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Amorphous Fe targets for transient field measurements with heavy-ion beams
Nuclear Instruments and Methods in Physics Research A 397 (1997) 52-54
a3.. __ ‘5% lfild ELSEVIER
Amorphous
NUCLEAR INSTRUMENTS i%METHODS IN PHYSICS RESEARCH SectIonA
Fe targets for transient field measurements with heavy-ion beams
L. Kleinena, K.-H. Speidel”,“, H. Buscha, R. Err&, A. Gohla”, U. Grabowya, G. Jakobb, V. Roth”, J. Gerberc, A. M6ensc, P. Maier-Komorb, P. Scharwaechterd aInstitutjiir
Strahlen- und Kernphysik, Univ. Bonn, Nussallee 14-16, D-53115 Bonn, Germany bPhysik-Dept., Technische Univ. Miinchen, D-85748 Garching, Germany ’ Cenfre de Recherches Nu&aires. F-67037 Strasbourg, France d Inst. f: Theor. und Angew. Physik, Univ. Stuttgart, D-70550 Stuttgart, Germany
Abstract For transient field measurements (TF), ferromagnetic target foils of the amorphous Fe89 B79 compound were prepared with thicknesses between 2 and 8 urn. A minimum thickness of 8 urn was achieved employing a special lapping and polishing technique. For further thickness reduction, the ion-etching technique was used. Very promising results with respect to heavy-ion beam deterioration of TF were obtained in the preliminary measurements with this material.
1. Introduction It was shown [l] that the deteriorating effect of heavyion beams on transient magnetic fields (TF) can be eliminated by segmentation of the ferromagnetic layer of bombarded targets (see contributed paper by Busch et al. [2]). This is a consequence of the long-range propagation [3] of the induced demagnetization which is restricted by the segment size. The same effect can be expected with amorphous Fe targets where the structure is of short-range order in contrast to crystalline Fe. For TF measurements, specific requirements have to be fulfilled using amorphous materials, which are described below.
2. Manufacture and properties of FesoBzo The amorphous compounds used in our experiments were produced by the melt-spinning technique, which is a well established method to obtain glassy metals [4]. FegOBZo in its crystalline form (containing 80 at% Fe and 20 at% B) is melted by using a high-frequency conductance coil in a quartz nozzle. Ar gas of high-pressure ejects the melted material on to a rapidly spinning copper wheel. High cooling rates of lo6 K/s caused by the good
* Corresponding
author.
heat conductivity of the copper wheel inhibit the crystallization leading to the amorphous state. This is characterized by anisotropy and the lack of long-range order as shown in X-ray and neutron diffraction measurements. It is this feature which may be the cause, that, the ionbeam-induced demagnetization is of short-range order as well.
3. Sample preparation - Foils of amorphous FesoBzo should have thicknesses between 2 and 8 urn depending on the specific experiment and ion beam. - Foils of the dimension of 1 cm wide and 21 urn thick ribbons were provided by the Max Planck Institut of Metallurgy in Stuttgart (Germany). ~ As the material is extremely susceptible to oxidation, it has to be cleaned with alcohol or acetone after each working step and should be kept in an evacuated desiccator. - The ribbon is fixed to a glass plate via a double-sided adhesive PVC-foil and is covered with several PVC masks. The masked pieces are separated from the ribbon by dissolving the unmasked Fe,,,B2,, parts in nitrohydrochloric acid. - The acid is rinsed out with water; the PVC masks and FesoBlo samples are carefully removed from the glass and adhesive remains dissolved in an ultrasonic bath with acetone. The circular shaped wafers are dried immediately.
0168-9002/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rights reserved PII
SO168-9002(97)00376-S
L. Kleinen et al. INucl. Ins@. and Meth. in Phys. Rex A 397 (1997) 52-54
To achieve a homogeneous reduction of the sample thickness a special lap technique is applied. The Fes,B,,, wafers are glued with glycerol-phthalic resin at 403 K on top of small steel cylinders (Fig. 1, left). These are heated on a hot plate with a tiny piece of synthetic resin glue melted on top of it. The wafers are attached to their carriers by pressing them on the resin glue with the help of a microscope slide (Fig. 1, right). To obtain a uniform thin film of glue between wafer and carrier, the overflowing glue is pressed from underneath the wafer by a slow rotation of the slide. The resin film should not vary more than 3 urn in its thickness. The carriers - 12 at maximum - are screwed to a heavy polishing block which is put upside down onto a thick glass plate covered with an A1,03-suspension (1 pm) (Fig. 2(a)). The glass plate is then inserted into a lapping (L) and polishing (P) machine, of the type L/P machine, model 7, manufactured by Solid State Measurements (Fig. 2(b)). The samples are lapped for approximately 90min causing an abrasion of FeBoBzo between the rotating glass plate and the polishing block through contact with the A1203 particles. For every 10 - 15 min one has to ensure that the suspension is still in fluid to avoid a loss of the samples. Water is eventually added. One can expect a thickness reduction of N 0.1 um/min depending on the velocity of the L/P-machine. After lapping, the wafers are polished by impasting an Al,O,-suspension (0.3 urn) on a cloth-covered glass plate and repeating the lap procedure for about 10 min. The Al,O,-suspension is then rinsed off the polishing block with water and the wafers are removed from their carriers by an ultrasonic cleaning in acetone. Finally, the free samples are carefully cleaned with acetone and dried with cotton buds. There is a high probability to lose wafers in each working step. Stresses in the amorphous material become more important with decreasing thickness of the FesoBzo wafers and cause them to come off their carriers. Lapping and polishing procedure are of no further advantage to relax the FegoBzo by annealing the ribbon
s1ide// FeB-wafer
ti
*
__
resin glue steel-cylin
I Fig. 1. Schematic their carriers
view of mounting
lcm
the amorphous
I wafers
on
53
FeB-wafer carrier
polishing
block
1 cm
Fig. 2. (a)Polishing block with several mounted wafers (see text); (b) Scheme of the lapping and polishing machine.
for 5 h at 593 K, although
in the following process of ion etching, this technique facilitates the handling of the samples. Those smaples, which sustain this delicate treatment, have shiny smooth surfaces and thicknesses between 7 and 12 urn. For further reduction of the thickness, ion etching is applied (see also Ref. [2]). For this purpose the FeaOBZO foils are bombarded with Ar ions (Fig. 3) which are produced in an ion source by electron impact with the gas atoms. The Ar gas is injected into an evacuated chamber maintaining a pressure of 2 x 10M2 Pa. The ions are guided towards the sample by two accelerator grids. The etching amounts depend on the ion current and the duration of bombardment. For FegOBZO etching rates of 0.33 mg/cm” per hour were achieved with current densities of 0.4 mA/cm* and ion energies between 800 eV and 1.0 keV. With such samples TF measurements have been performed using 48Ti-and 56Fe-beams of 130 and 150 MeV, respectively. The TF strengths observed for high-velocity 24Mg(2+)ions are significantly less attenuated than for crystalline Fe layers [S]. This result confirms the expectation that the beam induced demagnetization is more localized in the amorphous material due to its short-range order.
III. SPECIAL
TARGETS
L. Kleinen et al. /Nucl. Instr. and Meth. in Phys. Rex A 397 (1997) 52-54
54
source filament
Acknowledgements
gas inlet plasma chamber permanent magnet
One of us (L.K.) is indebted to the MPI in Stuttgart for kind hospitality and assistance during the sample preparation. The authors acknowledge the support by the BMBF and the Deutsche Forschungsgemeinschaft.
accelerator grids ion beam
References
neutralizer filament
\ ”v
removable cup
diffusion pump Fig. 3. Scheme of the ion-etching apparatus,
Cl1 H. Busch, G. Jakob, K.-H. Speidel, J. Cub, S. Kremeyer,
U. Grabowy, A. Gohla, J. Gerber, A. Meens, P. MaierKomor, C. Rezny, M. Schulz, P. Padberg, Z. Phys. A 355 (1996) 9. 121 H. Busch et al., these proceedings (18th World Conf. of the INTDS, Strasbourg, France, 1996) Nucl. Instr. and Meth. A 397 (1997) 10.5. c31 K.-H. Speidel, G. Jakob, H. Busch, U. Grabowy, J. Cub, A. Gohla, S. Kremeyer, C. Rezny, M. Behr, J. Gerber, P. Maier-Komor, Nucl. Instr and Meth. I3 107 (1996) 133. [41 H. Beck, H.-J. Giintherodt, in: H.-J. Guntherodt, H. Beck (Eds.), Glassy Metals I, Springer, Berlin, 1981, p. 1. c51 K.-H. Speidel, L. Kleinen, A. Gohla, R. Ernst, H. Busch, G. Jakob, U. Grabowy, V. Roth, J. Gerber, Z. Phys. A, in press.
a3.. __ ‘5% lfild ELSEVIER
Amorphous
NUCLEAR INSTRUMENTS i%METHODS IN PHYSICS RESEARCH SectIonA
Fe targets for transient field measurements with heavy-ion beams
L. Kleinena, K.-H. Speidel”,“, H. Buscha, R. Err&, A. Gohla”, U. Grabowya, G. Jakobb, V. Roth”, J. Gerberc, A. M6ensc, P. Maier-Komorb, P. Scharwaechterd aInstitutjiir
Strahlen- und Kernphysik, Univ. Bonn, Nussallee 14-16, D-53115 Bonn, Germany bPhysik-Dept., Technische Univ. Miinchen, D-85748 Garching, Germany ’ Cenfre de Recherches Nu&aires. F-67037 Strasbourg, France d Inst. f: Theor. und Angew. Physik, Univ. Stuttgart, D-70550 Stuttgart, Germany
Abstract For transient field measurements (TF), ferromagnetic target foils of the amorphous Fe89 B79 compound were prepared with thicknesses between 2 and 8 urn. A minimum thickness of 8 urn was achieved employing a special lapping and polishing technique. For further thickness reduction, the ion-etching technique was used. Very promising results with respect to heavy-ion beam deterioration of TF were obtained in the preliminary measurements with this material.
1. Introduction It was shown [l] that the deteriorating effect of heavyion beams on transient magnetic fields (TF) can be eliminated by segmentation of the ferromagnetic layer of bombarded targets (see contributed paper by Busch et al. [2]). This is a consequence of the long-range propagation [3] of the induced demagnetization which is restricted by the segment size. The same effect can be expected with amorphous Fe targets where the structure is of short-range order in contrast to crystalline Fe. For TF measurements, specific requirements have to be fulfilled using amorphous materials, which are described below.
2. Manufacture and properties of FesoBzo The amorphous compounds used in our experiments were produced by the melt-spinning technique, which is a well established method to obtain glassy metals [4]. FegOBZo in its crystalline form (containing 80 at% Fe and 20 at% B) is melted by using a high-frequency conductance coil in a quartz nozzle. Ar gas of high-pressure ejects the melted material on to a rapidly spinning copper wheel. High cooling rates of lo6 K/s caused by the good
* Corresponding
author.
heat conductivity of the copper wheel inhibit the crystallization leading to the amorphous state. This is characterized by anisotropy and the lack of long-range order as shown in X-ray and neutron diffraction measurements. It is this feature which may be the cause, that, the ionbeam-induced demagnetization is of short-range order as well.
3. Sample preparation - Foils of amorphous FesoBzo should have thicknesses between 2 and 8 urn depending on the specific experiment and ion beam. - Foils of the dimension of 1 cm wide and 21 urn thick ribbons were provided by the Max Planck Institut of Metallurgy in Stuttgart (Germany). ~ As the material is extremely susceptible to oxidation, it has to be cleaned with alcohol or acetone after each working step and should be kept in an evacuated desiccator. - The ribbon is fixed to a glass plate via a double-sided adhesive PVC-foil and is covered with several PVC masks. The masked pieces are separated from the ribbon by dissolving the unmasked Fe,,,B2,, parts in nitrohydrochloric acid. - The acid is rinsed out with water; the PVC masks and FesoBlo samples are carefully removed from the glass and adhesive remains dissolved in an ultrasonic bath with acetone. The circular shaped wafers are dried immediately.
0168-9002/97/$17.00 Copyright 0 1997 Elsevier Science B.V. All rights reserved PII
SO168-9002(97)00376-S
L. Kleinen et al. INucl. Ins@. and Meth. in Phys. Rex A 397 (1997) 52-54
To achieve a homogeneous reduction of the sample thickness a special lap technique is applied. The Fes,B,,, wafers are glued with glycerol-phthalic resin at 403 K on top of small steel cylinders (Fig. 1, left). These are heated on a hot plate with a tiny piece of synthetic resin glue melted on top of it. The wafers are attached to their carriers by pressing them on the resin glue with the help of a microscope slide (Fig. 1, right). To obtain a uniform thin film of glue between wafer and carrier, the overflowing glue is pressed from underneath the wafer by a slow rotation of the slide. The resin film should not vary more than 3 urn in its thickness. The carriers - 12 at maximum - are screwed to a heavy polishing block which is put upside down onto a thick glass plate covered with an A1,03-suspension (1 pm) (Fig. 2(a)). The glass plate is then inserted into a lapping (L) and polishing (P) machine, of the type L/P machine, model 7, manufactured by Solid State Measurements (Fig. 2(b)). The samples are lapped for approximately 90min causing an abrasion of FeBoBzo between the rotating glass plate and the polishing block through contact with the A1203 particles. For every 10 - 15 min one has to ensure that the suspension is still in fluid to avoid a loss of the samples. Water is eventually added. One can expect a thickness reduction of N 0.1 um/min depending on the velocity of the L/P-machine. After lapping, the wafers are polished by impasting an Al,O,-suspension (0.3 urn) on a cloth-covered glass plate and repeating the lap procedure for about 10 min. The Al,O,-suspension is then rinsed off the polishing block with water and the wafers are removed from their carriers by an ultrasonic cleaning in acetone. Finally, the free samples are carefully cleaned with acetone and dried with cotton buds. There is a high probability to lose wafers in each working step. Stresses in the amorphous material become more important with decreasing thickness of the FesoBzo wafers and cause them to come off their carriers. Lapping and polishing procedure are of no further advantage to relax the FegoBzo by annealing the ribbon
s1ide// FeB-wafer
ti
*
__
resin glue steel-cylin
I Fig. 1. Schematic their carriers
view of mounting
lcm
the amorphous
I wafers
on
53
FeB-wafer carrier
polishing
block
1 cm
Fig. 2. (a)Polishing block with several mounted wafers (see text); (b) Scheme of the lapping and polishing machine.
for 5 h at 593 K, although
in the following process of ion etching, this technique facilitates the handling of the samples. Those smaples, which sustain this delicate treatment, have shiny smooth surfaces and thicknesses between 7 and 12 urn. For further reduction of the thickness, ion etching is applied (see also Ref. [2]). For this purpose the FeaOBZO foils are bombarded with Ar ions (Fig. 3) which are produced in an ion source by electron impact with the gas atoms. The Ar gas is injected into an evacuated chamber maintaining a pressure of 2 x 10M2 Pa. The ions are guided towards the sample by two accelerator grids. The etching amounts depend on the ion current and the duration of bombardment. For FegOBZO etching rates of 0.33 mg/cm” per hour were achieved with current densities of 0.4 mA/cm* and ion energies between 800 eV and 1.0 keV. With such samples TF measurements have been performed using 48Ti-and 56Fe-beams of 130 and 150 MeV, respectively. The TF strengths observed for high-velocity 24Mg(2+)ions are significantly less attenuated than for crystalline Fe layers [S]. This result confirms the expectation that the beam induced demagnetization is more localized in the amorphous material due to its short-range order.
III. SPECIAL
TARGETS
L. Kleinen et al. /Nucl. Instr. and Meth. in Phys. Rex A 397 (1997) 52-54
54
source filament
Acknowledgements
gas inlet plasma chamber permanent magnet
One of us (L.K.) is indebted to the MPI in Stuttgart for kind hospitality and assistance during the sample preparation. The authors acknowledge the support by the BMBF and the Deutsche Forschungsgemeinschaft.
accelerator grids ion beam
References
neutralizer filament
\ ”v
removable cup
diffusion pump Fig. 3. Scheme of the ion-etching apparatus,
Cl1 H. Busch, G. Jakob, K.-H. Speidel, J. Cub, S. Kremeyer,
U. Grabowy, A. Gohla, J. Gerber, A. Meens, P. MaierKomor, C. Rezny, M. Schulz, P. Padberg, Z. Phys. A 355 (1996) 9. 121 H. Busch et al., these proceedings (18th World Conf. of the INTDS, Strasbourg, France, 1996) Nucl. Instr. and Meth. A 397 (1997) 10.5. c31 K.-H. Speidel, G. Jakob, H. Busch, U. Grabowy, J. Cub, A. Gohla, S. Kremeyer, C. Rezny, M. Behr, J. Gerber, P. Maier-Komor, Nucl. Instr and Meth. I3 107 (1996) 133. [41 H. Beck, H.-J. Giintherodt, in: H.-J. Guntherodt, H. Beck (Eds.), Glassy Metals I, Springer, Berlin, 1981, p. 1. c51 K.-H. Speidel, L. Kleinen, A. Gohla, R. Ernst, H. Busch, G. Jakob, U. Grabowy, V. Roth, J. Gerber, Z. Phys. A, in press.