Micro –channel cooling systemsand optical fibre sensors

Micro- Channels

Micro-channels are used in multiple different experiments, notably NA62 and LHCb

Micro-channels can cool the very heart of detectors from very close due to their extremely small size.

Micro-channels are cooling units that are used to cool down detectors

They can be exploited not only with liquid, but also with evaporative cooling systems.

Why are micro-channels advantageous?

Fun mind-blowing facts-the channels are about the size of your hair! -They are extremely useful due to their small size, radiation and magnetic resistance, and their low material cost-it is going to be used on new detectors because of these advantageous properties: They are the same material as the

detectors( silicone) therefore they expand and contract with heat at the same rate as the detectors.

They are very thin , therefore they minimise the total mass of the detector, reducing bias in data.

They fit directly under the heat source, and better distribute the cooling, in contrast to cooling systems based on piping, where the cooling is distributed unevenly.

Optical Fibre sensors

Why we need cooling in detectors? What are the dangers of heat and humidity?

Optical fibre sensors are currently being used a lot in CMS and are being proposed for most other experiments at CERN .

Optical fibres are so thin that they are perfect for entering small areas in the detectors

Optical fibre sensors work by sending light through the fibre and a special grating inside the fibre called the Bragg grating. The shape of the grating varies depending on the temperature and pressure. Depending on it’s shape, a certain quantity of light is reflected back. This quantity varies depending on the heat and pressure applied to the sensors. To detect humidity, we coat the fibres in polyimide : a plastic that expands on contact with water molecules (humidity). This expansion causes pressure on the fibres, resulting in a stronger reflection of light.

Fun mind-blowing facts:-The optical fibres are approximately the size of your hair, even with a protective coating-They are relatively cheap because there can be several detectors on one fibre

Why are optical fibres

advantageous?

We need cooling to take out the heat produced by the detector, the electronics and the cables. We need it to maintain a neutral environment for the optimal functioning of the electronics. To guarantee a long detector lifetime. To avoid over heating and damage or malfunctioning of the detectors. We need the cooling to be cool ;)

Heat could potentially melt and ruin the electronics, detectors and the data produced or in other words 100 million Swiss francs of machinery and ten years of work… LOST.

Another danger which the wrong amount of heat could produce is the malfunctioning of most detectors which would cause a lot of damage or unreliability concerning the data, or even no data at all.

Humidity could produce short-circuits and bias the data, it could even destroy the experiments

2 Swiss

francs• 1 fiber optic array with

• 8 FBG-based hygrometers (MULTIPLEXING)

Heat sensor

Humidity sensor

-It is extremely effective compared to the old system because it can have multiple detectors on one fibre compared to the old system which used to have to include one wire for each detector. Also , fibre optic is faster than other electronic systems.

Lauren GillNicolas Olney-RainvilleAlistair whistlerMaxime Barbier stage d’observation 05/02/2015

With thanks to Paola Tropea, Karl Gill, Giulia Romagnoli, Gaia Maria Berruti, Anne Dabrowski, Archana Sharma