Design and Implementation of the ABRACADABRA-10 cm Axion Dark Matter Search

The past few years have seen a renewed interest in the search for light particle dark matter. ABRACADABRA is a new experimental program to search for axion dark matter over a broad range of masses, $10^{-12}\lesssim m_a\lesssim10^{-6}$ eV. ABRACADABRA-10 cm is a small-scale prototype for a future detector that could be sensitive to QCD axion couplings. In this paper, we present the details of the design, construction, and data analysis for the first axion dark matter search with the ABRACADABRA-10 cm detector. We include a detailed discussion of the statistical techniques used to extract the limit from the first result with an emphasis on creating a robust statistical footing for interpreting those limits.Comment: 12 pages, 8 figure

A Ioffe Trap Magnet for the Project 8 Atom Trapping Demonstrator

The goal of the Project 8 experiment (B. Monreal and J. Formaggio, 2009) is to measure the absolute neutrino mass using tritium, which involves precisely measuring the energies of the beta-decay electrons in the high-energy tail of the spectrum (A. A. Esfahani et al., 2017). The experimental installation of Project 8 Atom Trapping Demonstrator requires a magnet with rather unusual field properties. The magnet has to contain within the cold mass a large volume enclosed by a continuous, uninterrupted boundary higher than 2 T, whereas the field in a substantial volume inside this boundary has to be of the order of 10 -4 T or less. A 1-T solenoid field provides the background field necessary for the detection of the beta-decay electrons (A. A. Esfahani et al., 2019). A proposed toroidal magnet system [a Ioffe-Pritchard trap (T. Bergeman et al., 1987)] comprised of specially shaped multiple racetrack windings with opposing polarities satisfies these unusual requirements. The magnet is made of NbTi wire and expected to be conduction cooled. Manufacturability issues are addressed as well as the effect of tolerances on the field quality. The design includes additional topological features providing a low-field duct for interfacing with the peripheral coils of the velocity and state selector

Compact, Low-Cost, Light-Weight, Superconducting, Ironless Cyclotrons for Hadron Radiotherapy

Superconducting cyclotrons are increasingly employed for proton beam radiotherapy treatment (PBRT). The use of superconductivity in a cyclotron design can reduce its mass by an order of magnitude and size by a factor of 3-4 over conventional resistive magnet technology, yielding significant reduction in overall cost of the device, the accelerator vault, and its infrastructure, as well as reduced operating costs. At MIT, previous work was focused on developing a very high field (9 T at the pole face) superconducting synchrocyclotron that resulted in a highly compact device that is about an order of magnitude lighter, and much smaller in diameter than a conventional, resistive cyclotron. The results of the study reported here were focused on a conceptual design for a compact superconducting synchrocyclotron to demonstrate the possibility to further reduce its weight by almost another order of magnitude by eliminating all iron from the device. In the absence of magnetic iron poles, the magnetic field profile in the beam gap is achieved through a set of main superconducting split pair coils energized in series with a set of distributed field-shaping superconducting coils. External magnetic field shielding is achieved through a set of outer, superconducting ring coils, also connected in series with the other coils, to cancel the stray magnetic field. These shielding coils replace the heavy iron yoke which is the conventional method to return the magnetic flux. It is noted that the 10 Gauss surface is located at a radius of about 3.5 m comparable in both ironless and conventional devices, even in the absence of iron in the ironless device. An important result from eliminating all magnetic iron in the flux circuit is the resulting linear relationship between the operating current and the magnetic field intensity. In the case with iron, the saturation of the magnetic field forces operation at one value of magnetic field. This feature design then enables continuous beam energy variation without the use of an energy degrader, thus eliminating secondary radiation during the in-depth beam scanning, increasing the ion current delivered to the patient and improving the beam quality. The beam energy is determined by the magnetic field strength at the extraction radius, and changing the field enables selection of the final beam energy. The magnetic field can be adjusted while maintaining the needed radial field profile

ABRACADABRA, A Search for Low-Mass Axion Dark Matter

ABRACADABRA is a proposed experiment to search for ultralight ($10^{-14} - 10^{-6}\mathrm{eV}$) axion dark matter. When ultralight axion dark matter encounters a static magnetic field, it sources an effective electric current that follows the magnetic field lines and oscillates at the axion Compton frequency. In the presence of axion dark matter, a large toroidal magnet will act like an oscillating current ring, whose induced magnetic flux can be measured by an external pickup loop inductively coupled to a SQUID magnetometer. Both broadband and resonant readout circuits are considered. ABRACADABRA is fielding a 10-cm prototype in 2017 with the intention of scaling to a 1 m$^3$ experiment. The long term goal is to probe QCD axions at the GUT-scale

First Results from ABRACADABRA-10 cm: A Search for Sub-μeV Axion Dark Matter

The axion is a promising dark matter candidate, which was originally proposed to solve the strong-CP problem in particle physics. To date, the available parameter space for axion and axionlike particle dark matter is relatively unexplored, particularly at masses m_{a}≲1  μeV. ABRACADABRA is a new experimental program to search for axion dark matter over a broad range of masses, 10^{-12}≲m_{a}≲10^{-6}  eV. ABRACADABRA-10 cm is a small-scale prototype for a future detector that could be sensitive to the QCD axion. In this Letter, we present the first results from a 1 month search for axions with ABRACADABRA-10 cm. We find no evidence for axionlike cosmic dark matter and set 95% C.L. upper limits on the axion-photon coupling between g_{aγγ}<1.4×10^{-10} and g_{aγγ}<3.3×10^{-9}  GeV^{-1} over the mass range 3.1×10^{-10}–8.3×10^{-9}  eV. These results are competitive with the most stringent astrophysical constraints in this mass range

VIPER: an industrially scalable high-current high-temperature superconductor cable

High-temperature superconductors (HTS) promise to revolutionize high-power applications like wind generators, DC power cables, particle accelerators, and fusion energy devices. A practical HTS cable must not degrade under severe mechanical, electrical, and thermal conditions; have simple, low-resistance, and manufacturable electrical joints; high thermal stability; and rapid detection of thermal runaway quench events. We have designed and experimentally qualified a vacuum pressure impregnated, insulated, partially transposed, extruded, and roll-formed (VIPER) cable that simultaneously satisfies all of these requirements for the first time. VIPER cable critical currents are stable over thousands of mechanical cycles at extreme electromechanical force levels, multiple cryogenic thermal cycles, and dozens of quench-like transient events. Electrical joints between VIPER cables are simple, robust, and demountable. Two independent, integrated fiber-optic quench detectors outperform standard quench detection approaches. VIPER cable represents a key milestone in next-step energy generation and transmission technologies and in the maturity of HTS as a technology