dubus c a
Associazione EURATOM-ENEA sulla Fusione, 45 Via Enrico Fermi, 00044 Frascati, Rome, Italy ENEA CR Casaccia, 301 Via Anguillarese, 00123 Santa Maria di Galeria, Rome, Italy c Fusion For Energy c/Josep Pla, n◦ 2 Torres Diagonal Litoral, 08019 Barcelona, Spain b
h i g h l i g h t s • ENEA developed and tested a prototype of a laser In Vessel Viewing and ranging System (IVVS) for ITER. • One piezo-motor prototype has been tested on the ENEA Calliope gamma irradiation facility to verify its compatibility to ITER gamma radiation conditions. • After a total dose of more than 4 MGy the piezo-motor maintained almost the same working parameters monitored before test without any evident and significant degradation of functionality.
• After the full gamma irradiation test, the same piezo-motor assembly will be tested with 14 MeV neutrons irradiation using ENEA FNG facility.
a r t i c l e
i n f o
Article history: Received 14 September 2012 Received in revised form 19 February 2013 Accepted 14 March 2013 Available online 6 April 2013 Keywords: IVVS Remote handling Laser beam Piezo-motor Gamma radiation
a b s t r a c t The In Vessel Viewing System (IVVS) is a fundamental remote handling equipment, which will be used to make a survey of the status of the blanket first wall and divertor plasma facing components. A design and testing activity is ongoing, in the framework of a Fusion for Energy (F4E) grant agreement, to make the IVVS probe design compatible with ITER operating conditions and in particular, but not only, with attention to neutrons and gammas fluxes and both space constraints and interfaces. The paper describes the testing activity performed on the customized piezoelectric motors and the main components of the actuating system of the IVVS probe with reference to ITER gamma radiation conditions. In particular the test is performed on the piezoelectric motor, optical encoder and small scale optical samples .The test is carried out on the ENEA Calliope gamma irradiation facility at ITER relevant gamma fields at rate of about 2.5 kGy/h and doses of 4 MGy. The paper reports in detail the setup arrangement of the test campaign in order to verify significant working capability of the IVVS actuating components and the results are shown in terms of functional performances and parameters. The overall test campaign on IVVS actuating system will be completed on other ENEA testing facilities in order to verify compatibility to Magnetic field, neutrons and thermal vacuum ITER typical environmental working conditions. © 2013 Euratom-ENEA Association sulla Fusione. Published by Elsevier B.V. All rights reserved.
1. Introduction The In Vessel Viewing System (IVVS) is a fundamental remote handling equipment, which will be used to make a survey of the status of the blanket first wall and divertor plasma facing components in ITER before first plasma and between plasma operations.
夽 Disclaimer: The views and opinions expressed herein are the sole responsibility of the authors and do not necessarily reflect those of Fusion for Energy, the European Commission or the ITER Organization. Fusion For Energy is not liable for the use which might be made of the information in this publication. ∗ Corresponding author. E-mail address: [email protected] (P. Rossi).
A design and testing activity is ongoing, in the framework of a Fusion for Energy (F4E) grant agreement, to make the IVVS probe design compatible with ITER operating conditions such as high temperature, very high magnetic field, ultra high vacuum (UHV), neutron and gamma fluxes. In particular gamma radiation dose rate will be up to 5 kGy/h and environmental radiation integrated dose will be up to 10 MGy. Furthermore, the IVVS probe must be compatible with the geometrical constraints coming from the space allocated to the system and the port to access to the vacuum vessel. The most important IVVS mechanical function is laser beam steering and control. The probe steers the laser beam through a silica fused prism attached to the mechanical axes. By rotating the axes of the prism, the probe can scan any desired area and point in any direction. The back scattered signal is then processed
0920-3796/$ – see front matter © 2013 Euratom-ENEA Association sulla Fusione. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2013.03.030
P. Rossi et al. / Fusion Engineering and Design 88 (2013) 2084–2087
2085
Fig. 2. Piezo-motor prototype.
Fig. 1. IVVS rotating head with prism, piezo-motors and optical encoders.
to measure the intensity level (viewing) and the time of flight that gives the distance from the probe (metrology). Two optical encoders accurately measure the angular orientation of the probe’s two mechanical axes. ENEA already developed and tested a prototype of a laser In Vessel Viewing and ranging System for ITER [1,2] and studied also an updated conceptual design where the tilt and the pan rotation actuators are driven by a couple of ultrasonic piezo-motors (see Fig. 1). Commercial ultrasonic piezo-motors are intrinsically nonmagnetic and vacuum-compatible but must be customized to work at 120 ◦ C, to be backed at 200 ◦ C and verified under neutrons and gamma radiations. One piezo-motor prototype has been realized for the purpose by Physik Instrumente (see Fig. 2) and has been tested to verify its compatibility to ITER gamma radiation conditions. The test was performed on the motor, optical encoder and small scale optical samples and was carried out on the ENEA Calliope gamma irradiation facility at rate of about 2.5 KGy/h up to the required total dose of 4 MGy.
water level. The irradiation cell biological protection is realized in baritic concrete with thickness up to 180 cm [3]. The maximum dose rate is achievable along the longitudinal axis of the source rack. In particular on May 2012 nine Red 4034 Perspex dosimeters have been placed in the center of the source cage and irradiated for 17 h. Afterwards the dosimeters were read and a dose rate of 2301.3 Gy/h was determined with a total uncertainty less than 5%. This dose rate value, corrected for the decay time, is used to evaluate the total dose delivered to the various IVVS components which have been hanged along the longitudinal source axis inside a containing structure (see Fig. 3). The intent was to reach a total accumulated dose of 4 MGy in about 70 days of irradiation in order to verify working capability of the IVVS actuating components and in particular of the piezo-motor in terms of functional performances and parameters. 3. Piezo-motor test assembly The PI piezo-actuator under test is a rotary stage prototype consisting of two piezo linear devices U-164 preloaded against a ceramic friction ring. They work as a break when at rest while in operation they oscillate with ultrasonic frequencies providing a rotation of the ring. The motor was controlled by the PI singleaxis C-867.160 motor controller operated by a host PC via USB port by means of a LabView application.
2. Gamma test facility Calliope is a pool-type irradiation facility equipped with a 60 Co gamma source in a high volume (7*6*3.9 m3 ) shielded bunker. The source has cylindrical geometry with 48 source pencils placed on two concentric cylinders of about 20 cm outer radius and 26 cm height. The source during no irradiation operation is stored in shielded position inside a water pool. For the irradiation operation the source is lifted-up using a crane and placed on air above the pool
Fig. 3. Piezo-motor test assembly on Calliope Facility.
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P. Rossi et al. / Fusion Engineering and Design 88 (2013) 2084–2087
The active components, i.e. the motor, were remote monitored using Kapton® insulated cables going from the irradiation zone to a shielded area, where the data acquisition hardware is placed. DAQ system (National Instruments compactDAQ) has three I/O modules to acquire temperature from RTD sensors + rheostat information (module NI 9217, analog input), to acquire optical encoder information (module NI 9215, analog input) and to acquire micro switches (module NI 9401, digital input). DAQ system is connected to a personal computer in which the data are stored. The local control room is located in the building of the Calliope facility but it is possible to remotely control the system. 3.1. Test procedure
Fig. 4. Detail of piezo-motor test assembly.
The rotary stage has been fixed on a supporting structure and has been equipped with a shaft driving a mechanical gear and a rad-hard rheostat. The Rheostat (RT12 Vishay Sfernice) works as angular position transducer, while the shaft activates two mechanical micro switches (Burgess V3F, rad-hard) placed at about 200◦ angular distance (see Fig. 4). The gear works as the rotative component of a very robust optical encoder system where teeth are optically read by a couple of optical fibers (silica/silica 600 m core) placed at a distance of 1 mm. The encoder electronic driver includes a transmission system using an adjustable laser source (up to 100 mW) coupled to the transmitting optical fiber. The receiving optical fiber is coupled to an amplified photo-detector, necessary to amplify the very low level optical signal. A gain controlled amplifier is necessary to adjust the electrical output with the Data Acquisition System input requirements On the structure were also fixed the custom optical encoder and collimator designed for ITER IVVS probe, both made from borofloat glass, to be optically compared after test to ones not irradiated. A rad-hard temperature sensor (electrotherm Type K10-E-3LS-400) monitors any increment of the motor temperature during the irradiation test.
The target of the test is to evaluate the behavior of the piezomotor prototype under gamma irradiation conditions similar to those of the IVVS scanning movements on ITER environment. The motor runs clockwise (CW) and counter clockwise CCW) directions driving the rheostat which gives a resisting torque of 0.1 N m and pressing two micro switches CW and CCW which give an additional resisting torque of 0.09 N m. Then, to move the motor and correctly press the switches it is necessary an effective motor torque of at least 0.19 N m (some additional friction is given from the internal bearing). The motor and its driver has a single dimensionless characteristic parameter “motor out” which varies both the speed and the torque and determines the amplitude of the output voltage (peakto-peak value Vpp) [4]. A specific characterization of the motor system has been performed before test and then repeated twice each working day one hour in the morning and one hour in the afternoon. In each characterization the following characteristic values have been evaluated: (a) Minimum motor-out-value to move the motor in both direction without pressing the switches; (b) Minimum motor-out-value to move the motor and to press switches; In case of degradation of the motor functions, it was possible to recover the movement increasing the value of “motor out”. The motor movement was controlled and monitored remotely from ENEA Frascati laboratories trough a LabVIEW user interface
Fig. 5. Detail of LabVIEW application interface for piezo-motor gamma irradiation test.
P. Rossi et al. / Fusion Engineering and Design 88 (2013) 2084–2087
2087
Fig. 6. Motor-out values plots during gamma irradiation test of piezo-motor in both directions.
developed to present all the relevant data: temperature, movement information of the motor by the encoder, by the micro switches and by the rheostat. A relevant part of the user interface is shown in Fig. 5. 4. Test results Since the Calliope facility is not operative during August, the gamma test campaign has been performed in two phases: the first between 6th July and 3rd August 2012 and the second phase from 4th September to 12th November 2012. In Fig. 6 is reported how the characteristic values (a, b, in the previous section) have changed during the full irradiation test of 2222 h for a total dose of about 4.88 MGy. The sign of the motor-out-value determines the direction of the motion; It has been noticed, also before the irradiation start, that the motor has more strength in negative direction than in the positive one, resulting in two different motor-out-values. Anyway the motor-out-values in both directions didn’t vary significantly from the first motor characterization, done before gamma irradiation start, with average values of 18,000 and 16,000. Considering that the motor-out maximum value is 24,000, there is also a consistent margin to operate the motor. No recovery effect due to the period of no gamma irradiation has been noticed. In fact the characteristic values collected during the first days of the second phase are similar to previous. Moreover, considering that the nominal torque of a commercial rotary stage (PI M660, similar to the tested prototype) is 0.3 N m, the motor has been operated without any evident loss of performances at about 70% of its mechanical capability, which approximately corresponds to the ratio between the used motor-out value and the maximum one. The monitored temperature remained quite constant around 30.5 ± 1.5 ◦ C. The small variation is due to laboratory environmental conditions and seems not to be linked to any irradiation effect, given the low energy deposited by the gammas (2500 Gy/h correspond to 0.7 W/kg).
5. Comments The gamma irradiation test of the IVVS actuating components reached a total dose of 4.88 MGy, higher than the target of 4 MGy, without any evident and significant damages and degradation of the piezo-motor functionality. The piezo-ceramic rotation stage prototype has been able to provide enough torque to both ensure the movement and the closure of the switches during the whole test campaign completing about 90 characterization cycles of 1 hour each at about 70% of its torque capability and maintaining almost the same working parameters monitored before test. After the gamma irradiation test, the same piezo-motor assembly will be tested with 14 MeV neutrons irradiation using ENEA FNG facility [5]. The overall test campaign on IVVS actuating system will be completed on other ENEA testing facilities in order to verify also compatibility to magnetic field and thermal vacuum ITER typical environmental working conditions. Acknowledgments The authors wish to thank the Calliope operators A. Pasquali and G. Ferrara for their precious assistance during the experimental session. This work has been supported by Fusion for Energy under the grant agreement F4E-GRT-282. References [1] C. Neri, P. Costa, M. Ferri De Collibus, M. Florean, G. Mugnaini, M. Pillon, F. Pollastrone, P. Rossi, Iter in vessel viewing system design and assessment activities, Fusion Engineering and Design 86 (2011) 1954–1957. [2] C. Neri, L. Bartolini, B. Brichard, A. Coletti, M. Ferri de Collibus, G. Fornetti, et al., The laser in vessel viewing system IVVS for ITER: test results on first wall and divertor samples and new developments, Fusion Engineering and Design 82 (2007) 2021–2028. [3] S. Baccaro, A. Cecilia, A. Pasquali, ␥ irradiation facility at ENEA-Casaccia Centre (Rome), ENEA RT/2005/28/FIS, ISSN/0393-3016, 2005. [4] MS185E User Manual, C-867 PILine® Controller, Release: 1.1.0 Date: 07.12.2009. [5] M. Martone, M. Angelone, M. Pillon, The 14 MeV Frascati neutron generator, Journal of Nuclear Materials 63 (1993) 1661–1663.