IPAC2021 - List of Authors (Winklehner, D.)

Paper	Title	Page
MOPAB159	Matching of an RFQ and Multicusp Ion Source with Compact LEBT	546
	L.H. Waites, J.M. Conrad, J. Smolsky, D. Winklehner MIT, Cambridge, Massachusetts, USA
	Funding: NSF provided funding for RFQ-DIP project, Draper Laboratory provided fellowship for graduate studnets The IsoDAR project is a neutrino experiment that requires a high current H²⁺ beam at 60 MeV/amu, which will be produced by a cyclotron. A critical aspect of the design is the injection, which comprises an ion source, a compact low energy beam transport section (LEBT), and a radio-frequency quadrupole (RFQ) buncher embedded in the cyclotron yoke. The LEBT is optimized to match the desired input Twiss parameters of the RFQ. Here we report on the latest results from the ion source commissioning, and on the design and optimization of the LEBT with matching to the RFQ. With this ion source, we have demonstrated a 76% H²⁺ fraction at a current density of 11 mA/cm² in DC mode. The design of the LEBT includes a chopper, steering elements, and focusing elements, to achieve the desired matching, which according to our simulations leads to ~95% transmission from the ion source to the exit of the RFQ.
	Poster MOPAB159 [0.851 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB159
About •	paper received ※ 15 May 2021 paper accepted ※ 24 June 2021 issue date ※ 13 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPAB160	Tools for the Development and Applications of the IsoDAR Cyclotron	550
	L.H. Waites, J.R. Alonso, J.M. Conrad, D. Koser, D. Winklehner MIT, Cambridge, Massachusetts, USA
	Funding: NSF provided funding for the RFQDIP project, Draper laboratory provided a fellowship for the graduate student The IsoDAR cyclotron is a 60 MeV cyclotron designed to output 10mA of protons in order to be a driver for a neutrino experiment. However, this high power can be used in other useful and important applications outside of particle physics. The IsoDAR cyclotron accelerates H²⁺, which allows the beam to be highly versatile and important for the development of high-power targets. This could help alleviate a huge bottleneck in the medical isotope community. IsoDAR could also be used for the development of materials. The accelerator system uses many new tools, including novel methods of applying machine learning, as well as several of the uses of this new technology. With these applications and tools, the IsoDAR cyclotron can have an important impact on the accelerator, medical, and physics communities.
	Poster MOPAB160 [0.424 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB160
About •	paper received ※ 15 May 2021 paper accepted ※ 24 June 2021 issue date ※ 13 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUXB07	High-Current H₂⁺ Beams from a Compact Cyclotron using RFQ Direct Injection	1301
	D. Winklehner, J.M. Conrad, D. Koser, J. Smolsky, L.H. Waites MIT, Cambridge, Massachusetts, USA
	Funding: This work was supported by NSF grants PHY-1505858 and PHY-1626069. For the IsoDAR neutrino experiment, we have developed a compact and cost-effective cyclotron-based driver to produce high current beams (cw proton beam currents of >10 mA at 60 MeV). This is a factor of 4 higher than the current state-of-the-art for cyclotrons and a factor of 10 compared to what is commercially available. All areas of physics that call for high cw currents can greatly benefit from this result; e.g. particle physics, medical isotope production, and energy research. This increase in beam current is possible in part because the cyclotron is designed to include and use vortex-motion, allowing clean extraction. Such a design process is only possible with the help of high-fidelity codes, like OPAL. Another novelty is the use of an RFQ embedded in the cyclotron yoke to bunch the beam during axial injection. Finally, using H²⁺ relieves some of the space charge constraints during injection. In this paper, we will give an overview of the project and then focus on the design and simulations of the cyclotron itself. We will describe the physics, computational tools, and simulation results. At the end, we will describe how we are including machine learning in the simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB07
About •	paper received ※ 27 May 2021 paper accepted ※ 22 July 2021 issue date ※ 31 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB195	Design and Optimization of a Low Frequency RF-Input Coupler for the IsoDAR RFQ	3081
	M.P. Sangroula, J.M. Conrad, D. Winklehner MIT, Cambridge, Massachusetts, USA M. Schuett BEVATECH, Frankfurt, Germany
	Funding: The RFQ-DIP project is supported by National Science Foundation grant \# PHY-1626069 and the Heising-Simons Foundation. The Isotope Decay-At-Rest experiment (IsoDAR) is a proposed underground experiment which is expected to be a definitive search for sterile neutrinos. IsoDAR uses an especially designed low-frequency spilt-coaxial radio frequency quadrupole (RFQ) to accelerate H²⁺ ions directly from the ion source into the main cyclotron accelerator. This paper mainly focuses on the design and optimization of a low frequency (32.8 MHz) RF-input coupler for the IsoDAR RFQ. Starting with a basic design, we determine its appropriate position for this coupler in the RFQ. Finally, we optimized the design to lower the input power without compromising the coupling efficiency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB195
About •	paper received ※ 21 May 2021 paper accepted ※ 30 June 2021 issue date ※ 29 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB202	Thermal Analysis of a Compact Split-Coaxial CW RFQ for the IsoDAR RFQ-DIP	3097
	D. Koser, J.M. Conrad, D. Winklehner MIT, Cambridge, Massachusetts, USA H. Podlech, U. Ratzinger, M. Schuett BEVATECH, Frankfurt, Germany
	The RFQ direct injection project (RFQ-DIP) for the neutrino physics experiment IsoDAR aims at an efficient injection of a high-current H²⁺ beam into the dedicated 60 MeV driver cyclotron. Therefore, it is intended to use a compact 32.8 MHz RFQ structure of the split-coaxial type as a pre-buncher. To determine the thermal elongation of the 1.4 m long electrode rods as well as the thermal frequency detuning of the RF structure at a maximum nominal power load of 3.6 kW, an extensive thermal and structural mechanical analysis using COMSOL Multiphysics was conducted. The water heating along the cooling channels as well as the properties of heat transfer from the copper structure to the cooling water were taken into account, which required CFD simulations of the cooling water flow in the turbulent regime. Here we present the methods and results of the sophisticated thermal and structural mechanical simulations using COMSOL and provide a comparison to more simplistic simulations conducted with CST Studio Suite.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB202
About •	paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 14 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB203	RFQ Beam Dynamics Optimization Using Machine Learning	3100
	D. Koser, J.M. Conrad, L.H. Waites, D. Winklehner MIT, Cambridge, Massachusetts, USA A. Adelmann, M. Frey, S. Mayani PSI, Villigen PSI, Switzerland
	To efficiently inject a high-current H²⁺ beam into the 60 MeV driver cyclotron for the proposed IsoDAR project in neutrino physics, a novel direct-injection scheme is planned to be implemented using a compact radio-frequency quadrupole (RFQ) as a pre-buncher, being partially inserted into the cyclotron yoke. To optimize the RFQ beam dynamics design, machine learning approaches were investigated for creating a surrogate model of the RFQ. The required sample datasets are generated by standard beam dynamics simulation tools like PARMTEQM and RFQGen or more sophisticated PIC simulations. By reducing the computational complexity of multi-objective optimization problems, surrogate models allow to perform sensitivity studies and an optimization of the crucial RFQ beam output parameters like transmission and emittances. The time to solution might be reduced by up to several orders of magnitude. Here we discuss different methods of surrogate model creation (polynomial chaos expansion and neural networks) and identify present limitations of surrogate model accuracy.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB203
About •	paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 30 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB167	Technical Design of an RFQ Injector for the IsoDAR Cyclotron	4075
	H. Höltermann, D. Koser, B. Koubek, H. Podlech, U. Ratzinger, M. Schuett, M. Syha BEVATECH, Frankfurt, Germany J.M. Conrad, J. Smolsky, L.H. Waites, D. Winklehner MIT, Cambridge, Massachusetts, USA
	For the IsoDAR (Isotope Decay-At-Rest) experiment, a high intensity (10 mA CW) primary proton beam is needed. To generate this beam, H²⁺ is accelerated in a cyclotron and stripped into protons after extraction. An RFQ, partially embedded in the cyclotron yoke, will be used to bunch and axially inject H²⁺ ions into the main accelerator. The strong RFQ bunching capabilities will be used to optimize the overall injection efficiency. To keep the setup compact the distance between the ion source and RFQ can be kept very short as well. In this paper, we describe the technical design of the RFQ. We focus on two critical aspects: 1. The use of a split-coaxial structure, necessitated by the low frequency of 32.8 MHz (matching the cyclotron RF) and the desired small tank diameter; 2. The high current, CW operation, requiring a good cooling concept for the RFQ tank and vanes.
	Poster THPAB167 [2.162 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB167
About •	paper received ※ 14 May 2021 paper accepted ※ 27 July 2021 issue date ※ 21 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Matching of an RFQ and Multicusp Ion Source with Compact LEBT

546

L.H. Waites, J.M. Conrad, J. Smolsky, D. Winklehner
MIT, Cambridge, Massachusetts, USA

Funding: NSF provided funding for RFQ-DIP project, Draper Laboratory provided fellowship for graduate studnets
The IsoDAR project is a neutrino experiment that requires a high current H²⁺ beam at 60 MeV/amu, which will be produced by a cyclotron. A critical aspect of the design is the injection, which comprises an ion source, a compact low energy beam transport section (LEBT), and a radio-frequency quadrupole (RFQ) buncher embedded in the cyclotron yoke. The LEBT is optimized to match the desired input Twiss parameters of the RFQ. Here we report on the latest results from the ion source commissioning, and on the design and optimization of the LEBT with matching to the RFQ. With this ion source, we have demonstrated a 76% H²⁺ fraction at a current density of 11 mA/cm² in DC mode. The design of the LEBT includes a chopper, steering elements, and focusing elements, to achieve the desired matching, which according to our simulations leads to ~95% transmission from the ion source to the exit of the RFQ.

Poster MOPAB159 [0.851 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB159

About •

paper received ※ 15 May 2021 paper accepted ※ 24 June 2021 issue date ※ 13 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPAB160

Tools for the Development and Applications of the IsoDAR Cyclotron

550

L.H. Waites, J.R. Alonso, J.M. Conrad, D. Koser, D. Winklehner
MIT, Cambridge, Massachusetts, USA

Funding: NSF provided funding for the RFQDIP project, Draper laboratory provided a fellowship for the graduate student
The IsoDAR cyclotron is a 60 MeV cyclotron designed to output 10mA of protons in order to be a driver for a neutrino experiment. However, this high power can be used in other useful and important applications outside of particle physics. The IsoDAR cyclotron accelerates H²⁺, which allows the beam to be highly versatile and important for the development of high-power targets. This could help alleviate a huge bottleneck in the medical isotope community. IsoDAR could also be used for the development of materials. The accelerator system uses many new tools, including novel methods of applying machine learning, as well as several of the uses of this new technology. With these applications and tools, the IsoDAR cyclotron can have an important impact on the accelerator, medical, and physics communities.

Poster MOPAB160 [0.424 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB160

About •

paper received ※ 15 May 2021 paper accepted ※ 24 June 2021 issue date ※ 13 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUXB07

High-Current H₂⁺ Beams from a Compact Cyclotron using RFQ Direct Injection

1301

D. Winklehner, J.M. Conrad, D. Koser, J. Smolsky, L.H. Waites
MIT, Cambridge, Massachusetts, USA

Funding: This work was supported by NSF grants PHY-1505858 and PHY-1626069.
For the IsoDAR neutrino experiment, we have developed a compact and cost-effective cyclotron-based driver to produce high current beams (cw proton beam currents of >10 mA at 60 MeV). This is a factor of 4 higher than the current state-of-the-art for cyclotrons and a factor of 10 compared to what is commercially available. All areas of physics that call for high cw currents can greatly benefit from this result; e.g. particle physics, medical isotope production, and energy research. This increase in beam current is possible in part because the cyclotron is designed to include and use vortex-motion, allowing clean extraction. Such a design process is only possible with the help of high-fidelity codes, like OPAL. Another novelty is the use of an RFQ embedded in the cyclotron yoke to bunch the beam during axial injection. Finally, using H²⁺ relieves some of the space charge constraints during injection. In this paper, we will give an overview of the project and then focus on the design and simulations of the cyclotron itself. We will describe the physics, computational tools, and simulation results. At the end, we will describe how we are including machine learning in the simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUXB07

About •

paper received ※ 27 May 2021 paper accepted ※ 22 July 2021 issue date ※ 31 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB195

Design and Optimization of a Low Frequency RF-Input Coupler for the IsoDAR RFQ

3081

M.P. Sangroula, J.M. Conrad, D. Winklehner
MIT, Cambridge, Massachusetts, USA
M. Schuett
BEVATECH, Frankfurt, Germany

Funding: The RFQ-DIP project is supported by National Science Foundation grant \# PHY-1626069 and the Heising-Simons Foundation.
The Isotope Decay-At-Rest experiment (IsoDAR) is a proposed underground experiment which is expected to be a definitive search for sterile neutrinos. IsoDAR uses an especially designed low-frequency spilt-coaxial radio frequency quadrupole (RFQ) to accelerate H²⁺ ions directly from the ion source into the main cyclotron accelerator. This paper mainly focuses on the design and optimization of a low frequency (32.8 MHz) RF-input coupler for the IsoDAR RFQ. Starting with a basic design, we determine its appropriate position for this coupler in the RFQ. Finally, we optimized the design to lower the input power without compromising the coupling efficiency.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB195

About •

paper received ※ 21 May 2021 paper accepted ※ 30 June 2021 issue date ※ 29 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB202

Thermal Analysis of a Compact Split-Coaxial CW RFQ for the IsoDAR RFQ-DIP

3097

D. Koser, J.M. Conrad, D. Winklehner
MIT, Cambridge, Massachusetts, USA
H. Podlech, U. Ratzinger, M. Schuett
BEVATECH, Frankfurt, Germany

The RFQ direct injection project (RFQ-DIP) for the neutrino physics experiment IsoDAR aims at an efficient injection of a high-current H²⁺ beam into the dedicated 60 MeV driver cyclotron. Therefore, it is intended to use a compact 32.8 MHz RFQ structure of the split-coaxial type as a pre-buncher. To determine the thermal elongation of the 1.4 m long electrode rods as well as the thermal frequency detuning of the RF structure at a maximum nominal power load of 3.6 kW, an extensive thermal and structural mechanical analysis using COMSOL Multiphysics was conducted. The water heating along the cooling channels as well as the properties of heat transfer from the copper structure to the cooling water were taken into account, which required CFD simulations of the cooling water flow in the turbulent regime. Here we present the methods and results of the sophisticated thermal and structural mechanical simulations using COMSOL and provide a comparison to more simplistic simulations conducted with CST Studio Suite.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB202

About •

paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 14 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB203

RFQ Beam Dynamics Optimization Using Machine Learning

3100

D. Koser, J.M. Conrad, L.H. Waites, D. Winklehner
MIT, Cambridge, Massachusetts, USA
A. Adelmann, M. Frey, S. Mayani
PSI, Villigen PSI, Switzerland

To efficiently inject a high-current H²⁺ beam into the 60 MeV driver cyclotron for the proposed IsoDAR project in neutrino physics, a novel direct-injection scheme is planned to be implemented using a compact radio-frequency quadrupole (RFQ) as a pre-buncher, being partially inserted into the cyclotron yoke. To optimize the RFQ beam dynamics design, machine learning approaches were investigated for creating a surrogate model of the RFQ. The required sample datasets are generated by standard beam dynamics simulation tools like PARMTEQM and RFQGen or more sophisticated PIC simulations. By reducing the computational complexity of multi-objective optimization problems, surrogate models allow to perform sensitivity studies and an optimization of the crucial RFQ beam output parameters like transmission and emittances. The time to solution might be reduced by up to several orders of magnitude. Here we discuss different methods of surrogate model creation (polynomial chaos expansion and neural networks) and identify present limitations of surrogate model accuracy.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB203

About •

paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 30 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB167

Technical Design of an RFQ Injector for the IsoDAR Cyclotron

4075

H. Höltermann, D. Koser, B. Koubek, H. Podlech, U. Ratzinger, M. Schuett, M. Syha
BEVATECH, Frankfurt, Germany
J.M. Conrad, J. Smolsky, L.H. Waites, D. Winklehner
MIT, Cambridge, Massachusetts, USA

For the IsoDAR (Isotope Decay-At-Rest) experiment, a high intensity (10 mA CW) primary proton beam is needed. To generate this beam, H²⁺ is accelerated in a cyclotron and stripped into protons after extraction. An RFQ, partially embedded in the cyclotron yoke, will be used to bunch and axially inject H²⁺ ions into the main accelerator. The strong RFQ bunching capabilities will be used to optimize the overall injection efficiency. To keep the setup compact the distance between the ion source and RFQ can be kept very short as well. In this paper, we describe the technical design of the RFQ. We focus on two critical aspects: 1. The use of a split-coaxial structure, necessitated by the low frequency of 32.8 MHz (matching the cyclotron RF) and the desired small tank diameter; 2. The high current, CW operation, requiring a good cooling concept for the RFQ tank and vanes.

Poster THPAB167 [2.162 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB167

About •

paper received ※ 14 May 2021 paper accepted ※ 27 July 2021 issue date ※ 21 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)