IN THE PRESS


IAC3 Researchers Return from a Fruitful Stay at LIGO Livingston

24 January, 2025

TJ O'Hanlon on the left, a LIGO engineer, Rafel Jaume on the right, and Joan-René Mérou in front of the Horizontal Access Module 6 (HAM6), where the two photoreceptors are located to read interference patterns.

On December 21, 2024, researchers Rafel Jaume Amengual and Joan-René Mérou Mestre, of the Institute of Applied Computing and Community Code (IAC3) at the University of the Balearic Islands (UIB), returned from a three-month research stay at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Livingston, Louisiana, USA. Their stay was part of their PhD program as members of the LIGO Scientific Collaboration (LSC) as part of the LIGO Fellow program, focused on detector characterization tasks to enhance the observatory's sensitivity to gravitational waves.

What are gravitational waves?

Gravitational waves are ripples in spacetime that travel at the speed of light, caused by accelerating objects. Predicted by Albert Einstein’s general theory of relativity in 1915, these waves propagate outward from events like merging black holes, neutron star collisions, or other highly energetic cosmic phenomena. These ripples carry information about the cataclysmic events that created them, offering a new way to study the universe.

However, detecting these waves is incredibly challenging due to their very small effects. They cause distortions on the scale of one ten-thousandth the diameter of a proton. To detect these tiny distortions, scientists have developed highly sensitive instruments like LIGO, which use advanced laser interferometry.

How does LIGO work?

Rafel Jaume on one of the arms of the LIGO Livingston detector.

LIGO operates two observatories in Hanford, Washington, and Livingston, Louisiana. Each facility houses a massive interferometer with two perpendicular arms, each 4 kilometers long. A laser beam is split in two and travels down each arm, reflecting off mirrors and recombining at a photodetector.

When a gravitational wave passes through, it stretches and compresses the arms slightly, creating a shift in the laser beams’ phase and producing measurable interference patterns. This change, though extraordinarily small, is detectable by LIGO's sensitive instruments.

To achieve such precision, LIGO must operate in an environment free from noise. This includes not only seismic vibrations but also other sources of noise, such as electrical interference, temperature fluctuations, and even the effects of human activity. Ensuring the quality of LIGO’s data is the primary goal of the Detector Characterization team, to which Rafel Jaume Amengual and Joan-René Mérou Mestre contributed.

The role of detector characterization

Rafel Jaume on the left, TJ O'Hanlon in the background, and Joan-René Mérou on the right at the new beam splitter of the detector.

Gravitational-wave detectors are incredibly sensitive, which means they are also susceptible to a wide variety of noise sources. The Detector Characterization team plays a vital role in identifying and mitigating these noise sources. Their work ensures that data collected by LIGO is accurate and free from artifacts that could mimic or obscure gravitational-wave signals. Detector characterization focuses on three main areas:

Contributions by Rafel Jaume Amengual and Joan-René Mérou Mestre

During their three-month research stay at LIGO Livingston, both Rafel Jaume Amengual and Joan-René Mérou Mestre worked closely with Dr. Anamaria Effler and the site staff as part of the Detector Characterization team. Their work focused on improving the detector’s sensitivity, identifying and mitigating noise sources, and contributing to real-time follow-ups of gravitational-wave candidate events during the fourth observing run (O4). Each researcher undertook distinct projects that advanced LIGO’s capabilities.

Rafel Jaume Amengual's work

Rafel Jaume working on the Analog-to-Digital Converters (ADCs).

Rafel’s efforts focused on improving LIGO’s data acquisition systems, particularly the Analog-to-Digital Converters (ADCs). These devices are responsible for converting the analog signals from LIGO's sensors into digital data for analysis. His contributions included:

In addition to these tasks, Rafel collaborated on noise investigations and contributed to analyzing data quality during candidate gravitational-wave events. He also participated in gravitational-wave candidate Rapid Response Team (RRT Level 0) shifts, supporting real-time validation of gravitational-wave candidates and analyzing noise events.

Joan-René Mérou Mestre's work

Joan-René Mérou in the control room of the LIGO Livingston detector.

Joan-René focused on identifying and mitigating noise issues that had been challenging detector scientists for months. He also contributed to rapid follow-ups of gravitational-wave candidate events detected during the fourth observing run (O4). His contributions included:

In addition, Joan-René participated in gravitational-wave candidate Rapid Response Team (RRT Level 0) shifts, supporting real-time validation of two gravitational-wave detections: 241113p and 241116cq, two coalescences of binary black hole systems. Following the validation of the gravitational-wave candidates, Joan-René sent circulars to the wider worldwide scientific community through NASA's General Coordinates Network.

Why their work matters

Joan-René Mérou and Rafel Jaume at the entrance of the LIGO Livingston detector.

Both researchers contributed to advancing LIGO’s capabilities during its fourth observing run (O4). The insights and tools they developed will be useful for current and future gravitational-wave detections. By addressing specific noise issues and enhancing the quality of the detector's data, they have ensured more reliable astrophysical observations.

Their work exemplifies the importance of collaborative international research in fields like gravitational-wave astronomy. The advancements made during their stay not only improve LIGO’s performance but also pave the way for new discoveries about the universe.