Students Work Electron Calibration for Collaborative aCORN Project
By Patrick Bedard '14
Contact: Holly Foster 315-859-4068
August 5, 2012
Hamilton physics concentrators Nick Sylvester ’13, Jill Hallak ’13, Kerkira Stockton ’14 and Brandon Wilson ’14 have spent the summer conducting research for the aCORN collaborative, a project being carried out by five universities and colleges and the National Institute of Standards and Technology (NIST). The goal of aCORN is to conclusively determine the relationship between the angles involved in neutron decay, called “little a,” which is an essential variable in the Standard Model of Electroweak Interactions.
This Standard Model is the basis for many modern day physics experiments and theories, and little a’s currently agreed upon value is only accurate to five percent, leaving too much room for error in a field as precise as molecular physics. The students are working under the direction of Professor of Physics Gordon Jones and Associate Professor of Physics Brian Collett to create a number of components necessary to enable the aCORN experimental apparatus to verify “little a” to an accuracy of one percent.
Sylvester and Wilson are working together to develop a system to precisely align the electric field within the aCORN experimental apparatus. Their apparatus consists of an electron-firing hot filament, similar to the filament found in an incandescent light bulb, which is suspended in a vacuum tube. The filament creates a stream of electrons which flow in conjunction with the electric field generated by the larger aCORN experimental apparatus, much like the way air flows around objects in a wind tunnel. The electron beam is then illuminated with an electron-exciting device called a scintillator, which in turn allows the electric field to be aligned with aCORN’s main cylinder. Once the main cylinder and electric field are calibrated by Sylvester and Wilson’s filament, other detection devices will be used to analyze electrons fired off during aCORN’s main experimental process of neutron event decay.
The electron detectors which analyze the neutron event decay must also be calibrated in order to reach an accurate value for “little a.” Nineteen photomultiplier tubes (PMTs) detect the electrons illuminated by the scintillator, and because these PMTs are triggered by light, they can be calibrated with a highly precise pulsing LED. Hallak created a stable LED pulse system to give off a known amount of light energy at a precise rate. Scientists can calibrate the 19 PMTs by comparing their readings on light energy from the pulsing LED with the known light energy produced by Hallak’s system.
Precision is so necessary for the successful completion of aCORN that Stockton’s sole task was to write a program to analyze calibration data from aCORN’s electron sensors. To do this, she studied the way in which electrons from a known radioactive source struck electron detectors within the aCORN experimental apparatus and recorded her findings. Stockton also visited the NIST Center for Neutron Research outside Washington, D.C., with Professor Jones in order to deliver sensitive and fragile parts and to see the aCORN project’s main experimental apparatus. Stockton was impressed by the sheer size of the NIST Center, which resembles an air hangar spanning multiple football fields. She said it was rewarding to see the multistory aCORN experimental apparatus in person, knowing that she and her fellow researchers helped to make the project possible.
As some of the only undergraduates working on the large scale aCORN collaborative, the students are excited that their work has the potential to conclude or alter one of the key theoretical underpinnings of physics.
Sylvester is a graduate of Little Falls High School (N.Y.), Hallak graduated from New Hartford High School (N.Y.), Stockton is a graduate of Holland-Patent Central High School and Wilson graduated from The Derryfield School (N.H.)