The Argonauts of Greek mythology braved sharp rocks, tough seas, magic, and monsters to search out the fabled Golden Fleece. A brand new robotics challenge on the Division of Vitality’s Fermi Nationwide Accelerator Laboratory will share that very same identify and spirit of journey.
Argonaut’s mission can be to observe situations inside ultracold particle detectors by voyaging right into a sea of liquid argon stored at minus-193 levels Celsius — as chilly as a number of the moons of Saturn and Jupiter. The challenge, funded in March, goals to create probably the most cold-tolerant robots ever made, with potential purposes not solely in particle physics but additionally deep house exploration.
Argon, a component generally discovered within the air round us, has turn out to be a key ingredient in scientists’ quests to higher perceive our universe. In its liquid type, argon is used to check particles known as neutrinos in a number of Fermilab experiments, together with MicroBooNE, ICARUS, SBND and the next-generation worldwide Deep Underground Neutrino Experiment. Liquid argon can be utilized in darkish matter detectors like DEAP 3600, ARDM, MiniCLEAN and DarkSide-50.
Liquid argon has many perks. It’s dense, which will increase the prospect that notoriously aloof neutrinos will work together. It’s inert, so electrons knocked free by a neutrino interplay may be recorded to create a 3D image of the particle’s trajectory. It’s clear, so researchers may acquire mild to “time stamp” the interplay. It’s additionally comparatively low cost — an enormous plus, since DUNE will use 70,000 tons of the stuff.
However liquid-argon detectors aren’t with out their challenges. To provide high quality knowledge, the liquid argon have to be stored extraordinarily chilly and intensely pure. Meaning the detectors have to be remoted from the surface world to maintain the argon from evaporating or changing into contaminated. With entry restricted, diagnosing or addressing points inside a detector may be tough. Some liquid-argon detectors, such because the ProtoDUNE detectors at CERN, have cameras mounted inside to search for points like bubbles or sparks.
“Seeing stuff with our personal eyes typically is far simpler than deciphering knowledge from a sensor,” mentioned Jen Raaf, a Fermilab physicist who works on liquid-argon detectors for a number of tasks together with MicroBooNE, LArIAT and DUNE.
The concept for Argonaut got here when Fermilab engineer Invoice Pellico puzzled if it might be potential to make the inside cameras movable. A robotic digicam might sound easy — however engineering it for a liquid-argon surroundings presents distinctive challenges.
The entire electronics have to have the ability to function in a particularly chilly, high-voltage surroundings. All of the supplies have to face up to the cooling from room to cryogenic temperatures with out contracting an excessive amount of or changing into brittle and falling aside. Any transferring items should transfer easily with out grease, which might contaminate the detector.
“You possibly can’t have one thing that goes down and breaks and falls off and shorts out one thing or contaminates the liquid argon, or places noise into the system,” Pellico mentioned.
Pellico acquired funding for Argonaut via the Laboratory Directed Analysis and Improvement program, an initiative established to foster revolutionary scientific and engineering analysis at Division of Vitality nationwide laboratories. At this early stage of the challenge, the crew — Pellico, mechanical engineers Noah Curfman and Mayling Wong-Squires, and neutrino scientist Flavio Cavanna — is concentrated on evaluating parts and fundamental design features. The primary purpose is to show that it’s potential to speak with, energy and transfer a robotic in a cryogenic surroundings.
“We need to show that we are able to have, at a naked minimal, a digicam that may transfer round and pan and tilt in liquid argon, with out contaminating the liquid argon or inflicting any bubbles, with a reliability that exhibits that it might final for the lifetime of the detector,” mentioned Curfman.
The plan is to energy Argonaut via a fiber-optic cable in order to not intervene with the detector electronics. The fist-sized robotic will solely get about 5 to 10 watts of energy to maneuver and talk with the surface world.
The motor that can transfer Argonaut alongside a observe on the facet of the detector can be located outdoors of the chilly surroundings. The digicam can be contained in the chilly liquid and transfer very slowly; however that’s not a nasty factor — going too quick would create undesirable disturbances within the argon.
“As we get extra superior, we’ll begin including extra levels of freedom and extra rails,” mentioned Curfman.
Different future upgrades to Argonaut might embrace a temperature probe or voltage monitor, movable mirrors and lasers for calibrating the sunshine detectors, and even extendable arms with instruments for minor electronics restore.
A lot of the expertise Argonaut is advancing can be broadly relevant for different cryogenic environments — together with house exploration. The challenge has already garnered some curiosity from universities and NASA engineers.
Deep house robots “are going to go to distant places the place they’ve little or no energy, and the lifetime needs to be 20-plus years identical to in our detectors, they usually should function at cryogenic temperatures,” Pellico mentioned. The Argonaut crew can construct on current robotics know-how together with Fermilab’s experience in cryogenic methods to push the boundaries of chilly robotics.
Even the exteriors of lively interstellar house probes resembling Voyagers 1 and a pair of don’t attain temperatures as little as liquid argon — they use thermoelectric heaters to maintain their thrusters and science devices heat sufficient to function.
“There’s by no means been a robotic system that operated at these temperatures,” mentioned Pellico. “NASA’s by no means carried out it; we’ve by no means carried out it; no person’s ever carried out it, so far as I can inform.”