[Paper Review] KLASH Conceptual Design Report

D. Alesini, D. Babusci+27 more|arXiv (Cornell University)|Nov 6, 2019

Dark Matter and Cosmic Phenomena21 citations

TL;DR

KLASH proposes a large haloscope experiment at INFN Frascati using the decommissioned KLOE superconducting magnet (0.6 T) to search for axion dark matter in the 0.2–1 μeV mass range via microwave photon conversion in a high-Q cavity. The conceptual design demonstrates feasibility of achieving sensitivity to KSVZ axions with a 3M€ budget and 2–3 year timeline, leveraging existing infrastructure and advanced SQUID-based signal amplification for high-fidelity detection of weak axion-induced signals.

ABSTRACT

The last decade witnessed an increasing interest in axions and axion-like particles with many theoretical works published and many new experimental proposals that started a real race towards their discovery. This paper is the Conceptual Design Report of the KLASH (KLoe magnet for Axion SearcH) experiment at the Laboratori Nazionali di Frascati (LNF). The idea of this experiment has been stimulated by the availability of the large volume superconducting magnet, with a moderate magnetic field of 0.6 T, used in the KLOE detector at the DAFNE collider. The main conclusion we draw from this report is the possibility to build and put in operation at LNF in 2-3 years a large haloscope with the sensitivity to KSVZ axions in the low mass range between 0.2 and 1 $μ$eV, complementary to that of other experiments. Timeline and cost are competitive with respect to other proposals in the same mass region thanks to the availability of most of the infrastructure, in particular the superconducting magnet and the cryogenics plant.

Motivation & Objective

• To design a large-volume haloscope experiment capable of detecting axion dark matter in the 0.2–1 μeV mass window using existing superconducting magnet infrastructure.
• To leverage the KLOE magnet’s 0.6 T field and stable cryostat environment to minimize construction costs and accelerate deployment.
• To achieve sensitivity to KSVZ axions comparable to or better than other experiments in the same mass range, with a focus on low-mass axion detection.
• To develop a robust signal amplification chain using microstrip SQUID amplifiers and implement a multi-stage data analysis strategy to suppress noise and false positives.
• To define a scalable data acquisition and computing pipeline capable of handling ~1100 TB of raw spectral data over 230,000 frequency steps.

Proposed method

• Utilizes the KLOE superconducting magnet (0.6 T, 1.3 m bore, 3.8 m length) as the core magnetic field source for axion-to-photon conversion in a high-Q microwave cavity.
• Employs detailed electromagnetic simulations using Ansys-HFSS to optimize cavity geometry and resonance frequency for maximum coupling to axion-induced photons.
• Deploys a cryogenic system with a 4.2 K bath and 1.5 K stage to maintain superconducting conditions and minimize thermal noise in the cavity and amplifier.
• Integrates a microstrip SQUID amplifier as the first-stage signal preamplifier to achieve near-quantum-limited noise performance and enable detection of weak axion signals.
• Applies a two-phase data analysis strategy: initial scan with thresholding based on SNR and Gaussian statistics, followed by a rescan of candidate bins to confirm signal persistence.
• Implements online pre-processing using PC RAM and GPU-accelerated FFTs to manage data flow and reduce storage burden, with real-time filtering and spectrum averaging.

Experimental results

Research questions

• RQ1 Can a large haloscope be constructed using existing superconducting magnet infrastructure to achieve sensitivity to axions in the 0.2–1 μeV mass range?
• RQ2 What is the achievable sensitivity of the KLASH experiment to KSVZ axions, and how does it compare to other experiments in the same mass window?
• RQ3 How can signal amplification and data analysis be optimized to detect weak, persistent axion signals while suppressing thermal and electromagnetic noise?
• RQ4 What are the computational and storage requirements for a full-scan haloscope experiment with 230,000 frequency steps and 10^10 spectra?
• RQ5 Is the use of the KLOE magnet viable after its decommissioning, and what are the mechanical and operational challenges of repurposing it for axion detection?

Key findings

• The KLASH experiment is feasible with a total cost of approximately 3 M€ and a deployment timeline of 2–3 years, leveraging existing infrastructure including the KLOE magnet and cryogenics plant.
• The conceptual design achieves sensitivity to KSVZ axions in the 0.2–1 μeV mass range, with projected limits competitive with other experiments in the same region.
• Simulations with Ansys-HFSS confirm that a high-Q cavity can be designed with Q-factors > 10^6, enabling efficient axion-to-photon conversion at the target frequency band.
• The microstrip SQUID amplifier achieves near-quantum-limited noise temperature (~100 mK), crucial for detecting sub-nanowatt-level axion signals.
• The data acquisition system is projected to generate ~1100 TB of raw data over 230,000 frequency steps, with online pre-processing using GPU-accelerated FFTs to reduce storage and processing load.
• The two-stage analysis (initial scan + rescan of candidates) reduces false positives by requiring signal persistence across multiple scans, with statistical thresholds derived from the Dicke equation and Gaussian statistics.