The front-end of IsoDAR

The Isotope Decay-At-Rest (IsoDAR) experiment is a cyclotron based neutrino oscillation exper- iment that is capable of decisively searching for low-mass sterile neutrinos. This paper outlines two new approaches that the IsoDAR collaboration are pursuing in order to increase the amount of H + 2 captured in the cyclotron through innovations in the design of the front-end. A new dedicated multicusp ion source (MIST-1) is currently being commissioned and tested at the Plasma Science and Fusion Center (PSFC) at MIT. Based on previous results from this type of ion source, we ex- pect to be able to achieve an H+₂ current density that will be sufficient for the IsoDAR experiment. We also discuss the results of a new investigation into using a radio frequency quadrupole (RFQ) as a high-efficiency buncher to improve the injection efficiency into the cyclotron.National Science Foundation (U.S.) (Grant 1505858)National Science Foundation (U.S.) (Grant 1626069

Input beam matching and beam dynamics design optimizations of the IsoDAR RFQ using statistical and machine learning techniques

This work was supported by NSF grants PHY-1505858 and PHY-1626069 and funding from the Bose Foundation and the Heising-Simons Foundation.We present a novel machine learning-based approach to generate fast-executing virtual radiofrequency quadrupole (RFQ) particle accelerators using surrogate modelling. These could potentially be used as on-line feedback tools during beam commissioning and operation, and to optimize the RFQ beam dynamics design prior to construction. Since surrogate models execute orders of magnitude faster than corresponding physics beam dynamics simulations using standard tools like PARMTEQM and RFQGen, the computational complexity of the multi-objective optimization problem reduces significantly. Ultimately, this presents a computationally inexpensive and time efficient method to perform sensitivity studies and an optimization of the crucial RFQ beam output parameters like transmission and emittances. Two different methods of surrogate model creation (polynomial chaos expansion and neural networks) are discussed and the achieved model accuracy is evaluated for different study cases with gradually increasing complexity, ranging from a simple FODO cell example to the full RFQ optimization. We find that variations of the beam input Twiss parameters can be reproduced well. The prediction of the beam with respect to hardware changes, e.g., the electrode modulation, are challenging on the other hand. We discuss possible reasons for that and elucidate nevertheless existing benefits of the applied method to RFQ beam dynamics design.Publisher PDFPeer reviewe

AN RFQ DIRECT INJECTION SCHEME FOR THE ISODAR HIGH INTENSITY H+₂ CYCLOTRON

IsoDAR is a novel experiment designed to measure neutrino oscillations through e disappearance, thus providing a definitive search for sterile neutrinos. In order to generate the necessary anti-neutrino flux, a high intensity primary proton beam is needed. In IsoDAR, H+2 is accelerated and is stripped into protons just before the target, to overcome space charge issues at injection. As part of the design, we have refined an old proposal to use an RFQ to axially inject bunched H+2 ions into the driver cyclotron. This method has several advantages over a classical low energy beam transport (LEBT) design: (1) The bunching efficiency is higher than for the previously considered two-gap buncher and thus the overall injection efficiency is higher. This relaxes the constraints on the H+2 current required from the ion source. (2) The overall length of the LEBT can be reduced. (3) The RFQ can also accelerate the ions. This enables the ion source platform high voltage to be reduced from 70 kV to 30 kV, making underground installation easier. We are presenting the preliminary RFQ design parameters and first beam dynamics simulations from the ion source to the spiral inflector entrance.National Science Foundation (U.S.). Division of Physics (NSF-PHY-1148134)MIT Energy Initiative Seed Fund Progra

Automated tube potential selection for standard chest and abdominal CT in follow-up patients with testicular cancer: comparison with fixed tube potential

Objective: To evaluate prospectively, in patients with testicular cancer, the radiation dose-saving potential and image quality of contrast-enhanced chest and abdominal CT with automated tube potential selection. Methods: Forty consecutive patients with testicular cancer underwent contrast-enhanced arterio-venous chest and portal-venous abdominal CT with automated tube potential selection (protocol B; tube potential 80-140kVp), which is based on the attenuation of the CT topogram. All had a first CT at 120kVp (protocol A) using the same 64-section CT machine and similar settings. Image quality was assessed; dose information (CTDIvol) was noted. Results: Image noise and attenuation in the liver and spleen were significantly higher for protocol B (P < 0.05 each), whereas attenuation in the deltoid and erector spinae muscles was similar. In protocol B, tube potential was reduced to 100kVp in 18 chest and 33 abdominal examinations, and to 80kVp in 5 abdominal CT examinations; it increased to 140kVp in one patient. Image quality of examinations using both CT protocols was rated as diagnostic. CTDIvol was significantly lower for protocol B compared to protocol A (reduction by 12%, P < 0.01). Conclusion: In patients with testicular cancer, radiation dose of chest and abdominal CT can be reduced with automated tube potential selection, while image quality is preserve

Enabling a Multi-Purpose High-Energy Neutron Source Based on High-Current Compact Cyclotrons

The current and future need for high-energy neutrons has been a subject of increasing discussion and concern. Immediate applications for such an intense neutron source include medical isotope production, high-energy physics (HEP) research, and for materials development and to support qualification for fission reactors. Also, and of the utmost importance, is the need for such a source to inform critical gaps in our understanding of the transmutation materials science issues facing fusion power reactors. A 14 MeV fusion prototypical neutron source (FPNS) has been a critical, yet unresolved need of the fusion program for more than 40 years. Given the narrowing timeline for construction of pilot and fusion power plants the urgency and necessity of such a neutron source has become increasingly time sensitive. One possibility to address this need is a scaled-down version of IFMIF technology ("IFMIF-Lite"), operating at 125 mA with the beam and target technology leveraging technology developed under the IFMIF/EVEDA program. Within this white paper, a blueprint of necessary R&D to enable a transformational change in both the capital and operating cost of this IFMIF-Lite driver concept is presented. Enabling this transformation is the replacement of the historic RFQ/LINAC components with multiple compact 35+ MeV D+ drivers, based on compact cyclotrons