- Email: [email protected]
The target manufacturing laboratory at the IPNO
ARTICLE IN PRESS Nuclear Instruments and Methods in Physics Research A 613 (2010) 419–422
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
The target manufacturing laboratory at the IPNO V. Petitbon-The´venet Nuclear Physics Institute of Orsay, Target Manufacturing Laboratory, Building 109, 91406 Orsay Cedex, France
a r t i c l e in fo
abstract
Available online 7 October 2009
The target-manufacturing laboratory at the IPNO develops and produces thin layers on backings and thin self-supporting layers. The different available techniques are the evaporation in vacuum and chemical methods for the production of polymers. New techniques are going to be developed. An extension of this laboratory will be the production of radioactive layers by electrodeposition. & 2009 Elsevier B.V. All rights reserved.
Keywords: Electrodeposition Evaporation Multi-layer target Polystyrene radioactive target Self-supporting target
1. Introduction This laboratory exists since 1963, first for local accelerators only, then for the national community and the international community for accelerators, as well as for lasers. The targetmanufacturing laboratory is a service provider of layers. This laboratory manufactures various types of layers. First, thin layers on a backing represent 25% of the production. Fig. 1 shows an example of C stripper for CEA/DAM (Bruye res le Chˆatel, France) which consists of 10 mg/cm2 carbon deposited on 7 mg/cm2 polystyrene. Secondly, thin self supporting layers below 1–2 mm are produced. This represents about 60% of the production. To make self-supporting layers, we use a very clean piece of glass. We deposit a release agent (CsI, KI, adeniney) on the glass and then we deposit the wanted material on the release agent. The system is slowly immersed in water, the release agent dissolves and the material floats on the surface. Then, we fetch the selfsupporting layer on the frame. For materials which oxidise easily, a polymer as release agent is applied and we work in a glove box under controlled atmosphere. An example of a self-supporting layer of 48Ca designed for the GANIL is shown in Fig. 2. We are constantly improving our technique. For example, when there is too much release agent on the glass, the thin layer rolls up in the water and when there is not enough release agent, the thin layer does not part from the glass. We try to find release agents which are not made under vacuum, prepared in advance to save time, and whose thickness is not critical for the layer. We fabricate prototypes. For example, we evaporate thermocouples (alumel, chromel) on particular supports, following an industrial design.
Tel.: + 33 1 69 15 62 75; fax: + 33 1 69 15 51 08.
E-mail address: [email protected] 0168-9002/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2009.09.090
Up to now, we can cover up to 900 cm2 with the electron gun. For example Al is evaporated with a precision of 2% for a 200 nm thickness over this area.
2. The resources Except for the production of polymer layers all techniques are applied under vacuum. The deposition rate and the thickness are measured during the deposition with quartz crystal monitor. (2.1) The laboratory is equipped with three evaporation systems with electron-beam guns. Electron-beam evaporation is the most common technique in the laboratory. Two set-ups are equipped with diffusion pumps (10 7 mbar) which typically allow one experiment per day and the third set-up is equipped with a cryogenic pump (10 10 mbar) which allows two or three experiments per day because of the much faster pumping speed. In Fig. 3a photo of an electron-beam gun is shown. In an electron-beam gun, a tungsten filament is connected to a low voltage power supply to cause an emission of electrons. A strong electric field is generated near the filament to accelerate the electrons which are then curved by a magnetic field. The crucible is water-cooled to avoid an alloy between the material and the crucible. We can use materials with a high melting point up to 3800 1C. (2.2) The laboratory is equipped with an electric arc for C deposition, as shown in Fig. 4. The electric arc runs under vacuum (10 6 mbar) and vaporises material off the graphite electrodes. An important heating occurs in the contact point what requires to make the sublimation of the carbon several times. (2.3) In addition, an electron bombardment is available, as can be seen in Fig. 5. The crucible is a tube which is situated close to the support of the target frame. Electron bombardment is particularly applied for targets out of isotopically enriched
ARTICLE IN PRESS 420
V. Petitbon-The´venet / Nuclear Instruments and Methods in Physics Research A 613 (2010) 419–422
material with a diameter o15 mm and for thin layers (2mm). The process is very material efficient because of the small crucible and the short distance between material and substrate. The thickness has a precision of 5%. This process is applied for expensive and rare isotopes. For example, 1 mg of 48 Ca with an isotopic purity of 99% costs about 400h. For materials sensitive to oxygen, we evaporate the material on a polymer foil on the frame and we use a transfer rod as shown in Fig. 6 to work in a glove box under controlled atmosphere. We stick the layer with a solvent like ethylacetate which dissolves the polymer. (2.4) The laboratory is equipped with a glove under controlled atmosphere. A pumping system brings the pressure down to about 10 2 mbar and a circulation of argon can then be established. In this case, a hygrometry level has to be maintained to 0% (Fig. 7). (2.5) Thermal evaporation: In Fig. 8, a thermal evaporation set-up is shown; the release agent is evaporated from one crucible, the target material from a second. The applied crucible depends on the material. For the evaporation of Au or CsI, we apply a boat out of Ta, W or Mo with or without alumina as shown in Fig. 9. The ‘‘basket heater’’ shown in Fig. 10 is a system used to evaporate with an indirect heating. For Al which boils over easily, we add a W wire to the Al. When the Al melts, it wets the wire and stays in the crucible. The boiling is minimized. The risk of overflowing and short circuit is eliminated. In Fig. 11, the baffled box is shown which is applied to control the evaporation of easily bursting materials like SiO. These different crucibles are connected to the electrodes of a controlled power supply.
(2.6) One polymer hood for the manufacturing of polymer layers is available. The support is dipped into a chemical solution (a mixture between the solvent and the polymer powder). Experimentally, the ratio between the weight of the polymer and the quantity of solvent has to be obtained for the
Fig. 3. Electron gun. 1: Water-cooled crucible, turning crucible with four positions in order to make multilayer. 2: Opening for the electron emission. 3: Shutter.
Fig. 1. Carbon stripper for CEA/DAM Bruye res le Chˆatel, France.
Fig. 2. Self-supporting layer of
Fig. 4. Electric arc for carbon deposition.
48
Ca for the GANIL.
ARTICLE IN PRESS V. Petitbon-The´venet / Nuclear Instruments and Methods in Physics Research A 613 (2010) 419–422
Fig. 5. Electron bombardment.
421
Fig. 8. Thermal set-up.
Fig. 9. Alumina coated evaporation source—R.D Mathis company.
wanted thickness of the polystyrene layer. In order to prepare radioactive layers, we are working on polyimide films, a polymer which can stand temperatures up to 450 1C [1].
Fig. 6. Transfer rod.
3. A recent list of manufacturing The table below shows a list of recent layers made at Orsay. Self supporting Surface deposits
Multilayers
Zr, Al, Au, Cu, Ti, In, Sn, Co, Ca, 48Ca, C, Ta, Ag, Mg, Sc, Si, CD2, CH, 7Li, Niy Au, 11B, C, Al, Pb, Bi, W, CsI, phenylalanine, Sm, 60C, Alumel (Ni90%, Cr10%), Chromel (Ni95%, Al2%, Mn3%, Si1%) Al/C/Al, CH/C, CH/AL, CH/KBr/Si/Al/Si
Target demands out of isotopically enriched materials are typically developed for the natural material first and then the production process is adapted for the enriched material. The behaviour of the natural material is generally identical to the isotopically material in 98% of the cases. The exception known in the targets laboratory is 154Sm.
4. The characterisation
Fig. 7. Glove box under controlled argon atmosphere.
Important quality information for the experimenters is typically the thickness and the chemical purity.
ARTICLE IN PRESS V. Petitbon-The´venet / Nuclear Instruments and Methods in Physics Research A 613 (2010) 419–422
422
Fig. 10. Basket heater with crucible—R.D Mathis company.
http://ipnweb.in2p3.fr/ cibles/, activities of the laboratory are listed in detail. This site, both in French and in English, is commonly used by different companies and research groups to establish contacts with us. Moreover, some presentation brochures are available on enquiry.
6. Future of the lab
Fig. 11. Silicon monoxide source—R.D Mathis company.
In the target manufacturing, we can measure the thickness. Up to now, we have no method to control the purity so we take a lot of precautions to be rigours: we clean regularly, we use systematically gloves, and we protect the different parts which are not easily accessible with aluminium foils to protect them from the pollution. At the CSNSM (Centre de Spectroscopie Nucle´aire et de Spectrome´trie de Masse), a laboratory near the IPNO, we can use RBS method. We have three techniques to measure the thicknesses:
by loss of alpha energy, by mechanical profilometer 2D/3D, where the difference of
height is measured, by the use of a precision balance.
For the laser community additionally the needed foils have to be light tight. We apply a He/Ne laser to control the produced foils. We can visualize holes. The size of holes is unknown. The control is ‘‘all or none’’. If we do not see the laser light in the other side of the layer, it is okay. If we see light in the other side of the layer, we start the manufacture again.
5. Communication Even if the laboratory is mainly dedicated to IPNO’s needs, many requests come from other laboratories. On the web site,
We have started a programme to develop the manufacturing of radioactive layers by electrodeposition [2,3]. Collaborations are under construction with different partners, in order to acquire the necessary knowledge and to be able to arrange necessary means for the characterization of targets. In a first step, we develop collaborations with the radiochemistry group of Orsay, the European IRMM/Geel Institute, the Berkeley University and the Wadworth Institute, the CEA/DAM and the Laboratoire National Henri Becquerel, a national metrology laboratory. This implies to work closely with the safety and security people. In 2009, a specific building should become operational. Development of new techniques: We would like to develop the centrifugation technique to make isotopic layers with backing without losing material. Spin coating is going to be developed, in order to make more homogeneous polymer targets. A recent study showed that the homogeneity of our polymers is bad. There are differences between two points more than + 100%. This means that we will have to re-establish the charts.
7. Conclusion The target manufacturing laboratory tries to answer all the demands so the physicists can obtain interesting results during and after their experiments.
Acknowledgements I would like to thank Patrick Nicol, Patrice Renevret and Julien Mottier who work with me. References ¨ [1] D.C. Aumann, G. Mullen, Nucl. Instr. and Meth. 115 (1974) 75. [2] A. Stolarz, J.V. Gestel, Nucl. Instr. and Meth. 561 (2006) 115. [3] Ch.O. Bacri, Paper on CACAO project, Contribution to this conference.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
The target manufacturing laboratory at the IPNO V. Petitbon-The´venet Nuclear Physics Institute of Orsay, Target Manufacturing Laboratory, Building 109, 91406 Orsay Cedex, France
a r t i c l e in fo
abstract
Available online 7 October 2009
The target-manufacturing laboratory at the IPNO develops and produces thin layers on backings and thin self-supporting layers. The different available techniques are the evaporation in vacuum and chemical methods for the production of polymers. New techniques are going to be developed. An extension of this laboratory will be the production of radioactive layers by electrodeposition. & 2009 Elsevier B.V. All rights reserved.
Keywords: Electrodeposition Evaporation Multi-layer target Polystyrene radioactive target Self-supporting target
1. Introduction This laboratory exists since 1963, first for local accelerators only, then for the national community and the international community for accelerators, as well as for lasers. The targetmanufacturing laboratory is a service provider of layers. This laboratory manufactures various types of layers. First, thin layers on a backing represent 25% of the production. Fig. 1 shows an example of C stripper for CEA/DAM (Bruye res le Chˆatel, France) which consists of 10 mg/cm2 carbon deposited on 7 mg/cm2 polystyrene. Secondly, thin self supporting layers below 1–2 mm are produced. This represents about 60% of the production. To make self-supporting layers, we use a very clean piece of glass. We deposit a release agent (CsI, KI, adeniney) on the glass and then we deposit the wanted material on the release agent. The system is slowly immersed in water, the release agent dissolves and the material floats on the surface. Then, we fetch the selfsupporting layer on the frame. For materials which oxidise easily, a polymer as release agent is applied and we work in a glove box under controlled atmosphere. An example of a self-supporting layer of 48Ca designed for the GANIL is shown in Fig. 2. We are constantly improving our technique. For example, when there is too much release agent on the glass, the thin layer rolls up in the water and when there is not enough release agent, the thin layer does not part from the glass. We try to find release agents which are not made under vacuum, prepared in advance to save time, and whose thickness is not critical for the layer. We fabricate prototypes. For example, we evaporate thermocouples (alumel, chromel) on particular supports, following an industrial design.
Tel.: + 33 1 69 15 62 75; fax: + 33 1 69 15 51 08.
E-mail address: [email protected] 0168-9002/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2009.09.090
Up to now, we can cover up to 900 cm2 with the electron gun. For example Al is evaporated with a precision of 2% for a 200 nm thickness over this area.
2. The resources Except for the production of polymer layers all techniques are applied under vacuum. The deposition rate and the thickness are measured during the deposition with quartz crystal monitor. (2.1) The laboratory is equipped with three evaporation systems with electron-beam guns. Electron-beam evaporation is the most common technique in the laboratory. Two set-ups are equipped with diffusion pumps (10 7 mbar) which typically allow one experiment per day and the third set-up is equipped with a cryogenic pump (10 10 mbar) which allows two or three experiments per day because of the much faster pumping speed. In Fig. 3a photo of an electron-beam gun is shown. In an electron-beam gun, a tungsten filament is connected to a low voltage power supply to cause an emission of electrons. A strong electric field is generated near the filament to accelerate the electrons which are then curved by a magnetic field. The crucible is water-cooled to avoid an alloy between the material and the crucible. We can use materials with a high melting point up to 3800 1C. (2.2) The laboratory is equipped with an electric arc for C deposition, as shown in Fig. 4. The electric arc runs under vacuum (10 6 mbar) and vaporises material off the graphite electrodes. An important heating occurs in the contact point what requires to make the sublimation of the carbon several times. (2.3) In addition, an electron bombardment is available, as can be seen in Fig. 5. The crucible is a tube which is situated close to the support of the target frame. Electron bombardment is particularly applied for targets out of isotopically enriched
ARTICLE IN PRESS 420
V. Petitbon-The´venet / Nuclear Instruments and Methods in Physics Research A 613 (2010) 419–422
material with a diameter o15 mm and for thin layers (2mm). The process is very material efficient because of the small crucible and the short distance between material and substrate. The thickness has a precision of 5%. This process is applied for expensive and rare isotopes. For example, 1 mg of 48 Ca with an isotopic purity of 99% costs about 400h. For materials sensitive to oxygen, we evaporate the material on a polymer foil on the frame and we use a transfer rod as shown in Fig. 6 to work in a glove box under controlled atmosphere. We stick the layer with a solvent like ethylacetate which dissolves the polymer. (2.4) The laboratory is equipped with a glove under controlled atmosphere. A pumping system brings the pressure down to about 10 2 mbar and a circulation of argon can then be established. In this case, a hygrometry level has to be maintained to 0% (Fig. 7). (2.5) Thermal evaporation: In Fig. 8, a thermal evaporation set-up is shown; the release agent is evaporated from one crucible, the target material from a second. The applied crucible depends on the material. For the evaporation of Au or CsI, we apply a boat out of Ta, W or Mo with or without alumina as shown in Fig. 9. The ‘‘basket heater’’ shown in Fig. 10 is a system used to evaporate with an indirect heating. For Al which boils over easily, we add a W wire to the Al. When the Al melts, it wets the wire and stays in the crucible. The boiling is minimized. The risk of overflowing and short circuit is eliminated. In Fig. 11, the baffled box is shown which is applied to control the evaporation of easily bursting materials like SiO. These different crucibles are connected to the electrodes of a controlled power supply.
(2.6) One polymer hood for the manufacturing of polymer layers is available. The support is dipped into a chemical solution (a mixture between the solvent and the polymer powder). Experimentally, the ratio between the weight of the polymer and the quantity of solvent has to be obtained for the
Fig. 3. Electron gun. 1: Water-cooled crucible, turning crucible with four positions in order to make multilayer. 2: Opening for the electron emission. 3: Shutter.
Fig. 1. Carbon stripper for CEA/DAM Bruye res le Chˆatel, France.
Fig. 2. Self-supporting layer of
Fig. 4. Electric arc for carbon deposition.
48
Ca for the GANIL.
ARTICLE IN PRESS V. Petitbon-The´venet / Nuclear Instruments and Methods in Physics Research A 613 (2010) 419–422
Fig. 5. Electron bombardment.
421
Fig. 8. Thermal set-up.
Fig. 9. Alumina coated evaporation source—R.D Mathis company.
wanted thickness of the polystyrene layer. In order to prepare radioactive layers, we are working on polyimide films, a polymer which can stand temperatures up to 450 1C [1].
Fig. 6. Transfer rod.
3. A recent list of manufacturing The table below shows a list of recent layers made at Orsay. Self supporting Surface deposits
Multilayers
Zr, Al, Au, Cu, Ti, In, Sn, Co, Ca, 48Ca, C, Ta, Ag, Mg, Sc, Si, CD2, CH, 7Li, Niy Au, 11B, C, Al, Pb, Bi, W, CsI, phenylalanine, Sm, 60C, Alumel (Ni90%, Cr10%), Chromel (Ni95%, Al2%, Mn3%, Si1%) Al/C/Al, CH/C, CH/AL, CH/KBr/Si/Al/Si
Target demands out of isotopically enriched materials are typically developed for the natural material first and then the production process is adapted for the enriched material. The behaviour of the natural material is generally identical to the isotopically material in 98% of the cases. The exception known in the targets laboratory is 154Sm.
4. The characterisation
Fig. 7. Glove box under controlled argon atmosphere.
Important quality information for the experimenters is typically the thickness and the chemical purity.
ARTICLE IN PRESS V. Petitbon-The´venet / Nuclear Instruments and Methods in Physics Research A 613 (2010) 419–422
422
Fig. 10. Basket heater with crucible—R.D Mathis company.
http://ipnweb.in2p3.fr/ cibles/, activities of the laboratory are listed in detail. This site, both in French and in English, is commonly used by different companies and research groups to establish contacts with us. Moreover, some presentation brochures are available on enquiry.
6. Future of the lab
Fig. 11. Silicon monoxide source—R.D Mathis company.
In the target manufacturing, we can measure the thickness. Up to now, we have no method to control the purity so we take a lot of precautions to be rigours: we clean regularly, we use systematically gloves, and we protect the different parts which are not easily accessible with aluminium foils to protect them from the pollution. At the CSNSM (Centre de Spectroscopie Nucle´aire et de Spectrome´trie de Masse), a laboratory near the IPNO, we can use RBS method. We have three techniques to measure the thicknesses:
by loss of alpha energy, by mechanical profilometer 2D/3D, where the difference of
height is measured, by the use of a precision balance.
For the laser community additionally the needed foils have to be light tight. We apply a He/Ne laser to control the produced foils. We can visualize holes. The size of holes is unknown. The control is ‘‘all or none’’. If we do not see the laser light in the other side of the layer, it is okay. If we see light in the other side of the layer, we start the manufacture again.
5. Communication Even if the laboratory is mainly dedicated to IPNO’s needs, many requests come from other laboratories. On the web site,
We have started a programme to develop the manufacturing of radioactive layers by electrodeposition [2,3]. Collaborations are under construction with different partners, in order to acquire the necessary knowledge and to be able to arrange necessary means for the characterization of targets. In a first step, we develop collaborations with the radiochemistry group of Orsay, the European IRMM/Geel Institute, the Berkeley University and the Wadworth Institute, the CEA/DAM and the Laboratoire National Henri Becquerel, a national metrology laboratory. This implies to work closely with the safety and security people. In 2009, a specific building should become operational. Development of new techniques: We would like to develop the centrifugation technique to make isotopic layers with backing without losing material. Spin coating is going to be developed, in order to make more homogeneous polymer targets. A recent study showed that the homogeneity of our polymers is bad. There are differences between two points more than + 100%. This means that we will have to re-establish the charts.
7. Conclusion The target manufacturing laboratory tries to answer all the demands so the physicists can obtain interesting results during and after their experiments.
Acknowledgements I would like to thank Patrick Nicol, Patrice Renevret and Julien Mottier who work with me. References ¨ [1] D.C. Aumann, G. Mullen, Nucl. Instr. and Meth. 115 (1974) 75. [2] A. Stolarz, J.V. Gestel, Nucl. Instr. and Meth. 561 (2006) 115. [3] Ch.O. Bacri, Paper on CACAO project, Contribution to this conference.