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 will likely be to observe circumstances 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 some of the 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 review 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 dark matter detectors like DEAP 3600, ARDM, MiniCLEAN and DarkSide-50.
Liquid argon has many perks. It’s dense, which will increase the possibility that notoriously aloof neutrinos will work together. It’s inert, so electrons knocked free by a neutrino interplay could be recorded to create a 3D image of the particle’s trajectory. It’s clear, so researchers may also acquire gentle 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 will not be with out their challenges. To provide high quality information, the liquid argon have to be stored extraordinarily chilly and very pure. Meaning the detectors have to be remoted from the skin world to maintain the argon from evaporating or turning into contaminated. With entry restricted, diagnosing or addressing points inside a detector could 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 generally is way simpler than decoding information 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 thought for Argonaut got here when Fermilab engineer Invoice Pellico puzzled if it could be attainable to make the inside cameras movable. A robotic digital camera could sound easy — however engineering it for a liquid-argon surroundings presents distinctive challenges.
All the 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 turning into brittle and falling aside. Any transferring items should transfer easily with out grease, which might contaminate the detector.
“You may’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 obtained funding for Argonaut by means of the Laboratory Directed Analysis and Improvement program, an initiative established to foster progressive scientific and engineering analysis at Division of Vitality nationwide laboratories. At this early stage of the challenge, the group — Pellico, mechanical engineers Noah Curfman and Mayling Wong-Squires, and neutrino scientist Flavio Cavanna — is targeted on evaluating parts and fundamental design points. The primary purpose is to show that it’s attainable to speak with, energy and transfer a robotic in a cryogenic surroundings.
“We wish to show that we will have, at a naked minimal, a digital camera 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 could final for the lifetime of the detector,” mentioned Curfman.
The plan is to energy Argonaut by means of 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 skin world.
The motor that may transfer Argonaut alongside a monitor on the aspect of the detector will likely be located exterior of the chilly surroundings. The digital camera will likely 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 may embody 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 will likely 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, and so they should function at cryogenic temperatures,” Pellico mentioned. The Argonaut group 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 energetic interstellar house probes corresponding to Voyagers 1 and a couple 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 achieved it; we’ve by no means achieved it; no one’s ever achieved it, so far as I can inform.”