2025 |
|
A radio-frequency quadrupole prototype additively manufactured as a multi-material component S. Brenner, M. Dickmann, R. Helm, J. Mitteneder, G. Schlick, M. Lehmann, C. Jugert, V. Nedeljkovic-Groha, G. Dollinger and M. Mayerhofer; Progress in Additive Manufacturing 10 (6) (2025) 3951-3961. |
| Abstract: Linear particle accelerators (Linacs) are essential for numerous applications in industry, medicine, and research. However, their use is often constrained by high investment costs, which are largely driven by conventional manufacturing methods. Studies have shown that additive manufacturing (AM) has the potential to significantly reduce these costs while simultaneously enhancing Linac performance. This study investigates this potential for the production of radio-frequency quadrupoles (RFQs), one of the most important Linacs for ion acceleration. For the first time, a multi-material RFQ prototype was fabricated using multi-material (MM) laser powder bed fusion (PBF-LB/M) AM, integrating the copper alloy CuCr1Zr for the internal cavity and tool steel (1.2709) for the outer shell in a single manufacturing step. The prototype’s design features six ConFlat® (CF) flanges for sealing without O-rings, highlighting the advantages of MM AM in simplifying assembly and enhancing functionality. Experimental evaluations included assessments of geometric precision, surface roughness, microstructural integrity, vacuum performance, resonance frequency (fR), and quality factor (Q0). The results demonstrated the successful application of MM PBF-LB/M for RFQ production, achieving a vacuum pressure below 8.3 ∙ 10-8 mbar in the prototype. However, challenges in geometric precision and material transition zones necessitate further process optimization. This work underscores the potential of MM PBF-LB/M to address limitations in mono-material AM, particularly for Linac applications. Future developments, such as enabling pure copper processing and improving thermal and mechanical performance, could establish MM PBF-LB/M as a transformative technology for advanced Linac designs, paving the way for enhanced Linac applications. |
BibTeX:
@article{Brenner2025,
author = {Brenner, Stefan and Dickmann, Marcel and Helm, Ricardo and Mitteneder, Johannes and Schlick, Georg and Lehmann, Maja and Jugert, Constantin and Nedeljkovic-Groha, Vesna and Dollinger, Günther and Mayerhofer, Michael},
title = {A radio-frequency quadrupole prototype additively manufactured as a multi-material component},
journal = {Progress in Additive Manufacturing},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2025},
volume = {10},
number = {6},
pages = {3951--3961},
url = {https://doi.org/10.1007/s40964-025-01120-6},
doi = {https://doi.org/10.1007/s40964-025-01120-6}
}
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Manufacturing Method for Radio-Frequency Cavity Resonators and Corresponding Resonator G. Dollinger and M. Mayerhofer; Patent, Universität der Bundeswehr München, 85577 Neubiberg (DE), 2025. |
| Abstract: A method of manufacturing a radio frequency cavity resonator, wherein said radio frequency cavity resonator comprises a tubular structure extending along a longitudinal axis, said tubular structure comprising a circumferential wall structure surrounding said longitudinal axis, one or more tubular elements and a first and a second support structure associated with each of said tubular elements, wherein said first and second support structures are provided on opposite sides of each tubular element and extend radially along a diameter of the tubular structure, wherein the method comprises producing the resonator by additive manufacturing in a manufacturing direction that is parallel to said diameter. |
BibTeX:
@patent{Dollinger2025,
author = {Dollinger, Günther and Mayerhofer, Michael},
title = {Manufacturing Method for Radio-Frequency Cavity Resonators and Corresponding Resonator},
type = {Patent},
holder = {Universität der Bundeswehr München, 85577 Neubiberg (DE)},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2025},
number = {US12464633 B2},
url = {https://patentscope.wipo.int/search/de/detail.jsf?docId=WO2022017833}
}
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|
Laser powder bed fusion for x-band RF cavities: A preliminary study M. Mayerhofer, S. Brenner, E. Chyhyrynets, M. Dickmann, V. Nedeljkovic-Groha, R. Helm, D. Heußen, J. Mitteneder, C. Pira and G. Dollinger; In: Proceedings of the16th International Particle Accelerator Conference , Journals of Accelerator Conferences Website (2025) 2616-2619 , JACoW Publishing. |
| Abstract: With increasing operational frequency (f_R), the size, weight, and power consumption of linear accelerators (Linacs) decrease, which is why e.g. X-band LinVarious studies show that additive manufacturing (AM) has the potential to significantly reduce the cost of radio frequency cavities (cavities) while increasing performance. With increasing resonance frequency, the size, weight, and power consumption of linear accelerators (Linacs) decrease, which is why, e.g. X-Band Linacs are attractive for industry, medicine, and science. This work investigates, for the first time, whether laser powder bed fusion (PBF-LB/M) offers the geometric accuracy necessary for X-Band cavity manufacturing. Eight 9.29 GHz side-coupled test cavities, each comprising three single cells, were fabricated from CuCr1Zr. One of the cavities was post-processed using plasma electrolytic polishing to increase the quality factor. The manufactured cavities were evaluated using a Vector Network Analyze and an optical 3D profiler. |
BibTeX:
@inproceedings{Mayerhofer2025,
author = {Mayerhofer, Michael and Brenner, Stefan and Chyhyrynets, Eduard and Dickmann, Marcel and Nedeljkovic-Groha, Vesna and Helm, Ricardo and Heußen, Daniel and Mitteneder, Johannes and Pira, Cristian and Dollinger, Günther},
title = {Laser powder bed fusion for x-band RF cavities: A preliminary study},
booktitle = {Proceedings of the16th International Particle Accelerator Conference},
journal = {Journals of Accelerator Conferences Website},
publisher = {JACoW Publishing},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2025},
pages = {2616--2619},
url = {https://indico.jacow.org/event/81/contributions/8722},
doi = {https://doi.org/10.18429/JACOW-IPAC2025-THPB052}
}
|
2024 |
|
Improving Fabrication and Performance of Additively Manufactured RF Cavities by Employing Co-Printed Support Structures and Their Subsequent Removal M. Mayerhofer, S. Brenner, M. Doppler, L. Catarino, S. Girst, V. Nedeljkovic-Groha and G. Dollinger; Instruments 8 (1) (2024) 18. |
| Abstract: The enormous potential of additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), to produce radiofrequency cavities (cavities) has already been demonstrated. However, the required geometrical accuracy for GHz TM010 cavities is currently only achieved by (a) avoiding downskin angles <40∘, which in turn leads to a cavity geometry with reduced performance, or (b) co-printed support structures, which are difficult to remove for small GHz cavities. We have developed an L-PBF-based manufacturing routine to overcome this limitation. To enable arbitrary geometries, co-printed support structures are used that are designed in such a way that they can be removed after printing by electrochemical post-processing, which simultaneously reduces the surface roughness and thus maximizes the quality factor Q0. The manufacturing approach is evaluated on two TM010 single cavities printed entirely from high-purity copper. Both cavities achieve the desired resonance frequency and a Q0 of approximately 8300. |
BibTeX:
@article{Mayerhofer2024,
author = {Mayerhofer, Michael and Brenner, Stefan and Doppler, Michael and Catarino, Luis and Girst, Stefanie and Nedeljkovic-Groha, Vesna and Dollinger, Günther},
title = {Improving Fabrication and Performance of Additively Manufactured RF Cavities by Employing Co-Printed Support Structures and Their Subsequent Removal},
journal = {Instruments},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2024},
volume = {8},
number = {1},
pages = {18},
url = {https://www.mdpi.com/2410-390X/8/1/18},
doi = {https://doi.org/10.3390/instruments8010018}
}
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Red and Green Laser Powder Bed Fusion of Pure Copper in Combination with Chemical Post-Processing for RF Cavity Fabrication M. Mayerhofer, S. Brenner, M. Dickmann, M. Doppler, S. Gruber, R. Helm, E. Lopez, V. Maier, J. Mitteneder, C. Neukirchen, V. Nedeljkovic-Groha, B. Reinarz, M. Schuch, L. Stepien and G. Dollinger; Instruments 8 (3) (2024) . |
| Abstract: Linear particle accelerators (Linacs) are primarily composed of radio frequency cavities (cavities). Compared to traditional manufacturing, Laser Powder Bed Fusion (L-PBF) holds the potential to fabricate cavities in a single piece, enhancing Linac performance and significantly reducing investment costs. However, the question of whether red or green laser PBF yields superior results for pure copper remains a subject of ongoing debate. Eight 4.2 GHz single-cell cavities (SCs) were manufactured from pure copper using both red and green PBF (SCs R and SCs G). Subsequently, the surface roughness of the SCs was reduced through a chemical post-processing method (Hirtisation) and annealed at 460 °C to maximize their quality factor (Q0). The geometric accuracy of the printed SCs was evaluated using optical methods and resonant frequency (fR) measurements. Surface conductivity was determined by measuring the quality factor (Q0) of the SCs. Laser scanning microscopy was utilized for surface roughness characterization. The impact of annealing was quantified using Energy-Dispersive X-ray Spectroscopy and Electron Backscatter Diffraction to evaluate chemical surface properties and grain size. Both the SCs R and SCs G achieved the necessary geometric accuracy and thus fR precision. The SCs R achieved a 95% Q0 after a material removal of 40 µm. The SCs G achieved an approximately 80% Q0 after maximum material removal of 160 µm. Annealing increased the Q0 by an average of about 5%. The additive manufacturing process is at least equivalent to conventional manufacturing for producing cavities in the low-gradient range. The presented cavities justify the first high-gradient tests. |
BibTeX:
@article{Mayerhofer2024a,
author = {Mayerhofer, Michael and Brenner, Stefan and Dickmann, Marcel and Doppler, Michael and Gruber, Samira and Helm, Ricardo and Lopez, Elena and Maier, Verena and Mitteneder, Johannes and Neukirchen, Carsten and Nedeljkovic-Groha, Vesna and Reinarz, Bernd and Schuch, Michael and Stepien, Lukas and Dollinger, Günther},
title = {Red and Green Laser Powder Bed Fusion of Pure Copper in Combination with Chemical Post-Processing for RF Cavity Fabrication},
journal = {Instruments},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2024},
volume = {8},
number = {3},
url = {https://www.mdpi.com/2410-390X/8/3/39},
doi = {https://doi.org/10.3390/instruments8030039}
}
|
2023 |
|
A carbon minibeam irradiation facility concept M. Mayerhofer, V. Bencini, M. Sammer and G. Dollinger; Journal of Physics: Conference Series 2420 (1) (2023) 012097. |
| Abstract: In minibeam therapy, the sparing of deep-seated normal tissue is limited by transverse beam spread caused by small-angle scattering. Contrary to proton minibeams, helium or carbon minibeams experience less deflection, which potentially reduces side effects. To verify this potential, an irradiation facility for preclinical and clinical studies is needed. This manuscript presents a concept for a carbon minibeam irradiation facility based on a LINAC design for conventional carbon therapy. A quadrupole triplet focuses the LINAC beam to submillimeter minibeams. A scanning and a dosimetry unit are provided to move the minibeam over the target and monitor the applied dose. The beamline was optimized by TRAVEL simulations. The interaction between beam and these components and the resulting beam parameters at the focal plane is evaluated by TOPAS simulations. A transverse beamwidth of < 100 μm (sigma) and a peak-to-valley (energy) dose ratio of > 1000 results for carbon energies of 100 MeV/u and 430 MeV/u (∼ 3 cm and 30 cm range in water) whereby the average beam current is ∼ 30 nA. Therefore, the presented irradiation facility exceeds the requirements for hadron minibeam therapy. |
BibTeX:
@article{Mayerhofer2023,
author = {Mayerhofer, M. and Bencini, V. and Sammer, M. and Dollinger, G.},
title = {A carbon minibeam irradiation facility concept},
journal = {Journal of Physics: Conference Series},
publisher = {IOP Publishing},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2023},
volume = {2420},
number = {1},
pages = {012097},
url = {https://iopscience.iop.org/article/10.1088/1742-6596/2420/1/012097},
doi = {https://doi.org/10.1088/1742-6596/2420/1/012097}
}
|
|
Additive Manufacturing of Side-Coupled Cavity Linac Structures from Pure Copper: A First Concept M. Mayerhofer, S. Brenner, R. Helm, S. Gruber, E. Lopez, L. Stepien, G. Gold and G. Dollinger; Instruments 7 (4) (2023) 56. |
| Abstract: Compared to conventional manufacturing, additive manufacturing (AM) of radio frequency (RF) cavities has the potential to reduce manufacturing costs and complexity and to enable higher performance. This work evaluates whether normal conducting side-coupled linac structures (SCCL), used worldwide for a wide range of applications, can benefit from AM. A unit cell geometry (SC) optimized for 75 MeV protons was developed. Downskins with small downskin angles α were avoided to enable manufacturing by laser powder bed fusion without support structures. SCs with different α were printed and post-processed by Hirtisation (R) (an electrochemical process) to minimize surface roughness. The required accuracy for 3 GHz SCCL (medical linacs) is achieved only for α>45∘. After a material removal of 140 µm due to Hirtisation (R), a quality factor Q0 of 6650 was achieved. This corresponds to 75% of the Q0 simulated by CST®. A 3 GHz SCCL concept consisting of 31 SCs was designed. The effective shunt impedance ZT2 simulated by CST corresponds to 60.13MΩm and is comparable to the ZT2 of SCCL in use. The reduction in ZT2 expected after Hirtisation (R) can be justified in practice by up to 70% lower manufacturing costs. However, future studies will be conducted to further increase Q0. |
BibTeX:
@article{Mayerhofer2023a,
author = {Mayerhofer, Michael and Brenner, Stefan and Helm, Ricardo and Gruber, Samira and Lopez, Elena and Stepien, Lukas and Gold, Gerald and Dollinger, Günther},
title = {Additive Manufacturing of Side-Coupled Cavity Linac Structures from Pure Copper: A First Concept},
journal = {Instruments},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2023},
volume = {7},
number = {4},
pages = {56},
url = {https://www.mdpi.com/2410-390X/7/4/56},
doi = {https://doi.org/10.3390/instruments7040056}
}
|
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First high quality DTL cavity additively manufactured from pure copper M. Mayerhofer, J. Mitteneder, C. Wittig, I. Prestes, E. Jägle and G. Dollinge; In: , R. Assmann, P. McIntosh, G. Bisoffi, Elettra-Sincrotrone, I. Andrian and G. Vinicola (Eds.), Proc. 14th International Particle Accelerator Conference (IPAC'23) , JACoW 14 (2023) 4967-4970 , JACoW Publishing, Geneva, Switzerland. |
| Abstract: Recently presented RF cavity prototypes printed entirely from pure copper illustrate the potential of additive manufacturing (AM), and particularly laser powder bed fusion (L-PBF), for accelerator technology. Thereby, the design freedom of L-PBF is only limited by overhanging geometries, which have to be printed with supporting structures to ensure sufficient accuracy. However, subsequent removal of these support structures is a major challenge for cm-sized GHz cavities. Therefore, our approach is to design self-supporting geometries. In this contribution we present a DTL cavity geometry as used in e.g. proton therapy linac systems that can be fabricated by L-PBF without support structures. A 5-cell prototype was manufactured from high-purity copper using L-PBF. It is shown that the developed geometry allows a print accuracy sufficient to reach the defined resonance frequency. A chemical, as well as dynamic electrochemical finishing process, was applied to optimize the prototypes surface quality. Thus, the CST simulated figures of merit (e.g., Q_0, Z_eff) were obtained for the first time with a printed cavity. |
BibTeX:
@inproceedings{Mayerhofer2023b,
author = {Mayerhofer, M. and Mitteneder, J. and Wittig, C. and Prestes, I. and Jägle, E. and Dollinge, G.},
title = {First high quality DTL cavity additively manufactured from pure copper},
booktitle = {Proc. 14th International Particle Accelerator Conference (IPAC'23)},
journal = {JACoW},
publisher = {JACoW Publishing, Geneva, Switzerland},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2023},
volume = {14},
number = {13},
pages = {4967-4970},
editor = {Ralph Assmann and Peter McIntosh and Giovanni Bisoffi and Elettra-Sincrotrone and Ivan Andrian and Giulia Vinicola},
url = {https://accelconf.web.cern.ch/ipac2023/doi/jacow-ipac2023-thpm035/},
doi = {https://doi.org/10.18429/JACoW-IPAC2023-THPM035}
}
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Entwicklung eines Störkörpermessstandes zur Charakterisierung von Hochfrequenz-Hohlraumresonatoren Cedric Wittig; Bachelors-Thesis, Universität der Bundeswehr München, 2023. |
| Abstract: Die resonante Störkörpermessung ist eine Methode zur Charakterisierung des elektromagnetischen Feldes in Hochfrequenz-Hohlraumresonatoren (fortlaufend als Resonator bezeichnet) und gilt als schnelles und zuverlässiges Mittel zur Bestimmung wichtiger Kenngrößen, wie z.B. den Gütefaktor QL. Durch Einbringen eines dielektrischen Körpers in einen Resonator verschiebt sich auf Grund der hervorgerufenen Kapazitätserhöhung die Resonanzfrequenz. Anhand der lokalen Bestimmung dieser Frequenzverschiebung an zahlreichen Messpunkten auf der Strahlachse ist es möglich, die Verteilung des elektrischen Feldes und folglich die Shunt-Impedanz als Indikator der Performance eines Resonators zu bestimmen. Im Rahmen dieser Arbeit wird ein Störkörpermessstand entwickelt, mit dem die resonante Störkörpermessung für Resonatoren automatisch und in kurzer Zeit durchgeführt werden kann. Der Messstand besteht im wesentlichen aus einem motorisierten Linearmodul, einem Mikrocontroller und einem Vektor-Netzwerk-Analysator, welche zentral über eine auf LabV IEW basierende Messstand-Software gesteuert werden. Um den Messstand zu charakterisieren, werden verschiedene Messungen der TM010-Mode an einem bereits charakterisierten Driftröhrenlinearbeschleuniger (engl. Drift Tube Linac (DTL)) durchgeführt. Zunächst wird die Störkörperkonstante α bestimmt, welche den Einfluss des Störkörpers auf das elektrische Feld beschreibt. Anschließend erfolgt unter Betrachtung verschiedener Abstände der einzelnen Messpunkte eine Bestimmung der relativen und absoluten Messgenauigkeit der Feldamplituden und deren Position in longitudinaler Richtung am Störkörpermessstand. Abschließend wird ein mittels Additiver Fertigung hergestellter DTL durch den entwickelten Störkörpermessstand charakterisiert und dessen Shunt-Impedanz bestimmt. |
BibTeX:
@mastersthesis{Wittig2023,
author = {Wittig, Cedric},
title = {Entwicklung eines Störkörpermessstandes zur Charakterisierung von Hochfrequenz-Hohlraumresonatoren},
school = {Universität der Bundeswehr München},
year = {2023}
}
|
2022 |
|
Manufacturing Method for Radio-Frequency Cavity Resonators and Corresponding Resonator G. Dollinger and M. Mayerhofer; Patent, Universität der Bundeswehr München, 85577 Neubiberg (DE), 2022. |
| Abstract: Disclosed herein is a method of manufacturing a radio frequency cavity resonator, wherein said radio frequency cavity resonator comprises a tubular structure extending along a longitudinal axis, said tubular structure comprising a circumferential wall structure surrounding said longitudinal axis, one or more tubular elements and a first and a second support structure associated with each of said tubular elements, wherein said first and second support structures are provided on opposite sides of each tubular element and extend radially along a diameter of the tubular structure, wherein the method comprises producing the resonator by additive manufacturing in a manufacturing direction that is parallel to said diameter. |
BibTeX:
@patent{Dollinger2022,
author = {Dollinger, Günther and Mayerhofer, Michael},
title = {Manufacturing Method for Radio-Frequency Cavity Resonators and Corresponding Resonator},
type = {Patent},
holder = {Universität der Bundeswehr München, 85577 Neubiberg (DE)},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2022},
number = {EP3944725 A1},
url = {https://register.epo.org/application?number=EP20187438}
}
|
|
Manufacturing Method for Radio-Frequency Cavity Resonators and Corresponding Resonator G. Dollinger and M. Mayerhofer; Patent, Universität der Bundeswehr München, 85577 Neubiberg (DE), 2022. |
| Abstract: Disclosed herein is a method of manufacturing a radio frequency cavity resonator, wherein said radio frequency cavity resonator comprises a tubular structure extending along a longitudinal axis, said tubular structure comprising a circumferential wall structure surrounding said longitudinal axis, one or more tubular elements and a first and a second support structure associated with each of said tubular elements, wherein said first and second support structures are provided on opposite sides of each tubular element and extend radially along a diameter of the tubular structure, wherein the method comprises producing the resonator by additive manufacturing in a manufacturing direction that is parallel to said diameter. |
BibTeX:
@patent{Dollinger2022a,
author = {Dollinger, Günther and Mayerhofer, Michael},
title = {Manufacturing Method for Radio-Frequency Cavity Resonators and Corresponding Resonator},
type = {Patent},
holder = {Universität der Bundeswehr München, 85577 Neubiberg (DE)},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2022},
number = {WO 2022/017833 A1, EP4186340 A1},
url = {https://patentscope.wipo.int/search/de/detail.jsf?docId=WO2022017833}
}
|
|
A 3D printed pure copper drift tube linac prototype M. Mayerhofer, J. Mitteneder and G. Dollinger; Review of Scientific Instruments 93 (2) (2022) 023304. |
| Abstract: Radio frequency cavities are among the most challenging and costly components of an accelerator facility. They are usually manufactured in individual parts, which are then joined by complex processes, e.g., several brazing steps. 3D printing has become an alternative to these conventional manufacturing methods due to higher cost efficiency, freedom in design, and recent achievement of high print quality for pure copper. A fully functional 3 GHz drift tube linac (DTL) prototype was 3D printed in one piece, made from pure copper by selective laser melting (SLM). To achieve a higher surface quality, the DTL geometry was optimized for the SLM process. The DTL design is related to the design of the DTL part of the side-coupled DTL modules used in linac-based proton therapy facilities. The quality factor (8750) and the shunt impedance per unit length (102 mΩ/m) of the printed prototype are already comparable to traditionally manufactured DTL structures and can be further enhanced by surface treatments. |
BibTeX:
@article{Mayerhofer2022,
author = {Mayerhofer, Michael and Mitteneder, Johannes and Dollinger, Günther},
title = {A 3D printed pure copper drift tube linac prototype},
journal = {Review of Scientific Instruments},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2022},
volume = {93},
number = {2},
pages = {023304},
url = {https://aip.scitation.org/doi/full/10.1063/5.0068494},
doi = {https://doi.org/10.1063/5.0068494}
}
|
|
A Carbon Minibeam Irradiation Facility Concept M. Mayerhofer, V. Bencini, G. Dollinger and M.A. Sammer; In: Proc. 13th International Particle Accelerator Conference (IPAC'22) , JACoW (2022) 2947-2950 , JACoW Publishing, Geneva, Switzerland. |
| Abstract: In minibeam therapy, the sparing of deep-seated normal tissue is limited by transverse beam spread caused by small-angle scattering. Contrary to proton minibeams, helium or carbon minibeams experience less deflection, which potentially reduces side effects. To verify this potential, an irradiation facility for preclinical and clinical studies is needed. This manuscript presents a concept for a carbon minibeam irradiation facility based on a LINAC design for conventional carbon therapy. A quadrupole triplet focuses the LINAC beam to submillimeter minibeams. A scanning and a dosimetry unit are provided to move the minibeam over the target and monitor the applied dose. The beamline was optimized by TRAVEL simulations. The interaction between beam and these components and the resulting beam parameters at the focal plane is evaluated by TOPAS simulations. A transverse beamwidth of < 100 µm (σ) and a peak-to-valley (energy) dose ratio of > 1000 results for carbon energies of 100 MeV/u and 430 MeV/u (about 3 cm and 30 cm range in water) whereby the average beam current is about 30 nA. Therefore, the presented irradiation facility exceeds the requirements for hadron minibeam therapy. |
BibTeX:
@inproceedings{Mayerhofer2022a,
author = {Mayerhofer, M. and Bencini, V. and Dollinger, G. and Sammer, M. A.},
title = {A Carbon Minibeam Irradiation Facility Concept},
booktitle = {Proc. 13th International Particle Accelerator Conference (IPAC'22)},
journal = {JACoW},
publisher = {JACoW Publishing, Geneva, Switzerland},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2022},
number = {13},
pages = {2947--2950},
url = {https://jacow.org/ipac2022/papers/thpoms006.pdf},
doi = {https://doi.org/10.18429/JACoW-IPAC2022-THPOMS006}
}
|
2021 |
|
Concept and performance evaluation of two 3 GHz buncher units optimizing the dose rate of a novel preclinical proton minibeam irradiation facility M. Mayerhofer, A. Bergmaier, G. Datzmann, H. Hagn, R. Helm, J. Mitteneder, R. Schubert, L. Picardi, P. Nenzi, C. Ronsivalle, H.-F. Wirth and G. Dollinger; PLOS ONE 16 (10) (2021) 1-19. |
| Abstract: To demonstrate the large potential of proton minibeam radiotherapy (pMBRT) as a new method to treat tumor diseases, a preclinical proton minibeam radiation facility was designed. It is based on a tandem Van-de-Graaff accelerator providing a 16 MeV proton beam and a 3 GHz linac post-accelerator (designs: AVO-ADAM S.A, Geneva, Switzerland and ENEA, Frascati, Italy). To enhance the transmission of the tandem beam through the post-accelerator by a factor of 3, two drift tube buncher units were designed and constructed: A brazed 5-gap structure (adapted SCDTL tank of the TOP-IMPLART project (ENEA)) and a non-brazed low budget 4-gap structure. Both are made of copper. The performance of the two differently manufactured units was evaluated using a 16 MeV tandem accelerator beam and a Q3D magnetic spectrograph. Both buncher units achieve the required summed voltage amplitude of 42 kV and amplitude stability at a power feed of less than 800 W. |
BibTeX:
@article{Mayerhofer2021a,
author = {Mayerhofer, Michael and Bergmaier, Andreas and Datzmann, Gerd and Hagn, Hermann and Helm, Ricardo and Mitteneder, Johannes and Schubert, Ralf and Picardi, Luigi and Nenzi, Paolo and Ronsivalle, Concetta and Wirth, Hans-Friedrich and Dollinger, Günther},
title = {Concept and performance evaluation of two 3 GHz buncher units optimizing the dose rate of a novel preclinical proton minibeam irradiation facility},
journal = {PLOS ONE},
publisher = {Public Library of Science},
type = {OpenAccess},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2021},
volume = {16},
number = {10},
pages = {1-19},
url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258477},
doi = {https://doi.org/10.1371/journal.pone.0258477}
}
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Eine präklinische Protonen-Minibeam-Bestrahlungsanlage Michael Mayerhofer; Dissertation, Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther, 2021. |
| Abstract: Studien in einem Mausohrmodell, an Rattenhirnen und in in-vitro Modellen der menschlichen Haut haben gezeigt, dass die Protonen-Minibeam-Strahlentherapie (pMBRT) das Potential hat, Normalgewebekomplikationen im Vergleich zur herkömmlichen Protonentherapie zu reduzieren. Das Ziel dieser Arbeit war die Konzeption einer präklinischen Protonen-Minibeam-Bestrahlungsanlage, die es ermöglicht, weiterführende Studien in einem Kleintier-Tumormodell durchzuführen. Das Konzept der präklinischen Bestrahlungsanlage basiert auf einem Tandem-Beschleuniger, der als Injektor einen 16 MeV Protonen-Strahl liefert, dessen Energie anschließend durch einen linearen 3 GHz Nachbeschleuniger (engl.: linear accelerator (Linac)) auf 70 MeV erhöht wird. Das entspricht einer Reichweite der Protonen in Wasser von mehr als 40 mm. Der Linac besteht aus zwei Side Coupled Drift Tube Linac (SCDTL) Strukturen und vier Coupled Cavity Linac (CCL) Strukturen, welche vom für die herkömmliche Protonentherapie entwickelten All-Linac-System LIGHT (AVO-ADAM SA, Genf, Schweiz) übernommen werden. Um die Transmission durch den Linac zu erhöhen, wird der Phasenraum des Tandemstrahls mithilfe einer 3 GHz Buncher-Einheit und einem Quadrupol-Quartett auf den akzeptierten Phasenraum des Linacs optimiert. Ein stromabwärts nach dem Linac positioniertes Quadrupol-Triplett fokussiert den Protonenstrahl zu Minibeams. Strahldynamik-Simulationen zeigen, dass die Transmission durch den Linac bei einer Buncher-Amplitude von 42 kV um einen Faktor 3 erhöht wird und insgesamt 54 % aller Tandem-Protonen (Strahlstrom ca. 21 nA) in einen Strahlfleck mit einer transversalen Ausdehnung von 77 µm (FWHM) fokussiert werden. Ein Scanning-System, bestehend aus vier Dipolmagneten, das zwischen Linac und Quadrupol-Triplett positioniert ist, ermöglicht das Verfahren des Strahls über eine Fläche von 30 mm x 30 mm am Fokus. Nach der Strahlextraktion an Luft hat der maximal ausgelenkte Strahl eine transversale Ausdehnung von 204 µm (FWHM). Bei der Applikation mehrerer solcher Protonen-Minibeams mit einem Center-to-Center-Abstand von 1,2 mm wird an der Fokusebene ein Peak-to-Valley-Verhältnis von ca. 780 erreicht. So erfüllt die entwickelte präklinische Protonen-Minibeam-Bestrahlungsanlage alle Voraussetzungen für zukünftige präklinische Experimente. Weitere Simulationen zeigen, dass sich auch das kommerziell erhältliche All-Linac-System LIGHT als präklinische Protonen-Minibeam-Bestrahlungsanlage eignet. Im Falle eines bestehenden Tandem-Injektors ist die entwickelte Tandem-Linac-Kombination jedoch deutlich günstiger zu realisieren. Das einzige zusätzlich nötige Element für die Tandem-Linac-Kombination, das nicht kommerziell erhältlich ist, ist die Buncher-Einheit, weshalb im Rahmen dieser Arbeit zwei Prototypen entwickelt und gefertigt werden. Beide Prototypen beruhen auf dem Prinzip des Drift-Röhren-Linac (engl.: drift tube linac (DTL)). Ein Prototyp ist als kostengünstiges Studienobjekt konzipiert, dessen Hohlraumresonator durch Schrauben zusammengepresst wird, was eine einfache Demontage erlaubt. Der Hohlraumresonator des anderen Prototyps ist hartgelötet, um die elektrische Oberflächenleitfähigkeit zu maximieren und ein Kühlsystem zu integrieren. Die Performance der beiden Prototypen wird mit einem Q3D-Magnetspektrographen evaluiert, wobei beide die geforderte Buncher-Amplitude (42 kV) bei einer Eingangsleistung unter 800 W erreichen. Der aufwendige Hartlötprozess bei der traditionellen Herstellung war Motivation zu evaluieren, ob sich auch 3D-Druck-Verfahren zur Fertigung von Hohlraumresonatoren eignen. Ein 3 GHz DTL-Prototyp wird entwickelt und für den 3D-Druck durch selektives Laserschmelzen optimiert. Der aus hochreinem Kupfer gedruckte DTL-Prototyp erreicht einen Gütefaktor von 8750 und eine Shunt-Impedanz von 53 MOhm/m, was das große Potential von 3D-Druck-Verfahren zur Herstellung von Hohlraumresonatoren zeigt. Im Hinblick auf die stark reduzierten Herstellungskosten und die große Designfreiheit motivieren die Ergebnisse, dieses Potential für die Herstellung noch komplexerer Hohlraumresonator-Geometrien weiter zu evaluieren. |
BibTeX:
@phdthesis{Mayerhofer2021diss,
author = {Mayerhofer, Michael},
title = {Eine präklinische Protonen-Minibeam-Bestrahlungsanlage},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther},
year = {2021},
url = {https://nbn-resolving.org/urn/resolver.pl?urn:nbn:de:bvb:706-7876}
}
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2020 |
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Preclinical Challenges in Proton Minibeam Radiotherapy: Physics and Biomedical Aspects G. Datzmann, M. Sammer, S. Girst, M. Mayerhofer, G. Dollinger and J. Reindl; Frontiers in Physics 8 (2020) 471. |
| Abstract: The concept of spatial fractionation in radiotherapy was developed for better sparing of normal tissue in the entrance channel of radiation. Spatial fractionation utilizing proton minibeam radiotherapy (pMBRT) promises to be advantageous compared to X-ray minibeams due to higher dose conformity at the tumor. Preclinical in vivo experiments conducted with pMBRT in mouse ear models or in rat brains support the prospects, but the research about the radiobiological mechanisms and the search for adequate application parameters delivering the most beneficial minibeam therapy is still in its infancy. Concerning preclinical research, we consider glioma, non-small cell lung cancer and hepatocellular carcinoma as the most promising targets and propose investigating the effects on healthy tissue, especially neuronal cells and abdominal organs. The experimental setups for preclinical pMBRT used so far follow different technological approaches, and experience technical limitations when addressing the current questions in the field. We review the crucial physics parameters necessary for proton minibeam production and link them to the technological challenges to be solved for providing an optimal research environment. We consider focusing of pencil or planar minibeams in a scanning approach superior compared to collimation due to less beam halos, higher peak-to-valley dose ratios and higher achievable dose rates. A possible solution to serve such a focusing system with a high-quality proton beam at all relevant energies is identified to be a 3 GHz radio-frequency linear accelerator. We propose using a 16 MeV proton beam from an existing tandem accelerator injected into a linear post-accelerator, boosted up to 70 MeV, and finally delivered to an imaging and positioning end-station suitable for small animal irradiation. Ion-optical simulations show that this combination can generate focused proton minibeams with sizes down to 0.1 mm at 18 nA mean proton current - sufficient for all relevant preclinical experiments. This technology is expected to offer powerful and versatile tools for unleashing structured and advanced preclinical pMBRT studies at the limits and also has the potential to enable a next step into precision tumor therapy. |
BibTeX:
@article{Datzmann2020,
author = {Datzmann, Gerd and Sammer, Matthias and Girst, Stefanie and Mayerhofer, Michael and Dollinger, Günther and Reindl, Judith},
title = {Preclinical Challenges in Proton Minibeam Radiotherapy: Physics and Biomedical Aspects},
journal = {Frontiers in Physics},
school = {Universität der Bundeswehr München, Fakultät für Luft- und Raumfahrttechnik, LRT 2 - Institut für Angewandte Physik und Messtechnik, Professur: Dollinger, Günther ; Reindl, Judith},
year = {2020},
volume = {8},
pages = {471},
url = {https://www.frontiersin.org/article/10.3389/fphy.2020.568206},
doi = {https://doi.org/10.3389/fphy.2020.568206}
}
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