*2.3.2.4 Sample holder dedicated to the irradiation under magnetic field (STD line of CMAM)*

In order to investigate the influence of an external magnetic field on ioninduced damage, a new experimental system has been developed at the STD line of CMAM. It consists on a dedicated custom sample holder with a permanent magnet embedded behind one of the samples (see **Figure 7a**). Here the samples are irradiated in pairs with and without external magnetic field (B = 0.4 T) with field lines oriented normal to the sample surface in order to avoid ion beam spreading. Commissioning of the system was performed by the irradiation of a luminescent material deposited on a metal support plate. In this way, it was observed that the ions impacting on the luminescent material showed good magnetic field uniformity. In addition, the complete system, i.e., the holder, the permanent magnet, and a UHP-Fe test sample, was also tested during 4 h of irradiation by a 2 MeV, 200 nA

**Figure 6.** *Microtensile test module mounted in the vacuum chamber base (a) and detail of the test section with a probe (b).*

**27**

(Fe+

**Figure 7.**

*Ion Beam Experiments to Emulate Nuclear Fusion Environment on Structural Materials…*

current H+ beam at a sample temperature of −100°C, with and without magnetic field, getting a good temperature control during irradiation and a same ion beam footprint in sample without B and with B. Although irradiations can generally be

*(a) New sample holder for the irradiation of samples in pairs. It has a permanent magnet behind the right sample. The setup is connected to a LN cooled finger (by a Cu mesh) to achieve low temperature if required. A thermocouple is touching one of the samples for temperature measurements; (b) ANSYS simulation of the* 

In parallel, prior to starting the experiments, ANSYS simulations were done for Fe90Cr10 slice (1 mm thick) embedded in the center of a long solenoid (giving 1 T in the central column) in order to emulate the effect of B on the surface of the sample. **Figure 7b** shows that although a high concentration of magnetic field lines is observed at the edge, there is good magnetic flux uniformity about the irradiated zone (sample central region), thus validating the experimental setup for use with these samples.

A series of experiments have carried out with this sample holder to study the damage in FeCr alloy (14% Cr content) when irradiated at low temperature by heavy

of an external magnetic field (B = 0.4 T) was also analyzed [31]. In this context, the influence of B on defects shows small but significant differences in the magnitudes studied here by conversion electron Mössbauer spectroscopy (CEMS) and slow positron annihilation spectroscopy (SPAS). Mössbauer spectra point to less clustering for a sample damaged by He+ (being closer to the as-received sample) than irradiation without B. SPAS points to slightly lower values of vacancy-type defects over a

further support the conclusion that the size or concentration of the vacancy clusters

was analyzed by CEMS and found differences when the magnetic field is present during irradiation [18]. The results indicate that the Cr distribution in the neighborhood of the iron atoms could be changed by the application of an external field. The detailed studies carried out up to date [18, 31] indicate that an external magnetic field may be an important parameter to take into account in predictive models for Cr behavior in FeCr alloys and especially in fusion conditions where

created during the Fe + ion irradiation diminishes in the presence of B.

) ions, single and sequentially, and additionally, the influence

(again compared to irradiation without B). SPAS results

, high dose) or by sequential

up to 15 dpa (displacement per atom)

performed at low temperature, the analysis is always carried out at RT.

**3.1 First results of FeCr alloy damage by ions under magnetic field**

large region when a sample is damaged by self-ions (Fe+

Also, FeCr alloy (10% Cr) damaged by Fe<sup>+</sup>

and He+

*DOI: http://dx.doi.org/10.5772/intechopen.87054*

*magnetic field in the sample near the permanent magnet.*

**3. Experimental results**

) and light (He+

irradiation: Fe+

*Ion Beam Experiments to Emulate Nuclear Fusion Environment on Structural Materials… DOI: http://dx.doi.org/10.5772/intechopen.87054*

**Figure 7.**

*Ion Beam Techniques and Applications*

*of CMAM)*

of innovative techniques for material research. In this case we have installed a microtensile test module (**Figure 6**) inside the vacuum chamber in order to carry out mechanical strain/stress tests of materials under irradiation or irradiate structural materials (Fe, Cu, steel), while the sample is submitted to a constant stress. The chamber base shown above and holding the XYZ sample holder can be easily changed by a new one with the microtensile module installed and connected with the proper Fischer feedthrough. Especial connectors are also incorporated for temperature measurements (thermocouple and oven) during the tests.

*2.3.2.4 Sample holder dedicated to the irradiation under magnetic field (STD line* 

In order to investigate the influence of an external magnetic field on ioninduced damage, a new experimental system has been developed at the STD line of CMAM. It consists on a dedicated custom sample holder with a permanent magnet embedded behind one of the samples (see **Figure 7a**). Here the samples are irradiated in pairs with and without external magnetic field (B = 0.4 T) with field lines oriented normal to the sample surface in order to avoid ion beam spreading. Commissioning of the system was performed by the irradiation of a luminescent material deposited on a metal support plate. In this way, it was observed that the ions impacting on the luminescent material showed good magnetic field uniformity. In addition, the complete system, i.e., the holder, the permanent magnet, and a UHP-Fe test sample, was also tested during 4 h of irradiation by a 2 MeV, 200 nA

*Microtensile test module mounted in the vacuum chamber base (a) and detail of the test section with a probe (b).*

**26**

**Figure 6.**

*(a) New sample holder for the irradiation of samples in pairs. It has a permanent magnet behind the right sample. The setup is connected to a LN cooled finger (by a Cu mesh) to achieve low temperature if required. A thermocouple is touching one of the samples for temperature measurements; (b) ANSYS simulation of the magnetic field in the sample near the permanent magnet.*

current H+ beam at a sample temperature of −100°C, with and without magnetic field, getting a good temperature control during irradiation and a same ion beam footprint in sample without B and with B. Although irradiations can generally be performed at low temperature, the analysis is always carried out at RT.

In parallel, prior to starting the experiments, ANSYS simulations were done for Fe90Cr10 slice (1 mm thick) embedded in the center of a long solenoid (giving 1 T in the central column) in order to emulate the effect of B on the surface of the sample. **Figure 7b** shows that although a high concentration of magnetic field lines is observed at the edge, there is good magnetic flux uniformity about the irradiated zone (sample central region), thus validating the experimental setup for use with these samples.

## **3. Experimental results**

### **3.1 First results of FeCr alloy damage by ions under magnetic field**

A series of experiments have carried out with this sample holder to study the damage in FeCr alloy (14% Cr content) when irradiated at low temperature by heavy (Fe+ ) and light (He+ ) ions, single and sequentially, and additionally, the influence of an external magnetic field (B = 0.4 T) was also analyzed [31]. In this context, the influence of B on defects shows small but significant differences in the magnitudes studied here by conversion electron Mössbauer spectroscopy (CEMS) and slow positron annihilation spectroscopy (SPAS). Mössbauer spectra point to less clustering for a sample damaged by He+ (being closer to the as-received sample) than irradiation without B. SPAS points to slightly lower values of vacancy-type defects over a large region when a sample is damaged by self-ions (Fe+ , high dose) or by sequential irradiation: Fe+ and He+ (again compared to irradiation without B). SPAS results further support the conclusion that the size or concentration of the vacancy clusters created during the Fe + ion irradiation diminishes in the presence of B.

Also, FeCr alloy (10% Cr) damaged by Fe<sup>+</sup> up to 15 dpa (displacement per atom) was analyzed by CEMS and found differences when the magnetic field is present during irradiation [18]. The results indicate that the Cr distribution in the neighborhood of the iron atoms could be changed by the application of an external field.

The detailed studies carried out up to date [18, 31] indicate that an external magnetic field may be an important parameter to take into account in predictive models for Cr behavior in FeCr alloys and especially in fusion conditions where

### *Ion Beam Techniques and Applications*

intense magnetic fields are required for plasma confinement. Experiments with higher B and higher sample temperature are currently in progress in order to elucidate if external magnetic fields are a key parameter in the structural materials damage.
