Hula Hoop

is the largest particle accelerator in the world which is situated inside Academy City. Chapter 1 Part 3
==Etymology==
A is a toy hoop which is spun around the waist, limbs or neck.
==Principles==
The giant ring-shaped particle accelerator follows the shape of the city's walls and is built 200m underground. Its control center is the same, situated near the outer edges of School District 23, which borders the outer walls. Chapter 1 Part 5
To prevent the Hula Hoop from releasing gamma rays in case of accidents, there are protection walls on the level of nuclear shelters built around it. According to the different stages in speed, Hula Hoop is split into first, second and third rings, and accelerates particles separately starting from the smallest one. From the configuration, the third ring cannot work at a low speed of 30% of the speed of light - it is something that can only be used in experiments that force particles to go over 70% of the speed of light. It is capable of accelerating protons to 99.22% of the speed of light, and maintain that speed for up to 300 seconds. Surpassing the speed it was designed to hold, or running it longer than it was supposed to would both lead to Hula Hoop’s explosion; Chapter 1 Part 6 that meant enough gamma radiation to cover a third of Academy City would be released.
The accelerator's operation involves billions of eVs, with a single electrical short involving enough energy to vaporize a sports stadium. As its operations involves atoms or protons colliding at more than 99% of the speed of light, if tunnel shielding were to be compromised while it is in use, there would be a major release of neutrons and radiation. As such, the Hula Hoop has thick lead shielding, capable of containing radiation from the accelerator's operation, as well as shielding its equipment from external radiation. The accelerator has strict safety features and takes the highest priority within the hierarchy of precedence for the wall facility systems. If its internal stability is damaged, all resources will be used to help its recovery, leading to a drop in wall security in the meantime. Chapter 1 Part 4
As well as requiring a large amount of electricity for its operation, the accelerator also requires a large amount of power for an emergency stop. As such, it has a back-up power generator in case the main generators fail.
The collisions of different particles in the accelerator can create a variety of phenomena, including the creation of new elements which don't exist in the natural world.
===Particle Accelerator Cannon===
During the events in January of the main story's second year, Board Chairman Accelerator had Hula Hoop modified to act as a particle accelerator cannon, intended as a trump card for use against Alice Anotherbible and later "Christian Rosencreutz".
Gathering the city's energy and accelerating electrons to over 99.99% the speed of light, Hula Hoop would fire an immensely powerful electron beam, intended to kill the target and also, in case it failed to do the job, discretely inject a massive amount of energy into Kazakiri Hyouka and Qliphah Puzzle 545 to boost their raw power. It would only be able to fire a single shot as it would push it past its power limits, frying its forcibly-linked capacitors and transformers.
The electron beam was capable of bisecting the city in a single line from north to south, with the absorption by the two energy beings preventing it from piercing the outer wall and continuing on to and . In its line-of-fire, even without directly hitting, the beam vaporized all moisture in the air, melted asphalt to a boiling orange liquid, blew up abandoned small aircraft and burned apart an armored combat vehicle, half-vaporizing it. In the wake of the beam, which was bright enough to blind, the air was electrified and sparking, suggesting that even the elements making it up may have been rewritten.
===Meltdowner Research Lab===
Prior to its shutdown in August one year before the main story, the School District 14 portion of Hula Hoop hosted the research lab for Meltdowner. Chapter 3 Part 2 Epilogue It was housed in a large building with a futuristic design resembling an airport terminal and vast grounds surrounded by a tall wall. Chapter 3 Part 4 Chapter 3 Part 11 It had secret priority access to the accelerator, which reverted to the District 22 control center after its shutdown.
As well as developing Mugino Shizuri's Level 5 esper ability with unique, specially-made equipment, the lab was also the site for , which aimed to develop a set of the perfect and electric scalpel for industrial-scale genetic manipulation and esper designing. Chapter 3 Part 9
The lab's former head researcher was Ainame Caroline, who was fired around half a year prior to the lab's shutdown. Chapter 1 Part 6 Chapter 3 Part 6 Progress at the lab stalled after her departure, a factor in the lab's closure after her death. Chapter 4 Part 4
The lab was protected by a laser weapon, which utilized the windows of nearby skyscrapers (the glass sprayed with a special coating without permission) as mirrors to bend the beam, a repurposed system known as , and a microwave-based EM weapon. Chapter 3 Part 3
==Chronology==
===Toaru Majutsu no Index===
====DRAGON Arc====
Spark Signal, having revolted against Academy City, carefully made a plan that included the seizing of Hula Hoop on October 17th and put into it the majority of their efforts and resources; the demand that they made to Academy City was "disclose all of the information you possess about DRAGON". Chapter 1 Part 9 Before Spark Signal's attack on Hula Hoop, they kidnapped around 30 primary school students on an astronomy field trip, along with their teacher and driver as a ‘bargaining chip’; while threatening to detonate Hula Hoop, which would have released enough gamma radiation to cover a third of the city.
The higher ups wanted to eliminate them and end the threat, dispatching to do so. used an elevator in School District 23 to gain entry to it where they waited ten minutes to strengthen the signal from the Misaka Network to Accelerator's collar. He then effortlessly eliminated Spark Signal in 300 seconds while also saving the first hostage set to be executed. Chapter 1 Part 7
===Shinyaku Toaru Majutsu no Index===
====Aleister Crowley Arc====
On December 11th, the Hula Hoop was still operational, having being protected by its shielding from the recent heat wave. During his attempt to escape the city with his sister and Karasuma Fran, Tsuchimikado Motoharu attempted to take advantage of the particle accelerator's precedence in the wall facility's hierarchy which prioritized its recovery over maintaining the wall's security. He damaged the power cable connecting the wall and the underground using a drill and , intending to use the five minute reduction in security to climb over the wall, however Tsuchimikado Maika was struck by Aleister's curse magic sword at the wall, forcing them to change their plans. Chapter 1 Part 5
===Souyaku Toaru Majutsu no Index===
====New Year's Arc====
Following the Bridge Builders Cabal establishing a consulate inside Academy City, Accelerator had the Hula Hoop prepared to launch an immensely powerful electron beam as a trump card to kill their leader Alice Anotherbible if necessary. Chapter 3 Part 6 Following the emergence of CRC and his destructive march across the city, it was instead turned against him. With Accelerator having cleared people from the predicted line of fire via the city via cleaning and security robots, Chapter 2 Part 6 Chapter 3 Part 1 and the city's attacks at the School District 23 defensive line having momentarily kept CRC still, Chapter 3 Part 5 the particle accelerator cannon fired its single shot, which bisected the city from School District 3 in the north to School District 10 in the south.
Having been pushed past its limits, firing electrons at over 99.99% the speed of light with all of the city's power, the Hula Hoop's capacitators and transformers overloaded and blew up. Despite being hit directly by the beam, which caused considerable damage in its wake (though no human damage), CRC was seemingly undamaged. However, the beam achieved its secondary objective of secretly injecting Kazakiri Hyouka and Qliphah Puzzle 545 with a massive amount of energy to boost their strength, which they would later use to support Kamijou Touma in the final battle with CRC, preserving his life and strength when he was bleeding out during his self-destructive use of the dragon behind Imagine Breaker. Chapter 4 Part 7
==Trivia==
*Given that Academy City is around 1/3rd the size of Tokyo, the city's circumference, and thus the length of the wall and the accelerator by extension, can be calculated as around 95km. This is three and a half times longer than the , although its proposed successor, the would be just as long.
==References==
Category:Locations
Category:Academy City Locations
Category:Science
Category:Academy City Technology