Radiation Impact on Tile Calorimeter During LHC Run 2

The ATLAS experiment at the Large Hadron Collider (LHC) is a large particle physics experiment designed to explore a variety of fundamental questions about the universe. One crucial component of this experiment is the Tile Calorimeter (TileCal), which measures the energy of particles like hadrons. As these particles interact with the detector, they can lead to some wear and tear, especially from Radiation. This article covers a study of how the optical instrumentation of the TileCal withstood radiation during LHC Run 2, from 2015 to 2018.

#What is the Tile Calorimeter?

The Tile Calorimeter is the central piece that measures the energy of particles produced in collisions at the LHC. It consists of several layers of plastic scintillators and steel that work together to absorb the energy from incoming particles. When a particle hits the scintillator, it produces a flash of light, which is then collected by special Optical Fibers and sent to photodetectors for measurement.

Imagine it as a high-tech "diner" where each particle is a customer, and the scintillator tiles are the waiters who serve light instead of food. Each waiter collects tips (light signals) based on how well they do their job.

#Optical Components at Risk

As you might guess, working with high-energy collisions means the TileCal faces a lot of radiation. The scintillators and optical fibers can suffer damage when exposed to this radiation over time. The study explored how these components held up under the harsh conditions of the LHC.

The optical fibers, responsible for gathering light from the scintillators, are a bit like partygoers who absorb the best stories from lively conversations. If the party lasts too long, they might start forgetting the good parts.

#Calibration and Monitoring

To keep track of how well the TileCal is functioning, various calibration and monitoring systems are in place. These include:

• Caesium radioactive sources: These provide consistent light for calibration checks.
• Laser systems: These help monitor the response of the detectors.
• Minimum bias events: These are random-scale events that help gauge overall performance.

Think of these systems as regular check-ins at the diner to ensure all the waiters are still delivering food correctly. If a waiter starts slacking off, the management needs to know!

#Data Collection

The data for this study came from the Run 2 period, which spanned from 2015 to 2018. Measurements taken during this time aimed to evaluate how the light output from the optical components changed as a result of radiation exposure.

The measurements revealed that the more time the tiles spent under radiation, the more their light output began to flicker, much like the dimming lights of a diner as the night wears on.

#Results of the Study

The TileCal's performance varied across its layers. The innermost A-layer was hit hardest by radiation, ending Run 2 with a loss of about 10% in light output. Other layers suffered much less damage, often remaining within 1% of their original performance.

It turns out that the A-layer was almost begging for a break after a long night of serving energy! Meanwhile, the other layers managed to keep up their game.

#Gap and Crack Scintillators

In addition to the regular segments, there are special gap and crack scintillators, which faced even tougher conditions. The gap scintillators showed about a 12% light output loss, but the crack counters were the real drama queens, suffering losses of 20% and 30% for their respective types.

The diner’s breakroom was clearly a chaotic place, and these counters were asking for a serious makeover going into Run 3.

#Minimum Bias Trigger Scintillators

The Minimum Bias Trigger Scintillators (MBTS), which help with triggering and timing events, faced significant wear. The inner counters in this system nearly lost 90% of their light response after accumulating a particularly hefty dose of radiation during Run 2.

As if that wasn't enough, they were replaced for Run 3 since they had seen better days, much like an overworked chef in a bustling diner.

#Radiation Environment

The radiation environment at the LHC is influenced by high-energy collisions that create an array of secondary particles. About 50% of these particles are produced in the area where the TileCal operates, though they only contribute about 1% of the total collision energy.

Imagine a busy street corner where everyone is chatting, but only a few conversations are loud enough to be heard.

Simulations were used to estimate the total ionizing dose (TID) experienced by the scintillator materials, revealing that certain areas received a much higher dose than others.

#Degradation Models

With the collected data, researchers created models to understand how the optical components would degrade over time under radiation. These models allowed them to extrapolate future performance, preparing for a more intense environment expected in future runs.

It's like forecasting how busy the diner will be over the summer based on last year’s patronage.

#Future Projections

The High Luminosity Phase of the LHC is expected to deliver even more radiation, with a projected increase in the instantaneous luminosity by a factor of seven. This means that the TileCal will need to be on its best behavior or risk facing serious degradation.

The future "dining" conditions look intense, and the waiters must be ready for the rush!

#Conclusion

In summary, the study of the Tile Calorimeter’s optical instrumentation during the LHC Run 2 provided valuable insights into how radiation impacts the performance of these critical components. The data collected and the models developed will help ensure that the TileCal remains robust, even as it faces new challenges in the High Luminosity Phase.

As the diner prepares for its next big round of service, the kitchen must be stocked with the best materials to ensure every customer leaves happy, even if that means some shiny new waiters and a few upgraded menus!